As I’ve promised in earlier posts, I’m archiving the Duelund-Westminster External Crossover article here at Jeff’s Place so you can find everything in one place for reference purposes (Part 1 – Intro, Part 2 – Breadboarding, Part 3 – Final Design).
The full version of the article was just published in Issue 70 of Positive Feedback Online here so be sure to check it out if you haven’t already.
Here is the next installment of the Duelund-Westminster External Crossover Project, Part 4, describing rewiring the Westminster Royal SEs to get the most out of the Duelund-WRSE external crossovers. Enjoy!
Continued from Part 3:
Rewiring the Westminster Royal SE Loudspeakers
For rewiring the Westminster Royal SE loudspeakers to accept the Duelund CAST external crossovers, Mark Coles was a major source of inspiration on how to best preserve the signal quality coming from the exotic Duelund CAST external crossovers to the WRSEs’ Dual Concentric drivers. To that end Mark suggested eliminating the WRSEs’ internal wiring connectors, the driver connecting plugs, and the binding posts, which all degrade the audio signal to an extant.
At first Mark had recommended that I use the same Neotech wire for the internal wiring of the WRSEs that I had used for the Duelund CAST external crossovers, but after considering the enormous performance improvement I realized with my WRSEs from his Sablon Audio Panatela component speaker cables (which I reviewed in Issue 63 of Positive Feedback Online), Mark suggested we instead use a continuous run of Panatela cables from the Dual Concentric™ drivers to the external Duelund CAST crossovers to see if we could realize a similar performance improvement from using the Panatelas as internal wiring.
Let me say that Mark’s idea of running a continuous set of Panatela component speaker cables from the drivers to the crossovers really appealed to me, and it turned out to be a complete success. While the primary focus of this article is upon the remarkable performance improvement that can be realized by using the Duelund CAST components in the external crossovers for the WRSEs, I want to emphasize that to fully benefit from the Duelund CASTs’ lofty performance potential you’ll want to use the absolute best internal wiring possible, and for my Westminster Royal SE loudspeakers that’s the Panatela speaker cables that Mark has tailored to perfection to match their performance needs.
To get an idea of the sort of performance you can expect by using the Panatela component cabling in the Westminster Royals SEs, I recommend that you go back and read the Panatela review in Issue 63 of Positive Feedback Online where I covered it in detail. Here is a snippet about the Panatela’s performance from that review:
“The Panatela had a rich, luxurious, slightly warm & dark presentation, which at the same time was extremely transparent and high resolution, which I find to be a rather amazing set of qualities, as usually you can have one or the other but not both. This ‘darkly detailed’ style of presentation is my personal audio Holy Grail, because it not only portrays a musical performance as emotionally engaging, but also as spectacular sonically, which provided an unbeatable combination that left me in an almost constant state of musical satisfaction and amazement.
The Panatela speaker cables portrayed timbral characteristics like textures, colors, and tones & overtones superbly, and in my experience the Panatela is in a class by itself in this regard. The string tone and color in Swan Lake was so naturally & compellingly portrayed that it left me in a state of awe as to its beauty and ability to stimulate an emotive response. The same with Getz/Gilberto, where instrumental timbres (piano, guitar, sax, drums and bass) and Astrud’s & Joao’s vocals were so beautifully tangible and present that it was intoxicating.
One of the strengths of the Panatela is being able to unravel complex music, like classical music, and present it in its full sophisticated glory. In this regard I think the Panatela speaker cables have no rival. Listen to any one of the Ansermet recordings and I suspect you’ll be picking your jaw up off the floor even as I did. This level of musicality combined with this level of sonic sophistication is unrivaled in my experience.”
I was completely blown away by the performance improvement the Panatelas brought to my Westminsters during the review, and using them as internal wiring for the Westminsters yielded similar results times two. Using the Panatela component speaker cables as the internal wiring for the WRSEs was a truly exciting development in the project, and I’d like to thank Mark Coles for suggesting it and providing a set of Panatela component cables to use for the project.
As we get ready to move on, let me remind you what goes into producing a set of Panatelas. Mark custom makes every set of Panatela cables, and builds them up from the bare wire. Mark meticulously voices the Panatela cables using a variety of different conductors and natural dielectrics. As I mentioned in the review, Mark contacted Dr. Paul Mills at Tannoy and got his advice about optimizing the high-frequency Panatela cable run to match the Tannoys Dual Concentric™ high-frequency driver characteristics. Mark doesn’t use solder joints that degrade the sound, he uses great connectors, and he meticulously tweaks the design with cryo treatments, anti-oxidants, contact paste and the like. To top it off Mark pre-conditions all of his Panatela cables with an Audiodharma Cable Cooker so there’s no break-in required.
Mark’s approach to making the Panatela cables utilizes the same sort of dedication to perfection as Frederik & Magnus do with their Duelund CAST components, and due to my aforementioned experience I felt confident that Mark’s Panatelas would bring out the very best in the exotic Duelund CAST components. To say I was very excited about the opportunity to use the Panatela component speaker cables as the internal wiring of the WRSEs would be a massive understatement!
The Panatelas I used for the internal WRSE wiring part of the Duelund-WRSE Project were the very pair of 8-foot Panatela speaker cables I reviewed for Positive Feedback Online back in Issue 63, which Mark Coles repurposed for use as internal wiring by reterminating one end of the Panatela speaker cables to make them suitable to connect directly WRSE’s Dual Concentric™ drivers.
If you decide you want to use Panatelas as internal wiring in your own Duelund-WRSE external crossover project – and I would recommend that – Mark will make you a set of Panatela cables as a custom order to meet your specific needs. Mark told me that the cost would be similar to that of the Panatela speaker cables as they are “the same underlying product with different terminations”. You should contact Mark directly for accurate price quotes on the best length of Panatelas for your project.
To give you an idea of what you’re looking at price-wise to duplicate what I did for this project, the 8-foot pair of Panatela speaker cables used from the low-frequency section of the Dual Concentric™ drivers to the low-frequency section of the external Duelund crossovers retails for $1750 USD. The pair of 8-foot Panatela tweeter cables going from the high-frequency section of the Dual Concentric™ drivers to the high-frequency section of the Duelund external crossovers retails for $1250 USD, and Mark also made me a set of dedicated ground leads to go from the ground on the Dual Concentric™ drivers to the ground on my restored vintage McIntosh MC240/MC30s, which retails for $375 USD. Total Panatela internal wiring cost comes to $3375 USD for an 8-foot set.
I used an 8-feet length of Panatela component cables to provide flexibility for reviewing, so that I could easily move the Duelund CAST external crossovers around to accommodate various electronics during reviews, and also so I could keep them visible during photo shoots. If you have a fixed system you can get by with shorter lengths of cable.
For example, Frank Rogers, a fellow Westminster Royale SE enthusiast who has also done the Duelund-WRSE project for his loudspeakers, told me he successfully used a 5-foot set of Panatelas and that length worked great. Frank also told me he thought he might have got by with a 4-foot set had he placed his crossovers directly behind the loudspeakers.
If you decide you want to do a project like this, I thought it would be handy for you to see every step in the process, so lets go through what I did in detail to rewire my Westminster Royal SEs.
The first step is to open up the big Westminsters by removing the back panel screws with a # 2 Philips screwdriver. After taking out the screws and setting them aside I lifted out the back panel and set it down against the cabinet.
Caution: My back panel came out easy, but Tannoy says the back panel is often a tight fit and warns that owners should not try to pry it out or you could damage the cabinet. Rather, Tannoy says to instead go around the outside of the panel while “thumping it firmly with your fist” until it starts to loosen up and move, then you can lift it out. Good advice to follow to protect your precious WRSEs.
Closer view …
Closer view still …
The next step is to remove the WRSEs’ internal wires from the speaker binding posts mounted in the terminal panel.
The internal wires are held to the binding posts with 8mm bolts, so I first loosened the bolts with a 8mm wrench, and then removed the 8mm bolts with a socket to speed the job.
Once the bolts and internal wires were removed, I then removed the nuts holding the binding posts in place, and then removed the binding posts from the terminal panel, allowing me to set the back panel aside to give myself more room to work on the WRSEs internals.
When the binding posts have been removed from the terminal panel the mounting holes are just the right size to thread the Panatela cables through when the time comes!
Hint: Before you start unplugging the wiring from the drivers and low-frequency crossovers, be sure to label everything just in case! I wrote directly on the wood inside my Westminster Royal SEs’ cabinets with a Sharpie® to make it clear what went where for future reference.
Label the low-frequency crossover according to the wiring color code conventions!
Next I labeled the harness color codes on the inside of the cabinet, as well as the position of the tweeter wires and grounds.
Next I unplugged the drive unit wiring harness male connector from the female connector. It just pulls straight out.
The color-coding scheme Tannoy uses for the internal wiring follows this convention:
Brown: LF +ve
Blue: LF –ve
Yellow: HF +ve
Green: HF –ve (this wire is black from the female connector to the driver)
Next unplug the yellow/green ground wire.
Then unplug the four wires from the low frequency crossover.
Next I pulled the wires down through their routing holes to get them out of the way for the next steps.
I pulled the wires down through the second routing hole too and let the wire harness rest on the floor. Next I removed the screws that hold the internal plywood structure that seals the bass horn in place with a # 2 Phillips screwdriver. There’s two screws as seen in the photo below and …
… then I removed the 5 screws from around the driver of the internal plywood structure that seals the bass horn.
Next I lifted out the internal structure to expose the driver, and then set the inner structure aside.
I’ll connect the internal Panatela wiring direct to the drivers, and then direct to the outputs of the crossover, so I will not be using the stock Tannoy male/female plug connectors, which are said to degrade the sound quality. That way I have only the Panatela wiring in the signal path between the crossovers’ outputs and the driver connections with no intervening connectors.
There are two extremely fine wires that go from the female plug connector to the tweeter. There’s a little blue tag on the tweeter endcap, and I suggest that if you’re doing a direct connection of wire to the tweeter driver like I am, that you label it with the wire connection’s color codes. Mine had a yellow wire connected on the right, and a black wire connected on the left. The wires are soldered in place, so I snipped them off to get them out of the way.
Caution: If you choose to desolder / solder the connections for the high frequency wires you need to be extremely quick and cautious about it. The two tabs that the yellow & black high frequency wires are attached / soldered to are mounted on a driver endcap that is made of plastic (the one in the photo with the 4 screws holding it in place). If you heat the tabs too long with a soldering iron you’ll melt the plastic. This could wreck your day as the endcap has micro-electrical connections deposited in it in high-tech fashion, and it is part of the tweeter assembly. If you melt it you will likely destroy it. That means you’ll have to order new ones. They’re probably expensive. Be careful!
Then I removed the female plug connector from drivers frame. The connector has two little plastic prongs that you have to push in to get clearance so you can push it out (I used a small screwdriver).
Then I pulled the fine tweeter wires through to free them from the opening.
I then pushed the female connector out using the handle end of a wooden spoon (use something non-magnetic or it’ll be drawn into the powerful magnet of the driver, which is a no-no). Note the color-coding and label the wires. Mine had blue (LF -) as the left wire and brown (LF +) as the right wire.
Now it was time to go to work on the high frequency crossover located in the front of the Westminster’s cabinet. On the front of the cabinet I removed the 2 brass adjustment screws and set them aside.
I then removed the four 2.5mm hex screws holding the brass trim place in place, pulled out the plastic cups, and then removed the trim plate and set it aside.
I then removed the 6 wood screws holding the wooden panel and withdrew it to reveal the HF crossover assembly.
I marked the yellow (soldered) and green (press fit) positions on the circuit board by the autoformer with a permanent marker in case I wanted to re-install the stock cable set, so I could remember what went where. I taped the green and yellow wires together and labeled them “bottom by the autotransformer”.
I unplugged the green wire from the circuit board, and then I de-soldered the yellow wire. I then labeled the green (soldered) and yellow (press fit) positions on the top of the circuit board with a permanent marker, and then de-soldered the green wire and unplugged the yellow wire. I taped the two wires together and labeled them “top of the circuit board”.
I then pulled the internal wiring harness out through the back of the speaker and placed it in a plastic bag labeled “WRSE internal wire & binding posts Left” and set it aside in case I need it later.
I reinstalled the now disconnected HF crossover back into the cabinet, put back on the trim plate, inserted the plastic cups, and put the selector pins back in place. I then went around back and sealed the wiring harness hole in the back of the horn with Blu-Tack.
I labeled the wires with the Peavey color-coded microphone tape so I wouldn’t get them mixed up.
I then pulled the low-frequency wires through the connector hole and then sealed the hole with Blu-Tack. Then I set the internal plywood structure that seals the bass horn and the driver back in place.
The Panatela low & high-frequency cables sets are shrink wrapped on the crossover end, so I reverse routed them from the external Duelund crossover through the binding post holes in the Westminster Royal SEs.
Through the binding post holes in the Westminster Royal SEs …
… and up through the cabinet routing channels.
As a refresher, the color-coding scheme Tannoy uses for the internal wiring follows this convention:
Brown is LF +ve (this is the red leg of the Panatela low frequency cable), blue is LF –ve (this is the white leg of the Panatela low frequency cable), yellow is HF +ve (this is the red leg of the Panatela high-frequency cable), green is HF –ve (this is the white leg of the Panatela high-frequency cable), and green/yellow is Earth.
I connected the low frequency cables to the driver leads with WBT 8 AWG crimp sleeves.
The blue LF –ve lead from the driver is crimped to the white leg of the Panatela low frequency cable.
Then the brown LF +ve lead from the driver is connected to the red leg of the Panatela low frequency cable …
Next I connected the Panatela ground using a dab of WBT silver solder …
Next I soldered the Panatela HF leads with a dab of WBT silver solder …
After I got the Panatela cables attached to the driver, I tightened down the internal plywood structure that seals the bass horn and the driver, then secured the cables with a little Blu-Tack, and put the back panel back in place on the WRSE.
My initial fears about my ability to upgrade my Tannoy Westminster Royal Special Edition loudspeakers’ crossovers with the premium Duelund Coherent Audio CAST components turned out to be unfounded, and it turned out to be much easier and more straightforward than I had presumed.
I couldn’t be more delighted with the outcome of the Duelund-Westminster external crossover project – the Duelund CAST crossovers turned out spectacularly good!
Next up will be Part 5 with a review of the results.
Thanks for stopping by!
On Sunday afternoon Ron (center) and Leo (left) joined me for a fine day of hi-fi fun and games, and as usual we had a ball! (Sorry for the blurry photo. Note to self: remember to use the correct camera setting next time!)
After a lunch of a combo pizza and a few glasses of some mighty fine vino, we put together a set of binding post bypass style of speaker cable adapters for Leo’s vintage McIntosh MC30 mono amps so he could use modern speaker cable connectors on his amps.
For those of you not familiar with the vintage amplifiers, they use terminal blocks with screws to connect speaker cables, from back in the days when people only used a bare wire end to connect loudspeakers, and modern connectors are just too big too fit into their tight confines.
Below, that’s the terminal blocks on my vintage MC240 with a binding post bypass adapter in place, securing a pair of Panatela speaker cables, so you can see how they work. If you look close you can see how the spade connectors of the Panatela speaker cables are clamped to the bare end of Neotech wire, with the other end being held in place by the screw on the terminal block. These adapters work great!
Next time we’re going to build a set for George’s MC30 mono amps, and a pair for Leo’s vintage Marantz 8!
We also had a great discussion about our favorite 6L6GC tubes. There’s a ton of great new stock 6L6GC tubes being made right now, so if your amps run 6L6GCs this is a good time to be alive! Arguably the prettiest of the bunch is the Tung-Sol 6L6G (which you can use in a circuit designed for 6L6GCs, unlike the NOS 6L6Gs which can’t handle it), and they’re one of the best sounding of the currently available 6L6 family tubes. That’s a quad of them with their sexy ST bottle shapes in my MC240 below.
On the vintage front the RCA 6L6GC black plates and the Philips 7581A are easy favorites, and I’d say it is about a draw between those musical titans. They sound different, but they are both great, and on some music I preferred the RCAs, and on other music the Philips 7581A.
That’s the RCA 6L6GC black plates below in my MC240. Expect to pay a small fortune for the RCAs if you are lucky enough to find them. You could probably buy 4 quads of the Tung Sol reissue 6L6Gs for what a quad of the RCAs would sell for. They’re good, but are they that good?
Here’s a photo (below) of the Philips 7581A in the MC240. The Philips are really great tubes and come in at less than half the price of RCAs. They are getting hard to find too.
I had a digital front end set up for my upcoming review of the Mhdt Labs Stockholm V2 vacuum tube USB DAC that included an iMac with about 900 or so CDs loaded on it, and the Channel D Pure Music software that integrates nicely with iTunes (I’ll have more to say about Pure Music in another post – great software!).
In the review I’ll be comparing the Stockholm V2 to the Mhdt Labs vacuum tube Havana USB DAC, and to my vinyl front end, the final arbiter of how far digital has come!
Leo brought over his new McIntosh C2300 vacuum tube preamplifier (top) and we listened to it compared to my vintage McIntosh MX110Z (below).
The C2300 is one beautiful looking preamplifier with its glass front, glowing green McIntosh logo, and blue meters!
Comparing the new C2300 to the vintage MX110Z was about what you would expect, with the C2300 being more transparent and resolving, and the MX110Z sounding more … well vintage … softer, warmer, and less transparent.
The C2300 has more features than you can imagine, and a remote control for all of them!
I really like the fact that the C2300 – like the MX110Z – has tone controls. Tone controls are such a good idea for being able to fine tune a system to a room, a new component, or to different records, and the great designers of the Golden Age of Audio all knew that sort of adjustably was important (ergo the classic Marantz, McIntosh, et al, had tone controls). I hope tone controls come back into fashion, they’re awesome!
Ok, the MX110Z does win on one feature that it has that the C2300 doesn’t, that fantastic sounding vacuum tube tuner that pulls in my local National Public Radio station with ease! I have really been getting into listening to FM lately, and it sounds remarkably good.
With a few judicious tweaks to the tone controls we could make the C2300 sound quite a lot like the MX110Z. There is definitely a McIntosh ‘house’ sound that has crossed the five decades since the MX110Z was made. That’s impressive really, as the over 50 year older MX110Z and shiny new C2300 are both easily identifiable as McIntosh’s, and that’s a good thing! Kudos to McIntosh for honoring tradition!
A complete change of subject: I just heard from Frederik Carøe in Denmark – the founder of Duelund Coherent Audio – that he has started building a pair of 6.8 uF SILVER Duelund CAST paper-in-oil capacitors for me to try in the C1 position of the Duelund-WRSE external high-frequency crossovers! That is really exciting news!
In the photo above you can see the Duelund 6.8 uF CAST copper capacitor (C1) in the left lower corner of the crossover. When the 6.8uF CAST silver capacitors arrive from Frederik all I’ll have to do is loosen the binding post clamps to slip out the leads, loosen the setscrew lugs to slip out the other leads, and then slide the new 6.8uF silver CAST capacitors in place and tighten everything back up – easy as that!
I’ll have a lot more to say as the story of the Duelund 6.8 uF CAST silver capacitors develops in both blog posts along the way, as well as a full review at Positive Feedback Online in due time – stay tuned!
I hope you enjoyed Sunday afternoon with us at Jeff’s Place, and I hope you’ll come back again soon!
From our homes to yours, may the music warm your heart!
As I promised in earlier posts , I’m archiving the Duelund-Westminster External Crossover article here at Jeff’s Place for reference purposes (Part 1, Part 2). The full version of the article was just published in Issue 70 of Positive Feedback Online here so be sure to check it out if you haven’t already.
Here is the next installment of the Duelund-Westminster External Crossover Project, Part 3, describing building the final version of the Duelund CAST external crossovers for the Westminster Royal SE loudspeakers. Enjoy!
Continued from Part 2.
The Final Version of the Duelund CAST External Crossovers
Once the breadboarding of the Duelund CAST external crossovers was complete, I began building the final versions according to the following steps:
- Build the vibrational energy dissipation platforms to mount the Duelund CAST crossovers on.
- Install the Duelund CAST components and Tannoy autotransformers from the breadboards onto the vibrational energy dissipation platforms.
- Use straight tongue copper setscrew lugs from McMaster-Carr for mechanical connections of the wires on the crossover boards.
- Use 20-gauge Neotech solid-core UP-OCC silver wire with a Teflon jacket to wire the high-frequency section of the crossover.
- Use 14-gauge Neotech solid-core UP-OCC copper wire with a Teflon jacket to wire the low-frequency section of the crossover.
The inspiration for the final chassis design for the Duelund CAST external crossovers came from the creatively brilliant Mr. Ken Ishiguro of Acoustic Revive fame, whose innovative applications of physics, materials science, and audio engineering principles to his high-performance Acoustic Revive audio products never fail to amaze me in their cleverness and effectiveness in enhancing the performance of my audio system. I chose to base the chassis for the Duelund CAST crossovers on concepts related to the Acoustic Revive RST-38 Quartz Under-Boards I reviewed in Chapter 7 of The Acoustic Revive Chronicles, which are my favorite audio stands/platforms.
As I described them in the review, the Acoustic Revive RST-38 Under-Boards are stands, or more correctly, vibrational energy dissipation platforms, to place your audio equipment upon. The RST-38 Under-Boards are designed to quickly route vibrational energy away from audio components and dissipate it. They feature a composite wood chassis that is filled with quartz granules, upon which a birch plywood top plate is placed to sit components upon. The idea behind using quartz fill in the chassis of the RST-38 Under-Boards is to harness the piezoelectric properties of quartz to dissipate vibrational energy, thereby improving the sound of Hi-Fi electronics placed upon them. Acoustic Revive says that vibrational energy from a component travels through the top board to the quartz filling where it is dissipated, and conversely that vibrational energy coming up through the floor or equipment into the Under-Board’s chassis is also transferred to the quartz and dissipated.
I would have built the Duelund crossovers directly onto the RST-38s if they were big enough, but they weren’t. The massive size of the Duelund components means that I needed the bases for the crossovers to be 20.5-inches by 18.5-inches, and the RST-38′s 17-inches by 13-inches was just too small to accommodate the king-sized Duelund CAST components.
My friend and colleague, Dave (Dave Biancosino, Answers in Art), who is also an expert woodworker, helped me develop and build the final chassis for the outboard Duelund CAST crossovers. After we had the basic design planned out we went into Dave’s woodworking shop to get the chassis started.
Instead of the composite wood chassis and birch plywood top plate of the RST-38, for the Duelund crossovers I wanted to try a tonewood approach (tonewoods are woods used to construct musical instruments, which I thought was quite fitting in this case): a maple frame with a birch ply base, and a solid walnut top plate.
In the above photo you can see the Duelund breadboard crossover in the foreground, and the walnut top plates in the background.
The first thing Dave did was to make the terminal blocks that the binding posts would be mounted to (below), which would then be attached to the walnut top plates.
Then we got started on building the maple frames to fit the dimensions of the 18.5-inches by 20.5-inches walnut top plates, which gave us the needed room for mounting the king-sized Duelund components.
Dave thought it would look nice to use a black ink stain on the maple frames to give the isolation platforms a complimentary finish to that of the Duelund CAST components, which I thought was a particularly cool idea.
After Dave did the glue-up and sanding of the frames, he used an India ink dye to stain the wood. Dave said, “Although any stain or dye would work, to get a jet black finish, India ink or a black acrylic would be needed. The acrylic would not show the grain as well, however.”
After Dave did the dyeing with the India ink, he did a light sanding because the ink is water based and will raise the grain a bit. Dave chose a clear gloss wipe-on polyurethane finish and put 6 coats on the frame. Dave lightly sanded between each coat with progressively finer paper each time to give a beautifully smooth finish.
Dave told me, “Although the bottom will not be seen, it’s important to at least put a coat or two of finish on it as well to eliminate the possibility of warping. You want moisture content of the wood to be the same throughout the wood.”
In the foreground below is the unfinished maple frame mounted on the plywood base, with the stained (but without the final finish steps) maple frame on the plywood base in the background.
While Dave was completing the finish work on the maple bases, I installed the walnut binding post blocks onto the walnut top plates, and then got busy mounting the Duelund CAST components.
Since the layout was optimized on the breadboards, all I really had to do was transfer over the Duelund CAST components to the walnut top plates.
To mount the Duelund CAST components to the walnut top plates, Pete recommended that we use straight tongue copper set screw lugs, 14-8 AWG, #10 stud, from McMaster-Carr, part number 6923K61 (I ended up using 21 of them in each crossover to complete all the wire-on-wire connections, for a total of 42, at $1.83/each USD).
The wire leads from the Duelund CAST components were inserted directly into the setscrew lugs and clamped together to give the best possible connection.
For the wiring within the crossover itself, Mark Coles recommended that I use 20 gauge Neotech solid-core UP-OCC silver wire with a Teflon jacket for the high-frequency section of the crossover (I used approximately 12 feet – 6 feet per crossover – at $21.34 USD per foot), and 14 gauge Neotech solid-core UP-OCC copper wire with a Teflon jacket for the low-frequency section of the crossover (I used slightly less than 16 feet – 8 feet per crossover – at $5.95 USD per foot).
You can see the blue Neotech silver wire used in the adjustable high-frequency portion of the Duelund CAST crossover (above), and the red Neotech copper wire used in the low-frequency crossover in the photo below, now with all of the Duelund CAST components installed on the walnut top plate.
When I got the finished frames from Dave I placed the quartz granules in the bases and placed the walnut top plates into the bases, and voilà – the Duelund-Westminster CAST external crossovers were born!
A breaking news note about isolation platforms: While it will be too late coming for inclusion as part of this article, the nice people at Soundcoat Company, who have been providing specialized noise control solutions to aerospace, medical, and industrial applications since 1963, have been working with me to integrate cutting edge vibration-control technologies into the Duelund-WRSE Project isolation stands in a number of clever and easily applied ways, both by providing vibration reduction technologies for the entire stand, as well as for each of the Duelund components mounted upon them. Additionally, the Soundcoat Company will provide additional vibration control technologies that can be applied to individual components like turntables, phono equalizers, USB DACs, preamplifiers, amplifiers, and other audio applications. I will follow up in a future article to let you know the outcomes of this collaboration with Soundcoat Company on applying their vibration control technologies to audio applications. It’s an exciting topic!
A Walk-Through of the Duelund High-Frequency Crossover
Let’s take a ‘walk-through’ of the final Duelund-WRSE CAST crossover, starting with the high-frequency section, so you can see in detail how everything goes together in the final design.
Below is my high-frequency crossover schematic for a refresher before we start our journey, so hopefully it will help make the photos and discussion a little easier to follow. I’ll start at the left side of the schematic where the signal comes in from the amplifier, and then walk my way across towards the right, where the signal goes out to the loudspeaker.
In the photo below you can see the Sablon Audio Panatela speaker cables coming in from the amplifier attached to the HF+ IN (red) and the HF- IN (white) binding posts of the Duelund CAST high-frequency crossover. (The pair of binding posts on the right side go to the Duelund CAST low-frequency crossover, which I’ll describe in a moment.)
If you look closely at the photo below you can see the details of how the binding post bypass method works for connecting the Panatela speaker cables to the Duelund CAST crossover’s internal wiring: The lead from the Duelund 6.8 uF CAST capacitor (C1) inserts into the left binding post’s wire passage. The silver spade connector from the positive (red) Panatela cable coming in from the amplifier slips over the binding post shaft directly in front of the wire lead from the Duelund capacitor. When the binding post cap nut is tightened down it clamps the Panatela’s spade and the Duelund CAST capacitor lead wire tightly together to make the electrical connection, thus avoiding a signal degrading solder connection, and making for the most direct connection of the speaker cables spade connector possible to the crossover’s internal wiring.
On the right binding post a 20-gauge Neotech silver wire (blue) is inserted into the right binding post’s wire passage. The silver spade connector from the negative (white) Panatela speaker cable coming in from the amplifier slips over the binding post shaft directly in front of the Neotech silver wire lead, and when the binding post cap nut is tightened down it clamps the Panatela’s spade and the Neotech silver wire tightly together. As passing the signal through binding posts as part of a circuit degrades the signal somewhat, the binding post bypass method is a truly nice way to get the binding posts out of the circuit and at the same time avoiding an equally signal degrading solder connection!
Thanks again to Mark Coles for the idea of using the binding post bypass method of connecting speaker cables to the crossover’s internal wiring, it’s truly an elegant way to preserve the fidelity of the audio signal passing through the circuit as much as possible.
In the photo below you can see the entry lead (with the yellow tape marker) going from the HF+ IN binding post into the C1 Duelund 6.8 uF CAST capacitor, and from the HF- IN binding post you can see the 20-gauge Neotech silver wire (blue wire with green tape marker) going off into the distance to connect at the setscrew lug that connects to the black wire on the autotransformer, the R1 Duelund 47R/5W Carbon/Silver CAST resistor, and the C3 Duelund 3.3 uF CAST capacitor.
The copper setscrew lugs serve the same sort of clamping function as the binding posts do in the binding post bypass method, where the setscrew simply clamps the two wires tightly together in the lug for a signal-preserving solder-free connection. To maintain as much signal fidelity as possible, there are absolutely no solder joints used in the Duelund CAST external crossovers. Only the leads from the Duelund CAST components, connected where necessary with the shortest possible lengths of the ultra-quality Neotech hookup wire, make up all the wiring used in the circuits, and all connections are made with the setscrew lugs.
Thanks to Pete Riggle for suggesting the idea of using the copper setscrew lugs to connect the Duelund components’ leads to the crossovers’ internal Neotech wiring, as it’s truly a superb way to preserve the fidelity of the audio signal passing through the circuit as much as possible, with the added bonus of being able to quickly change out a component should that be desired.
In the photo above you can see the lead from the Duelund 6.8 uF CAST capacitor (C1) inserting into the red-tape side -1.5 dB treble energy level setscrew lug where it connects to the green lead of the autotransformer (the 3rd red-side setscrew lug up from the bottom of the photo).
The photo above also shows a close-up of the aforementioned 20-gauge Neotech silver wire (blue) coming in from the negative binding post and inserting into the bottom red-tape side setscrew lug that connects the black wire on the autotransformer, the R1 Duelund 47R/5W Carbon/Silver CAST resistor, and the C3 Duelund 3.3 uF CAST capacitor.
You can see the R1 Duelund 47R/5W Carbon/Silver CAST resistor positioned between the C1 Duelund 6.8 uF CAST capacitor and the autotransformer. Note that R1 Duelund 47R/5W Carbon/Silver CAST resistor also inserts into the red-side +3 dB treble energy level setscrew lug (the top setscrew lug on the red-tape side in the photo below).
As with the stock internal Tannoy WRSE crossover, the Duelund CAST external crossover allows the treble energy level of the tweeter to be adjusted over a range of -3 dB to +3 dB by selecting different taps on the autotransformer that increase or decrease the tweeter energy level in 1.5 dB steps from the crossover point.
In the Duelund CAST crossover this is accomplished by moving a jumper wire in the crossover to connect to the appropriate autotransformer tap (from top to bottom in the photo below: the red tap is +3 dB, the orange tap is +1.5 dB, the yellow tap is +0 dB, the green tap -1.5 dB, and the blue tap -3 dB).
In the photo below you can see a length of 20-gauge Neotech silver wire (blue with a red tape marker) that is inserted into the +0 dB treble energy level setscrew lug (on the ‘red-side’) that connects it to the yellow tap (+0 dB) from the autotransformer. This is the jumper wire that can be moved between the different red-side setscrew lugs corresponding to the autotransformer taps that adjust the treble energy level of the tweeter. In the photo, the Neotech jumper wire is inserted into the +0 dB treble energy level setscrew lug, which means that there is zero alteration of tweeter’s treble energy level.
As we move to the right in the photo (and schematic), the other end of Neotech movable jumper wire is connected to the R2 Duelund 10R/10W Carbon/Silver CAST resistor (which is the horizontal resistor in the middle of the photo) via a setscrew lug that you can see just to the left of the C2 2.2 uF Duelund CAST capacitor (the capacitor in the upper right of the photo). A length of Neotech silver wire also goes from this setscrew lug to the +2 dB treble roll-off control that is at the top of the green tape strip in the photo.
A length of 20-gauge Neotech silver wire (blue) goes from the -3 dB treble energy level setscrew lug (red side) to the -6 dB treble roll-off level setscrew lug (green side), and then all the way to the HF+ OUT binding post that goes out to the loudspeaker, where it is clamped to the silver spade of the positive lead (red) of the internal WRSE Panatela wire (lower right-hand corner of the photo).
The treble roll-off circuitry functions as a variable low pass filter, which I’ll explain in more detail in a moment, but first let me describe what it does visually by using the diagrams from the front panel of the WRSE treble controls, which I think will give you more of an intuitive feel for what the circuitry does.
If you look at the photo below, the diagram underneath the treble energy level control (the left control) shows that when the different transformer taps are selected the treble energy level is changed in steps over the range of +3 dB to -3 dB at the crossover point, but the change in dB is linear in response with increasing frequency from the crossover point.
In the diagram underneath the treble roll-off level control, you can see that the change in dB response is non-linear with increasing frequency. The treble roll-off control provides an increasingly greater dB change in treble response as a function of increasing frequency in a smooth curve (i.e. dB response ‘rolls-off’ with increasing frequency).
In discussing the treble roll-off control with Paul Mills, he told me that its inclusion in the WRSE’s circuit is largely historical in nature, as its original purpose was to tailor the high-frequency response to help reduce the hiss on 78 rpm records. Paul told me that he had considered removing the treble roll-off control from the circuit as it doesn’t really serve a useful purpose for modern recordings, but a very enthusiastic core group of Westminster owners who still listen to 78s wanted him to retain it, so he did. Paul advises those not listening to 78s on their Westminsters to ignore the treble roll-off control!
Ok, now let’s continue our walk across the high-frequency crossover. Take a look at the row of setscrew lugs on the green tape in the photo below – these are the treble roll-off level controls for the Duelund CAST crossover. If you have a lot of 78s to listen to you might want to change the treble roll off setting from the normal +0 dB setting to +2 dB, -2 dB, -4 dB, or -6 dB to best flatter your particular 78 rpm record.
To change the treble roll-off to best complement the 78 rpm record you want to listen to, you would move the lead of the C2 2.2 uF Duelund CAST capacitor (marked with the red tape in the photo) to the setscrew lug with the desired level of roll-off. (It’s the capacitor in upper right of the photo above, with a close-up below.)
+2 dB setting: If you insert the C2 2.2 uF Duelund CAST capacitor lead into the +2 dB setscrew lug, it places the R2 Duelund 10R/10W Carbon/Silver CAST resistor and the R3 Duelund 22R/10W Carbon/Silver CAST resistor in parallel with the C2 2.2 uF Duelund CAST capacitor to give +2 dB of roll-off on its way to HF- OUT.
+0 dB setting: If you insert the C2 2.2 uF Duelund CAST capacitor lead into the +0 dB setscrew lug, it places the R2 Duelund 10R/10W Carbon/Silver CAST resistor in series with the C2 2.2 uF Duelund CAST capacitor, and the R3 Duelund 22R/10W Carbon/Silver CAST resistor in parallel with the C2 2.2 uF Duelund CAST capacitor, to give +2 dB of roll-off on its way to HF- OUT.
Note: In my original posting I made a mistake in describing how the circuit works to achieve the +2dB and +0dB settings. The text has now been corrected. A big ‘Thank you!’ to the very astute Carlos Margutti for pointing this out – very much appreciated!
-2 dB setting: If you insert the C2 2.2 uF Duelund CAST capacitor lead into the -2 dB setscrew lug, it drops the C2 2.2 uF Duelund CAST capacitor out of the circuit, and the HF+ IN signal from the transformer tap goes through the R2 Duelund 10R/10W Carbon/Silver CAST resistor and the R3 Duelund 22R/10W Carbon/Silver CAST resistor, to give -2 dB of roll-off on its way to HF- OUT.
-4 dB setting: If you insert the C2 2.2 uF Duelund CAST capacitor lead into the -4 dB setscrew lug, the HF+ IN signal from the transformer tap goes through the R2 Duelund 10R/10W Carbon/Silver CAST resistor and the R3 Duelund 22R/10W Carbon/Silver CAST resistor on its way to HF- OUT, and it places the C2 2.2 uF Duelund CAST capacitor and the C3 3.3 uF Duelund CAST capacitor in series across the driver terminals to act as a low pass filter, to give -4 dB of roll-off.
-6 dB setting: If you insert the C2 2.2 uF Duelund CAST capacitor lead into the -6 dB setscrew lug, the HF+ IN signal from the transformer tap goes through the R2 Duelund 10R/10W Carbon/Silver CAST resistor and the R3 Duelund 22R/10W Carbon/Silver CAST resistor on its way to HF- OUT, and it places the C2 2.2 uF Duelund CAST capacitor across the driver terminals to act as a low pass filter, to give -6 dB of roll-off.
Once the incoming signal goes through the treble roll-off level control it ends up at the HF-/HF+ OUT pair of binding posts, which connects to the Panatela internal cabling from the Westminsters using the binding post bypass technique as described earlier (below).
Ok, that’s it for the high-frequency section of the Duelund CAST external crossover, so now lets walk through the low-frequency section.
A Walk-Through of the Duelund Low-Frequency Crossover
The adjustability of the high-frequency crossover makes it more difficult to understand what is occurring in the circuit as different energy & level settings are selected, but fortunately the low-frequency crossover’s fixed design makes it relatively easy to follow.
For a refresher, above is the schematic for the low-frequency crossover. We’ll start at the left side of the schematic where the signal comes in from the amplifier and work our way across towards the right.
In the photo below you can see the pair of LF+/LF- IN binding posts on the right that the Panatela speaker cables coming from the amplifier attach to.
As with the high-frequency binding posts, the low-frequency binding posts also use the bypass method (below) to clamp the 14-gauge Neotech solid-core UP-OCC copper wire (red) used for wiring in the low-frequency crossover to the Panatela speaker cables silver spade connectors.
In the photo below a length of 14-gauge Neotech copper wire goes from the LF+ binding post to a setscrew lug that connects the leads in parallel from the C4 Duelund 200 uF Mylar CAST capacitor (at the top in the photo), the R4 Duelund 4R7/10W Carbon/Silver CAST resistor (between the capacitor & inductor), and the L1 Duelund 4 mH PIO Copper Air Core CAST inductor (at the bottom in the photo).
Below is a close-up photo of the setscrew lug that connects the length of 14-gauge Neotech copper wire from the LF+ binding post to the leads from C4, R4, and L1 in parallel.
In the photo below you can see that on the right side of C4, R4, and L1 there is a setscrew lug that connects their leads in parallel, while adding in the lead for the L2 Duelund 1 mH PIO Copper Air Core CAST inductor, which is visible in the upper right corner of the photograph.
The L2 Duelund 1 mH PIO Copper Air Core CAST inductor is positioned perpendicular to the L1 Duelund 4 mH PIO Copper Air Core CAST inductor so their magnetic fields don’t interfere with each other.
In the photo above you can also see the two Duelund 2R0/10W Carbon/Silver CAST resistors that are paralleled to give a 1R0 value in the R5 position of the circuit.
In the photo below you can see the leads of the paralleled 2R0 Duelund resistors nearest the L2 Duelund 1 mH PIO Copper Air Core CAST inductor connect at a setscrew lug that intersects a length of 14-gauge Neotech copper wire that goes all the way from the LF- IN binding post to the LF+ OUT binding post.
In the photo above you can see that the leads of the paralleled 2R0 Duelund CAST resistors furthest from the L2 Duelund 1 mH PIO Copper Air Core CAST inductor connect at a setscrew lug to the lead from the C5 20 uF Duelund CAST capacitor.
The other lead from the C5 20 uF Duelund CAST capacitor connects to the L2 Duelund 1 mH PIO Copper Air Core CAST inductor at the setscrew lug on the far right of the crossover, and a short length of 14-gauge Neotech copper wire connects it to the LF- OUT binding post (see close-up below).
The LF+/LF- OUT to the Westminster connects the 14-gauge Neotech copper wiring of the low-frequency crossover to the Panatela internal wiring using the binding post bypass method, as with the high-frequency crossover (below).
Now that we’ve completed our ‘walk-throughs’ of the final versions of the Duelund-WRSE external crossovers, let’s get started on the next major project phase, rewiring the Westminster Royals SEs with Sablon Audio Panatela speaker cables so they can get the best from the Duelund CAST external crossovers!
Ok friends, that’s it for now. Next up will be Part 4 covering the rewiring of the Westminster Royal SEs to get the most out of the Duelund-WRSE external crossovers.
Thanks for stopping by!
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