Duelund CAST copper 3.5 mH inductors and 10.5 uF capacitors for the Duelund-Corona Project.

I'm going full steam ahead on the Duelund-Corona 832A Project as well, and making great progress!

If you haven't been following along, the Duelund-Corona 832A Project is about building custom Duelund CAST copper crossovers for my beautiful vintage Altec Corona 832A loudspeakers from the late 1950s. 

Altec 832A Corona loudspeaker in a room corner.

The stock crossovers are the Altec N800Es, which are really nice, as you can attenuate the high-frequencies by up to 6dB.

That allows the listener to dial in the HF to the room, listening position, or personal tastes, which is a really handy carryover feature from Altec's professional range of loudspeakers. 

Altec N800E crossover.

Altec N800E crossovers can attenuate the HF by 6dB.

The circuit for the N800E crossovers is super simple, with only one 3.5 mH inductor and one 10.5 uF capacitor in the LF circuit, and the same for the HF circuit.

N800E crossover schematic courtesy of Great Plains Audio.

Closeup of a Duelund CAST 3.5 mH pure copper air-core inductor.

Closeup of a Duelund CAST 10.5uF pure copper capacitor.

The HF resistance network of the N800E looks rather complicated, but it can be eliminated and replaced with an L-pad or autoformer to achieve adjustable HF attenuation, as in the diagram below.

N800E crossover with L-pad replacing the resistance network.

I've been working hard on getting the breadboard versions of the Duelund CAST copper crossovers put together, and I've now completed them.

Duelund CAST copper "breadboard" crossovers.

In the photo above you can see one Duelund CAST copper 3.5 mH inductor & one Duelund CAST copper 10.5 uF capacitor at the top of the photo, which makes up the low-frequency part of the crossover circuit. 

In the bottom of the photo above you can one Duelund CAST copper 3.5 mH inductor & one Duelund CAST copper 10.5 uF capacitor, and a 16 Ohm L-pad, that makes up the high-frequency part of the circuit. 

The black (-) wire in the crossover is Duelund DCA16GA tinned-copper wire, and the red (+) wire in the crossover is vintage Western Electric WE14GA tinned-copper wire.

I ran out of DCA16GA tinned-copper wire, but using the red WE wire helped me make sure I had everything wired up correctly, so all's good. 

Altec 802D compression driver & Altec 811B HF horn.

The next step was to rewire the Corona 832A loudspeakers internally, as the wiring harnesses for the N800E crossovers are permanently attached to the crossovers, so I wanted to leave those intact. 

Altec 803A low-frequency driver - the king of Altec LF drivers!

The Coronas' cabinets are a real bugger to take apart, as Glenn of California used something like 20 screws per back panel, and there's 2 back panels to each Corona due to their triangular shape. Complete overkill on Glenn's part. Four to six screws securing each back panel would have been plenty!

Whining aside, once I got the back panels off - all four of them for the pair of Coronas - I rewired the Altec 803A low-frequency drivers & Altec 802D compression drivers with Duelund 600V DCA16GA tinned-copper wire.

The 600V DCA16GA tinned-copper wire is overkill voltage-wise for internal wiring, and sounds a little closed-in compared to the cotton wrapped DCA16GA tinned-copper wire. 

Ideally for the Coronas, internal wiring with cotton-wrapped copper or silver wire might be a better choice, so the 600V DCA16GA tinned-copper wire may be a temporary stop. 

Having said that, I thought it was interesting that the original wiring loom for the N800E crossovers was tinned-copper wire with a polymer coating of some sort, so the Duelund 600V is similar to that. I'll have to think about wire a little more for the path forward. 

After getting the Corona loudspeakers rewired internally, I installed the breadboard crossovers to give them a test run, to make sure everything was operating correctly. 

Leben CS-300F integrated amplifier.

I'm using a beautiful little Leben CS-300F integrated amplifier to power the Altecs during bedding-in of the crossovers, wiring, etc., in combination with a Sony Blu-ray player for CDs & DVDs, and an Apple TV for streaming video. 

Yazaki-san's hot-rodded Douk Audio U4.

It just occurred to me as I was writing this, that Yazaki-san's hot-rodded Douk U4 Bluetooth streaming DAC might be great in this system as well, so I'll have to get it transferred over from my office audio system and give it a try. 

Postscript: I installed Yazaki-san hot-rodded U4 into the system and have been using it for bedding-in the crossovers & wires. Not only does the U4 sound great in this system, it really is handy just to leave it running to get bedding-in time accumulated. 

The test run for the new crossovers went exceptionally well, and I am really impressed at how much more musical information is coming through compared to the stock N800E crossovers.

I found a nice setting for HF attenuation with the L-pads, and once everything was dialed-in, I was really satisfied with how musically natural all the CDs I have played sound. 

So far I've played jazz, classical, and opera albums, with each album impressing the heck out of me through these vintage Altec Corona 832A loudspeakers with the Duelund CAST copper crossovers. 

I figure about 100 hours of bedding-in time for the crossovers & wiring should be about right, which is easy to do by playing CDs, or even easier with streaming. 

So Phase One of the Duelund-Corona 832A project is complete, and now it's on to the next steps.

Luxman AS-10 transformer constant impedance attenuators.

Up next is deciding what sort of high-frequency attenuation to go with. Friend Yazaki-san is testing the Luxman AS-10 transformer constant impedance attenuators, which he seems to like quite a lot. They are not current production items though, so may be harder to find. Dave Slagle's "Speakerformers" are also a similar idea. So those two are on the horizon for consideration.

Dave Slagle's "Speakerformers".

After I get adequate bedding-in time completed, I'll then give more consideration to the crossover & loudspeakers wiring. Leave it as is? Or try something else? 

I had thought about installing the crossovers inside the Corona loudspeakers, but after considering it, I've decided external crossovers are a better way to go, so I'm thinking about options for that.

Have I mentioned I am an Altec nut? I love these vintage Altec loudspeakers!

A huge "Thank you!" Frederik at Duelund Coherent Audio for partnering with me on the Duelund-Corona 832A Project, and providing the Duelund CAST copper inductors & capacitors for the project - you're the best! 

Previous articles in the Duelund-Corona 832A series:

• A New Audio DIY Project Announcement: The Duelund-Corona 832A Project! HERE
• The Duelund-Corona 832A Project: The resistance network! HERE

To find all four-hundred and fifty-two articles mentioning Duelund Coherent Audio products in Jeff's Place articles, enter "Duelund" in the Jeff's Place search function. 

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