Tannoy CPA 12 Cabinets

No worries Dev.

 

What a day!

I finally got around to veneering the speakers today. I cut out veneer made sure it was the correct size and applied Evo-Stick to it and left it in the garden to dry and applied Evo-Stick to one of the speakers. As soon as I finished the speaker I went out to pick up the veneer and realised there had been a sudden downpour :cry:.

Spent 4-5 hours and about half a litre of white spirit to remove the Evo-Stick from speaker and veneer .



The blog of the removed EvoStick.

 

I know the pain. I have to do it on the Kensai to remove and change the leather cover. I find a good wipe with white spirit and then the back flat edge of a razor scraper helps get it off well. Looks like you did the same.

 

Yes, I used liberal dose of white spirit to wipe the evostick off. The only remaining problem is that the veneer is still about 1-2mm too wide and showing stains of white spirit (it's darkened the wood). I thought the white spirit evaporates completely

 

Dev, are you planning darken the veneer with a stain?
Those are usually spirit based and would probably even things out.

 

Yes Rob, that's the plan. I'm planning to stain them a bit redder.

 

Crossover and tuning questions

Hello!

I finally found someone else playing around with CPA12s!
A fantastic looking project, I must say.

I have some questions regarding CPA12 original design. Hopefully someone on this list might be able to help me as you have studied the things so much deeper?

I have a pair of the dual concentric drivers but can't find any info for the original cabinet's tuning frequency or the crossover - except for the crossover frequency 1.5k. As I am (or at least originally WAS before reading this thread) going to try to make my speakers according to the Tannoy's original design I would be grateful to get any info for the speakers. I have the spec sheet, but that doesn't give me the details I'm after.

I also found it very interesting to read about the crossover tweaking. Any chance for some further info?


Thanks to all for a very interesting thread!


Janne Auvinen
Turku, Finland

 

Hi Janne, welcome to the forum.

You need to talk to cooky1257. He's the best authority on Tannoys here.

 

Thanks for the tip! Just found another thread on (your?) crossover design. It seems like I'm going to have to start the project again!

Janne

 

Hi Janne some CPA info here;http://www.hilberink.nl/codehans/tannoy41.htm

The original cabinets are too small for hifi and are designed to be used with subwoofer, Dev's design is as good as you will get from these units in a conventional enclosure(non horn).

 

Hi Janne, do you have a pair of cabinets for the drivers?

I have some spare which you're welcome to if you like. Or if you need anything measured for dimensions etc just ask.

I've been watching this progress nicely and i'm about to make some new cabinets for the same drivers. I can't find the parameters anywhere though, and I can't have anything as big as those in my flat...

I might just make a slightly bigger box of about 100/110 litres and see how it goes, maybe port it if i have to

 

And finally:-

 

Dev, those look great.
I would seriously start looking for some nice 12" Golds or perhaps the 12" driver used in the more modern pro DCs.

Those cabinets deserve a really nice driver IMO.

 

I might have to Rob. Pity I didn't make them a couple of inches wider to accommodate 15" drivers .

 

hi dev, they look super, do you still have the bass problem on the left spkr?

 

Cabs look really nice Dev, I'd have to sort out the unfinished feet though;-)

 

Nope, it's sorted, after Roger glued the bass cone to the spider.

I understand there is something special about unfinished projects, like the unfinished symphony.

But seriously, I haven't even gotten around to levelling them yet. I was thinking of painting them black after cutting the corners off (see picture of the feet below), but for now, they remain unfinished.

 

Looking good Dev.
15" hehe

 

One day Steve, after the other half has recovered slightly.

 

I have wanted to build some big Tannoy cabinets myself for ages but never had the time. I noticed Dev had built some bigger cabs for his DMT 15 drivers so I contacted him on the off chance that he might want to sell these. He very kindly gave them to me for nothing and I've been experimenting for the past few months.

I have DMT12 Mk1s and i12s and both driver types fit the cabinet perfectly. I think both these and Dev's CPA12 drivers all use the same cast chassis. I used the DMT 12 drivers as they sound by far the best to me.

The balance between the drivers varies a lot depending on loading. With the cabs sealed as Dev made them, LF is much quieter than in the original ported cabs. Ported, the bass is a lot louder than the originals. As I don't have the skills to redesign the passive crossover and I already had 2 power amps and an active crossover, I decided to use them active so I could get a reasonable balance between the LF and HF drivers. I also experimented with a parametric equaliser.

Initially, I tried them sealed but with both my drivers, they sounded quite uninspiring - lacking much bass at all. I then tried them with the rear connection panel removed to act as a rudimentary port and this time there was loads of uncontrolled bass. I stuffed some old t-shirts in the holes and I managed to get a decent quantity of bass that was quite well controlled, so I decided to add some proper ports. I think I tuned them to about 40Hz as this is the -3dB point of the DMT12s and I assume the driver wouldn't be happy being asked to go lower.

Anyway, I've had a lot of fun but I feel I would need to tinker a lot longer to get the balance just right and the original cabinets are a better size for my room so I've decided to let them go. If anyone would like them, please get in touch. They are very heavy and big - they only just fitted in the back of my largish estate car. They are 108h x 50d x 45w cm. I live in Chelmsford, Essex.