DIY TA-7331-A here we go...

Wntrmute2

Not So Mediocre Member
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Nice-ola!
Were there not some louvers or some contraption at the back end or am i mixing these up with another build?
 

billfort

Administrator
Staff member
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These look great in that room Mr.E, what a fantastic setup.

Looking forward to hearing about them once finished and settled in.
 

MrEd

Senior Nobody
Site Supporter
Thanks for all the positive comments.
I hope do some measurements later todsy and then get my sub back into the room after that.
So far I have a really nice full and large sound stage and sounds nice, but I might have the mids touch too much still.
 
I took measurement and the voice coils are both 6.7 ohm, the field coils are 658 and 669 ohm.
The date codes are 1 year apart.
I have not been able find any info on what years the were used, I am going to assume they are from the 50's.
The 4th digit is the year but it is 0 through 9 the the next two digits are the week of the year. 285 is Rola, 280 is Jensen. I have 285225 and 285125.
Awesome project. Kudos!

I've a pair of A12's (with usual mismatched FCs found from pairs pulled from tone cabs) you're inspiring me to dust off and play with. I think mine are both from '47.

Re: date codes, from what I've read the EIA codes didn't come in until after '45, so odds are yours are '52 and '51, respectively. Would they have made them in the 60's??

Another way to tell earlier from later is the use of phenolic spiders in the earlier models.B26B7F2F-59A5-4A15-8532-5BC18C12E656.jpeg
 
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Hey,

I initially got these given the raves about FCs and after having communicated with a German gent who went from WE15a's down to A12's (in TA-7331's) with jensen rp103 tweeters and seemed happy enough with that transition. So you're on the right track, based on his views!
I've extracted some of his messages at the end of my post for reference (I don't think he'd mind me sharing).

Right now, and as you might have seen from my DIY speaker extravaganza ad, I'm trying to sell a load of surplus kit after having finished my DIY speakers. I had thought about using the A12's in the DIY speakers but, as they'd be used daily for HT and music and not just by me (I've 2 tween-aged girls) and I've yet to find another with the same FC impedance, I went with GPA'd 414's instead.

A possible use might be to install one of them in a UK version of the WE D-94675 'loudspeaking telephone unit' I recently found. I posted some details about the find here on the massive WE thread on lencoheaven, see: https://www.lencoheaven.net/forum/index.php?topic=7616.1650

My unit sadly had the original KS/TA 7109 FC woofer replaced with a Rola PM somewhere along the way and, from what I've read, they had a FC of 2300 ohms, which is a close enough match for one of my A12s. I could also add a jensen rp103 on top (similar to the silbatone approach of adding a 597a). However, currently undecided as to whether to keep the WE unit as the long-term running costs of 262's, 274s and 275s for a mono, second speaker is pretty prohibitive. Now, if i came across a 555 and had the space for a mono 15a etc, then that would be a different story altogether!

For now, still keeping an eye out for a single A12 to make a matched pair and may well look at installing them in the DIY jobbies down the track.

Cheers,
Adrian

"I am using a 12 inch field coil woofer now (Jensen A-12) but didn't make any measurements concerning frequency response. From my experience i would say that it goes down to 30Hz, maybe even 25Hz. The correct balance between bass and treble can only be achieved by finetuning the field coil voltage until it's perfect (very easy to do, since you hear it immediately). I woud definitely not recommend to use a permanent magnet woofer in this enclosure. It can sound quite good with one of them (maybe even an Altec 803a), but you'll never get the best out of it. And it's worth getting the best
wink


In my setup the 8ohms woofers run up to 5kHz without filter and the 16ohms tweeters are coupled with 2µF. That's it and it's perfect! Extremely fast, deep, clear and colorful."

"The point about FC woofers is that you adjust the Qts by adjusting the field. And the point about the 7331 is that they seem to sound excellent with every kind of woofer. That's why you can get a real perfect match by combining 7331 & FC. To be honest, i had much luck with my setup because i'm no expert and i made my decisions based on my personal experience with the 15A horns (that i unfortunately don't have anymore). So no, i don't know the quater-wave resonant frequency. The dispersion of the 7331 is fantastic – another point i had luck with, because i had the same doubts like you. Fact is that the woofers don't seem to beam at all. I'm pretty sure that this effect is caused by the construction of the 7331s, so i wouldn't recommend to change this. And believe me: there's no need for two woofers in one 7331
smiley.gif
It would be overkill – at least in a 2-way system. But even with 3 ways and a quite loud mid-horn the 7331 should work fine and be loud enough."

"i am using Jensen RP103 tweeters with their 106 horns. They have 16 Ohms voice coils, so there is no need for more than a 2µF condenser to make a perfect match to the 8 Ohms woofers. They are positioned on top of the 7331 on a very thick felt layer – extremely important to prevent reflections from the wood surface wich make them soud harsh."

"Well, of course i loved the 15A setup a lot. It surely wasn't perfect – whatever that means – but it sounded just the way i like it and i hoped: natural, clean, quick, detailed, colorful, airy, vivid....with the authority one would expect from such a big system
smiley.gif
Fantastic!

The biggest surprise for me was to hear pretty much of these characteristics from the small 7331 setup. In my normal-sized livingroom the 7331 does "the same thing" like the 15A in the much bigger room – it's just proportionally downsized. The magic is there, the speed, the natural, live-like sound....just a little bit more compact, somehow like a distillate of the 15A. You see: i love it
smiley.gif


And there is even one thing the 7331 does better than the 15A: it plays the whole spectrum from say 30Hz to 5kHz without the need of a subwoofer. For my 15As i used two small bass horns that were integrated quite well soundwise. But it wasn't that really deep, fast, dry and strong bass of the 7331.

I don't state that a 7331 sounds like a 15A. But it brings the same fun to the listener, is much cheaper and smaller
smiley.gif
Nonethless i'm very happy with the 15A experience – better: adventure. I learned a lot, had loads of fun and don't want to miss these years."
 

MrEd

Senior Nobody
Site Supporter
Hey,

I initially got these given the raves about FCs and after having communicated with a German gent who went from WE15a's down to A12's (in TA-7331's) with jensen rp103 tweeters and seemed happy enough with that transition. So you're on the right track, based on his views!
I've extracted some of his messages at the end of my post for reference (I don't think he'd mind me sharing).

Right now, and as you might have seen from my DIY speaker extravaganza ad, I'm trying to sell a load of surplus kit after having finished my DIY speakers. I had thought about using the A12's in the DIY speakers but, as they'd be used daily for HT and music and not just by me (I've 2 tween-aged girls) and I've yet to find another with the same FC impedance, I went with GPA'd 414's instead.

A possible use might be to install one of them in a UK version of the WE D-94675 'loudspeaking telephone unit' I recently found. I posted some details about the find here on the massive WE thread on lencoheaven, see: https://www.lencoheaven.net/forum/index.php?topic=7616.1650

My unit sadly had the original KS/TA 7109 FC woofer replaced with a Rola PM somewhere along the way and, from what I've read, they had a FC of 2300 ohms, which is a close enough match for one of my A12s. I could also add a jensen rp103 on top (similar to the silbatone approach of adding a 597a). However, currently undecided as to whether to keep the WE unit as the long-term running costs of 262's, 274s and 275s for a mono, second speaker is pretty prohibitive. Now, if i came across a 555 and had the space for a mono 15a etc, then that would be a different story altogether!

For now, still keeping an eye out for a single A12 to make a matched pair and may well look at installing them in the DIY jobbies down the track.

Cheers,
Adrian

"I am using a 12 inch field coil woofer now (Jensen A-12) but didn't make any measurements concerning frequency response. From my experience i would say that it goes down to 30Hz, maybe even 25Hz. The correct balance between bass and treble can only be achieved by finetuning the field coil voltage until it's perfect (very easy to do, since you hear it immediately). I woud definitely not recommend to use a permanent magnet woofer in this enclosure. It can sound quite good with one of them (maybe even an Altec 803a), but you'll never get the best out of it. And it's worth getting the best
wink


In my setup the 8ohms woofers run up to 5kHz without filter and the 16ohms tweeters are coupled with 2µF. That's it and it's perfect! Extremely fast, deep, clear and colorful."

"The point about FC woofers is that you adjust the Qts by adjusting the field. And the point about the 7331 is that they seem to sound excellent with every kind of woofer. That's why you can get a real perfect match by combining 7331 & FC. To be honest, i had much luck with my setup because i'm no expert and i made my decisions based on my personal experience with the 15A horns (that i unfortunately don't have anymore). So no, i don't know the quater-wave resonant frequency. The dispersion of the 7331 is fantastic – another point i had luck with, because i had the same doubts like you. Fact is that the woofers don't seem to beam at all. I'm pretty sure that this effect is caused by the construction of the 7331s, so i wouldn't recommend to change this. And believe me: there's no need for two woofers in one 7331
smiley.gif
It would be overkill – at least in a 2-way system. But even with 3 ways and a quite loud mid-horn the 7331 should work fine and be loud enough."

"i am using Jensen RP103 tweeters with their 106 horns. They have 16 Ohms voice coils, so there is no need for more than a 2µF condenser to make a perfect match to the 8 Ohms woofers. They are positioned on top of the 7331 on a very thick felt layer – extremely important to prevent reflections from the wood surface wich make them soud harsh."

"Well, of course i loved the 15A setup a lot. It surely wasn't perfect – whatever that means – but it sounded just the way i like it and i hoped: natural, clean, quick, detailed, colorful, airy, vivid....with the authority one would expect from such a big system
smiley.gif
Fantastic!

The biggest surprise for me was to hear pretty much of these characteristics from the small 7331 setup. In my normal-sized livingroom the 7331 does "the same thing" like the 15A in the much bigger room – it's just proportionally downsized. The magic is there, the speed, the natural, live-like sound....just a little bit more compact, somehow like a distillate of the 15A. You see: i love it
smiley.gif


And there is even one thing the 7331 does better than the 15A: it plays the whole spectrum from say 30Hz to 5kHz without the need of a subwoofer. For my 15As i used two small bass horns that were integrated quite well soundwise. But it wasn't that really deep, fast, dry and strong bass of the 7331.

I don't state that a 7331 sounds like a 15A. But it brings the same fun to the listener, is much cheaper and smaller
smiley.gif
Nonethless i'm very happy with the 15A experience – better: adventure. I learned a lot, had loads of fun and don't want to miss these years."
Thanks for sharing.
I do agree that that the 7331 is quite impressive.
I am still in the beginning of this adventure. 🙂
 

MrEd

Senior Nobody
Site Supporter
I am curious if you could compare and contrast the 7331 with your A7
The 7331 fills the room with a bigger presence and a better sound stage, the 825 cabs with 416's seem to be a bit darker or maybe not as natural tone wise.
I am crossing these higher than the Altec cabs.
The bass is very defined and a bit more real maybe.
 
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MrEd

Senior Nobody
Site Supporter
@Rahman ,
You inspired me to put the Rola field coil drivers back in...
I have been working on crossover and power supply this afternoon.
I feel at this point with these drivers and the settings I have right now there is no need for a sub for anything that I normally listen to.
These are not as efficient as the Magnavox woofers but dig deeper for sure and the Magnavox are no slouch.
Definitely a fun project.
 
Hey

Great to hear and, often, simpler is better!

Wish I had the space for 7331's but I could see the a12's in a 100L bass reflex (same as my 414s) and just tuning the FC voltage to get the right bass output and also tame the HF.

Enjoy!

Cheers
Adrian
 
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