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GAMMA 30 experiement

So how does the finished product compare to the test bed?

My new speakers sound warmer, they have significantly more bass, fine down to 50Hz or so.
They are much more detailed, something the old worn down BK3013A's had a hard time with, but the retain the lovely sound.
They sound open and effortless as usual, very nimble with super fast transients, they make it sound so easy.
The "EEE" problem is totally gone.

If you don't want to use a 12" woofer for the midrange but is still interested in GAMMA woofers, but want to use them for what they do best, use them as a midbass uinit in an aperiodic box, you wont regret it, they are wicked!
Very fast and detailed, with such a nice tone, very dynamic.

Their midrange is open and detailed, with great depth and presence, you wouldn't think a woofer was involved.
Directivity is an issue though, but it's not as bad as you think, especially not when the speakers are placed at a distance.

The ribbons add air and space to everything, and integrate flawlessly with the LA1231's, it's incredible that such big woofers can keep up with the ribbons, but they where made for each other so...

Damn they can even rumble now :D

Compact aperiodic boxes have been approved by me, and are HIGHLY recommended, the speed and detail is what you want, perfect for midbass drivers.
 
Another pic!

6e4dfdad_AUT_0003.jpeg
 
Very nice, Adda! This build deserves WAY more attention than it's getting here on AK. You've tweaked like a madman (!:thmbsp:!) and now have something to show for it that you're clearly very proud of and that, IMO, is highly commendable. You and I both had a suspicion there was something there with aperiodic venting. I'm glad you beat me to the punch in implementing it successfully...now I can just follow your recipe! :yes:
 
And can you please provide a brief synopsis on driver complement, crossover points, network construction, box volume and operating range?
 
Thanks Michael!

I'll get right to the explanation of what these are.

Box volume is right around 60 liters (~2.11ft³), sports two Scan-Speak Flow Resistors per box, and are stuffed with rockwool.
The flow resistors have been placed on the back of the speakers, near the bottom in a vertical orientation.

The tweeters are the GAMMA VLD-12 8 ohm horn loaded ribbons (compatible with GAMMA/Vissokogovoriteli VLD-13, VLD-40, and possibly also the DECCA DK30).
Mine use Howard Dawson ribbons at this time.

The woofers are GAMMA LA1231 4 ohm with ferrite magnets(compatible with GAMMA/Vissokogovoriteli BK3013A and VKN12211/311).
AlNiCo or ferrite models can be used.
Both 4 and 8 ohm models are compatible since no low pass filter is used.
The dustcaps have been removed and short phase plugs added for much improved upper midrange.

The crossover network is a very basic 3rd order highpass filter crossing at 4KHz -6dB and uses standard component values for easy construction.

0743f065_wVKN4ohm.png


This graph shows an on axis response, this is not what is heard in real life as the woofer is under the tweeter.
The tweeter is supposed to be at ear height, so the hump you see around the crossover point isn't there, since the woofers have very limited dispersion at those frequencies.
Bass response is not accurate in this graph.
The impedance response at Fs isn't accurate either, it will be significantly flattened by the flow resistors.

Usable frequency range is from 50Hz and up, measured by ear.
 
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Great thread. I think it would have gotten more readers and posters over in the Speakers forum. For some reason the DIY forum does not have a lot of traffic. Anyway, nice job on a very unusual and high quality pair of speakers.
 
Thanks!

After all the testing, tinkering and bad drivers I have gone though, it's great to finally have a product, and a bloody good one at that!

Next stop USB power supply (Aqvox) then speaker cabling (maybe) and finally subwoofers (preferably stereo! meybe even DIY).
 
I'll just talk a bit about the GAMMA BK3013A vs. LA1231

The BK3013A has a few design problems, the surrounds are very fragile, not that they tear easily, but they deform easily when mounting the woofers on a baffle.
This is because the gasket is soft, the screw holes go right through them, the glue they used is hard and brittle, and the surrounds are glued to the basket right underneath the gasket.
So when screwing the woofers down, the gasket will compress, expand and then the glue lets go and the surround deforms...
You'd think those woofers weren't meant to be mounted anywhere.
The glue is fragile and ages poorly, with age is turns to powder or looses it's grip, so the woofer will fall apart and start leaking air in all sorts of places.
The spider and surrounds loose tension with age, ruining the woofer, the process is accelerated by moisture and long term storage.
Out of the eight BK3013A's I have had, four didn't suffer from sagging loose spider/surrounds.
Keep in mind that these are woofers made from 1966-early 80's, so they hold up pretty well considering the low cost.

Enter the LA1231, with tougher surrounds, better glue, harder gasket, different spider and a simplified design, they seem to have addressed all the problems that plagued the BK3013A's except terrible quality control.
You can screw them down no prob, the surrounds are thicker and seem much more rugged, the spider has a different color and texture and the PCB has been replaced by simple wiring.
My LA1231's where made in 1992 and 1994 respectively, NOS.

So how are the Howard Dawson ribbons when used in VLD-12's? LINEAR!
 
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The "EEE" problem has crawled up on me again, but only at loud volumes on some recordings.
So in their current state, these speakers are not for playing loud, they do go fairly loud though.
So not all changes related to burn-in are good, they mostly are though, I get more and more bass and detail as they settle down.
I have narrowed it down to somewhere around 2kHz, so it has nothing to do with the crossover network.

My guess is that coating the inner cone to stiffen it a bit will fix it, maybe dampening the basket with felt will help too.

I'll see how things develop in the longer run.
 
I think the LA1231's are just about burned in by now.
The speakers have gotten a warmish sound, quite nice, and have enough bass, not over the top, more like a studio monitor.
Full but not bloated, nice and tuneful, the kind of speaker you don't even feel the need to play loud, moderate volumes or less is just fine.
I no longer feel an urgent need for a subwoofer either, in fact I'm wondering if I want to bother at all.
I should do another tone sweep when people are not sleeping.

An Aqvox USB power supply is on it's way, from what I read, it's going to be a substantial upgrade for my hiFace Two, especially in the bass region, which is already top dollar!
My speakers never had satisfying bass, when they had BR tubes they sounded kind of bloated, and the mids suffered, when they where sealed it didn't go low enough.
Now it goes low enough to make me happy and it's so fast and controlled, just great, and detailed too, even airy, airy bass, if there is such a thing.
They fill the room nicely too.
 
Well, I have moved in to a different apartment, 2nd time I move this year, hurraaayy where will I move to next? :D

Anyway, my old place was a bass killer, my new place isn't!! I got a dedicated AND carpeted listening area! damn! no I do not need a subwoofer at all, these babies can really move some air!
Oh yes I can feel the bass, I'll have to get used to that :banana:

Big ass widebanders are awesome! the rarest and craziest type of woofer you'll never come across.

This is great, I'll have to get some acoustic panels sometime.
I'll also have to do some tone sweeps at some point, and I need to experiment with placement as well.
 
Well how to make a big widebander, if you can't find a "true" widebander?

Well, a big ass widebander is more then just similar to a large fullrange driver.
The main difference is that a widebander doesn't have a whizzer cone, and they tend to have phaseplugs, same as fullrangers.

But who's keeping you from buying a big 10-15" fullrange driver, and then removing the whizzer cone and add phaseplugs, if they don't have them already?
 
Adda said:
It seems VLD-12 ribbon tweeters where sold in the UK under the name "Audio-Tronic".

So drivers made by Vissokogovoriteli, has been sold under the names, GAMMA, Jordanov, Expolinear, Giant and Audio-Tronic.
Click to expand...

Audio-Tronic was a company founded by Bo Bengtsson and active during the 70's - 80's and perhaps 90's, After that he was involved with Red Rose.
He used the black VLD-13 horns with modified ribbons of his own hands, in all of his models. Think the used woofers were Kef B-200's.
Perhaps there were more modifications to the original units, guess it's still kept a secret.
The Bulgarian units were very popular for different kits until the factory started to lack in production quality, lacking spec. tolerances together with heavily rising their prices.
Numbers of LA-1231/BK3013 were popular used in pricey home-semi-discoteque speakers with stacks of Motorola piezos on top.

Nice diy thread :thmbsp:
 
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Cpectrum said:
Audio-Tronic was a company founded by Bo Bengtsson and active during the 70's - 80's and perhaps 90's, After that he was involved with Red Rose.
He used the black VLD-13 horns with modified ribbons of his own hands, in all of his models. Think the used woofers were Kef B-200's.
Perhaps there were more modifications to the original units, guess it's still kept a secret.
The Bulgarian units were very popular for different kits until the factory started to lack in production quality, lacking spec. tolerances together with heavily rising their prices.
Numbers of LA-1231/BK3013 were popular used in pricey home-semi-discoteque speakers with stacks of Motorola piezos on top.

Nice diy thread :thmbsp:
Click to expand...

Exactly, I have since learned that :)
Bo Bengtsson did indeed use B200's, but must have used both VLD-12 and 13's as I have seen a picture of a gray Audiotronic VLD tweeter.
Audiotronic VLD's have custom transformers, enabling them to be crossed with 1st order crossovers.

Today, Audiotronic is known as Transmission Audio.

Vissokogovoriteli (who makes the VLD's and BK3013A/LA1231/VKN12211/311) have always had a quality control problem.
I have not yet owned a Vissokogovoriteli (GAMMA) product without production flaws or defects.
I have ten VLD-12's, two VLD-13's, eight BK3013A's and two LA1231's.
A few VLD-12's have crooked magnets, flaws in thew cast, flaws in the cutouts in the metal, poorly fitted PCB's that don't age well.
The VLD-13's are perfect but very rough looking, one was dropped though, to the magnet assembly is no good.
Some BK3013A's suffer from scraping voice coil problem, are hard to mount due to problems I have described earlier, and don't age very well.
LA1231's are poorly assembled, but use higher quality materials compared to BK3013A's and age better.
By far most of them are perfectly functional though, the flaws are mostly cosmetic.
Prices are still very low in Bulgaria.

If only Vissokogovoriteli would sort out the quality issues, and make a VKN series woofer with phase plugs and a stiffening coating around the middle of the cone, and do the same to their dual voice coil version of the woofer, well then they'd have awesome products, all they'd need to do is improve availability.
 
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Transmission audio yes, most of his speakers were transmission line so the newer company name seems apropriate :)

I really did like his speakers in some aspects, they had a great lively and clean party sound and could play loud.
but! they had some linearity problems on low levels and the sweetspot was very narrow.
Like big headphones with a lively sound but not the best of details.

Yes it's sad that quality wasn't in focus at the "Gamma" factory.
Guess it's the many years of communism responsible for it.
Are they developing new models or just the old products?
It would be nice to take a peek at the products they still produce with realistic measurements.

It will be sweet to follow your project.
 
Well today, Transmission Audio makes small to medium size BR speakers, and some of the most incredible dipole speakers ever conceived.
He even designed a fullrange ribbon speaker, all true ribbon, no woofers, no ESL or planars mixed in there, just true ribbons.

My speakers have a narrow dispersion pattern too, a result of the horn and large woofer with a high crossover point.
But they sound great, you won't find better bang for the buck anywhere and you won't find woofers or tweeters with the same capabilities as the GAMMA's.
Well ok, there is the DECCA DK30, but it's not in production anymore, is very expensive on the used market, and at least one person have compared them to the VLD's and told about it, he prefers the VLD's!

I think Vissokogovoriteli is focusing on the local market, and Bulgaria isn't a particularly wealthy country, so they have to keep costs down.
But now that Bulgaria has become a member of the EU, we can hope that they change their strategy.

They have introduced some new products along the way, but it seems most of what they have done is simplify the design of old products, and convert their AlNiCo motors to ferrite.
The VLD's still use AlNiCo magnets though.
Their high end models are still the same old VLD and VKN series drivers, developed in the late 60's.
They where simplified and improved a bit during the 80's, but they sound the same.

The current VKN12211/311 woofer, measures the same as the old BK3013A and LA1231, It's incredibly linear, I have posted measurements in this thread.
The VLD's are linear to within 1dB above 3kHz, some of the most linear tweeters ever made.

Toshko from the penkiller forum measured a bunch of VKN woofers and says the result is the same as the old measurements.
There are some variations in T/S parameters between units, but they perform similarly.

I'm pretty much done with my project at this time, I may add a PVA coat to the inner cone of my LA1231's, but I'm not sure they need it.
If I feel like upgrading at some point, I'll probably do it.
 
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