GAMMA 30 experiement
- Thread starter Adda
- Start date
Adda
Super Member
Thanks man, it seems it has finally reached the result I want.
Now I just have to refine it, but the crossover seems done, I'm wondering if I should get a 4ohm LA1231, rather then 8ohm, for lower inductance.
But as far as I understand, both the woofer and tweeter impedance affect the highpass filter, so I'll have to redesign he highpass filter if I lower the woofer impedance.
I'm not sure I want to do that, we'll see.
Now I just have to refine it, but the crossover seems done, I'm wondering if I should get a 4ohm LA1231, rather then 8ohm, for lower inductance.
But as far as I understand, both the woofer and tweeter impedance affect the highpass filter, so I'll have to redesign he highpass filter if I lower the woofer impedance.
I'm not sure I want to do that, we'll see.
Adda
Super Member
Ah the woofer impedance does not affect the tweeter crossover, but since both the 8 and 4 ohm LA1231 play equally loud at 1w of power, they will not have the same efficiency.
If you fed them the same voltage, the 4 ohm driver would play louder.
I should stick with 8 ohms.
Edit: another advantage to sticking with 8 ohms, is magnet compatibility, it seems 4 and 8 ohm drivers have different magnet strengths, usually anyway.
If you fed them the same voltage, the 4 ohm driver would play louder.
I should stick with 8 ohms.
Edit: another advantage to sticking with 8 ohms, is magnet compatibility, it seems 4 and 8 ohm drivers have different magnet strengths, usually anyway.
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Adda
Super Member
So it's been a few days since I build my new crossover, I have tone sweeped, played all kinds of music of all qualities, quiet and as loud as I dare.
I can't find any problems with this crossover, it works just as intended and sounds fantastic!
The speakers go right to the edge, but never cross it, they don't become sharp, piercing or sibilant, but they almost do with some recordings, but never too much.
They bring out the best in poor recordings, and reveal the goodness in great recordings.
8-bit chiptunes, noisy electro industrial, 80's David Bowie and New Order, the Skyrim, Blade Runner and Ghost in the Shell soundtracks, Tubular Bells or Harshlizer, don't matter it's all good.
All they need is more bass, and it would be nice to try and improve directionality, but I definitely need more bass, the box needs work.
I can't find any problems with this crossover, it works just as intended and sounds fantastic!
The speakers go right to the edge, but never cross it, they don't become sharp, piercing or sibilant, but they almost do with some recordings, but never too much.
They bring out the best in poor recordings, and reveal the goodness in great recordings.
8-bit chiptunes, noisy electro industrial, 80's David Bowie and New Order, the Skyrim, Blade Runner and Ghost in the Shell soundtracks, Tubular Bells or Harshlizer, don't matter it's all good.
All they need is more bass, and it would be nice to try and improve directionality, but I definitely need more bass, the box needs work.
Adda
Super Member
GAMMAs are versatile, durable and well behaved, I really have tried very hard to find alternatives :yes:
The VLD-12's are as good ribbons as any, within a reasonable price range of cause.
The GAMMA/Vissokogovoriteli VLD-12/13/40 and VLDD80, the Howard Dawson HRL-1, Expolinear NDRL 81/82 and DECCA/Kelly DK30 and London, are all of the same basic design.
The differences are mostly cosmetic, and they have different efficiencies of cause, the most efficient being the Expolinear NDRL 81 at 92dB/w without horn.
The NDRL's are basically VLDD80's with fancy ribbons and Neodymium magnets.
The GAMMA/Vissokogovoriteli BK3013A, LA1231, VKN12211/311 all appear to be the same, both electrically and mechanically.
The only differences being that the new ones have ferrite magnets rather then AlNiCo, and some minor construction differences (PCB in old versions replaced by wiring in new ones).
They seem to be one of a kind, maybe other vintage woofers are similar, but these are still in production.
It's such a shame Vissokogovoriteli are so hard to come by on international markets, it's as if they don't feel too keen on selling their product, at least outside of Bulgaria.
Adda
Super Member
I have been tinkering with Boxsim, and I think I can simulate my crossovers now, roughly.
My crossover is pretty good according to this app, phase is good, but there is a small bump (1.5dB) just before the crossover frequency, which is at 5KHz.
By replacing the 3.3uF cap in the filter with a 1.5uF, I should be able to fix it, and improve phase response a little (very little it is already very close).
Luckily I have a pair of 1.5uF caps.
My crossover is pretty good according to this app, phase is good, but there is a small bump (1.5dB) just before the crossover frequency, which is at 5KHz.
By replacing the 3.3uF cap in the filter with a 1.5uF, I should be able to fix it, and improve phase response a little (very little it is already very close).
Luckily I have a pair of 1.5uF caps.
Adda
Super Member
This crossover:
Looks like this according to Boxsim and my abilities with the app:
Ignore bass output, I didn't put effort in to it.
I did not include the phase response graph, as I doubt it's validity, it shows an almost perfect mating between the two drivers.
Reducing the size of the coil will introduce phase distortion, even just reducing it's size to 0.27mH.
It seems the 0,3mH coil is meant to be.
Looks like this according to Boxsim and my abilities with the app:
Ignore bass output, I didn't put effort in to it.
I did not include the phase response graph, as I doubt it's validity, it shows an almost perfect mating between the two drivers.
Reducing the size of the coil will introduce phase distortion, even just reducing it's size to 0.27mH.
It seems the 0,3mH coil is meant to be.
Adda
Super Member
I have been experimenting with the old Audioscan style crossover in Boxsim, and it seems it can't work, unless the woofer is assisted by directivity.
No matter what, I get a peak around 2KHz when using that filter.
My new (mkIII) filters all seem to work, which is better depends on taste, listening position and how effectively the phaseplug (if any) works.
v1.00 has a hump around the crossover point, this should compensate for woofer directivity, to some degree, within a certain range of angles, as long as ears are at tweeter height.
v1.01 has a significantly smaller hump around the crossover point, it's the filter I'm using now, and I think it provides a good balance and best sound from a wide range of angles.
But more testing is needed.
v1.02 is yet to be built, it should provide the best on axis frequency response, we'll see once the parts arrive.
Finding the best filter out of these will most likely take a while, and the phaseplugs will certainly affect which works best.
No matter what, I get a peak around 2KHz when using that filter.
My new (mkIII) filters all seem to work, which is better depends on taste, listening position and how effectively the phaseplug (if any) works.
v1.00 has a hump around the crossover point, this should compensate for woofer directivity, to some degree, within a certain range of angles, as long as ears are at tweeter height.
v1.01 has a significantly smaller hump around the crossover point, it's the filter I'm using now, and I think it provides a good balance and best sound from a wide range of angles.
But more testing is needed.
v1.02 is yet to be built, it should provide the best on axis frequency response, we'll see once the parts arrive.
Finding the best filter out of these will most likely take a while, and the phaseplugs will certainly affect which works best.
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Adda
Super Member
I compared the original GAMMA 30 filter to my current filter in Boxsim, and they do very much the same thing, except, my filter does it to a smaller degree.
They both make a linear increase in amplitude from 1-5Khz, topping out at +9dB for the Audioscan filter, my filter tops out a +6dB.
I'm looking forward to some higher SPL listening tomorrow, to see what happens.
They both make a linear increase in amplitude from 1-5Khz, topping out at +9dB for the Audioscan filter, my filter tops out a +6dB.
I'm looking forward to some higher SPL listening tomorrow, to see what happens.
Adda
Super Member
So the mkIII filter sounds best, but the mkII filter sounds more consistent.
The mkII filter has quite limited SPL, it starts sounding rougher as volume goes up, but is great a low-moderate volumes.
The mkIII filter is like a hologram, literally, you most likely know those holographic stickers, with different 3d images on them
The mkIII filter makes my speakers like that, excellent imaging and depth, but as I change angles, the colors change, again like a hologram.
This makes cymbals and high hats and other upper mids lower treble sounds illusive at certain angles.
I'd like to combine attributes from both kind of filters, I have found a phaseplug source, but I'll have to wait from them to arrive.
I doubt they will be able to solve the directivity problem with the mkIII filter, but maybe it'll help enough to make it work better.
Right now I'm not sure what to do, the mkIII filter sounds better and plays louder, but is highly inconsistent due to serious directivity problems.
The mkII filter has limited SPL and sounds rougher all round and the woofer isn't "invisible", but is much more consistent with it's superior directivity.
Difficult choice, but I can't make it now anyway, I have to see what phaseplugs can do, maybe I'll settle for a compromise between the two methods.
The guy from Bulgaria that put phaseplugs in his VKN woofers, is crossing somewhere between 4 and 5KHz, it seems he made the compromise I think I'll have to make as well.
I should see what I can do to cross at 4KHz, I have filters for 3KHz and 5KHz, I shoud make one for 4KHz too.
The mkII filter has quite limited SPL, it starts sounding rougher as volume goes up, but is great a low-moderate volumes.
The mkIII filter is like a hologram, literally, you most likely know those holographic stickers, with different 3d images on them
The mkIII filter makes my speakers like that, excellent imaging and depth, but as I change angles, the colors change, again like a hologram.
This makes cymbals and high hats and other upper mids lower treble sounds illusive at certain angles.
I'd like to combine attributes from both kind of filters, I have found a phaseplug source, but I'll have to wait from them to arrive.
I doubt they will be able to solve the directivity problem with the mkIII filter, but maybe it'll help enough to make it work better.
Right now I'm not sure what to do, the mkIII filter sounds better and plays louder, but is highly inconsistent due to serious directivity problems.
The mkII filter has limited SPL and sounds rougher all round and the woofer isn't "invisible", but is much more consistent with it's superior directivity.
Difficult choice, but I can't make it now anyway, I have to see what phaseplugs can do, maybe I'll settle for a compromise between the two methods.
The guy from Bulgaria that put phaseplugs in his VKN woofers, is crossing somewhere between 4 and 5KHz, it seems he made the compromise I think I'll have to make as well.
I should see what I can do to cross at 4KHz, I have filters for 3KHz and 5KHz, I shoud make one for 4KHz too.