GAMMA 30 experiement
- Thread starter Adda
- Start date
Adda
Super Member
Apart from being directional, the LA1231 should do fine it's pretty well behaved up to around 2500Hz, which is close to the point I'll cross them over.
If you look around, you'll find that people get quite surprised by the midrange of the LA1231, and the sounds BK3013A is good too if it wasn't for those peaks.
Well those 0.8mH coils will be the last thing I'll try on the crossover before I have saved up for a pair of LA1231's.
Adda
Super Member
Or maybe I should get out my 6" Wavecor WF152BD02 Nomex drivers in stead, I have four of them, but they only need a 15 liter box, with a 22cm long 7cm diameter tube.
I can calculate that I can reuse the same coils I have but need to put some large caps in parallel with the 6.8uF ones.
I can calculate that I can reuse the same coils I have but need to put some large caps in parallel with the 6.8uF ones.
Adda
Super Member
The problems that have kept me from using the Wavecor drivers is that, I don't know how to go about using two drivers with low Vas, while making use of my 50 liter box.
Could I make a push pull system?
I have read about multi chamber bass reflex systems where the chambers are connected by a tube.
I read about bass reflex systems with two isolated chambers.
Or one big chamber for both drivers.
But I just don't know how to go about this.
speacs for the Wavecor WF152BD02:
Nominal size 6 [inch.]
Nominal impedance 8 [ohm]
Recommended max. upper frequency limit 3.5 [kHz]
Sensitivity, 2.83V/1m (average SPL in range 400 - 1,000 Hz) 87 [dB]
Power handling, continuous, IEC 268-5, no additional filtering 70 [W]
Effective radiating area, Sd 93 [sq.cm]
Resonance frequency (free air, no baffle), Fs 47.5[Hz]
Moving mass, incl. air (free air, no baffle), Mms 12.8 [g]
Force factor, Bxl 7.9
Suspension compliance, Cms 0.83 [mm/N]
Equivalent air volume, Vas 10.8 [lit.]
Mechanical Q, Qms 11
Electrical Q, Qes 0.39
Total Q, Qts 0.37
Voice coil resistance, RDC 6.3 [ohm]
Voice coil inductance, Le (measured at 10 kHz) 0.19 [mH]
Voice coil inside diameter 32 [mm]
Voice coil winding height 5 [mm]
Air gap height 14 [mm]
Could I make a push pull system?
I have read about multi chamber bass reflex systems where the chambers are connected by a tube.
I read about bass reflex systems with two isolated chambers.
Or one big chamber for both drivers.
But I just don't know how to go about this.
speacs for the Wavecor WF152BD02:
Nominal size 6 [inch.]
Nominal impedance 8 [ohm]
Recommended max. upper frequency limit 3.5 [kHz]
Sensitivity, 2.83V/1m (average SPL in range 400 - 1,000 Hz) 87 [dB]
Power handling, continuous, IEC 268-5, no additional filtering 70 [W]
Effective radiating area, Sd 93 [sq.cm]
Resonance frequency (free air, no baffle), Fs 47.5[Hz]
Moving mass, incl. air (free air, no baffle), Mms 12.8 [g]
Force factor, Bxl 7.9
Suspension compliance, Cms 0.83 [mm/N]
Equivalent air volume, Vas 10.8 [lit.]
Mechanical Q, Qms 11
Electrical Q, Qes 0.39
Total Q, Qts 0.37
Voice coil resistance, RDC 6.3 [ohm]
Voice coil inductance, Le (measured at 10 kHz) 0.19 [mH]
Voice coil inside diameter 32 [mm]
Voice coil winding height 5 [mm]
Air gap height 14 [mm]
Adda
Super Member
I guess I could just devide my box in to chambers, one that's 15 liters, and dampened with wool, and one for the ribbons and crossover filters, and at the bottom a chamber with whatever space is left over.
But these drivers would need a chamber that's only about 20cm section of the box's height of 68.1cm.
The drivers would have to be mounted horizontally.
Of cause the horn will get a rather big chamber due to it's height, probably about a 30cm section.
18.1cm in excess.
But these drivers would need a chamber that's only about 20cm section of the box's height of 68.1cm.
The drivers would have to be mounted horizontally.
Of cause the horn will get a rather big chamber due to it's height, probably about a 30cm section.
18.1cm in excess.
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For two drivers in the same chamber, you just double the volume you calculated for the single, so 30 liters. The vent would be the same as if you were calculating a single driver in the 30 liter box. Maybe after you subtract the vent volume and driver volumes 50 liters won't be too far off. You'd probably want to go 2.5-way vertical, though. I think your center-to-center spacing would still be too far for the 2500Hz crossover range you're talking about, i.e. you'd get nulls in your horizontal response if you put them side-by-side. I didn't really calculate or simulate any of this, though.
Adda
Super Member
Vas is only 10.8 liters, but since I don't want to stuff the chamber with closed cell foam, I'll make it 15 liters, and stuff it with wool.
Yeah 2.5 way would be very cool, should be fine in a closed box right?
I do have some boxes that are 30 liters, if I divide that box up in two chambers, one for each driver, and do the 2.5 way crossover trick.
Expensive in components though, my budget is not unlimited, but I might be able to sell off some laptops.
Edit: My amp wouldn't mind the lower efficiency of the 2.5 way either, my volume dial would love it.
Edit2: Of cause I could just buy the cheap components for the sub crossover, and upgrade when I can afford it.
How do I select the crossover point, experiment and see?
Erg, but I do love my ol' GAMMA's, moving on from them with be a bitter sweet affair, I have had them over half of my life, my dad built them.
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Adda
Super Member
Well thanks for the help, I'll have to think this over.
Adda
Super Member
Well the conclusion is that in order to proceed, I need to have the Wavecor drivers in an appropriate box and the VLD ribbons measured.
But I don't know anyone who could do this, my dad knows someone who gave the impression he could, but it turned out he couldn't.
Lets see what happens.
But I don't know anyone who could do this, my dad knows someone who gave the impression he could, but it turned out he couldn't.
Lets see what happens.
Adda
Super Member
The goal if all goes well, will be to use my 30 liter boxes, fill them with tons of wool, sure wool makes the box act as if it where bigger, but there must be limits as to how much wool you can stuff in to a box, and not make it act smaller.
Lots of dampening material should make the box acoustically dead, even though it's not made of concrete.
I hope I can leave it as a sealed box, I want these speakers to be so fast it's ridiculous, bass reflex is supposed to be a bit slow.
I might have to use BR though, if I can't get enough bass otherwise.
It will be 2.5 way, one Wavecor WF152BD02 will fill out the gap in the bass region of the other, a nice little trick to make small speakers produce a plenty of bass.
I'll then pair that with the GAMMA VLD-12's, preferably crossing them at 3500Hz, with as steep a crossover I can get away with, without causing phase errors.
The VLD's will be mounted on top of the boxes for easy access and to avoid interference from the woofers.
I'll probably keep the crossovers external, I donno where to put them, maybe they could be hidden in all the wool inside the boxes.
I think a suitable name for these would be "GammaWave"
Edit: I think I'll experiment with the VLD's without the horn, if they can go low enough without it, and play loud enough, I might not have to pad them down to match the WaveCor drivers efficiency.
Lots of dampening material should make the box acoustically dead, even though it's not made of concrete.
I hope I can leave it as a sealed box, I want these speakers to be so fast it's ridiculous, bass reflex is supposed to be a bit slow.
I might have to use BR though, if I can't get enough bass otherwise.
It will be 2.5 way, one Wavecor WF152BD02 will fill out the gap in the bass region of the other, a nice little trick to make small speakers produce a plenty of bass.
I'll then pair that with the GAMMA VLD-12's, preferably crossing them at 3500Hz, with as steep a crossover I can get away with, without causing phase errors.
The VLD's will be mounted on top of the boxes for easy access and to avoid interference from the woofers.
I'll probably keep the crossovers external, I donno where to put them, maybe they could be hidden in all the wool inside the boxes.
I think a suitable name for these would be "GammaWave"
Edit: I think I'll experiment with the VLD's without the horn, if they can go low enough without it, and play loud enough, I might not have to pad them down to match the WaveCor drivers efficiency.
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Adda
Super Member
First VLD w/o horn test completed, they are flat from 3000Hz onwards as with the horn, but they have lost a lot of efficiency.
Horizontal dispersion seems very good, even at high frequencies, vertically they are a bit of a joke, just terrible, but not a problem proper placement can't beat.
Now how about power handling...
They seem fine without the horn.
Horizontal dispersion seems very good, even at high frequencies, vertically they are a bit of a joke, just terrible, but not a problem proper placement can't beat.
Now how about power handling...
They seem fine without the horn.
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Adda
Super Member
I thought it was time for an update.
I think this project has turned out better then I thought last time I updated this thread.
These speakers are not without some rather obvious flaws, like a rather undefined midrange, not very detailed, and the upper midrange is just not very good at all.
This becomes very apparent when playing loud, the upper mids become piercing, I think it's because the great big 12" cone gets too stressed and starts breaking up.
At low to moderate volumes they sound very good though, effortless, tuneful, rich, with the fantastic ribbon treble range.
Like the GAMMA 50's, they sound very big and spacious, but without the squeaky midrange, that has been traded for mediocre midrange detail, and limited SPL.
I have been experimenting with different horn positions, I put the horns on top of the box, in a vertical orientation, on a piece of rug, so that vibrations from the box doesn't interfere with the ribbons.
I have tried putting them on top of some cardboard boxes, to get the horns out of the way of the woofers, but that made them integrate poorly.
It seems that the closer the two drivers are to one another, the better, even though the horn is almost in the way of the woofer.
I have tried using the VLD's with the KEF B110's using the crossover I made, the B110 is NOT a 96dB/w driver, not by a long shot, more like 86dB/w.
The VLD's are more efficient even without the horn, and I find that the B110's sound strained, like they are working really hard to do what they do.
They are detailed and clear, but their struggle and tiny sound made me miss the BK3013A's quickly.
Based on what I have learned, I'm yet again rethinking what to do next, and I think I'll be looking to Beyma, they make some nice 10-12" woofers with neodymium magnets and wide frequency ranges, I think I'll pair one of those with my ribbons.
The Beyma 12MW/Nd looks compelling.
http://www.cadaudio.dk/12mwnde.PDF
I think this project has turned out better then I thought last time I updated this thread.
These speakers are not without some rather obvious flaws, like a rather undefined midrange, not very detailed, and the upper midrange is just not very good at all.
This becomes very apparent when playing loud, the upper mids become piercing, I think it's because the great big 12" cone gets too stressed and starts breaking up.
At low to moderate volumes they sound very good though, effortless, tuneful, rich, with the fantastic ribbon treble range.
Like the GAMMA 50's, they sound very big and spacious, but without the squeaky midrange, that has been traded for mediocre midrange detail, and limited SPL.
I have been experimenting with different horn positions, I put the horns on top of the box, in a vertical orientation, on a piece of rug, so that vibrations from the box doesn't interfere with the ribbons.
I have tried putting them on top of some cardboard boxes, to get the horns out of the way of the woofers, but that made them integrate poorly.
It seems that the closer the two drivers are to one another, the better, even though the horn is almost in the way of the woofer.
I have tried using the VLD's with the KEF B110's using the crossover I made, the B110 is NOT a 96dB/w driver, not by a long shot, more like 86dB/w.
The VLD's are more efficient even without the horn, and I find that the B110's sound strained, like they are working really hard to do what they do.
They are detailed and clear, but their struggle and tiny sound made me miss the BK3013A's quickly.
Based on what I have learned, I'm yet again rethinking what to do next, and I think I'll be looking to Beyma, they make some nice 10-12" woofers with neodymium magnets and wide frequency ranges, I think I'll pair one of those with my ribbons.
The Beyma 12MW/Nd looks compelling.
http://www.cadaudio.dk/12mwnde.PDF
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Adda
Super Member
I think I'll go for these, in my 30 liter box BR, if there is room, but I think there is.
http://profesional.beyma.com/ingles/pdf/10LW30N.pdf
They look they they where made for my needs, hope I can afford them soon.
http://profesional.beyma.com/ingles/pdf/10LW30N.pdf
They look they they where made for my needs, hope I can afford them soon.
Adda
Super Member
I found a problem with one of my GAMMA BK3013A woofers, when pushing the cone, it made a slight scraping noise, it did feel like it could not move as freely as the other woofer.
I knew instantly what this problem was, the magnet was not properly centered around the voice coil.
Luckily the simple design of these drivers allows me to remove the magnet form the woofer, so I did, and adjusted it till the rubbing was gone, and tightened it down.
I knew one of my speakers where more peaky then the other, I contributed it to variation in component values, placement of that speaker (closer to a corner) and wear and tear on the ancient woofers.
But it seems it was the rubbing, I still get breakup at high volumes, but not as bad, but I got a bunch of extra midrange detail.
Happy days
I knew instantly what this problem was, the magnet was not properly centered around the voice coil.
Luckily the simple design of these drivers allows me to remove the magnet form the woofer, so I did, and adjusted it till the rubbing was gone, and tightened it down.
I knew one of my speakers where more peaky then the other, I contributed it to variation in component values, placement of that speaker (closer to a corner) and wear and tear on the ancient woofers.
But it seems it was the rubbing, I still get breakup at high volumes, but not as bad, but I got a bunch of extra midrange detail.
Happy days