I have tried solo vent-stuffing with and without foam phase plug. It increases the resonance. Everything that blocs the center venting air flow appears to do so (including the original dust cap). With the center completely without anything appears to be the best in this regard.
No I haven't.
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I tried some whizzer damping with foam stakes.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Some measurements...
On the left is the undamped, at the center is the version damped with 4 stakes and on the right is the version damped with 8 stakes. Measurement was taken close to the cone. Current driven was used un-equalized, so the Fs rings like hell.
Impulse responses (fairly good way to quickly look at the quantity/amplitude of the resonances, but one does not know the frequency of the delayed energy)
An externally hosted image should be here but it was not working when we last tested it.
CSD:
An externally hosted image should be here but it was not working when we last tested it.
It seems that coupling the whizzer too much to the bigger cone causes the whizzer also to radiate (to greater extent) the 2,5khz resonance. This hints that the 2,5khz resonance is bigger cone's cone resonance or something similar, maybe even the rear wave reflecting from the basket could cause something like this (that's what I'm hoping, the cure would be making the basket less reflective)? The whizzer's own resonances between 4kHz ... 6,5khz are reduced with more damping, but i don't find them irritating from the beginning.
The key is to find a balance, with the stakes I think it's the 4 staked version. Hf sounds less confused with it, but the 2,5khz resonance is not boosted nearly at all. 4 stakes weight less than a gram.
In freq response the 4 stakes result only in slight hf reduction (measured 80 away from the cone).
An externally hosted image should be here but it was not working when we last tested it.
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Holy shite, making the basket's feet of 12LTA non-reflective with ~2cm thick sound absorbing mat resulted in massive reduction delayed energy at ~4khz. The 2,5kHz resonance was also reduced a bit, the initial 15-20dB dying is faster.
Measured ~80cm away from the cone, 4ms window, on the right is the damped feet (obviously).
Never imagined effect of this magnitude. Absorbing the rear wave reflections seems to be very important with this driver.
I will propably go with absorptive mat on the inside and 4mm thick bitumen on the outside of the legs (+ back of the magnet too maybe).
Measured ~80cm away from the cone, 4ms window, on the right is the damped feet (obviously).
An externally hosted image should be here but it was not working when we last tested it.
Never imagined effect of this magnitude. Absorbing the rear wave reflections seems to be very important with this driver.
I will propably go with absorptive mat on the inside and 4mm thick bitumen on the outside of the legs (+ back of the magnet too maybe).
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Interesting! I knew that it made a huge difference with smaller drivers, but assumed that any basket damping on a 12" would show up lower down where it typically benefits the response overall, at least that's been the case with Altec and similar prosound wide BW drivers I've experimented on. Ditto damping the magnet assy., but with this driver you have me wondering about this, and some other tweaks, normally only considered worthwhile on smaller drivers.
GM
GM
Here the changes in FR with the feet damping, blue is with the damping:
It definitely affects in the problem band, difference in the ~300hz is also interesting.
I really want to see the results after I have damped the backside thoroughly, including the spider's "cup" fully (the area between the edge of the spider and the basket) and the magnet.
Found some very nice 30mm thick daping mat that weights a ton and is supposed to damp ~40dB wide range. Don't have to use bitumen with that. It seems that this mod is so effective that one should not take short cut on the damping material's properties = get mucho wide range absorption and weight/inert material to damp possible structural resonances.
An externally hosted image should be here but it was not working when we last tested it.
It definitely affects in the problem band, difference in the ~300hz is also interesting.
I really want to see the results after I have damped the backside thoroughly, including the spider's "cup" fully (the area between the edge of the spider and the basket) and the magnet.
Found some very nice 30mm thick daping mat that weights a ton and is supposed to damp ~40dB wide range. Don't have to use bitumen with that. It seems that this mod is so effective that one should not take short cut on the damping material's properties = get mucho wide range absorption and weight/inert material to damp possible structural resonances.
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You mean as the whizzer dampers? I'm not familiar with that material. For whizzer damping every lossy and light weight material will propably cut it. The material does not have to have high density. Different materials result in different optimal amount of damping, thats why I would fine-tune with measurements (in addtiotion to listening) if possible, to see the effects in time-domain and delayed energy.
For the basket absorption/damping I would get near the best and heaviest damping material available because the difference was so big. For example polyester wool and other regular speaker box damping materials are too low density imo.
For the basket absorption/damping I would get near the best and heaviest damping material available because the difference was so big. For example polyester wool and other regular speaker box damping materials are too low density imo.
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I used this kind of absorption mat:
It weights almost 4 times more than the absorption mat I used yesterday in testing. Damped the basket very well. I can start testing them in the evening after the glue has been completely dried. I think won't be glueing the absorption mat to the back of the magnet. Instead I bought some foam pipe to give slight damping and edge rounding at the basket/magnet interface.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
It weights almost 4 times more than the absorption mat I used yesterday in testing. Damped the basket very well. I can start testing them in the evening after the glue has been completely dried. I think won't be glueing the absorption mat to the back of the magnet. Instead I bought some foam pipe to give slight damping and edge rounding at the basket/magnet interface.
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That's some serious damping, looks expensive.
Thick felt or jute carpet pad can be glued on and still work well, though for drivers I don't want to 'deface', I just tie-wrap dense open cell sheet foam to create a tube sleeve and for the magnet I extend it somewhat behind and cram some scrap in the tail end.
GM
Thick felt or jute carpet pad can be glued on and still work well, though for drivers I don't want to 'deface', I just tie-wrap dense open cell sheet foam to create a tube sleeve and for the magnet I extend it somewhat behind and cram some scrap in the tail end.
GM
The glue I used (construction glue used to attach acoustic panels and similar porous stuff to the walls) can be taken off from the powder coating with a finger nail if one want's to revert the modification without leaving a trace. Although one has to really try, they definitely won't come off by accident.
Tried also PVA and universal glue, but they are not made for glueing porous surface like acoustic mat, they go in the mat and it might lose some of it's damping. They also came off from the powder coating like a peel.
Yep it was quite expensive (30 euros 100cm x 50cm x 3cm piece) but I think it's not a bad investment. It's enought to damp all 12LTA's I will ever own, or at least 4-5 pairs. Have been thinking to build a curved dipole line arrays out of them, I like this driver so much. 5-7pcs 12LTAs per side might be quite something.
Tried also PVA and universal glue, but they are not made for glueing porous surface like acoustic mat, they go in the mat and it might lose some of it's damping. They also came off from the powder coating like a peel.
Yep it was quite expensive (30 euros 100cm x 50cm x 3cm piece) but I think it's not a bad investment. It's enought to damp all 12LTA's I will ever own, or at least 4-5 pairs. Have been thinking to build a curved dipole line arrays out of them, I like this driver so much. 5-7pcs 12LTAs per side might be quite something
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I have had good results using something like this
McMaster-Carr
They have different thicknesses and densities....
Damping the baskets on my 12LTAs did improve the sound in my OB set up....so did a crossover and a tweeter and a woofer ....And then ended up shelving them for a pair of these..
http://profesional.beyma.com/pdf/12MI100E.pdf
McMaster-Carr
They have different thicknesses and densities....
Damping the baskets on my 12LTAs did improve the sound in my OB set up....so did a crossover and a tweeter and a woofer ....And then ended up shelving them for a pair of these..
http://profesional.beyma.com/pdf/12MI100E.pdf
Hah, the measured performance of this black mat was not as good as the performance of the test damping! The foam was not dense enough, the mass came from the rubber sheet that is between the foam layers, and it was actually reflecting the high frequencies and did not absorb them as good. I ended up cleaning the baskets and bought new damping material.
The test damping was made of 2cm thick re-bonded foam of 120kg/m3 density. For the final damping I bought 3cm thich re-bonded foam of same density. Improved things marginally over the test damping.
On the left is the test damping, on the right is the 3cm thick damping. The scale is reduced to 20dB to show the difference better.
Tomorrow is the listening day, finally.
Tried some cone edge damping with 4-12pcs of damping pieces with various positioning and the best result I got is here:
On the left is the CSD with the damping pieces.
Freq response (1/24 oct smoothing) with and without the edge dampers, blue is with the dampers (still current driven, hence the rising response):
This mod attacked the ~2,5kHz resonance finally
. Eight damping pieces weight approx. 2 grams. With the whizzer dampers total 3 grams. No loss in sensitivity to speak of, yet pretty massive change in the time domain behaviour if I would remove all of them.
I will make the damping scheme on the back side of the cone to hide it from they eye.
Phase plug still made the resonances worse, they definitely look nice but time domain performance suffers.
An externally hosted image should be here but it was not working when we last tested it.
On the left is the CSD with the damping pieces.
An externally hosted image should be here but it was not working when we last tested it.
Freq response (1/24 oct smoothing) with and without the edge dampers, blue is with the dampers (still current driven, hence the rising response):
An externally hosted image should be here but it was not working when we last tested it.
This mod attacked the ~2,5kHz resonance finally
. Eight damping pieces weight approx. 2 grams. With the whizzer dampers total 3 grams. No loss in sensitivity to speak of, yet pretty massive change in the time domain behaviour if I would remove all of them.I will make the damping scheme on the back side of the cone to hide it from they eye.
Phase plug still made the resonances worse, they definitely look nice but time domain performance suffers
.
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I have listened to them full range using current drive (1:9 voltage ratio), and I would say that the ringin at the Fs looks worse than it sounds. Works quite good in dipole, musical bass that also sounds quite fast, accurate and traceable. Some lower Fs drivers with higher Qms have not reacted so well, the basswent muddy without eq. Lower Qms high-ish Fs drivers usually react better in no-eq situation, due to lower impedance peak at the Fs.
One can smoothen the bass response with eq using current drive to reduce ringing, or use high pass to transition to a different woofer. Some resistance/aperiodic/damped TL type enclosure, that smoothens out the impedance peak at the Fs, might also work nicely with the current drive, lessen or even remove the need for eq.
One can smoothen the bass response with eq using current drive to reduce ringing, or use high pass to transition to a different woofer. Some resistance/aperiodic/damped TL type enclosure, that smoothens out the impedance peak at the Fs, might also work nicely with the current drive, lessen or even remove the need for eq.
I have listened to the 12LTA for couple hours now with the 8pcs edge damping pieces on the backside of the cone, there is clear improvement.
With the music material I listened, I could not detect any long decay resonances. The 2,5Khz region resonance could be heard before in some piano notes resonating and popping out a bit, that is now gone. Piano has nice clang, not underdamped nor overdamped. Some sreeching distortion quitars are now cleaner, and I'd say they now have right amount of "bite" to them what I have been used to with my electrostatic speakers. Many speakers do not reproduce the heavy metal distrotion quitar sounds right, nor the brass instruments or higher-pitch percussive instruments' transients. Usually they tend to sound too gentle, like compressed and/or non-time-coherent. 12LTA handles them all, I would compare them to my ESLs in many regard. It's almost hard to believe what I'm hearing from modded current driven 12LTA.
The paper cone's life-like and fun-to-listen-to sound signature is not altered from the whizzer damping pieces or cone edge damping pieces. Just more controlled resonances with the same sound signature.
With the music material I listened, I could not detect any long decay resonances. The 2,5Khz region resonance could be heard before in some piano notes resonating and popping out a bit, that is now gone. Piano has nice clang, not underdamped nor overdamped. Some sreeching distortion quitars are now cleaner, and I'd say they now have right amount of "bite" to them what I have been used to with my electrostatic speakers. Many speakers do not reproduce the heavy metal distrotion quitar sounds right, nor the brass instruments or higher-pitch percussive instruments' transients. Usually they tend to sound too gentle, like compressed and/or non-time-coherent. 12LTA handles them all, I would compare them to my ESLs in many regard. It's almost hard to believe what I'm hearing from modded current driven 12LTA.
The paper cone's life-like and fun-to-listen-to sound signature is not altered from the whizzer damping pieces or cone edge damping pieces. Just more controlled resonances with the same sound signature.
I'm not particularly interested in coating/douping the cone any way. Also one cannot simulate before and after effect in a reversible way and try to find the optimal damping scheme. In the edge damping test I found out that some damping styles made the CSD plot worse, or they reduced some resonances but generated some new ones at the same time. Shooting in the dark is not the way to go.
I have not seen quite many CDS plots before/after Enabling (if any, outside the Enable white paper). Are there some? Real world results speak for themselves.
I have not seen quite many CDS plots before/after Enabling (if any, outside the Enable white paper). Are there some? Real world results speak for themselves.
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