Oh, and, from my simulations, a pair of SB34RNXL-8 in parallel can’t reach 120dB/1m anechoic- displacement limited below 300Hz and thermally limited above.
So please don't try to coax the magic smoke out of it by trying to measure 120dB/1m out of it... perhaps you have no factored in baffle losses...
So please don't try to coax the magic smoke out of it by trying to measure 120dB/1m out of it... perhaps you have no factored in baffle losses...
Ah bless you, so cool! I'm registering just to thank the site owner.
And bless Google Translate which lets me read it!
@head_unit : No need for google translator, there is an english translation on the site, see "en" button on the top right!
Thanks for all the condolence! 
The test signal WAS just 1s long and the 2nd driver did take it without problems - I still think it was a problem with the broken one. I did hundreds of these measurements and never destroyed a driver - but I destroy them sometimes when checking borders of capacity. Like the T25 tweeters - the only can take 10Vrms long term which is pretty common for 1" tweeters (ScanSpeak can take a little more, their metal membrane gets to 80°C!)
I can't show pics of the test cell or measurement setup but the speaker design is my copyright so I can tell a few words about that.
The aplication is to measure microphones with very high precision in a 2x2x2m big free field chamber. 16Hz to 60kHz at 94dBSpl in 0,5m was the old spec which I already built a speaker, now we expanded to 16Hz to 100kHz and some reserves in level at low and mid frequencies. That could mean up to 120dBSpl at 1kHz for short bursts. The chamber helps with roomgain, but there is also a bigger one at a different location which brings the former 2x20cm driver to it's limits.
Standards tell you should use a coax for measurement speakers but there are no coaxes with a) no narrow band chancellations on axis b) extend to 60-100kHz so I build D'Appolito to get at least symmetrical radiation.
Price of the material is not the main concern at this project ... working time is WAY more expensive. It must be reliable and with the best possible performance.
These SB34RNXL-8 are pretty cool. 2 of them have enough sensitivity and power to bring most 1" tweeters in trouble. But if you would need 120dB at 16Hz ... that's not enough and of course was never the plan. These test cells are not that good isolated at low frequencies and there are people around during the tests
The test signal WAS just 1s long and the 2nd driver did take it without problems - I still think it was a problem with the broken one. I did hundreds of these measurements and never destroyed a driver - but I destroy them sometimes when checking borders of capacity. Like the T25 tweeters - the only can take 10Vrms long term which is pretty common for 1" tweeters (ScanSpeak can take a little more, their metal membrane gets to 80°C!)
I can't show pics of the test cell or measurement setup but the speaker design is my copyright so I can tell a few words about that.
The aplication is to measure microphones with very high precision in a 2x2x2m big free field chamber. 16Hz to 60kHz at 94dBSpl in 0,5m was the old spec which I already built a speaker, now we expanded to 16Hz to 100kHz and some reserves in level at low and mid frequencies. That could mean up to 120dBSpl at 1kHz for short bursts. The chamber helps with roomgain, but there is also a bigger one at a different location which brings the former 2x20cm driver to it's limits.
Standards tell you should use a coax for measurement speakers but there are no coaxes with a) no narrow band chancellations on axis b) extend to 60-100kHz so I build D'Appolito to get at least symmetrical radiation.
Price of the material is not the main concern at this project ... working time is WAY more expensive. It must be reliable and with the best possible performance.
These SB34RNXL-8 are pretty cool. 2 of them have enough sensitivity and power to bring most 1" tweeters in trouble. But if you would need 120dB at 16Hz ... that's not enough and of course was never the plan. These test cells are not that good isolated at low frequencies and there are people around during the tests
You can't get free field conditions in ANY room for 16Hz. But you can do very precise measurements of pressure microphones.
When it's just following the books they wouldn't need me
1,44m. Fits perfecty, chamber has 50cm wedges.
There are a lot of small pressure chambers around for measurements (1/100 the size). But golden devices and specifications need to be measured in "freefield" at 50cm distance. You need to follow the regulations your customer demands if you want to sell.
(Like 3 days at 130dBSpl endurance test or 150/160dBSpl shock test - funny projects)
But now back again to speaker driver measurements?
(Like 3 days at 130dBSpl endurance test or 150/160dBSpl shock test - funny projects)
But now back again to speaker driver measurements?
You can when the room is EXTREMELY big
I am just a little confused why you would like to measure stuff?
Since the speaker works in its piston range, it would be much easier just to simulate.
@b_force I think @IamJF is just using the speaker as a source to measure/calibrate microphones that have extreme working ranges. However he has to know the source is up to the job first and the microphones need to be calibrated individually, something a simulation can’t do. As for the microphone there are a number of application where you may want to measure 160dB impulse noise accurately, I will leave that up to your imagination.
I got answer from Bliesma regarding the damaged driver. The voice coil was smashed - seems like 500Hz at 27V are mechanical to much ;-) With a crossover at 500Hz this would not have been a problem cause it would have been a few dB down already at 500. Thermal it wasn't a problem, as I thougt.
M74x-6 drivers have 1.2mm x-max...
Much like conventional tweeters, these domes are in sealed boxes, so SPL vs Vd is predictable.
Reference:
http://www.baudline.com/erik/bass/xmaxer.html
Much like conventional tweeters, these domes are in sealed boxes, so SPL vs Vd is predictable.
Reference:
http://www.baudline.com/erik/bass/xmaxer.html
As they are underhung voice coils I would have expected a higher Xdamage as 2,5mm. But maybe there was a tiny pop in addition with the start of the measurement signal? Seems like the ATC is at least more robust in this regard.
Nevertheless - when testing these extreme conditions failure can happen. Don't do this at home when you are on a tight budget
Therefore I wanted to report here about my abuse so nobody needs to repeat my brute force approach
Nevertheless - when testing these extreme conditions failure can happen. Don't do this at home when you are on a tight budget
Therefore I wanted to report here about my abuse so nobody needs to repeat my brute force approach
Given the unknowns perhaps it is safer to use a safety factor of 20 or 50%, like that taught in mechanical engineering.
Did Stanislav tell you, by any chance, what the power handling or x-limit was?
Bliesma's own webpage is a bit behind, there's no datasheet. So much work to do and not enough hours in the day...
It's not clearly defined on the datasheet hosted, thanks to @HiFiCompass
Did Stanislav tell you, by any chance, what the power handling or x-limit was?
Bliesma's own webpage is a bit behind, there's no datasheet. So much work to do and not enough hours in the day...
It's not clearly defined on the datasheet hosted, thanks to @HiFiCompass
Stas is very gracious and helpful in emails. However I'm under the impression that Bliesma is deliberately obfuscating the power handling capabilities of their M74 series of driver. It seems odd that although there are many established industry standards for determining power handling, Bliesma does not disclose a rating for their drive units. I believe they have working on their own technical paper on power handling, but have yet to release it.
It may be that the single suspension is causing problems during a such a large mechanical displacement, and together with the extremely tight gap tolerances, may have induced minor rocking modes that caused the coil to jam within the gap momentarily, (together with the huge motor force) leading to the former deformation. This is just sheer speculation and it may well be that the former did indeed hard bottom (although that would frankly indicate a rather poor design choice, to leave such a short headroom for overexcursion). However if it was a hard bottom, you would surely have heard an audible clack from both drivers as well?
It may be that the single suspension is causing problems during a such a large mechanical displacement, and together with the extremely tight gap tolerances, may have induced minor rocking modes that caused the coil to jam within the gap momentarily, (together with the huge motor force) leading to the former deformation. This is just sheer speculation and it may well be that the former did indeed hard bottom (although that would frankly indicate a rather poor design choice, to leave such a short headroom for overexcursion). However if it was a hard bottom, you would surely have heard an audible clack from both drivers as well?
Any idea guys for a silk tweeter 2000 hz XO ; > to 90dB/2.83V ; as detailled as the metal SB26CDC to challenge it, please ? Budget less than 250 euros/USD max the pair
MTM with 5" hard paper units (NE149W). I thougth also to the Bliesma T25S and the wave guided Morel CAT378/TW30A11 ? SS 2604/83000 ? small Illuminator twweter cans ?
Can be horned too but not sure it is worthing with 5" woofers ?!
Sligthy OT but still a question of measurements and sounding measurement and experience feedbacks. Coming from daily aluminium tweeter use I am looking for something detailled enough and blending fine with a detailled papaer cone at the level of a Satori paper driver.
MTM with 5" hard paper units (NE149W). I thougth also to the Bliesma T25S and the wave guided Morel CAT378/TW30A11 ? SS 2604/83000 ? small Illuminator twweter cans ?
Can be horned too but not sure it is worthing with 5" woofers ?!
Sligthy OT but still a question of measurements and sounding measurement and experience feedbacks. Coming from daily aluminium tweeter use I am looking for something detailled enough and blending fine with a detailled papaer cone at the level of a Satori paper driver.
