Not all is speculation - and no - its *not* only a long term phenomena (like many people think) - there is also some calculation, simulation and measurements I've done as an outspin of a discussion elsewhere here some time ago:
Have a look - its fairly easy to read and understand...
Audio and Loudspeaker Design Guide Lines
as PDF:
http://members.aon.at/kinotechnik/d...wer_compression/thermal_power_compression.pdf
and possibly also here :
Audio and Loudspeaker Design Guide Lines
Michael
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My 21" Beyma reaches Xmax at 25 Hz with approx 400 W power input. Its AES power rating is 1600W, so I think we are within safe limits here? An other thing is that the sensitivity @ 100 Hz is almost 110 dB. When we consider this, 30 dB EQ dont look all that bad I think. But as I have said a couple of times - I need more headroom!
Before investing in an other pair of 21" woofers I would like to try an even larger H-baffle to see how much that helps.
Oh.. and of course: Happy new year to you all!
Before investing in an other pair of 21" woofers I would like to try an even larger H-baffle to see how much that helps.
Oh.. and of course: Happy new year to you all!
... following my own line of thinking outlined in the links above I admit that there actually is a lot of speculation regarding the *outcome* of thermal distortion.
This IMO is due to the circumstance that the effects of thermal distortion are to be considered in three pretty different time frames where TD affects :
- mere efficiency decrease after minutes ( power compression )
- SPL overshot in the 1-2 digit seconds range, affecting the perceptions of the rhythm of music
- outright waveform distortion due to thermal effects in the ms range
To speculate myself a little bit about the *perception* side of thermal distortion, I'd say its a matter very close to intermodulation distortion.
Meaning – for most people its obviously an "non-issue", especially for all those who love full range speakers.
I tend to not put down their perception as there is something going on with full range speakers that IMO extends well beyond the "on point source" explanation.
My guess here would be that both intermodulation distortion and thermal distortion add to the sense of " coherent sound" simply by the fact that there is no interruption of that specific distortion - seen over the full frequency spectrum - by any XO.
I assume that our ear / brain system is perfectly capable to detect such inconsistent distortion behaviour over the full frequency spectrum. It might even be of help to better "restore" sound events that actually are clouded for some reason.
Above means that even an absolute perfect XO done with an absolute perfect Coax-driver would suffer form a subjective degradation in sound coherence.
Myself loving active multi way speakers on sophisticated XO's – this is something sort of hard to digest....
Michael
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Just new housing. They're still the same ICEpower 125ASX2 amps I've used before, now in much nicer boxes.
classy finish
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Just received the Beyma 12G40 and with just a few hours of break in they already come up with a loooot of details... an excellent match to the high resolution of the AMT's IMO - though possibly not *directly* for crossing over to the tweeter as first dipole peak would be a little bit too low for this.
Will see how well I manage to integrate them in the end.
Michael
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An externally hosted image should be here but it was not working when we last tested it.
Virtually the same frequency response as the smaller H-baffle I had before, but 8 dB higher in level. 6 of those dB is because there are two drivers wired in parallell. The baffle is also 10 cm taller and deeper, and twice as wide. That's where the last 2 dB comes from I guess.
Some years ago I had two 18" in large bass-reflex boxes... they were a lot louder than this! However... its more than sufficient low bass now, can also reach 20 Hz easily.
The weakest part of the baffle is the top and bottom plate. They're not stiff at all, but I'm amazed at how little they actually vibrate. This is a prototype though, built from cheap 19 mm MDF. If I do a "production" version, it will probably be in birch ply that is stiffer than MDF.
The weakest part of the baffle is the top and bottom plate. They're not stiff at all, but I'm amazed at how little they actually vibrate. This is a prototype though, built from cheap 19 mm MDF. If I do a "production" version, it will probably be in birch ply that is stiffer than MDF.
Don't let Earl Geddes see this!
It is the living proof of his verdict that you end in a battle of material, if you really try to do dipoles right.
It's gorgeous!!
The longer I listen to the 12G40 the more I appreciate its outstanding quality!
In case you have 'em lying around Stig Erik, I really recommend to give it a try below the tiny Excels.
They possibly play with even "more fun" than the previous Beyma 12P1000nd you had. It would not surprise me if they outperform the three 8" Excels in your setup.
The 12G40 provide a quality of "directness" that is breathtaking
My current (test-) setup is the 12G40 below the 8" Jantzen below the AMT
Michael
In case you have 'em lying around Stig Erik, I really recommend to give it a try below the tiny Excels.
They possibly play with even "more fun" than the previous Beyma 12P1000nd you had. It would not surprise me if they outperform the three 8" Excels in your setup.
The 12G40 provide a quality of "directness" that is breathtaking
My current (test-) setup is the 12G40 below the 8" Jantzen below the AMT
Michael
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OK... here are some observations of the dual 21 H-baffles.
a) They are loud enough! More than sufficient for church organ, synthbass and other extreme stuff.
b) The baffles should probably be build a bit stiffer... easy to fix
c) I have -6 dB @ 16 Hz with 26 dB of EQ. A loooot of EQ, I know.
d) Eady to get 20-100 Hz +/- 1 dB without much more EQ than dipole compensation. That would be impossible with closed box woofers.
a) They are loud enough!
More than sufficient for church organ, synthbass and other extreme stuff.b) The baffles should probably be build a bit stiffer... easy to fix
c) I have -6 dB @ 16 Hz with 26 dB of EQ. A loooot of EQ, I know.
d) Eady to get 20-100 Hz +/- 1 dB without much more EQ than dipole compensation. That would be impossible with closed box woofers.
Michael - glad you liked the 12G40. I think its a great midbass driver, with better midrange than the 12LX60 that Derek loves so much. I think the new 12P80nd looks promising, I will try a pair of those I think. I do like the 8" Excels a lot though... very clean sound, but a bit low efficiency.
Yeah the new Beyma neo drivers all look tempting.
I selected the 12G40 not for its comparatively low price or good looking distortion figures but for its >10 Qms (12LX60 could have been my next best choice).
There are not that many Pro speakers out there that can do *and* have somewhat smooth FR too.
Actually this was my test to see if there are audible benefits to gain compared to the Qms ~ 7 figure of the Peerless SLS combination with NEO horn.
Well - it turned out that Qms seems to be even more correlating to what I was looking for than expected.
Low distortion and relatively smooth FR (both not to complain about with the SLS) helps too of course.
So I tried it in the AMT setup and it harmonizes very, very well.
You already know I'm picky with friction.
Qms actually isn't exactly about friction though, as its - more or less - the whole bunch that does not fit into electric diaphragm control.
One part of that Qms nevertheless is related to friction and this part must be minimised too to get Qms high.
Bottom line : low Qms not necessarily indicates high friction but high Qms most certainly indicates low friction.
Michael
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With 2.1mh Le it surely doesn't look fast.
The 12PD80ND would be my current choice of Beyma 12" inchers.
If I didnt decide for 3x10" I would get two of those beasts ASAP.
Why is it that you look at Le in this context?
I mean - rising impedance is only affecting upper part of frequency response - and this particular FR is close to second to none with respect to its diameter.
Michael