I have been looking at two different 2" exit compression drivers. The Beyma SMC-60 and the P-Audio BM-D750. They only seemingly differ in that the SMC-60 has a polymer surround and the BM-D750 presumably is using the dome as its own surround. So there could be a difference in damping of dome breakup but P-Audio is supply very smoothed data. Big difference in price though, am I missing something?
https://www.beyma.com/speakers/Fichas_Tecnicas/000000718.PDF
http://www.paudiothailand.com/uploads/pdf/products/BM-D750.pdf
https://www.beyma.com/speakers/Fichas_Tecnicas/000000718.PDF
http://www.paudiothailand.com/uploads/pdf/products/BM-D750.pdf
90% going off what Dr Gedds has said about compression drivers here (but I think that the information is pretty accepted)
My understanding is that there is not a *massive* difference between 2 different but decently designed horn drivers (I have no idea about these two.)
Both drivers are supplied with mesurements taken from a horn, not from a plane wave tube. So you are really, most of what you are looking at is the horn, not the C.D. Beyma has put the compression driver on a constant directivity horn (looks kinda jbl esq) so its probably a better indicator of real world performance. The directivity of theTD-400 horn collapses in the last octave, so this is hiding the lack of output above 10k.
The P-Audio does not specify what horn it was made on, so its probably an exponential horn, they sound terrible but give even loading over the whole range.
If you had plane wave tube measurements, you could better evaluate each driver. As it stands, you probably need make sure that each driver would work well on whatever horn your going to use. If output levels are not crazy. imho i'd probably try the P audio, but i'd be tempted to go for a known great driver.
My understanding is that there is not a *massive* difference between 2 different but decently designed horn drivers (I have no idea about these two.)
Both drivers are supplied with mesurements taken from a horn, not from a plane wave tube. So you are really, most of what you are looking at is the horn, not the C.D. Beyma has put the compression driver on a constant directivity horn (looks kinda jbl esq) so its probably a better indicator of real world performance. The directivity of theTD-400 horn collapses in the last octave, so this is hiding the lack of output above 10k.
The P-Audio does not specify what horn it was made on, so its probably an exponential horn, they sound terrible but give even loading over the whole range.
If you had plane wave tube measurements, you could better evaluate each driver. As it stands, you probably need make sure that each driver would work well on whatever horn your going to use. If output levels are not crazy. imho i'd probably try the P audio, but i'd be tempted to go for a known great driver.
All depends on the final application. If you eq both of them flat, level match them, and take a listen at 90db, they'll be nearly identical in performance. If you turn up the power and/or lower the crossover point, then differences may begin to appear.
What output levels and bandwidth requirements do you need? Made in Spain vs. Thailand is the main difference in price.
China makes direct copies of B&C and others for a fraction of the price. Geddes mentioned that they're close in performance but quality control is lacking. P-Audio has been inconsistent in the past, not sure how they are now. Reports on the forum have been fairly positive in recent years.
What output levels and bandwidth requirements do you need? Made in Spain vs. Thailand is the main difference in price.
China makes direct copies of B&C and others for a fraction of the price. Geddes mentioned that they're close in performance but quality control is lacking. P-Audio has been inconsistent in the past, not sure how they are now. Reports on the forum have been fairly positive in recent years.
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It always surprises me that data sheets for speakers are so incomplete considering that putting a speaker into production must be a significant expense and you would hope that the relevent measurements to make a better data sheet would have been done during development. If I can sustain 120dB/1m that will keep up with the other components of the system when eq'ed flat to 20Hz. Worst case I can think of I would need 125dB/1m if I was not running the sub system flat. That's about 10-20W so within both drivers specs.
The Beyma is about 2x the price so I will go with the p-audio and return them if I have big differences between the drivers.
The Beyma is about 2x the price so I will go with the p-audio and return them if I have big differences between the drivers.
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Can someone please explain the frequency plots on both results as when I look at other frequency responses of different drivers the plots seem to be in multiples of 10 regards axis
I think this makes sense ie a vertical line @ 500/600/700/800/900/1000 etc but the graphs have way more vertical plots
I think this makes sense ie a vertical line @ 500/600/700/800/900/1000 etc but the graphs have way more vertical plots
10 to 100 Hz the extra lines are 5's ie: 10 15 20 25 etc
100 to 1000 Hz the extra lines are 50's ie: 100 150 200 250
1000 to 10000 the extra lines are 500's ie: 1000 1500 2000 2500
10000 to 20000 the extra line is 5000
I have a pair of the above P Audio drivers and they both match well when measured.
Rob.
You're welcome.. I get frustrated when trying to compare graphs with wildly differing spl scales (a speaker looks 'flat' and smooth on one graph and like a rollercoaster on the other)
Yeah, stupidly so. But there is plenty of 3rd party info for them:
Cask05 on this forum has used them, you can search for his comments.
Klipsch sold them (with a different sticker), so they have had quite a lot of Klipsch forum discussion
Tests: K-69-A driver on Edgar type wood Tractrix horn - Technical/Modifications - The Klipsch Audio Community
They seem pretty good for a budget driver.
P. Audio PH-4525 horn and BM-D750 (aka. K69) - Technical/Modifications - The Klipsch Audio Community
After years of trial and error I have come to the conclusion that it is mostly the diaphragm and surround material (and resonance control techniques) that give a compression driver it’s sound character in home applications
There is an extensive compression driver test here on this forum. A true apples to apples comparison. I'll see if I can find it.
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