Any comments on the BMS 4538 compression driver?

I'm gearing up to start my next speakers project, a 2-way CD design.
So, I'm looking through the local retailers lists and the BMS4538 looks affordable and sweet but I'm aiming for a low crossover and all the sweeteness in the world won't make a difference if the driver isn't up to the task.
900Hz with a Seos-15 waveguide.

So, any comments on this little compression driver?
If all else fails I'll go with the DE250, this will be my reference.
 
So, I'm looking through the local retailers lists and the BMS4538 looks affordable and sweet but I'm aiming for a low crossover and all the sweeteness in the world won't make a difference if the driver isn't up to the task.
900Hz with a Seos-15 waveguide.
Looking at the published distortion of the BMS4538, it has more distortion around 900 Hz, but less above than the 4550.

I did extensive testing of the BMS 4550 and 4552, and you can listen to the results, and perhaps interpolate the difference you see in the graphs between them and the 4538.
Those two BMS drivers sounded quite similar, I would not expect the 4538 to sound much different.
If you like to listen loud, but are sensitive to distortion, I'd suggest no less than a 12 dB electrical crossover for these drivers at 900 Hz.

The “Full Monty” has been posted here:
http://www.diyaudio.com/forums/multi-way/212240-high-frequency-compression-driver-evaluation.html
A shorter version (only 3000 rather than 8000 words, and a lot less pictures) can be found here:
High Frequency Compression Driver Evaluation

The sound files in the soundforums.net posts do not have the low frequency portion of the music mixed in, listening to the HF horn alone makes it easier to hear the difference in sound quality and distortion between the drivers.

The recordings afford an insight in compression driver comparison (as far as I know) never undertaken before this study.

Hope you will enjoy the opportunity to compare the different driver’s sound without all the usual problems associated with A/B/C/D/E/F testing!

Art
 

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The fact that you believe that these drivers can be crossed successfully at 900Hz with a 2nd order crossover is great news. :)
I'll try to figure out a way to listen to the files on my current rig.

How would you compare it to the B&C DE250?
Better/Worse/just different or pretty much the same?
 
How would you compare it to the B&C DE250?
Better/Worse/just different or pretty much the same?
Have not heard the B&C DE250, and since B&C and BMS don't use the same horns, the charts don't make an easy comparison possible.

Whatever horn the B&C DE250 uses, the LF response looks to be similar to the BMS4550 on a CD90/75 horn, they both fall off at around 30 dB per octave below 800 Hz.
 
The fact that you believe that these drivers can be crossed successfully at 900Hz with a 2nd order crossover is great news.

How would you compare it to the B&C DE250?
Better/Worse/just different or pretty much the same?

Hi Markus,
Art is basing his 2nd order/900hz on the distortion graph.
BMS rates this driver with a 1.9khz crossover point.
I don't know if not meeting the power specs is the only drawback to crossing over lower, or if there are other factors.

The basic differences between BMS and B&C are that B&C will have a flatter frequency response, and BMS will have much better transient response.

Regarding transients. Art says that the 4550 and 4552 sound very similar to him. Indeed they have very similar frequency and distortion response. (Down to 1K, the 4552 throat opens up much faster and has higher distortion below 1K.) But to me the 4552 has better transient response, (see its higher flux density), and with the neo magnet has a more stable flux density. To me is sounds more precise.

In the 4550 vs. 4538, the 4550 has a higher flux density. I think that will translate into better sound quality in the mids. Again, better transient response. The 4538 has a smaller Voice Coil, VC, and will have better resolution on the high end, and go higher.

Regards, Jack
 
I guess there's no such thing as a free lunch.
Flat frequency response and good transient response are both valuable.
I can get the BMS for a $100/piece less than the B&C driver, perhaps you can understand why I'm interested in it's performance. :)

Still it doesn't matter if it's cheaper if it doesn't work in the design. It's always most economical to do it right the first time.
 
That driver looks to need about 9 db of midrange padding to get a semi-flat response so maybe 109 db/w/m at 10 watts - look at that HF distortion though and the top octave response :confused:
Midrange reduction won't change the low output potential which is limited by excursion, not power. The level in the 1200 Hz range is 117 dB,(read the 2 dB graph increments wrong) the level above is more. I don't get what your 109 dB reference is.

The top octave response is from 15,000 to 30,000 Hz, I can look at it but can't hear it ;^).
 
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Thanks, that is more than adequate. I have two Tannoy dual concentric pa 15"-drivers, and plan to replace the original 1" compression driver with a better one (better SQ). The driver used to be in a V15 enclosure.
What makes you think that the BMS 4538 will have "better SQ" than the driver that Tannoy used ?
Do you have EQ in your active crossover to compensate for the different driver response?
Do you have delay in your active crossover to compensate for the different driver depth/phase response?