Compression drivers Part II (News)
by Bert 
, Wednesday, February 22, 2006, 21:35 (6644 days ago)
Hi all,
I finally received the first prototype Oris 250 for compression drivers!
The first thing I did was measure the low end response to see if my theory works out in practise. Guess what, it does! 
Without doing any power tests and based on primarely measurements the Oris 250/2C loads the BMS 4592ND midrange all the way down to 250Hz including a simple 12dB high-pass filter (below that it drops like a rock, as expected). The impedance having one pretty strong peak at resonance (350Hz, when not loaded) became pretty well dampened with the horn in place, only three relative small peaks were left and another strong impedance peak at 1000Hz (unloaded) dissapeared after connecting the driver to the Oris 250/2C horn. Great so far...
The tweeter extends very well up to 22kHz and does not drop too fast when measuring off-axis (at 10 degrees still pretty okay) but the crossover range didn't look too good to me...
Okay, time to listen to some music using the standard filter provided with the BMS driver.
Very dissapointing, this sounds like a horn as used on football fields! 
Next day:
I made a good adapter which already sounded better but still not good enough... Searching for the problem(s) causing this I'll started to work on the midrange only, removed the BMS low-pass filter and listened without the tweeter part of this coaxial compression driver.
Much better! Gone was most of the nasal and aNoying character, this starts to make some music! 
Up to date: Very promising but not yet good enough. I'll need to make my own filter and do many more experiments to see if I can make the BMS sing full-range in the future Oris 250/2C horns.
![[image]](images/uploaded/image91.jpg)
I'll keep you'll posted...
Bert
--
BD-Design - Only the Best!
Compression drivers Part II
Hi Bert,
Thanks for the information. It sounds very interesting indeed! I know that the BMS 4592 ND comes in an 8 Ohm version and in an 16 Ohm version. May I ask which one you are using? Thanks!
Regards
Peter
Compression drivers Part II
by Bert , Thursday, February 23, 2006, 21:56 (6643 days ago) @ Peter K
Hi Peter,
Thanks for the information. It sounds very interesting indeed! I know that
the BMS 4592 ND comes in an 8 Ohm version and in an 16 Ohm version. May I
ask which one you are using? Thanks!
At this moment I have the 8 ohm version but I will try the 16 ohm version later (by replacing the diaphragms) if the 8ohm version is going to be a success.
Ciao,
Bert
--
BD-Design - Only the Best!
Compression drivers Part II
by Johannes , Friday, February 24, 2006, 10:50 (6643 days ago) @ Bert
Hi Bert,
There is a guy here in Germany, who did a very good job in finding a filter/crossover for the BMS Driver. Maybe this helps a bit.
Here is the link to the german forum go to "Hörner" an look for Weichenupdate für BMS4590/JABO KH50. The horn he uses is an different Type, but the shape is a Tracktrixcurve as well.
Compression drivers Part II
by Bert , Friday, February 24, 2006, 18:50 (6642 days ago) @ Johannes
Hi Johannes,
Here is the link to the german forum go to
"Hörner" an look for Weichenupdate für BMS4590/JABO KH50. The horn he uses
is an different Type, but the shape is a Tracktrixcurve as well.
Thanks for the link but that does not cure the real problem...
Basically the driver is not designed well enough, there is a huge gap between the high and the midrange simply because the midrange driver is not going high enough, there is no overlap between the two drivers. Even without any filter there is already a 6dB dip at 5kHz, connecting the standard filter reduces the output of the high frequencies (on their lower end) making it more balanced in the higher frequencies but adds ripples in the midrange.
Also, the whole midrange remains too strong (> 3dB) and needs to be EQ-ed.
With a digital crossover and EQ-ing the higher midrange makes it very easy to create a balanced sound but that is not someting I want to do...
Now that I have found the problems does give me a rough idea what to do next though...
Bert
--
BD-Design - Only the Best!
Compression drivers Part II
Hi Bert,
You wrote:
Now that I have found the problems does give me a rough idea what to do
next though...
This is almost like a criminal novel:-)
Will you reveal what this next step in going to be? Thanks!
Regards
Peter
Compression drivers Part II
by Bert , Friday, February 24, 2006, 22:51 (6642 days ago) @ Peter K
Hi Peter,
This is almost like a criminal novel:-)
Exiting isn't it!
Will you reveal what this next step in going to be? Thanks!
I'll need to think about how to solve this but on the other hand, if a driver needs so much work wouldn't it be better to find something else...?
I won't give up on this driver so soon though, no worries!
Ciao,
Bert
--
BD-Design - Only the Best!