Compression drivers Part III (News)

by Bert , Tuesday, February 28, 2006, 22:30 (6638 days ago)

Hi All,

I have spend some hours to get the BMS linear... work has been done at:

Midrange: correcting impedance peak at 3kHz and correcting the rising impedance after that to be able to add a 12dB filter to get rid of the high frequency noise (only 20dB down between 10-20kHz).

Tweeter: correcting a resonance at 8kHz (by means of an impedance correction network) and replaced the original filter for a 12dB version mirrored to the response of the filtered mid-range.

I needed a total of 18 parts to have this done! I will probably need 4 parts more because I want to try a 24dB Linkwitz filter so that I can connect the tweeter in phase with the midrange.

Below you can see the differences between the two versions. The red line is the BMS with original filter (tweeter connected out of phase as standard), the yellow line is the corrected version (also with the tweeter out of phase).

The scale between the vertical grey lines is 10dB and the graph is highly smoothened to recognize the main differences more clear. Measuring distance was 1m away from the mouth of the horn and 5 degrees off-axis, on-axis the high frequencies gradually rise above 15kHz with about 2dB and 10 degrees off-axis the high frequencies are falling gradually down with about 2dB above 15kHz.

The rest of the frequency respons remains the same so a good listening window of 20 degrees in total will be possible with these relative deep Oris 250/2C horns in combination with the BMS 4952ND compression drivers.

BTW, the low-end respons is limited with a 12dB high-pass filter crossing at 250Hz and the overall "efficiency" has dropped around 5dB.

How it sounds? I have no idea, that will be tested tomorrow if I can find the time. I bet it will sound less horny! :wink:

To be continued soon...

Bert

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BD-Design - Only the Best!

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