B&C DCX464 vs DCX 354

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Kevin Stelling

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Hi!
Which compression driver would be your choice above 1khz for a club installation? The dcx464 or the dcx354?
The driver hast to play over 3x 18Sound 15NTLW3500 (80-350Hz) and a 10" Midhorn JBL 2012 (350-1100Hz).
Crossover will be active FIR with Powersoft Amps. Horn for the Coax is a Limmer 250M.
 
Most large format compression drivers will play down to 1kHz. You do not need the lower frequency response capability (300Hz) of these coaxials as you already have this range covered by your midhorns.
 
Carl Klinkenborg said:
Most large format compression drivers will play down to 1kHz. You do not need the lower frequency response capability (300Hz) of these coaxials as you already have this range covered by your midhorns.
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yes, but most large compression drivers have problems in the upper frequency range. At the moment i use a Nd3st and i think at high levels, the crossover at 1200hz could be a bit higher for the 3“ driver. I want a driver which can play at 1200hz fully relaxed and at the same time can play flat to 16-18 khz without breakups.
 
Kevin Stelling said:
At the moment i use a Nd3st and i think at high levels, the crossover at 1200hz could be a bit higher for the 3“ driver. I want a driver which can play at 1200hz fully relaxed and at the same time can play flat to 16-18 khz without breakups.
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Kevin,

A constant directivity horn like the 90x50 Limmer 250M sensitivity will be around -5 to-10dB at 18kHz compared to 1000 Hz, regardless of the driver used. Chasing a "flat " response at the very high frequencies any driver can run out of headroom quickly due to air (atmospheric) absorption on top of constant directivity EQ compensation.
Limmer 250m.png
At 50 feet, in addition to the inverse distance loss, around 4 times more power (-6dB loss) is required to flatten the VHF at 18kHz compared to 1200Hz.
The problem gets worse at lower humidity levels than this example:
HF air absorption.png

Calculation method of absorption of sound by atmosphere air damping dissipation absorbtion high frequencies attenuation sound during propagation outdoors outdoor - sengpielaudio Sengpiel Berlin

Damping of air of high frequencies acoustics calculation of absorption of sound by the atmosphere outdoor absorbtion - Eberhard Sengpiel sengpielaudio
www.sengpielaudio.com www.sengpielaudio.com

Usually a 3" should have no problem being "fully relaxed" with a single 10" at 1200 Hz if using a 24dB/octave crossover, unless the low-mid horn is very narrow dispersion.
You say the crossover "will be" active FIR, what are you using now?
Have you verified the low mid and high horns are acoustically in phase through the crossover region?
What midhorn (350-1100Hz) is the JBL 2012 on?

Art
 

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Art Welter said:
Kevin,

A constant directivity horn like the 90x50 Limmer 250M sensitivity will be around -5 to-10dB at 18kHz compared to 1000 Hz, regardless of the driver used. Chasing a "flat " response at the very high frequencies any driver can run out of headroom quickly due to air (atmospheric) absorption on top of constant directivity EQ compensation.
View attachment 209851
At 50 feet, in addition to the inverse distance loss, around 4 times more power (-6dB loss) is required to flatten the VHF at 18kHz compared to 1200Hz.
The problem gets worse at lower humidity levels than this example:
View attachment 209850

Calculation method of absorption of sound by atmosphere air damping dissipation absorbtion high frequencies attenuation sound during propagation outdoors outdoor - sengpielaudio Sengpiel Berlin

Damping of air of high frequencies acoustics calculation of absorption of sound by the atmosphere outdoor absorbtion - Eberhard Sengpiel sengpielaudio
www.sengpielaudio.com www.sengpielaudio.com

Usually a 3" should have no problem being "fully relaxed" with a single 10" at 1200 Hz if using a 24dB/octave crossover, unless the low-mid horn is very narrow dispersion.
You say the crossover "will be" active FIR, what are you using now?
Have you verified the low mid and high horns are acoustically in phase through the crossover region?
What midhorn (350-1100Hz) is the JBL 2012 on?

Art
Click to expand...
Hi Art!,
The cabinet is a modified JBL VS3215-9. So the midhorn is 90x50. I use powersoft Amps with FIR filters above 1khz. Under 1khz i use IIR Filter. At the moment there is a 18S ND3ST on the Limmer250M. In my opinion it gets a little bit "aggressive" when the peak voltage reaches 25-30V.
 

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The JBL VS3215-9 mid horizontal dispersion falls to around 60 degrees above 1kHz, it's on axis sensitivity probably near equal to the HF horn driver. JBL specs the crossover points at 300-and 1.3kHz.
A 3" driver has about 4-5dB less output than a 4" as used in the stock VS3215-9 .

Since you have added more bottom end, reduced the bandwidth of the 10" mid, and are crossing the 3" lower than the 4", the "aggressive" sound of harmonic distortion could be bothersome at 30 volts- THD could be 50-100% at 10kHz at that level.

I have not yet heard the DCX464 or the DCX354, but based on the output potential of your system and how hard you drive the HF, and distortion tests of both drivers, I'd would suggest the DCX464 would be more "relaxed" sounding at those high levels.

That said, the sound of diffraction throats at high levels can arguably sound more "aggressive" than THD at high drive levels, so a driver upgrade alone may not be the cure.
 
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Art Welter said:
That said, the sound of diffraction throats at high levels can arguably sound more "aggressive" than THD at high drive levels, so a driver upgrade alone may not be the cure.
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Any suggestions for a horn with similar dimensions like the 250m or the original JBL 2381 biradial horn without diffraction throat and 90x50 dispersion?
 
The 18 Sound XR1496C 90x60 has a smoother throat, looks like it would fit, has decent polars, though may not be as sensitive being wider vertical dispersion.
The B&C ME90 80°x60° is similar.
 
Uwe Riemer said:
464 is the best driver I have used so far for high SPL/Bandwidth
354 is not the same in a smaller package, it sounds very different
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Any chance you could elaborate on this with some general subjective thoughts?

On paper they both look reasonably similar other than a different distortion profile which isn't always as clear cut to what people prefer/suits some applications better than others.

It seems very few people have heard both and been able to compare so any notes or onions on the context/configuration/music would be appreciated as i am considering purchasing one of the two at some point in hear future.
 
Rhys Edwards said:
Any chance you could elaborate on this with some general subjective thoughts?

On paper they both look reasonably similar other than a different distortion profile which isn't always as clear cut to what people prefer/suits some applications better than others.

It seems very few people have heard both and been able to compare so any notes or onions on the context/configuration/music would be appreciated as i am considering purchasing one of the two at some point in hear future.
Click to expand...
Since you asked so nicely:
The 354 HF sounds a little bit like the BMS, which is absolutely not my cup of tea

But the big difference which interestingly nobody seems to notice :
464 bands overlap, which makes passive crossover design pretty easy
354 bands underlap even without crossover
 
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DSP settings for the DCX 464 (or any other driver) depend on the horn used.
Few horns will support 300Hz, crossing above 500Hz opens up a large variety.
The mid section broadly peaks around 1.8kHz, the HF has fairly sharp dip between 5 and 6kHz.
As Uwe mentioned, the DCX 464 has a wide overlap, around an octave from 3-6kHz.
The "best" crossover point would vary with level, but around 4kHz is a good balance between mid/high headroom using a 24dB per octave "shape".
The HF section is smoother in the 3.2-5kHz range, so for lower SPL applications crossing a bit lower may be preferable.
 
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