Behringer B1800D-PRO 10-30Hz low bass extension - diyAudio
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Old 26th July 2012, 02:55 PM   #1
AndreaT is offline AndreaT  Italy
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Location: Rio Saliceto (RE), Italy
Default Behringer B1800D-PRO 10-30Hz low bass extension

Hello Folks,
at the beginning of this year I purchased a PA Sub, the Behringer B1800D-PRO.

It is a 18" drive based bass-reflex unit.
It is equipped with a Class-D 1400W amplifier with an integrated X-over.

My objective when I purchased is was to conver the 10 to 50Hz frequency range.
For the purpuse I am also using a DSP to correct the native response of the B1800.

Measuring its "native" response, I detected two things:
1) The integrated Class-D ampli looks to be filtered with an HP at 20Hz with a 6 or 12dB/oct roll-off factor.
2) The Sub is PA "tuned" and its response quickly drop below 35Hz.

Any suggestion on how to modify the bass-reflex / enclosure to lower the "native" frequency response of this unit?

Anybody before me tried to modify the embedded Class-D ampli to get-rid of the 20Hz HP filter?

Many thanks in advance and kind regards,
Andrea
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Old 26th July 2012, 06:21 PM   #2
epa is offline epa  Netherlands
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you could make the br pipe longer and /or make a bigger box.
DO NOT take the hpf out or your driver wil probaply bottem out and be destroyed
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Old 26th July 2012, 09:02 PM   #3
tb46 is offline tb46  United States
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Hi AndreaT,

I'm with epa on this one. Additionally, you could measure the T/S parameters of the driver, and use a simulation program (e.g.: Hornresp) to evaluate what you could do with this driver. Then you can evaluate if there is any way to modify the enclosure to arrive at your desired response. By the way, 10Hz does not sound very realistic?

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Old 27th July 2012, 11:14 AM   #4
MaVo is offline MaVo  Germany
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I wonder, how loud would 10hz need to be to be recognisable?
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Old 27th July 2012, 01:46 PM   #5
AndreaT is offline AndreaT  Italy
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Join Date: Jul 2012
Location: Rio Saliceto (RE), Italy
Dear Friends,
thanks for your first replies.

Let me try to reply to you all here with these further details:
a) I already have the Sub working flat from 10Hz and then rolling down as expected (I actualy filtered it with a 42 dB/oct 35Hz LPF).
b) To get this "good & wanted" response I am "deeply" using the EQ capability of my DSP, the Thunea Frequency Allocator and Phase Arbitrator.
c) However, as my original post should figure-out, I am now really heavily adjusting (even up to 35 dB peak correction) a "native" response that is quite far-away the desired.
d) I can confirm that the flatness at 10Hz are not the "killing detail" making your system good or bad, but it mattersa a lot in the final sound stage inpact and in the realism of the entire "sound pressure".

So, based on your replyes, I will move-on with TB46 suggestion.

Let me know if you have more tips!

Many thanks and kind regards,
Andrea
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Old 27th July 2012, 04:42 PM   #6
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I would install a longer port, as is physically easy, and test/retune. That will lower the tuning frequency, but will lower the power handling, so look out for bottoming the driver.
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Old 27th July 2012, 04:44 PM   #7
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I bet that by pushing the sub so hard below it's tuning frequency, you are getting some major group delay and port noise.
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Old 27th July 2012, 05:54 PM   #8
AndreaT is offline AndreaT  Italy
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Join Date: Jul 2012
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Hi Turbodawg, yes doing that 10Hz EQ, I got group delay issues, but no port noise (so far).
I corrected the group delay by Thunea Phase Arbitrator delay adjustment.
I didn't hear any port noise, probably because I am using no more than the 20% of this PA Sub power.
It is a long excursion 1400W sub, I am not using more than 200W.
//Andrea
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Old 27th July 2012, 06:01 PM   #9
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Quote:
Originally Posted by AndreaT View Post
Hi Turbodawg, yes doing that 10Hz EQ, I got group delay issues, but no port noise (so far).
I corrected the group delay by Thunea Phase Arbitrator delay adjustment.
I didn't hear any port noise, probably because I am using no more than the 20% of this PA Sub power.
It is a long excursion 1400W sub, I am not using more than 200W.
//Andrea
Given what you say, I would see about lengthening the port quite a bit. Or consider removing the port entirely and sealing up the box, plus EQ and filter.
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Old 27th July 2012, 06:09 PM   #10
18Hurts is offline 18Hurts  United States
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Pack the port with socks, clothes or whatever

This will give it a simulated sealed box response, EQ it and listen. If you like it and the woofer does not make bad noises--it might work for you as a sealed box. It won't be as loud as the ported box but it is a PA woofer....those drivers tend not to have a ton of Xmax.

I built a subwoofer tuned to 22 Hz with two PA 15" woofers (Fs = 32Hz) loaded them push-pull isobaric in the stock PA box to cut the Vas in half and double the power handling. Since I had no T/S specs, I went with an 18" passive radiator and tuned it in place in the corner. My SPL meter was used to get the final tuning down which was around 22Hz.

If I move the sub, I can easily retune the passive radiator to wherever it ends up for the next location. No problems with peaks of 300 watts hitting the woofers (150W each) and I love the sound quality. Good luck!
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