OB bass equalisation for boxed sub's.

[ashok]

OB subs roll of at 6 db /octave below the resonance frequency of the driver. This is compensated for in the crossover with a pole and zero set to some frequency which will give a flat response in the desired band. The response could also just have a single pole set a very low frequency providing a flat bass response and roll off above the resonance frequency and not requiring an additional LPF.

Most applications do not do this as the resonant frequency is fairly low . But some designers have decided to do just this with a sealed sub woofer . They are www.bagend.com .
Roll off would have to be a second order unit and they must be using drivers with relatively higher resonance frequency. Must be their own drivers or made specially to their specs. High sensitivity, high resonance frequency, large Xmax etc.
Check out the literature on their web site. The commercial blurb about performance is misleading I think.

Has anyone heard these drivers ?

[zigzagflux]

I have, probably about 15 years ago. The marketing hype was centered around an integrator type of equalization. Was not very impressed, but to be fair I was getting the demo in a very large room.

[jbell]

Church with 10kw of macrotech, eaw cluster, and eaw delays, gl3200, xframe, a pair of bagend double 18's and their infra processor... (split subs, ugghhh) and timealign monitors. Worst sounding system my name is associated with... (I lost a lot of design arguments on that system.)

My 2c, 8hz is marketing, not musical.

[ashok]

I found something about the 8Hz rating. Apparently it very close mic'd and for short duration. They mentioned that upper frequencies were at about 1 watt or less ! That would mean plenty of bass boost. With 12db per octave this must be so.
They also recommend that the units be played with 'low levels' of low frequency 'noise' !
I wonder if this performance also uses room gain to help the performance. They used 'specialised' test equipment to measure this. Wonder what that was.

I guess rolling off HF at 12 db/octave is OK if the roll off starts very early. Depends on the driver also.

Interesting to see that it's been accepted very well commercially by some people. Must be working well in real life when it's set up critically. Some top honchos have given it the thumbs up for performance.
I was told that some studio over here has these speakers. Now I need to get round to listening to them here.
Very interesting !

Edit: Just saw jbells reply. Must be tough to get it to work well. Maybe only suitable for some applications. Yeah, the 8Hz performance here is meaningless.

[jbell]

Nah.. not difficult to get it to work well -- for PA use, it just doesn't work !!

It comes back to physics and that whole free lunch thing... Splitting a pair of double 18's with 'processing eq' to go to 8hz, guarantees you won't have any bass at all.

Loud, Low, Small, pick any 2... bagend's with infra processing are low and small.

From bagend's web site, looks like 97db is max acoustic output at 10hz, so 8hz must be less. Being extremely generous, and with +-3, 103db is all that church can get...

impressive.....


Frequency Response:
60 Hz to 250 Hz +/-3 dB
w/external Infra Integrator
8 Hz to 95 Hz +/-3 dB

Hi Pass Filter Frequency Switchable:
-6dB @ 8 Hz, @ 50 Hz, @ 95 Hz

Crossover Network:
Requires external INFRA Integrator
for 8 Hz Response

Maximum Acoustic Output:
Half Space @ 1 Meter
10 Hz - 97 dBSPL
20 Hz - 109 dBSPL
40 Hz - 121 dBSPL
80 Hz - 130 dBSPL