equalising a replacement amplifier for a B&W active sub

[PGS4038]

FIRST POST on this forum:
I have two ASW750 active subs, 13yrs old now and I think they're superb. Nevertheless the fitted amplifiers have both now failed twice! I've had enough and decided to replace the latest failure with a 500W Hypex FA501 fusion amplifier.
The original B&W ASW800 amp was equalised to provide a reasonably flat output in-room to below 20Hz from the relatively small enclosure with it's heavy duty driver so I know I'll have to imitate their filtering.

I have tried contacting B&W who as yet haven't bothered to acknowledge my mail. ( I was asking for thiele-small parameters for the driver, I can measure the box!)

My listening room is not an easy acoustic environment either, and there's not much I can do about that!

I've got REW software so I can see the results of my attempts to programme the DSP and to integrate the new amp into the system, and so far the results are promising but I'd like to know if anyone else has attempted a similar transplant to share experiences.

 

[KozmoNaut]

If you can't get the specs for driver, I think you're already doing the right thing. Measuring with REW to evaluate the changes you make is something you should be doing anyway, so while it may take you a bit longer, you'll presumably arrive at the same result in the end. Obviously start with no correction at all, so you have a decent baseline. The benefit here is that you can make it do what you want, not just what B&W thought was best, which will always be a compromise to work in as many room configurations as possible.

Since you're going to be using them in your room, measuring them in the room should be OK. If you can get the anechoic frequency response plot, another method could be to measure them outside in open air, and try to match the plot. That would be the best way to match the original EQ, if you can't get the specs from B&W.

 

[PGS4038]

Thanks for that, I was wondering about measuring it outdoors but as it weighs so much, and I'm now 68 I thought better of encouraging hospital visits! I need to transport it on a trolley anyway and it would be difficult to place it tight against an outside wall. I'll carry on with what I've already done but hopefully gaining knowledge as I go.

 

[KozmoNaut]

For the outside anechoic measurement, you would actually measure it in free air, some distance from any walls and such

I think it should be fine to just DSP it to the room, though you would probably have to redo it, if you move the sub sometime in the future.

 

[PGS4038]

I'd need a big crane to hoist it more than it's lowest achievable wavelength off the ground! Wouldn't against a wall or even in a corner outside be more accurate, as it's designed for indoor use, not as a PA!

 

[KozmoNaut]

Yes, ideally for anechoic measurement, it would have to be removed from any boundary effects. I do think a lot of companies measure their subs outside sitting on the ground, though.

If you are going to place it nearby any walls, you should just do it in the room anyway, since that's where you will be using them

When I was at B&O, speakers were measured both anechoically, and in a huge concrete room, with the speaker suspended in the middle and a microphone relatively close. The idea is that if you measure short pulses, you get the pure speaker response at the mic, before any room reverberation hits it.

 

[PGS4038]

I'll keep to in room measurements, I was originally just after some starter suggestions