The speakers are 7 Pi's and the room is 17.5 x 12.2 x 8.5 (LWH)

To be honest I didn't spend a great deal of time on this (to boring when there's music to listen to) so may have to revisit the exercise again sometime.

Paul W.

I'm going to put in another passive resonator to target the 130's, but would placing a sub between the two 7 Pi's help with the cancellation effect or would that just add to my boosted room mode problems?

For sub duties I have a little active KEF unit to play with so I guess I should try it out. I also still have the spare Omega Pro 15 that I rejected due to cosmetic damage and the supplier didn't want back - would this be useful for making a sub and if so any tips regarding design parameters?

Paul W.

The Omega 15 can be used in cabinets from 2.0ft3 to 5.0ft3 tuned to 40Hz. It works great in a four π cabinet, so you could make one of those and place it between the speakers you have now. However, I think for a dedicated subwoofer, I'd prefer it in a larger box than this. You can go as large as 8.0ft3, tuning a little lower to 30Hz, and get a nice EBS alignment. That will give deeper extension and will blend nicely with the bass bins you already have.

But I do have that Omega Pro 15 sitting there doing nothing, and enough materials, so for the price of a small plate amp.....

OK, more things to investigate, no idea what EBS alignment is but will do in the next hour or so! However, to shorten the process in getting some guidance, do you know of any sites/forums that could aid me in the designs, remember total non-techie here (just handy with a saw and soldering iron) rather than continually asking here about non-Pi stuff.

Paul W.

Or would it be better to upsize the basic 4 Pi cab by 80%? I have to say I'm not really into this "design it yourself starting from scratch" stuff and am always happier to use someone else's (who at least knows what they are doing) tried and tested design

Paul W.

To tune the box, size the port accoring to the Helmholtz formula below. Make port area at least 20in2.

As, over the last few days I've decided on the final position of the foam bass traps and the panel resonator in the room I though I'd take some more measurements but just for the bass below 255Hz as this seems to be the element that's giving me most concern - so out with the tripod, meter and in with the ear plugs!

I'm constantly surprised by how ragged the output seems to be for something that sounds so good, though please bear in mind I've no specialist measurement kit just the good old radio Shack SPL meter. The bass output has been sounding very much better since the treatment was introduced and this is much smother than when first measured and obviously the scale makes the plot look quite dramatic.

Anyway the most dominant (+18db) room mode in the 130's (Hz) is now gone and next I'll tackle the one covering the 90's, also the major dip I had at about 45Hz seam to now be two dips either side, but I was much more careful with the measurements this time so it could have been an error previously.

Going to have a play with my little KEF sub over the next few weeks and see how this changes the output, before going for a bigger sub build with the Omega Pro 15.

Paul W.

:-0