PORT DAMPING

Having been a regular reader of your magazine for more years than I care to admit, I hope you won't mind me writing with one small query?

In your November 2012 review of the Usher Dancer Mini-Two speakers you mentioned the use of acoustic foam to damp down port output and went on to say that a 50% fill of foam made a useful improvement in your test room.

I'm interested in understanding a little more about what you did here. I very much enjoy my Dancer Mini-Twos, particularly the full-scale reproduction that they afford, but there are times when, in my 5m x 5m room, a little less would be a bit more! Could you spare a moment to explain what is meant by the term acoustic foam and, also, what the 50% fill means in practice: does this relate to the area of port that is filled (or, conversely, left open) by the foam, or the depth of foam that is inserted into the port?

Looking forward to your reply.

Kind regards

James Batchelor

Loudspeaker foam port bungs. At top is a one piece bung with  a flat that

allows some air flow.

   Below is a roll of foam that allows air flow through the centre and wlil fit a slot port. These bungs damp down heavy bass,

and tighten it up.

Hi James. Yes, you have a problem there. A 5m (15ft) square room has a big resonant mode at 36Hz and the Mini-Two will excite this strongly because it delivers enormous LF energy.

   We half filled the port with acoustic foam. It was a 3cm thick slab of foam about 10in long, rolled up into a tube and put into the port. This narrows the port and provides some acoustic resistance. If that is insufficient then the port can be filled completely. You will hear the difference.

    You can get acoustic foam from Studio Spares (Google it, they are in North London).

Your room will boom because it is square. Try and put in the largest volume of acoustic foam possible.Studio Spares sell foam bass traps but you need a lot of them in big volume to absorb bass energy. I hope this helps. NK

MINI TWO TOO

I am a USA owner of the Usher Mini-Two loudspeakers, and note that the December issue of The Absolute Sound gives a similarly rave review...and also suggests the need to tighten the low bass. Query, then: exactly what did you do to plug the ports: material, dimensions, etc? 

M B Rosenberg

We half filled the port with acoustic foam. It was a 3cm slab of foam rolled up into a tube and put into the port. This narrows the port and provides some acoustic resistance. NK

As you suggested, I half filled the ports with rolled up acoustic foam and immediately heard the difference: tighter bass with no noticeable loss of low end response in my 24ft square listening room. Sure did help; thanks from across the pond! 

M B Rosenberg

Usher Dancer Mini Two produces strong bass and "a little less would be

a bit more!" says James Batchelor.

You’re more than welcome. It’s a gloriously simple way to fine tune any reflex loudspeaker. The only other (more expensive) trick is to fill the room with big, deep settees. Most cushions are foam filled and absorb bass energy, damping down room boom.You get a lovely comfortable lounge that sounds great too! And likely a happy wife. NK