Acoustic Treatment

PAC

Over the past year or so, I've been asked to help sort out so many systems (call it "system tweaking") but when I've visited the owner's premises, I've found that the systems are fine (bar the odd TT set up issue) and the real culprit to unsatisfactory sound has been poor room acoustics.

It always amazes me that enthusiasts are willing to spend a fortune on kit yet never think about the space they listen in!  The most extreme case was a guy who had £50K's worth of gear in a bare rectangular room, with just one chair and a coffee table...and a laminate floor.  He couldn't work out why his system sounded awful and was on the brink of giving up on hifi.  A few words to the wise about room treatment, a consignment of soft furnishings and clutter introduced into the room and you now couldn't wipe the smile off his face!

After giving it some thought, I will now be custom building very affordable high quality acoustic absorption panels to order.  I have spent the past few weeks mucking about with prototypes and have designed a small but perfectly formed series of panels.  These will be in the following sizes:

1200 by 750 by 100mm; 1200 by 600 by 100mm; 1200 by 600 by 50mm and 1000 by 300 by 100mm.

These will be pine framed panels containing dense glass wool insulation and covered in pukka acoustically transparent fabric (foam backed to provent insulation migration...yet still totally acoustically transparent).  You can choose from a wide variety of colours to suit your own decor and the fabric and insulation are fire retardant so safe for use in the home.

The thicker sizes have been designed as broadband absorbers and have a very high acoustic coefficient.  They make better bass traps than the lightweight foam wedges you see for sale and will look a darned site better in the home!

The larger panels can be free standing (optional feet supplied) or attached to walls and ceilings.  The 300mm panel is a bass trap for placement in corners and the air gap behind it means it doubles the efficiency (due to reflection and re-absorption of the reflected sound).

50mm panels are very effective above 500Hz, in fact being as effective as the 100mm panels.

These won't be appearing on the website for a little while, but I am starting to take orders for them now.  Other custom sizes can be constructed to suit your needs (price on application).

Prices for the large panels expected to be between £80 and £95 each and the bass traps expected to be much less.  Will firm this up in due course, but expect high quality and excellent VFM.  Not to be confused with cheaper Ebay alternatives wich dont use the same quality purpose designed and manufactured acoustic cloths, but more importantly, most of which are not fire retardant nor designed as true broadband absorbers.

Also happy to give anyone advice on treating their individual listening rooms.  Feel free to PM me.

uglymusic

Sounds very interesting Paul. Good luck with them.

Alan

Great idea Paul, good luck with this new branch. There seems to be a lot of interest in this on forums at the moment.

What method would you recommend for ascertaining what treatment should apply to a room - after all, its surely best to know what you are 'aiming' at?  For instance, a broadband absorber won't always fit the bill, will it? There must be ways of finding out what is needed for individual rooms.

PAC

Hi Alan

yes good point.  There is a general rule of thumb, backed up by advice I recently received from a studio engineer that ALL listening rooms can benefit from up to 20% reflective area coverage for increased accuracy, stereo image etc etc.  The rule regarding bass traps is that you can NEVER have too many, the ideal being that all corners should be treated.  As we live in our rooms and they're not studios, a compromise has to be met.  All listening spaces would benefit from a broadband panel behind the loudspeakers on the front wall, except for stand mounters that need to use the wall as bass reinforcement.  In that case, side walls (points of primary reflection) benefit from treatment, both close to the corner and again mid way between front wall and listener.  The same goes for the rear wall, where most spaces benefit from a broadband absorber there too.  For some, an additional panel on the ceiling mid way between listener and loudspeaker is another recommended place for a thin acoustic absorber (500Hz-20KHz).

A quick on line check against recommended acoustic treatment for studio spaces will confirm the above.

In my own room, I have treated the corners (bass traps), the area behind the speakers and the front wall in between the speakers and the improvement is significant.  There is a big reduction in bass boom and a better clarity to the imaging.  I plan to add bass traps to the other corners in time.  That is typically what most of us could get away with in rooms we have to live in.  For the cost of LESS than a gucci set of cables, you'll get biggest improvements to sound than buying the best cables!  

Our sources and amps these days are capable of vanishingly low distortion, so why to we accept huge values for phase shift and distortion from the loudspeaker/room interaction? It defeats the object of that high fidelity kit.  Simple room treatments can significantly lower in room distortion.

You can over do it though, so best to do a little at a time then evaluate instead of jumping in with two left feet and treating the whole room.  If overdone, the room will become acoustically dead, and SPL levels will decrease quite dramatically.

Brumjam

Interesting stuff Paul. Do the wall panels have to be proud of the wall to be effective? The reason I ask is that I'm planning a house extension, part of which will see my listening room stripped right back and reboarded and plastered. Therefore I have the opportunity to integrate some sort of panelling and reduce the visual impact as much as possible, potentially even making sections of the wall out of some form of acoustic panelling.

James

PAC

Hi James

the most effective way of mounting the panels is to leave them free standing within 25 to 100mm from the wall.  The idea being that what sound makes it through the panel is reflected back off the wall and re-absorbed back into the panel increasing it's effectiveness.  Best way for a living room is to use battens attached to the panels and fit the panels with screws/rawplugs up against the wall spaced out from the wall by the battens (behind the speakers).  That lowers the profile into the room and maximises panel efficiency. If you have the room, simply sit them on the feet provided as an optional extra which allows them to be placed within 100mm of the wall. The advantage of free standing units is that you can move them around with room changes or to tune the sound.