Speakers VERY close to wall - Cork board useful?


Hi there,

I have a set of Klipsch RP-5's, that have a built in powered sub, and a rear facing port on the bottom of each tower. I have them in a small room (15'x13') with about 6' of separation. Considering the small room dimensions I have them pushed up against the wall because otherwise they'd be in the way. They are at least at a slight angle, but the port for the sub is still only about 4" off the wall. 

Would putting a square of cork board on the wall directly behind the port, cut out so its slightly larger than the port, make any positive difference compared to an ordinary sheetrock wall?  (The cork comes in a roll, so it is maybe 1/8" thick)

Any thoughts, additional suggestions on other common house-hold materials/geometry of cut/ etc, or comments would be appreciated! (other than "move the speakers away from wall" bc unfortunately that's not an option in this room)

:)
thanks!!!
hockey4496
I forgot to mention, in case it matters, that the room is carpeted. The speakers are on feet with spikes raised to a height of about 1" 
Contact http://gikacoustics.com/ and ask them for assistance. They have excellent acoustical products for affordable prices and will guide you as to the best solution as per your budget. They are experts. They will help. (No affiliation, just a very satisfied customer.)

Four inches should be plenty of clearance for the ports.  Even a bit less is still functionally fine - as the port gets closer to the wall the effective tuning frequency moves lower, which is the direction you'd want it to go. 

I assume that the controls for the subs should give you a fair amount of adjustability.  If the bass is too boomy and you can't fix it with the controls on the subs, you might try stuffing foam or a rolled-up towel into one or both of the ports. 

Duke

I've got about 3...4" from the wall and I use rug on the wall behind speakers. 
Thanks for the feedback guys. I'll look into gikacoustics, but in the mean time y'all don't think the cork would have any value with the current setup? 

Thankfully the sub output is adjustable via a dial on the back of the speaker. Overall the sound is great, especially with digital sources. What made me wonder about using cork though is when playing vinyl, some records sound perfect with the sub adjusted to say 25%, then on others 25% is loud/boomy and over shadows the treble/mids so I have to continually adjust both speakers up and down between different albums, and occasionally even between songs on the same record. 

Ive tried varying tracking forces on the tone arm and it doesn't have an effect on the bass issue described above so I thought maybe playing around with the surface of the wall could level out the acoutics a bit so the lows aren't so sporadically over powering
Hockey4496 - unfortunately cork is not the solution for this problem.

You would achieve better results from carpet or rug as suggested by Czairvey. Underlay under the carpet will also help.

An option that I have tried with great success it to redirect the direction of airflow from the port by installing a Perko Chromalex Cowl Vent over the port.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=11143&familyName=Perko+Chrom...

It worked very well in my case and made the speakers perform so much better across the entire bottom end - almost eliminating the muddiness and booming I had before..

Once installed, moving the speakers out just a couple more inches will improve things further.

Since you have carpet on the floor I would try pointing the vent downwards first.

Crazy Option ??? - maybe, but it worked

And - it's cheaper than new speakers :-)
Clever move, Willy. Sort of a "transmission line band aid". Cheers,
Spencer
Clever idea, I am give that a try. Thanks!

Willy Wonka’s cowl increased the effective port length and lowered the tuning frequency, which is the direction you want to go to compensate for the increased boundary reinforcement from placement near the wall.  I incorporate variable port tuning into most of my designs to deal with similar situations. 

It is also possible to lower the tuning frequency by decreasing the port’s cross-sectional area throughout its length, perhaps by inserting a smaller-diameter tube into the port. The smaller-diameter tube would be wrapped with tape as needed to get a good friction fit.

Williewonka - 
did you just slide the vent you bought into the speaker port? Or did you attach it in a particular way (modify speaker port, wrap tape to get correct diameter, etc.) I have some curved pvc tubing in the garage that may be about the right size that's could try without having to spend anymore $$ if it will work the same

thanks!
Hockey4496 - The cowl vent consists of two parts...
1. a plastic mount that is attached to the speaker with screws
- the opening just happened to be very close to the size of my port
2. the chromed cover which is than attached to part #1 via a latch mechanism and a single screw (If I recall correctly)

You could try the PVC pipe, lots of speakers use some kind of "plastic" for their ports.

Oooooh - I just had a vision of a speaker with dual chromed pipes on each side - just like a MAC truck - LOL

Seriously - I went with the cowl because it is metal and a much more solid solution - and I’m a big fan of solid :-)

It’s also looks very neat and tidy, hardly visible, even from the side and a little less "DIY" looking

Audiokinesis - thanks for the enlightenment - I had no idea why it worked - it just did.

QUESTION: Does the direction of the port have any effect or is it simply changing the length or diameter that causes the improvements ?

My reasoning for taking this particular approach ...
- I have observed that speakers that have rear firing ports are prone to placement issues
- whereas speakers with downward or front firing ports are better suited to closer placement to the wall behind them
- so firing the port downwards seemed like a logical choice

Cheers



Port bungs or rolled up socks...
If you want to enable your speakers to create a soundstage, you might try diffusion behind the mids & tweeters.
I had a similar situation and found there's really no substitute for breathing room for speakers unless they're built to work that way, especially if you're concerned with soundstageing and imaging.  So here's what I did -- when I wanted to listen critically I pulled the speakers a few feet into the room and pushed them back when done.  There are probably lots of aftermarket footer options that would let you easily slide the speakers back and forth without damaging the floor or significantly compromising sound quality.  Hope this helps and best of luck. 

I think all cork will do is eat up more valuable real estate back there. 

The vents look like a good idea.

I have relocated ports, cutting out frontal ports with a hole saw. Then sealed the rear cavities. I got the same sized ports from a parts supplier that have over hanging flanges for easy installation. Plus they hid the rough cuts and small chips created by the saw. The side mounted bass may work to an advantage as to not challenge the speaker's over all design much, or at all. More true if the internal cavity is symmetrical. But I'm not suggesting anyone go hacking into there factory speakers.  

Footers for easy movement sounds like a good option. But wont help for decoupling. For carpet footers made of rounded over walnut or other choice with a high count sandpaper polish. Even hit them with some wax. This made a 150 + lb audio rack a breeze to slide away from the wall to make adjustments or dust. Then when I had it placed on a hardwood surface I simply stuck felt pads under them.

Some bass traps in the L\R and top corner should further help the situation.   
Does anybody know of the speakers Designed to be set against the wall??? I know of just two: Naim SBL and DBL but they r discontinued ;-( Anything else?
NHT, but haven't heard from them in years. Still around? Cheers,
Spencer
Does anybody know of the speakers Designed to be set against the wall??? I know of just two: Naim SBL and DBL but they r discontinued ;-( Anything else?
Audio Note speakers (typically corner placement).
Von Schweikert VR speakers
Klipsch Cornwalls
Larsen models 4, 6, and 8

I also remember reading about an inexpensive ($500 or so) transmission line design with an angled top and upward firing drivers. The boxes only came in black. The name escapes me now though. I’m certain there are others. The Larsen 8 receives fairly high praise.

In addition to Yakbob's recommendations I'd add Sjofn The Clue.  I think they offer a free in-home trial.  BTW, don't pay any at attention to the Stereophile review of them.  It was completely botched and they should be ashamed of themselves.  Everyone who's heard them at shows (including me) has been amazed.  If you can afford a stacked pair do that.  Really incredible. 

Allison.
I've found that most speakers (those I've tried - e.g. like some Tannoy models) that have a port in the front will operate well in corners or against a wall.

Some speakers that have a port in the bottom will also work well, but some brands/model can sound a little muddy and confused if placed in the corners, so it's a bit more hit and miss

Regards...
I agree with soix about (the clue) speakers. I have a pair and they sound great. It does take time and effort to get them set up correctly, however once they are dialed in they are amazing and sound excellent in small rooms too.
+1 to all advice from Duke (audiokinesis)
+1 to stacked the Clue speakers.  They soundedfantastic when placed within an inch or two of the wall at the NY show a few years ago.