Question for What Hi Fi team re speakers

[Big Aura]

Posted this in the Magazine sub-forum, but think it got overlooked.

A question on the April issue : In your mid-price speaker test, you say that you get the best results with the B&W 685s if you place them a bit in front of a wall, as otherwise they can sound a tad boomy. Why so? I've got these speakers and have them about 7 inches off a wall and can't really re-locate without significant works, so was wondering why it's an issue.

Cheers

 

[Anonymous]

Also have the 685s since about a week ago and have similar space problems - have them about 10" from the wall and any further out I'd have to build a flyover! Did notice that when I put them nearer to the wall the bass did get a bit 'boomy' but where they are they sound like they should. They shouldn't boom - as they're front ported - but they do.

 

[Big Aura]

that's my view - to say a front porting speaker needs to be far from a rear wall seems as arbitrary as saying it needs to be in a room painted orange. WHFS&V please explain!?!

 

[Anonymous]

My understanding is that bass frequencies are omni-directional, ie radiate out 360 degrees, whereas higher frequencies are more directional. Hence even if the speakers are front-ported, they should still ideally be placed away from a back wall or side wall, but not as far away as rear-ported speakers.

 

[Big Aura]

Andrew - if that is the case, it might be a good feature to have in the magazine. Each month have a "How stuff works" in noddy terms. You could do speakers (I recall someone posted a link a few months back to how speakers work, but it was long and a bit techy), amplifiers, dvd, blu-ray, mains & conditioning (one for Trevor to ghostwrite??!). Etc.

 

[AEJim]

There are a few factors that cause bass-lift near a wall, omni-directionality of low frequencies is one, another is radiated sound from the cabinet itself, put your ear to the back of a speaker when it's playing and you'll hear quite a lot of noise! Even more so with rear ported speakers, quite a lot of the mid can make its way down the port tube - "muddying" the sound.

Cheaper speakers usually suffer most due to limited construction methods = more noise from cabinet, in anycase it's not just the low frequencies which are affected by this, if you put a speaker flush to a wall you'll get an approximate 6dB lift in the bass AND lose "air" and spaciousness from the high frequencies, flattening the soundstage considerably.

 

[the record spot]

Big Aura:that's my view - to say a front porting speaker needs to be far from a rear wall seems as arbitrary as saying it needs to be in a room painted orange. WHFS&V please explain!?!

I suppose it doesn't help me adding you'll find red, or even a nice rich purple will help things along nicely. Orange only works in sunny locations. Or if you listen to lots of reggae.

 

[Big Aura]

actually, the wall behind the speaker is purple. The missus calls it something else entirely. But as far as I can see it's "light purple".

 

[the record spot]

There's your problem then. This could be another thread entirely, but anything other than Dulux ruins my separation...

Seriously, placement's a killer depending on the room - we've got a bay window and that sometimes has an effect depending on the speaker. My previous Missions could boom a little (albeit front ported) whilst the current 752s being slightly leaner can sit further apart, and slightly closer to the rear wall. Bigger soundstage, and less fussy over positioning.