Speakers to close too wall?

From the manual:
"The speakers should be approximately 0.5m away from the back wall, and at least 0.5m away from any side walls. Figure 1a illustrates this arrangement."

http://www.bowers-wilkins.com/Downlo...CM1_manual.pdf

So long as there's at least one port diameter dimension between it and the wall there's no problem.

That depends on the baffle step compensation, if any, and crossover to the subs. 0.5m would result in an Allison Effect notch at 170Hz. Since that's well above the port radiation pass band it's not a problem where the port is concerned. But depending on BSC it could still impact the front wave reflection, especially as the baffle is further away from the wall, lowering the Allison Effect frequency for the front wave.

Oh okay... whatever the "effect".

Just going by the manufacturer's recommendation(s). That's why I provided a link to the manual which has other "fine tuning" suggestions.

The effect can result in a response notch as much as 24dB deep. IMO a manual that long should at least make mention of it.

http://www.aes.org/e-lib/browse.cfm?elib=2760
http://forums.musicplayer.com/ubbthr...&Number=693960

Are you serious? "That long"?
It's 3 1/2 pages in English.

Once you have that much space (a port diameter like Bill points out) so you're not effectively lengthening the port and changing its resonance it doesn't matter what side the ports are on (even at 100Hz sound waves are 3.4 meters long and wrap around anything you can fit in your living room like it wasn't there so what you hear doesn't depend on what direction the source is facing).

The big issue is that you need speakers voiced specifically for near-wall use. I'd buy in-wall speakers (with MDF enclosures) if I owned the place and on-wall speakers if I didn't instead of trying to make stand mounted speakers work in the location.

Both designs won't have the baffle step compensation needed for free standing use that yields too much bass near a room boundary and singers that sound like they have chest colds. This also allows them to be 3-6dB more sensitive for more headroom than the same drivers in a speaker built for free standing use. The in-wall designs also won't have an SBIR null from the front wall proximity (where the path length of the reflection is enough for the sound to make a 180 degree phase shift and cancel. Sound travels about 340 meters/second; so a speaker 20cm deep 10cm from the wall which puts the mid-bass .3 meters off the wall would have a notch at 340 / 4 / .3 = about 280Hz) or enclosure diffraction.

Sound stage depth will be less than you get with properly placed free-standing speakers but you're already giving that up by not keeping your speakers a healthy distance off the front wall (100 - 150cm is a nice number).

Okay... a few of you are focusing on the "rear port" issue. Here is the recommendation for the 685's.
"The speakers should be approximately 0.5m (20 in) away from the back
wall, and at least 0.5m (20 in) away from any side walls. Figure 1a illustrates this arrangement."

http://www.bowers-wilkins.com/Downlo...685_manual.pdf

So now what?

You look at the SPL chart, see if baffle step compensation has been applied. If so you want it far from the wall, if not you want it close to the wall. That applies irrespective of port location, though with a rear port you'd want to keep it at least a few inches away.

Do you have a reference/link to the SPL chart for the CM1's or 685's?
How does the OP see if baffle set compensation had been applied?

Again, as recommended in the manuals (if anyone read them) for each speaker, the "fine tuning" section describes suggestions for speaker placement and port tuning.

My speakers dont have ports insead they have a passive radiator. But they do need at least "6"-"12" from the wall to sound thier best, if i put them flush against the wall the soundstage gets muddy and the imaging goes flat.

Not all speakers (or rooms) are created equal.

Not trying to thread-jack... I hope this is on topic...

My 2 Primus 363's are front ported and I have them out 2 feet from the back walls (measured from the back of the speaker)...

Do I have them out too far...?

My Sub is rear ported, and I have it 20 inches from the back wall (measured from the back of the Sub)...

Do I have it out too far...?

Thanks for any info provided...

If it sounds good to you... you have everything positioned properly.

The distance matters but not because of the port and you would do better with in-wall or on-wall speakers.

That places the cancellation mode at 170 Hz, which is above the subwoofer passband, so no problem with the port. There could be with the front wave, depending how deep the cab is. The mains could have a null mode as well. It's the distance from the radiating plane to the wall that matters, be that the port or the baffle, or in the case of a rear port both. You do not want that distance 1/4 wavelength within the speaker pass band.

No. You can't really have them too far out unless it moves the speakers so close you're within the acoustic near field which ends about 3-10 source diameters from the speaker (8' to the listener is fine for most speakers). You could do with a few more feet out. Your SBIR null is strong and occurs at 140Hz.

If you pushed them out to 4'measured from the front baffles the SBIR null would be less, be at 70Hz, and be mitigated because over half the output was coming from the sub-woofer. 5' would be better with a 57Hz null half an octave into the sub-woofer's pass-band.

Thanks for all the information Bill and Drew...