Space From Walls

[NMMechEst]

I'm looking at having full range sound for every channel of 5.1 or at least 30Hz and up. I wanted 20-20Khz for every channel, but only muddy sounding Cerwin Vegas will give you that.

So here's my plan. Onkyo TXSR308 receiver, RF7's up front, RF82's in the back, where there is a 45 degree angle between me and the RF82's. My angle to the RF7 should be 30 degrees, such that my face to the wall distance is Dsin(60) and the distance from me to the side wall is Dcos(60). The room dimensions are 13x21x8 in feet. The system will use the length of the room such that the TV is in the center of a short side. The RF7's will be biased to the corners.

Here are my questions. Since the RF series have the port on the back of the speaker, how far from the wall should the speaker be? Would I be better off getting two pairs of F30's if the RF series have to be really far from the wall. I look at F30's because the Port is on the front.

[WMcD]

A few comments.

One of moderators answered such a question saying that if there is a rear port, the spacing should be no less than 1 port diameter (or so) from the wall. That is not much. It is simply the distance necessary so that the function of the port is not compromised.

I have my Forte II (big passive radiator) riight in a corner with the corners of the speakers almost touching the walls. I don't hear any problems. You can imagine the geometry. There is sort of a duct formed by the triangular cross-section.

In my view. We now know that the speaker with a back port has the potential for all placement except for being jammed up against a wall. But that doesn't tell us what is best, and doesn't tell us what is the best spot.

Please note that just about all suggestions for placement of surround speakers place them 90 degrees off axis (plus or minus a bit) from the listner and not behind. This "behind idea seems to be a hold-over from the quad sound era. And people see many surrond speakers in movie theaters, including he back wall.

I wonder whether the electronic set up is going to put 30 Hz into the surround speakers. Of course you have to check the manual.

Wm McD

[NMMechEst]

Ok. That adds some confidence. I was just afraid that they had to be at least 5 feet away. A buddy of mine has these gigantic Cerwin Vegas with 2 15" woofers, and they were flush with the wall. They sounded like car subwoofers until we moved them about three feet away from the wall. Then they just sounded like PA speakers that were all bass and no highs.

I'm siding with that pi/4 arrangement because on some of my games, they have a setting were you choose from the speakers being placed on an axis though both sohoulders, or on the 45-degree-behind-you placement.

Thanks!

[colterphoto1]

Gil, I think that advice came from me. When I worked in Tech Support I came up with an idea that a starting point for speaker-wall spacing might be the sum of the diameters of all rear-mounted ports or passive radiators. There are two ports on the RF7, indicating 8-10" or so as a starting point. I've heard of folks with their Refs some 2 feet from the front wall, whatever works for you I suppose.

My forte II's *(15" passives) are in corners and corner to speaker back is about 13", leaving 2" between rear edge of speaker and side wall. This feels right for me. I've not scooted them in increments and done room measurements but I'm sure it's possible to really fine tune the placement.

I like having speakers like LS and CW (also subs) near a corner but not pushed back into it, in fact find that having them non- equidistant from the front and side walls is often a pleasing arrangement. Currently my LS are symmetrical around my plasma screen, but not to the room. One is against the front wall, the other near a setback in the room but supported by a sidewall boundary. Works for me.

Michael

[colterphoto1]

Remember too, that sound is not a laser beam [8-|], it disperses into the room, reflects off boundaries, with some frequencies absorbed. If you can see into the horn you're pretty much close enough imho, but I keep it simple. Most loudspeakers are designed to create a sizeable large 'sweet spot' and sitting directly in the crosshairs is not necessary. Some guys put a LED [H] pointer taped to a T-square on top of their speakers to 'aim' them, trig is fun but not necessary. Some of us with Klipschorns find that we like the sound field better when sitting behind the absolute apex of arriving sound.

Besides, the cleaning lady will move your chair anywho. []

[Colin]

I’ve reviewed, even manually measured, a few loudspeakers

over the years. Not sure I can find my post or article, so I will simply

summarize what I remember. Depending on the room dimensions and modes, I found

that the mid-bass response of almost all speakers sounds better when placed

three to four feet away from front and side walls. Since creating mid-bass is

usually the task of the front speakers in a multi-channel system, I would certainly

place them away from the front and side corners.

http://www.enjoythemusic.com/magazine/equipment/0408/loudspeaker_roundup.htm