What design attributes create a three dimensional image?

[SE-Raider]

I have listened lately to electrostats like the Martin Logans and read alot on the Pass Labs site about dipoles. Unfortunately my room application dictates placement close to a wall (6-12") which precludes these designs. OTOH, I have read many times in reviews of small MT's that they have exceptional imaging. What has experience taught you are the most important priorities to consider in order to achieve superior imaging (width and height as well as depth)? If the room prohibits dipoles, what would be the next best thing to accomplish a realistic soundstage?

[cjd]

Realistic soundstage?

Go to live events.

In seriousness, I think that keeping things to an equilateral triangle sure seems to work wonders for most systems - at least as a starting point.

Imaging and soundstage are not necessarily part of the same package - you can get imaging without much staging.

Beyond that I'm not sure - ability to resolve acoustic cues accurately, no smearing, no nasty non-source additions...

My suspicion is that any of Jon's work will do quite well in this regard. I know my 3-ways stage FAR better than they have a right to given being much too close to walls and an otherwise rather compromised setup. I think. Unless I've just managed to get super lucky and things worked out magically for me. I don't know if using a more idealized box has anythign to do with it, but my cheap(er) MTM's seem to do quite a job of it when set up well - the designs I've given more direct side by side AB testing with were all more constrained and all had box size dictated by something other than driver parameters (I believe - obviously hard to tell without knowing the params of the drivers).

So, in a nutshell, I have no idea at all. But it sure is fun to blather on about, especially because I don't look for staging as much other than gravy. I'd be happy with mono clock-radio if the performance was good enough.

C

[Evil Twin]

The room.

Minimum diffraction at the speaker.

Minimum distortion and noncoherent response from the speaker.

Minimum energy from early reflections in the room (which generally means keeping the speaker well out from the walls).

Minimizing low level distortion and noise so that subtle ambience information can be presented without masking.


Setups like this.

[SE-Raider]

Please elaborate...

What would be primary cause for "nocoherent response from speaker"?

Would surface treatment of the enclosure face, using materials by Cascade or others help minimize diffraction at the speaker? I would assume that surface shape and flush mounting would have more effect here, as detailed at Zaph's site.

If early reflections cannot be minimized by plcaement out from the wall, as in small rooms, would treatment of the wall immediately behind the speaker help?

How would low level noise be mitigated/minimized? Amp headroom?

[AJINFLA]

I just noticed something. Is that guy in the back wearing bowling shoes?
Man those are pretty funky.

Cheers,

AJ

[Evil Twin]

What would be primary cause for "nocoherent response from speaker"?

Cones operating beyond their pistonic region go into bending modes, storing energy and releasing it later. This can occur well below the nominal upper end breakup. Resonant peaks at the upper end will amplify distortion products from the motor, and will do so in a time smearing way.

Cabinet vibration contributes similar problems. In poorly designed speakers, reflected backwave through the cone may be a issue. Tweeter distortion creating "air" and intermodulation products folded down to lower frequencies that weren't there in the original recording.

Would surface treatment of the enclosure face, using materials by Cascade or others help minimize diffraction at the speaker? I would assume that surface shape and flush mounting would have more effect here, as detailed at Zaph's site.

If early reflections cannot be minimized by plcaement out from the wall, as in small rooms, would treatment of the wall immediately behind the speaker help?

How would low level noise be mitigated/minimized? Amp headroom?

Modal room resonances. Room modes as a function of both speaker position and listener position- CARA and RPG Acoustics Room Optimizer can help address those. Early reflections at high level that combine with the primary arrival, producing comb filtering of the frequency response. (The balance seems roughly right, but the sound is "gray" or washed out, lacking harmonic texture- a VERY common problem with home systems).

Sound deadening behind speakers is not necessarily the cure- problem areas are anywhere on a boundary (wall, ceiling, floor) that you could put a mirror and see one of your speaker reflected in it when you're sitting in your main listening position.

Listening close to near field with the speakers well out from the walls tends to ameliorate a lot of the room issues, if the LF setup (based on CARA or RPG, or CARDAS) is good. Otherwise, it's much more of a gamble...