narrow and wide baffles and imaging


According to all the "professional" audio reviews that I've read over the last several years, narrow baffles are crucial to creating that so-desired pin-point imaging.

However, over the last few weeks, I've had the opportunity to audition Harbeth 40.2, Spendor Classic 100, Audio Note AN-E, and Devore O/93.  None of these had deficient imaging; indeed I would go so far as to say that it was good to very good.

So, what gives?  I'm forced to conclude that modern designs, 95% of which espouse the narrow baffle, are driven by aesthetic/cosmetic considerations, rather than acoustical ones, and the baffle~imaging canard is just an ex post facto justification.

I can understand the desire to build speakers that fit into small rooms, are relatively unobtrusive, and might pass the SAF test, but it seems a bit much to add on the idea that they're essentially the only ones that will do imaging correctly.



128x128twoleftears

Showing 3 responses by josh358

I've heard from a speaker manufacturer that the main reason we're seeing so many ultra-narrow baffles is WAF -- narrow speakers can be shoehorned between the furniture.

Otherwise, I think it's a tradeoff. As Alon Wolf said, a larger baffle reduces the baffle step effect, something that can never be completely corrected. On the other hand, a large baffle causes diffraction issues that are known to interfere with imaging and can also block room reflections that add to the sense of space. In any speaker, these issues can be minimized by for example curving the edges of the baffle and using felt.

Interestingly, though, the most holographic imaging I've ever heard was from the IRS V, at Lyric. Which of course had a huge baffle, curved to minimize diffraction effects. As I recall, the room was also quite dead, which tends to give you pinpoint imaging at the expense of spatiality (width and depth) and a sense of ambiance. And it was being used with tube electronics (CJ) that were known for enhancing depth (out of phase second harmonic distortion).

Otherwise agree with those who say to get the electronics out from in behind the speaker -- the rack will cause a reflection and create a virtual speaker that confuses imaging.

One of the most important factors in imaging seems to be the distance from the speaker to the walls -- you want ideally to have no early reflections greater than -20 dB for the first 25 ms or so, because the ear uses first reflections to judge the size of a space and early reflections from the room mask the recorded ambiance of the original venue. In all but very large rooms, some acoustical treatment (absorption or diffusion) at the early reflection points is needed to do this.

You also have to consider your distance to the rear wall. I've found that if you're too close to the rear wall, rear wall reflections interfere with the imaging. Since in my own undersized listening room I have to sit a few feet in front of a wall, I put some Owens Corning 703 on it and the imaging problems disappeared.

Another imaging rule that I've found useful is that good mono makes good stereo. If you listen to a mono recording or pink noise it should be pinpoint centered between the speakers. That will give you palpable, pinpoint stereo imaging. Asymmetries in the listening room and setup can cause the sound to wander with frequency. I recently put a sheet of plexiglass in front of a window behind my right speaker to flush it out with the wall, and I was astounded by the improvement in imaging. I didn't think a couple of inches would make such a difference, but it did.

It's amazing how much of a difference small changes to the room can make. For example, I have a computer monitor off to the side, and when I angle it so that it faces the rear wall and doesn't reflect the sound from the speakers to my ear the imaging improves. A Umik-1 measurement mic and the impulse response display in Room EQ Wizard are great tools for catching early reflections.
They were amazing, weren't they? I remember having the sense that I could go into the soundstage and walk between the instruments.

Soundsrealaudio, that's an interesting point and one I'd never heard.
Yes, the IRS V had a very large baffle. But Arnie Nudell, physicist that he was, curved it back to minimize the effects of diffraction.

Also, the note that the mids and tweeters are right next to one another, producing something close to a coherent line, and they covered a wide frequency range, with only the deep bass, which is hard to localize, produced by the separate woofer towers. By comparison, line sources like Maggies or Apogees have more separation between the drivers, smearing the image laterally.

Paradoxically, it’s the wide baffle of the IRS that makes the extended frequency range of the line possible, by better supporting the bass.

The problem that I had with the imaging of the IRS Betas that my friend had was that each frequency range came from a different height. Maybe his listening seat was too close, but it used to drive me crazy. Very cool plasma tweeters, by the way!