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Narrow & deep or flat and wide?


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7 replies to this topic

#1 of 8 OFFLINE   Phil Olson

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Posted June 05 2006 - 07:36 AM

I am curious about something. Why are most speakers narrow and deep instead of flat and wide. It would seem that baffle step would be easier to deal with if it's farther away from the XO frequency.

Just curious.

#2 of 8 OFFLINE   Wayne A. Pflughaupt

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Posted June 05 2006 - 01:17 PM

It has to do with something called “edge diffraction,” which is a raggedness in response in the 3-4 kHz range. It’s caused by soundwaves from the drivers reflecting off the front baffle, and the effect is worse the larger the baffle is.

At least that’s what I recall from reading about it in a hi-fi publication quite a number of years ago, so I might not have it quite right. I tried Googling “edge diffraction speaker” and got this site that discusses it (I didn’t read much of it, so I’m not sure if it answers your question). Scroll down to the link "Understanding Edge Diffraction."

http://www.speakerdesign.net/home.html

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#3 of 8 OFFLINE   Phil Olson

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Posted June 05 2006 - 04:57 PM

I think that's what I meant by baffle diffaction. I also thought that it started below 1KHz. But I could be wrong.

#4 of 8 OFFLINE   ThomasW

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Posted June 06 2006 - 06:28 AM

The criteria for choosing the width of the baffle is contingent on what you want to baffle to do....

The wider the baffle the greater the boundry loading at lower frequencies.

There's a great little Excel based freeware progam called "Baffle Diffraction Simulator" It provides a graphic representation of the output of the driver and the resulting interaction with any size baffle you want to use...

#5 of 8 OFFLINE   Phil Olson

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Posted June 06 2006 - 07:56 AM

Thomas,

Thanks for the info. I think I understand the science but what I don't understand is why people choose narrow over wide.

I have heard that some people try to tune the baffle step to coincide with the XO so that it can be 'solved' with one speaker but I've also seen that many seem to keep the speaker no wider than the widest driver.

On the other hand, in wall speakers seem to take advantage of basically infinite baffle.

I guess I'm asking why no one seems to choose wide. One reason I can think of is that the baffle is the weakest part of the cabinet so making it narrow will make it more stable. I would think, though, that this could be fixed by doubling the thickness, although it would make the enclosure deeper again.

#6 of 8 OFFLINE   Chris Tsutsui

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Posted June 06 2006 - 08:35 AM

Aesthetics also has something to do with it since "skinny" is beautiful. People also only have "so" much room if they want a TV, equipment rack, etc...

It also depends on the design compromise of finding the baffle that has good size/volume, aesthetics, and complexity.

Dipole speakers and ESLs tend to be flat and wide where Omni-polars might have no baffle at all. Then there's Horns/waveguides, which are almost like "shaped" baffles.

#7 of 8 OFFLINE   SamNavy

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Posted June 06 2006 - 08:42 AM

This answer might not be as technical as you think.
The average consumer doesn't buy speakers for pure sound quality. The average consumer wouldn't know the difference between $1k Kef's and $15 Radio Shacks and probably doesn't care all that much. Bose would be out of business overnight if everyone who bought speakers came to this forum and searched for five minutes. The average consumer is nobody on the DIY board.

If you designed an acoustically "perfect" speaker (even if we could come to a consensus of what "perfect" is), would the drivers and cabinet in any way resemble what we have in our living rooms?

Speaker companies have to be able to sell their products. We here on this board for the most part would gladly sacrifice a little aesthetics for better sound. The average guy walking into BB (with wife in tow) would never buy a "wide" speaker. Can you imagine a "wide" front panel of a 3-way with a 12" woofer. It'd be three feet wide!!! How do you fit that into the living room? Even some of the 2x6.5" center channels out there are monsters.

I think the bottom line to your question as to why there are no flat/wide speakers is that nobody would buy them. You couldn't place them on the ground, so they'd have to be on shelves/wallmounted/stands. Check out the JBL Northridge series... they're fairly wide/flat and shallow. And designed to be wall mounted mostly. I think they're hideous. How about these JBL's towers w/8" drivers http://www.jbl.com/h....at=PER&ser=PER I think they're fairly wide for 8's. And they're still tall for a tower, but very thin. They look great, but I'm not spending $3400 on a pair of JBLs. Am I too far off on this?

#8 of 8 OFFLINE   Phil Olson

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Posted June 06 2006 - 01:25 PM

Ok, I was just curious. The jbl model was what I was talking about. I was thinking that if I wanted to hide them behind columns it might be easier to make them that way. I might build a couple of boxes, (one of each shape), with the same drivers and do some measurements of each.