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Multi-Way Conventional loudspeakers with crossovers

Curved sided speaker enclosures, why?
Curved sided speaker enclosures, why?
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Old 21st January 2009, 11:49 AM   #11
Wingfeather is offline Wingfeather  United States
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Totally. A spherical internal shape just creates one single honking great resonance. Worst possible shape unless the driver used doesn't operate at the resonance's frequency (or, presumably, have any harmonics there)

B&W seem to do something clever by cutting a hole in the sphere opposite the driver and attaching their exponentially tapered tube to it (as in the nautilus speakers). Not entirely sure how it works, but it looks interesting.
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Old 21st January 2009, 12:09 PM   #12
cirrus18 is offline cirrus18  United Kingdom
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Quote:
Originally posted by pjpoes
Visually curved shapes reduce the appears of size. While acoustics plays a role in curved cabinets, I believe the primary one is appearance. It looks more visually appealing, and has the effect of reducing the visual presence a speaker has in a room.

Thanks guys for the replies. It looks like curved is the way to go. It's a win-win situation. Less moans from the other-half about great big monstrosities in the lounge and better acoustic performance.

Curved, here I come.
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Old 21st January 2009, 12:19 PM   #13
annex666 is offline annex666  England
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Default Baffle step

I'm surprised that no-one has mentioned the baffle step yet, so I'll chirp in...

Spherical enclosures have a very smooth baffle step response - they can, in theory, be equalized to remove the effect of the baffle step completely.

Enclosures with a flat baffle show very uneven transition between 2PI and 4PI radiation and may be considered inferior in this respect.
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Old 21st January 2009, 01:40 PM   #14
bear is offline bear
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Somehow the idea that all of this depends on wavelength, and therefore dimension seems to be lost in the discussion. It's important, and critical if you want to make an intelligent decision or understand it at all.

As far as -40db down being important, I'd say that it is, but show me an enclosure that has the rear reflected energy down -40db? That's not so simple to do. Impossible the way most enclosures are built internally - what's in them. In fact the lower in freq u go, the less effect anything you do inside the box has...

So what are we talking about?

And, let's understand that a standing wave means nothing unless it is radiated through the diaphragm and out of the box... what we're really talking about is reflected energy, and if a standing wave at some frequency will cause a peak or dip in the response.

Let's take a look at the dimensions vs. frequency vs. wavelength for a standing wave in the audio band, and see what frequency the box dimension starts to be an issue... and what absorption can be effective (and how much) at that freq before worrying about fancy internal shapes.

Put this way, volumes of air don't notice non-parallel walls until the frequencies get fairly high, at which point if you have not yet absorbed the rear radiation, imho, you've built a poor enclosure...

Or, which would you rather have - a volume taken away by a curved side or filled with a highly absorptive material that works lower in frequency as its thickness dimension increases??

You decide.
I know what I would pick.

And, stiffness is only valuable if the material does not re-radiate sound via transmission, no matter what the frequency. It could be argued that if you had a choice between an enclosure that radiated no mid and higher frequencies, but radiated LF, compared to a cabinet that radiated mid and highs (stiff, eh?) and few lows that the former would sound better overall.

Obviously the ideal enclosure has no baffle step, radiates nothing, and has zero reflected internal energy... anyone got one?

_-_-bear

PS that's monkey coffin not money coffin...
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Old 21st January 2009, 04:36 PM   #15
planet10 is offline planet10  Canada
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Curved sided speaker enclosures, why?
Quote:
Originally posted by bear
And, let's understand that a standing wave means nothing unless it is radiated through the diaphragm and out of the box...
Or if it builds up sufficient energy to excite a cabinet resonance.

dave
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Old 21st January 2009, 05:12 PM   #16
cirrus18 is offline cirrus18  United Kingdom
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Quote:
Originally posted by planet10


Or if it builds up sufficient energy to excite a cabinet resonance.

dave
Well, if this is a problem and everybody is going down the road of thicker and heavier enclosure walls how about thinking of something different and possibly better

I live on a very busy main road and without double glazed windows I would never get to sleep at night, it's so noisy. I am quite amazed how quiet my bedroom is, just relieving the pressure on the window catch: ever so slightly, allowing the airtight seal to just break and it is quite amazing how much noise comes galloping in through this miniscule gap.
To my mind the gap between the double glass facings is attenuating the sounds from the road dramatically. Couldn't this apply to speaker cabinet making?

By building enclosure walls with say two 5 mm sheets of ply wood with a 10/15 mm air gap in between. Of course the gap must be 100% airtight.
Or alternatively filling the gap with some inert substance such as sand.

Over to you.
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Old 21st January 2009, 08:27 PM   #17
chris661 is offline chris661  United Kingdom
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Default Those Nautilus tweeters

The idea behind them is to make 0 loading by air pressure on the tweeter, to allow movement more freely. Like those speakers that have channels inside the speaker cabinet which makes the pressure dissipate as it goes through the chanel.

However, the curved sides imporve stiffness because they are tense. Think about it - those panels used to be flat. They they were bent. This adds tension. Meaning there will be less audiable resonance stuff. Because they are more tense, it will be harder to shift them (to create the soundy-resonancy peak).

Basically there's less resonancing to worry about
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Old 21st January 2009, 08:44 PM   #18
smokinghot is offline smokinghot  Canada
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Quote:
Originally posted by cirrus18

By building enclosure walls with say two 5 mm sheets of ply wood with a 10/15 mm air gap in between. Of course the gap must be 100% airtight.

If you could somehow float the internal enclosure within the external, then you might have something. As it is, they would have to be physically connected at mulitple points, and therefore still transmit the resonance you're trying to eliminate.

Not to mention, how would you deal with baffle of the external enclosure?.... ....some airtight membrane..?
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Old 21st January 2009, 09:06 PM   #19
badman is offline badman  United States
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There have been many good points made on this thread thus far. Bear talks of the lost space (compared to a rectangular cab) which could be used for absorbtive material for better internal reflection/standing wave performance.

But, the rounded enclosures still retain the stiffness and diffraction benefits. Also, early internal reflections will tend to "bounce around" more before re-exiting, since there will be widely distributed incidence angles for the backwave components. This will mean more energy is likely retained within the cab and dissipated or at least delayed prior to re-exit.
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Old 21st January 2009, 10:05 PM   #20
cirrus18 is offline cirrus18  United Kingdom
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Quote:
Originally posted by smokinghot



As it is, they would have to be physically connected at mulitple points, and therefore still transmit the resonance you're trying to eliminate.

Not to mention, how would you deal with baffle of the external enclosure?.... ....some airtight membrane..?
Yes, but it wouldn't be connected everywhere, perhaps only 15/20% which would have these same sound transmission characteristics as a solid walled cabinet so you haven't lost or gained anything there. The remaining odd 80% or so would have very low transmission, so therefore over all, one has gained. If my theory is correct that is.
Anybody want to test it out?

Similarly with the speaker baffle, this could be of similar sandwich construction, sealed around the edges with say half inch wide 12 mm thick strips of wood. For the speaker cut out, a piece of 12 mm thick MDF which would overlap inside the sandwich once the speaker hole has been cut out by perhaps 1 inch, leaving something solid for the speaker to be mounted to.
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