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Multi-Way Conventional loudspeakers with crossovers

Is vibration bad or good
Is vibration bad or good
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Old 8th November 2019, 11:39 AM   #11
YSDR is offline YSDR  Hungary
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Quote:
Originally Posted by Galu View Post
There is a school of thought that a loudspeaker cabinet should be designed to be as light and thin as possible.

It is claimed that the more solid and heavily damped a cabinet, the more energy it stores, the slower energy is released and the more sluggish and leaden the speaker sounds.

Having a light and thin-walled cabinet, it is suggested, allows any stored energy to be dissipated quickly.

One would think that light, undamped cabinet panels would vibrate, but could this be essential to convert stored energy into heat and provide the rapid energy dissipation mechanism suggested above?
If the speaker walls are thick and heavy but not stiff enough then that might be a problem, but usually thick and heavy walls are more stiff than a thin and light wall. So the thick and heavy walls are less excited by the vibration from the drivers. This is only my guessing.
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Old 8th November 2019, 07:24 PM   #12
system7 is offline system7  United Kingdom
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Thin-wall or light cabinet construction is based on the fiendishly difficult theory of resonances, and how best to avoid them:

Interesting read I found on Lossy Cabinet designs by Harbeth

The idea is a light and rigid cabinet can't store much energy, and a lot of that energy can be absorbed by rubbery panels stuck to the side and top and bottom walls as it flows around. This is what the BBC found back in the day for their monitor outside broadcast speakers. And light is good when you have to hump them around! Take a tip from an old timer, that rubber feet reduce nasty rattles.

Below a certain -30dB level, cabinet resonances don't intrude. Something Harbeth have applied for many years, and people like them. If a slightly wooden sound is part of the package, maybe it suits wooden instruments in the Classical Orchestra. IDK.

Quote:
Originally Posted by lorenzoS View Post
@System7, always good to hear from a Portsmouth man. When you say a 120 Hz 'lump', this means you suspect they have an active base boost circuit which just massively amplifies the 120Hz band in question? Is it really bad to use such tone controls to compensate from less than flat frequency response, if yes, why?
The libratones are probably 3" basses in reflex. I'd be surprised if they go below 120Hz in any significant fashion. Boomboxes have very little in common with the flattish response of a big bass speaker.

Let's look at a 8" reflex (Qts=0.33) Visaton W200S-8 bass driver in 30L closed box:

Click the image to open in full size.

Now we give it its preferred reflex enclosure, because if it worked well in closed box, it would have a Qts nearer 0.5 and a smaller magnet:

Click the image to open in full size.

See it goes much deeper. FWIW, you can always spot a reflex driver (where there is a tuned tube in the cabinet) by the big magnet.

Hours of fun to be had with the Boxsim simulator:
Software | Visaton

If you want the big bass, the Debra charity shop in Elm Grove has a pair of Wharfedale 8" bass Linton II's for sale at an outrageous 90. I think they'd take 50!

Click the image to open in full size.

Probably most of it still works, and you could fix them if they don't. But good 25L boxes that you could fit most 8" woofers and tweeters to. And biggish bass. Those old speakers are like old digital cameras. People are throwing them away. Bargains to be had.
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"Per ardua, ad astra." Best Regards from Steve in Portsmouth, UK.

Last edited by system7; 8th November 2019 at 07:47 PM.
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Old 8th November 2019, 10:32 PM   #13
res07njc is offline res07njc  United States
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I've read about these lossy/resonant cabinet constructs. I'm quite certainly no expert, but they do seem to offer something lively? Is that the right term? Where a life-like or euphonic experience can occur, at the expense of volume.

For lower volume listeners like myself this seems like something worth pursuing; but still respecting the science of all of this, it also seems like something difficult to analyze/predict/replicate for a given situation/equipment and thus a black art area.

And then dependent on one's taste even. I wish there were more of these types of speakers being DIY's or explored. The experimental nature of it is prohibiting, unless you want to build 4 or 5 different cabs to experiment with. If only there was an LtSpice for materials....
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