Any speaker experts here?

This speaker question kinda goes with my previous question(s) about tubes. I have been looking at tube stuff on the web and some of it really appeals to me. I'm a machinist and have a shop so making knobs and the like is easy for me to do. And some of the tube sets with exposed tubes and transformers sure are pretty. So I got to thinking about speakers. I would like to have metal enclosures (cans really) for the speakers that follow the shape of the speaker. Each speaker would then be mounted on its own pole. Or maybe three speakers, mounted vertically, on a pole. The enclosures would be nickel plated. Probably brass, because I can spin brass. Nickel plate it too. I've got the stuff. The enclsures should also have some sort of nickel plated grille too. I know it sounds ridicolous, but the idea appeals to me. Could I get good sound with the enclosures I'm describing? Would the enclosure need to be perforated? Shoul I just get a life? Thanks, Eric

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etpm
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I don't know much, and much of what I know is old.

But I think such enclosures would make for horrible sounding speakers. For the most part you need to give the speakers room to move, in rigid cabinets that won't contribute their own motion to the sound.

I do know that there's a science to it. 30 years ago -- back when I cared about such things -- the science said that you wanted the speakers mounted in a big cabinet with lots of air volume, with rigid walls and some sort of sound dampening material on the inside (so that you wouldn't hear all the echoes from inside the cabinet).

Time progresses, folks have figured out better ways to do things, and I dunno what that is. I'd go looking for a book on DIY speaker cabinets that was written in the last ten years or so, and hope that it's by someone who knows his stuff.

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Tim Wescott

There are several programs for speaker cabinet design. You will need the specifications of the speakers provided by the manufacturer. I am in agreement with Tim and my knowledge is also old. Tom

Reply to
Tom Biasi

WinISD Alpha is one of the better programs out there, despite being in alpha. The beta is far more limited. But I'm not sure either will be happy with cylinders - though most of the numbers have more to do with volume, so you can work from a box approximating your can's volume and it should be close, -ish.

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Reply to
Ecnerwal

If you can hit the metal cabinet with a hammer and it rings, it probably isn't good as a speaker case. If not much happens when you hit it, it might be okay.

Those Radio Shack Minimus 7 speakers (and their descendants) didn't suffer from being in a metal case, but that's the rare case. A whole generation of speakers for shortwave receivers were in metal cases, with open backs, really pretty lousy, but nobody cared since it wasn't about hifi but about voice communication.

Thin metal won't work.

Michael

Reply to
Michael Black

smooth curves are good, because they withstand pressure differences without deforming.

To port or not to port... As I understand, it's a loudness vs fidelity trade-off.

no! build it!

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Reply to
Jasen Betts

Defintely do NOT make the enclosures from metal, or anything resonant. The best material is actually one of the cheapest: Particle board. Usually Medium Density Fiberboard (MDF) is recommended, but any flake or chip composite will probably be OK. (High density is also good.)

As for your thought about following the shape of the speaker, the enclosure shape is not terribly critical, but the volume is. There are two basic design types: sealed box or ported box. (Omitting exotics like horns and transmission lines.) In either case, the design box volume is related to mechanical properties of the woofer, such as the free-air resonance frequency and the compliance or "springiness" of the suspension. Those can be gotten from the supplier for most of the better brands, but they can also be measured with fairly simple equipment. Then you plug them into a formula that tells you the ideal box volume.

Ported speakers have an additional variable. Instead of the box being sealed, there is a "port" in it which is typically tuned by having a heavy cardboard tube behind it. The general idea is that the speaker and box combo has a resonant frequency below which sound output falls off quickly. The port can effectively move it down a bit. It also increases bass output by radiating the lower frequencies itself.

So back to your quest: You can do a full design job using speaker parameters (or measurements) and equations (or software), build a nice MDF box, and *then* cover it with metal... or anything else. (Many people opt for fancy wood veneer, but a cheap, simple, and attractive alternative is upholstery fabric. It can be chosen to go with the room decor (and easily changed later), and you can put it on with a staple gun and some careful folding.)

Note that box design only pertains to the low-frequency response of the woofer, but most speakers also have a tweeter, or a tweeter and midrange (or multiple). The tweeter/midrange needs to be matched to the upper end of the woofer response, or (more typically) a "crossover" network is used to low-pass filter the woofer and high-pass filter the tweeter/midrange so the overall response is reasonably flat. The crossover is thus an important comonent in the overall system.

So the other way you can approach this is to buy a speaker you like (actually a speaker system, including enclosure , woofer, tweeter, crossover, etc) and then cover it with metal.

Or buy a kit from a supplier, which will typically have all the parts (sometimes without the enclosure, just construction plans). Follow their plans exactly and then cover the enclosure with metal, OR come up with your own enclosure design that has the exact same interior volume as specified.

Best regards,

Bob Masta DAQARTA v7.50 Data AcQuisition And Real-Time Analysis

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Bob Masta

Thanks Bob and everyone else who replied nto my question. It seems that making an enclosure that follows the speaker shape is a bad idea. I suppose I could make some from wood lined metal but the shape will still probably be wrong enough to make the speakers sound bad. Eric

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Reply to
etpm

You still seem to be missing the other half of the equation: the volume of the enclosure will still be way too small.

Speakers need to be in BIG boxes, or they need some magic with the tuned vents (the teeny Bose speakers have this magic).

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Tim Wescott

David Weems used to write endless construction articles for the hobby electronic magazines on building speakers. And he'd use all kinds of things, sewer pipes and cardboard boxes, to make the boxes. Just about any shape or material did work. The caveat was that you had to know what you were doing, understanding what the cabinet was there for and what made one good and one bad.

It also matters what you are using the speakers for. Voice communication has a very limited frequency range, and you can get by with a lot less. A speaker running at low volume (because you've got it close to your ear) will be less fussy than if you were running more power into it. If you want hifi, you will need a lot more.

Headphones are easier to make "hifi" because they feed the ear directly, thus low volume, but also the room doesn't become part of it all. "Computer speakers" get away with being really awful because one generally has them relatively close to the ears. One might be better off mounting them on your chair, feeding the ears more directly.

Michael

Reply to
Michael Black

Soon, upscale hospitals in high-tech centers will be offering Bluetooth neural implants for infants, side-stepping this whole messy vibrate-the- air business.

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Tim Wescott

Hi Eric, OK this is a total hijack of your thread and question. (I suppose I should take it over to rec.crafts.metalworking... but you know what it's like over there.) So can I ask a few questions about metal spinning? I'd like to make some little radiation shields for use at 77K (liquid nitrogen) So cylindrical type cups.. maybe 2" diameter and ~4" long. I've only heard about spinning aluminum, but you mentioned brass. Can you also spin something like TeCu (tellurium copper)

Does the spinning work harden the metal? Can it be annealed afterwords? How thin a wall/ bottom can you get.

Thanks. George H. gherold(-AT-)teachspin.com

Reply to
George Herold

I have heard that 'stone' works well. The mass helps provide a stable platform. A few years ago I saw an article on using the clay tile drainpipe as a stand for mounting speakers inside it. The idea was that the back side being open provided a phase boost to the bass and took the low end lower than the speaker, or so.

Sorry, years ago, can't recall the publication, nor name of article.

Reply to
RobertMacy

I suspect there were some commercial speakers made with stone or concrete.

But that's the advantage of making your own, you can try things that aren't economically feasible. Stone or cement might be cheaper than some other materials, but the cost of shipping is going to ruin it. But if you can get locally, you can experiment.

Probably Popular Electronics, that often had a speaker project in an issue, and as I previously said, often written by David Weems.

I certainly remember one article by him about using a drainpipe.

Michael

Reply to
Michael Black

Bet that's it!

Plus, remember someone made a rack of sixteen, mounted four by four, 4 inch speakers that made a woofer like you wouldn't believe. Then, someone complained about all the resonances adding up or such. sigh. you can spend a lifetime in this and NEVER make much progress.

Reply to
RobertMacy

Please please please ask this question on the metalworking group.

Here's the answers to your questions, to the best of my knowledge:

Yes.

Yes, depending on the alloy.

Dunno, but probably way thin.

I used to work at an infra red imaging company that needed pretty fancy little radiation shields to get adequate image quality. They were made by machining an aluminum mandrel on a lathe, then plating it with copper, then etching away the aluminum in an acid chosen to dissolve aluminum but not Cu.

It worked a treat, but the whole system cost $$$$$, so it's not necessarily cheap.

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Tim Wescott

Jim Kyle had that article about the "Sweet 16", yes lots of speakers and something about how the multiple speakers null out the bad parts of the cheap speakers or something like that.

I thought it was just a general speaker, not a woofer, but the accumulated speakers allowed for bass response.

It was in Popular Electronics in the late fifties or early sixties, I've seen the article, it's somewhere around here (and might be on the internet). And for the next decade, there were followup articles, some arguing against, some in favor, and others extending the idea. I think there were even commercial versions of it, but there may have been more planning to those while a review I think I read saw it only as a commecial version of the Sweet 16.

Michael

Reply to
Michael Black

Greetings George, You can indeed spin many different metals. I have never worked with tellurium copper alloy and so can't say whether it can be spun easily. Spinning does work harden the metal. Depending on the amount of movement from the original disc a part may or may not need annealing. Cylindrical cups are hard to spin. especially the ones you describe. You would be better off soldering or welding. Can TeCu be welded? Will the fumes kill you? One of the first things I attempted to spin was a sterling silver shot glass. Tall for its diameter. It was quite a challenge. Eric

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etpm

,snip>

TeCu machines much nicer the Copper, similar to brass. (If that makes any difference in spinning.) But the thermal conductivity is better (than brass). For the radiation shield it'd be nice to nickel plate it too.

I'm mostly worried about the conductivity*, I guess it depends on how much the conductivity changes with work hardening.

Hey, that's interesting. Say I take a piece of copper wire, Put one end in the vice and pull on the other till it gives a bit. (I'm sure you've done this, you get a nice straight piece of wire.) How much does the conductivity change? (Thermal or electrical.) (Well besides the geometrical effect, longer length, less area)

What makes it hard? I don't need sharp corners, a rounded bottom would be fine. (In fact I'm a man that likes a round... never mind.)

It solders just fine. But soldering never looks great. (this is for something to sell.) Hmm, What does it look like if you nickle plate over solder? I don't know about welding, can you weld brass?

"fumes kill you".. Ahh you are thinking of BeCu (Beryllium) maybe

Thanks for the response. I better move this to metal crafting, Tomorrow. George H.

Reply to
George Herold

One factor to consider with speaker arrays is "beaming". This seems at first counter-intuitive, but adding speakers along one axis actually constricts the sound on that axis to a narrower beam, unless you physically angle the speakers to broaden the coverage. Commercial installations thus use vertical stacks to put more of the sound into horizontal coverage. I don't recall ever seeing the converse.

So the Sweet 16 would have had a narrow "sweet spot" for listening.

As I recall, this was before the days of Thiele and Small (who gave us scientific box design), and the array was open-backed. Many speakers were open-backed back then, which caused loss of bass when the back wave interfered with the front output. Just the fact of having a wider front panel, never mind the increased drivers, would have helped reduce the back-interference. Similar to the effect of an open-backed but deep box (also popular back then) or a sewer pipe, it just increased the distance that the back wave had to travel before interfering with the front wave.

Best regards,

Bob Masta DAQARTA v7.50 Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, Pitch Track, Pitch-to-MIDI FREE Signal Generator, DaqMusiq generator Science with your sound card!

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Bob Masta

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