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Can someone walk me through speaker design? I have no idea.

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Can someone walk me through speaker design? I have no idea.

Postby Matthew Lau » Thu Feb 02, 2017 11:16 pm

Dear MIMFers,

For the longest while, I've been obsessed with getting good sound and responsiveness from a wooden box (guitar).
More recently, I found out that audiophile speaker guys place a huge amount of focus on getting rid of sound, coloration, etc from the a quasi-wooden (plywood or MDF) box.

Am I missing something?!?

I'm honestly pretty confused when 3/4" MDF is touted as superior to baltic birch ply, and more superior to good air-dried solid wood enclosures. I'll be building the Parts Express Overnight Sensations, as I'm finally tired of my $12 Amazon speakers.

Oh, and can someone point me towards good esthetics?
I want to make my speakers look nice even though they're "cheap."
I've heard sonus faber is nice? Any suggestions of dressing up the speakers?

-Matt

ps. I'm not trolling. I'm truly confused. Additionally, I find luthiers to have a superior sens of good taste to most "audiophiles." I mean--how do you get more audiophile than recreating the sound on the actual instrument that was played originally?!?
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Re: Can someone walk me through speaker design? I have no idea.

Postby Bill Raymond » Fri Feb 03, 2017 12:12 am

I believe the preference for MDF is because it has a higher damping factor than plywood, although ply will make a fine speaker enclosure as well. As for aesthetics, I believe that's a matter of individual taste. Some might be happy with a nice coat of paint, others would prefer a fine veneer, and there are other possibilities out there. Otherwise I can't give much advice as I still prefer my Altec voice of the theater speakers with 15" woofer and horn tweeter in a large ported bass reflex cabinet over anything I've heard, so I'm pretty much out of the mainstream of contemporary thought on loudspeaker design. I have been thinking about making an R-J bookshelf speaker for my TV, though, as I can't stand the awful bass in most speaker systems popular today. :|
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Re: Can someone walk me through speaker design? I have no idea.

Postby Bob Gramann » Fri Feb 03, 2017 12:55 am

Let me preface these comments with the statement that I haven't had to make a speaker box in over 20 years and I am no expert in speaker design. You can get books on speaker design and calculate box volume and port size and placement and where you will need peaks to replace dips in the drivers. I always found that way more complicated than I wanted to mess with. A good speaker box doesn't add anything to the sound but rather provides a baffle for the speaker so you don't get phase cancellation from the sound coming around the back. So the massive mdf is less likely to have a resonance within frequency range of the driver. I started with the theory (which I learned somewhere in the 60's) that the best speaker enclosure is an infinite wall. So, going for fidelity rather than volume, I would build the largest box that would fit where I wanted the speaker, pack it with fiberglass insulation, and put a driver in it with the flattest and widest frequency response that I could afford at the time. All that design information from the books can get you a more efficient enclosure and maybe some more bass. I never wanted to go through all that work. The speakers in my living room are a pair of Yamaha NS-244s with 10 inch woofers. They are pretty clean sounding, which is what I prize.
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Re: Can someone walk me through speaker design? I have no idea.

Postby Bill Raymond » Fri Feb 03, 2017 2:22 am

I'm not sure how I got that emoticon or emoji or whatever you call that thing in my post, but it was a mistake--I never use the things!
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Re: Can someone walk me through speaker design? I have no idea.

Postby Matthew Lau » Fri Feb 03, 2017 2:49 am

Thanks for the quick feedback!

I know that a few builders cite speaker design as influencing their bracing system.
I think Greg Smallman was one? He had a plywood rim and a fairly inert back/sides if I recall right?
I've never played his instruments before, so just supposition.

I the case of dampening is the big thing, why not build with a vacuum pocket? Like mdf with foam, rubber, or sand between several layers? It'd cost a bunch to do, but would it sound good?

I dunno. My mind is blown.

Also, any recommendations for esthetics?

I was looking at the Sonus Fabers, and they look sorta nice.
I'm thinking of building these for a friend--if they turn out great, I'll give them to him and make myself another pair (more from scratch this time). Leather, cherry, gloss black.

I have a feeling that this might be a fun alternative to building guitars. MDF is dead cheap and easy to get compared to Baltic birch ply (that I like for cabinetry and jigs), soundboards, back and sides, etc. There's a ton of creative possibilities too, since the box is MDF, and built to be intentionally dead!

My buddy says he likes cherry wood, leather, gunmetal gray and orange.
I'm not 100% sure how that would work out, as gunmetal gray doesn't seem to pair with any particular wood I can think of.
I may do the veneerwork and assemble mostly unfinished. He has a friend who repairs cars for a living, and may provide autobody finish.

I'd appreciate suggestions.
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Re: Can someone walk me through speaker design? I have no idea.

Postby Matthew Lau » Fri Feb 03, 2017 2:51 am

If it were me, I'd probably do an oil finish on the veneered wood.
I'd fill and die the nonveneered stuff, probably black.
I'd french polish the whole sucker.

Than again, I *only* know how to french polish, sadly enough.
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Re: Can someone walk me through speaker design? I have no idea.

Postby Joshua Levin-Epstein » Fri Feb 03, 2017 3:03 pm

That kit looks like a lot of fun. Needless to say you are overqualified in regard to the necessary "woodworking". I got a pair of tweeters from them and they really revived our old beloved Baby Advents. I'll bet that kit will sound really good, and then the "I wonder if I....." will begin
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Re: Can someone walk me through speaker design? I have no idea.

Postby Bill Raymond » Fri Feb 03, 2017 5:23 pm

Wharfedale used to produce a speaker system with a sand-filled baffle. Gilbert Briggs, Wharfedale's founder, claimed that it produced superior damping of the baffle. I believe they used 2 layers of 1/2 inch plywood separated by maybe 1/2 inch of sand. I doubt that they still manufacture one, but it was a pretty successful idea in the 1950s.
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Re: Can someone walk me through speaker design? I have no idea.

Postby Brian Evans » Sat Feb 04, 2017 8:06 am

I used to fuss and fart with speaker design, all the old helmholtz resonators and ported this and that. Back in the day a 35 watt RMS per channel amplifier was a big serious piece of kit (I still have a Dynakit Stereo 70 on my bench downstairs). That meant the efficiency of the speaker was paramount, so the loaded horns and ported bass reflex designs ruled the roost. Now you can get audiophile rated Class D amplifiers with 500 watts RMS in a package the size of a shoebox for very little money, most modern music is mixed to favor MP3 digital compression and speakers can by front ended by sophisticated electronics that tailor the frequency response to as flat as flat can be. Most of the design, from what I've seen, is based on what looks good on the outside, they have specialized driver designs, fancy cross-overs, bi-amping, gold plated wire, and stick it all in an mdf box and staple some fiberglass batt inside.
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Re: Can someone walk me through speaker design? I have no idea.

Postby Halgeir Wold » Fri Feb 10, 2017 4:41 pm

One of the problems in speaker design, is that you can make almost all the wrongs there are, but unless you make a dead electrical short there will always be sound. If it sounds good is another story. MDF is commonly used in most commercial designs from cheap to very expensive, although some audiophiles claim it sucks the life out out of the music. Some claim that baltic birch ply is a better material, mainly because it is stiffer than MDF. To a point this is also true. Chipboard is another good solution. Solid wood may or may not work, but is usually avoided because of well known problems under varying humidity conditions. The big difference between acoustic instruments and loudspeakers is that in an instrument you want to use the resonances of the wood to add to or characterize the sound, but in speakers cabinet resonances will add to the sound from the speaker elements in an uncontrolled way which makes the design math uncertain - and yes - modern speaker design is usually a math exercise. Based on these aspects, good speaker cabinets rely upon avoiding and combating panel resonances in various ways - mass loading, bracing, irregular shapes etc etc. All panels will resonate, and another trick is to use mentioned tricks to move the resonances above the passband of the respective elements. An often used trick is to use a "golden ratio" between individual panels sizes.
Crossovers are another culprit. While it is easy to calculate crossovers that is driven and loaded purely resistive, no speaker element is a resistive load - they are all reactive, mostly inductive, and this leads to all sorts of tricks to compensate the nonlinearities that the load creates. A rather good book on these subjects, without all the heavy math that is involved in modern speaker design, is Vance Dickasons " Loudspeaker Cook Book".
Then enter the looks. Fancy looks, in terms of lacquer, veneering and other cosmetics influences the sound to a very small degree, but OTOH, few of us wants a plain chipboard box in our living room. Sonus Faber is one of the up-market brands that also focuses heavily on appearance, - so also Bower and Wilkins in some of their designs, and several other brands. In this context we are talking prices from around 10k $ and upwards.
As for DIY - if one doesn't want to delve at least partly into the fundamentals of speaker design theory, kits are an easy way out. The woodworking and finish is solely up the builder. The final result will mostly surpass equally priced sets by a good margin, - add more or less elbow grease, woodworking and finishing experience, and the final result may totally outperform similarly priced commercial units. After all - it is all about the music - isn't it???
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