DIY Cabs--Source for plans, components, etc.?

[Ericman197]

I have a question that's sort of on the subject. My friend's father is a carpenter and used to build bass and guitar cabs back in the 70's. We've decided to try building our own cabs, just for fun. Our first project is to try to build a better "home" for my friend's Eminence V12 speakers; they're currently housed in an Avatar Speakers 4x12" slant guitar cab. I've already done all of the design work, and what I've found is that we need to make the enclosure have more volume than it does now. My question is this:

Which would be better: One large chamber, or individual chambers for each loudspeaker? I would assume that the individual chambers would be better. I've gotten the idea from manufacturers like Accugroove who put each driver in it's own chamber. We'd like to try doing that with a guitar cab to start. Also, if we were to put the drivers in individual chambers, could they be segregated? For example, could I then split it into 2 2x12"s, each with 2 tuned chambers? The Avatar cabinet is basically just a big box with no chambering or bracing, so we think that by making individual chambers, caulking the inside of the cabinet, putting in quality acoustic material, using locking bolts to secure the drivers, etc. we could make a guitar cab that has a tight, defined low end without the muddy effect that most tend to.

 

[The Bassmaniac]

My thought now is to buy the head, and the components for the speaker cab and build the cab myself. I would appreciate any suggestions for books, websites, etc., where I might find general info on cab design, and specific plans to work from.

What sort of wattage head would you be looking at, and what style of music do you play?

Here's a pic of the 2x12" 200 watt RMS sealed cabinet I made.
I can post the plans for it if you like as I designed it myself.
Invalid Link Removed
It gets reasonably loud for what it is and sounds really good to my ears for Motown, Blues and rock styles. Cost me $300.00AU all up, not counting labor.

 

[bgavin]

The great myth of the folded horn is just that: a myth.

To clarify, the horn performance suffers/goes away when the air column length is shorter than the wave length, and the mouth perimeter is less than a wavelength. Doing the math for a 41 Hz note, this is a 27.5 foot measurement. And a 8.7 foot diameter round mouth. Rectangular mouths are slightly larger.

A horn smaller than this cuts off higher than 41 Hz.

The JBL rear loaded horns with their 13 foot air columns were good down to 86 Hz, then acted as direct radiators below that. Note that the horn also unloads below its cutoff point, and 41 Hz is a long way down from 86 Hz.

Some guys have good luck building a horn with a ported rear chamber that tunes around 40 Hz. This provides a bottom note boost in an area where the horn is not working.

I don't want to haul it around, for sure.

 

[bgavin]

As for the V12 drivers, since all four produce the same frequency range, there is no compelling reason to separate them. The box should be 4x the correct volume required by a single driver.

The Accugroove is a multi-way system where each driver has a restricted range of frequencies. There is good reason to keep the low frequency impulses away from the cones of the mid-bass drivers, hence a separate chamber. Further, the mid-bass driver requires a smaller tuning volume than the larger bass driver.

 

[Ericman197]

Hmmm... but wouldn't it make the box stronger? The problem with the current box is that as far as I know, it has little to no bracing. There's a lot of muddy cabinet resonance; you can feel quite a lot of vibration even when my friend isn't playing very loud. By using individual chambers for each speaker, essentially making a cross inside a speaker box, would it not make the box much stronger? I would think so, but perhaps it's not really that big of an issue?

Also, do you recommend stuffing the cabinet? My plan was to buy acoustic dampening material, the eggshell stuff, to line the inside of the cabinet, and then stuffing in some of the foam as well. It currently has just a thin foam'ish type thing along the walls.

 

[emor]

I have spent some time checking out amp manufacturer's websites and doing some searching in the TB archives and have come to the conclusion that buying a complete (quality) rig that is powerful enough to play with a band is a bit out of my budget at this time.

My thought now is to buy the head, and the components for the speaker cab and build the cab myself.

O.K.
I'm rethinking this again.

I could easily build a cabinet on my day off.
I'm sure it would be aesthetically presentable.

However, after considering the time I would have to spend researching the project, the cost of components, and the fact that I probably wouldn't really know what it would sound like until it's done, I think maybe I should just work some OT and save some dough until I can afford something that I can try out. (It's not like I'm itching to build yet another plywood box! If I spend any time at all on a personal project I would just as soon it be an instrument--which I'm also thinking about).

I 'd like to thank everyone who responded to my initial post, even if it just served to help me realize that it might not be the best use of my time.

emor

 

[goodbetterbass]

As one poster said...if you have a specific reason to build one go for it. I managed to save au$700 by building a 1x18 based on the Big Ben driver. I already owned a Labsystems 2x12 and wanted them to mate properly.....also wanted it to be transportable so built in wheels etc. Also wanted it to fit in my car so that was a factor...

Think about it all and give it a go. It does take time...all up abotu 4-6 weeks for me but it wasn't solid work.

Chris

PS..have had may "love the cab" coments so it must look OK. I covered it with the same carpet and grill as my labsystems....

 

[bgavin]

Never build a cabinet to save money. Ain't gonna happen... the major manufacturers have volume purchasing that the private builder can never match.

Build a cabinet when you can't get what you want commercially.

As for plywood, only use the pricey Baltic Birch, Appleply, or other void-free, many-laminate types. Home Depot plywood is better used for firewood than bass cabs. Use MDF if you can tolerate the weight. It is all around better for bass cabs than plywood, but is terribly heavy.

If the cab is resonating, it is improperly braced. The buzz is a huge waste of acoustic power.

 

[Bongolation]

Use MDF if you can tolerate the weight. It is all around better for bass cabs than plywood, but is terribly heavy.

Ignoroids will fight you all day over the assertion that MDF is sonically better than plywood, but it is and always has been. They'll tell you that plywood or even straight-grain wood imparts "tone."

The biggest problem with MDF is fragility, not weight.

 

[Bongolation]

The great myth of the folded horn is just that: a myth.

I've been wondering.

The primitive single-fold Voight principle still turns up in commercial stuff as it's relatively simple, but I've been pretty skeptical of the TL thing if for no other reason than all the designs I see people building are from at least thirty years ago, and the single-fold Voight goes back to the 1930s, before actual speaker engineering even existed. While the Bose "Wave" principle appears to just be a molded plastic transmission line (and a long one), I haven't otherwise seen a real TL seriously promoted for a long time.

One wonders about old designs. There are people still building and raving about the Karlson, and to my astonishment, I saw Roy Rogers's bassist playing through a Karlson box on a recent PBS concert show. Karlsons look neat, but are sub-scientific and utter snake oil.

There a certain sort of nut that seems to gravitate toward exotic antique speakerbox design that manifestly doesn't work.

 

[A9X]

I've been wondering.

The primitive single-fold Voight principle still turns up in commercial stuff as it's relatively simple, but I've been pretty skeptical of the TL thing if for no other reason than all the designs I see people building are from at least thirty years ago, and the single-fold Voight goes back to the 1930s, before actual speaker engineering even existed. While the Bose "Wave" principle appears to just be a molded plastic transmission line (and a long one), I haven't otherwise seen a real TL seriously promoted for a long time.

Thirty years ago? You just need to get up to date. I've heard, and seen measurements on a number of speaks using Martin's models, and they work consistently and predictably well. Sound great too.

 

[A9X]

The great myth of the folded horn is just that: a myth.

To clarify, the horn performance suffers/goes away when the air column length is shorter than the wave length, and the mouth perimeter is less than a wavelength. Doing the math for a 41 Hz note, this is a 27.5 foot measurement. And a 8.7 foot diameter round mouth. Rectangular mouths are slightly larger.

A horn smaller than this cuts off higher than 41 Hz.

The JBL rear loaded horns with their 13 foot air columns were good down to 86 Hz, then acted as direct radiators below that. Note that the horn also unloads below its cutoff point, and 41 Hz is a long way down from 86 Hz.

Some guys have good luck building a horn with a ported rear chamber that tunes around 40 Hz. This provides a bottom note boost in an area where the horn is not working.

I don't want to haul it around, for sure.

Sorry, but again you're incorrect. Ever seen or heard a LABhorn? Designed by Tom Danley of Servodrive and packing enormous performance into a moderately sized package. Still not <i>small</i> mind you (48x48x22"), but with very low distortion and huge output capability that you'd need a very large number of 18's to equal. I have a pair in my living room system and they measure flat to 30Hz (@ 106dB/W), and with 6dB EQ, 20Hz.

I've read all the theory too, from the classic through what the modern designers like Danley and Edgar are doing. The numbers you give above are for 4pi space, and that doesn't effectively exist in real world installations at LF. Modern design techniques and measurements allow lots of careful tradeoff that the classic theoreticians couldn't have possibly implemented.

 

[bgavin]

And I've seen the measurements from the Labhorn also.

They didn't repeal the laws of physics, nor did they rewrite them recently. Wavelength is still unchanged, despite the Tractrix design.

As for your living room, right. We all know the huge gains involved in a room. Standing waves in a living room will produce huge nodes of +/- swing. Flat? No.

Anybody can claim DC to daylight specs on the internet.

So... show me the measurements. Without proof, it's just bullsh!t. "Again".

 

[patrickj]

I'd be interested to read if any one out there actually was able to conclude that building your own cabinet was a cost-effective alternative to purchasing a factory-built one.

There are plenty of reasons out there to build a cabinet including sound, power handling or simply the satisfaction of knowing that you built it yourself.

But in nearly 20 years of bassin', I must have looking into building my own cabs at least a half dozen times, and everytime, the cost ends up adding up to be more than I could have bought one already made. IME, economics is not a reasonable motivation to go the roll-your-own route.

FWIW... I built a 4x12 (and later broke it down, redesigned and rebuilt an entirely new 4x12+2x10) Aguilar copy for probably 1/3 of what it cost to buy one new. I also built 2 GS112 copies for probably about half of what it would cost to buy 1 new.

I do a lot of woodworking though (build basses, cabinets, furniture, etc), so when I figure my costs it's only specific to the materials of the project. I've already got a complete tool shop so I don't need anything else (beyond the project materials) to complete the project - this may be an issue for others though. I also don't consider my design/build time on one a project to be 'billable' because I'm 1) building stuff for me, and 2) I enjoy doing the work.

Building your own can be a lot cheaper, but it can also be a money pit (esp. if you don't have a plan or know how to do what you're trying to do).

$.02

 

[A9X]

And I've seen the measurements from the Labhorn also.

They didn't repeal the laws of physics, nor did they rewrite them recently. Wavelength is still unchanged, despite the Tractrix design.

It's not a tractrix. I never said that the laws of physics were repealed, merely that modern design techniques (and I should have added) specialised drivers, allow us to move closer to what the theory predicts in practice.

As for your living room, right. We all know the huge gains involved in a room. Standing waves in a living room will produce huge nodes of +/- swing. Flat? No.

In practical terms, flat within a 3dB envelope as all measurements within a room will be at best, taken at the listening position. Get <i>anything</i> perfectly flat within a room! Of course there is some room gain, as they're placed at a wall floor boundary, but the room is huge and open plan, so it's not that great. Sorry if you took it I implied you could put a ruler on the trace.

Anybody can claim DC to daylight specs on the internet.

So... show me the measurements. Without proof, it's just bullsh!t. "Again".

Leave the hyperbole at home. DC to light, what a load of crap.
What I acheived isn't that difficult, or uncommon with these. Where they're placed (pi space), they effectively simulate a 4 stack per side, which is more what you'd use in a Pro rig, and in line with what Tom specified in his design.
Are you speaking from experience of working with and designing horns (as I am for quite some time; I'm also a qualified and experienced engineer) or spouting theory blindly?

 

[patrickj]

Hmmm... but wouldn't it make the box stronger? The problem with the current box is that as far as I know, it has little to no bracing. There's a lot of muddy cabinet resonance; you can feel quite a lot of vibration even when my friend isn't playing very loud. By using individual chambers for each speaker, essentially making a cross inside a speaker box, would it not make the box much stronger? I would think so, but perhaps it's not really that big of an issue?

Also, do you recommend stuffing the cabinet? My plan was to buy acoustic dampening material, the eggshell stuff, to line the inside of the cabinet, and then stuffing in some of the foam as well. It currently has just a thin foam'ish type thing along the walls.

You can reinforce the inside to avoid the mud w/o chambering.



Look at the H-brace on this page:
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to see what I mean..

 

[bgavin]

Leave the hyperbole at home. DC to light, what a load of crap.

Hardly. The bass world is full of phony response claims, none of which are substantiated by published response plots.

I got started in bass horns in the early 1960s, by first working on a round mouth model driven by a 5" driver that sat behind a movie screen. The size and length were totally impractical for anything other than permanent installation.

You are not the only qualified and experienced engineer here. You can be as cranky and uncivil as you want, because I absolutely could not care less.

However, I still invite you to PUBLISH your claims. If you have taken the time to achieve this project, then surely you can measure your achievement and post it here. I'd like to see how your achievement performs in front of a decent measurement mic, and away from the enhancements of a confined space.

 

[Ericman197]

You can reinforce the inside to avoid the mud w/o chambering.



Look at the H-brace on this page:
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to see what I mean..

Ahhh, thanks, maybe we'll try that instead. Perhaps we'll stick with the original cab and just throw in that brace and some acoustic material. Hmmmm.

 

[Bongolation]

Thirty years ago? You just need to get up to date. I've heard, and seen measurements on a number of speaks using Martin's models, and they work consistently and predictably well. Sound great too.

I found this page on your linked site really delightful and interesting for a number of reasons, but I think viewing most of these examples with a healthy dose of skepticism is unavoidable.

That said, I have not yet seen on any of these sites any design or discussion of similar principles applied to bass instrument cabs. Not one, and I've looked for a couple of weeks now.

It's kind of eerie.

I am not an engineer. I'm a mere BFA, though I worked for a while at GLI in their heyday (and locked myself in their anechoic chamber to eat lunch in absolute peace every day!). I can build a good cab structurally, and can finish it out to boutique standards. None of this matters if it's a bad design based on fallacious principles (e.g. Karlson).

I'm willing to entertain the possibility that a 1/4-wave bass instrument cab can be worth the effort, but so far I've seen zero discussion of it or examples online.

 

[Nightbass]

That said, I have not yet seen on any of these sites any design or discussion of similar principles applied to bass instrument cabs. Not one, and I've looked for a couple of weeks now.

Have you looked at the Bill Fitzmaurice designs? These may not be 1/4 wave, but they are a very good, modern, proven application of horn design to bass instrument cabs, as long as we're talking about horns in general.

http://www.billfitzmaurice.com/

Bill has 6 DIY plans for $9.95 each. Can't beat that!

Half-space response doesn't look too shabby at all.

Nightbass