# building a cab! i need advice.



## dylanreimer (Nov 16, 2009)

Im building a half slant cab. With MFD. I would like to put at least 2 Vintage 30's what else should i put in there? I have been reading some articles and have some questions. What is "Q" and "F3"? in lamens terms please haha. In other words, what should i know before i start this project. Building the cab is not the problem. I just dont know what to put in it! Help would be much appreciated!

Thanks alot!

-Dylan Reimer.:wave:


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## Zeegler (Jan 2, 2006)

Well, that's like asking "how long is a piece of string?". It really depends on many factors. What type of music do you play?, what amp do you have?, what kind of guitars do you have?, and what pickups are in them?. Also, what kind of sound are you going for? Do you have a budget? 

Personally, I would never use MDF for a guitar speaker cabinet. I use 13 ply birch or maple void-free plywood, but if that's what you want to use, just remember that it's not a resonant material, and will absorb a lot of good vibrations.


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## hollowbody (Jan 15, 2008)

The concept of Q is basically how quickly your cab reacts to the vibrations Huff was talking about. 

The actual drivers in the cab are going to cause a lot of motion in there. A well built cab with a low Q value will react faster to these vibrations, so it won't lose much of it's ability to produce sound. Higher Q values mean the cabinet is slow to react to the vibrations and absorbs the sound too much. This can cause a loss of midrange, which especially for a guitar cab, is devastating. It'll end up being a muddy cab. Keep in mind Q only applies to sealed back designs.

Bottom line, you can't just slap 6 pieces of wood together and call it a cab. It will work, but it might sound like ass. You'll have to do some research into cab design before you buy and cut any wood. And yes, wood. 

MDF is fine to settle for if you find a nice cheap cab on the curb of your neighbour's house. But if you're going to go to the trouble of building your own, do yourself a favour and use marine birch or at least plywood.


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## Wild Bill (May 3, 2006)

I Huff Paint said:


> Personally, I would never use MDF for a guitar speaker cabinet. I use 13 ply birch or maple void-free plywood, but if that's what you want to use, just remember that it's not a resonant material, and will absorb a lot of good vibrations.


Actually, a lot of guys use MDF! It is an excellent material, except for one factor I'll get to in a minute.

The idea is that the wood is NOT supposed to be resonant! The big boogieman is voids. If you've ever looked at cheap plywood you might notice how there are often chunks missing in a layer or two. When there are a number of layers you don't have any holes showing right through but those empty spots might cause a resonance.

What does a resonance sound like? Booms, rattles or other noise at certain notes.

Voids can also suck away energy, particularly bass energy. The walls of a cab need to be stiff and rigid. A void area might leave the wood above or below it thin enough to vibrate with the sound. So you have energy being wasted in that vibration rather than coming out as moving air.

That's why the vintage masters used solid pine for their cabinets. It was the cheapest, readily available material that had no voids and was reasonably light yet strong.

As we came through the 1950's better and better plywoods were invented and they became more cost-effective. Solid pine then became more expensive. Worse yet, what we found in the lumber yards hadn't been dried for as long so the moisture content was much higher, increasing the weight and giving a tendency to warp.

So while construction grade plywoods are a bad choice the better stuff like 13 ply or Baltic Birch works very well! They're a lot more expensive but they work great.

MDF is made from fine sawdust sized particles, compressed in an epoxy glue. It has absolutely NO voids and is extremely rigid and strong! It also tends to be a bit cheaper. So acoustically it's a great choice. The problem is that it weighs a ton! What's more, have you ever tried to router that stuff? You have to really give the router bit time to cool off. I burned out two bits learning that!

So I would have no problem using MDF for a hifi cabinet, where it would be left in one place after I built it. I wouldn't use it for a guitar cab only because it's so damn heavy!

Guitar amp manufacturers have been using a cousin of MDF for decades called particle board. The particular type they use has no voids and is not that heavy. It works just fine but with one caution - don't get it wet! If you've ever had an older amp with ripped tolex get soaked in a basement flood you'll know what I mean.

Many of us would have seen cabs built from less common but gorgeous-looking hardwoods. As long as there are no voids pretty well any strong wood is ok. 

Actually, you don't even have to use wood! The 1950's was a time when building hifi speaker cabs was a common hobby. The magazines all had articles about cabs using clay sewer pipe, concrete and even paper mache!

JMHO

:food-smiley-004:


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## Mooh (Mar 7, 2007)

Wild Bill said:


> Actually, you don't even have to use wood! The 1950's was a time when building hifi speaker cabs was a common hobby. The magazines all had articles about cabs using clay sewer pipe, concrete and even paper mache!
> 
> JMHO
> 
> :food-smiley-004:


Nice post! Thanks.

I remember experimenting with tubular speaker cabs back in the '70s. We had some heavy cardboard/paper cheese barrels and old drum shells that could be made to sound _okay_ if they were braced stiff enough. We also tried odd shaped cabs to mount in the corners of rooms and against the ceiling, but the weird carpentry/joinery wasn't worth the lousy tonal results. If I remember correctly, the drum shells worked best, but there wasn't any high end.

I was reminded of all this last fall when there were scrap pieces of sewer pipe and water mains along my street. Heavy, stiff plastic of some sort. Wish I'd tried to bum some for subwoofers or something.

Peace, Mooh.


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## shoretyus (Jan 6, 2007)

It's funny that amp companies haven't graduated to plastic like the newer generation of P.A bins.... 

good post Bill. Leslies used Lumber core plywood right from the start.. solid wood with veneer on both sides.


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## dylanreimer (Nov 16, 2009)

alright, haha i have a peavey 5150 with a Esp Eclipse-II with EMG 81 and a 60. I play anything from metal to indie. So im going for a meaty sound with some nice mids. But i dont want my highs to suffer. And no i dont have any price range really. You see im seventeen so i will not buy it all at once haha. good Ebay finds is what im going on haha.


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## dylanreimer (Nov 16, 2009)

I Huff Paint said:


> Well, that's like asking "how long is a piece of string?". It really depends on many factors. What type of music do you play?, what amp do you have?, what kind of guitars do you have?, and what pickups are in them?. Also, what kind of sound are you going for? Do you have a budget?
> 
> Personally, I would never use MDF for a guitar speaker cabinet. I use 13 ply birch or maple void-free plywood, but if that's what you want to use, just remember that it's not a resonant material, and will absorb a lot of good vibrations.


alright, haha i have a peavey 5150 with a Esp Eclipse-II with EMG 81 and a 60. I play anything from metal to indie. So im going for a meaty sound with some nice mids. But i dont want my highs to suffer. And no i dont have any price range really. You see im seventeen so i will not buy it all at once haha. good Ebay finds is what im going on haha.


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## Lincoln (Jun 2, 2008)

Not sure if it's the right way to go or not but what I've been doing is making copies of a known good sounding cab rather than trying to re-invent the wheel. 
Want an open back single 12? Measure up a tweed deluxe. Want a 2-12 cab? Measure up a Messa Rectifier 2-12 cab and have at her.


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## Wild Bill (May 3, 2006)

Lincoln said:


> Not sure if it's the right way to go or not but what I've been doing is making copies of a known good sounding cab rather than trying to re-invent the wheel.
> Want an open back single 12? Measure up a tweed deluxe. Want a 2-12 cab? Measure up a Messa Rectifier 2-12 cab and have at her.


If it's just for guitar don't worry much. The dimensions are not critical at all. Worksmanship and rigidity are all that are really important.

It has to do with wavelengths. Regular guitar doesn't put out much below 100 cycles per second or so. The wavelengths are short enough at frequencies about that point that the cab just has to act as a frame to hold the speakers. The actual dimensions are too short to make any difference anyway. The only other factor would be closed back designs versus open backed ones.

Bass guitar, PA and hifi applications are quite different. The wavelengths of those frequencies below 100 hz are long enough that the dimensions of the cabinet DO matter! Things like ports and ducts are also used to improve the lower bass efficiencies. This is another reason why many modern smaller cabs are so inefficient with these applications and need so much extra power to drive them. There is just no substitute for a big box, if you'll pardon the expression!:smile:

:food-smiley-004:


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