My Stillborn Plan for a DIY Speaker Cab

[Lt. Bob]

I don't think you need to be so worried about efficiency unless you're gonna try pushing them with a Valve Jr or something flea powered like that.
With that many speakers, you're gonna move some air. I don't think you need that many .... one of the best bass cabs I ever heard had only 8-8's in it. Probably you should try 10 or 12 of the little 4's first.

 

[32-20-Blues]

I don't think you need to be so worried about efficiency unless you're gonna try pushing them with a Valve Jr or something flea powered like that.

See 4 posts up.

 

[Zaphod B]

I don't think you need to be so worried about efficiency unless you're gonna try pushing them with a Valve Jr or something flea powered like that.
With that many speakers, you're gonna move some air. I don't think you need that many .... one of the best bass cabs I ever heard had only 8-8's in it. Probably you should try 10 or 12 of the little 4's first.

Good point, Lt. Bob.

The reason I was concerned about the efficiency for a working rig was that inefficient speakers, on the order of 83 - 84dB, are enormous power soaks compared to more efficient speakers, and you have to drive much more wattage into them to get equivalent volume levels, then you have to worry about power handling of all those teeny things......

But now I'm thinking more in terms of proof-of-concept.

I hadn't put the calculator to it yet, but here are some rough figures. Let's say that the area of a 12" speaker would be about 128 sq inches, and the area of a 4" speaker is about 13 square inches. You'd need 10 4" speakers to match the cone area of a 12" speaker. To duplicate a 4X12 cab you'd need 40. I guess it depends on how much air you want to move.

 

[Zaphod B]

Okay, I'm going to get working on it too. If I run into problems, guess who I'll be PMing? I don't yet know how to solder, but I have a pretty reasonable grasp of physics, so I hope it'll work out. I'm planning on using my Epi Valve Junior on this, so I'm going to get out the calculator and mess around with some numbers. Any speakers will do, can't wait to get this started.

Very cool!

And don't worry about the efficiency part of it. It just means that your 5-watt Valve Jr. isn't going to get you as much volume as it would being played through a regular guitar cab.

 

[alien]

actually, the idea has been used before

I remember seeing a set of speakers for sale in a used store in Nashville, TN a while back.

It had around 30 4" drivers with four 10" drivers up the middle of the bottom half. There was a horn in the top (probably an old Foster version). Can't remember the make or model, but they lookd alot cooler than they sounded.

 

[Zaphod B]

actually, the idea has been used before

I remember seeing a set of speakers for sale in a used store in Nashville, TN a while back.

It had around 30 4" drivers with four 10" drivers up the middle of the bottom half. There was a horn in the top (probably an old Foster version). Can't remember the make or model, but they lookd alot cooler than they sounded.

Right. You're talking about a three-way cab with a crossover. I'm not envisioning any crossover, thus the need for full-range speakers.

.

 

[Lt. Bob]

See 4 posts up.

uh-oh! oops

Actually I have a Valve Jr. and I think it's an awesome amp so I promise I'm not dissing your amp!


But I think with all the voice coils and all 5 watts may be too little. Still, technically there's no reason it wouldn't work.

 

[Zaphod B]

Here's the kind of speaker I was originally thinking of.

It's a 3" full range, linear down to 100Hz and -3dB at 80Hz, and fairly linear on-axis to about 10K, if I'm reading the fuzzy spec sheet right.

Sensitivity, though, is very low at 81dB. It costs $9.95 and I think you'd need about 12 or 13 of them to get the equivalent cone area of a single 12" driver.

Edit: it can actually handle 15W.

Imagine a box with about 50 of these little fuckers:

 

[Lt. Bob]

looks like a neat little speaker ..... where do you get those?

Hmmmm .... well, isn't one of the reasons for using multiple speakers to offset speaker inefficiencies? I may be wrong but it seems like you'd get more sound out of ten of those than you would out of a single 12 of identical efficiency.
At least intuitively it seems like you would ....... but intuition is often wrong.

 

[Zaphod B]

looks like a neat little speaker ..... where do you get those?

Hmmmm .... well, isn't one of the reasons for using multiple speakers to offset speaker inefficiencies? I may be wrong but it seems like you'd get more sound out of ten of those than you would out of a single 12 of identical efficiency.
At least intuitively it seems like you would ....... but intuition is often wrong.

You can buy this speaker and others like it at Madisound:

http://www.madisound.com

That particular driver is a Hi-Vi Research model B3N.

I see your point about multiple, less efficient speakers adding up to a high efficiency system. But I don't think it works that way. Don't forget that you are dividing power evenly between all the drivers in a system like this, so the overall system efficiency can't increase beyond that of a single driver, driven by the same power level. I don't think.

 

[travelin travis]

I think the increased coverage of multiple drivers will appear to be louder over a single speaker.

 

[Zaphod B]

I think the increased coverage of multiple drivers will appear to be louder over a single speaker.

I think you're right, and it may just be that the sound stage is larger.

 

[travelin travis]

I think you're right, and it may just be that the sound stage is larger.

what sound stage? it's a guitar amp.

 

[Zaphod B]

what sound stage? it's a guitar amp.

You're really pushing it, bubba. Don't make me come over there!

.

 

[Mr. C]

This thread got me thinking. I know that I have some small speakers laying around here somewhere from some old cheap stereos, and I do think they are around 4". I have no clue about this efficiency stuff, or how to even find out what the efficiency of a speaker is...but it does sound cool to take a bunch of these and put them together for an extension cab. I have a Classic 30 to drive them. Oh, and one other drawback, I'm horrible at soldering, but maybe I could practice to get better.

 

[Zaphod B]

This thread got me thinking. I know that I have some small speakers laying around here somewhere from some old cheap stereos, and I do think they are around 4". I have no clue about this efficiency stuff, or how to even find out what the efficiency of a speaker is...but it does sound cool to take a bunch of these and put them together for an extension cab. I have a Classic 30 to drive them. Oh, and one other drawback, I'm horrible at soldering, but maybe I could practice to get better.

Sounds like a perfect excuse to perfect your soldering technique!

(Hints: Let the soldering iron get nice and hot. Brush rosin on the surfaces that will be soldered. Attach those surfaces together. Apply hot soldering gun. When rosin starts smoking, for a few seconds - don't breathe this stuff - apply solder to joint. A little dab'll do ya. )

 

[NRS]

I know exactly what you need.......

5" Galaxy Audio Hot Spot moniter replacement speakers: At 100watts RMS (200 max) and a 95db efficiancy rating they are meant to handle stage applications and sound perfect for what your trying to do. Although they're not exactly as dirt cheap as the small computer or home stereo speakers you mentioned, it might cost you about the same anyway since you'll need far less of them to achieve your same objective and I'll bet they'll sound much better too. They're full range though (150hz to 18000) so if your using them for guitar you may need the proper capacitors to roll off the top end down to around the typical 4-6khz roll off level of an average guitar speaker. Might be cool to leave full range with a modeler that has a cab sim though or maybe your EQ settings alone could do the trick.

CLICK: GALAXY AUDIO S5N-8 5" NEODYMIUM FULL RANGE DRIVER