Building a Speaker Cab

Andywragg · 12-19-2009, 05:05 PM

Hi,

My Bandit has a 100w 8 Ohm output on the back. How would I go about building a cab for a larger or more powerful speaker? What would I need to be aware of? Should I use 2 speakers instead of 1 and what effect does this have? Could I use 2 lower powered ( say 60W) cones instead of one big one? What impedance would they have to be for a double and how to connect them?

Cheers

Andy

Dusty · 12-19-2009, 05:32 PM

Andy, there are a couple of things you need to decide upon because you have choices.
Some like a large single speaker that handles the capacity such as a 15 inch speaker. Others prefer two or four ten or 12 inch speakers in a cab.
With two plus speakers it will take up more room and be more difficult to transport.

Will you want the cab to be sealed or open? It is a personal choice thing. Some will sing the praises of open and some will sing those of sealed cabs. There really is no difference in sound.
I prefer sealed cabs because of the damage I have seen happen to loudspeakers, yet many amps are open backed and the speakers seem to escape most damage.
Dimensions of sealed cabs is critcal, whereas the size of an open back cab can be almost anything you want.
From my experience, pine /partical board is not the best material. Solid timber, ply wood or craft wood is preferred. My choice for durability and cost is 18mm plywood.
I find craft wood and particle board too heavy , and although I havent experienced it, I read that particle board can disintergrate with vibration over the years. And dont have a damp basement with particle board as it will fall apart.
I think I posted some speaker cab dimensions, but happy to email them to you if you can' t find the post.
Oh, cost can determine the size of speakers. Often you can buy two 12 inch speakers cheaper than you would pay for one 15 inch loud speaker.
Best if you match the impedence to your amp out put. Needs to be determined before you buy the speakers.
No harm in having a cab capable of more watts than your amp, just a long as it is not underpowered.
When you are ready we can assist with connecting it up. It's no biggie unless you screw it up.
For a relatively small cost you can make a 2 x 12 " cab that can handle 120 watts. Any higher wattage starts to put the price of the speakers way up.
Speaker brands are not really all that important. I prefer Celestions as they in my Vox, others will argue JBL or another brand. The most important thing is to try and match the speakers as closely as possible if there is more than one.

Improbable Joe · 12-19-2009, 05:36 PM

Before building your own, you should check out Earcandy cabs .com

They make a lot of sweet speaker enclosures with the sort of custom appointments that might be prohibitively expensive for you to do yourself.

Andywragg · 12-20-2009, 03:59 PM

Cheers Dusty,

So if I get 2 x 12" 16 ohm cones and wire them in parallel, I'll get 8 ohms load? Right?

What about the speaker Watts rating? Do I need each cone to be more than the amps rated power (100w in this case) for or is this cumualtive? for instance 2 x 60w speakers.

And WTF does modern with a touch of English mean?

BTW
ImprobableJoe, If you handnt guessed by my profile summary, I'm in the UK and getting a custom cab made in the US to get delivered here is probably gonna cost more than a valve amp header and matching cab from my local supplier.

boyda · 12-20-2009, 05:35 PM

Quote:

Originally Posted by Andywragg

Cheers Dusty,

So if I get 2 x 12" 16 ohm cones and wire them in parallel, I'll get 8 ohms load? Right?

What about the speaker Watts rating? Do I need each cone to be more than the amps rated power (100w in this case) for or is this cumualtive? for instance 2 x 60w speakers.

First, think of speakers as noise emitting resistors. So 2 16 ohm resistors in parallel would give you 8 ohms equivalent resistance.

On the second question, I think that you can just use 2 60w speakers. As long as you're not dissipating more than 60w across a single speaker, it should work all well and fine. I'd check with Dusty or LATS on this one though.

calgary1 · 12-20-2009, 06:41 PM

Here is an interesting primer. Speaker cabinets

Andywragg · 12-20-2009, 08:48 PM

Thanks for that Cal, interesting stuff.

I have a local supplier where I can get 2 Jensen CH 12/70 cones for less than a ton (£100). I'm going to compare timber prices and have a look on ebay to see what the going rate is for a 2 x 12 mono cab capable of 140watts.

The speaker is described as Modern with a touch of English. I have no idea what this means, but apparently 4 of these in a sealed cab gives the classic Marshall tone.

I'll probably go with open backed, as this is what my bandit already has.

Improbable Joe · 12-20-2009, 09:50 PM

Quote:

Originally Posted by Andywragg

BTW
ImprobableJoe, If you handnt guessed by my profile summary, I'm in the UK and getting a custom cab made in the US to get delivered here is probably gonna cost more than a valve amp header and matching cab from my local supplier.

That was sort of dumb of me... sorry. I'd be surprised if there isn't a UK outfit providing the same service though.

Dusty · 12-20-2009, 09:52 PM

Andy you cant crank more out of speakers than their rating. You need to ideally have both speakers with a wattage higher than the amp out put. If your amp is rated at 100 watts, two 16 ohm speakers connected in parallel both need to be at least 100 watts each.

Correct, two 16's in parallel gets you near enough to 8 ohms.
If you were thinking four speakers, dont wire them all in parallel as that will drop too far below the amp's capacity if it's rated at 8 ohms. You can wire them in series/parallel to overcome the problem.
A pair of 100 watt speakers should handle an amp with 100 watt output. To be honest, I can't think of anywhere most people could wind an amp up to 10 on the volume scale, so peak watts will never likely be used.
Check out Ebay. Thgere are often good deals on loudspeakers.
Also look at stuffed cabs that have had a battering. Often they contain very good speakers in perfect nick and you can buy them cheaply because the cab does not look pretty.
In Oz a sheet of 18mm 1200 x 1200mm ply costs around $45 One sheet will make one cab with a bit of spare.
Most timber mechants will cut your timber to size. Cutting up a sheet here is $10.
Do not forget you need 20mm x 20mm bracing strips for all corners, and they should be both glued and screwed.
Tolllex and speaker cloth can be obtained cheaply on Ebay, though many use carpet. You can even buy the old Vox brown diamond patterned cloth and the logos, plus genuine corners and handles

Andywragg · 12-20-2009, 10:12 PM

I'm playing around in my head at the minute. dangerous eh?

I'm thinking of building a 2 x 12 cab with a watts rating in excess of 100 watts. That would allow me to use a dedicated 100w valve head when the time comes.

If I buy a 8 X 4 sheet of 3/4" ply I can potentially make 4 cabs. I'd get 8 strips of 12" wide (ish) ply out of it and then get a side and a top/bottom out of a strip.

I'd then need a sheet of 1/2" ply to mount the speakers onto and use as joint reinforcement material.

Sell the 3 I dont need on ebay and I could probably cover my timber costs.

As for the speakers issue. I have seen information elsewhere this evening to suggest I can run 2 x 16 ohm 70s together in parallel to give me an 8 ohm 140 watts capable cab. Is the other info incorrect?

Thanks for all the help guys

Andy

12-19-2009, 05:05 PM	#1 (permalink)
Andywragg I now have stupid fingers Join Date: Jul 2009 Location: Sheffield, UK Posts: 452	Building a Speaker Cab Hi, My Bandit has a 100w 8 Ohm output on the back. How would I go about building a cab for a larger or more powerful speaker? What would I need to be aware of? Should I use 2 speakers instead of 1 and what effect does this have? Could I use 2 lower powered ( say 60W) cones instead of one big one? What impedance would they have to be for a double and how to connect them? Cheers Andy

12-19-2009, 05:32 PM	#2 (permalink)
Dusty Senior Member Join Date: Nov 2008 Location: Mollymook, Australia Posts: 5,468	Andy, there are a couple of things you need to decide upon because you have choices. Some like a large single speaker that handles the capacity such as a 15 inch speaker. Others prefer two or four ten or 12 inch speakers in a cab. With two plus speakers it will take up more room and be more difficult to transport. Will you want the cab to be sealed or open? It is a personal choice thing. Some will sing the praises of open and some will sing those of sealed cabs. There really is no difference in sound. I prefer sealed cabs because of the damage I have seen happen to loudspeakers, yet many amps are open backed and the speakers seem to escape most damage. Dimensions of sealed cabs is critcal, whereas the size of an open back cab can be almost anything you want. From my experience, pine /partical board is not the best material. Solid timber, ply wood or craft wood is preferred. My choice for durability and cost is 18mm plywood. I find craft wood and particle board too heavy , and although I havent experienced it, I read that particle board can disintergrate with vibration over the years. And dont have a damp basement with particle board as it will fall apart. I think I posted some speaker cab dimensions, but happy to email them to you if you can' t find the post. Oh, cost can determine the size of speakers. Often you can buy two 12 inch speakers cheaper than you would pay for one 15 inch loud speaker. Best if you match the impedence to your amp out put. Needs to be determined before you buy the speakers. No harm in having a cab capable of more watts than your amp, just a long as it is not underpowered. When you are ready we can assist with connecting it up. It's no biggie unless you screw it up. For a relatively small cost you can make a 2 x 12 " cab that can handle 120 watts. Any higher wattage starts to put the price of the speakers way up. Speaker brands are not really all that important. I prefer Celestions as they in my Vox, others will argue JBL or another brand. The most important thing is to try and match the speakers as closely as possible if there is more than one. __________________ James "Meditate on this, I will." ―Yoda The older I get, the better I was. www.ridpest.com.au Blog www.blog.ridpest.com.au Last edited by Dusty; 12-19-2009 at 05:36 PM.

12-20-2009, 09:52 PM	#9 (permalink)
Dusty Senior Member Join Date: Nov 2008 Location: Mollymook, Australia Posts: 5,468	Andy you cant crank more out of speakers than their rating. You need to ideally have both speakers with a wattage higher than the amp out put. If your amp is rated at 100 watts, two 16 ohm speakers connected in parallel both need to be at least 100 watts each. Correct, two 16's in parallel gets you near enough to 8 ohms. If you were thinking four speakers, dont wire them all in parallel as that will drop too far below the amp's capacity if it's rated at 8 ohms. You can wire them in series/parallel to overcome the problem. A pair of 100 watt speakers should handle an amp with 100 watt output. To be honest, I can't think of anywhere most people could wind an amp up to 10 on the volume scale, so peak watts will never likely be used. Check out Ebay. Thgere are often good deals on loudspeakers. Also look at stuffed cabs that have had a battering. Often they contain very good speakers in perfect nick and you can buy them cheaply because the cab does not look pretty. In Oz a sheet of 18mm 1200 x 1200mm ply costs around $45 One sheet will make one cab with a bit of spare. Most timber mechants will cut your timber to size. Cutting up a sheet here is $10. Do not forget you need 20mm x 20mm bracing strips for all corners, and they should be both glued and screwed. Tolllex and speaker cloth can be obtained cheaply on Ebay, though many use carpet. You can even buy the old Vox brown diamond patterned cloth and the logos, plus genuine corners and handles __________________ James "Meditate on this, I will." ―Yoda The older I get, the better I was. www.ridpest.com.au Blog www.blog.ridpest.com.au Last edited by Dusty; 12-20-2009 at 10:03 PM.

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12-19-2009, 05:36 PM	#3 (permalink)
Improbable Joe Banned Join Date: Jul 2009 Posts: 1,986	Before building your own, you should check out Earcandy cabs .com They make a lot of sweet speaker enclosures with the sort of custom appointments that might be prohibitively expensive for you to do yourself.

12-20-2009, 03:59 PM	#4 (permalink)
Andywragg I now have stupid fingers Join Date: Jul 2009 Location: Sheffield, UK Posts: 452	Cheers Dusty, So if I get 2 x 12" 16 ohm cones and wire them in parallel, I'll get 8 ohms load? Right? What about the speaker Watts rating? Do I need each cone to be more than the amps rated power (100w in this case) for or is this cumualtive? for instance 2 x 60w speakers. And WTF does modern with a touch of English mean? BTW ImprobableJoe, If you handnt guessed by my profile summary, I'm in the UK and getting a custom cab made in the US to get delivered here is probably gonna cost more than a valve amp header and matching cab from my local supplier.

12-20-2009, 06:41 PM	#6 (permalink)
calgary1 Banned Join Date: Mar 2009 Posts: 7,390	Here is an interesting primer. Speaker cabinets

12-20-2009, 08:48 PM	#7 (permalink)
Andywragg I now have stupid fingers Join Date: Jul 2009 Location: Sheffield, UK Posts: 452	Thanks for that Cal, interesting stuff. I have a local supplier where I can get 2 Jensen CH 12/70 cones for less than a ton (£100). I'm going to compare timber prices and have a look on ebay to see what the going rate is for a 2 x 12 mono cab capable of 140watts. The speaker is described as Modern with a touch of English. I have no idea what this means, but apparently 4 of these in a sealed cab gives the classic Marshall tone. I'll probably go with open backed, as this is what my bandit already has.

12-20-2009, 10:12 PM	#10 (permalink)
Andywragg I now have stupid fingers Join Date: Jul 2009 Location: Sheffield, UK Posts: 452	I'm playing around in my head at the minute. dangerous eh? I'm thinking of building a 2 x 12 cab with a watts rating in excess of 100 watts. That would allow me to use a dedicated 100w valve head when the time comes. If I buy a 8 X 4 sheet of 3/4" ply I can potentially make 4 cabs. I'd get 8 strips of 12" wide (ish) ply out of it and then get a side and a top/bottom out of a strip. I'd then need a sheet of 1/2" ply to mount the speakers onto and use as joint reinforcement material. Sell the 3 I dont need on ebay and I could probably cover my timber costs. As for the speakers issue. I have seen information elsewhere this evening to suggest I can run 2 x 16 ohm 70s together in parallel to give me an 8 ohm 140 watts capable cab. Is the other info incorrect? Thanks for all the help guys Andy