Advice on building a cab please.

[machinehead]

I'm not sure if this is the correct forum for this? Maybe technical?

Anyway....I've ordered one of Alex's Compact cabs which I will use with my LMII.

For rehearsals and small pub gigs I've been using my Markbass 121 combo. It has it's obvious limitations due I think, to the small box size. Before I ordered the Compact I was planning to buy a Markbass 121 extension cab and use it paired to the MB combo for medium gigs. These little cabs now cost around the £500 mark which is too painful for me for what it is and I much prefer to go with the Compact.

So now I'm thinking about just building a 12" cab to match the MB combo. This is as much about me learning how to build a cab as it is about saving money. And really, if I have the Compact I might never gig the Markbass combo again other than in a very tiny pub where even the compact is taking up too much space. I can think of only one pub we play where this applies. It is perfect for rehearsals though because I have to carry my gear up steep stairs to the room.

So, after that long-winded introduction here are my questions:

1. What speaker should I buy to best match the Markbass B&C speaker in the combo?
2. Would this be successful if I simply copied the dimensions of the combo, including the rear port? (By this I mean would the two similar sized boxes be a decent balanced match?)
3. Roughly what sort of results should I expect by adding another 12", similar sized cab to the 121 combo? More volume? Deeper sound? That is what I am hoping for.
4. Finally, would building this cab be worth the effort based on the expected returns, sound and volume wise bearing in mind I will also have a Compact cab. I'm hoping the responses to this thread will help me decide this.

Thanks for any advice offered and please don't limit replies to answering my questions. All other relevent points will be listened too very carefully.
Tell me it's a waste of time and money if you think so.

Frank

[alexclaber]

Well I should have the first of the Midgets done by the end of June if you'd like an easy solution!

Alex

[stevie]

[quote name='machinehead' post='484385' date='May 10 2009, 04:52 PM']So, after that long-winded introduction here are my questions:
1. What speaker should I buy to best match the Markbass B&C speaker in the combo?
2. Would this be successful if I simply copied the dimensions of the combo, including the rear port? (By this I mean would the two similar sized boxes be a decent balanced match?)
3. Roughly what sort of results should I expect by adding another 12", similar sized cab to the 121 combo? More volume? Deeper sound? That is what I am hoping for.
4. Finally, would building this cab be worth the effort based on the expected returns, sound and volume wise bearing in mind I will also have a Compact cab. I'm hoping the responses to this thread will help me decide this.[/quote]

1. The best match would probably be the same one that’s already in the Markbass cab you have. You’re unlikely to be able to get hold of one though. Even if they are using a standard B&C driver, it will have a different model number because of the different colour cone. The only way of finding out for sure would be to measure the speaker parameters, something that requires specialist equipment. It might be worth looking inside the cab just in case you can deduce what speaker is in there. B&C drivers are not cheap, however. A 400-watt neodymium 12” from B&C will cost you around £150.

2. Yes, that would be a reasonable plan. Even if you can’t get the identical driver, you should be able to find something that works reasonably well in what looks like a 35-litre box. There are a few Celestion 12s that would fit the bill. The two Green label bass speakers look OK for the purpose – the BL12-200X (ferrite magnet) and the BN12-300X (neo magnet). As there is only 1kg difference in the weight, you might want to save money by opting for the ferrite magnet one. The power handling difference will not be an issue in practice.

3. You’ll get more volume and an impression of more bass. Depending on what you have at the moment (I'm not really familiar with it), the combination of the two may well go lower.

4. The driver will cost you something in the region of £70. You could always knock a cabinet up in half-inch chipboard and No More Nails glue from B&Q just to try it and get a feel for what you need to do should you decide to build a proper cab (15mm birch ply would be good). Total cost with the wood will be around £120, depending on how you finish it. Certainly worth a go, I’d say.
However, it’s quite possible you won’t need another cab when you get your Compact, as you’ll have two already. It's a decision that you have to make yourself. But as a project for familiarizing yourself with speaker building, it's probably a good one. You might like to download and check out the freeware WinISD software to model what you are doing.

Edited May 11, 2009 by stevie

[machinehead]

Thanks for taking the time to write a very detailed reply Stevie.

I will try to identify the speaker in the Markbass. My guess was right that I would be best to buy a speaker as close to the Markbass one as possible.
I want to buy the best speaker for the job rather than save money so I'll research it well before buying. Just a thought, is it possible to buy a speaker that is too good for the Markbass one and overpower it giving a worse result?

I'm in a fortunate position of being able to get decent plywood free so I would plan to build the box as close to the Markbass box, to a decent standard and as professional looking as I can manage on my first attempt.

Alex. I am certain that the Midget will be far superior to anything I build but I want to get the box dimensions and general appearance the same as the combo. Also, I quite fancy this project just to hear the results and maybe learn something in the process. Still, I might end up with a Midget if I make a total balls of building a cab myself,which is a real possibilty.

Frank