Speaker cab design?

Marty Forrer · #1 10-31-2010, 03:25 PM

I'm rebuilding the cab for my 12" speaker so it sits under my GB shuttle 3.0 combo better, and is smaller and lighter. Does anyone have links or thoughts on the porting for a micro cab? My initial thoughts are to port it the same way as the shuttle, which is two triangular ports at the rear of the cab. Another possibility is no porting at all.

Ric Vice · #2 10-31-2010, 04:31 PM

Quote:

Originally Posted by Marty Forrer

I'm rebuilding the cab for my 12" speaker so it sits under my GB shuttle 3.0 combo better, and is smaller and lighter. Does anyone have links or thoughts on the porting for a micro cab? My initial thoughts are to port it the same way as the shuttle, which is two triangular ports at the rear of the cab. Another possibility is no porting at all.

Marty,
Now , I'm not a speaker builder, but my favorite cabinet of all time is the Portaflex that Ampeg built in the early sixties. There was a 12" version of that cabinet that sat under the B12 and SB12, very different than the GB but very efficient. The one thing I wouldn't go with is a totally sealed box. The Gentz Benz does work really well though.

fdeck · #3 10-31-2010, 05:01 PM

I've got some documents at my little web page about compact speaker design, including one on my lightweight 12" box.

Most contemporary musical instrument drivers appear to be designed for ported use. If it turns out that your existing driver is unsuitable, the Eminence BassLite drivers are of good quality and quite affordable.

Marty Forrer · #4 10-31-2010, 06:18 PM

Thanks Fdeck, my head hurts, but very interesting.

fdeck · #5 10-31-2010, 07:56 PM

I have to admit that the theory stuff was meant as an academic exercise for myself -- to see if this stuff could be figured out. The article on the actual speaker is probably more useful.

jon3673 · #6 11-08-2010, 07:46 AM

Marty,
Although I've now stopped using it and have gone off in an entirely different direction, when they first came out I was very pleased using a GB Shuttle 3.0 to drive a Gallien-Krueger 112MBX Metal Extension Cab. I used this cabinet because it was physically smaller, but gave great response. In fact, I mounted the Shuttle on the top of the cabinet and installed a mounting unit with wheels, similar to a luggage carrier, which made a very small and portable unit. It responded great with my 5 string upright.
Also, as it is an all metal enclosure, it will take the punishment of moving around a lot.
Jon

Matthijs · #7 11-08-2010, 08:25 AM

Isn't the 112mbx a sealed cab? If you don't mind running the risk of doing it all over again you might try a sealed cab first. I think all those small Gallien and Kruegers are sealed, and a lot of DB'ers like that sound. A sealed cab is less efficient in the low frequencies, but the cut off of those frequencies is less abrupt. This works quite welll for most traditional amplified DB tones. Also, you need fewer calculations for a sealed cab, it's a pretty straightforward trade off: smaller is less bass, but will handle more power before x-maxing, bigger is other way around. So: build a cab at the maximum size you're willing to carry around and see if you like it.

If you want it ported you should calculate the ports on the exact specifications of your 12" speaker and on the frequnecy response you want. Ideally you'd want it to correspond with the gb 3.0 cab, to get the most out of the combination, but it will be difficult to guestimate a good match. Wether the ports are triangular, round, or on the backside doesn't really matter. It might be practical to use a standard tuneable port from the shop. This allows you to adapt the port afterwards.

Marty Forrer · #8 11-09-2010, 06:49 PM

I made the new cab. Because I play slab as well, I ported it in the same style as the Shuttle cab, but slightly bigger because of the 12" speaker. I did a DB gig the other night and it worked well. A friend who I gig with a lot remarked that the DB sounded very clear and punchy. I'm a happy camper.