Discussion in 'Amps and Cabs [BG]' started by gimp, Jan 28, 2013.

1. ### gimp

Jan 13, 2011
Catonsville, MD
I'm spit-balling building a cab, but I don't have a PC easily available to me. Could someone tell me the optimum internal volume and port size/length for an single 1x5 enclosure using the following speaker:

http://www.eminence.com/pdf/Legend_CA154.pdf

I know that bracing and the speaker will take up 10%.

(Full disclosure - this will be for a light(er) weight 2x15 build, but due to the wiring I plan on using, I want to put each speaker in its own ported enclosure in the same box).

Thanks!

3. ### gimp

Jan 13, 2011
Catonsville, MD
Nothing, other than the fact I didn't know they existed!

4. ### B-string

Eminence is good about supplying optimized plans for their drivers Your welcome
The software they have for download will have their driver specs also if you want to tweak.

5. ### gimp

Jan 13, 2011
Catonsville, MD
That is too awesome! Much appreciated.

6. ### gimp

Jan 13, 2011
Catonsville, MD
Making some notes for myself, but if anyone has any comments, feel free to chime in.

I'm looking at making a 2x15 that will actually be made up of two identical 1x15s. Each will have an angle taken out the back (on the top for a "towel bar" and the bottom for casters).

Looks like, based upon the "Med Vented Design" (http://www.eminence.com/pdf/Legend_CA154_cab.pdf) and using 1/2" ply for the sides and 3/4" for the baffle, I will get a cab with the following dimensions:

The math works out that the internal dimensions, not factoring in bracing or space for the driver, as follows.

Just the "cube" (interior): 25w x 20h x 14.75d = 7375 ci inches
The "triangle": 3.54 x 3.54 x 5 = 230.1 ci inches
Total volume: 7375 - 230.1 = 7144.9 ci inches

The spec sheet calls for a V(total) of 7046.8 ci inches.

Seems like that should work out pretty well.

Anyone care to comment?

7. ### B-string

I might suggest to increase the depth and reduce the width.

8. ### gimp

Jan 13, 2011
Catonsville, MD
I went with that width because I may end up using this cab with an Ampeg V4b head, and I wanted to keep it from looking too strange (Ampeg says their 8x10 is 26 x 48 x 16).

That being said, I'll have to remeasure. The internet shows the V4b at 27" wide.

9. ### B-string

Ah I see. Best to measure the head, I don't have mine any more, you may need additional depth for the head as well. Measure from the front to the back foot and add 1" minimum for the flat part of the depth.

10. ### gimp

Jan 13, 2011
Catonsville, MD
Good call. I'll measure when I get home tonight. Thanks!

Internet says:
Head Dimensions: 10 H x 26 5/8 W x 11 1/8 D inches

11. ### gimp

Jan 13, 2011
Catonsville, MD
In theory, if I wanted to make this an inch wider, I could just take a total inch out of the height and maintain the same volume (I think).

That being said, if the true goal here is to build a cab that is optimized for these speakers, should aesthetics be damned? Would having a narrower, but deeper cab have any impact on the sound, versus the wider, more shallow cab? All other things being equal.

12. ### will33

May 22, 2006
austin,tx
It will change the baffle step frequency and the reflection distance between the drivers and walls, which will change the overall "flavor" of your lowend/lowmids, even though the net box size stays the same.

13. ### gimp

Jan 13, 2011
Catonsville, MD
So, to follow up, which "flavor" is better?

14. ### B-string

Will33 points are valid. Better to shorten height and maintain depth. The old formula was 3X2X1 H X W X D

15. ### will33

May 22, 2006
austin,tx
Whichever one your ear likes best.

In general, the deeper cab will sound fuller than one that is very shallow front to back. Compromises are made all the time between absolute optimal and something that looks nice, or is of a shape that will fit in a car or is more easy to carry, etc. B-strings ratio is a good one, I've seen it expressed as .6/1/1.6. It has to do with making the internal box reflections not all line up at a certain frequency giving you a big notch or resonant boost at some frequency. That doesn't mean boxes that don't follow that "golden ratio" sound bad, people sound good playing them everyday.

16. ### gimp

Jan 13, 2011
Catonsville, MD
Thanks again to everyone! I wasn't trying too hard to reinvent the wheel. The overall depth (16") and width (26") were simply stolen from Ampeg's 8x10 dimensions, and then the height was calculated off the needs to meet the required internal volume.

As it's currently laid out, I should have plenty of room to line up the speakers vertically to one side, and ports on the other.

Either way, it's shaping up to be a cool project.