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215 Cab Build Question?

Vincent P

Vincent P

Jul 13, 2007
1,140
11
Toronto Ontario, Canada
#1
Hello all,

Don't know if this is the correct place to ask this question, and if it is'nt then moderators, could you please move it to the right forum.

Started 215 cab build with my son this weekend, to house a couple of Eminence speakers I had laying around the garage; see attached images. Dimensions were copied from the Mesa Boogie 215; 36 3/4 H x 24 1/2 W x 19 3/4 D.

Question: Should I insulate the inside?

Thanks for any input, or suggestions.
 

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#2
Yes. you will need to tame the midrange frequencies from bouncing around inside the cab. If you don't it could sound boomy.

Something you should think about is that all speakers don't like to play nicely in the same size box. There are free programs you can download and enter the TS parameters to determine the right size cabinet and tuning frequency (port dia and length).

WinISD is a good one, http://www.linearteam.dk/

What Eminence drivers are you using? I can do a sim for you.

Tedward
 
#6
According to winISD the LEGEND CB158 in an 8 cubic ft box with the ports you have (looks like 3"D x .75L) will have an f3 of 54.98 HZ with a 2.64 db peak at 84.19 HZ. A 3 db increase is twice as loud. Nothing wrong with this. Just for fun and a learning experience try four 3.5" long ports and see how the sound changes. Your f3 will be lowered to 54.09HZ and the peak at 84.19HZ will be gone. This change will flatten out the response and give you more of HI FI sound or studio sound. Some people like it and some don't. I'm just offering some food for thought. Either way it will sound awesome. Tedward
 
#8
Use cardboard mailing tube or PVC pipe to port that thing. Use winISD to calculate the tuning, somewhere between 40 and 50hz. Make all 4 ports the same length. Line the inside with insulation or quilt batting and it will sound good. The Legend CB15's are pretty forgiving towards various box sizes and tunings, as long as you're in the ballpark. Need to add some crossbracing in there to, to tie together opposing panels and stiffen it up.
 
#9
Very nice! And quite similar to the TL606 design. I built the TL606 (2x15) with only a baffle brace (mostly to separate the individuals drivers a bit). The 3/4" plywood should be stiff enough... I've run an SVT V-9 wide through mine with Eminence Kappa series (ceramic) with no panel vibrations to speak of. I lined all interior panels (except the baffle) with Radio Shack's "speaker fiberglass." It's not as packed as rigid fiberglass, but not as loose as the pink stuff you put in the wall of your house... As HM said, it sounds EPIC!
 
#11
Good advice above. Your build will also benefit from more cross bracing, and it doesn't have to be a 2x4--leftover strips of plywood work fine. I'd put in at least one top to bottom, two side to side and one front to back and glue them together where they intersect. All the ply braces will be about the same total weight as the 2x4, which I'd remove.
 
#13
::::BASSIST:::: said:
Yeah, if you add some bracing it will definitely enhance the sound. 1.5 x .5 x (your internal dimensions) of ply should do it. Check the greenboy website for visuals of how its done right. Also 2 inch deep of poly batting (etc) will help make it sound better as well.
Click to expand...
Well, greenboy's bracing is good, but he uses splines glued to the face of each panel, and I like cross bracing, but I'm no engineer. It just seems to do what's needed with the least weight and fuss.
 
#14
bobcruz said:
Well, greenboy's bracing is good, but he uses splines glued to the face of each panel, and I like cross bracing, but I'm no engineer. It just seems to do what's needed with the least weight and fuss.
Click to expand...

The crossbracing provides the strongest result with the least amount of wood, but, you can't always put a crossbrace where you need one. Can't glue them to the backs of magnets or handle cups for example, so oftentimes, a combination of the 2 is the best solution. The splines are strong if you make them wider and then swisscheese them than if you use a narrower, solid spline.

I've done it both ways and the combo way. The spline only way works, but makes the cab heavier than it needs to be if you went the crossbrace way and ended up at the same stiffness. No hard numbers to back that up there but it's pretty obvious just from working with the wood, trying to make it flex, etc. I put splines on the back side of my baffles where say a driver hole and a port hole are close together. Maybe put splines on the back wall behind the driver magnets and then crossbraces from between the driver cutouts to the back wall.
 
#15
Attach the cross braces to the splines.
Swiss-cheese the cross braces if you have time and patience to burn.

I suggest building one cross brace and weighing it.
Add the holes, weigh again.
See if the return on investment is worth the investment.

The length of the cross braces can be less than perfect accuracy because gluing to the splines allows for a lot of slop.
 

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