[GlibHarbinger]

I'm kind of in the early planning stages for a Tapped Horn using a 10 subwoofer and I'm hoping the folks here can help me with some advice about construction of the box:


The baffle will be 27.6 cm (10.87) across and the driver's cutout diameter is 23.5cm (9.25); this will leave 2.05cm (0.8) baffle on each side of the cut. Is that going to be enough material or is it a problem? The outside diameter of the driver mounting flange is 26.1cm and that leaves .75cm (0.29) overall clearance on each side.


The horn height at S3 is 17.79cm and (7) and the driver height is 15.3cm (6) so clearance here is about 2.49cm (1). At the closest point the clearance is 1.96cm (0.77). Is that cutting it too close?


The compression ratio is 4.27:1, (S2 = 85cm^2 Sd = 363cm^2) I've read in the forum that people are reluctant to go above 4:1. This is a paper cone driver...


Instead of bracing I'm considering routing a 3/4 x 1/8 groove in the longer boards and using a non-elastic epoxy to glue up 3/4 x 3/4 x 1/8 steel T bar most of the length of the long dimension for the boards that need it. This should create a resonance node and stiffen the board (steel has a much higher elasticity modulus than plywood and T bar is very stiff by virtue of its shape). Sound like a not so great idea?

Thanks for any and all help.

 

[Cerdic]



Quote:
Originally Posted by GlibHarbinger /forum/post/20779679



The baffle will be 27.6 cm (10.87) across and the driver's cutout diameter is 23.5cm (9.25); this will leave 2.05cm (0.8) baffle on each side of the cut. Is that going to be enough material or is it a problem? The outside diameter of the driver mounting flange is 26.1cm and that leaves .75cm (0.29) overall clearance on each side.

Should be fine. Once the baffle is glued in place on either side, it will be very rigid. You're screw holes won't be close enough to the edge to worry about splitting, especially if you're using plywood. The only tough thing might be installation if you are going to put in a "hatch" for driver access, but if you're adding the driver as you build it (permanent installation) it should be a piece of cake.

 

[noah katz]



Quote:
Originally Posted by Cerdic /forum/post/20780017


...if you're adding the driver as you build it (permanent installation) ...

a really bad idea

 

[GlibHarbinger]



Quote:
Originally Posted by Cerdic /forum/post/20780017


Should be fine. Once the baffle is glued in place on either side, it will be very rigid. You're screw holes won't be close enough to the edge to worry about splitting, especially if you're using plywood. The only tough thing might be installation if you are going to put in a "hatch" for driver access, but if you're adding the driver as you build it (permanent installation) it should be a piece of cake.

I'll be putting in an access panel. I'd like to be able to get at/replace the driver if necessary without tearing apart the box.

 

[Oklahoma Wolf]



Quote:
Originally Posted by GlibHarbinger /forum/post/20779679


The compression ratio is 4.27:1, (S2 = 85cm^2 Sd = 363cm^2) I've read in the forum that people are reluctant to go above 4:1. This is a paper cone driver...

Depends on the driver. Some can take it, some can't. I've only gone as high as 3.2:1 in the case of the Tang Band W8Q-1071F I used in my first TH design. Haven't tried any at 4:1 yet, mostly because I can't afford to screw up and start killing drivers in these big designs I keep coming up with.

 

[GlibHarbinger]



Quote:
Originally Posted by Oklahoma Wolf /forum/post/20780368


Depends on the driver. Some can take it, some can't. I've only gone as high as 3.2:1 in the case of the Tang Band W8Q-1071F I used in my first TH design. Haven't tried any at 4:1 yet, mostly because I can't afford to screw up and start killing drivers in these big designs I keep coming up with.

I hear ya!


I get the impression that no one really knows the limits for this and with no manufacturer data about how to "strong" the drivers are it's kind of a crap shoot.


Given that, I'm guessing everyone is being pretty conservative about compression numbers.