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  Topic Review (Newest First)
01-21-12 06:06 PM
Re: Looking for driver and general sub advice

I finally started building this thing. The inside front is routed and has t-nuts installed and is glued to the bottom. I've started on the vertical divider.

Should I start a build thread, or is someone going to move this thread?
01-18-12 04:20 PM
Mike P.
Re: Looking for driver and general sub advice

Angling the ports is fine. The Bash 300 has a 17.7 hz HPF, adjust the tuning frequency in your modeling to get the most benefit from it.

01-18-12 03:26 PM
Re: Looking for driver and general sub advice

I don't have time to do a whole new SketchUp drawing of the 4" port design, but here are some screenshots to give an idea of my current plan. Instead of bending the ports to move the internal ends at least 4" from anything, I think it will be easier and maybe better to just angle the port. I think it will only take about 7 degrees. There will be horizontal bracing and cross bracing similar to what was in the previous, 6" design.
Does it seem okay?
01-18-12 07:49 AM
Re: Looking for driver and general sub advice

I made limited progress on my sub build last weekend. I did buy plywood and some hardware and glue. I couldn't get 6" PVC at the local big box store, only 4" and smaller. Later found it for about $60 (have to buy 10ft.) a 45 minute drive away. I modeled 2 4" vents (which I can get for $14) this morning, and it looks the same as 6", except for lower vent mach, which is good, right? So, I'll probably go with 4" vents.

Last decision is tuning. I'm probably going to use this 60/40 movie/music. I modeled three tunings, which are shown. Green is 18hz; blue is 17hz; and red is 16hz. This modeling does not include an HP filter, because I don't know how to do that. My current plan is to get the Bash 300W amp. I guess its HP will reduce the benefit of the lower tunings, right? I have no experience hearing/feeling the differences between different low frequency outputs, so I have no idea which of these will sound better to me. Any advice is welcome, even if there are 10 conflicting opinions.
01-12-12 04:57 PM
Re: Looking for driver and general sub advice

Great. Thanks for the design confirmation. Yes, the angle is for clearance from the side and top.
01-12-12 03:06 PM
Mike P.
Re: Looking for driver and general sub advice

The design looks good. I take it you're angling the port downward for clearance issues.

I thought weighing would be easier than calculating curved cutouts and whatnot.
I see your point.
do you calculate the whole volume of the cylinder of the port inside the cabinet?
Yes, it's considered a solid for displacement purposes.

01-12-12 02:02 PM
Re: Looking for driver and general sub advice

Sure, here are some screenshots.

I thought weighing would be easier than calculating curved cutouts and whatnot. I forget -- do you calculate the whole volume of the cylinder of the port inside the cabinet?
01-12-12 12:12 PM
Mike P.
Re: Looking for driver and general sub advice

About time you showed up!

Sketchup doesn't get along with my laptop so I can't view your file. Could you possibly post a screen shot of the pic? There's no need to weight the bracing for calculating the volume, just figure out how many cubic inches is being displaced from the L x W x H dimensions.

01-12-12 09:31 AM
Re: Looking for driver and general sub advice

Well after two years of my driver sitting on a shelf, I finally made it through enough of my house renovations to indulge myself and build this thing! My plan was refined several times due to the great advice in this thread. Thanks, Mike and everyone! As I am beginning this week (maybe today!), and further advice or encouragement would be greatly appreciated. Here is the current design/info:

Room dimensions: 15'x20'
Music/HT: 50/50
Sub location: rear corner next to end of theater seating
Sub volume: 9 cubic ft. or so, ported
Driver: Dayton RSS390HF-4 15" Reference HF Subwoofer 4 Ohm
Amp: Probably Bash 300

I will go with a 6" port. Exterior dimensions will be 2' tall x 1'-11" wide x 3'-0" deep. Due to HV/AC vent behind, curtains and sofa on sides, table top above, all of those directions are out for driver and vent. Due to height restriction and desire to maximize volume down firing is also out. So, driver and port will be front firing.

The attached sketchup file shows the design. My sketchup skills and time are limited, so it is not complete. The quadrant with the port is basically done, except for lacking cutouts in the longitudinal vertical brace, additional bracing for the port, and two of the cutouts in the horizontal brace don't go all the way through. I also left off the top, back, outer layer of front, one side, the rest of the cross bracing, and port flares. The horizontal brace on the driver side will also curve to wrap around the driver -- not quite to the front. BTW, the driver in the sketchup is some other 15" driver that I found on this site, not the Dayton one.

For ease of construction I will use plywood (3/4"). This will allow me to use simple, strong butt joints. The second phase of this project will be adding false legs and apron and a top to make it into an end table. The front will have black speaker cloth hanging between the legs. Therefore, no part of this box will show, so I plan on simply gluing and screwing it together, only using clamps for alignment and wherever screws are impractical. I offset the two halves of the horizontal brace to facilitate screwing. If there is anyone smirking at this, I will mention that I was a cabinetmaker for 8 years, but don't like doing extra work if there is no practical or aesthetic reason to. I do like things strong and pretty, and I think this design will achieve that when completed. The use of screws should allow me to complete this with fewer pauses to wait for glue to set.

So, any advice? Is the port location okay? I am following lsiberian's advice on mitering the PVC, so that the internal exit is farther from the sides. Does that look good? As I mentioned before, it will have a flare added to the end. I plan on calculating the volume of the internal bracing by weighing one of the pieces before making the internal cutouts, calculating the density of the plywood, weighing it after, and using the density to calculate volume. Then I can do final tuning by recalculating vent length in WinISD, right?

I have line level wires running to the sub (behind the drywall), and my A/V receiver has a low level sub amp output, so I am planning on putting the Bash amp in my A/V cabinet, rather than in the sub. That makes sense, right? I am not sure how to install the amp in the cabinet though. I guess it needs to be in at least a partial box to protect it. Has anyone out there done that?

I know as soon as I post this I will think of something else, but here goes...
12-24-09 02:47 PM
Oklahoma Wolf
Re: Looking for driver and general sub advice

EQ is best left to a last resort thing IMO - if there's any possible way to get the box up to the size it needs to be, I'd do that first. As mentioned, you can run short on amp or excursion fast if you end up having to apply too much boost.
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