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I'm thinking about building a couple of these subs for my basement theater. I have a cubby space that I can put the subs into that will allow me to effectively flush mount them into the wall. I'm trying to go as cheap as possible so my question is - can I use a single port for each sub and have them tuned to 15 hz? I know the design calls for two ports per sub but this is just to have the flexibility to tune them differently right? If I can get away with buying two precision ports instead of 4 I can save $30 or so. Thanks in advance for the help.
If you only ever plan on running it at 15hz, then yes you can build it with JUST a single port.

You are correct in that the other port is there to allow for the different tune options.

If it was me, I'd build it in such a way as to be able to add the other port later on, if needed.
 

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@mtg90
Do you have a design for your VBSS using a single square, triangle, or slot port at the 15hz tune. I am seriously thinking of building 4-8 of theses for my theater room.

Edit: Also with regards to keeping the port velocity low as at least 2-4 of them will be behind an AT screen.

Sent from my iPhone using Tapatalk
 

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Thanks all for the info and replies. EndersShadow, that sounds like a good idea to always have the option of adding the second port. I'm thinking that by having two and running them tuned to 15hz even though it might not have as much headroom compared to if it was tuned higher I'll still have waaaaay more bass than I'm used to. I currently have a little Definitive sub that I picked up cheap off of craigslist. Pretty sure I'll be in for a treat once I get them up and running. Its going to be a while and I'm going to have to do it in stages (gotta pay for a family trip to Disney first). I'll try to post a few pics once its all done. I know everybody around here likes build pics :) I'm sure I'll be back at some asking questions about setting up Behringer amps!
 

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Discussion Starter #585
You can build it with a full width slot port that is 1.5" high x 28" long with a brace running down the middle of the port, This will allow for both the 20hz tune with both halves of the port open or the 15hz tune if one of the halves was closed off.

If just the 15Hz tune is desired then the slot port can be 1" high, full width (22") and 32" long.
 

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Yep, using the original cabinet dimensions.
Any plans on starting a thread on the four Goldwood 10" drivers in that 6th order series tuned bandpass sub? Maybe a rough idea of what it outputs at so many watts? Always had a fascination with bandpasses so your design looks very well done.

Any issues with the bandpass yet? :cool:
 

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@mtg90,

I'm meeting with my wife's uncle who is building me two vbss cabs. Just want to make sure I understand the slot port. If it needs to be 28" long then it would extend roughly 17" back from the face and then about 11" up the back wall of the enclosure. I'm I thinking about that correctly?
 

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Discussion Starter #591 (Edited)
Yes that is correct.

Any plans on starting a thread on the four Goldwood 10" drivers in that 6th order series tuned bandpass sub? Maybe a rough idea of what it outputs at so many watts? Always had a fascination with bandpasses so your design looks very well done.

Any issues with the bandpass yet? :cool:
I can start a thread on that at some point, if enough people want me to. It does have more output then the VBSS but it also has an issue I didn't realize would be as bad as it was.

The font chamber is smaller then it should be for the drivers, this causes a peak in the response near 115hz. I thought no bid deal EQ that flat and all should be well, if anything that peak being EQ'ed down will provide greater headroom and reduction in compression over that range (which it does). The issue is that the GRS drivers tend to have pretty high distortion when pushed up around xmax and where is the excursion peak on this design? Well it's centered around 35hz. So what happens is that as the divers are pushed near xmax in that range the 3rd and 4th harmonics from 30-40hz land right on that peak in the response and they get amplified by it. If a larger front chamber was used (about twice the current volume of that chamber) that would eliminate the peak in the response and also and give more output below 80hz but doing so would make for a sizably larger enclosure overall.

Above the issues in the 30-40hz range range distortion drops like a rock and is impressively low above 50hz which is the acoustic low of the bandpass design working like it should.

Overall the sub in it's current format works ok for what it is, just not quite as good as it could be.

Here is the sim in Hornresp with 400w input, roughly the output of a single channel on an inuke 3000. Could power 4 of these in total off that amp.
 

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Yes that is correct.



I can start a thread on that at some point, if enough people want me to. It does have more output then the VBSS but it also has an issue I didn't realize would be as bad as it was.

The font chamber is smaller then it should be for the drivers, this causes a peak in the response near 115hz.

Above the issues in the 30-40hz range range distortion drops like a rock and is impressively low above 50hz which is the acoustic low of the bandpass design working like it should.

Overall the sub in it's current format works ok for what it is, just not quite as good as it could be.
Ahhhh,

Yes, that 115Hz peak would be problematic if using a conventional 80 to 100 Hz XO--the larger chamber would need a redesign making it larger. Thanks for the reply, series tuned BPs I always found interesting and wondered how wide of a response you can tune the things. Crossing my fingers for a 25Hz and 70Hz tune but that does not seem attainable without response looking like two mountains with a deep valley.

Thanks for the reply and that design is outstanding for 75 bucks in drivers. I ponder how something like four Anarchy 7" drivers or the Dayton UM8 driver would handle that design. Would I be correct in thinking that 6th order series tuned bandpasses require stout cones, strong motors and a lot of thermal mass? I do like the idea of push-pull sub loading and one dimension that is about a foot deep--to slide behind my couch. One of these days... Thanks again for the information and have a great weekend. :cool:
 

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OK, what am I missing ? We are suppose to use the full length of the port but as you can clearly see the port will basically hit the inside of the cabinet.

 

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Discussion Starter #594
There should be about 2" from the port flare to the rear wall of the cabinet, the closeness there effectively gives some extra length to the port allowing a lower tuning then normal.
 

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There should be about 2" from the port flare to the rear wall of the cabinet, the closeness there effectively gives some extra length to the port allowing a lower tuning then normal.
Thanks, so I guess I need to glue that back flare piece on while the port is in place ... and what glue do i use ?
 

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Thanks, so I guess I need to glue that back flare piece on while the port is in place ... and what glue do i use ?
The back flare piece fits through the hole. In fact you could use it as a template to draw the circle for the hole. Wish I'd done that, I ended up making the holes a bit too big.
 

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How would these compare to a Marty microcube? Am I correct that you can run two off of a 1000 dsp?

I'm on the fence about whether these are too big for my living room...
 
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