To best keep peace in the house, I need to move my subwoofer into the basement and have it fire back up into the living room from whence it came. Rather than have one large vent, I am looking at making the manifold into a ‘U’ shape and the exits will be through two smaller vents along the wall under the television. The vents would be separated by one floor joist bay that houses an HVAC duct and from what I can see two vents will help cancel nodes due to the sound emanating from two separate locations.
The bottom of the ‘U’ is where the driver will mount. I like to tinker and try different types of subs, so the driver mount will be somewhat universal. The opening will be large (19” x 14”) and there will be 4 large bolt studs so that, with a simple adapter plate, pretty much any speaker/enclosure combination (<= 15” driver) can be bolted to it – sealed, ported, infinite baffle, etc.
My question is this… Since the path lengths of the vents are in the 22”-24” range, would I be running into a 140Hz peaking issue? Or would this be easily taken care of with the crossover? I am not sure how prominent the peak will be.
Any help would be greatly appreciated.
The bottom of the ‘U’ is where the driver will mount. I like to tinker and try different types of subs, so the driver mount will be somewhat universal. The opening will be large (19” x 14”) and there will be 4 large bolt studs so that, with a simple adapter plate, pretty much any speaker/enclosure combination (<= 15” driver) can be bolted to it – sealed, ported, infinite baffle, etc.
My question is this… Since the path lengths of the vents are in the 22”-24” range, would I be running into a 140Hz peaking issue? Or would this be easily taken care of with the crossover? I am not sure how prominent the peak will be.
Any help would be greatly appreciated.
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I am sure you will be able to make it work, but there will be some cases where the behaviour might not be simple.
This will depend a lot on the area and length of air in each duct to the registers in your picture.
Consider one case, with a closed box on the speaker attached to the adapter plate, the ducts to the register, depending on area / length could make the system exhibit bandpass enclosure behaviour.
Clearly an infinite area duct to the register would bring the system back to a first order closed box.
Your trick will be to ensure the area of duct is sufficient that it does not play a meaningful role in affecting the system response. Have you tried to model what a 14 by 4 inch (times 2) duct on tbe front of your speaker does?
This will depend a lot on the area and length of air in each duct to the registers in your picture.
Consider one case, with a closed box on the speaker attached to the adapter plate, the ducts to the register, depending on area / length could make the system exhibit bandpass enclosure behaviour.
Clearly an infinite area duct to the register would bring the system back to a first order closed box.
Your trick will be to ensure the area of duct is sufficient that it does not play a meaningful role in affecting the system response. Have you tried to model what a 14 by 4 inch (times 2) duct on tbe front of your speaker does?
Well, the cross sectional area of the two ducts are more than the Sd of any 12" or smaller driver. So, if the ducts are only 1"-2" long, they do nothing. However, since both of them will be 22"-24" long, they will act as two transmission line enclosures tuned to 140Hz-150Hz. Hence my question.
I think you have the perfect opportunity to explore infinite baffle bass. It doesn't get better than that. Check out: Home | "Cult of the Infinitely Baffled" Hear The Bass, Not The Box The definitive online resource for Infinite Baffle subwoofer design Established 1999
boswald - i do not have any modeling software.
cowanaudio - My first DIY home sub (2001) was an infinite baffle - two long throw 15" drivers mounted in the attic above the living room. I loved it.
Because it's so easy to setup, a 15" IB sub is going to be the first test of this manifold. However, due to the layout of my house, I am curious to see how well the back wave will be separated. Also, I am worried about bothering the guests who use the finished portion of the basement.
But that is the beauty of the universal manifold plate. I can try just about anything I can screw an adapter plate to and that will fire into a 19"x14" hole.
cowanaudio - My first DIY home sub (2001) was an infinite baffle - two long throw 15" drivers mounted in the attic above the living room. I loved it.
Because it's so easy to setup, a 15" IB sub is going to be the first test of this manifold. However, due to the layout of my house, I am curious to see how well the back wave will be separated. Also, I am worried about bothering the guests who use the finished portion of the basement.
But that is the beauty of the universal manifold plate. I can try just about anything I can screw an adapter plate to and that will fire into a 19"x14" hole.
Whether the peak could be "easily taken care of" would be dependent on the crossover type and frequency.
Even with 24 dB per octave slopes, an out of band +6dB response (likely) at around 140 Hz may be a problem unless you also have parametric equalization (PEQ) to address it.
Most DSP (Digital Signal Processor) "crossovers" have more than enough PEQ to deal with cabinet and room frequency response issues.
Perfect! Thank you weltetsys! Yes, my inuke has a dsp with plenty of PEQ power to handle the job.
Now to do something about the rain this weekend.
Now to do something about the rain this weekend.