I found some Adire Audio 12" Brahmas in excellent condition that somebody was selling on Craigslist for $125 for the pair. I bought them not really knowing too much, but after some research it appears that these are quite legendary. Very capable SPL and SQ, so I am excited at the prospect of being able to build some high-end subs. I am looking to build a ported enclosure with one of them for use in the home. Problem...I have very limited floor space and a wife who understandably does not want any more taken up.
I was looking into building an enclosure beneath my house. I have seen bandpass designs where just the port fires into the room, and I guess I could go that route. But I was really hoping to build a vented system. My question is, if I build a ported enclosure and both the woofer and port fired into a "chamber" that goes to the room, then is this just a bandpass? For instance let's assume the front baffle of the enclosure is 18x14 and fires into a "chamber" that is 18x14x6 such that the 14x6 dimension is a hole in my floor covered with a vent to make it look like a heating vent.
I am thinking all speakers fire into a "front enclosure" that is your room, but at some point that enclosure is so large that it does not affect design. But I don't know how large that area needs to be. It made me think of car audio...is a sealed sub in a car with a window partially rolled down now considered a bandpass enclosure to those outside the car?
Thanks
I was looking into building an enclosure beneath my house. I have seen bandpass designs where just the port fires into the room, and I guess I could go that route. But I was really hoping to build a vented system. My question is, if I build a ported enclosure and both the woofer and port fired into a "chamber" that goes to the room, then is this just a bandpass? For instance let's assume the front baffle of the enclosure is 18x14 and fires into a "chamber" that is 18x14x6 such that the 14x6 dimension is a hole in my floor covered with a vent to make it look like a heating vent.
I am thinking all speakers fire into a "front enclosure" that is your room, but at some point that enclosure is so large that it does not affect design. But I don't know how large that area needs to be. It made me think of car audio...is a sealed sub in a car with a window partially rolled down now considered a bandpass enclosure to those outside the car?
Thanks
When said chamber is large enough to effect the response curve.
Check out the PPSL builds for some ideas where you "port" the driver in a short slot to better load the driver.
A Thread for those interested in PPSL enclosures
14" deep is a 1/4 wavelength resonator at 240 Hz. As the room screws up the frequency response anyway, I would not worry about it. Keep the depth of the front chamber as small as possible. After building the box, the port tuning frequency can come out a little lower than expected, so the port might need to be shortened.
Yes to some extent. A car is lossy so the 'port' resonance is damped.
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OK, 'sounds' like you want a floor vented 6th order band-pass [BP6], so morph it into a tapped horn [TH] to get the most out of it.
GM
GM
GM...not really wanting to get all that complex with it. Honestly just want to build a simple vented, but optimum box I want is about 9 cubic feet and there is no way that will fit in the room normally, thus I am trying to find ways to get the enclosure somewhere else like beneath my house.
The other consideration is that if I build a "permanent" location enclosure then I can't move it to get the best room location for the sound
The other consideration is that if I build a "permanent" location enclosure then I can't move it to get the best room location for the sound
If crossed low (80 -100 Hz) most subs will have little problems sound wise, you could test the best location by using the driver free-air (low power, without blocking vents).
Imho 9 cubic ft is way to big, 2-3 cubic ft (plus materials) sounds way more like it.
Imho 9 cubic ft is way to big, 2-3 cubic ft (plus materials) sounds way more like it.
I put the driver info into WinIsd and it came up with a huge box. I thought that was too big also. I played around with it and 9 cubic ft produced a nice “virtual” speaker response. Originally WINISD had the box over 10 cubic ft.
I have heard of the “subwoofer crawl” method but never taking a driver in free air to test location. Will that really work? Won’t an enclosure change the best location and the way it sounds. Or is that just more a function of the room itself.
I have heard of the “subwoofer crawl” method but never taking a driver in free air to test location. Will that really work? Won’t an enclosure change the best location and the way it sounds. Or is that just more a function of the room itself.
Can you post WinISD input parameters, nothing about the current TSP says large cabinet to me. One thing is for sure, the average room has a large impact on the frequency response.
OK, though while 9 ft^3 is about right for the TH, based on published specs it's ~ 4x too large for a basic vented alignment as Rademakers noted:
Vb = 20*Vas*Qts'^3.3 = ~62.45 L
Fb = 0.42*Fs*Qts'^-0.96 = 25.17 Hz
Note that an 'optimum' in room location is in one of its odd H,W,D harmonics [1, 3, 5, 7, etc.], which for max room gain will be in a corner or at least along the sound wall and/or the wall behind the listening position, which also should be at an odd harmonic:
room modes explained - Google Search
GM
??? Immensely! The only time one uses an [OB] driver in a 'crawl' is when the 'sub' is OB and placed acoustically near the floor or close to the ceiling.
GM