[dvenardos]

Long preamble: 

The genesis of this is from a problem that I posted over here:
http://www.tweakcityaudio.com/forum/showthread.php?t=1433

Basically my neighbors (single family detached home) have complained about my subwoofer shaking their walls like an earthquake. I ran some sweeps with REW a few months ago and thought I had taken care of things and I don't listen at high spls, until "War of the Worlds" last weekend.

I was having trouble with REW and so downloaded some test tones and discovered that in the 22-29 hz range above about 83 db my walls start rattling like no tomorrow. It really is like an earthquake, you can put your hand on the wall and feel it vibrating. The distance from my subwoofer to their wall is about 40ft and our houses are the same model so I am sure it does the same to their walls (I thought they were seriously embellishing). I am guessing that being at the distance of the wavelength they get nailed when I don't have a problem. 0 - 19 hz is dead silent, no rattles at all. They are out of town for a few days, but when they get back I will do some testing with them and see if I can move the subwoofer to eliminate their rattles.
---------------------------------
Question:
Danny has stated that an OB sub does not load the room and I have also heard that the bass is more directional. What about the physics of the soundwave propagation? Does an OB sub not propagate as far as a boxed sub? What about an IB sub? (Can you see this is going to be my excuse here?) I cross my mains over at 40hz and I do have one spot where I could just get 3' for an OB sub (the left corner of the room to the left of the left speaker) and one spot for an IB sub (about 1' to the rear of the seating position where the ceiling and right wall meet). So, at a 40hz crossover I am thinking that one of these two positions might work, but would this solve my neighbor problem or would I have the same issues?

Thanks for getting this far
Don

[cujobob]

If I understand correctly, OB servo subs are perfect for your situation.  The servo amp can be adjusted to do basically anything you would need.  And OB subs don't pressurize like ported subs which is also a huge plus for your situation.  If making your neighbors happy is essential, then get a few dual OB servo subs.  Mine should be arriving this week, so far I've only read about how they sound.

[dvenardos]

If I understand correctly, OB servo subs are perfect for your situation.  The servo amp can be adjusted to do basically anything you would need.  And OB subs don't pressurize like ported subs which is also a huge plus for your situation.  If making your neighbors happy is essential, then get a few dual OB servo subs.  Mine should be arriving this week, so far I've only read about how they sound.

And now I realize that I could actually put it about 5' behind the listening position if I build a nice frame and grills for it. If anyone with an OB sub wants to cross it at 40 hz and see what it sounds like behind you, I would appreciate it.

Hopefully Danny can confirm that this would be a neighbor friendly solution for me...

[Rudolf]

Don,

if you want to solve your problem with OB, there are two things to keep in mind:

- OBs will not produce much bass below the lowest room mode. If you need to have bass down to 19 Hz, the longest dimension of your room needs to be 9 m at least.

- OBs will deliver maximal bass volume when placed in the middle of the room. They do worst in a corner. It is just contrary to conventional loudspeakers.

5' behind the listening position should be fine if you cross over at 40 Hz. Your Xover should have a filter order of 18 dB/oct or higher. IB will not solve your problem because it loads the room the same way a CB or BR does.

Warning: You will need LOTS of cone area to get sufficient OB bass below 30 Hz.

[BradJudy]

If this is a matter of walls resonating at a particular frequency, I don't see how a different sub design will help unless it decreases the SPL at that frequency (which could be done with a PEQ or filter). 

[Bob in St. Louis]

{semi}True Brad, but adding mass to the walls would help contain this.
GreenGlue and one layer of 5/8" sheetrock comes to mind.

Bob

[dvenardos]

Thanks Rudolf.

If this is a matter of walls resonating at a particular frequency, I don't see how a different sub design will help unless it decreases the SPL at that frequency (which could be done with a PEQ or filter).

This is one of the things that I am trying to figure out. Maybe OB bass just sounds better at lower SPL than a boxed subwoofer, this plus the figure eight radiation pattern causes less bass to travel out of the listening area?

[Danny Richie]

Still the OB bass will not load the room and will not put the same kind of pressure and stress on the walls.

[dvenardos]

Danny, do you have any graphs comparing the output of the SW-12 sandbox to a pair of SW-12 OBs like in the Venue?

Still the OB bass will not load the room and will not put the same kind of pressure and stress on the walls.

I think this might be helpful in our understanding, but I will need to sit down with it for awhile.
http://en.wikipedia.org/wiki/Sound_pressure

[Danny Richie]

With the same setting on the amp, the single Venue loudspeaker (with two SW-12-16FR's per speaker) has as much or more output as a single SW-12-04 is a sealed box. Both play flat to 20Hz too.

[dvenardos]

It sounds like this might solve my problem.
What do you think about the position 5' to the rear of the listening position crossed at 40hz?

With the same setting on the amp, the single Venue loudspeaker (with two SW-12-16FR's per speaker) has as much or more output as a single SW-12-04 is a sealed box. Both play flat to 20Hz too.

[konut]

I'm with Brad on this one. Its a matter of your sub exciting the resonant frequency(ies) of your neighbors house as a function of distance(wavelength) and intensity. How those frequencies are produced are irrelevant. Whats needed is a recording of a frequency sweep at the neighbors house to find the offending frequencies, and then notch them out.

[dvenardos]

I want to do this in any case. I have a laptop, mic, and usb sound card. Any recommendations for software that I can use for recording the output of the mic when playing test tones from my house?

I'm with Brad on this one. Its a matter of your sub exciting the resonant frequency(ies) of your neighbors house as a function of distance(wavelength) and intensity. How those frequencies are produced are irrelevant. Whats needed is a recording of a frequency sweep at the neighbors house to find the offending frequencies, and then notch them out.

[BradJudy]

{semi}True Brad, but adding mass to the walls would help contain this.
GreenGlue and one layer of 5/8" sheetrock comes to mind.

Yes, adding mass should both lower any vibrations within the house and hopefully reduce the wave power on the other side of the wall (i.e. what reaches the neighbor's house).  In that way, I'm fortunate the prior owner of our current house added drywall on top of the original lath and plaster - our walls have a lot of mass. 

[konut]

I want to do this in any case. I have a laptop, mic, and usb sound card. Any recommendations for software that I can use for recording the output of the mic when playing test tones from my house?

 

Good question. I don't know, but am sure one of our more computer savvy members will.

[BradJudy]

I want to do this in any case. I have a laptop, mic, and usb sound card. Any recommendations for software that I can use for recording the output of the mic when playing test tones from my house?

Room EQ Wizard is a great free tool - http://www.hometheatershack.com/roomeq/

There's also TrueRTA, but the free version doesn't give you the resolution you'll need - http://www.trueaudio.com/

ETF (now RPlusD) is another option, but it isn't free - http://www.etfacoustic.com/

At one point, I had full versions of all three on a notebook with a MobilePre and a calibrated ECM8000 mic.  I should rebuild my measurement capabilities sometime...

[dvenardos]

REW pissed me off because I had it all setup a couple months ago and when I went to use it the other day, no output from the test tones. I will have to check to see if I can use if for recording only.
Thanks for the other links too, I will check them out.

[dvenardos]

Okay, here is my theory...

Boxed subwoofer radiation pattern. This would be an example of "loading" the room; with uniform pressure on the walls and transference of sound waves to the exterior of the structure.


Now the radiation of the dipole. This doesn't "load" the room; there is not uniform pressure on the walls and sound radiated to the outside is dependent on location (not uniform).


edit: I see the pictures aren't coming through anymore, here is the website:
http://www.kettering.edu/~drussell/Demos/rad2/mdq.html

[Bob in St. Louis]

Forbidden

You don't have permission to access /~drussell/Demos/rad2/monopole.gif on this server.

That's the message I get when trying to view the pics. 

[Stereodude]

SPL= Sound Pressure Level.  If you can hit the same volume with both solutions I can't see how the OB will pressurize the room less since volume is a measure of pressure.