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Finished my subwoofer project
Finished my subwoofer project
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Old 21st January 2006, 01:20 AM   #1
pjpoes is offline pjpoes  United States
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Default Finished my subwoofer project

I can post pictures later when I get some taken. At the moment I thought I would just briefly describe it, and I even had a few questions some might be able to help me with.

1-12" Dayton Refrence SQ sub
1-500 watt Class G Dayton amp
1-2 cubic foot Parts Express(Dayton?) box
3-sheets of 1 3/4" sonic barrier dampening material w/ PSA
1-set of black chrome spikes
1-roll of gasketing tape
8-machine head screws
8-t nuts

I used a router to cut the opening for the amp and the woofer, never used a router to cut circles before, it worked great. I then installed the t-nuts for the spikes and woofer. I then covered all the interior surfaces, including the brace, with the foam material. I have no idea if that stuff was a good idea, but I wanted to try it. I then installed the amp, spikes, and lastly the woofer. After everything was wired up I took it upstairs and isntalled it in my system. Been listening ever since.

I'm impressed with the sound of this subwoofer thus far. I think its still breaking in, the difference in sound just from the first hour of listening now has been immense, that speaker really needed to break in. The amp is practicly dead silent, no hum at all that I can hear. This is the first subwoofer I have used in my system that didn't have atleast a little hum, generally there existed far more than I cared to have in my system.

First thing I played on it was a live recording of an old Louis Armstrong concert, as it was in the cd player at the time. I had the adjustments generally wrong, so I'm not sure what it added to the sound of that cd. What impressed me was the quality of the crossover, it seemed to actually come close to its specified numbers. I had it set at about 60hz, and I didn't notice or hear much from the subwoofer, the cone was not moving much. Which, given the source material, was a good thing. I then adjusted things to see how it would handle a stand up bass, and tried a Ray Brown album I have on SACD. This was also impressive, as the timbre of Ray's bass remained basically the same as withouth the sub, with just a hint of greater girth to the bass, as if the instrument had enlarged. Exactly what I want in a sub, it should not color the sound, warm things up, or pull an instrument like the bass down into the lower registers, farther than it belongs. Most subs I have owned seemed to do that.

I am yet to take any real measurements, but my ears tell me this woofer has extremely low distortion, as the sound from the woofer is far better than my last subwoofer. Everything seems tighter, cleaner, notes seem to have less unnatural overhang, there is no warm fuzziness or moosh around the instruments. It sounds spectacular with good real music.

Because I was curious as to how low the sub could go, I grabbed an old bass test cd I have, which has some really bad techno music with synthesided extreme low bass. Its purpose is to test a car audio system, but I find it works well, as I know most all of the songs have bass that goes down to 20hz or lower, infact, the liner notes tell you how low, and which parts of the song go that low. I was really dissappointed at first with this, but found that really what I was hearing was more natural. I was used to hearing car audio competition systems with a resonant frequency and F3 all at around 50hz, intentionally, so I was used to certain parts sounding much louder than they did. In time I realized what I was hearing was what was recorded on a cd, and that the output levels were as loud as I could expect from one 12" woofer in a room my size. For 99% of what I am doing, this setup is perfect.

Now for my question. I bought some Acousta stuff as well, I used it once before in a speaker project and liked it. I was debating here on putting the stuffing in or the foam, or both. I actually bought 4 sheets of both sizes of the dampening foam with PSA, so I could switch to the thinner stuff and use the stuffing if people feel the foam is taking up too much space. I could also just add some stuffing if people feel thats needed, or could help. I have heard wild debates over the use of the stuffing material, what it does (Lowering the Q of the alignment, I think?), and what to use. I was also told that using it can help correct for small box size problems, say if the box should be 2.1 cubic feet and is only 2, or something like that. My box is 2 cubic feet, to get a .7 alignment I came up with a 2.030 cubic foot box, and with the woofer and amp in it, even with the slightly larger size Parts Express claims the box is, I imagine I am at slightly less than 2 cubic feet. I have it ligned with 1 1/4" of foam on almost every internal serface, even a few small pieces on the amp case. Let me know if you guys think the stuffing might aid, or be needed even.
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Old 21st January 2006, 01:30 PM   #2
Volenti is offline Volenti  Australia
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Regarding the stuffing, from my experience and testing the resonance damping properties of stuffing is a far larger effect then the small thermal effect that only reduces Fs by a few hertz.

ie; a stuffed enclosure (which is now supposedly ~20% acoustically larger from the stuffing) has a completely different response and far higher damping than an enclosure that is 20% larger.

From the sounds of it the damping material you currently have in the enclosure appears to be about right, if the sub starts to sound boomy over time you may want to add some fill to damp the resonance.
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Old 21st January 2006, 02:01 PM   #3
pjpoes is offline pjpoes  United States
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ah yes what you are saying sounds consistent with the articles and 'white papers' I remember reading on the subject too, I had forgoten about those. Thanks, that seems like a sensible way to look at it.

Thus far the bass seems anything but boomy.

I did find one issues, very bothersome too. I can't hear it at my listening chair, but I can't imagine its good. The amplifier, which is mounted in the box, leaks air through the phase switch. Not a ton, but it does leak. My guess is that the area where the wire passes through plastic enclosure around the amp allows air to leak in.

Do you or anyone else know if small amounts of leaking have an adverse affect on the subs ability to be a propper acoustic suspension subwoofer. Everything else is well sealed or gasketed. I even put this red non-hardening paste on all the screws that went into those t-nuts, to ensure they sealed well, but could be easily removed.
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Old 21st January 2006, 11:08 PM   #4
Volenti is offline Volenti  Australia
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For most of the bass frequency range (most music) it shouldn't be a problem but I have had issues before with small leaks like that when playing near infrasonic content at high volume.

You could use a product like

to seal around the phase switch.
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Old 22nd January 2006, 11:30 PM   #5
simon5 is offline simon5  Canada
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I've experienced small leaks when building a big ported subwoofer. They were destroying the sound quality, altering the tuning frequency and lowering the output considerably.

It's less problematic for a sealed enclosure but I suggest you to seal that leak ASAP.

About stuffing, you decide hehe, try it and check if it's good or not for you.
DIYaudio for President !
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Old 23rd January 2006, 04:53 AM   #6
paulspencer is offline paulspencer  Australia
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Leaks can whistle when the pressure is high. The problem is most noticeable at low frequencies and high excursion where the ear is less sensitive and hence there may be less to masking of the whistle while it is more severe. You should try to fix it as it could be annoying.

I made a sub with a cheap plate amp and the sound was like farting! It was so bad I removed the plate amp from the subwoofer enclosure entirely.
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Old 23rd January 2006, 02:28 PM   #7
dfdye is offline dfdye  United States
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Nice to see that you like your new system! I just finished one that is quite similar, and I can second everything you said about the sound quality of the system.

As far as the leak goes, with a sealed box, a small pin hole is often necessary to allow for changes in air pressure between the inside and outside of the box due to atmospheric changes (as recommended by Siegfried Linkwitz--I'm not smart enough to think ahead for stuff like that! ) If the leak is audibly whistling, the by all means seal it and drill another pinhole through the box in a different place, but if it is not audible, I would leave it as a pressure equalization leak.
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