So I was given this little jamo sub210 8" ported sub that I want to sell locally to make a few bucks. It functions fine except it has a LOT of port noise. I temporarily stuffed the port just to verify all the noise I was hearing was from the port, and it was. Driver and amp seem totally fine. Port noise is so bad, you basically have to turn it down to the point of barely being audible/useful, so it's not a matter of me playing it too loud (volume was at 12 o'clock/half). I'm also aware of the factors that cause chuffing (too fast air speed due to port size or overdriving). The port is about 2" wide, about 4" long, and has flared ends. I'm not terribly concerned with slightly altering the tuning. I think a buyer would notice the loud chuffing before they'd notice a slight loss of output or tuning change. My options are (A) just plug the port. (B) Completely stuff the sub with polyfill ($5/bag) and leaving port open. (C) Completely stuff with polyfill and plug port. (D) Remove port, make the hole bigger by about and inch or two and install a larger port depending on how much room I have on the baffle. If I increase the port width, how do I determine the larger port's length? Btw, while the port was temporarily stuffed, I was playing bass sweeps and after a while I noticed one spot on the plate amp was very warm. Any chance of damaging the amp in case it relies on the air movement from the port for cooling? With the port open and playing bass sweeps, the air coming out of the port could be felt a couple feet away. Again, this was a normal listening levels (volume was at about 1/2 (half). Thx.
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Thanks. That was (A) 👍
Since it would then be a sealed sub, wouldn't it benefit from stuffing?
No worries of amp heat issues from lack of air movement? Thx.
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If the port has any sharp edges/burs on its inside, removing those can help. In an extreme case may not be enough though.
Some other options that are quick to try and reversible if they don't provide any benefit:
1) Stuff the port with drinking straws
2) Instead of fully sealing the port, lightly stuff it with polyfill or place a thin layer of damping at one of the port ends (could be a few layers of grille cloth or polyfill sandwiched between grille cloth). This may alter port behavior more than the straws, but if done carefully may provide part of the port response. In practice, this may also be similar to your idea of stuffing the box full of damping, if your intention is to fill it to the point where damping is flush to the inner opening of the port.
Some other options that are quick to try and reversible if they don't provide any benefit:
1) Stuff the port with drinking straws
2) Instead of fully sealing the port, lightly stuff it with polyfill or place a thin layer of damping at one of the port ends (could be a few layers of grille cloth or polyfill sandwiched between grille cloth). This may alter port behavior more than the straws, but if done carefully may provide part of the port response. In practice, this may also be similar to your idea of stuffing the box full of damping, if your intention is to fill it to the point where damping is flush to the inner opening of the port.
Thanks! The port is smooth. In fact, if I decided to make it wider, I would wind up using non-flared pvc or cardboard tubing since I'm trying not to spend any serious money, and I'm afraid the lack of flaring, even on a much wider port, would greatly reduce any improvement I might get.
Never heard of the straw trick, but I'll give it a try. I assume I cut them down so they're the same length as the port?
Yes, I thought of putting enough poly fill in the box so that it actually goes over the downfiring port. This port is pumping out air like a hair dryer on high. Lol.
Soundly beaten to the drinking straw idea. Some ports have a flair at both ends. Does this one? The flair can help the air from having to "rip" across the sharp edge. If it's not flaired on the inside, that might be a trick to impliment!
Well then. Looks like "Jamo tried", but couldnt steer it right.
Yes, that could happen.
When I worked for Alesis, I was part of a team tasked to build a new subwoofer. One of my first jobs was to find out what we needed by way of heatsinking. The hope was that a simple flat aluminium plate on the outside rear of the subwoofer would do the job, but I mounted a power resistor and a temperature sensor on the plate, and quickly found out that - in still air - the plate was nowhere near adequate for the amount of power it would have to dissipate.
Someone had the bright idea to make the heatsink plate one wall of the (slot) port. Bingo - air movement in the port dropped the heatsink temperature a lot, all the way from "completely useless" to "this is perfect!"
Obviously I know nothing at all about the specific subwoofer you're working with. But the one I worked on would definitely fry if you blocked the port.
The fact that you noticed the electronics getting hot when you blocked the port, confirms that your subwoofer probably does rely on port air movement to keep its cool.
-Gnobuddy
Thanks! I'll play some test tones with the port unblocked for a while and see if I feel the same hot spot.
Yes. Typically this method is used on non-flared ports and the straws are the same length as the port. In your case, you may get away with them only in the straight section. Seems like someone years ago had a speaker where only a portion of the port had this treatment. Mission maybe?
Below Fb (box tuning) any vent will "unload" and blow air, rather than make bass at "normal listening levels".
The 8" Jamo Sub210 frequency range according to the manual is 38-200 Hz, Fb is probably above 40Hz, you can expect it to blow below 🙂
A strong enough input level can drive the amp to full output or clipping at any volume setting, be careful when using sine wave tones to generate wind.
Also, the chance of burning the driver is probably greater than damaging the amp..
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