Tips for fixing a loose port - AVS Forum
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post #1 of 12 Old 09-29-2012, 11:35 AM - Thread Starter
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We have a dayton 15" HF in a 6.5^3 ft (internal) box with 2x, 30" ports. The ports have a 90 degree bend in them. I noticed a distorted sound and thought maybe we over did the driver or maybe over driving the plate amp. It sounded more like a vibrating noise upon closer inspection. It happens during movies where the sound appears to go into the lower frequencies, like maybe 25hz and lower. So I thought maybe it's one of the ports. I stuck my arm in the port to the elbow and put a little pressure down on it. When I play a scene with some low bass, it makes the distorted noise stop.

Any one ever run into this? If you did, what did you do to fix the problem aside from taking the thing apart? The best thing I can come up with is taking the plate amp off the back of it and see if I can better secure the port with a clamp or something. Only problem is, I don't know how well the amp will screw back on into the same screw holes. Thanks in advance for the tips smile.gif
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post #2 of 12 Old 09-30-2012, 05:14 PM
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When you do an experiment, you have to isolate and change one variable at a time. Sticking your arm in the port effects two variables - port inertness/looseness and port tuning. The distortion may in fact come from the driver due to excursion, but since you stuck your arm in the port an d lowered the tuning frequency, that will change the driver's excursion. Or it may even be air flow induced noise that will also be tuning frequency dependent and thus change too.

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post #3 of 12 Old 09-30-2012, 06:27 PM
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Are your ports at all braced? As on are the attached to anything in the box. Most people will cut a hole in the brace to accommodate the port. Because unfortunately the port itself can resonate.

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post #4 of 12 Old 09-30-2012, 09:05 PM - Thread Starter
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I looked at the driver during the "problem sound", and there is not any excessive excursion going on. That's what made me stick my arm in the port and hold it down. I first thought maybe the driver was hitting against itself when we didn't notice and caused damage. I put my ear to the driver while playing a scene that caused the rattling sound, and then to the port. It's much more noticeable with my ear to the port. Plus being able to put pressure on the port, which eliminates the sound make me suspect the port has come loose inside the box.

The best solution I can come up with is taking the amp and driver out, and getting rid of the ports. We can than take a saturday and add a slot port in place of the original ports. I just have to run it through winisd and see what's possible to save the box. I really don't think it's the driver, and I'd imagine PE wouldn't give us much of a hard time on the warranty because we're only using a bash 300 with it, and we never crank it.

Edit: Yes the ports were secure, we put a piece of rounded wood on each port side, then liquid nailed the ports into the groove.
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post #5 of 12 Old 10-01-2012, 04:36 PM
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Options include more port bracing, gluing, and/or mass added to the port to change the frequency that it vibrates at, if indeed it does vibrate.

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post #6 of 12 Old 10-01-2012, 09:19 PM - Thread Starter
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I am pretty sure it's the port making the noise. We decided we're going to scrap the enclosure and make a folded horn (tuba ht, or f-20). So is there any way I can be 100% sure there isn't a problem with the driver before we recycle it in the folded horn?
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post #7 of 12 Old 10-07-2012, 01:26 PM - Thread Starter
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I took it apart and the port was definitely loose. But I'm a little concerned about the glue on the spider. I don't remember what it looked like when we first got it so I'm not sure if this is normal. If it is wrong, I wonder if dayton will waranty it. We're only using a bash 300, and we don't overdrive it at all. Here's some pics:

DSC01239.jpg

DSC01238.jpg
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post #8 of 12 Old 10-07-2012, 06:32 PM - Thread Starter
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I just took it out of the enclosure and played the same scene. I had it on top of the enclosure and the port vibrated and made the same noise, so I put the driver on the floor and it didn't make any noise. So it's definitely not coming from the driver. I am still concerned about the glue though, I'm not sure if that's normal or not. Hopefully it doesn't have to get sent back because I just cut the wood for the f-20 today.
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post #9 of 12 Old 10-07-2012, 09:39 PM
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Quote:
Originally Posted by doodoobutter View Post

I just took it out of the enclosure and played the same scene. I had it on top of the enclosure and the port vibrated and made the same noise, so I put the driver on the floor and it didn't make any noise. So it's definitely not coming from the driver. I am still concerned about the glue though, I'm not sure if that's normal or not. Hopefully it doesn't have to get sent back because I just cut the wood for the f-20 today.

To fix the port, bond it with high strength vibration resistant epoxy or contact plastic cement to the enclosure.

Looks like the the spider is coming detached at one point of around it, as I can see a gap with no glue on it. Definatly looks like a manufacturing defect, as the spider is supposed to be glued down all the way round.
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post #10 of 12 Old 10-08-2012, 06:08 AM - Thread Starter
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As for fixing the port, we already started on making a folded horn. For the spider, is there anything I can do myself to fix this? Or do I have to send them into parts express? I never saw this happen, not even on cheap car subwoofers. I cracked the cones on 2 sony xplods with an ep4000 and the spider was still intact...

edit: It doesn't seem to be affecting the sound, so as long as it doesn't look like it'll get worse I could just leave it.
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post #11 of 12 Old 10-08-2012, 06:25 AM
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Looks to me like a manufacturer defect. If it tore I would think you would see obvious ragged edges in the glue. Find out what type of glue Dayton uses and just add a little there yourself for added insurance.

Dumb enough to spend lots of cash on this junk!
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post #12 of 12 Old 10-08-2012, 08:08 AM - Thread Starter
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I was thinking about trying to re glue it. But the spider is so rigid that you cant stretch it back at all. I'll see what parts express says, maybe they will cover it under the warranty. It's only about 5 or 6 months old.
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