Driver Noise?

[derekbannatyne]

Whenever I watch some bass-heavy movies, such as the Matrix Reloaded, I can hear the driver (Dayton 15" DVC) moving pretty clearly during high excursions. I don't think it's port noise, it's coming from the actual driver itself. It seems to be coming from the surround, any idea as to what's causing this?

[Bent]

It's almost impossible tyo confirm where a noise is coming from in a driver - the voicecoil's connected to the former.. The former's connected to the spider (and to the cone...) the cone's connected to the surround - any npise gets tranferred thru all of the surrounding area, you get the picture.

My BP-1503 developed a "noise" after a while (very likely my "enthusiasm" that caused rthe initial failure...), the nearest I could figure was my voice coil started to de-laminate and as it heated up, it would rattle and click, I'm honestly not sure if that was it or not, but after a couple of times trying to get a re-cone kit for it (Thanks for nothing, UPS!), I got frustrated and bought a new RL-p driver.

[ThomasW]

Could be one of several things.

Drivers themselves are usually quiet unless driven to the extremes of their excursion where mechanical noises do occur. Normally these are masked by the output of the driver.

There can be small air leaks where the frame attaches to the baffle or in the construction of the box itself. These are usually immediately noticable with a sealed box but don't manifest themselves in a ported box until high output levels.

Finally it could be port chuffing.

Hard to diagnose without actually hearing it...:wink:

[derekbannatyne]

Could be one of several things.

Drivers themselves are usually quiet unless driven to the extremes of their excursion where mechanical noises do occur. Normally these are masked by the output of the driver.

There can be small air leaks where the frame attaches to the baffle or in the construction of the box itself. These are usually immediately noticable with a sealed box but don't manifest themselves in a ported box until high output levels.

Finally it could be port chuffing.

Hard to diagnose without actually hearing it...:wink:

Do you think putting another layer of gasket material around the driver will help? It definitely seems to be coming from the driver, almost sounds as if I can hear the foam moving in and out :?:. But I'll definitely try to record some sound of it later.

It's almost impossible tyo confirm where a noise is coming from in a driver - the voicecoil's connected to the former.. The former's connected to the spider (and to the cone...) the cone's connected to the surround - any npise gets tranferred thru all of the surrounding area, you get the picture.

My BP-1503 developed a "noise" after a while (very likely my "enthusiasm" that caused rthe initial failure...), the nearest I could figure was my voice coil started to de-laminate and as it heated up, it would rattle and click, I'm honestly not sure if that was it or not, but after a couple of times trying to get a re-cone kit for it (Thanks for nothing, UPS!), I got frustrated and bought a new RL-p driver.

I'll try not to be too "enthusiastic"!

[ThomasW]

As I said there can be mechanical noise from parts of the driver if the excursion is high enough.

If you want to experiment pull out the driver and just place it on the floor cone facing out. Using a 9 volt battery or some very low frequency test tones to quickly cycle the cone in and out.

With the driver in the box, test for leaks around the edges of the frame by using a piece of incense or cigarette. With the sub playing watch for the stream of smoke to be displaced off to one side if there's a air leak.

With your sub you might want to make sure a section of the metal isn't loose and vibrating

[cjd]

At low frequencies, the Dayton motor and assembly contribute quite a bit of mechanical noise. I have a pair of the IB sub, which is close enough to the same for this issue. I will be replacing them when I get around to the HT upgrade.

C

[derekbannatyne]

At low frequencies, the Dayton motor and assembly contribute quite a bit of mechanical noise. I have a pair of the IB sub, which is close enough to the same for this issue. I will be replacing them when I get around to the HT upgrade.

C

So it might be typical between these drivers? It only happens at really loud volumes, and you can see the driver moving alot. I'm going to watch Serenity pretty soon, I'll see if it still makes the noise (I just tightened the screws a bit). BTW what does it sound like to you? It kind of sounds like a flapping noise to me, it's hard to describe.

[ThomasW]

I doubt you can hear what Chris is talking about, since he's describing noise off the backside of the driver.

[bobgpsr]

...I'm going to watch Serenity pretty soon, I'll see if it still makes the noise (I just tightened the screws a bit)...

Careful! I was trying out the newly calibrated analog outputs of my Toshiba HD-XA1 with the Serenity HD DVD. At the end of the opening Universal logo my Tumult bottomed when only playing +10 over reference :E. It must have some really nasty bass peaks there.

Bob

[---k---]

I'm not quite sure what type of noise you are describing. And really don't have much to add, but: I've heard a couple noises from my subs now. I originally had a crackling sound which I'm very confident was my amp clipping - doubt you have this problem. Earlier this week, I had a scratching sound when I was playing some sweeps w/ REQW. It was a "shhoooshh shooosh". Pushing on the cone, I heard it very clearly, and could feel the leak from the edge. The weather stripping had worn out and I didn't replace it whe I pulled the driver last week.

[derekbannatyne]

Well I just finished watching Serenity a few hours ago, and the noise was still there. I'm going to try and take out the driver and add a layer of gasket material next week to see if it helps. The only problem is the bottom bolt won't come loose! I tried to take some sound recordings of the noise, but my MP3 player/voice recorder doesn't seem to want to cooperate. But the bass is really nice for music and movies, it's just that sound that is really distracting. I noticed it again when watching Chapter 5 of WOTW.

[cjd]

I doubt you can hear what Chris is talking about, since he's describing noise off the backside of the driver.

I hear it in the room, seating position - the driver backs are not in the room. My guess is something is very slightly off-center and as it hits the excursion limits it pulls the VC to one side slightly. It could easily be something in the wall I suppose, but it's hard to tell. Could still be hearing something off the backs through the cone though.

I should add, it's WAY past normal operating limits when I hear this. So I know well I'm pushing the driver and this is not "normal" when keeping sane levels...

C

[Dennis H]

Bottom line, Bad Things happen when you push any driver past 1/2 Xmax. Published Xmax is like 10% distortion and who knows how much noise. Even the best drivers, like those from TC Sounds, show rapidly increasing distortion once you get past 1/2, if you look at the Dumax plots. So, when you're doing your SPL calcs, double the number of drivers the theoretical math says you will need. As the drag racers say, there's no replacement for displacement.

[derekbannatyne]

Well I got a response from Parts Express, and he told me that it was probably a combination of slight port noise and the spider not being able to control the driver well enough. He said to glue a piece of 8x8" fiberglass to the inside of the port to see if it helps. What will this do?

[ThomasW]

What will this do?

It will put resistance in the port making it function as if it were a smaller port. IOW it raises the tuning frequency. It also tends to mask (damp) any noise generated by the spider that's coming out the port so it's less audible.

This is a 'band-aid' or 'duct tape' type of 'fix' to the symptoms created by the problem, not a solution to the root cause of the problem.

Unfortunately you're in one of those situations where the budget restrictions dictated this driver and you're trying to operate it like it were a higher performance unit.

This is the fundamental reason we alway try to steer people toward the bigger drivers, or more drivers, or drivers with high Xmax. Problem is those are expensive. Hollywood then increases the price of admission by recording lower frequencies and hotter bass tracks...so it's a vicious circle for those on a budget.

If/when the budget permits, sell the driver and drop in one of the 12" TC2+ from www.oaudio.com. These are now only slightly more money than the DVC12, and they're designed to take a pounding...

[derekbannatyne]

Do you know if the 15"s are going to be in stock within a year or so (I'm using the 15" version). Or what about the Dayton 15" RS HF?

[Brian Bunge]

It's possible that one of them could work for you. What size enclosure and tuning frequency did you use for the DVC 15?

[derekbannatyne]

It's about 7.8 cubic feet, tuned to 16-17hz with a 4" precision port.

[Brian Bunge]

Both the HO and HiFi versions will work, but I like the looks of the HO driver in that enclosure. It has a bit of an EBS alignment in the enclosure you currently have, which is what I'm thinking about building if I go ported. I'm thinking I may go with dual HO's sealed though. We'll see. I should have a single one here on Wednesday.

[ThomasW]

Oops my bad for some reason I was thinking you used the 12".... ops:

The new RS15's maybe quieter but they aren't going to give you the needed output for big time bass passages (look at their Xmax).

Unfortunately Todd (oaudio) and TC-Sounds can't come to an agreement about pricing for a 15". That's why none are available.

You can drop virtually any high-excursion 15" in that box and it will work. With the 4" port you might get some port chuffing at high output level using a 15". If you do, seal up the port and use EQ to boost the bottom end.

[Mark Seaton]

At low frequencies, the Dayton motor and assembly contribute quite a bit of mechanical noise. I have a pair of the IB sub, which is close enough to the same for this issue. I will be replacing them when I get around to the HT upgrade.

C

Hi C,

The 2" VC and no venting under the spider in the stamped basked inevitably will make for some noise at high excursion. The noise you should hear is somewhat of a beating, "whump-whump-whump" that comes at excursion past it's Xmax. There's not a lot you can do about that, as every driver has limits as Dennis reminded above.

While I won't claim this will turn your IB driver into a TC woofer, a reduction in air noise from the motor can be had by simply yanking off the screen over the pole vent. Simply pressing with a screwdriver near the edge will break the side free, and then pull it off with a pair of plyers. It certainly won't hurt the performance, and might push the point where you notice this a little higher in level.

[SteveCallas]

Hollywood then increases the price of admission by recording lower frequencies and hotter bass tracks...so it's a vicious circle for those on a budget.

:B :B :B

[cjd]

Well, I may hold off on tearing into those 15's. Looks like I'll be getting a couple 18's to evaluate and give some serious listening. Will have to whip up a different manifold I believe, but that's not difficult.

Mmm, displacement.

C

[derekbannatyne]

Well I finally figured out the problem after living with it for a few months. Since the driver is probably around 5 years old (bought it used), part of the ring under the dust cap had come loose, making that weird noise that I was hearing. Then just a few days ago a chunk of adhesive broke off and started rattling inside the dust cap as well. Well I pulled off the dust cap, took off the old adhesive, put new adhesive in, and now it's working beautifully!

Here's what's under the dustcap:



anyone know exactly what that ring is for, maybe to lower the fs?

[ThomasW]

Glad you found the problem.... :T

From the way you originally described it I wouldn't have thought that was the cause.

Yes typically they mass-load the cone under the dust cap to lower the Fs. Doing that keeps the mass centered.

[derekbannatyne]

Yep it's all better now, I just fired up the Matrix Reloaded and couldn't hear anything coming from the driver, well apart from all the bass!