Breaking in PE Titanic question (1 Viewer)

[VinhT]

I purchased the Parts Express 10" Titanic driver and 150W amplifier. I put them in a 2 cubic feet enclosure with 2 2 inch internal diameter ports 10.81 inches long as specified by WinISD.

Since I was so excited about building a DIY subwoofer, I neglected to break-in the driver according to the instructions provided by Parts Express. Now that I've finished the sub and am starting to test it out, I'm noticing that it bottoms out like crazy. Now I am fully aware that the ported design has a much higher tendency to bottom-out that a sealed enclosure, but this is ridiculous.

But then again, I'm not exactly sure that it's actually bottoming-out. I've read that when a driver hits its excursion limit, there's a sickening whack. However, the sound I'm experiencing is more like a light pitter-patter of wimpy whacks. The volume on the subwoofer amp is set pretty low, only 1/3.

Anyone have any idea what I might be hearing? Have I somehow damaged the driver, or is this merely a side effect of the breaking-in period that will disappear shortly? Or perhaps the driver is underpowered and the amp is clipping?

(I've already double checked to make sure the driver frame and port tubes aren't just vibrating, also, plugging up the ports tones down the problem a bit, which is why I suspect it's bottoming-out)

Any comments would be greatly appreciated.

 

[Rudy H]

Looks like you're tuning to 26hz...with that big (for the driver) enclosure and high tuning frequency, UniBox says you should be bottoming below 22hz....... my suggestion is to either tune lower, or decrease box size.
You might be hearing the suspension bottoming.... drive it harder and see what kinda sound you get. From my PE 300-794 plate amp (275watts RMS), I get a farting like sound when I drive it into (obviously square wave) clipping on my 15inch Dayton DVC HT sub. I don't get any bottom in my 5.25cf box
Let us know!

 

[VinhT]

Yes, it sounds like the suspension is creaking or something (farts at high volumes). Will this go away after a while? Any possible remedies other than making a new enclosure?

 

[Rudy H]

is the cone moving a lot (about an inch) when the farting comes on?

It could be your amp clipping...but that would be for music, you should be bottoming before clipping for movies.

 

[Ben Ven]

Are all of your speaker fasteners tight?? I had this happen to me a while ago on a sub I built for a car. It was making a fart like noise at higher volumes. After hours of checking, I found 2 screws were a little loose. I don't think you are bottoming out that woofer. You should hear a loud crack when bottoming. What sort of gasket are you using between the woofer and box?

 

[VinhT]

Rudy:
Yes, the cone's moving a whole lot when it starts making the noise. It concerns me a bit, because that's exactly how it looked when I free-air tested it, and I thought being in an enclosure would subdue it better.
Ben:
I'll definitely have to check my screws again. The stuff I'm using between the driver and the baffle is just the foam stuff that Parts Express included with the woofer (4 strips of foam that stick in place). Could you recommend a better material to use? I have a feeling the foam isn't airtight anyways, but I don't want to use caulk on the driver since I plan to recycle it later.
Thank you both for your help.

 

[Ben Ven]

I'll definitely have to check my screws again. The stuff I'm using between the driver and the baffle is just the foam stuff that Parts Express included with the woofer (4 strips of foam that stick in place). Could you recommend a better material to use? I have a feeling the foam isn't airtight anyways, but I don't want to use caulk on the driver since I plan to recycle it later.

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It doesn't sound like the screws being loose. As far as a gasket material is concerned, I have had good luck with a black neoprene based window sealing material sold at Home Depot. It is about 3/8" thick and conmpresses well when the driver is screwed down providing a very good seal. And since it is single sided tape will not stick to your woofer.

Can you do some frequency sweeps to determine if the farting is occuring at a specific frequency? Could you be getting some subsonic frequencies? I know thats a longshot but....

Let us know what you find.

 

[Rudy H]

Vin, I got an excursion graph for you, email me: [email protected] and I'll send it to you.