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View Full Version : Leaks in a Vented Box?



Wagner
11-17-2009, 10:28 AM
As I have posted elsewhere, I am currently enjoying my recently rehabbed L55s.
After getting a little time on Rick Cobbs surrounds they have really opened up and are quite satisfying.

I can hear no sonic anomalies or problems, BUT I can feel (I think) a little breeze in the area where the LE14 is nearest the tweeter. I know my seals are clean and tight as well as in their little groove, and the front baffle is clean and flat. When I go through an old pair of JBLs I wash the seals in hot water and let them relax while I do the rest of the work. They typically will lose the "memory" of being crushed for 40 years, return to their original shape and have always worked well.

As I said, I can't hear a problem, and the breeze may be coming from the cone or the port itself, but it only seems to be happening with one of the boxes on DEEEEEP synthetic bass.

Is this worth pursuing? How much, if any, response am I losing from this tiny, if at all, loss of box tuning?

Thanks,
Thomas

Wagner
11-17-2009, 10:33 AM
Also wondering if the silicone "O" rings are still available individually (correct diameter) at a reasonable cost, or if there is a more desirable solution that won't "glue" the driver to the box.

This for future consideration/projects.

Thanks to all,
Thomas

grumpy
11-17-2009, 10:44 AM
http://en.wikipedia.org/wiki/Scientific_pitch_notation

(toward the bottom of the page).

Even at normal-seeming levels, you -should- be getting a breeze from the
port over at least a few note range (and the cone should almost stop moving).

Even a small leak can whistle at the resonant frequency though... I had an
un-tightened screw blow out of an L19 I was assembling with a test
tone running (just for grins). From that one screw hole, you could feel
the air pulsing out from ~ a foot away.

If there's a leak to fix, it shouldn't be hard to locate.

If the other cabinet is not doing the same thing, and you've traded
speaker wires L<->R (or are using a mono signal), then I'd look further
into the problem.

Mr. Widget
11-17-2009, 10:54 AM
Audible noise or not, I was working with some repurposed cabinets some time back and there was a measurable change in the tuning frequency from simply leaving the four bolt holes open from an unused MA-15 kit. Filling the four small holes made a difference... so, even though a ported box isn't sealed, it should be properly sealed everywhere except the actual port.


Widget

Wagner
11-17-2009, 11:05 AM
http://en.wikipedia.org/wiki/Scientific_pitch_notation

(toward the bottom of the page).

Even at normal-seeming levels, you -should- be getting a breeze from the
port over at least a few note range (and the cone should almost stop moving).

Even a small leak can whistle at the resonant frequency though... I had an
un-tightened screw blow out of an L19 I was assembling with a test
tone running (just for grins). From that one screw hole, you could feel
the air pulsing out from ~ a foot away.

If there's a leak to fix, it shouldn't be hard to locate.

If the other cabinet is not doing the same thing, and you've traded
speaker wires L<->R (or are using a mono signal), then I'd look further
into the problem.


Thank you grumpy. When these guys are cranked you can feel the fairly large ports themselves a foot away. Very prodigious!

I am going to try and pin it down, but it's a little troublesome, it's not very consistent and could just very well be peripheral port turbulence around that area of the front baffle.

As I wrote, there is/was nothing going on sound wise to draw my attention to it. I noticed it by happenstance as I was up close to the box doing something else when I felt it, at what seemed to be an odd spot.

All leaky box issues I've had in the past were much easier; you could hear the problem with little or no effort.

Thank you for the link.
Regards to all,
Thomas

Wagner
11-17-2009, 11:16 AM
Audible noise or not, I was working with some repurposed cabinets some time back and there was a measurable change in the tuning frequency from simply leaving the four bolt holes open from an unused MA-15 kit. Filling the four small holes made a difference... so, even though a ported box isn't sealed, it should be properly sealed everywhere except the actual port.


Widget


Yes :(

I plan to isolate the port's output from the rest of the box's face and see if I still have a "breeze". Hoping not to have to disturb the network and tweeter's seals if that's the offending spot!
Let's hope I'm wrong and there is no leak! :bouncy:
Thomas

Allanvh5150
11-17-2009, 09:05 PM
If you are worried about the rubber rings not sealing properly, if the baffle is good and flat and the mounting flange on the speaker is good you could cut a paer gasket instead. Use something like cartridge paper or some other type of thick paper. One thing for sure though, as the other guys say, the box needs to be airtight appart from the port.

Allan.

kawasakitech
01-12-2015, 11:27 PM
I used felt to make gaskets to seal the drivers
I got the felt at a fabric store and it was cheap too
Made from recycled plastic bottles
I used contact cement to glue it to the front of the cabinet
Seals way better than a little o-ring
I got the idea from old Wharfedale W60s
Removeable back panels can also be sealed
I also sealed the ports in my cabinets as per Philip Newell and they are much improved in sound quality
He recommends sealed cabinets as opposed to ported
Way back JBL recommended a large sealed cabinet for the LE15 not a ported one
I have 2235s in 8 cu ft cabinet with 2425s and 2307s

kawasakitech
01-13-2015, 10:55 PM
Sorry
2370 horns not 2307

Fort Knox
01-17-2015, 06:27 PM
This thread had me revisit my speaker holes...blocking old tweeter holes
and filling in to original port area's ..and I gotta tell ya....
It made for some really clean new sound...
...thanks guys:) FK