Sealed Cabinet with 1/4" Input Jacks?

[GregS]

I'm presently building a 4 x 10 sealed bass cabinet. I was going to use two 1/4" open frame input jacks in parallel but it occurred to me that this may be a problem as I'll normally only be using one leaving the other open. It would seem to me that having one jack with no plug in it would create a significant air leak that may cause problems such as whistling noises. If so, I'll just use one jack instead.

Does anyone know if this air leak associated with 2 jacks would be a significant enough problem to be concerned about?

Thanks,
Greg

[g1]

I've seen cabs that have little plastic plugs that go in the jack you are not using, so some manufacturers are concerned with the issue.

[olddawg]

I think the cover plug is for corrosion more than anything else. 1/4" is an awfully small port. I doubt you will perceive a difference. But people hear all sorts of things, lol.

[Leo_Gnardo]

Jiminy Cricket says "give a little whistle." And yes I've run across this. You could build an aritight mini box around your jacks. Doesn't have to be incredibly sturdy. Even a plastic container of most any sort would do. I've also used "barrel jacks" but they don't seem to last as long as the good old Switchcraft # 11. Cost a lot more too.

If you have very powerful speakers, and that jack's a bit loose, could blow the plug right out. Seen that happen too.

"Give a little whistle, and you'll know what to do."

[Bill Moore]

I have built several sets of cabinets, and always use 2 1/4" input jacks. (I have had 1 fall into the cab when we arrived at the venue!) I have never heard the whistle Leo describes, but my high frequency hearing has been weak for a long time.

[The Dude]

If you're guitar volume isn't loud enough to cover any slight whistle, do you really need a 4x12 anyway?

[J M Fahey]

From a practical point of view, no whistle nor parameter degradation with such a small hole.

Plug blowing is a real possibilirty, doubly so with Cliff type plastic jacks.

FWIW I had custom made "Double positive" jacks, meaning classic stereo metallic jacks, but with two "tip" contacts instead of tip and ring; and to reinforce the concept, flexible contacts made out of double thickness (4 X the rigidity) phosphor bronze.

Have to order them in lots of 1000, but well worth the effort and cost.

Will post a couple pictures.


Plugs "click" in with authority and surprise my customers when pulled out.

[Enzo]

This is a bass cab, and so might be expected to move more air than a guitar cab. I have seen plugs blown out of jacks. Those locking Neutrik jacks with the push tabs hold on well and are not a clear through hole. I have heard jacks whistle on bass cabs, not often, but it happens. The tiny hole won;t upset the performance of the speakers though.

Peavey uses two-tip jacks in some speakers and other applications, so you need not order 1000 of them, you can order one or two from them.

Classic 30 is one example, the extension speaker jack. In fact on that one they rely upon the tip shorting the two contacts together to complete a circuit. The input jack is one also.

Their part number is 71466214. TS jack with cutout and extra tip contact. It is one of those square black Switchcrafts with the one beveled corner. They do hold the plug more tenaciously.


There are some 4x12 cabs that have XLR connectors on them in addition to the 1/4". THose won't blow out from wind pressure.

[jbltwin1]

When they ship Hot Spot monitors with two jacks, ONE of them has a screw on cap that screws directly onto one of the jacks that protrudes a tad further than the other.

[olddawg]

If you are really worried check out these:
Switchcraft : 1/4" Locking Panel Mount Jack
Switchcraft : 1/4" Jack Cover

Or check out the whole line:

http://www.switchcraft.com/category.aspx?Parent=42

[Leo_Gnardo]

If you are really worried check out these:

Switchcraft : 1/4" Jack Cover. Thanks for reminding me of "mini hatch covers", got 'em on my JBL cabaret wedges. Keeps ants & wasps out.

[R.G.]

Doing it right (IM...limited... O) means making a small pressure-holding box around the jacks inside. If I were doing this, I'd probably make a metal cover for the outside of the box to mount the jacks on. Then I'd cut an opening for letting the jacks project back from the mounting plate. Then I'd glue a block of wood over the jacks-mounting hole on the inside. When the glue is dry, use a 3/4" spade bit to drill recesses in the wood block for the jacks to not interfere, and run wires into the interior through a small hole that you then caulk airtight.

I've seen bass cabs with spare jack-holes blowing puffs of air that you could feel easily on your finger.

[The Dude]

Legend is that the original Marshall 4x12 cabinet was designed for the least amount of wood waste. There is no "magic" in the box design as evidenced by the number of completely different speakers that people put in them. (Note: I'm not saying that they don't sound good.) That said, if the concern is that a small air leak is going to have an effect on performance, I wouldn't worry about it.

[GregS]

Thanks for all the responses! Lots of good interesting info in here!

What prompted my question was stuff I'd read in cabinet construction articles where small unintended air leaks in the cabinet could create un-wanted whistling sounds. That lead me to wonder about the opening of an extra un-used 1/4" speaker jack. Perhaps that's too large an opening to create a whistle - smaller cracks might be more of an issue?

I'm not too worried about plugs blowing out of jacks. I've never had that happen - either with my amps or the P/A which also uses 1/4" jacks. Perhaps that's more of an issue with very high power applications. My amp is only 160W and I don't use nearly all of that.

I'll probably just end up using one jack on the cabinet as I think the chances I'll ever use a second are slim. I have 2 parallel speaker jacks on the amp in case I ever want to run 2 cabinets which should be fine as both cabinets will likely be in close proximity to the amp so no need to daisy chain cabinets. I don't want to go to a lot of time and trouble on this now as I'm anxious to get the cabinet completed and in use. However, if I end up building P/A cabinets and monitors where daisy chaining is common and multiple jacks are needed, the information in this thread will be very useful.

Thanks to all who contributed. Much appreciated.

Greg

[GregS]

If you are really worried check out these:
Switchcraft : 1/4" Locking Panel Mount Jack
Switchcraft : 1/4" Jack Cover

Or check out the whole line:

Switchcraft : 1/4" Jacks and Plugs

I looked at this after my last post. This seems like a great simple solution and may change my mind on this. I never knew these existed. Thanks for posting this.

Greg