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Booooomy speaker cab

R

Ray man

Nov 5, 2009
708
46
Staten Island NY
#1
Hey,
I have a Hughes & Kettner QC 412 that I never use because it sux.
The problem is at any volume it sounds so boomy.
All the lower notes are so boomy they almost sound indistinguishable from each other. Even the upper register is totaly out of focus and muddy.

This little wedge shaped combo has what looks like a Deltalite or a kappalite except the driver is advertised as having 'duradome' or 'dueldome' technology meaning there is a high frequency source under the dustcap. I don't know if it has any real advantage. What do you guys think?

The other thing that I suspect as the problem is that there is no dampening material inside this cab.
Will adding some clean up the mud and bring focus to the mids? Or will it somehow upset the tunning of the cab?

Thanks guys
 
#2
Almost any 1x12 combo can have the boom removed by putting a Kappalite 3012HO in its place. If the driver has a horn, it's important to make sure there's either no low pass on the woofer or that the driver you're replacing is 8 ohms.

The 3012HO will be boom free down to around 1 cubic foot of volume or less.

Another option would be to get a parametric eq and dial out 150hz 1/2 octave q, or thereabouts.

Adding some dampening material (quilt batting is my suggestion) is the first thing you should do. It should have a negligible effect on tuning, and will absolutely cut back on midrange nastiness.

That said, boom is usually not something you can get rid of with dampening. boominess is usually caused by a big driver stuffed in a small box (relates to the Qts and Vas of the driver vs. the size of the box, and the tuning).
 
#7
Ray man said:
The other thing that I suspect as the problem is that there is no dampening material inside this cab.
Will adding some clean up the mud and bring focus to the mids? Or will it somehow upset the tunning of the cab?

Thanks guys
Click to expand...
There's no excuse for an unlined cab. It can't help but be boomy, with horrid mids. It should be fully lined with an inch to inch and a half of either foam or polyester batting. If it still booms after so doing it's because the cab is too small; not much can be done about that.
 
#8
billfitzmaurice said:
There's no excuse for an unlined cab. It can't help but be boomy, with horrid mids. It should be fully lined with an inch to inch and a half of either foam or polyester batting. If it still booms after so doing it's because the cab is too small; not much can be done about that.
Click to expand...

Are you referring just to that format or a dinky ported cab with a bass driver? Cause guitar cabs have awesome mids, and seem to never be lined or stuffed, would stuffing or lining one kill the good colour?

Is the combo ported?
 
#9
This one?

Invalid Link Removed

Looks like another case of "criminally small cab."

Try some walmart quilt batting to stuff it. That will set you back maybe $7.

While you are in there measure the internal volume.

Replacing the driver is an option, with an Eminence Kappalite 3012HO or similar product that works with the cab's volume.

If the cab is too small and that doesn't fix it maybe put a 10" in there.

That's a lot of messing around unless really like the amp section! If you do really like the amp you might be off to the DIY cab building threads. Do an "ampectomy" and keep the useful parts?

You isolated the problem to the cab. Maybe just take it around to your local store and try it with some other cabs? Or trade it in on something else.
 
#11
Thanks for the responses guy's.

Yes this is the combo, Invalid Link Removed
I bought it a few years back without trying it, it's been in my closet ever since.
Since I never use it, I probably won't bother changing the speaker.
Just as Bill said, 'there's no excuse for an unlined cab', so I think this will be the one thing to try.
If it still sounds murky, then it must be another case of "criminally small cab."
In that case it will go back in the closet.


On a side note, How does dampening material effect the behavior of the speaker or cab tunning?
Does it keep the speaker from over excursion somehow, maybee by limiting the amount of air movement?

I ask because it seems any speaker will play deeper without dampening as it seems to be in my case.
 
#15
At a minimum, put batting in the bottom and sides. That might do the trick, else next the top and start doubling thickness on the bottom... might never need to dampen the back.

I don't know why this is; I am just repeating as best I can what I was told. The original source was the Dave owner or manager at Avatar; I bought one of the very first cabs they ever sold on ebay, and it had minimal batting and was boomy (years and years ago). They sent me some free; not fiberglass but more like a moving blanket, about 1/4 to 1/2 in. thick so I could layer it if needed.

I'm sure there are other ways to approach it and better advice to be found; I only had to do that once.
 
#16
Ray man said:
So does this somehow raise or lower the cab frequency, how does it effect the motion of the driver?
Click to expand...

Tuning is changed by making the port longer or shorter. The batting helps with midrange cancellations so more of the mid and upper sound gets out of the cab and into your ear. It's cheap, some mattress foam and a staple gun, that's it. I'd try that and see how you like it. If not, you can always sell it.
 
#17
My recollection is that changing the cabinet volume will modify tuning frequency too. This is one good reason to use open cell foam, since closed cell foam not only won't do the job, but can take up space in the cab.

I like using a few layers of quilt batting myself :) Cheap and easy.
 
#18
rpsands said:
My recollection is that changing the cabinet volume will modify tuning frequency too. This is one good reason to use open cell foam, since closed cell foam not only won't do the job, but can take up space in the cab.

I like using a few layers of quilt batting myself :) Cheap and easy.
Click to expand...

Changing the volume and leaving the port the same will change the tuning so yeah, open cell foam. I use the eggcrate looking mattress pad stuff on all mine and results sound pretty close to what was expected, at least to my ear. Who knows? Maybe they're all a little off and just sound right compared to each other.:D I don't think I have anything that's totally stock with known curves to compare them to. Every cab I have including PA mains/monitors, whatever has at least been messed with to some degree if not built from scratch.

I really need to invest in a camera and some simple measuring equipment/program and put some of this stuff up here. Could serve as some type of example for beginners and/or scrutinized by pro's so I can hack them up and make some more stuff.
 

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