Help for boomy cab?

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charisjapan
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Re: Help for boomy cab?

Post by charisjapan »

GibsonGM wrote:Good suggestions guys, thanks! I'll try a pad. It has a weird resonance when I play 1st C...pretty good otherwise. I still have to stuff it with insulation or something, tho! {lazy}
Hey GGM,

I'm not exactly an expert, but have made a few custom cabs, so here's my 2 yen ...

1) I'm not clear about all the dimensions of your cab, but the slant probably reduced the interior volume of the cab (this is critical in a closed, unported cab). I know you said you made it deeper, but 12" bottom to 6" top is a pretty radical slant, so interior volume is probably down by 20% (just a guess). A while back I explored "optimum" enclosure size for a 12" 100dB speaker, and the ideal cab is the size of a closet! The thing with adding foam or felt "wadding" is to create an artificial volume by soaking up some of those interior waves. It also breaks up some of those specific "pitch assaults" o the backside of the speaker cone. Just throwing a small wool blanket on the floor of the cab might work wonders! (wool and felt seem to be better than cotton ... so I've heard)

2) The slant complicates how the waves move around in the interior. How exactly that works is apparently a very deep science ... at the same time, most folks say it still requires a lot of experimentation. In other words, even the scientists admit that the calculation to real-time achievement of great sound is somewhat hit-and-miss.

3) Porting is REALLY complicated, while open back is a lot more forgiving. But if you need that closed back "projection" and tightness, you have to work at it. As has been said, some speakers just don't work with open back, and some don't work closed. (very generally-speaking, low-efficiency speakers do well open, and more powerful and efficient speakers like closed environments)

I get you about lazy (welcome to the club!), so my suggestion is to just throw any towel inside and see what happens. If it seems to work, you have motivation to try other stuff. And as has been mentioned, irregular bunching (or waves or wadding) will definitely work better than just a flat piece of carpet felt. Don't stuff the cab too much, or it will muffle the tone.

Best of luck!
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charisjapan

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SkynyrdSurvivor
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Re: Help for boomy cab?

Post by SkynyrdSurvivor »

Going back more than a few years I built a handfull of speaker cabinets. The acoustic science of the time, that I could find, said that the purpose of insulation inside of a speaker cabinet was to reduce or eliminate standing waves that would tend to occur between parallel sides of a cabinet. The standing waves would alter the frequency response and creat undesirable peaks and valleys in the response and exagerate resonant frequencies.

This would be the boominess you're having trouble with.

Also that you only had to cover one of each parrallel side with insulation to be effective so the bottom, back and one side would be plenty. Of course overkill with insulation on all sides wouldn't hurt either.

We used the pink fiberglass stuff they used for attics and it seemed to work well.

This was all very much before the innertubes so we had to find everything in libraries. When you started looking, you could find all sorts of stuff in those places.

Is current science much different?

Hope this helps.
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GibsonGM
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Re: Help for boomy cab?

Post by GibsonGM »

Thanks everyone - I have been following the replies on this old thread with interest!
I STILL haven't opened her up to cure the issue, since I haven't used the cab in a band setting in quite a while. Sounds great at lower volumes, so it's not bothering me at home.
I do have a bunch of insualtion "tiles" - they're not batts, but loose squares, almost an acoustic wadding sort of material. I intend to open it up soon and do just what you said, Skynyrd...I want a dead cab anyway, so stuffing seems to make a bunch of sense.

Too bad, it only booms on your first "C"...has a resonance there. I'm actually surprised it's not worse, being so custom sized!
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Vedaire
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Re: Help for boomy cab?

Post by Vedaire »

im no expert on sound or speaker cabs but i use to work in a car stereo shop where we built custom cabs for 12"+ speakers one thing I learned is different wavelengths reflect refract and defract differently when compared to others in a set volume of area if it were me before I went and spent more money I think i would try taking your baffle and move the top closer to the front of the box thereby shortening the travel distance of the soundwaves which might take away some of the boomyiness and brighten the higher tones.

just my 2 cents as I said im no proffesional
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