Head keeps rolling off my cab?

[Downunderwonder]

Originally Posted by wcriley

Hmmm........
Something no one has thought of:
Is it possible that the resonance isn't coming from the cab, but from the floor structure under it?

He's tried it on multiple floors.

[creis2]

Yeah, I tried the cab in all different environments. Studio that was built with good materials, a room in an old house, a cement basement floor.

I spoke to Don. After ideas and some testing, here's the end problem. When I had the cabs built, I insisted on having tall 410's. Basically a design that isn't used, the volume on these is pretty big, but I like the way they sound.

Don told me that the cabs might need more stuffing. As I mentioned this thing has a lot of bracing. Luckily, I was throwing some old pillows out, so I just threw one in the cab and tacked it to the top of the cab temporarily. Although I didn't have a chance to play it loud, I did try it and the head isn't shifting like it was.

Obviously a pillow inside a cab isn't a perm. solution, but it did make a huge difference, so I'm going to double add stuffing to the top.

Not to get into personal details, but Don is a great builder and great business man. We discussed details, and I am currently very happy and recommend him more than ever.

[joelb79]

Stuffing huh?

[vickde]

Originally Posted by joelb79

Stuffing huh?

Perfect. I'll bet if you make that with whole wheat it will really weigh it down...

[joelb79]

Well if weight was the what we were adding, perhaps these work better?

[B-string]

Originally Posted by creis2

Yeah, I tried the cab in all different environments. Studio that was built with good materials, a room in an old house, a cement basement floor.

I spoke to Don. After ideas and some testing, here's the end problem. When I had the cabs built, I insisted on having tall 410's. Basically a design that isn't used, the volume on these is pretty big, but I like the way they sound.

Don told me that the cabs might need more stuffing. As I mentioned this thing has a lot of bracing. Luckily, I was throwing some old pillows out, so I just threw one in the cab and tacked it to the top of the cab temporarily. Although I didn't have a chance to play it loud, I did try it and the head isn't shifting like it was.

Obviously a pillow inside a cab isn't a perm. solution, but it did make a huge difference, so I'm going to double add stuffing to the top.

Not to get into personal details, but Don is a great builder and great business man. We discussed details, and I am currently very happy and recommend him more than ever.

As I thought, beat frequency at the upper part of the chamber. Run this idea by Don; 1/4 round molding added around the inside at the top and bottom with the additional acoustic batting. The pillow was a nice stop-gap idea but not a permanent one

[creis2]

Originally Posted by B-string

As I thought, beat frequency at the upper part of the chamber. Run this idea by Don; 1/4 round molding added around the inside at the top and bottom with the additional acoustic batting. The pillow was a nice stop-gap idea but not a permanent one

The difficult thing is, Don is in Seattle and I'm in Boston.


Luckily, my father is a carpenter, so if any wood work needs to be Done, I'll get Don in touch with him.

The pillow isn't a solution, but Don believes adding stuffing to the top will help.

What do you mean by round molding, like a dowell?

[TRyan5289]

Looks like what we make here at home; chicken and rice wrapped in kale, slow cooked in the crock pot. I'm drooling already.

Originally Posted by joelb79

Well if weight was the what we were adding, perhaps these work better?

[hover]

Originally Posted by creis2

What do you mean by round molding, like a dowell?

No, he means quarter-round molding like this:



Kills reflections / standing waves in the corners.

[Foz]

The difficult thing is, Don is in Seattle and I'm in Boston.

Luckily, my father is a carpenter, so if any wood work needs to be Done, I'll get Don in touch with him.

The pillow isn't a solution, but Don believes adding stuffing to the top will help.

What do you mean by round molding, like a dowell?

1/4 of a dowel - a dowel cut lengthwise twice - a standard trim material



https://www.google.com/search?q=quarter+round+molding

Your father will know.

Got the cab disassembled?

How about some pics of the bracing scheme?

===

As I thought, beat frequency at the upper part of the chamber...

Betcha a doughnut it aint - I understand the dimensions of this cab are sup-optimal in the depth department but I am skeptical that is the big issue here - I think Ockham's razor suggests a simple matter of hyper panel resonance arising from an insufficient bracing scheme and a superbly unfortunate fundamental resonance frequency. Guesses given above - that the core problem is related to interaction between the two largest panels / the baffle and the rear panel - strike me as a good place to start looking.

I would be interested further investigation that might prove us both wrong.

[B-string]

Originally Posted by Foz

1/4 of a dowel - a dowel cut lengthwise twice - a standard trim material



https://www.google.com/search?q=quarter+round+molding

Your father will know.

Got the cab disassembled?

How about some pics of the bracing scheme?

===


Betcha a doughnut it aint - I understand the dimensions of this cab are sup-optimal in the depth department but I am skeptical that is the big issue here - I think Ockham's razor suggests a simple matter of hyper panel resonance arising from an insufficient bracing scheme and a superbly unfortunate fundamental resonance frequency. Guesses given above - that the core problem is related to interaction between the two largest panels / the baffle and the rear panel - strike me as a good place to start looking.

I would be interested further investigation that might prove us both wrong.

Your on. I like plain raised glazed or simple cake. What is your preference?
Either would be affected by added batting but would be more highly affected if acoustic resonance is the cause?
The long distance problem solving is kind of fun but at the same time the itch to get your hands in there is very strong.

[BogeyBass]

the cabinet might have been handled to rough in shipping and alot of mated surfaces or joints have been broken
and might not be visible or obvious from the outside.

then maybe molding and a krapload of glue will save it.
could even drive more finish nails into all the joints from the outside and countersink the nail heads.

otherwise bracing from front to back is gonna kill the rattle bucket front and rear baffle. still advised and would try that first.

take a picture of the inside so we can see how the existing bracing is laid out

[Vince Klortho]

I want to see what an amplifier "rolling" looks like.

[Foz]

Plain cake - hot from the fryer with a side of black coffee.

[creis2]

The problem is, there is existing lining on the inside. To be able to take a picture of the bracing and to add bracing, I'll have to rip it all out.

I'm hoping the extra padding helps, maybe adding a 1" dowell from front to back. If I really have to put that much labor into this, I would prefer to scrap it. I don't have a lot of free time.

[Foz]

Rip it out.

Fixing the resonance once you have a good look at everything and a good plan for repair/augmentation probably won't be a challenge for your Dad.

Replacing the batting is easy - if you decide to augment/upgrade, get a roll of thick poly batting from the fabric store or salvage a few feet of un-faced [no paper] fiberglass insulation batting [R-11 will do] - then snip snip with some scissors and ask to borrow Dad's good stapler for 3 minutes.

[creis2]

Originally Posted by Foz

Rip it out.

Fixing the resonance once you have a good look at everything and a good plan for repair/augmentation probably won't be a challenge for your Dad.

Replacing the batting is easy - if you decide to augment/upgrade, get a roll of thick poly batting from the fabric store or salvage a few feet of un-faced [no paper] fiberglass insulation batting [R-11 will do] - then snip snip with some scissors and ask to borrow Dad's good stapler for 3 minutes.

I can feel the bracing though. It's 1" thick all along the top, bottom, back and side walls. The baffle is very thick as well.

I think I'm going to buy some mattress foam as Don recommended and line the the cab. If it stops shaking, I'll be happy. I'm going to start simple then work to more difficult.

[dukeorock]

Originally Posted by creis2

I can feel the bracing though. It's 1" thick all along the top, bottom, back and side walls. The baffle is very thick as well.

I think I'm going to buy some mattress foam as Don recommended and line the the cab. If it stops shaking, I'll be happy. I'm going to start simple then work to more difficult.

I truly hope that helps, but I can't see how it will, sadly

[creis2]

Originally Posted by dukeorock

I truly hope that helps, but I can't see how it will, sadly

If that's the case, I'll have 4 Beta speakers up for sale and after some slight modifications, my cats will have a pretty sweet kitty condo.

I live in a small Boston apartment, I don't have the space to dissect this thing. My father is in New York, I really don't have the time to screw with this cab. I'm sure my dad and I could have built a sick cab, but I go with custom builds because I just don't have the time.

[f64]

Originally Posted by BogeyBass

its another argument yes, either its seen as to reduce cabinet vibration you need to raise the resonant frequency of the cabinet. and it has been found that adding mass can lower the resonant

+1. I've been following this thread and this was mentioned early on. From a mechanical engineering standpoint the natural frequency of the cabinet is too close to the working frequency of the assembly. When these two intersect all hell breaks loose. A common example is when you shut a pump off and it is slowing down just before it stops it starts shaking violently. This is the intersection of those two points - it's caused bridges to collapse. The common solution is to increase the mass of the object.