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 Post subject: A tweak for cheap speaker cabinets
PostPosted: Dec Mon 28, 2015 10:07 pm 
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They say "You can't make a silk purse out of a sow's ear". True, but you can sometimes make a cheap speaker sound better by just stiffening the cabinet. Cheap cabinets are made from thin plywood or MDF, typically only 1/2 inch thick. When knocked with the knuckles they make a resonant "bonk" sound instead of a better deadened "duck" sound. There's not much you can do about the wood thickness, but you can make it less resonant by stiffening the box internally.
The quick-fix I have used is to cut lengths 1 x 1 inch wood that fit tightly inside the box between the sides and/or front to back, the nearer to the panel centre points the better and the bigger the panel, the greater the improvement... avoid the drivers, of course, not always easy. To fit these braces, measure very carefully so that you can insert countersunk screws from the outside that go into the ends of these internal braces. You'll have visible screw heads on panels outsides, but: 1) these are cheap speakers so it doesn't matter, and 2) use brass screws, they look better. A while back, I was given a really crappy floor-stander made of thin board and cheap drivers (closed box, not reflex)... predictably, it sounded awful. I had a spare PSB high-end 10 inch woofer, a good tweeter and a X/O, which I installed. The speaker unit then sounded sort-of OK, but not good enough. I added the bracing, above, and a bit more internal damping material. The result was impressive, now a pleasure to listen to (mono, of course.)
Cheers,
Roger

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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Jan Sun 03, 2016 5:39 am 
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that's very interesting.

I have fixed up some pairs of 'department store' 3 way speakers by adding true 2nd order xovers and stuffing them with insulation or batting.

I also L-padded the mids and (sometimes) the tweets because they were so overbearingly loud compared to the woof. adding a true crossover helped with attenuation and then adding an Lpad of resistors finished the job.

there was an incredible difference with those mods.

now, they are not a set of wharfedale W70's or Realistic Machs, but the difference between the modified speaker and the stock speaker was definitely noticeable in a pleasant way.

steve

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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Jan Mon 11, 2016 5:21 am 
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Dutch Rabbit wrote:
... I have fixed up some pairs of 'department store' 3 way speakers by adding true 2nd order xovers and stuffing them with insulation or batting... L-padded the mids and (sometimes) the tweets... adding a true crossover...
There was an incredible difference with those mods.
Steve, I am not surprised... done some of that myself! If you also add the bracing I described you'd get even better sound.
Cheers,
Roger

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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Jan Mon 11, 2016 9:27 pm 
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it is so funny that this came up again.

just yesterday, my buddy just called me up b/c he found a set of Technics 12" three way speakers.

i told him to (at least) line the cabinets with good pink panther fiberglass (not that white stuff) insulation and compare it to the other speaker. i also told him about this thread and making the cabinet more solid.

i also added that if he wanted to really break the project loose, he could install a TRUE and REAL 12dB/oct crossover by eliminating those (joke of a crossover) single capacitors.

it sounded like he would try the insulation upgrade first.

steve

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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Jan Mon 11, 2016 9:47 pm 
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I wonder if bubblewrap glued to the inside of the enclosure would do anything worthy?


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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Jan Mon 11, 2016 11:00 pm 
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My guess: no. Not absorbent enough.


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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Jan Tue 12, 2016 9:11 pm 
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Dave Wise wrote:
My guess: no. Not absorbent enough.
Agree. You need many small interstices in the material to give enough SPL loss. Bubble wrap has virtually none.
Cheers,
Roger

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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Feb Mon 01, 2016 10:33 pm 
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Location: Kalispell, Montana
Dutch, the method you describe is generally how I do it, too.

Most of the cheap speakers have either no insulation or very poor insulation.

Also, I have found they often utilise poor quality caps for the crossovers, too. Many I have tested have either been outright bad or out of spec (meaning over 20% deviation from marked value). There have even been some speakers that did not have even a rudimentary crossover at all, the speakers were simply in parallel inside the cabinet.

And some very strange impendence ratings, too. I just saw a pair rated at 2 ohms (on the back label) at a garage sale. I have to confess, that is something I have not seen before in an audio speaker. I bought them anyway, tossed the speakers themselves and did my own thing with 8 ohm and insulation.

engineer, you have an interesting solution there. I will have to try that one. I always like to learn different methods like that. Thank you for posting.

Tony
KC7ZWH


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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Mar Sat 26, 2016 9:05 pm 
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engineer wrote:
Dave Wise wrote:
My guess: no. Not absorbent enough.
Agree. You need many small interstices in the material to give enough SPL loss. Bubble wrap has virtually none.
Cardboard egg cartons work.
Image


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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Mar Sat 26, 2016 9:13 pm 
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Good idea.


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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Mar Mon 28, 2016 6:05 pm 
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Mike Toon wrote:
engineer wrote:
Dave Wise wrote:
My guess: no. Not absorbent enough.
Agree. You need many small interstices in the material to give enough SPL loss. Bubble wrap has virtually none.
Cardboard egg cartons work.
I tried egg cartons once (in a reflex cabinet with a properly tuned port)... speaker was still "boomy". I had to add a fiber fill, I forget which one, then it was OK.
Cheers,
Roger.

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 Post subject: Re: A tweak for cheap speaker cabinets
PostPosted: Mar Mon 28, 2016 8:27 pm 
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In the 70s, a buddy stapled egg cartons in a room. Hundreds of them. Cheap experiment. The room was (almost) dead quiet and was used to test electric guitars, ALUMINUM neck guitars.

R.I.P. Clifford Travis Bean.


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