bookshelf speaker sizes needed [Archive] - Audio & Video Forums


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05-21-2008, 10:40 AM
I'm sure some of you remember me, I made a post about bookshelf speakers earlier; here is the followup post:)

After much thought I've nearly decided what I want to build. I'd like some help determining what size box i need though before I decide. I've also heard that using insulation can decrease the box size. Is that true? Is there a place on the internet i can visit that will give me formulaso t figure out what size things will need to be?

Type the part number into parts-express. apparently the links die quickly.

setup #1:
275-075 x3(one for each speaker, one for the center speaker)
295-362[/url] x2 (one for each speaker)
295-360 x1(for the center speaker)

setup #2:
275-075 x3(one for each speaker, one for the center speaker)
295-360 x3(one for each speaker, one for the center speaker)

275-075 x3(one for each speaker, one for the center speaker)
295-360x5 (two for each speaker, one for the center speaker)

05-21-2008, 07:32 PM
one thing about stuffing a speaker cabinet with polyfill to make the woofer think its in a bigger enclosure. is that you could wind up damping the midrange as well. resultant sound can be a muted effect over the bass and high frequencies sounding louder, sounds unbalanced. i tried an experiment with small book shelf speaks and themid range was way down. but the bass was more pronounced. so i removed it. wasnt worth missing out on the midrange. you should think more along the lines of building a correct sized box. and lining the walls so as to reduce reflections.

what size to choose should be defined in the parts youre buying. altough i could be wrong. since ive never bought anything like this.
one thing you could try is find different sized card board boxes cut out the needed hole for the woofer. and see how it sounds. sure its not very high tech. but it could prove to be cost effective. or different sized buckets with lids . i tried this with a 8 inch wofer before(5 gallonbucket) and it sounded good was suprised by it.
anyways just a thought.;)

05-21-2008, 08:47 PM
that's the poor mans way and i've done it before with cheap car speakers, but I'm looking to do this the correct way.

thanks for the advice about the polyfoam though. What is this about lining the walls?

05-22-2008, 08:25 AM
an example of what i did. it reduces if not eliminate reflections inside the cab.
i bought some bedding foam. it is flat as you can imagine. about one inch thick.
measure out the size you need. e.g. front to back/top to bottom. half inch oversize.
so it doesnt keep falling inside the cab.
in cunjunction with this i put some polyfill in the cab about half full, then proceeded to cram it in the back so it isnt taking up much space in cab but there to reduce reflections. stays there quite well. i did this in my bookshelf yanmahas.

in my sherwood midwoofer cabs i got the same foam since this is a little smaller than the yams i cut out one piece measured the front. top-bottom/side -side. top-top i cut out 2 inches too long so it bows. on side to side i cut it just slightly longer.
this way it fits behind the woofer and since it has pressure against the walls i have no worries about it falling over.

what i used was the yellow foam. if you do go down this route? there are different sizes available. the denser the better. you can tell by feel.
i got really lucky i found some super dence black foam at a llocal thrift store. stiffer than the yellow bedding foam. there wasnt much of it. enough to put some in the sherwoods(enough to cover the back of the cab halfway. and a 3 or 4 inch strip about 2 inches wider than the cab. i was amazed at how well it worked. i even noticed a little bit more bas extension from them.

using this your going to need a little bit of polyfil. to cover spots the foam doesnt get around the woofer.

OR you could buy the acoustic wool that ive read about. try google it if you havent yet. i wont point you to a particular website because i m not promoting any particular product. sure i talk about the stuff i own. just because i like talking audio. speaking coherently i hope.
if you ask me its over priced for what you could do cheaper. all the while you end up with more money for other things. but thats just me

05-22-2008, 09:57 AM
what about the green floral foam? or would that end up falling apart over time?

you say it destroys midrange though? That's bad because that's what I'm looking for in these speakers.

I'm still looking for some formulas to use to develop box sizes

05-22-2008, 07:22 PM
not familiar what the floral foam is. using too much poly fill will reduce the midrange. there is a fine balance you have to adhere to when using polyfill. using too little wont have much effect. using too much will.

lets take an example of what i did with how i used the poly fill.
take a large handfull and put it into a cantainer and put it in there. then push on the fill. when done the foam stays on the bottom instead of puffing up again. i did this but i pushed towards the back of the cabinet. doesnt seem to affect the midrange. while minimizing reflections. i used this combo of polyfil and the bedding foam because of budgetary reasons. had the polyfill around. and when i saw the foam i was wondering to myself (what could i use it for? ok...ill try it in my speakers. works good so i leave it in there.
i dont think it will be cut and paste for the box size. a web page doesnt know the output capabilities of your woofer. check at the parts express site youre buying from. shouldnt they have that info?

05-23-2008, 05:51 AM
sometimes the best things in life aren't free :

05-26-2008, 07:18 PM
i would build a kit if i was you,
small box cannot make good bass unless there is reflex or crossover sensitivity tweeaking in the design
---- you would look in the specs for good sounding bass reviews instead of what reaches lower frequency, in other words you look for quality , some people can say their small enclosures reach 45 hertz but some 70 hertz ones can sound with more bass.

05-27-2008, 09:42 AM
Gab, why are you so concerned about how much bass I get? I guess I should have mentioned i've already built myself a sub for the room.
yes I intend on using a crossover; I didn't feel the need to include that because it shouldn't take up enough space to matter when designing a box.

is that really my only option?