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In Reply to: light 8" speakers posted by hollowboy on April 12, 2007 at 22:12:11:
for playing back music. thanks for the reply and the tipned .
Follow Ups:
OK. Sorry, but more questions: by "portable system" and "for playing back music", do you mean for:==> loud use (public preformances, busking, whatever)
==> quiet personal use (like quiet background music on fishing trips)if the former, I'd suggest something new and high-powered. If the latter, I'd go cheap + vintage.
its for this. these are too heavy
they're Eminence beta 8A's. fullrange would be simpler also, and i can enjoy some of that darkness audiophiles speak of :)
sorry if this is posted twice,im having a little difficulty posting
Hi ned,
We need to know what is important to you.Also will the enclosure be sealed, ported or open. You could still get a nice sounding unit even with the back open (search for "open baffle") but less bass.
Is fullrange "darkness" important?
some really efficient fullrange speakers could give a very musically involving performance, but most efficent fullrange speakers have no bass in a small enclosure.OR might want to ensure that the bass could really pump as most (normal) people only judge sound quality by the bass level. It is a boom box after all. you would probably need a tweeter with this sort of driver, but this option generally speaking, would have lower efficiency.
hollowboy's suggestion of the SN-8MB if you can get them, could sound very nice but you'd need a tweeter. some well controlled mid bass and efficient.
It's ALWAYS about compromises.
just some more ideas. I really like this project. Please let us know what you come up with.
Regards Philip
hi, thanks for your interest, i appreciate it. i had a look at those p-audios, i gotta say im excited. never before have i seen something so ideal.whats important to me is
1. weight - i dont have a car so i have to carry it, long distances
2. sound. i understand, or am beginning to understand, more about the
finer points of hi-fi, but for this box bass ands volume are important.3. lesser down on the scale but still relevant is efficiency. id like sustained power. heres the link to the battery i was thinking of, it should power a t class amp for a decent amount of time, and is light http://www.batteryweb.com/eaglepicher-detail.cfm?Model=CF-12V5H
i have sealed the back of the box, using a sheet of perspex with a layer of rubber between to dampen vibration. the perspex is see-through, and i intend to "pimp" the inside of the box in the same way someone would a show car.i really dont know what way to go about venting it or whatever. id love suggestions.
ned,The perspex would need to be thick as it flexes, would look cool though.
sometimes you can reduce bass by putting large speakers in too small a box. There are on-line calculators for box design. Ported one here:
http://www.carstereo.com/help/Articles.cfm?id=17Car speakers may be ok as they are 4 ohms and will draw more power from the amp (as long as they are louder as well!).
I saw these smaller 6.5 inch coaxial drivers in the link below no idea what they sound like though.Rgards Philip
hi, had a look at that link, and followed it up a bit. honestly math scares me, but ill pursue it more. from what i could gather the correct port kindof tunes the box, and eases the load on the woofers. that has to be good.
i had a look at those speakers. their construction is ideal, not for this unit though. i have other shells that use 6.5" woofers, in fact im going to recommend them to somebody who is working on that box.im crap at math but i can draw! appearance is important to me so as a result im not a fan of coaxial speakers, they just dont look right to me. i really do think speakers are beautiful. i realise they would solve the crossover problem im going to encounter though.
what happens if i just seal the thing?
Hi ned,a port matched with the right speaker and box volume can extend bass response. for the SN-8MB the ported box calculator gives a volume of 0.385 cubic feet for 86.98Hz -3dB frequency. Not too bad. A sealed box for this driver gives less bass.
a sealed box uses the air in the box as a spring control the driver at low frequencies. Some drivers will work better in a sealed box.
for a sealed box see the link below.
no math required, click on the link at the bottom of the page for the sealed box calculator. enter the T/S parameters for the chosen speaker to see what the response will be like for a given driver. Qtc above 0.7 gives more boom to your box (usually 0.7 is the highest recommended for "hi-fi" sound)
elswere on the site there is an enclosure volume calculator. you will need to halve the total volume of the shell as you are using 2 speakers. For complex shapes you can also use a strong plastic bag and water to measure the volume, but this procedure can be risky if you have a leak.Regards Philip
seems to me then ported is the way to go. so am i trying to build the correct sized port?also, im going to try the water/bag technique. the eminence that are in there would be approx the same size as the p-audio's, should i remove them before i calculate the volume?
sorry bout all the questions and thanks for all your help.
ned .
Rather than a bag 'o' water, you could use bean bag stuffing. Easier to handle, less chance of ruining things.
Hey thanks Hollowboy, alas i have no beanbag and nightmares over the last one breaking ! i prepped it properly and used three wheely bin bags, no leaks at all thank God.it's 25lt without the speakers or the tweeters
its not an exact science im afraid, but thats as close as i could get it, i was very careful. so what now?
Footstony this is one of the early 90's boxes with the crazy ports
Hi ned+hollowboy,I'm glad you're in litres. Cubic feet sounds like it would be hard to walk.
Quoting my previous email
"for the SN-8MB the ported box calculator gives a volume of 0.385 cubic feet for 86.98Hz -3dB frequency."
you measured "25lt without the speakers or the tweeters"
Using google 0.385 (cubic feet) = 10.9019859 litres
for 2 speakers divide by 2 and remove a few litres for drivers and it's almost spot-on for 2 X SN-8MB!
use the calculator on the caraudio site to calculate the port. I like to tune a port by ear, just stick in different length ports and try! I like to have the ports sticking out of the box for this test so they are easier to change. as a guess a cling wrap tube or toilet roll size could be about right. I have seen people use plumbing fittings to coil a long port inside a box.I love the pic. Those big ports would probably work OK
I think I need to get myself an old boom box shell, install my own electronics and use an ipod to drive it. Do other people do this? are there web sites?
Regards Philip
result! cool cool cool, i can do that. man yeah, theres a few of us working on three boxes at the moment, 1 more in ther pipeline, but not neary enough.
applying the knowlege ye people have, well its just a good idea. theres a major big friendly site, stereo2go.com, home of all things ghettoblaster-ish.look through the collections section, in fact here, this guys ciollection is kicking-
http://stereo2go.com/eve/forums/a/tpc/f/1696027254/m/4391031734
you may need to register to view it. guys got some funky radios.
hi again guys, have been moving along with project, main hassle was cash. im about E200 off the mark now, so itll soon be finished.
i wanted to show ye these speakers i came across, i think they remove my crossover problem (i dont know how to build one~) but i may be wrong cos im a nini. anyways -
http://www.lataudio.eu/HTMLs/BMS/8CN252L.htm
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