Building a Sub Box (PIC)

[TX5]

Hey all, my first post. I just found this forum while searching on google. I started making sub box for 2 12" or 10" or watever is the best, since i havent bought nothing yet, i'd like some advice on some subs and amp.. i was thinking loud but cheap, lol. im from aus, and was thinking of spending about 800$ ... ( i dont know much about sound systems ) i know the box can be too small.. but is wat i made too big? here are a few pics..

[img=http://img258.echo.cx/img258/8156/box5nu.th.jpg]

ThX

[Google]

[Sally]

That really is on a sub-by-sub basis. Every model will perform differently in different sized boxes. Are those measurements from the inside of the box or the outside?
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[wb131988]

How do you measure what your sub box is tuned to?

[ToggleHead]

you should go on the website of the speaker manufacturers and check how much air they need to perform the best, including basket displacement......

a lot of companies put the bix measurements on the page too
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[wb131988]

so what do people mean when they say their box is tuned to say 27Hz??

[sandness]

A box being tuned to XX Hz is normally referring to a ported box in car audio. Getting technical, the tuning frequency depends on the vent area, length, and box volume. Getting even more technical, the air mass of the vent functions as a Helmholtz resonator. It resonates at the said frequency and increases output near that frequency.

Here is the simplified equation to derermine a ported box's tuning frequency:

Fb = box's tuning frequency
Av = vent area
Vb = box's net volume (gross volume less speaker, bracing, and port displacement)
Lv = vent length

This is for a standard 4th order vented box. Math gets even more complex for higher order enclosures, as well as quarter-wave and horn loaded designs. Makes for a fun hobby, eh?

[sandness]

Back to the original topic. Based on those external measurements, assuming 3/4" wood, I get a net volume of roughly 5.5 cubic feet. With that volume, I'd look towards 12's rather than 10's. Although I don't know what you brands you have available., I'll go ahead and suggest Kicker Comp VR's. They like larger boxes like that.

Running subs designed for a smaller box in that box will yield a lower Qtc- which can lead to boomy bass, over-emphasized lows, and a muddy transient response- basically can sound like poo.

[TX5]

mmm ok, thx for the reply's .. i'll keep u updated wen i have time to buy some subs, TIME $$$...

[wb131988]

So what is the difference between a ported box and a vented box?

Also do you think a sealed box suits my type R's or would putttin a port/vent in it be better? Thanks for the info and effort guyz

[sandness]

Vented - ported - bass reflex - all are synonomous.

I'd say that if you are happy with the output your current sealed box gives you, don't change. Sure, a ported box will be louder, but is much easier to goof. If it is tuned too high, you get a one note wonder, poor delay times = poor transient response, no low bass, and possible damage from unloading below tuning frequency. Tune too low, you get over-emphasized low the simulates a 'loss' of higher bass. Use too small port area and you get chuffing and noise. Not to mention a ported box will require more volume than a sealed setup.

wb131988 - a word of advice: Please, if you have questions/comments not related to the original post, make a new post - but please don't hijack threads. Not trying to be a dickhead or anything, but it just seems to happen alot.

[wb131988]

well since we are on the subject of sub boxes I just thought it would be OK to keep areas of the topic in this one little neat package lol.... I c wot ur sayin

[TX5]

hey there, im bak.. im still looking around for subs and amps.. and just got some few questions.. i dont know much about amps and im just wondering wats wrong with this amp, http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&category=4950&item=5770611050&rd=1 would it burn after 5 mins of using it? or is is just sh||| ? and would 2 of them run these 2: http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&category=4950&item=5770806159&tc=photo ...

[TX5]

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&category=4950&item=5770805807&rd=1

[fussnfeathers]

Hmm.......well, I've never heard of the amp, and being "exclusive" to an eBay auctioneer........steer clear. You want to stick with a known brand, primarily for longetivity factor, but also for warranty support.

One thing to keep in mind, you CAN overpower your subs, frequency-wise. If you're looking for a more musical tone, where the amp is working at its ideal level, you should look for a setup that's roughly double the wattage of your full range.......so, if you're using, say, a head unit or outboard amps for full range that put out, say, 100 watts per channel x 4, or 400 watts, you really don't want to go much over 1000 watts for your subs. If you get, say, 2000 watts for your subs, with only 400 watts for full range, you're going to be turning down the sub amp to compensate, and amps are designed to run best at "unity", or 0.....however your amp is labeled. Turning the amp down or using excessive padding dampens the signal, and results in muddy, not-too-clear bass. Turning them up to where they sound good overpowers the full-range, giving you too much bass overall.

Audiobahn seems to be a good brand, they've been around for a few years now, with great reviews, so those are OK, but make sure they match up with your amp, and make sure your sub amp falls within the 2 to 2.5 x range of your total full range output. Unless you LIKE overly heavy bass, that is......some people do.
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