Need DIY for decent 18" subs - AVS | Home Theater Discussions And Reviews
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post #1 of 12 Old 06-29-2012, 03:09 PM - Thread Starter
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i am wanting to build two 18" ported subs for outdoor use. i only want to spend ~$100 for each woofer, should be able to handle ~500w rms. i plan to use std -3db choke coil around 100-150hz.

the box needs to be "portable". i will build it from 3/4" ply.

anyone have any DIY's or can suggest woofer along with box/port size?

thnx.
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post #2 of 12 Old 06-29-2012, 04:42 PM
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there is the dayton pa460 from parts express for that money.

two cabinets tuned to 33hz, 6 cubic feet each should be good.

a slot port in each cab that is 3.0" tall by 20.0" wide and 18.0" deep will tune the cab to 33hz.

they will be shooting a little past xmax with 500 watts per driver, but that should be okay.

the next step up is probably the peavey low rider, but they cost twice as much.

the two dayton subs should get you around 127db @1m, which is pretty damn loud.

good luck with your project!

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-036

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post #3 of 12 Old 06-29-2012, 07:21 PM - Thread Starter
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great. thnx for the info.
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post #4 of 12 Old 07-07-2012, 07:28 AM - Thread Starter
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anyone have opinion on suggested build by LTD02 before i go get some parts? i used to build speakers many moons ago as hobby, but havent done anything since then so my speaker books for tuning are either gone or lost....


and on he chokes, -3db is not 2x impedance because power is I^2 * R (in this case R is Z). so the -3db mark is half the power, so on a 8ohm(Z) speaker -3db is something like 12ohm(Z), is this correct?
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post #5 of 12 Old 07-07-2012, 08:42 PM
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most folks in pro audio no longer run passive components to low pass the signal in subs. for low crossover points and minimimal power compression, inductors need to be large and that makes them expensive. it is often much easier and cheaper to actively filter your signal prior to amplification.

what does your rig look like prior to the subs?

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post #6 of 12 Old 07-08-2012, 07:04 PM - Thread Starter
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i will have cheapo Pyle multi-function amp/pre-amp. it has RCA out for sub, but i would need another amp for that. the Pyle unit has 4x speaker outputs, so i just wanted to use that. 14gauge in the 6-10mH rage are not that expensive.

i agree, active x-over is better, i just dont have that setup. my stuff is cheap-o, etc.
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post #7 of 12 Old 07-10-2012, 01:49 AM
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so just to clarify, you plan to run your mains off one set of speaker outputs and the subs off of the other set?

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post #8 of 12 Old 07-10-2012, 11:28 AM - Thread Starter
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apparently the pyle unit has 4 independent channels, so i could run the subs by themselves. but you say "mains". i dont have mains. its basically a 3-way system. i am turning my full range Bose speakers (2 drivers in each cabinet, a 10" woofer and a 1" soft dome tweeter) into the mid/high speakers, and then the 18" driver the low woofer. so i figure i do -3db choke on the 18's around the 100-150Hz mark, then bandpass the woofer on the bose so it doesnt get crushed, etc.

so in essence, i could run it all from one set of amp outputs, but i can indeed run the 18's off of the 2nd set of outputs.
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post #9 of 12 Old 07-10-2012, 03:32 PM
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No way the Pyle is is making 500 watts rms.
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post #10 of 12 Old 07-10-2012, 10:54 PM - Thread Starter
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Quote:
Originally Posted by Manic1! View Post

No way the Pyle is is making 500 watts rms.
its rated 3k watts max.

if its 100rms x4 channels then thats plenty.

its this pyle unit
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=248-4074&FTR=pwma3003t
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post #11 of 12 Old 07-12-2012, 02:25 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

there is the dayton pa460 from parts express for that money.
two cabinets tuned to 33hz, 6 cubic feet each should be good.
a slot port in each cab that is 3.0" tall by 20.0" wide and 18.0" deep will tune the cab to 33hz.
they will be shooting a little past xmax with 500 watts per driver, but that should be okay.
the next step up is probably the peavey low rider, but they cost twice as much.
the two dayton subs should get you around 127db @1m, which is pretty damn loud.
good luck with your project!
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-036

so, does 6cu.ft exclude the port itself and any additional volume used by internal bracing/parts?

using WinISD v0.44 it shows a better response tuning at 40Hz @ 6cu.ft. with a max spl of 98.5 1w/1m, around 125db @ 500w !
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post #12 of 12 Old 07-14-2012, 05:15 PM
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denonkid, the net internal volume excludes driver and bracing. i was giving you a margin for error and assuming a more modern spectral type content for your material. hit an unprotected high tuned cab with a low dubstep note and guess what? recone time because under the tuning frequency in a ported cab the driver excursion unloads and goes crazy.

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