DIY Subwoofer first build 2 18's - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 8 Old 07-08-17, 03:31 PM Thread Starter
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Join Date: Jul 2017
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DIY Subwoofer first build 2 18's

Hi,

I have these 2 drivers sitting around my house after a trade i made with someone. Both subs work perfect and i traded my 2 pioneer ts-W5102's for them along with a few other things.

This is what i have to use

Behringer EP4000.
2 RE XXX 18's dual 4 ohm

I bought 3 3/4" plywood already and i have some half inch aswell pieces i can cut for bracing or front mounting help.

I've asked around a bit and i have alot of different recommendations. Some way too costly to even try to build.

Skill level = average

I would prefer doing a sealed application if i can get it good for HT. I dont mind size because i have a giant living room. Approx 20ft by 35ft or bigger.

I know i can run 1200w RMS peak from that amp and i'm not looking to push these to full power and i'm not sure of an amp that can push them harder at 2 ohm.
My second option would be to bridge the amp and subs together for 2400w rms at 4 ohm with both subs wired for 4 ohm.

I am ok to build a sealed box any size (possibly), either 2 boxes or 1 for the 2 drivers.

I dont have access to ports anywhere where i live, but can do the "L" port method aka slot port?

I tried using bassbox pro and a friend used another program but something doesnt seem right with the box size. Alot of forums said 10cuft will give you a good low response, and recommended is quite small, but if going super small you need alot more power to drive the driver.

So any help would be appreciated alot. I'm not good at figuring out the box size because in my head i know a cubic foot is 1 foot on all sides correct? so if they ask for a 4 cu ft box, sure seems small for this type of sub no?

Thanks again for any help i really would appreciate it.

If all goes good i'll post my build here and how it turns out

Current setup
Front's 2 Paradigm Monitor P90 V3
Center Paradigm CC 390 V5
sides Paradigm Monitor 9's
Backs Paradigm Montor 7's
Main Sub Paradigm Ultracube 10

Yamaha RX A1010 Home Amplifier
Behringer Ep4000 for the subwoofer build



Driver Properties
--Description--
Name: XXX 18 D4
Type:
Standard one-way driver
Company: RE Audio (2015)
--Configuration--
No. of Drivers = 2
Mounting =
Standard
Wiring =
Parallel
Drivers sum coherently =
Yes
Dual voice coils =
parallel
--Driver Parameters--
Fs =
28.94 Hz
Qms =
5.403
Vas =
3.404 cu.ft
[6.808]
Xmax =
2.3 in
Sd =
194.8 sq.in
[389.6]
Qes =
0.802
Re =
1.881 ohms
[0.94]
Le =
2.077 mH
[1.039]
Z =
2.257 ohms
[1.128]
Pe =
2000 watts
[4000]

Last edited by Nicodareus; 07-08-17 at 04:04 PM. Reason: adding current setup
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post #2 of 8 Old 07-10-17, 07:05 PM
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My System
Re: DIY Subwoofer first build 2 18's

A few things to keep in mind: a 4ft^3 box would be about 19.5" on each side, and a 10ft^3 box would be about 25" on a side. Volume of a cube obviously increases exponentially... oddly enough, with the cube of the length of a side. (Odd how these things work out sometimes...)

A 4ft^3 box is definitely not small, and there are plenty of 18's that would be right at home in a sealed design of that size. I'd suggest, especially if this is your first run at building a subwoofer, that you make a sealed box. It's much simpler to design and construct a decent sounding sealed sub than it is to design and build any version of a vented design, and for a lot of reasons. I'd also go with two separate boxes, if for no other reason than it will be much easier to move when you're finished. If you want to run them together in series or in parallel, you can still make the appropriate connections at the terminals on the box, and you have the option of changing your mind for whatever reason. I'd also wire the dual coils on each driver in series, giving you a single 8Ohm driver... then you can run in parallel for 4 ohms if you want. Or power them independently at 8 each. And if you decide to power them in series, you have 16Ohms (not necessarily ideal, but at least you don't risk killing your amp with a 2Ohm load).

If Bassbox is suggesting 4ft^3, you can safely bend that number by 25-30% in either direction, remembering that altering the box volume nominally alters the F3 of the box proportional to the change in volume. It has other effects, like the final Q of the system, but since this is your first shot at this, I wouldn't worry too much about that. Your point about smaller boxes requiring more power is pretty much correct... because of the smaller air column inside the box, the driver experiences the sensation of "riding on a stiffer spring". As the driver moves, it either compresses or rarifies the air in the box... less air in a smaller box will compress or rarify faster, and thus exert a larger force on the cone of the driver. It takes more amplifier power to overcome this, but it's a rapidly diminishing return and because the box may be restricting the motion of the cone, you can run the risk of overheating the coil. I wouldn't call "likely", but it's mathematically possible.
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post #3 of 8 Old 07-10-17, 08:06 PM Thread Starter
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Thanks for the reply. I started the box and going sealed. I followed their recommended box size then adding 2x3 bracing inside but added to the volume so instead of say 18" high its now 18.9" high.

For the amplifier part im going to wire them so i have a final impede ce of 4 ohm. My power amp is 4 ohm stable at 2400w rms.

That sounds correct no?

Thanks again for your reply. I have no garage so just working on a peice of plywood set on my lawn. Well garage i have but my dad stores his corvette there since his place has no space.
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post #4 of 8 Old 07-11-17, 06:40 PM
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Re: DIY Subwoofer first build 2 18's

So, is that a single 18, or a dual 18 box? And if it's dual, did you make it ~2x the volume to account for the second driver?

There are two ways to get to 4-ohms using 2 4+4 subs... you can wire each sub parallel for 2Ohms, then wire the two subs in series for 2+2=4, OR you can wire each sub series 4+4 for 8Ohms, then wire the two subs in parallel for 4Ohms. In theory, it doesn't really matter which way you go, but it does matter that you use the same method on each sub. And it's better if you use the same method the manufacturer used when testing the specs. Given your specs, that means you should wire each individual sub for 2Ohms, and then put them in series with each other.

If the system total is 4Ohms, then you and your amp should be good.
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post #5 of 8 Old 07-11-17, 09:16 PM
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Re: DIY Subwoofer first build 2 18's

that ep4000 is rated to 2 ohms per channel. 1250 rms and 2000 peak each channel. the only way they don't recommend 2 ohms is bridged mono. parts express has the manual linked on the website.
https://www.parts-express.com/pedocs...nual-43359.pdf

did you use this from the re website for the box size?
http://reaudio.com/products/woofers_xxx.php

dave

basement
AVR - Yamaha RX-V867 AMP 1 - Acurus 200X3 ( for the fronts ) AMP 2 - Behringer EP4000 ( for the subs ) AC FILT - Harbor Freight power strip DISPLAY - Hitachi 15 year old 57" 1080i
MAIN - Bang & Olufsen Redline 140 CENTER - Bang & Olufsen Redline 140 SURROUND - Monoprice 6 1/2" in ceiling SURROUND BACK - Monoprice 6 1/2" in ceiling SUB - Dual PSB 10" passive
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post #6 of 8 Old 07-14-17, 07:31 AM Thread Starter
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Quote:
david yurik wrote: View Post
that ep4000 is rated to 2 ohms per channel. 1250 rms and 2000 peak each channel. the only way they don't recommend 2 ohms is bridged mono. parts express has the manual linked on the website.
https://www.parts-express.com/pedocs...nual-43359.pdf





did you use this from the re website for the box size?
http://reaudio.com/products/woofers_xxx.php

dave
Yep used the sealed but added some space due to bracing material inside the box.

This is my first ever build. Had to silicone a bit to seal the subs and some air got out of a few screw tops so siliconed that too.

Build pics and video coming
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DIY Subwoofer first build 2 18's-img_1302_1500035361537.jpg  

DIY Subwoofer first build 2 18's-img_1313_1500035427004.jpg  

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post #7 of 8 Old 07-14-17, 07:33 AM Thread Starter
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Trying to put a video but it wont let me but wow the excursion and sound is tight. Had to get a buddys help getting that box off the ground though.

Had to work in the yard to make this project.
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post #8 of 8 Old 07-14-17, 07:35 AM Thread Starter
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Goes well with placement although may move to the corner. Tv stand is angled as i was organizing some wires.
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