DIY 18" Subs?

fu22ba55 · #1 09-20-2010, 10:43 AM

I love the size of these JBL subs:

http://www.jblpro.com/catalog/genera...x?PId=89&MId=3

23.5" high x 20.3" wide x 22" deep

But I hate that most subs at this price point are MDF, so I'm looking to build my own out of nicer 3/4" ply.

Is there any funny business going on inside these cabs or can I just build boxes out of hardwood ply and drop in the same drivers?

I'm a mac guy, so no WinISD for me.

Thanks.

T-Bird · #2 09-20-2010, 11:03 AM

Hi.

If You don't have any modelling software, I'd stick with proven designs.

I have a pair of "EV" TL505's and they're not much bigger than the JBL's You linked. Heavy as hell, obviously

.

Another (more recent= better?) option would be to go to the Eminence plans section, and build something from there.

Just my 0.02€ as usual.
Sam

SactoBass · #3 09-20-2010, 11:09 AM

I have built my own subs before using the T/S parameters of the driver and design software. They turned out great!

I would say that you could just use the same dimensions as the JBL cab. Just be sure to use the same number of ports, same port diameter, and same port tube length.

And regardless of whether or not the JBL cab has internal bracing, I would install internal bracing in your new cab just to make sure the sides vibrate as little as possible.

rpsands · #4 09-20-2010, 11:09 AM

Leland from SpeakerHardware is making CNC'd cutkits for Eminence 18's and 15's. Contact him. That's how I'd roll if I were going to do this. Shoot him an email and ask him what drivers and size to use.

I would recommend the 4 cubic foot cab with 3015LF's.

SactoBass · #5 09-20-2010, 11:14 AM

Another option for DIY 18" subs is to go to a site such as Parts Express (I have no affiliation), and select an 18" sub driver, and then click on the tab labeled "project ideas" and there will be a pdf that you can click on which will tell you what size to make the cab and what ports to use.

Here is an example:

http://www.parts-express.com/pe/show...number=294-565

billfitzmaurice · #6 09-20-2010, 11:17 AM

Quote:

Originally Posted by fu22ba55

Is there any funny business going on inside these cabs or can I just build boxes out of hardwood ply and drop in the same drivers?

I'm a mac guy, so no WinISD for me.

Thanks.

JBL doesn't sell the drivers for these. It's also a model that's almost universally dismissed as not worthy of the JBL name. One reason why is because it's too small to work well with an 18.

abarson · #7 09-20-2010, 11:20 AM

Try either of these plans from reputable speaker manufacturers. I haven't used them myself, but I'd say that they've already done the heavy work. Also take into consideration that the T/S specs for these drivers may be different than the JBL.

http://www.faneinternational.com/dow...18inch200L.pdf

http://profesional.beyma.com/download/pdf/SB18-3.pdf

I'm not sure about the love affair with 18" speakers. If it's just for looks, what does it matter what's going on inside? If it's for size, I would also tend to agree that the enclosure looks too small for the driver. For the same size cabinet, you're probably better off using a 15" driver.

BassmanPaul · #8 09-20-2010, 11:29 AM

Quote:

Originally Posted by fu22ba55

I'm a mac guy, so no WinISD for me.

Thanks.

You can run the program from the website with Safari. There's also Parallels or Virtual PC. If you have an Intel Mac you can run Windows natively.

Paul

koobie · #9 09-20-2010, 11:47 AM

Quote:

Originally Posted by rpsands

I would recommend the 4 cubic foot cab with 3015LF's.

+1. OP, if you're up for rolling your own, it'd be tough to beat this driver in the right cab.

fu22ba55 · #10 09-20-2010, 12:14 PM

Wow, this is all amazing and helpful info.

I'm dead set on 18"s. I currently have 4 TL606s, and I love those, but I've used 2x15 plus 2x18 in the past, and I'm having a hankering for that setup again. I know I want an 18" radiator, not a long throw... so those JBL, EV, Peavey micro-sized boxes are just what I'm after, but ALL THREE are made of MDF. Yuck.

I have the plans for the TL505s, but thought there might be something a taste smaller.

I had no idea Eminence and Parts Express had plans online as well.

CNC-cut kits sounds like an AWESOME idea... might be just what the doctor ordered.

Talkbass is the best thing ever. I can't imagine how much time and money I would have saved had it existed 20 years ago.

---

Re: a four foot box with 3015LFs

The TL606s are 3.2 feet..

You're saying stick with the 3015LFs and just use a bigger box? Better results than a 18" in a smallish box?

Again.. I'm looking for direct radiation, not long throw. I've been using 15s only for years, and they sound like tweeters to my ears. 10"s are absolutely out of the question. There's something I like about an 18" radiator.

SactoBass · #11 09-20-2010, 12:25 PM

Note to the OP: please take seriously any advice given by billfitzmaurice (see post #6). That guy knows his stuff when it comes to cab design.

fu22ba55 · #12 09-20-2010, 12:43 PM

Quote:

Originally Posted by SactoBass

Note to the OP: please take seriously any advice given by billfitzmaurice (see post #6). That guy knows his stuff when it comes to cab design.

+1

Understood 100%. I totally understand and respect the mighty and awesome power of Mr. Fitzmaurice. No argument here.

So what's the smallest box you'd put an 18" radiator in? And which driver. I like the idea of spending around 400-500 for two 18" drivers. I'm not factoring in plywood cost.

For example

Eminence has a 4.6 cubic foot box for their Definimax 4018LF

Is this box too small? I have no idea how to read the specs below... I'm guessing this is a 24" x 24" ish box?

http://www.parts-express.com/pdf/290-579c.pdf

Box Properties
--Description--
Normalized Amplitude Response (dB-SPL/Hz)
Eminence Designer
Name: Type: Vented
Box Shape: Prism, square
--Box Parameters--
Vb = 4.6 cu.ft
V(total) = 5.346 cu.ft
Fb = 41 Hz
QL = 7
F3 = 41.03 Hz
Fill = minimal
--Vents--
No. of Vents = 4
Vent shape = round
Vent ends = one flush
Dv = 4 in
Lv = 12.56 in

SactoBass · #13 09-20-2010, 01:11 PM

Quote:

Originally Posted by fu22ba55

I have no idea how to read the specs below... I'm guessing this is a 24" x 24" ish box?

Box Properties
--Description--
Normalized Amplitude Response (dB-SPL/Hz)
Eminence Designer
Name: Type: Vented
Box Shape: Prism, square
--Box Parameters--
Vb = 4.6 cu.ft
V(total) = 5.346 cu.ft
Fb = 41 Hz
QL = 7
F3 = 41.03 Hz
Fill = minimal
--Vents--
No. of Vents = 4
Vent shape = round
Vent ends = one flush
Dv = 4 in
Lv = 12.56 in

Vb is net box volume after subtracting out the volume taken up by the driver and the port tubes.

V(total) is the gross box volume before subtracting out the volume of the driver and the port tubes. You can go with any shape cab you want as long as it has, in this case, 5.346 cubic feet of volume (inside measurements).

Fb is the tuning frequency of the box.

Don't worry about QL. 7 is a good number for that.

F3 is the -3dB downpoint of the box. In this case, at 41.03 hertz, there will be 3 decibels less volume than the full volume.

Fill refers to the thickness of the sound absorbing material you attach to the inside walls of the cab.

Number of vents (ports) is self explanatory.

Vent (port) shape is round (tubes).

Vent ends = one flush means one end of the port is flush with the front baffle of the cab.

Dv is the diameter of the vent (port) tube.

Lv is the length of each port tube.

EDIT: by the way, 41hz seems kinda high for a box tuning frequency for a sub. The low E string on a 4-string bass guitar is 41 hz. If I were building a sub, I would want the box tuning freq to be lower, around 30hz or so. Over excursion of the driver can happen if the input signal is below the box tuning frequency. So the lower the Fb, the better (for subs).

mcapote · #14 09-20-2010, 01:12 PM

Quote:

Originally Posted by rpsands

Leland from SpeakerHardware is making CNC'd cutkits for Eminence 18's and 15's. Contact him. That's how I'd roll if I were going to do this. Shoot him an email and ask him what drivers and size to use.

I would recommend the 4 cubic foot cab with 3015LF's.

leland is a little behind on his cutkits, I been waiting a few weeks for him to get the jacks cut

fu22ba55 · #15 09-20-2010, 01:18 PM

Quote:

Originally Posted by SactoBass

Vb is net box volume after subtracting out the volume taken up by the driver and the port tubes.

V(total) is the gross box volume before subtracting out the volume of the driver and the port tubes. You can go with any shape cab you want as long as it has, in this case, 5.346 cubic feet of volume (inside measurements).

Fb is the tuning frequency of the box.

Don't worry about QL. 7 is a good number for that.

F3 is the -3dB downpoint of the box. In this case, at 41.03 hertz, there will be 3 decibels less volume than the full volume.

Fill refers to the thickness of the sound absorbing material you attach to the inside walls of the cab.

Number of vents (ports) is self explanatory.

Vent (port) shape is round (tubes).

Vent ends = one flush means one end of the port is flush with the front baffle of the cab.

Dv is the diameter of the vent (port) tube.

Lv is the length of each port tube.

Awesome. Thank you for taking the time to clarify that for me. I really appreciate it, and apologize if my questions are mundane.

SactoBass · #16 09-20-2010, 01:21 PM

Quote:

Originally Posted by fu22ba55

Awesome. Thank you for taking the time to clarify that for me. I really appreciate it, and apologize if my questions are mundane.

There is no such thing!

And I know only a fraction of what the "real" cab designers know ( like Bill F or Alex who builds Barefaced cabs).

Also, please read my "EDIT" I added to my previous post.

And one last thing.........have fun with this! Building your own subs is cool!!

billfitzmaurice · #17 09-20-2010, 01:26 PM

Quote:

Originally Posted by fu22ba55

So what's the smallest box you'd put an 18" radiator in?

Whatever it takes to get a 35Hz F3. IMO if you're not going that low an eighteen is wasted cartage. A fifteen that has a 40-45Hz F3 will work as well as or better than an eighteen of equal and sometimes greater displacement.

Quote:

Again.. I'm looking for direct radiation, not long throw

There's no such thing as a long throw woofer. Direct radiator refers to a driver that directly radiates sound to the air, as opposed to bandpass and horn loaded, which don't.