? Building 12 or 15 Inch Speaker Cabs

Gary Steele · Post by **Gary Steele** » 17 Sep 2000 6:07 am

Gerry Walker the guy that sells the Stereo Steel told me some of the big boys, One is P.Franklin uses his closed back speakers so if this is true he must like the sound of a closed back speaker. I have a killer set of open back speakers i built out of 3/4 inch Birch with 15 inch speakers. They are good looking and sound great but they are a little big. I'm thinking of building a small set of closed back speakers. G.D. Walker has always said with the closed back it will give you the same sound out front all the time which sounds great to me. He talks about these cabinets being tune. So what is the best way to do this? Has anyone ever built two cabinets for steel and left the bottom open kinda like a Bass reflex cabinet rather than cutting holes in the cabinet. Also there is a lot of talk about 12's VERSES 15's and we know some of the pro's use 12's Is there any real reason a person should stay with 15's??? Some guys talk a lot about bottom end but i always thought by experimenting with different amp if you use to much bass it kinda seems to get into the bright side of your sound. So please tell me what you guys have encountered. I'm not building speakers only for my use. Is there any better wood to build than the birch cabs i have now? Thanks for all input. Gary

Ron Whitworth · Post by **Ron Whitworth** » 17 Sep 2000 6:18 am

Hi Gary;
I really like the stereo system using 2 speakers in seperate cabs..Here is another idea that i tried & REALLY liked a lot..Make one of your cabs a 15" spkr & then make the other one a 12" spkr..This setup really covers a lot of ground..Just an idea for you.
Ron

Jack Stoner · Post by **Jack Stoner** » 17 Sep 2000 9:17 am

The size of the porting hole(s) in closed (ported) speaker cabinets vary depending on the size of the cabinet. Go to the JBL site and they have some speaker design documents you can download. Porting will also depend on the low end frequency response you want.
However, according to JBL, the porting holes can be anyplace - not just at the bottom of the speaker mounting board.

J D Sauser · Post by **J D Sauser** » 17 Sep 2000 5:39 pm

Very interesting. I've got a couple of JBL D-130's that I've been thinking of building a new home for.
For some reason though, I can't seem to believe that just simply building a nice "box" will cut it. There's got to be some rules as to dimensions.... (?)

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The future belongs to culture.

jaydee@bellsouth.net

Larry Clark · Post by **Larry Clark** » 18 Sep 2000 12:26 pm

Back in the 70's and early 80's JBL sold an enclosure kit which had plans for building cabinets for their speaker line. They had single 12 and 15 plans for musical instrument cabs as well as some hi-fi boxes.

Jon Smorada · Post by **Jon Smorada** » 19 Sep 2000 4:20 am

J.D., for D130's your enclosure shoule be right around 4 cubic feet and should be tuned. I have a design that I had someone build for me and they sound great. I could probably dig up my drawings and send them to you, or scan them and post them somehow.

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Jon
'66 Emmons P/P D-10 4x8
rebelspirit.net/rebel
rebelspirit.net/showdown

dlayne · Post by **dlayne** » 20 Sep 2000 8:19 pm

Jon,
I got a dumb question,just what is tuned and how does one do it.

Thanks

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Dan Layne

J D Sauser · Post by **J D Sauser** » 21 Sep 2000 6:05 am

Jon, I appreciate the kind offer.

You can fax me @: (561) 791-3416
or email me @: jaydee@bellsouth.net .

Can someone describe "tuning" the cabinet?

Thanks! ... J-D.

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The future belongs to culture.

jaydee@bellsouth.net

Lynn Kasdorf · Post by **Lynn Kasdorf** » 21 Sep 2000 6:53 am

I would like to see some good speaker cab plans for 15" and 12" speakers.

I have a GD Walker stereo steel and I have his speaker dimesnsions as well. As I recall, he uses the same size cab for 12" and 15", which tells me that they are not particularly tuned. More likely, they are just a reasonable size and happen to sound good. A "properly tuned" cabinet for a JBL 15" speaker is pretty huge- I built one from JBL's specs several years ago.

Tuning a speaker cabinet has to do with adjusting the size of the port (on a closed back cabinet) so as to even out the frequency response of the speaker. If you take a speaker and hook it up to an amp and an adjustable audio oscillator, as you sweep the low frequencies you will see the freq where the speaker has the most excursion. This is the free air resonance. Tuning a cabinet mediates this peak, and evens out the response of the speaker. I am not sure of the procedure, though.

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"You call that thing a guitar?"

Jon Smorada · Post by **Jon Smorada** » 21 Sep 2000 7:00 am

J D, Here are links to the plans for D140-F speakers based on JBL's specs. They are full-range cabinets using a 1" compression driver for the horns. I'll have to check to see what value cap I used for the crossover. If you want to use them without the horns, just eliminate the top section of the cabinet and don't drill the hole for the wires.

Main View - http://rebelspirit.net/rebel/d140f/d140fcab_main.jpg

Sections View - http://rebelspirit.net/rebel/d140f/d140fcab_sections.jpg

Sides View - http://rebelspirit.net/rebel/d140f/d140fcab_sides.jpg

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Jon
'66 Emmons P/P D-10 4x8
rebelspirit.net/rebel
rebelspirit.net/showdown

<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Jon Smorada on 21 September 2000 at 08:10 AM.]</p></FONT>

Jim Smith · Post by **Jim Smith** » 21 Sep 2000 7:13 am

Lynn, I don't know where you got your information about 12" speakers. GD's web site: http://www.stereosteel.com doesn't mention anywhere that he offers 12" speakers. In reference to his 15" speaker cabinets he says, "These speaker enclosures are closed back, ported cabinets tuned to allow better bass reproduction while maintaining a small compact size."

I love my Stereo Steel rig, and one of the best features is the compact speaker cabinet size and the room-filling sound I get from them.

I believe that the Marrs cabinets are also made from the same plans as GD's.

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Jim Smith
-=Dekley D-12 10&12=-

bob drawbaugh · Post by **bob drawbaugh** » 22 Sep 2000 1:19 pm

Does any one have any information on the Marrs speaker cabs.

J D Sauser · Post by **J D Sauser** » 22 Sep 2000 1:46 pm

Saved

!
Thanks Jon!

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The future belongs to culture.

jaydee@bellsouth.net