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  15" speaker cabinet design

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Author Topic:   15" speaker cabinet design
Pete Knapton
Member

From: Christchurch, New Zealand

posted 21 November 2004 02:36 PM     profile     
I have a couple of vintage 15" speakers and want to make a single 15" cabinet and road test each speaker, for steel guitar and rhythm guitar. And then use the cabinet for gigs, with the chosen speaker.

My understanding is that a cabinet should be designed to suit given speaker specs. The two speakers in question are JBL K130 and a 1970's Celestion G15C, both are instrument speakers.

I feel that a closed box with ports is the way to go, but i'm not entirely sure about this.
Does anyone have design specs for a good cabinet? Or links?

Also, I have been thinking about alternative materials for construction. My thoughts are for a poly-carbonate plastic. This can be purchased in sheets up to 1" thick. Simply cut to size and glue with a solvent glue. Very strong, durable, lightweight and easy to manufacture. Also you dont need to cover the box...colours include black, white and clear. Different plastics have different acoustic properties, so it may be 'hit and miss' to get it right first time.

Any ideas will be much appreciated.

Cheers, Pete

Jon Light
Member

From: Brooklyn, NY

posted 21 November 2004 02:41 PM     profile     
http://www.webervst.com/enclosures/index.html

You will find links to specs and calculating utilities at the top of the page here.


Larry Bell
Member

From: Englewood, Florida

posted 21 November 2004 06:44 PM     profile     
I would say look at the Peavey Nashville 115e speaker cabinets. The dimensions and design were really good for steel guitar. Unfortunately, they don't make them any longer, but the design is excellent, IMHO.

A few folks use closed back cabinets, but the VAST majority of steel players use speakers in open back cabinets.

I'd be interested to hear the results of any experiment you do with a material other than wood, particularly those lighter in weight than wood.

------------------
Larry Bell - email: larry@larrybell.org - gigs - Home Page
2003 Fessenden S/D-12 8x8, 1969 Emmons S-12 6x6, 1971 Dobro, Standel and Peavey Amps

Dave Grafe
Member

From: Portland, Oregon, USA

posted 22 November 2004 01:35 PM     profile     
Whatrever material you use you should take steps to avoid the box itself from becoming a vibrating surface. That is why the best sounding cabinets are made of stiff, dense material like particle board, OSB or thicker plywood. Thin plastic in particular could be a real problem unless you find some way to stiffen all of the surfaces.

Keep us posted --

Dave

------------------
Dave Grafe - email: dg@pdxaudio.com
PDX Audio
Music

1978 ShoBud Pro I E9, 1960 Les Paul (SG) Deluxe, 1963 Precision Bass, 1954 Gibson LGO, 1897 Washburn Hawaiian Steel Conversion


Donny Hinson
Member

From: Balto., Md. U.S.A.

posted 22 November 2004 04:34 PM     profile     
Polycarbonate is light? Maybe you have access to some expanded form of this material, but standard full-density polycarbonate is almost twice as heavy as plywood! I have a piece in my shop that's about 6" x 12" (1" thick), and it's weighs over 3 pounds!

Speaker manufacturers use plyood and particle board because it's the lightest and cheapest material that works well in the application. If covering it seems a big deal, then don't! Paint it flat or semi-gloss black paint, and just touch it up with black liquid shoe polish when necessary. (That's a "trick" I learned from playing in rock bands! )

johnnyb
Member

From: Wendell, NC, USA

posted 22 November 2004 06:53 PM     profile     
.

[This message was edited by johnnyb on 04 June 2005 at 07:42 AM.]

Rick Johnson
Member

From: Wheelwright, Ky USA

posted 23 November 2004 04:30 AM     profile     
Johnny,
I agree with you, good old fashioned
pine is my choice too.

------------------
Rick Johnson

jay thompson
Member

From: east peoria, il USA

posted 23 November 2004 06:43 AM     profile     
Pete, trying to send a couple of examples for cabinet design but your email address does not work. Regards, Jay Thompson

[This message was edited by jay thompson on 23 November 2004 at 06:51 AM.]

Pete Knapton
Member

From: Christchurch, New Zealand

posted 23 November 2004 08:50 PM     profile     
I've been away for a few days.

Jay, i've sent you an email for you to reply to.

Jon, I've chased up the links and waiting for a reply. Thanks.

Donny, maybe i've got it wrong about the weight of polycarbonate. I have some old EV100s PA cabinets of polycarbonate, which i thought were light??? I'll follow that up with the plastic guru and see how it compares with ply woods or particle board.

My guitar tech advised that i could build the cabinet with clear transparent plastic and have colourful flashing lights inside!...just in time for Christmas.

Cheers, Pete

Donny Hinson
Member

From: Balto., Md. U.S.A.

posted 25 November 2004 05:42 PM     profile     
Pete, there are some cabinets made of PC, but the ones I've seen are 1-piece (molded) designs. They're pretty thin, maybe 1/4"-5/16" thick. You can get away with that thickness in molded cabinets, especially those with no large flat surfaces, but making it from flat sheets would require more thickness, to reduce unwanted cabinet resonance. And then, I feel most of the advantages of PC would be lost.

But that's not saying you couldn't try it!

David Spangler
Member

From: Kerrville, TX USA

posted 28 November 2004 08:52 PM     profile     
Pete, I could send you a freeware speaker cab design program. I have used it for EV, JBL, Black Widows, Eminence and others with good results. For your application, I would recommend tuning the cabinet to 72Hz. The results will probably be different for the JBL and the Celestion, but by changing port tubes, you might be able to make the same cab work for both.

On a related subject, I modified a Peavey Nashville 115e cabinet by replacing the back with a panel that covered the entire back except for a 1" rectangular port. That improved the performance by tuning it to 72Hz and getting consistent results in each venue.

------------------
David Spangler

James Quackenbush
Member

From: Pomona, New York, USA

posted 29 November 2004 12:31 PM     profile     
David,
Could you shoot me that prorgram if you don't mind ?....Thanks for your time....
Sincerely, Jim
Pete Knapton
Member

From: Christchurch, New Zealand

posted 01 December 2004 03:12 AM     profile     
David, Thank you, I've got the design specs for a Peavy Nashville 115e cabinet (thanks Paddy).
With your ported cabinet, where did you place the 1" port. Can you describe the location please?
Pete
Jim Simon
Member

From: Athol, Idaho, USA

posted 01 December 2004 01:26 PM     profile     
Pete: Some time ago I wanted to build cabs and got the specs for the 115E and some advice from Mike Brown at Peavey.
The Nashville 115E was;
18.5W x 22.5H x 14.375D
I front loaded the speakers and used a removable half back. Used birch ply. They sound great to me.

Jim

David Spangler
Member

From: Kerrville, TX USA

posted 02 December 2004 07:11 AM     profile     
Hi Pete, I simply made the new back panel 1" shorter than the longest dimension of the back of the cabinet, resulting in a 1" rectangular port.

------------------
David Spangler

David Spangler
Member

From: Kerrville, TX USA

posted 02 December 2004 07:16 AM     profile     
James, check your e-mail for the program.

Here is a link to the website to download WINISD-Beta:
http://www.linearteam.dk/default.aspx?download=winisd

I have the Thiele/Small parameters for the Peavey Black Widows for those interested.

------------------
David Spangler

Brad Sarno
Member

From: St. Louis, MO USA

posted 02 December 2004 08:29 AM     profile     
Open back all the way! Closed with port sounds weird on steel and guitar. Ok for bass guitar. Open back cabinets have a midrange openness and warmth that has been proven to be the most musical sounding design over the years. It's very hard to beat the dimensions of a Session 400, Nashville 1000, Fender Twin, Sho-Bud, etc. Also try the same sized back plates to provide that same rear opening. That size cabinet is mathematically and acoustically correct for a 15" speaker and will give you very full low end. If you want a more choked or tight low end, you can try something smaller like a Webb 6-14E size. Even smaller is the LTD or Nashville 400 cabinet size which is actually designed for a 12" speaker, but it's been very popular for 15" steel speakers. It has greatly reduced low end response compared to the full size cabinets. That can be good or bad depending on what you're after.

Brad Sarno

David Spangler
Member

From: Kerrville, TX USA

posted 05 December 2004 08:52 AM     profile     
Brad, I agree that many closed/ported cabs sound weird for steel or guitar. In my experience, ported cabs that are not designed properly produce objectionable frequency peaks in the 100-300Hz lower midrange. A properly-designed cab will flatten response in the midrange and rolloff the bass frequencies to keep the cab from sounding too bassy and can protect the speaker from over-excursion.

Speaker cabs are very subjective and some pickers prefer 1-15, 2-12, 4-10, etc. To my (damaged) ears, Open-back cabs sound different in different rooms and outside and their tone is greatly affected by the walls, ceiling, and whatever is behind the cab which could absorb or reflect sound.

A humanitarian note: closed-back cabs may protect the hearing of whoever is behind the cab. Of course, most drummers I know have already fried their ears.

But, back to ported cabs. Cab design is of special interest to me and I enjoy the experimenting, like a hobby, with scientific basis. My personal favorites are the EVM15L in a 2 cu ft ported cab and the BW 1501-4 in the modified NV115e cab.

I would enjoy corresponding with others who are interested in cab design.

------------------
David Spangler

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