speaker cabs, closed, open or ported

Tom Wicks · Post by **Tom Wicks** » 1 Apr 2003 3:51 am

well guys I`m almost finished the cab. for my 12 inch eletro-voice speaker and the quistion is, should the back be closed,open or ported and if so why. your replys will be much appreciated.

James Quackenbush · Post by **James Quackenbush** » 2 Apr 2003 6:27 am

Tom,
Closed back with no port does not allow good speaker movement...

Open back speakers allow for an airy tone that comes from both the front and back of the speaker cab

Closed back ported speaker cabs will allow for more bass, and have a more direct, punchy tone to them...

Then you can go with a semi closed back cab which has a smaller opening in the back...This will give you the porting you need, and will also give you more bass than a totally open back, and still give you sound coming out of the back of your amp...It's a win/win situation....This is the design I like..Very similar to what you see in the Evans amps with small opennings in the back....

Hope this helps....

Scott Swartz · Post by **Scott Swartz** » 2 Apr 2003 7:37 am

For optimal bass response, you size the box per the TS parameters of the speaker you are using. Or, if the box is built already I guess you could calculate which approach, sealed, round ported, slot ported is best for your box.

Check out this thread for a discussion of this and some links
http://steelguitarforum.com/Forum11/HTML/003427.html

Erv Niehaus · Post by **Erv Niehaus** » 2 Apr 2003 7:59 am

I had a fellow build me a couple of enclosures a few years ago and he said they were "tuned" to a C, I think he said. What is this all about?

David Doggett · Post by **David Doggett** » 2 Apr 2003 8:17 am

Erv, this sounds wierd to me. The object is to tune the cabinet to the frequencies where the bass response of the speaker begins to drop off. This boosts the response there and thus extends the lower frequency range of the speaker. Unless it just happens that the speaker drop off point is near C, arbitrarily choosing a note like that doesn't seem to follow the normal logic of tuning speaker cabinets. But I guess if you do have a choice of notes near the drop off region you could pick one and tune for it. C is not a bad choice for general music, but for country I think I'd go for G, for blues and rock either E or A. But I'm no sound engineer, I'm just speculating.

Gene Jones · Post by **Gene Jones** » 2 Apr 2003 9:40 am

Whatever it is.....Gerry Walker of Stereo-Steel has it "nailed"! www.genejones.com

jay thompson · Post by **jay thompson** » 2 Apr 2003 10:17 am

Tom,

I answered this same question like this. How many closed back steel amplifiers do you see?. It occures to me that if closed back was the way to go there would be more of them available.

Jay Thompson

------------------

David Doggett · Post by **David Doggett** » 2 Apr 2003 10:53 am

Jay, I think it's just because open back combo amp cabinets are cheaper. If a combo amp is closed, you have to separate the electronics from the speaker chamber. Extension speaker cabinets tend to be closed. I think a closed ported speaker/cabinet system is more efficient and louder. Just my marginally informed impressions.

jay thompson · Post by **jay thompson** » 2 Apr 2003 11:41 am

Dave,
I have two sets of cabinets,one set with 12"BWs, one set with 15"BW's. I used the Nashville 400 cabinet as a guide for the 15" cabinets minus the amp head housing of course. I find that with the cabinets setting near a wall,12" to 14", the sound reflection is larger than a ported cabinet. The 12" cabinets are proportionately smaller and perform as well. If the speakers were to be miked a ported cabinet may be an advantage.

Regards,
Jay Thompson

------------------

Donny Hinson · Post by **Donny Hinson** » 2 Apr 2003 5:20 pm

Open-back cabinets are cheaper and lighter, and they give good high-end response. They're not very efficient (5-10%), and they don't help much on the low end. They sound very "lively" over short distances, but don't "throw" well over long distances, and since they offer almost no damping, you'll have to be careful how hard you push them.

The ported (bass-reflex) cabinet is heavier, and costs more, and it gives much better low-end response, but at the sacrifice of the highs. The mids are "punchier", too, and the efficiency is a little better (8-13%), as well. Since they do offer some damping, they can be pushed a little harder than an open-back cabinet. Their sound "throws", or projects very well, but the sound to the sides is minimal, and almost non-existent to the rear.

If you like round, full tones, go with the ported design. But if you like sparkling highs and wide distribution, go with the open-back.

Jim Eaton · Post by **Jim Eaton** » 11 Apr 2003 1:23 pm

I use my 76" Session 400 W/15" JBL & and an Alembic extension cabnet W/2 Altec 12".
The Alembic cabnet is "closed". The blend of the Session 400 being open and the extension being closed is very nice to my ears.
JE:-)>