AudioCircle

Audio/Video Gear and Systems => Open Baffle Speakers => Topic started by: 077 tweeter on 20 May 2011, 02:34 pm

Title: advice on an OB project
Post by: 077 tweeter on 20 May 2011, 02:34 pm

I want to use old jbl 12" d123 extended range speakers on an OB.I might use a subwoofer. The d123's go out to 7kc,where I add jbl 077 horn tweeters. The d123's are 98 db efficient,fs of 40hz,qts of .45,and a vas of 4.5 cubic ft. What size OB board should I use? should it be flat only,or use wings? Thanks for any advice.Rudy( 077 tweeter).

Title: Re: advice on an OB project
Post by: DanH on 22 May 2011, 03:44 am

See these sites. They are a good starting point:

http://www.quarter-wave.com/ (http://www.quarter-wave.com/)
http://members.myactv.net/~je2a3/open.htm (http://members.myactv.net/~je2a3/open.htm)

Title: Re: advice on an OB project
Post by: Badwater on 23 May 2011, 12:34 am

I did a similar project with and EVSP12B.  I am very satisfied with the result. 

Sp12b high passed at 200 hz passive.  Fostex t90 with a cap very high and Alpha 15A in an H frame driven by a low powered plate amp.  This sounds way better than it should.

Bill

http://gallery.me.com/marilynladieu#100295

Title: Re: advice on an OB project
Post by: scorpion on 24 May 2011, 11:29 pm

Actually, I don't think Bill's outfit could be any bettered at all.

/Erling

Title: Re: advice on an OB project
Post by: Badwater on 25 May 2011, 10:31 pm

Thank you Erling. 

The next phase of the project is to implement a MiniDSP and upgrade the amps driving the Alphas.  i built a 4 Channel Class D Audio kit to do this.  The amp is wonderful.  I just have figure out how I am going to sneak everything into the living room without my wife noticing.

Title: Re: advice on an OB project
Post by: scorpion on 27 May 2011, 03:01 pm

My be I should have been a bit more articulate.
I think the adding of an H_baffle bass is a very sound idea, because you would never be able to regain bass OB-wise with this JBL-unit.
So H-bass or some ohter U- or unit flat OB based could be fine.

About the EV-units I have no real idea how they sound.

/Erling

Title: Re: advice on an OB project
Post by: Badwater on 28 May 2011, 01:55 pm

I second Erling on the H-Frame.  Add a good tweeter to your JBL and you should be in for a treat.

The EVSP12B units or ElectroVoice are vintage drivers that I bought new in 1975.  They literally have 1000s of hours on them.  To my ears they are every bit the equal to a pair of Fostex 166ESR that I have. I have enjoyed them very much over the years.