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Old 16th October 2005, 08:17 AM   #1
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Default Open baffle afterburner?

Well after much deliberation i am intent on building a full dipole setup for my main listening area. I already have the sub setup done (4 el cheapo goldwood 18" subs) and am looking at the midrange aspect.

I like to listen to my music pretty loud and it looks like the eminence beta 12 tl (100hz and up) with the fostex ft 17h (ala afterburner style) will get me there. A few questions though.

1. If i run a single 2uf cap on the fostex, am i okay to let the eminence run wide open? Or should i throw a simple first order circuit on it to help keep the breakup modes to a minimum?

2. I am going to run a 31 band eq i have to help tune the dipoles. Should i still think about utilizing a zobel network or just keep the minimalistic approach?

3. Any opinions on the beta 12tl run open baffle? I can only find posts of it in BR designs.

Any suggestions or ideas are welcome to add to this design. I basically want a stero pair of speakers for under 250 bucks that are extremely efficient (wood is excluded).

Nate
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Old 17th October 2005, 10:53 AM   #2
JimW is offline JimW  United States
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Default afterburner

You should probably use the notch filter recommended by Thorsten. That driver has a rise in sensitivity from about 700hz through 2.5k (from memory, see eminence site for exact data). I use afterburner as my main speaker, sounds very good, I also use the fostex ft17h. Originally I had a simple 6db filter on the 12, but I thought it sounded a little better without, so now I allow the 12 to just roll off, use 1.5 cap on fostex. I also use a zoebel on the 12. I used dammar on the cones, clay on the speaker basket (they will ring like a bell, and I had planet 10 make some phase plugs, which I think are very well worth the money and effort. Good luck, and please post your results - I would like to know how they sond ob!
Jim
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Old 17th October 2005, 04:01 PM   #3
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Default afterburner

I would like to build this too, but I am confused when I look at Thorsten's notch. The values aren't clear to me.
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Old 17th October 2005, 08:17 PM   #4
JimW is offline JimW  United States
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Default notch values

From Thorsten's site, the notch is as follows: 8.2R/10w, 8.6uf, .65mh, these items are paralleled and the network is placed in series with the woofer. The zoebel: 6.8R/10w, 22uf, these two items are connected in series and placed across woofer terminals, after the notch filter.
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Old 17th October 2005, 11:35 PM   #5
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Default Re: afterburner

Quote:
Originally posted by JimW
You should probably use the notch filter recommended by Thorsten. That driver has a rise in sensitivity from about 700hz through 2.5k (from memory, see eminence site for exact data). I use afterburner as my main speaker, sounds very good, I also use the fostex ft17h. Originally I had a simple 6db filter on the 12, but I thought it sounded a little better without, so now I allow the 12 to just roll off, use 1.5 cap on fostex. I also use a zoebel on the 12. I used dammar on the cones, clay on the speaker basket (they will ring like a bell, and I had planet 10 make some phase plugs, which I think are very well worth the money and effort. Good luck, and please post your results - I would like to know how they sond ob!
Jim

The reason for lack of a notch filter on the 12lta is because i will be using an active eq.

What amp are you using to power them with and what interconnects are you using?

Nate
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Old 18th October 2005, 10:58 AM   #6
JimW is offline JimW  United States
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Default amp and interconnects

I use one of the following to drive them : Legacy 300b (mostly) McIntosh m-60, push-pull 2a3. I have also driven them with an Onkyo TX4500 mk2. The speakers sound good with all of these amps. I am using either cat5, or radio shack premium (I may have tin ears as I hear very little difference between these two cables). The speakers are fairly revealing of the differences in the amps. Speaker cabs themselves are wired with cat5, binding posts are used as split bolts to tie wires directly to speaker cables. Source is mainly cd player through diy 12bh7 linestage, although I will be adding vinyl to the mix in a couple of months (I don't have room in present set-up for my tt, but we are soon moving).
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Old 18th October 2005, 12:13 PM   #7
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Exclamation Afterburner open baffle

I emailed thorsten asking him the very same thing, with regards to using the eminence driver in open baffle, and he warned against it. The driver has a relatively low Qts (.5?) and therefore would not perform well OB.

He suggested the Ciare CH 250 10" which has a very high Qts (1.7?), is pretty sensitive (96db) and cheap (40 euros). if you search the forum you will find several threads discussing it. It seems to compare well with drivers costing many times more. I have a pair and plan to make a dipole system including a w-frame dipole woofer using two eminece alpha 15s per side. It appears the ciare may be difficult to get in the states, also the uk, it is avaiable in europe from www.spectrumaudio.de

Another option is the 8" Beyma 8agn which has a suitably high qts is less sensitive (92db) but is cheaper again (20 in the uk). seems to be more widely available. It doesnt go as low as the ciare (some use ithe ciare without woofer or tweeter), but since you have you woofer sorted that probably wont matter.

Look at the ciare threads and other options are mentioned, but it seems that the beta 12lt is not the best solution.

Cheers,

Ross
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Old 18th October 2005, 07:51 PM   #8
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Default Re: Afterburner open baffle

Quote:
Originally posted by rossco_50
I emailed thorsten asking him the very same thing, with regards to using the eminence driver in open baffle, and he warned against it. The driver has a relatively low Qts (.5?) and therefore would not perform well OB.

He suggested the Ciare CH 250 10" which has a very high Qts (1.7?), is pretty sensitive (96db) and cheap (40 euros). if you search the forum you will find several threads discussing it. It seems to compare well with drivers costing many times more. I have a pair and plan to make a dipole system including a w-frame dipole woofer using two eminece alpha 15s per side. It appears the ciare may be difficult to get in the states, also the uk, it is avaiable in europe from www.spectrumaudio.de

Another option is the 8" Beyma 8agn which has a suitably high qts is less sensitive (92db) but is cheaper again (20 in the uk). seems to be more widely available. It doesnt go as low as the ciare (some use ithe ciare without woofer or tweeter), but since you have you woofer sorted that probably wont matter.

Look at the ciare threads and other options are mentioned, but it seems that the beta 12lt is not the best solution.

Cheers,

Ross

Well with shipping costs from europe, considering i can't find ciare drivers they will cost a lot more than the beta's. Plus i already bought the betas on saturday so i will just make them work.

I believe with the active eq i have i can make em work. Hell if they don't do so well OB then i'll just put em in a box.

Something sealed that has a natural roll off or f3 about 100 hz would be awesome and probably not be too big. I don't have winISD or anything though so i'll have to download that eventually.

Nate
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Old 20th October 2005, 09:23 AM   #9
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somebody elses' reply would be greatly appreciated.

Nate
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Old 20th October 2005, 12:39 PM   #10
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Default Afterburner open baffle

Hi there,

I wasnt speaking from exprience, I have none, so I think you are probably right to give the eminence a go in open baffle if you have them, especially given that you can try this out with little cost and put them in a box if you dont like it. maybe try both.

Im trying to do something similar to what another member has done, with apparently gives stunning results for (relatively) little cost and effort, which may be helpful to you. Like you he is also using two 18" woofers open baffle with a single full range and tweeter. See peters post in the link below. He advised a zobel with the ciare, but I think he has now using lowthers which have a lower Q (perhaps similar to the eminence?) and Im not sure what he has done with these. Im affraid I cant adivse on the tweeter crossover, but a single cap seems to be the way to go. I think the f17h was used with the super 12 (at least one revison of it) which uses a modfied beta12lt so you might want to check the hammerdynamics site and have a look at the crossover for that.

Cloning the BassZilla Platinum
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