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Thread: Wall mountable surround speakers to match 4675/4670's?

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  1. #1
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    Wall mountable surround speakers to match 4675/4670's?

    Hey guys, I recently refurbed some 4675's and 4670's that came out of an old theater and I'm really enjoying them. However I need some idea's for what to use on the back wall for rear center duty in a 7.1 setup.

    The theater supply house that I bought these from also has several 4647's with 4670 hf sections that I can get pretty cheap. I'm thinking about just gutting and building the components into smaller wall mountable speakers. Maybe run the 15's in a small sealed(and stuffed) cabinent with the horn on top. I'm not looking for much low-end...just good output down to the 80hz or so x-over point.

    More than anything i want them to have a similar tone to the other speakers.

    I had Klipsch rs-7's as rear centers for a little while but they just sounded too different and were easy to localize. I've considered 8340a's but I'm afraid they'll end up like the rs-7's and not blend well enough tonally.

    Any ideas...opinions...suggestions?

    Thanks,
    Ken

  2. #2
    Senior Member GordonW's Avatar
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    JBL 2225H in 2 ft^3 enclosure size, lined with 4" thick fiberglass on all the sides and back walls, port-tuned to about 50 Hz (two 4" diameter vents, 8 1/2" long each), looks to have flat pass-band response (no peaking above flat) and an f3 of about 65 Hz. Acoustic power handling is fine, with full-power available to below 50 Hz, without woofer over-excursion. You could reduce the port frequency down to 45 Hz (if needed, for tuning the bottom to reduce "boom"), and still have an f3 of 70 Hz or so, with good power handling (45 Hz in 2 ft^3 would need two 4" diameter vents, 11 1/2" long)...

    Sealed box, it's not gonna really do much below 105 Hz... and it's going to be acoustic-power-limited (ie, potential to bottom out) below 120 Hz, even in the optimal box size...

    Regards,
    Gordon.
    This Is Gordon's Page: www.geocities.com/gordonwaters

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    Excellent info...Thanks Gordon.

  4. #4
    JBL 4645
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    GordonW

    Let me see if I get you right mate, you what to attach JBL 4675 to the sidewalls. Man I thought I was going crazy, that sounds like a doable idea, but why not just go with a surround array of JBL 8340, or the 8330ís.



    Nearly all the best sounding commercial THX sound system cinemas that I have attended here in the United Kingdom, in the past use the three-screen JBL 4675-A, JBL 8330ís and JBL 4645 sub bass array clusters. And boy, do they sound out of this world, with films like (Star Trek) your home cinema will really jump to (Warp 8)!

    I would personally place x4 JBL 8330ís or 8340ís on the back wall, spaced out and placed at the correct height!



    The sidewalls surround array, should be made up of no less than, x4 for each sidewall, with the sides and back being driven by there own amplifier, and wired in (series) for the back and the sides.

    Now Iím not running the (Dolby surround-EX) decoding circuitry in the home cinema, instead Iím running a different version, but using Dolby Pro-Logic circuitry to do the surround back decoding. But I have re-plugged my home cinema so that I can run, split-surrounds via the Dolby Digital 5.1, in standard mode, where I switch on (A & B) on the (Marataz 1030) B is for the sides, and A is for an additional JBL surrounds.

    The centre back is made-up of a same JBL surrounds Control 1, but are placed in the centre line of the back.

    So you see if the decoding in by-pass of the (Dolby Surround-EX) will send the back half surrounds the split-surrounds, as centre back works with extracting the phantom signal from left and right, forward phase.

    Anyway Iíll be keeping an eye on this thread, and get some pictures up mate, this sounds like its going to be project that I wouldnít mind doing, only my home cinemas a whole lot smaller than yours, and I wouldnít have room to swing a cat if I had x3 JBL 4575-A!

    Good luck.

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    Actually I'm thinking about building a small wall mountable pair of rear center surrounds using a single 2225 and a 4645/2380 in each cabinent.

    I'm also thinking about taking the easy way and just throwing a pair of 8340a's back there. However I'm a little concerned about their ability to blend with my other speakers(4675's and 4670's) in a relatively nearfield environment like a home theater. My Klipsch's that I previously used as rear center's really didn't work well with the JBL's.

    Since JBL intends for the 8340's to be paired with the 4675 and 4670 in cinema apps. does that mean 8340's blend decently with the big JBL's?

  6. #6
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    No rear centers yet but here's a few pics:




    Not pictured is a JBL 4688tcb sub on the opposite wall from the 4642a and another 4670 surround in the back left corner. Everything is powered by QSC amps.

    Edit:
    The maggies(1.6qr's) are powered by a carver tfm-55x.

    -Ken

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