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Thread: Replacement for DIY B460 Subs

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    Senior Member svollmer's Avatar
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    Replacement for DIY B460 Subs

    Hello all,

    Iím currently using two of the B460 clones from the Audio article by Greg Timbers: http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm . I built the version with the 12 cubic foot cabinets and have been extremely pleased with their performance. Iím moving into a larger room and was planning on building one of two more of them, until I saw the ASB7128 subwoofer on JBLís site: http://www.jblpro.com/catalog/general/Product.aspx?PId=300&MId=2 . While it doesnít go as low as the 2245H subs, it looks like I might be able to EQ it to achieve low bass because its output at 25Hz is 135 db continuous (141 peak!!!).

    My goal is to save space and I thought maybe one of these with EQ could replace four 2245H drivers. Does that make any sense, or am I way off base in my thinking? If anyone has any opinion on the quality of bass I might expect from a high output PA sub, Iíd appreciate that too. I expect not too many, if any, has heard this beast, but I welcome even your educated speculation.
    I also havenít been able to find a cost on this thing, so that might rule it out for me once Iím able to get one. In the meantime, Iím just curious as to what you all think.

    Thanks!

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    Senior Member hmolwitz's Avatar
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    Nice thing about those is if you cannot afford an amp to drive them you can probably plug them straight into the mains. Big Stuff!!!!!!

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    Senior Member Loren42's Avatar
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    Quote Originally Posted by svollmer View Post
    Hello all,

    Iím currently using two of the B460 clones from the Audio article by Greg Timbers: http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm . I built the version with the 12 cubic foot cabinets and have been extremely pleased with their performance. Iím moving into a larger room and was planning on building one of two more of them, until I saw the ASB7128 subwoofer on JBLís site: http://www.jblpro.com/catalog/general/Product.aspx?PId=300&MId=2 . While it doesnít go as low as the 2245H subs, it looks like I might be able to EQ it to achieve low bass because its output at 25Hz is 135 db continuous (141 peak!!!).

    My goal is to save space and I thought maybe one of these with EQ could replace four 2245H drivers. Does that make any sense, or am I way off base in my thinking? If anyone has any opinion on the quality of bass I might expect from a high output PA sub, Iíd appreciate that too. I expect not too many, if any, has heard this beast, but I welcome even your educated speculation.
    I also havenít been able to find a cost on this thing, so that might rule it out for me once Iím able to get one. In the meantime, Iím just curious as to what you all think.

    Thanks!
    I did not see the distortion rating for the drivers. I guess that would be my biggest question, but if you are just thinking of limiting the boost to no lower than 20 Hz, then it would seem like a doable approach.

    Below 20 Hz you should probably cut off at a high roll off rate to prevent excessive cone flapping and associated noise.

    Is this for home stereo listening? If so, if I ever come over remind me to bring 30+ dB ear plugs.

    I guess I should ask what you are trying to accomplish?

  4. #4
    Senior Member svollmer's Avatar
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    Yes, this is for home listening. I don't listen too loud (well, not always ), but I have become accustomed to the nice infrasonics I can get from the two 2245H. The reason I use two now is because of how little they have to work to achieve the volume and extension I like. Since I'm moving into a larger room, I was going to build another one or two to keep distortion to a minimum.

    I'm using an Audio Control Richter Scale III x-over becuase I couldn't locate a BX63A when I built the subs. To date, I've never even had to use a boost for the lowest frequencies. The crossover frequency I'm using is 40Hz (18 db/octave). I built the 25 Hz unassisted box, which gives the same output as the B460 with the low boost of the BX63A.

    I currently use an Adcom GFA-555II bridged mono, but am considering a Crown K2 or maybe a Crown Powerbase 3 because of their high damping factor.

    So what I'm really trying to accomplish is replicating what I get from two subs now (three or four in the new room) without having four 12 cubic foot boxes stacked in the corner. I thought maybe that pro sub might be strong enough to accomplish that.

    Thanks for your replies!

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    Senior Member Loren42's Avatar
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    Quote Originally Posted by svollmer View Post
    Yes, this is for home listening. I don't listen too loud (well, not always ), but I have become accustomed to the nice infrasonics I can get from the two 2245H. The reason I use two now is because of how little they have to work to achieve the volume and extension I like. Since I'm moving into a larger room, I was going to build another one or two to keep distortion to a minimum.

    I'm using an Audio Control Richter Scale III x-over becuase I couldn't locate a BX63A when I built the subs. To date, I've never even had to use a boost for the lowest frequencies. The crossover frequency I'm using is 40Hz (18 db/octave). I built the 25 Hz unassisted box, which gives the same output as the B460 with the low boost of the BX63A.

    I currently use an Adcom GFA-555II bridged mono, but am considering a Crown K2 or maybe a Crown Powerbase 3 because of their high damping factor.

    So what I'm really trying to accomplish is replicating what I get from two subs now (three or four in the new room) without having four 12 cubic foot boxes stacked in the corner. I thought maybe that pro sub might be strong enough to accomplish that.

    Thanks for your replies!
    Personally, I would wait and install them in the new room and see what you get.

    For one thing the room will be a totally different set of variables to contend with and the room gain will probably be different, too.

    Two 18" 2245Hs should provide an awful lot of SPL in just about any room in any house.

    What is the current size of your listening room and how big is the new room?

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    Senior Member svollmer's Avatar
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    My current room is 20 x 22 x 7.5. My new room will be 18 x 30 x 8. So it's about an additional 1,000 square feet.

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    Quote Originally Posted by svollmer View Post
    To date, I've never even had to use a boost for the lowest frequencies. The crossover frequency I'm using is 40Hz (18 db/octave).
    First of all, crossing over that low cuts about 5 dB of efficiency right out of the equation so the 2245H drops from 95 dB/W/m to 90 dB/W/m. This is a normal phenomenon so no biggie.

    Secondly, the bandwidth of the driver simply by crossing it over that low becomes completely different than one would expect. I would imagine that particular configuration is probably 3 dB down around 20 Hz with usable response down to about 16 Hz and that would be without any room gain added in.

    Find yourself another 2245H or two if you really think you need them. The new stuff is really neato but it won't touch 2245H's in those huge boxes.

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    What about those bass bins (I think that was what they were) that held 2 2245? that should have been efficient as all..

    Next listening party at your house, bass will be the theme!!!!

    Mark
    Think center channel for 250TIs; (2) 108s, a 104 and a 44ti, now what?

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    Senior Member svollmer's Avatar
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    4313B: I had no idea about the changes you describe by crossing over so low. What you describe matches my experiences exactly. I have several CD's with with infrasonic information (mic stand bumps, HVAC systems turning on, etc.) that I never hear with commercial subs. I was wondering how my sub tuned to 25 Hz went so low. I assumed it was room gain from them being in a corner. Fortunately, I have extra 2245H drivers. Your comments are much appreciated. It looks like I'll be building one or two more boxes.

    Does anyone know how to wire three 8 ohm drivers in series/parallel? If I go with three, I'll bridge an amp to run mono. If I go with four, I'll use two mono amps or a stereo amp for 2 subs so it sees a 4 ohm load.

    Mark (Opimax): I think I can make it on the 11th to your listening party; family plans are changing. And yes; when (FINALLY!) I get my basement done, all are invited over for some fun. I'm working on it daily!

    All: thanks for your input and advice.

    Steve

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    Heather [Senorita member] hjames's Avatar
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    Uh oh -- the brown note symphony!

    Sounds like BIG fun!
    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

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    Grat , glad you can make it. If I had to be "done" to have people over it wouldn't happen! I invited people over to design the finalized product, they think its going to be fun, lol.

    When I came over I thought I remember you had some 18s in boxes, what happened to them?

    Mark
    Think center channel for 250TIs; (2) 108s, a 104 and a 44ti, now what?

  12. #12
    Senior Member svollmer's Avatar
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    Those are the same two boxes as you saw. If you remember, they were in an unfinished basement piled high with junk and I was listening to two-channel in a small sitting room upstairs. That's still the same, but I've moved the HVAC ductwork, water main, and lolly columns (with a design by a structural engineer so the house wouldn't fall on my head!) and am finally framing the room up.

    I guess my plans will be to build one or two more of those boxes for the room.

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    Quote Originally Posted by svollmer View Post
    Those are the same two boxes as you saw. If you remember, they were in an unfinished basement piled high with junk and I was listening to two-channel in a small sitting room upstairs. That's still the same, but I've moved the HVAC ductwork, water main, and lolly columns (with a design by a structural engineer so the house wouldn't fall on my head!) and am finally framing the room up.

    I guess my plans will be to build one or two more of those boxes for the room.
    Sounds like a cool project overall and a labor of love to boot. Perseverance is the key, and you'll be done one day. Having a really good room really blows the heck out of everything. Good luck.
    In.

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    jbl srx 728s

    looking to use a jbl srx 728 at home for my home theater does any buddy have any idea how this sub will work at home thanks

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