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Thread: Isobaric 2245

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    Isobaric 2245

    Quick question. If I build full 10cu. cabs anyway, would using 2 per cab isobaricly not be an advantage? I happen to have 4 2245 with a 10cu. build plan. I would effectively have 20cu. cabs +or-. Is there a benefit to this? I'm not concerned about efficiency. What kind of extension would be possible? What effect on transient behavior? TIA

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    Senior Member Champster's Avatar
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    Quote Originally Posted by gasfan View Post
    Quick question. If I build full 10cu. cabs anyway, would using 2 per cab isobaricly not be an advantage? I happen to have 4 2245 with a 10cu. build plan. I would effectively have 20cu. cabs +or-. Is there a benefit to this? I'm not concerned about efficiency. What kind of extension would be possible? What effect on transient behavior? TIA
    I posted this same question months ago and didn't get many (helpful) responses. I think it is because not a lot of people have the means to devote this much money to a subwoofer. Thats not a slam, just the reality and therefore not much of an informed base to comment.

    What is your goal is with this subwoofer? I have 2-2245's each in 9cf cabinets and love them. I use them below 35 hz and love them. They go plenty deep enough with enough power and control to be very impressive. If you really want to reduce distortion, go the Isobaric path. If you want greater output, double them up. I have a pretty good sized room and really like listening loudly and don't need the output of 4 18" subs.

    So, what are your design goals?

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    Senior Member grumpy's Avatar
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    I like to check numbers before cutting wood.
    A quick dry run in WinISD might provide some insight as to why folks aren't drooling all over this idea.
    The trade space is pretty severe (e.g., power required vs output)

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    Quote Originally Posted by Champster View Post
    I posted this same question months ago and didn't get many (helpful) responses. I think it is because not a lot of people have the means to devote this much money to a subwoofer. Thats not a slam, just the reality and therefore not much of an informed base to comment.

    What is your goal is with this subwoofer? I have 2-2245's each in 9cf cabinets and love them. I use them below 35 hz and love them. They go plenty deep enough with enough power and control to be very impressive. If you really want to reduce distortion, go the Isobaric path. If you want greater output, double them up. I have a pretty good sized room and really like listening loudly and don't need the output of 4 18" subs.

    So, what are your design goals?
    I went through that thread. My point is I'm not trying to save space. And I'm not concerned about -3db. The plan I have has been put together by the crew here. Essentially a fully active franken-4345 with 2245, 2206, 2390, and 2405. But I just happen to have 4 2245s. Since everything up top is bigger than life, I'm thinking I might as well carry the theme all the way down. I've also noticed some comments about the upper range of the 2245 being a bit 'muddy'. So if there is a net gain in performance, I'd love to use all 4. Again, I'm not concerned about efficiency since they will be fully active. I have plenty of power to drive them.

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    Senior Member Ian Mackenzie's Avatar
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    You are more likely to get a smoother bass from 4 sources spaced around the front of the room than 2.

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    I know you're right Ian. But I want to build a pair of stand alone speakers. Help can come at any time thereafter.

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    J.A.F.S.
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    TCB

    Quote Originally Posted by gasfan View Post
    I know you're right Ian. But I want to build a pair of stand alone speakers. Help can come at any time thereafter.
    What about building a triple chamber bandpass enclosure? I built four of them with qty TWO 2245H in each enclosure. The bass is prodigious.
    Amazed I'm still alive!
    Tim

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    In theory isobaric will only let you save some volume compared to a single driver.

    Here is an example of one of Mr Willy Peters' projects:
    http://www.axiomaudio.net/realisations1.php
    It is similar to yours, with a pair of 18" in isobaric configuration per side.
    He is adamant that this isobaric configuration is the best there is

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    Quote Originally Posted by loach71 View Post
    What about building a triple chamber bandpass enclosure? I built four of them with qty TWO 2245H in each enclosure. The bass is prodigious.
    I don't want to hide them or cut them off that low. I also want to preserve the impact of the 2245.

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    Quote Originally Posted by pos View Post
    In theory isobaric will only let you save some volume compared to a single driver.

    Here is an example of one of Mr Willy Peters' projects:
    http://www.axiomaudio.net/realisations1.php
    It is similar to yours, with a pair of 18" in isobaric configuration per side.
    He is adamant that this isobaric configuration is the best there is
    I like it.

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    Senior Member Lee in Montreal's Avatar
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    Going in isobaric indeed allows to use half the cabinet volume. If the usual cabinet volume for one woofer requires 10cft, then you can run both woofers in 5cft. But you'll waste twice the amp power.

    If you have four 2245 and don't know what to do with them, perhaps you can use two close to the main speakers, and two in opposite corners. You should be able to fill the room evenly, with a massive sweet spot in the center ;-)

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    Senior Member Ian Mackenzie's Avatar
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    If you simulate the port area and length in the smaller volume the port is much larger.

    That might not be practical unless you are able to have a metre or so of 6 inch pic pipe.

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    Quote Originally Posted by Lee in Montreal View Post
    Going in isobaric indeed allows to use half the cabinet volume. If the usual cabinet volume for one woofer requires 10cft, then you can run both woofers in 5cft. But you'll waste twice the amp power.

    If you have four 2245 and don't know what to do with them, perhaps you can use two close to the main speakers, and two in opposite corners. You should be able to fill the room evenly, with a massive sweet spot in the center ;-)
    The idea is to still use the same 10cu. volume. And since they are fully active, separate mono amp for each driver.

    I have four LSR&D Leach Superamp monos, two Model 101 stereo Leach amps, and two diy stereo Leach amps for a total of 12 channels. I will need just 10.

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    You can build a pair of "push pull slot loaded" boxes. The theory is that because all drivers are assymetric the result will be symmetric since one driver is mounted with the magnet out. The slot also creates a tighter coupling of the drivers than traditional mounting.

    On top of that you can do a closed enclosure and use a Linkwitz transform to get low bass from the box. Either an analog Linkwitz filter, or a digital one. You should design for a total Q=0.5 because this will have optimal cone damping.

    If I had four 2245, this is what I would do :-).

    Mårten

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    Senior Member Lee in Montreal's Avatar
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    Marchand also makes a Linkwitz transformer and so does Kef. actually Kef has different version. They are all called Kef Kube.

    http://www.marchandelec.com/wm8.html

    I had a Kef Kube 200 and it was a very good bass enhancer for that last octave.


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