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Thread: Jbl Sub1500 15" Subwoofer 4 Ohm

  1. #46
    Dang. Amateur speakerdave's Avatar
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    Subwoofer for LSR32

    I already have plans to make a subwoofer with the 1400nd I have on hand--I bought these before the LSR 32's with another idea in mind.

    I know the 1400nd is not designed for subwoofer use, although I also know some people have done it. (I've read the G. T. suggests using them in pairs--Does he mean two on each side?) It's designed to work up to the mid hundred Hz and is excursion limited. But I thought the fact that the 1400nd has a neodymium magnet like the woofer in the LSR32 would make the two compatible. Besides, I already owned them.

    The LSR32 is so good in it's operating range that I did not want to touch it even to the point of putting an active crossover in front of it. I was going to cut the subwoofer in at 50 Hz and let the LSR32 run full range. It is 3 dB down at 53 (absolutely flat to 60). I thought with the 1400nd and the 252G running together below 50 Hz there would be plenty of bass with room rise.

    Now this thing comes along. For making a subwoofer to work with a speaker really good to 60 Hz it must be considered, especially since the 1400nd's would pay for the sub1500s and the cabinets and some SACD's.

    I need help with the concept of group delay. I take it from reading that the driver parameters, crossover and enclosure are all factors. Mr. Widget, how bad is it? Since the enclosure type is also part of the filter, would group delay be less in a sealed enclosure? Would placement elsewhere in the room, away from the main speakers but closer to the listening position, help or hurt the group delay issue?

    Would expert opinion on transient response prefer the 1400nd in 4.1 ft ported enclosure to the sub1500 sealed in the same size box?

    There are probably other questions I should ask.

    I need help thinking this through.

    Thanks,

    David

  2. #47
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    "Would expert opinion on transient response prefer the 1400nd in 4.1 ft ported enclosure to the sub1500 sealed in the same size box?"

    No. A properly designed vented system cannot beat a properly designed sealed system in transient response. Transient response is directly related to frequency response, the shallower the roll-off the better the transient response. One might want to read up on the pros and cons of sealed versus vented systems. Neither is the be-all end-all. This particular driver thrives in the sealed enclosure just like the original 121A/121H did.

    I looked at the numbers on this driver again and it will indeed match the old B212 in bandwidth when used in a 4.0 cubic foot sealed enclosure. Very impressive! A slightly smaller package than the old B380. All the bandwidth of the B212 with considerably more thermal and displacement limited power handling capacity and slightly higher sensitivity plus much lower distortion. What a deal!

    Anyway, one would do well to try both sealed and vented and choose the one they personally prefer.

  3. #48
    Dang. Amateur speakerdave's Avatar
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    OK. Thanks, Giskard.

    David

  4. #49
    Administrator Mr. Widget's Avatar
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    "I need help with the concept of group delay. I take it from reading that the driver parameters, crossover and enclosure are all factors. Mr. Widget, how bad is it? Since the enclosure type is also part of the filter, would group delay be less in a sealed enclosure? Would placement elsewhere in the room, away from the main speakers but closer to the listening position, help or hurt the group delay issue?"

    Ditto what Giskard said.

    I plan to try a pair of them in a pair of 4 cu ft enclosures that I have. I will try them both sealed and ported. The primary benefit of sealed is as Giskard pointed out, better transient response. There are two functional downsides to it's use in a sealed box. First it will require equalization, second it will not produce quite as much output at say 25Hz regardless of amplifier power. Below about 19Hz the sealed box will actually have greater maximum output though. According to BBPro in a 4 cu ft sealed box it will be able to produce a phenomenal 85 dB at 5Hz!!!

    Of course the audible differences between ported and sealed are purely subjective. I want to try both to see which I prefer.

    Now as far as group delay is concerned, a driver's group delay with a given tuning has no bearing on the system's time alignment. Placing a sub nearer or further from the rest of the system will not be affected by it's group delay. I am not sure of the definitive definition of group delay, but I think of it as how well a driver can pass a pulse or recreate it's portion of a square wave. As the group delay goes up the pulse will get more and more smeared.

    I hope this helps.

    Widget

  5. #50
    Dang. Amateur speakerdave's Avatar
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    Yes it does, and thanks.

    For reasons I may not be able to fully articulate, I'm going to go with the 1400nd's for now.

    One reason is that I know I would not want to make them go away without having tried them.

    I may miss out on the sub1500's, but that's OK. I'm not going to float another pair of woofers right now.

    I also think the 1400nd is going to be more to my taste in a woofer. I'm just not interested in sheetrock-loosening bass; I'm not an HT devotee, and I'm only mildly amused by organ pedal notes. I think I can lay enough of a foundation with the 1400nd's and the 252's running in common. I have a feeling that with the sub1500s I would end up crossing the LSR 32's out, and I don't want to do that.

    In the long run probably the best subwoofer for the LSR32's is the one in the LSR series that was engineered to work with them.

    Finally, I want to hang onto the 1400nd's as the basis of a shot at the M9500 later on.

    This has really helped, to be able to kick this around.

    Thanks again,

    David

  6. #51
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    "There are two functional downsides to it's use in a sealed box. First it will require equalization"

    If you are going to use it in a 1.5 cubic foot sealed box and if you don't mind the additional group delay the EQ adds. +3 to +6 dB of EQ in the low 20's should do. I would probably port it before adding any EQ to the 4.0 cu. ft. sealed box. In the 4.0 cu. ft. sealed box it will yield pretty much the same bandwidth as the old B212. If anyone doesn't think the old B212 has sufficient bandwidth then they aren't using it right. There were dealers all across the country back in 1977 who didn't have the first clue what to do with a subwoofer back when it first hit the market. Usually subwoofers have their drivers low to the floor so they pickup a bit of boundary reinforcement already. If you go vented, keep the driver up off the floor a bit. Another nice thing about sealed is they tend to drop at roughly the same rate a typical room rises so the net result is quite nice. JBL seems to be trying to accomplish this with their ported Bessel systems these days. Kind of like trying to compromise between the transient response of the sealed and the increased sensitivity of the vented.

    Speakerdave - I thought you had a pair of 2242H subs? Those are definitely one better than the REVEL15 if you can afford the real estate for their large enclosure requirements.
    Last edited by 4313B; 02-24-2004 at 08:48 AM.

  7. #52
    Senior Member JuniorJBL's Avatar
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    Question Specs of 1500 SUB

    is every one using the specs from the PE web site or the numbers Giskard posted?
    Some of the specs dont look the same. I do not know much about all the T/S parameters but it seems most software uses different T/S to get the same plot.
    Could someone possibly guide me in the right direction as to the T/S parameters that are required to get the right responce for a box program? It also seems that some T/S parameters have a different name even though they mean the same thing.
    I may not be asking the right questions so please enlighten me.
    Shane

  8. #53
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    Hey, these are too good to pass up. I am going to try a pair in eq'd sealed boxes. It kind of reminds me of a pair of McIntosh ML-1c's I had back in the seventies. Even back then they had fairly impressive LF capabilties for a low effeciency system.

    But, they will have to wait, my 4333 system in 4505 (remember, I am the guy stuck with the 4325's?) boxes are nearing completion. Just waiting for the paint to dry...........

    BTW Giskard, early measurements of your substitute L300 network are looking pretty good. Once I get all the drivers installed I'll do some more, accurate measurements.
    Charles.

  9. #54
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    Re: Specs of 1500 SUB

    The numbers I posted are from the actual JBL Engineering Design Specification. The numbers PE posted are from running one of the drivers they have in stock through their CLIO system. Vas is easily the most difficult measurement to take so keep that in mind.

    One must have a minimum of Qts, Vas, and Fs for most box modelling software. The more info you want out the more info you have to put in.

  10. #55
    Senior Member Don C's Avatar
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    I'm wondering how this would work in one of Parts expess's own 3.0cu ft ready made sub boxes.
    http://www.partsexpress.com/pe/showd..._ID=9385&DID=7

  11. #56
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    Quite a bit of difference in the FS and VAS - 'any reliable way to determine which is more accurate?

    John

  12. #57
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    Ok, I just briefly compared the two sets of TS parameters. My guess would be JBL ran their test after break in . The PE driver might not have been sufficiently broken in, if at all. Note that Vas is easily the hardest parameter to measure.

  13. #58
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    Originally posted by Don C
    I'm wondering how this would work in one of Parts expess's own 3.0cu ft ready made sub boxes.
    I suppose it could work. The internal standing wave would occur at ~ 380 Hz and it would be greatly amplified since it's a cube but it you crossed over real low it might not suck.

  14. #59
    Dis Member mikebake's Avatar
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    I'm going to posit that we'll see a number of designs from guys using this driver before long; make sure you guys keep us posted on your results, now ya hear!

  15. #60
    Senior Member JuniorJBL's Avatar
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    On the way!!

    The subs are on the way!! They should be here on thursday. I am working on designs from about 2-5 cuft. I will probably end up with one at about 2 cuft and one at about 4 cuft. I may cut a vent in the 4 cuft for further testing. Pics and stuff I will be collecting for the forum.
    Shane

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