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Thread: 2245h Help required

  1. #1
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    2245h Help required

    I have a set of 2245h in mint condition purchased in the original boxes sealed 3 months ago. I have run the woofers in loaded horn cabinets from bentwood. I am using Bryston 4b in mono block to drive each sub. Bryston claims the 4 B puts out 800 watts into 8 ohms strapped. The JBl woofer is rated at 600 watts continuous pink noise. The cone started to separate from the voice coil approximately 1/8 around diameter. I had a jbl dealer remove the dust cap and recement the voice coil. When the dust cap was off the repair tech said the coil showed evidence of slight over heating. I seen the apparent discolouring on the coil ( not that i have seen an original coil to compare ) and wished i had take a picture to verify. The recementing seems to worked fine. I have a couple of questions to be answered.
    1. Could there be a faulty glue connection which caused the seperation?
    2. I checked out the JBL Pro Vintage section and I am not shure what this woofer is rated for. The Theile parameters are 300 watts contiuous sine wave and the jbl vebage says 600 watts Pink noise. Can someone tell me what the RMS wattage rate is before they melt down.
    3. If the wattage rating is 300 watts what should i replace the 2245's with. I need a driver that has a low resonence 25 hz. . These cabinet reproduce down to 20 hz and lower, no problem.

    I am using altec 416 8b mid bass loaded bentwood horn, JBL2482 bentwood mid horn and JBL2410 with 2301 masher on highs - controlled with a JBL DSC 280 crossover. Parasound six channel amp (80 watts per channel) driving each driver from the mid bass to high. and two bryston 4b's on sub bass.

  2. #2
    Administrator Mr. Widget's Avatar
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    The 2245H is a wonderful woofer that was designed before today's extreme bass and power levels were anticipated. You are obviously over driving the woofer... don't take it personally, movie theaters and pro sound companies across America ran into this problem and have switched over to the newer 2242H. It is also what JBL now supplies in their top of the line Synthesis systems. The 2242H can handle significantly more power and abuse. It also has less dynamic compression (the loss of SPLs as the driver heats up) so it will play more loudly after 30 minutes than most other woofers of similar power and sensitivity ratings.


    Widget

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    Hello
    Are you using a high pass filter on the the subs to prevent over excursion of the speakers from sub low frequencies. You should ba able to program it in the 280. I would suggest 25hz.

    Mike Caldwell

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    jbl 2245h

    hello. can the 2242h cone be install in the 2245h frame. also I had my crossover custom built from dss sound labs I have 2245h/2202h/2425h/2404h the crossover freq is 200-1200-5000 and has a 95 db at 1 watt . what do I have to change in the crossover to bring every thing up to 99 db at 1 watt. the jbl 2245h is 95 db at 1 watt and the 2242h is 99 db at 1 watt

  5. #5
    Administrator Robh3606's Avatar
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    can the 2242h cone be install in the 2245h frame.
    Simply no. Different gaps and motors.


    what do I have to change in the crossover to bring every thing up to 99 db at 1 watt.
    On an electronic crossover??? You can adjust the gain on the drivers or overall for the channel. That's artificial. You can't change the basic driver effciency unless you horn load or in the bass or you get the drivers to couple which adds 6DB and room gain which is variable and frequency dependant. Other than that, unless I missed something that is set in stone.

    Rob

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    jbl 2245h

    Thanks Robh 3606 for the info on the woofer. my crossover is passive

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    I still haven't found out what the correct RMS wattage rating is on the 2245h. Will it take 600 watts rms

  8. #8
    Administrator Robh3606's Avatar
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    Use the data sheet here:

    http://www.jblpro.com/pages/components/2245h.htm

    No if you look they define the 600 continuous music and 3dB above the sine/RMS so it's a 300 watt woofer which is probably what the T/S has it specified at with PE.

    Rob

  9. #9
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    Quote Originally Posted by Mike Caldwell
    Hello
    Are you using a high pass filter on the the subs to prevent over excursion of the speakers from sub low frequencies. You should ba able to program it in the 280. I would suggest 25hz.

    Mike Caldwell
    I tried that and seem to loose the Kick drum punch. I tried rolling off at24 db per octive at 21 hert. I believe that my problem originated from Rap play by a younger family member during a party. I should have eq'd out some bass as his music is extremely bassy. The jbl dealer agreed this may have been the cause, possibly even from Suare wave effects used in rapp. I preffer regular music rather than rapcrap. Kids today you gotta loveem

  10. #10
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    Quote Originally Posted by Mr. Widget
    The 2245H is a wonderful woofer that was designed before today's extreme bass and power levels were anticipated. You are obviously over driving the woofer... don't take it personally, movie theaters and pro sound companies across America ran into this problem and have switched over to the newer 2242H. It is also what JBL now supplies in their top of the line Synthesis systems. The 2242H can handle significantly more power and abuse. It also has less dynamic compression (the loss of SPLs as the driver heats up) so it will play more loudly after 30 minutes than most other woofers of similar power and sensitivity ratings.


    Widget
    What is the power rating for 2245 ---600watts rms

  11. #11
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    Normally a high pass filter will actually tighten up a system by reducing cone over excursion and by preventing the power amp from wasting power trying to amplify frequencies outside of the speakers design. Most kick drum thump/punch is in the 50hz to 70hz range. In most music there is not much in the area around 20hz. Special effects, synthesizers, true pipe organ recordings can be the exception. I think the low B on a bass guitar is only something like 32hz. I'm not familiar with your speakers but how do they state the 20hz rating, many are not flat down to their low end cut off but are rated to say -3db at 20hz some will even rate them at a lower db level cut off per a given frequency.


    Mike Caldwell

  12. #12
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by jbldriven
    What is the power rating for 2245 ---600watts rms
    No, as Rob said it is 600 watts program... 300 watts rms. The 2242 is 800 watts rms, and has greater sensitivity.


    Widget

  13. #13
    Senior Member Ian Mackenzie's Avatar
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    I am surprised about the thermal damage, it could be from a previous user.
    or possibly your amp is bleeding dc into the driver but that is unlikely

    Even with 800 watts, that is well within the dynamic capability of these woofers according to Greg Timbers original 2245 subwoofer article. If you are attempting to use it for Pro sound reinforcement they might be unsuitable.

    You might also check the tuning of the boxes, they should be tuned b/n 28-30 hertz for the 2245. I have never heard of horn loading the 2245 if I ead your post correctly!

    Ian

  14. #14
    norealtalent
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    I recently purchased 10 identical factory JBL kits and 8 of 10 had faulty glue joints at the cone to coil former. There were many large gaps where the glue didn't touch one or the other. The two good ones were NOS, the 8 bad were freshly ordered. What does that say for anything else coming out their doors nowadays? I know mistakes happen but 100% garbage is inexucesable for any reason. They should never have made it by QC and the fact that they did is indicative of quality being sacrificed for the bottom line.

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    When you let the bean counters take over a company the quality always goes down.
    Vlad

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