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Thread: JBL 4520 speaker replacement.

  1. #16
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    Oh ok. Do I need to set the crossover at 90Hz or will a higher crossover point work?

    Also am I limited to 500 watts or is the wattage limit 1,000 watts since I will have two 8 ohm 500 watt drivers in parallel?

    Now if the cabinet has any resonance at higher power levels how would I fix it?

    I figure that once all the speakers are fixed I won't need to run as much wattage to the speakers.

    Looking at the frequency response graph http://www.jblpro.com/pub/obsolete/L...nclosures2.pdf it looks like there's a slight dip of around 3db around 150Hz.

    Best thing for me to do is fix one cabinet then feed an audio generator through the amp and have a listen to frequencies 150Hz and below just to see what I'm dealing with.

    That way I can hear any frequencies where there are issues and figure out the best way to work around those issues to get the best possible sound I can out of the bass cabs.

  2. #17
    Senior Member Lee in Montreal's Avatar
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    Hey buddy

    If you are used to bass reflex cabinets, you have probably already realized that a lot of energy is wasted in absorption and that not much is actually output. Hence requiring big amps. Horns are way more efficient. All the energy sent to the driver is actually output. You will not need big amps to get good thumping. It is surprising to have loud music while the cone is barely moving. So, whatever amp you have picked will be good. Just make sure they never clip. Clipping = DC
    Your crossover frequency will be determined with what will play on top of the 4520s.

    Place your cabinets side by side to connect their mouth.

  3. #18
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    yes I'm used to bass reflex cabinets. Have two 1 cu ft ones with a 12" each in them in my home system and it takes lots of watts to keep up with the rest of the system.

    Never had a proper horn loaded bass cab, but I have heard the ones at the skating rink you posted a picture of and one of the ones that was working properly did indeed sound very good to me.

    So a 500 watt amp on each of four JBL 4520 cabinets loaded with the drivers I listed will go more than plenty loud enough for the skating rink?

    What you said about it being surprising to have loud music with the cones barely moving really hits home as it brings to mind how if a low frequency at high wattage is played into the speaker below the frequency the horn unloads at the cone goes from barely moving to suddenly moving a lot and can indeed self destruct in short order.

    Also if the cabinets should happen to vibrate should I put some bracing on the outside rear of the cabinets?

    With the Yamaha amp I'm using I can set the limiting to where the system cannot go any louder than a certain point which will be good as that will protect the whole system from over powering and keep the system from being damaged by DJs who love to jack up the bass knob on the mixer.

    In the case of the self destructing woofer I think the problem was the amp is way over powered for the speakers used which in normal cases is fine, but in the case of anyone and everyone having their hands on the mixer and the system being in disrepair one thing led to another and a woofer destructed itself.

  4. #19
    Senior Member Lee in Montreal's Avatar
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    If you run a digital crossover (which I suggest you do for better sound shaping and time alignment), you can set limiters.

    On the amps, you can also probably set a 28/30Hz high pass filter to protect the drivers.

    And set a new rules for your DJs... If they blow a woofer, they pay for it... ;-)

  5. #20
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    The Yamaha amps I'm going to recommend to the rink owner have built in DSP which will serve for the eq, crossover limiter and high pass filter for the woofers.

    That way they don't have to buy separate equipment with knobs for people to dick around with.

    No one will be able to dick around with the Yamaha amps as the whole front panel can be locked out with a code and the only ones who will know that code are me and the guy they have help with the sound system. Also with the settings stored on a thumb drive it will be easy to set it back to where it should be if someone should somehow figure out how to change things.

    My plan is to volunteer time on Saturdays to show people how to run the sound system properly.

    Concerning blowing speakers with the limiters and high pass it will be extremely hard to do, but I'm sure someone will find a way to do it anyways

    I'll mention to the owner that any equipment that breaks due to abuse should be paid for by whoever operated the mixer at the time it happened.

  6. #21
    Senior Member Lee in Montreal's Avatar
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    BTW if you have those on top, they shall be great. You can then probably crossover at 90Hz and get the kick bass out of the Bullfrog.

    Then what's on top of those? ;-)




  7. #22
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    That's the speakers which will be on top of the 4520s.

    On top of those will be a single Yamaha 6115H horn with Eminence PSD2002S-8 drivers with 1" to 1.4" adapters.

    The speaker stack is like this

    Yamaha horn
    Bullfrog
    4520

    Sadly the two Yamaha horns I opened were minus the original drivers and I found one in a storage closet minus the diaphragm.

    So the crossover between the Bullfrog and Yamaha horns will need to be 1.6KHz which is easily taken care of by this
    http://www.parts-express.com/eminence-pxb2-1k6-2-way-speaker-crossover-board-1600-hz--290-634

    I'm tempted to use the higher power Yamaha amp for both woofers in the 4520 and use the smaller Yamaha amp and have it three way active, but I don't think the rink owners can afford that plus that's just more to get miss adjusted and there will be no tweeter protection, whereas that Eminence crossover has tweeter protection.

    What I will do when I get it all together is play the system as loud as it should ever go then set the limiters on each amp to prevent it from going over that loudness level.

    I can see why the rink chose those components. They are very efficient and don't require a lot of watts. One amp was most likely an original one and it was a Yamaha only rated at 85 WPC, but it had went out and was not used. Goes to show that efficient speakers don't need much power to go loud.

    Will definitely experiment with the crossover point between the 4520 and Bullfrog.

    Sadly there isn't much info at all online about those particular Bullfrog speakers.

    Now I did find a complete minus the driver Bullfrog cabinet in a storage closet. Now if I could find the other three Bullfrog cabinets and the other four Yamaha horns I could recreate their whole original sound system only better due to the new Yamaha amps. I wouldn't even need any more amps as I can just parallel two of the Yamaha Bullfrog cabinets on each amp channel.

    Also I think that Yamaha amp has a setting to adjust impedance. Not sure what that's for unless it is to let the processing circuitry know what impedance the amp has to drive so it can optimize the amp section to the load impedance.

    Now the Bullfrog cabinets do have drivers in them, but I don't know what they are yet. If the drivers are not good the one 4520 had two Peavey Black Widow woofers in it (one self destructed) and I suspect there may be more of them. If I find four Black Widows in proper working condition would those be good for the Bullfrog cabinets? If so that would save them $319 in costs.

    The only thing that concerns me about using the Dayton Audio drivers in the Bullfrog cabinets is the frequency response graph towards the 1.6KHz crossover point where the off axis response starts to be different than the on axis response. Suppose the front loaded horn might take care some of the issues provided the horn can load the driver at that high of a frequency as the Bullfrog cabinets were most likely originally crossed over at 800Hz based on the Yamaha compression driver's listed frequency response.

    I am thinking of mounting the amps on top of the Yamaha horns so that they are easily accessible and in the air conditioned part of the rink, but I don't know if I should.

    Crossing over the Bullfrogs at 90Hz may be better because I may not need to eq below 60Hz as strongly.

  8. #23
    Senior Member Lee in Montreal's Avatar
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    Well, the 15" drivers in the Bullfrogs might hardly reach 1.6KHz. Even a clean 1Khz might be a challenge. It seems your Yamaha horns are quite incomplete. Compressors without diaphragms are literally worthless. May I suggest another combination on a budget.

    Two stations.

    Each station comprises two 4520 scoops side by side. Two bullfrogs (great for snare drum snap), one on top of the other. Maybe even only one single Bullfrog per station. And a JBL 2360 horn on top with 2" throat compressor. That shall be a simple 3-way system. And I suggest a digital crossover.

    One big amp feeds two 4520 on 4 Ohms (one amp per 4520 is better but more costly). One medium size amp used assymetrically : one channel feeds the Bullfrog. The other channel feeds the 2360 horn. Both amps located by the stations.

    The 2360 horns are usually cheap to get as they are huge and can hardly be shipped. They are basically cinema hardware that often gets crushed. The 2360 is designed for 500Hz and up. Pretty good until 12Khz. In your case, it could run from 800Hz.






    Here's an eBay ad for some JBL 2360 horns. Usually, you get to pay half that price. Also, 2445 compressors with original diaphragms are usually quite cheap at $200.00usd a pair.

    http://www.ebay.com/itm/JBL-LARGE-31...0AAOSwXeJYEq5n


  9. #24
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    I like that, but the problem is cost and space.

    The next time I go there which may be after Christmas I may see if I can test one of the Bullfrog cabinets and see how high in frequency it will go.

    If it will do 1.6KHz and sound good that will be good, but if not I will need a good 1.4" compression driver.

    Would this driver work?

    http://www.parts-express.com/eminenc...-bolt--290-566

    Maybe eventually as they get more money I can add this Yamaha amp to each speaker stack which will get me the digital crossover I need. It would be used for the 4520 cabinets.

    http://www.parts-express.com/yamaha-...ohms--247-6157

  10. #25
    Senior Member Lee in Montreal's Avatar
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    If you've noticed, this is a Lansing forum. We can hardly recommend a crappy eminence or Yamaha driver over a much better JBL 2240-41-45-50-51 compressor...

    BTW The Eminence's claim of 800-20KHz is perhaps far fetched too...

  11. #26
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    Will have to look up those drivers

    EDIT:

    Just looked up those drivers.

    Those are low frequency drivers at least that's what I saw when looking them up.


    Everything is all set. Talked to the owner's daughter today and her dad doesn't quite have the money right now to put into the sound system.

  12. #27
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    Quote Originally Posted by Lee in Montreal View Post
    If you've noticed, this is a Lansing forum. We can hardly recommend a crappy eminence or Yamaha driver over a much better JBL 2240-41-45-50-51 /snip/
    Considering Eminence is one of, if not the largest, oem manufacturer of speakers, they are a good alternative for a temporary solution if you are looking to properly restore the equipment with JBL or Altec components once the $$ is available. It's not that their components are "crappy"...it's an option Ive had to use in 9ne club here I've worked with for the last 25 years. I had to replace 6 15" speakers in some Martin 115 bins that were i itially loaded with JBL 2225. I wasn't about to get the owner to shell out for 6x 2226 speakers, and reloaded them with Eminence units suitable for horn loading, which performed well.

    Cerainly not up to what I would accept from JBL. But the alternative at the time was having 6 empty bins that couldn't be used.

    I understand the whole "not gonna recommend" because it's not JBL, but unfortunately, some of us arent made of $$ and have to look to alternatives. I'd love to have a full SRX800 series of foh stacks and stage monitors...but alas. Will have to make do with homebrew monitors loaded with E140 and eminence horns/drivers and non standard double 18 cabs that hopefully will work with the 2242 speakers I just scored on a few weeks ago.

  13. #28
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    Agreed.

    If it were for myself I'd get JBL drivers as I wouldn't abuse them.

    Given this is for a skating rink I hesitate to use the JBL drivers as I'm sure the system will be used and abused.

  14. #29
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by short_circutz2 View Post
    Considering Eminence is one of, if not the largest, oem manufacturer of speakers, they are a good alternative for a temporary solution if you are looking to properly restore the equipment with JBL or Altec components once the $$ is available. It's not that their components are "crappy"...it's an option Ive had to use in 9ne club here I've worked with for the last 25 years. I had to replace 6 15" speakers in some Martin 115 bins that were i itially loaded with JBL 2225. I wasn't about to get the owner to shell out for 6x 2226 speakers, and reloaded them with Eminence units suitable for horn loading, which performed well.

    Cerainly not up to what I would accept from JBL. But the alternative at the time was having 6 empty bins that couldn't be used.

    I understand the whole "not gonna recommend" because it's not JBL, but unfortunately, some of us arent made of $$ and have to look to alternatives. I'd love to have a full SRX800 series of foh stacks and stage monitors...but alas. Will have to make do with homebrew monitors loaded with E140 and eminence horns/drivers and non standard double 18 cabs that hopefully will work with the 2242 speakers I just scored on a few weeks ago.
    Crappy : What do you think of a company that claims 800-20khz from his driver when basically only TAD and their very pricey units can achieve this performance, or a JBL driver with expensive Berylium diaphragm. Reminds me of Radio Shack.

    Alternatives were given to buy used JBL drivers at equal (or lower) price. Per exemple JBL 2445 with their original Titanium diaphragms often sell locally for $200.00cad a pair (that's $150.00usd for TWO). Why would I pay more (each) for some Eminence drivers? i was not bashing him for using Eminence or any other brand. Just not recommending it after I showed there are better solutions.

    Lee

  15. #30
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    Given how big Eminence is especially with the OEM market I doubt they would claim their driver can do something it cannot do.


    Also if these were mine I would use JBL, but I cannot see risking JBL drivers in a situation where they can and probably will be abused.

    Sure the Yamaha amp I'm going to use has limiters, but with the passive crossover I'd be limiting the power to the bullfrog cabinets and unless the max power level the Bullfrogs need to fill the place with sound is less than the max power level the compression drivers can take, they can still be damaged.

    Now when the owner gets enough cash if there are four JBL drivers available I might look into getting them, but they will need to fit a 1.4" throat and play up to 16KHz.

    It's more about making the system as robust as I can while still sounding good.



    It's gonna be nice to have all this high quality sound with the 15" drivers barely moving

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