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Thread: Experiments with M2 horns.

  1. #1
    Senior Member Don C's Avatar
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    Experiments with M2 horns.

    I thought that this kind of fooling around should have it's own thread and not go into the M2 thread, as these cannot be called M2s.
    I mounted the 2452Hs to the horns and set them on top of my PS1400s. It surprised me how much they look like they belong there right off the bat. They look more at home than the PT800s ever did. The compression drivers are resting on an inch of styrofoam, itself resting on the same stand previously used for the PTs. The horns are upside down, so that they don't rock on the rounded part.
    My early impression is that they sound breathy, that is, I'm hearing the singer breathe on the mic more than I used to. I like that I can walk around and the sound doesn't change a lot. My listening chair is a little off center in the room, and I'm hearing more from the opposite speaker than I used to. They sound pretty neutral, not as big of a change from the PT800s as I expected. I have a lot of adjustment left to try though.
    The crossover is the same JBL SPP-AC1 that I have been using with the PT800. There are no filters left in the woofer cabinets. I Set the crossover frequency to 800, and they sound better to me with the phase invert on. I set the horn eq to 4K, just going by ear. I don't have any protection filter on the tweeters, so I have to be careful. I could live with this setup forever as it is, but those boxes sitting on the chair contain 1500FEs, for future use.
    I know that I'm not the only one here who bought these horns, and I want to see what you guys are doing with yours now.

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  2. #2
    Senior Member Don C's Avatar
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    My experience so far is that they sound wonderful on one CD and awful on the next. When they are good, they're very good. Larry Carltons Sapphire Blue CD sounds absolutely amazing. But I'm having some frustration getting the level matched between the horn and woofer. With no padding on the tweeter, the tweeters level control on the crossover is turned down to near it's minimum. Making a tiny rotaion to the level pot makes a huge diference to the sound. Fine adjustment is impossible. I'll get some resistors installed into the driver circuit and continue later this week.

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    Senior Member pos's Avatar
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    Hi Don

    Quote Originally Posted by Don C View Post
    My experience so far is that they sound wonderful on one CD and awful on the next.
    That is probably a hint that the EQ settings you are using do not give a flat response.

    FWIW, here is what it gets to make it flat with the D2 driver:
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  4. #4
    Senior Member Don C's Avatar
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    OK, saying they sounded awful was too much exaggeration. A Steven Wilson concert earlier this month has robbed me of some of my hearing and left me prone to listening fatigue. Tonight, Fleetwood Mac made them sound awesome again.

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    Senior Member ivica's Avatar
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    Quote Originally Posted by pos View Post
    Hi Don


    That is probably a hint that the EQ settings you are using do not give a flat response.

    FWIW, here is what it gets to make it flat with the D2 driver:
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    Hi,

    But with 2450H driver, EQ curve would be different, I would expect, especially if Ti-ribbed diaphragm is used, so only after some measurements more realistic EQ can be get, not to mention the bass-to-VHF driver sensitivities differences.

    regards
    ivica

  6. #6
    Senior Member pos's Avatar
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    Yes of course, but the horn would still require very specific EQs.
    The idea was just to stress the fact that this horn require more complicated EQ settings than say a PT waveguide (ie it is less smooth by nature).

  7. #7
    Senior Member Don C's Avatar
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    I haven't told the full story about the drivers and diaphragms here, it involves me screwing up. When I saw the horns at Speaker Exchange, I also saw the drivers, 2452H, and brand new at better than half off, looking like a bargain. I suspected that I really wanted 2451s, but looking around, none were for sale, at least not at prices that I wanted to pay. So I got the 2452s. Right after the 2452s were delivered some used 2451s showed up on ebay, pretty cheap. (2451SL-16) I debated with myself for a while and then ended up buying those too.
    When I got the adapter plates I knew that they would need to be modified to take both styles of driver. After imposing upon a friend who spent 45 minutes setting up a fixture to mill out the slots, this was done. We set a bit to just kiss the inside diameter of the original holes, then moved it out from center .375, making the slots long enough for a four inch circle. I was sure this was correct. I was wrong. The 2451s need a 4.5 circle, and I'm a bonehead.
    So more work is needed but it has to wait.
    What I did do, was this. After I listened to the uncoated 8 ohm ti diaphragms for a few hours, I removed them and borrowed the -SL diaphragms from the 51s. They fit right into the 2452s. You just have to move the terminal posts from the old diaphragms to the new ones. These are a big improvement, immediately it was obvious that something had changed for the better. I thought that I would be adjusting the levels up by 3db, to compensate for the impedance change, instead I ended up with 5db more, and they are less harsh even at that level. I'm still fooling with the settings too much though. I set the horn comp down to to 3Khz and have played with the levels endlessly. One CD seems to have too much treble, the next not enough. It's probably a sign that the horn levels are correct and my music selection is the problem. I also have some Truextent diaphragms that 4313B sold me. But I'm not going to install those until I get the resistor network straightened out. And those slots elongated more. And then I'll probably put them into the 2451s.

  8. #8
    Senior Member Don C's Avatar
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    I may put this Rane equalizer into the system. I'd like to avoid it due to added noise.

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  9. #9
    Senior Member ivica's Avatar
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    M2 resp with 2451/52 Be Trex

    Quote Originally Posted by Don C View Post
    I haven't told the full story about the drivers and diaphragms here, it involves me screwing up. When I saw the horns at Speaker Exchange, I also saw the drivers, 2452H, and brand new at better than half off, looking like a bargain. I suspected that I really wanted 2451s, but looking around, none were for sale, at least not at prices that I wanted to pay. So I got the 2452s. Right after the 2452s were delivered some used 2451s showed up on ebay, prety cheap. (2451SL-16) I debated with myself for a while and then ended up buying those too.
    When I got the adapter plates I knew that they would need to be modified to take both styles of driver. After imposing upon a friend who spent 45 minutes setting up a fixture to mill out the slots, this was done. We set a bit to just kiss the inside diameter of the original holes, then moved it out from center .375, making the slots long enough for a four inch circle. I was sure this was correct. I was wrong. The 2451s need a 4.5 circle, and I'm a bonehead.
    So more work is needed but it has to wait.
    What I did do, was this. After I listened to the uncoated 8 ohm ti diaphragms for a few hours, I removed them and borrowed the -SL diaphragms from the 51s. They fit right into the 2452s. You just have to move the terminal posts from the old diaphragms to the new ones. These are a big improvement, immediately it was obvious that something had changed for the better. I thought that I would be adjusting the levels up by 3db, to compensate for the impedance change, instead I ended up with 5db more, and they are less harsh even at that level. I'm still fooling with the settings too much though. I set the horn comp down to to 3Khz and have played with the levels endlessly. It's probably a sign that the horn levels are correct and my music selection is the problem. I also have some Truextent diaphragms that 4313B sold me. But I'm not going to install those until I get the resistor network straightened out. And those slots elongated more. And then I'll probably put them into the 2451s.
    Hi,

    In such large number of JBL 4-inch drivers 245x, may be a good staring point can be the measurements data that our forum member sebackman
    ( http://www.audioheritage.org/vbullet...?600-sebackman ) has shown to us:

    http://www.audioheritage.org/vbullet...l=1#post373896
    http://www.audioheritage.org/vbullet...l=1#post375970

    regards
    ivica

  10. #10
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Don C View Post
    One CD seems to have too much treble, the next not enough. It's probably a sign that the horn levels are correct and my music selection is the problem.
    I would agree with pos. I doubt the problem is with the music or the recordings. I bet fine tuning of your EQ is needed. I also doubt you can get there with a graphic EQ. You may want to explore DSP options and good acoustic measurement software.

    You've got a great start with these horns and drivers... with further exploration you'll really have something.


    Widget

  11. #11
    Senior Member Don C's Avatar
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    I've been in a somewhat similar situation before. More than once. When the amp in these PS1400s went up in smoke, () I added these AC1 crossovers and the Lexicon amps, and started tweaking. It was weeks before I learned to leave the level controls alone and enjoy the sound they were giving me. If you are thouroughly familiar with a system, and then you put on a disc and hear too much bass, you think it's the recording engineer's fault. Right after making a big change to the system, you hear the same change, and think it's you own setup that's wrong. I'm definitely dealing with some of the same thing right now, just on the treble instead of the bass. And I need to mention also that I've had a lot of great sound already from these, when they are good, they're really, really good. I'd never discourage anyone from trying them out.

  12. #12
    Senior Member Don C's Avatar
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    Here's a surprise, you can still buy useful parts from Radio Shack, like this 8 ohm 20 watt resistor. Parts express only had 10 watt for some reason.
    It's probably just my imagination that the speakers sound better today with the pad in place, but that's what I think. The pad is only 6db, so the tweeters are still a few db louder than the woofers. It's nice to make a small level change and only hear a small level change, because the controls are close to the middle of their range now.
    And the horns still look good sitting there, I'm constantly admiring the design, upside down or not.

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  13. #13
    Senior Member Don C's Avatar
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    I've obtained a measurement microphone and set up the REW software to get a visual of what I'm listening to. This is how I had it set up by ear using the few controls available on the crossover and sub equalizer. It seems that I like a lot of bass. I'm looking at some of those fancy DSP crossover/equalizers for the next step. I have quite a way to go on just getting these measurements done right for now. This is just one sweep, smoothed. I'm working on making sweeps with different mic locations and averaging them next. But I had suspected that things that I heard that I didn't like were more of a problem with the woofer than with the tweeters, and this sort of confirms that.

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  14. #14
    Senior Member Don C's Avatar
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    I'll soon be adding a BSS Blu-160 to the system. Bought used from eBay, it was less cost than just buying the interconnect kit from JBL. I'll be using regular XLR cables and regular Phoenix connectors to hook everything up, projected cost less than 50.00
    I obviously have a steep learning curve ahead of me.

  15. #15
    Senior Member Lee in Montreal's Avatar
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    If I remember well, the M2 heavily uses DSPs, so I am not surprised that using an M2 horn might require some time to properly eq it. Then, when it'll look good on a plot, perhaps it will require more time to sound good ;-) I think it would be the ideal set-up for two amps and a digital crossover...

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