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Thread: Looking For More Punch From My 2245, 4345 Clone

  1. #46
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    Quote Originally Posted by Ian Mackenzie View Post
    Here are some guidelines for matching the crossover characteristics to jbl systems using your drivers in a 4 way monitor.

    These characteristics are set for the driver locations on the baffle and the amplitude and phase characteristics of the drivers. The guidelines refer to the voltage drives not the amplitude response.

    Use the Crossover Butter-worth filter characteristics
    Woofer low pass
    2nd Order Butter-worth 260 hertz


    Mid 2123
    Low pass 2nd order Butterworth 360 hertz
    High pass 3rd order Butterworth 1,100 hertz
    Wire the mid electrically out of phase.

    I tried this and I like it so far. I had to turn down the 2245's amp slightly. I think I will have a bit of time in the next few weeks to play with this. I left the woofer high pass in there for now.

  2. #47
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    Quote Originally Posted by robertg View Post
    So underlapping crossover frequencies would mean kind of leaving a hole between frequencies? Instead of using 300 hz use 290 and 310?

    It doesn't leave a hole so to speak.

    For example a standard 24 db per octave filter cutoff crossover at 300hz at 450hz the signal is attenuated 12db, at 600hz it is down 24db (one octave) at 1200hz it would be down 48db. The same attenuation scale work on both sides of the cutoff frequency.
    There is area where both the low and the mid drivers are putting out an overlap of frequencies, using steeper cutoff rate filters will help minimize that, I use 48db on my sound systems.

    Where it gets interesting is in what they call the acoustic crossover frequency that can be different from the electrical DSP crossover frequency.
    In the case of crossing over from lows to mids or from any band pass to the next is when you run the band passes at different level as in more lows than mids raising the low output level increased the low drivers frequencies that are over lapping into the mid range area.

    Excuse my crude drawing!

    The middle vertical black line represents your intended crossover frequency.

    The green line is your mid range crossover output level and cut off slope.

    The red line to the left of the green line is the low frequency output level and cutoff slope.

    Both at the same level the crossover frequency both electronic and acoustic is the same.
    Now look at the upper red line that represents a higher low frequency output level and low pass cutoff frequency that is still set at the same high pass frequency as the mid range.

    You can see that it moved the acoustic crossover frequency higher with more overlap between the lows and the mids.

    The dashed blue line represents the same higher low frequency output level only with a
    lower low pass frequency and the resulting acoustic crossover now matches what the intended electronic crossover frequency was to be.

    You can listen by ear and play with the under lapping frequency, it is better to use a analyzer program so you can see the frequency response and phase response as you make adjustments.
    With your DSP you can also correct for driver offset delay.
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  3. #48
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    Mike I understand it by the way you explained it.

    I did some measurements today with REW. I put the microphone in five different places. That program is a little too advanced for me, but I can understand the basics anyway.

    Everything looks normal to me, I am using 1/6 smoothing.

    I'm going to raise my speakers about six inches next. I'm still looking for a decent looking way to do it.
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  4. #49
    Senior Member Ian Mackenzie's Avatar
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    Get a trolly board with heavy duty casters.

  5. #50
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    Thatís probably what I will do. Iím looking for a nice piece of butcher block to mount wheels to.

  6. #51
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    Grizzly makes butcher block workbench tops in several sizes.

    https://www.grizzly.com/search?q=(categoryid:360100)

  7. #52
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    Quote Originally Posted by JeffW View Post
    Grizzly makes butcher block workbench tops in several sizes.

    https://www.grizzly.com/search?q=(categoryid:360100)
    I have no problem finding butcher block, I just want some for really cheap. Usually counter top manufacturers have some cut-offs, or maybe I can find a couple of used restaurant for a good price. If not I will make something myself. I just don't really want to go to a retail store these days and buy some lumber and wheels.

  8. #53
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    I made some changes to these lately. The mids are now 2450s, one has a 2451SL diaphragm and the other doesn't. I can't seem to find another 16 ohm SL diaphragm, and I can't hear the difference anyway. I bought a pair of 2403 tweeters and had some NOS diaphragms for them. I built a pair of stands with rollers, way easier to move around now. I also built a pair of crossovers, now I only run two amps. Running a four channel or 4 amps was a real pain.

    I still want to buy a Bryston 10B crossover and a small Class A amp for the top end. I'm using a $100.00 Ramsa WP-9055 for now, but should really try something else. There doesn't seem to be much for sale right now.

    Every change seems to make a little improvement in sound quality. Or at least I think it did.
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  9. #54
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    Looks great Rob.

    Name:  413B86F1-0742-4D23-B283-491A40A244D9.jpg
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    Nice Blue, plus I love the look of the painted port-internals.

    Also the L94 lense is a nice touch .


  10. #55
    Senior Member grumpy's Avatar
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    Looks great!

  11. #56
    Senior Member Ian Mackenzie's Avatar
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    Very nice!

  12. #57
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    Thanks, hopefully this will be the last pair of speakers that I build. I'll post again when I change the amp. I am looking to buy a small Bedini, or some other Class A. They are difficult to find in Canada.

  13. #58
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by robertg View Post
    I'm going to raise my speakers about six inches next. I'm still looking for a decent looking way to do it.
    Looks like you found a great way to do it.

    Nicely done all the way round. Good luck on the Bedini. If you find one, it should be serviced due to age, but they are out there and they are very nice amps.


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  14. #59
    Senior Member BMWCCA's Avatar
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    Quote Originally Posted by robertg View Post
    Thanks, hopefully this will be the last pair of speakers that I build. I'll post again when I change the amp. I am looking to buy a small Bedini, or some other Class A. They are difficult to find in Canada.
    I seem to recall Greg suggesting a Crown D45 for this application at some point, if I remember correctly. Anyway, I started buying and stashing them some time ago. Cheap. Cute. Durable.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."óGreg Timbers

  15. #60
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    Quote Originally Posted by BMWCCA View Post
    I seem to recall Greg suggesting a Crown D45 for this application at some point, if I remember correctly. Anyway, I started buying and stashing them some time ago. Cheap. Cute. Durable.
    I bought quite a few D45s and D75s off eBay a couple of years ago. Every one had a big turn off thump that I didn't like. I remember they all had burnt resistors also. I ended up upgrading from my $60.00 Crown to $100.00 Ramsa WP-9055s. I have four of them now. I can't say anything bad about the Ramsa amps, I just want to upgrade a bit. Or maybe spend more money.

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