Brainstorming 3-way design with simple crossovers

Discussion in 'DIY' started by OJneg, Jan 28, 2019.

  1. OJneg

    OJneg The Most Insufferable

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    Currently have the Titan 615LX. Something that is cool about the speaker is that I could potentially swap out mid-tweeter units for something else. I have never actually built a design with 1st order crossovers, so this got me thinking.

    I am imagining the 15" woofer to be crossed at around 100Hz to an 8" widebander (lotta choices here). I would then use my Hawthorne AMT700's to hand off from the widebanders. Might still have to use some impedance correction on the mid to make a smooth transition, which I can live with. The AMT700 is meant to be crossed at 700Hz with a 2nd-order filter, and has decent power handling so I won't esplode it. Would still need to sort out the optimal crossover point for those two.

    This would all be mounted on a double-thick OB panel that would stand on the big woofer cabinet. The goal is high efficiency woofer in a big box mated with dipole mid AND dipole tweeter on the OB panel. Thoughts?
     
  2. purr1n

    purr1n Finding his inner redneck

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    Cross over the mid higher ~350Hz. An OB mid will start dropping around 350Hz with a 24" baffle. You don't want an OB mid to work that hard with unnecessary excursion that produces no sound. If you are using a mid, can probably crossover the AMT700 higher using 1st order.
     
  3. Serious

    Serious Inquisitive Frequency Response Plot

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    I guess you don't mean first order between woofer and mid at 100Hz.
    I'm not sure you can go first order from 8" widebanders to the AMT700, either. Shouldn't be a problem to recess the driver by 5-10cm relative to the mid, but beaming is probably going to be an issue and I highly doubt the AMT700 will have the necessary extension. With my 360Hz first order XO the woofer has to go to 2kHz and the mid to 40Hz reasonably well to get decent FR in the 100-1kHz range.

    What is the point here? Simple crossover or first order? I imagine 2nd order would be much simpler.

    Widebanders with whizzer cones are probably not going to work. The whizzer cone adds 60° of phase shift where it hands over to the big cone around 3-4kHz, at least with my Voxativs. Has to be tested. FR might become messy.
     
    Last edited: Jan 28, 2019
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  4. OJneg

    OJneg The Most Insufferable

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    Might need to do a second order on the mid then. The woofer already has a second order (IIRC) at 350 so that would lessen work for me

    I did. I don't know where the woofer breaks up, but probably between 1k-2k. First order filter gives me 20dB per decade, so it would depend on what the impedance curve is doing how much out of band energy its shooting out. Marvs insight about the smaller baffle acting against the mid would be the bigger issue.

    Extension where? As I said, it can run to -6dB @ 700Hz, so that means it has to be able to handle LF energy that your average tweeter would not. There is the issue of its HF extension. Doesn't quite get to 20k like some horns. Potential to augment with $500 super tweeters? :drunk:
     
  5. OJneg

    OJneg The Most Insufferable

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    Need to run simulation on what is the lowest Fc that I can safely run the AMT700 at. Not a lot of information out there and I think the Hawlthorne went radio silent

    @purr1n you ever use the Tang Band stuff?
     
    Last edited: Jan 29, 2019
  6. Serious

    Serious Inquisitive Frequency Response Plot

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    700Hz at -6db could mean crossover frequency around 2-3kHz at which point you'd need a pretty small mid. You could get it lower than that, but since it probably rolls off 2nd order + 1st order OB rolloff around there I'm not sure how low you can realistically take the mid-tweeter crossover.
     
  7. purr1n

    purr1n Finding his inner redneck

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    Never used them myself, but Craig had a few models in his lab. They are well behaved and do sound good, the downside is they are not super high-efficiency which means they will not work well with flea power SET amps.

    Isn't Hawthorne dead? Might be best to measure them with a protection cap and see what freq / SPL the distortion starts to rise. I don't totally trust what I've read on the audio-circy-jerky sites: supposedly it does down to 500Hz with steep active xovers, but I don't buy this because a steep knee filter at 500Hz may result in just as much excursion as a soft knee filter at 1000Hz.
     

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