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Thread: How Low Should One Take the Lower Midrange Driver if Given a Choice???

  1. #1
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    How Low Should One Take the Lower Midrange Driver if Given a Choice???

    I intend to use a 2241H 18" woofer crossing over to a 2251J (~9-3/4") woofer.

    Through much experimentation, I found that I can get the 2251J "flat" down to ~110Hz. This would then put almost the entirety of the vocal range (begins at ~80Hz), and the first one - two sets of overtones all in the 2251J.

    The resonant frequency of the 2251J is 61 Hz and it is mounted in ~0.4 cu ft and ported on the rear with 1-1/2" ID x 2.75" length of PVC.

    So, what are the potential consequences of running the 2251J this low in a home setting?

    Thanks

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    I like the idea of keeping the bottom of the vocal-range in the midcone!
    Actually I was thinking of such a setup as well in the past.

    But it is a very uncommon way to run a ported mid-woofer above a ported low-woofer...
    There must be a reason why you donīt see this kind of setup with oem-speakers.
    Basically all of them use a closed box for the mids.
    That would give you a cleaner transient response for shure. But you wouldnīt even closly reach to 110hz without the porting..

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    I can see where it would be much more difficult to port the lower mid if it is mounted in the same box as the woofer.

    The lower mid box is only slightly larger than the driver making it difficult to fit the port to the front, and the port is too short to run it out the back of the speaker or bend it to the front baffle from an internal side.

    Actually, it looks like Wilson Audio ports their mids to the rear.


  4. #4
    Senior Member gdmoore28's Avatar
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    Hi Todd,

    I think it's a great choice to keep the mid range operating that low, especially when it's responding the way you say - and especially in a home environment.

    And I suspect that if manufacturers of pro gear knew without doubt that their gear would be used only in the home, they might do the same. But most of us here are using ProSound gear in an environment for which they were not primarily designed. I'm thinking (and thinking is a bad thing for me to do, 'cause that's typically where I get into trouble) that JBL and other manufacturers have durability under the worst of conditions as one of their primary design criteria - ie, keeping their drivers operating in frequency bands that optimize performance while minimizing stress. Keeping the lower frequencies out of the mid driver certainly accomplishes that goal.

    But producing the mid and low-mid frequencies through a single driver offers too many advantages to undertake here. You are on the right path.

    (I've often wondered what it must be like to manufacture a product and sell it to who-knows-who, understanding that the majority of their customers likely have no idea of proper operations protocol, and then additionally offering to warranty that gear. No wonder they insist on such unheard of profits!)

    All of that blather just to encourage you and to urge you onward. I'm following your build, and this takes it in a very interesting direction.

    GeeDeeEmm

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    Senior Member DavidF's Avatar
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    Quote Originally Posted by toddalin View Post
    I intend to use a 2241H 18" woofer crossing over to a 2251J (~9-3/4") woofer.

    Through much experimentation, I found that I can get the 2251J "flat" down to ~110Hz. This would then put almost the entirety of the vocal range (begins at ~80Hz), and the first one - two sets of overtones all in the 2251J.

    The resonant frequency of the 2251J is 61 Hz and it is mounted in ~0.4 cu ft and ported on the rear with 1-1/2" ID x 2.75" length of PVC.

    So, what are the potential consequences of running the 2251J this low in a home setting?

    Thanks
    A couple of things come to mind. First, what is the excursion range of the 2251J and how does the response an octave below fit within that range? You will have quite a bit energy passed with higher slope xovers as you get in the actual bass range.

    The other is that passive xover values get really significant at these frequencies. Maybe you were already thinking active xover but that should be a consideration.
    David F
    San Jose

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    Ported Midrange

    The Electro Voice S15-3 had a ported midrange and sounded good.
    Ruediger

  7. #7
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    Quote Originally Posted by DavidF View Post
    A couple of things come to mind. First, what is the excursion range of the 2251J and how does the response an octave below fit within that range? You will have quite a bit energy passed with higher slope xovers as you get in the actual bass range.

    The other is that passive xover values get really significant at these frequencies. Maybe you were already thinking active xover but that should be a consideration.
    Active crossover is not/no longer a consideration.

    Excursion is high for a ~10" with a double rolled edge @ 5.7mm. That's more than some foam edge 15s" (e.g., 2231H @ 5.08mm) or even rolled edge 18s" (2240 @ 5.59 mm). Resonant frequency is 61 Hz, so I'm still almost an octave above that. And the 10" goes to over 8kHz, so I cross over to the Heil at less than half of that.

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