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Thread: Choosing a Mid-range that Fits.

  1. #31
    Senior Member Eaulive's Avatar
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    By the way, I listened to both versions, the original "Voodoo Child (Slight Return)" from the 1968 "Electric Ladyland" album and the SRV version from the 1984 "Couldn't Stand the Weather" album.
    The SRV version is cleaner, more adapted to plain vanilla audiences and casual listening with a much tamed guitar sound, the JH version is totally crazy, with flanging and L/R panning throughout, the guitar is more dirty, more in your face.

    I like both, but JH gets my vote.

    My apologies to the OP as well, this is a bonafide thread hijack
    My avatar: 4520 loaded with 2225H on E140 frames,
    1x 2202H on custom front loaded horn, 2x 2426 on 2370.

  2. #32
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    Quote Originally Posted by Eaulive View Post
    By the way, I listened to both versions, the original "Voodoo Child (Slight Return)" from the 1968 "Electric Ladyland" album and the SRV version from the 1984 "Couldn't Stand the Weather" album.
    The SRV version is cleaner, more adapted to plain vanilla audiences and casual listening with a much tamed guitar sound, the JH version is totally crazy, with flanging and L/R panning throughout, the guitar is more dirty, more in your face.

    I like both, but JH gets my vote.

    My apologies to the OP as well, this is a bonafide thread hijack

    And I just finished listening to the JH version. My SRV disk is SACD. It is cleaner (revealing a cleaner recording), the transients are much "snappier," and the soundstage and imaging are better. JH Strat is more laid back than SRVs, but that could be the difference in the recording process/chain. I actually prefer the SRV version. JH gets a bit carried away.

  3. #33
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    @mortron,

    Here's a comparison of JBL's 3, main 10" mid-rangers most commonly used in projects.

    These are traces made from JBL's official EDS documents ( found in the Transducer section of this very website ).

    Name:  JBL 2122h, 2123h, 2251j response.jpg
Views: 329
Size:  104.8 KB

    To these eyes, the 2123h is the smoothest within the usual ( useful ) passband area of 200hz - 2Khz ( followed by the 2251j and then the 2122h ) .

    Conveniently enough ( for the project designer ) all 3 perform very well with the ( Giskard modified ) 4344/4345 network ( the 8 ohm variable Lpad has the effect of moderating the impedance differences ) .

    Here's an Xsim prediction for these same 3 midrangers filtered with the 4345 midrange filter ( balanced//adjusted for output using the variable Lpad of that filter )

    Name:  JBL 2122h, 2123h, 2251j response with 4345 midfilter .jpg
Views: 393
Size:  91.5 KB

    I had to use "traced" impedance files ( which is only so good since they weren't made with these drivers located in the stock .5 cu' enclosures > which shifts the impedance peak upwards ).


  4. #34
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    Interesting.

    Note that in this application, the 2251J is the smoothest.


    What the graphs don't show is performance beyond frequency response. While the 2251J is a bit less sensitive, it will handle the most power in compensation (400 watt rating). It also uses a differential drive system that in theory/literature should produce the best transient response and lowest distortion.

    Then when you look at the outrageously LOW price for 2251Js, it becomes a no brainer. This is the same guy I got my set from so many years ago, and he still has a boatload to get rid of. His prices have actually dropped by about half of what I paid (IIRC $130/pr), but his shipping has gone up. (though he only shipped two pieces to me and is shipping four pieces here). If you don't like the set shown, he has others.

    https://www.ebay.com/itm/255097366660?hash=item3b64fce884:g:850AAOSww09g05c 6


    In actuality, the 2251J is a bit low in sensitivity compared to the 2241H, and a pair used in MTM fashion could be just the ticket. Remember that the 2251J was designed to be horn-loaded and all of its JBL published sensitivity ratings are based on it being horn-mounted. I put a resistor in parallel with the 2241H to reduce its sensitivity, but crossover-frequency wise, it would be better not to have the resistor. A second 2251 could take care of this and probably reinforce its low end a bit more. And at those prices, one could certainly afford to do so. Mine have worked as new and still do.

  5. #35
    Senior Member RMC's Avatar
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    Todd,

    RE "I put a resistor in parallel with the 2241H to reduce its sensitivity," (post # 34)

    What type, power rating and resistor value do you use for that purpose? Any inconveniences noted on driver performance/sound? Thanks.

  6. #36
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    I use a 50 watt Dale resistor (~20-30 ohms but currently ~27 ohms). 20 ohms seems a bit too little for the 2241 (makes it a bit bass light) and 30 ohms is a bit too much (a bit bass heavy).

    But this would not be necessary if using a 2245 because it is not as loud/efficient as a 2241 and should be just about perfect. Also note that I don't run a high pass cap on the 2251J. (I actually run these as a 2.5 way.) I found that it just reduces the volume a bit and really does nothing to change the slope or attenuate the very low bass (maybe 2 dB). And why put the signal through more components if unnecessary?

    This would be interesting to model.


  7. #37
    Senior Member RMC's Avatar
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    Todd,

    Thanks for the reply. Not drawing any conclusions about resistor on woofer, just curious that i may be missing something or not. You're the second member i see recently using a resistor on woofer, not usual, however the other fellow used his in series. I've used occasionally low value resistor in series with mids and tweeters but never on woofer, series or parallel. Hence my curiosity.

    One case i did was a small 4 parallel speakers system driven by a small receiver in a small room. Not really enough juice for series connections, also couldn't cope with the less than 4 ohms of the 4 boxes in parallel. One pair acting as rear channels having lower impedance than the other but also higher sensitivity. So that one got a series resistor increasing its impedance and by the same token reducing its sensitivity. This after some calculations and resistors testing. The outcome is good, levels are where i want them, receiver never complained about load seen.

    In your case since its to reduce sensitivity also any particular reason why not a smaller value resistor but in series instead of higher value in parallel? Power capacity, damping factor, back EMF, whatever?

    Btw, you mentioned previously here about box size for the 2251J. With its pretty low Vas and Qts numbers no wonder you were able to use such small box. EBP 277 nice for horn loading too (HLA 4895).

    RE And why put the signal through more components if unnecessary?

    I can't disagree with that. I've mentioned before i'm of the opinion that when a driver in a system needs a whole lot of adjustments or corrections in the crossover, then it may be the wrong driver to begin with... therefore look elsewhere for a more natural performer in view of application.

  8. #38
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    A low value resistor in series with the woofer is sometimes done and people equate this with a "tube" sound (BTDT). But it has an impact on how the woofer responds in that it hurts the damping, which is why it is often equated with tube sound. Tube amps typically have a relatively low damping factor compared to solid state.

    BTW, if you look at JBL crossover schematics, you will find that dozens use/used a resistor in parallel with the woofer, whereas I can't remember any where it is placed in series. Whether it be to reduce the volume to the woofer or modify the crossover slope, I guess would depend on the selected drivers, their efficiency, their characteristics, and the preferred slopes.

    I have an A/B/X switch box, and too match two sets of speakers, I can attenuate the signal at the line level, at the speaker level (using 100-watt L-pads), neither, or both. When I use the L-pads, the bass is notably "mushier" most probably because the difference in damping.

  9. #39
    Senior Member RMC's Avatar
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    Todd,

    Thanks for the interesting explanation.

    I design mostly around a woofer i want to use, not always though, and choose the other driver(s) accordingly. Since i never had to pad a woofer never did, plus in my head its kind of against nature. So I find a work around or use another driver.

    For a mid that has little lower sensitivity than ideal, or a small dip in response, this isn't a major problem considering the Fletcher Munson equal loudness contour curve. The ear is already more sensitive to mid frequencies than to others, so upon listening the subjective impression isn't much compromised.

    This goes along your: "why put the signal through more components if unnecessary?"

  10. #40
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    Quote Originally Posted by Earl K View Post
    @mortron,

    Here's a comparison of JBL's 3, main 10" mid-rangers most commonly used in projects.

    These are traces made from JBL's official EDS documents ( found in the Transducer section of this very website ).

    Name:  JBL 2122h, 2123h, 2251j response.jpg
Views: 329
Size:  104.8 KB

    To these eyes, the 2123h is the smoothest within the usual ( useful ) passband area of 200hz - 2Khz ( followed by the 2251j and then the 2122h ) .

    Conveniently enough ( for the project designer ) all 3 perform very well with the ( Giskard modified ) 4344/4345 network ( the 8 ohm variable Lpad has the effect of moderating the impedance differences ) .

    Here's an Xsim prediction for these same 3 midrangers filtered with the 4345 midrange filter ( balanced//adjusted for output using the variable Lpad of that filter )

    Name:  JBL 2122h, 2123h, 2251j response with 4345 midfilter .jpg
Views: 393
Size:  91.5 KB

    I had to use "traced" impedance files ( which is only so good since they weren't made with these drivers located in the stock .5 cu' enclosures > which shifts the impedance peak upwards ).

    EarlK, Thank you for this post, I feel it answered a few questions I didn't know I had. I presume the L-Pad is what helps match the 8ohm drivers to the 16ohm driver? I must admit to being a bit naive about L-Pads. I will do some googling. As for the crossover in the Giskard Network, is that the filter to pursue if one of us are looking at a 2245/2251 pairing?

    ----

    Toddalin, in your use of the 2251J, had you tried it on a wider baffle? If so, how would you compare them? Am still wrestling with a setup like yours or a large baffle speaker. If you did it over again, would you still go same route?

  11. #41
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    Quote Originally Posted by mortron View Post
    EarlK, Thank you for this post, I feel it answered a few questions I didn't know I had. I presume the L-Pad is what helps match the 8ohm drivers to the 16ohm driver? I must admit to being a bit naive about L-Pads. I will do some googling. As for the crossover in the Giskard Network, is that the filter to pursue if one of us are looking at a 2245/2251 pairing?

    You can use that N3145 filter ( for the 2245 and 2251j ) as long as the 18" and 10" are tight packed ( iow; closely oriented to each other like in the 4345 ) .

    If your intention is to build a two box system, then going the route that Todd went makes more sense ( the port in a slightly larger box > such as .75cu' - 1cu' < tuned high > such as maybe 120 hz > should be able to give a bit more usable LF to the response of the 2251j ). This might allow a lower crossover point ( which becomes an advantage as you move the two boxes further and further apart )

    Play around with some different tunings ( with various box sizes ) within winISD until you find a reasonable LF response for the 2251j.

    Post your results here.


  12. #42
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    Quote Originally Posted by Earl K View Post
    You can use that N3145 filter ( for the 2245 and 2251j ) as long as the 18" and 10" are tight packed ( iow; closely oriented to each other like in the 4345 ) .

    If your intention is to build a two box system, then going the route that Todd went makes more sense ( the port in a slightly larger box > such as .75cu' - 1cu' < tuned high > such as maybe 120 hz > should be able to give a bit more usable LF to the response of the 2251j ). This might allow a lower crossover point ( which becomes an advantage as you move the two boxes further and further apart )

    Play around with some different tunings ( with various box sizes ) within winISD until you find a reasonable LF response for the 2251j.

    Post your results here.

    Imma do that for sure.... As soon as I hook my desktop back up (painted the 'office' recently) as my Dual Core Celeron Laptop with 4gb of ram, has enough trouble with loading a webpage... Or Windows login screen... That Winisd is probably even too much for it to manage. Windows 10 is like the loudness wars for computers. How big of a boat anchor can they make???

    I'm guessing the smoothness of response would be affected by transitions in the two different box sizes and those would need to be measured, or can it also be simmed in another program?

  13. #43
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    This is why I run them as a 2.5 way. Look at that nice low end roll off. There is also an impedience peak at the very low end. When a cap is used in series with the 2251, it does little to protect the driver down in this range because the impedience is so high. The higher the impedience, the less effective the cap. My cabinet may be a bit small because I have a bit more low end roll off than shown, but that probably provides more protection for the 2251. But it could just as easily be the room because the 2241 also shows a substantial dip ~200 Hz.


  14. #44
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    Sorry folks... Got called away for an inspection gig... Not ignoring the wicked contributions from y'all. Be back soon!

  15. #45
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    I decided that I was loosing a bit too much in the ~200-300 Hz range, so I changed the parallel resistor on the 18" from 26.8 to 36.8 ohms, changed the inductor from 8 to 5 mH, and reduced its cap from 89 to 59 mfd. This lets the 18" play a bit higher into this range adding about 2 dB in the depression. The resistor reduces the overall volume from the 2241 by ~1 dB. Without the resistor, the bass is a bit overpowering reducing intelligibility.

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