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Thread: Choosing a Mid-range that Fits.

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    Choosing a Mid-range that Fits.

    Hey all, apologies if the wrong sub forum, but am looking to figure out what kind of mids to incorporate into my system. I run active setup with a DBX Driverack 260.

    The bass will be a JBL2245, and the HF unit for now is a Celestion CDX1-1745 on a QSC clone guide. Not all JBL, no, but a starting point. I suppose the go to would be to flow the 4345 design principles?

    The usual 4345 crossing the 2245 over at 290hz (IIRC) seems to be quite common. My boxes for the 2245 are 8 cubic foot and was considering initially just using them as subs ala the B460. The internet is full of 2 way designs and the like, and folk like Zilch developed the the Econowave, which is very well documented. Choosing a design of finding inspiration for one is tough. Fortunately the HF section is documented elsewhere and isn't totally alien. The 2245 in 8cf is familiar enough, that I am not concerned about how they will perform. It's picking the mid to fill the hole that has be scratching my head.

    Assuming I want to keep it as JBL as possible, I have considered a range of drivers from 10-15" including the 2123h, 2251j, 2206h, 2225/6h and so on. It would seem if taking the 2245 to almost 300hz, the 2123h is a wise choice. Using a 1" HF unit now means I need to cross higher than say a 2445. The Celestion can be crossed low enough that a 12 isn't out of the question, and some designs like Pi4's from Parnham cross a 15" to a 1".

    The 15" is a lot less appealing with a 2245 in the mix. I don't know if I am looking to clone anything specific at this point. The 2251j is a 10" but usually found in quads and 16ohm. I realize they're not 2123h drop ins, but they are more current 10" offerings and a little more common. I don't think I want an MTM setup. Not sure how hifi folks employ (or if they do) the 2251j.

    Sourcing many of these drivers isn't as easy as it was a few years ago even. Naturally the 2206 and 2226 are a little more common finds given their age or lack of. I've considered alternative brands, but that pursuit led me to "we don't have any to send you, but we charged your card" and am getting fed up waiting on bad actors, and have a big hole in my setup.

    TLR - I am looking for a 10-15" driver to go between a 2245h and 1" driver. Not sure if I go with a higher XO 3 way or like a 2 way with a sub.

  2. #2
    Senior Member Eaulive's Avatar
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    If you can put your hand on a set of 2202s, I highly recommend them!
    I used 2119 and 2118 in the past and they were also sounding good, although they don't have as extended a range as the 2202 IMHO.
    My avatar: 4520 loaded with 2225H on E140 frames,
    1x 2202H on custom front loaded horn, 2x 2426 on 2370.

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    Thanks for the replies.

    As it stands, I need to make some cabinets to house the 2251J and am curious the volume you settled on. I see the JBL enclosure guide lists a 1.5cft enclosure for E120 midrange, but that sounds a bit large, especially given the 2251J doesn't need to be in an 80hz tuned enclosure. I suppose using the volume of the 4345 midrange cone would be closer to what I am needing?

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    I simply used an 8" wide x 3/4" thick "shelf" board and made a ~11.5" x 11.5" x ~8" deep box adding a face and back from (IIRC) MDF. I also have a rear port made from a PVC coupler, reemed out a bit, and lined the inside of the backs with felt cloth.





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    I listen every day to a pair of 2206's crossed over at 1100 hz into a pair of 2426s on 2344 horns and they sound fine. I use a single 2226 as a sub since the 2206s have no trouble working down to 90 hz. I've tested the same set up with a 2202H that I've had since the 80s and it sounds very slightly better near crossover but I have yet to find a match for it ( and may never ). I've got a pair of single 2226 boxes that I'll use as lows if I ever do find another 2202 and move my crossover from 90 hz up to 250 where I've found the best sounding combination to be. The lightweight, curved cone of the 2202 really does sound better than the heavy, stiff cone of the 2206 ( or any dedicated bass speaker ) as you get closer to 1 kHz but at then any twelve crossing over into a 1" compression driver is to my ears the most pleasant sounding home hifi combination. Much better sounding than the 15" into the same horn / driver combo. B&C makes some nice light coned 12" mid bass drivers if you can't find any old JBLs.

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    @Mortron

    A little bit of Reading for you

    Follow the other links found within that thread ( for some other opinions ).


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    I use 2251Js with 2241H and Heil AMT.

    I run these as a 2.5 way in that the 2251J has no high pass crossover cap but uses its natural roll off from 300 Hz down. When I did put a 30 mF cap in series, it did reduce the low end and volume a bit (which it really needs), but the really critical lowest frequencies only decreased by about 1-2 dB. I guess the impedience peaks in this area and as the impedience goes up, the effectiveness of the cap is essentially lost. Based on that premise, I felt it better to not run a cap and take advantage of the additional volume available as well as the better integration with the 2241. I cross them over to the Heil at ~1,800 Hz. This is just before the 2251s show an major increase in volume and the roll off takes this out.

    The 2251s were used in a horn enclosure and very few people have found how to correctly apply them to a home setting. There is a guy located outside of LA who has/had a shiite-load and was selling them on ebay for, IIRC, $130/pr. He even matched the pairs to get the dc resistances the same or at least withn 0.2 ohm. NOW HE SELLS THEM FOR 4/$150 AND STILL HAS A SHIITE LOAD!!! I mean..., come on, $37.50 each!!! That's probably about 10% of JBL retail!

    https://www.ebay.com/itm/25506166496...YAAOSwpYNg05ru

    BTW, if you want 2123Js, there is a beautiful pair in Bakersfield that are/were recently listed on C/L. No affiliation.

    https://bakersfield.craigslist.org/e...342516052.html




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    Quote Originally Posted by RMC View Post
    Hi mortron,

    Somewhat late to the party, but this might help you.

    The Enclosure Guide's 1.5 CF, Fb 80hz, is good for E120 as woofer in a two-way system for example (read the note at bottom of page 1 of Enclosure Guide, the E120 is not mentioned there, indirectly confirming my statement).

    As i understand it (since i'm late), your driver application would be to use E120 for low-mid. Checking the TS for the driver, Qts is very low at 0.17 which helps in reducing box size to house the driver.

    In such application driver is usually housed in a small closed sub-chamber. But the best way to know for sure which size box is to model the driver in speaker design software.

    According to Eargle's Loudspeaker Handbook the upper limit for a 12" is 875hz @ DI 6 db, and somewhat stretched is 1313 hz @ DI 10 db. So more directional (this being a musical instrument driver it most probably has a rising response that you may benefit from, with the inconvenience of having more directivity).You decide if proper

    Driver EBP is 315 in principle driver more suitable for horn, but not necessarily a no here. Regarding the Graphs:

    First assuming 2 Pi box placement, then second one with baffle diffraction loss (no 2Pi), somewhat better for low-mid (you're actual result may be somewhere in between)

    Standard QL 7, this can be increased to QL 10 due to small box size, if well made, higher QL means little smaller box can be used because of reduced losses, but at some point need to have enough volume to fit the driver in.

    1 or 1.5 cf response graphs i get from modeling are practically the same.

    At first sight, 1 cf sub-box seems feasible as per dimensions given to me by Winspeakerz software, with a little "cheating"/adjustments (H vs W vs D).

    I'll post my graphs and sub-box dimensions later tonight, gotta go now...

    Richard
    Richard,

    Thank you for such a thought out reply. I am not using an E120... apologies if there was confusion. I simply mentioned it as it was the smallest enclosure on the list and E120 would alloy one to find it in the list... Apologies. Or am I mistaken and your math is for a 10" like the 2251J? Regardless I feel I've learned something and appreciate it.


    Toddalllin, thanks for your pics. You mentioned a read port. Is a port essential to using the 2251j down to around 300hz??

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    Quote Originally Posted by mortron View Post
    Richard,

    Thank you for such a thought out reply. I am not using an E120... apologies if there was confusion. I simply mentioned it as it was the smallest enclosure on the list and E120 would alloy one to find it in the list... Apologies. Or am I mistaken and your math is for a 10" like the 2251J? Regardless I feel I've learned something and appreciate it.


    Toddalllin, thanks for your pics. You mentioned a read port. Is a port essential to using the 2251j down to around 300hz??
    Probably not. But I ran them open back, closed back, and with the port and preferred the sound with the port best. Recognze that Wilson "vents" their smaller drivers too.

    Because of the fins on the heatsink, it is necessary to mount the speakers the same way in both cabinets (i.e., the leads won't look symmetrical).

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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.

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    Senior Member Eaulive's Avatar
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    Quote Originally Posted by Riley Casey View Post
    B&C makes some nice light coned 12" mid bass drivers if you can't find any old JBLs.
    True! Before having the 2202s in my 4520 stack (avatar) I had B&C 12PE32 in them, very pleasing as well and very dynamic for mid-bass.
    My avatar: 4520 loaded with 2225H on E140 frames,
    1x 2202H on custom front loaded horn, 2x 2426 on 2370.

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    Quote Originally Posted by Eaulive View Post
    True! Before having the 2202s in my 4520 stack (avatar) I had B&C 12PE32 in them, very pleasing as well and very dynamic for mid-bass.
    I use the B&C 12PE32 in my double 12 mid hi boxes, a very clean dynamic light weight cone mid bass
    speaker and very efficient at 101db.

    My stage monitors are loaded with JBL 2262 and 2265 speakers.

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    I will have to take a look at them, but I presume you mean because the fins should run vertical?

    In regards to the different enclosure types used, how would you compare/contrast the closed, open and ported designs? Also, did you use the same enclosure for all those alignments?

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    Quote Originally Posted by mortron View Post
    I will have to take a look at them, but I presume you mean because the fins should run vertical?

    In regards to the different enclosure types used, how would you compare/contrast the closed, open and ported designs? Also, did you use the same enclosure for all those alignments?
    Yes, because the fins can either let the air flow through them on its way to the port, or the air has to flow around them on its way. The fins create "channels".

    Yes same cabinets. The open back was lacking "body" and there seems to be a touch more "openness" with the port open rather than closed.

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    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.

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