JBL 2123
I continue to follow this thread with interest, and had actually been very intrigued by the 18 Sound 6ND midrange (x-o around 300HZ). I couldn't find any 2123's listed for sale. Now Magnetar says they are easy to find! Please tell me where/how, I'd love to get some!
Thank you,
Bill
I continue to follow this thread with interest, and had actually been very intrigued by the 18 Sound 6ND midrange (x-o around 300HZ). I couldn't find any 2123's listed for sale. Now Magnetar says they are easy to find! Please tell me where/how, I'd love to get some!
Thank you,
Bill
Re: JBL 2123
I have 16 ohm and 8 ohm pairs. email me if you want a pair - they pop up if you know where to look. I've been building home system with good pro drivers for years and have my sources in place on used stuff. There are a lot of them out there but they aren't cheap. the 16 ohm sound better, especially with a couple of coats of violin varnish.
Bill Brown said:
I have 16 ohm and 8 ohm pairs. email me if you want a pair - they pop up if you know where to look. I've been building home system with good pro drivers for years and have my sources in place on used stuff. There are a lot of them out there but they aren't cheap. the 16 ohm sound better, especially with a couple of coats of violin varnish.
Lynn ... Now you're talking. Something to look at.
Why not a 12" dipole waveguide for mids? Not a simple conical slab sides thing, but a true WG.
Rough estimates: 120 deg dispersion angle. 4" deep, about 9-10" total depth front to rear.
Mounted in a Sonotube it can look cool and would hide all the crap on the outside of horn to assemble and dampen, foam fill, etc.
Better pattern control and coupling rather than just letting the 6" blast away into low impedance air.
Mouth 20" diameter which is a little big but thought a little larger than normal would help smooth things out a bit and allow for a large flange radius. A 4" bell radius keeps the flare to mouth area ratio around 0.7.
Single driver advantage. Cone area about the same.
More cone break-up maybe, but spending the same dollars for one as three 6" may solve that.
I'm looking at doing this to compliment my bass horn and horn tweeter and still keep within the limits of the "Beyond ..." OB theory.
It's not cone, not horn.
Zene
Why not a 12" dipole waveguide for mids? Not a simple conical slab sides thing, but a true WG.
Rough estimates: 120 deg dispersion angle. 4" deep, about 9-10" total depth front to rear.
Mounted in a Sonotube it can look cool and would hide all the crap on the outside of horn to assemble and dampen, foam fill, etc.
Better pattern control and coupling rather than just letting the 6" blast away into low impedance air.
Mouth 20" diameter which is a little big but thought a little larger than normal would help smooth things out a bit and allow for a large flange radius. A 4" bell radius keeps the flare to mouth area ratio around 0.7.
Single driver advantage. Cone area about the same.
More cone break-up maybe, but spending the same dollars for one as three 6" may solve that.
I'm looking at doing this to compliment my bass horn and horn tweeter and still keep within the limits of the "Beyond ..." OB theory.
It's not cone, not horn.
Zene
This quote was regarding the 18" Seleniums. I bought a pair of
15" drivers from them and designed a simple crossover based on their curve showing flat response and a steep rolloff without spikes. The crossover was very close to being correct, and the response sounds like the curve claimed.. good! I liked them better than the similar Eminences that I have heard..
Its refreshing to find curves that match pretty well, certainly not all the manufacturers we have looked into here are as forthcoming!
So I also agree that Selenium seems very honest. It's true- some of their mid have pretty horrible curves, but there they are on the spec sheet.
So, If you need lots of big drivers at a decent price in the lowest octaves where possibly the differences between drivers isn't as noticable , the Selenium 18" drivers might be a good choice..
like the above mentioned 18WS600 which costs $146.16 ea. at PArts experess
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-394
The one I mentioned may not be quite as flat but has over 6mm x-max and is $160:
http://www.partsexpress.com/pdf/264-387s.pdf
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-387
Re. 2123
Magnetar,
Thank you for the offer. I would like to get a pair of the 16 ohm drivers. I wanted to e-mail you directly rather than cluttering up the thread, but I have made so few posts that I remain under moderation and am not allowed yet! Please e-mail me if you are willing, or I assume (hope!) that at some point I'll be turned loose and can e-mail you!
Thank you,
Bill
Magnetar,
Thank you for the offer. I would like to get a pair of the 16 ohm drivers. I wanted to e-mail you directly rather than cluttering up the thread, but I have made so few posts that I remain under moderation and am not allowed yet! Please e-mail me if you are willing, or I assume (hope!) that at some point I'll be turned loose and can e-mail you!
Thank you,
Bill
Re: Re. 2123
Bill, I sent you mail
Here is a "review" of a low compromise open baffle system I had with the JBL 2123's as midrange-
Open Baffle Madness at my place
Bill Brown said:
Bill, I sent you mail
Here is a "review" of a low compromise open baffle system I had with the JBL 2123's as midrange-
Open Baffle Madness at my place
Zene Gillette said:
Well, a back-to-back LeCleac'h expansion has certainly occurred to me. Having neither horn-building nor horn-calculation skills (I wouldn't even know where to start on either), I don't know if a back-to-back horn would screw up all the length calculations or not. I have a suspicion it might, and the B-to-B horn would need to be an original finite-element calculation for the purpose - a dipolar 300 Hz to 3 kHz waveguide for a 6" driver. Finite-element calculations are way way way out of my league - I'm just a humble writer and part-time systems integrator, a very different skill set.
Since diaphragms are acoustically transparent, the front horn would probably "see" the presence of the symmetric rear horn, and I have a premonition it might make the triple peaks in the impedance curve look worse, not better - or maybe it might just shift them all down an octave since the effective length would be doubled. (I have this corny visualization of horns as being a subset of tuned pipes, at least close to the triple-peak region of operation, where the pipe modes are directly visible on the impedance plot.)
This might be an excursion into FUBAR territory, but it might be possible to stagger the lengths and sizes of the two horns in an attempt to smooth out the impedance curve - or it might be a resonant mess, with worse coloration than either horn/waveguide by itself.
I do know for tuned pipes (AKA transmission-line loudspeakers) it is sometimes desirable to place the driver at a critical part of the tuned pipe, and not on the ends. The same might be true of a dipole horn, which I suspect reduces to an open-ended tuned pipe at the lowest frequencies. This is the kind of thing that needs to modelled by a finite-element genius - hello out there, any takers???
<tap><tap>Is this thing on? Any takers? Anyone? Hellooo out there?
Another Link
Joe Rasmussen has a crossover design philosophy that overlaps with mine to a large degree. Not identical, mind you, but a lot of areas of agreement. I mainly use low-Q 2nd-order networks, but am quite partial to 1st-order combined with a notch filter as well, depending on what the driver wants to do.
Linear phase I can take or leave, but the phase angles between the drivers are very very important and are quite audible as "phasiness" with pink-noise stimulus. A correctly designed crossover does not sound "phasey" and more importantly, sounds like a single driver, even when quite close-up to the loudspeaker.
It is certainly true that high-quality cone drivers typically have a single well-defined peak at the top of the range, and this single peak is amenable to notch-filter equalization. I agree with Joe's comment these clean, well-defined peaks are not breakup, but are artifacts of the cone shape itself. They are especially evident in top-of-the-line cones with low inductance figures - in a more typical high-inductance driver, the peak is intentionally masked by voice-coil inductance. Since VC inductance is quite nonlinear, low inductance is a good thing - but it does make the FR look different than you might expect.
It's the drivers with ragged responses above the top of the range that are more problematic to cross over and equalize - any driver with a whizzer or poorly designed dustcap or phase plug qualifies here. These are the notorious directional peaks you've seen me complaining about - the famous KEF B110, as used in the BBC LS3/5a, had three directional peaks 100 Hz apart in the 3.5 kHz region, as well as a single broad peak at 1.5 kHz (which was equalized in the LS 3/5a crossover).
Joe Rasmussen has a crossover design philosophy that overlaps with mine to a large degree. Not identical, mind you, but a lot of areas of agreement. I mainly use low-Q 2nd-order networks, but am quite partial to 1st-order combined with a notch filter as well, depending on what the driver wants to do.
Linear phase I can take or leave, but the phase angles between the drivers are very very important and are quite audible as "phasiness" with pink-noise stimulus. A correctly designed crossover does not sound "phasey" and more importantly, sounds like a single driver, even when quite close-up to the loudspeaker.
It is certainly true that high-quality cone drivers typically have a single well-defined peak at the top of the range, and this single peak is amenable to notch-filter equalization. I agree with Joe's comment these clean, well-defined peaks are not breakup, but are artifacts of the cone shape itself. They are especially evident in top-of-the-line cones with low inductance figures - in a more typical high-inductance driver, the peak is intentionally masked by voice-coil inductance. Since VC inductance is quite nonlinear, low inductance is a good thing - but it does make the FR look different than you might expect.
It's the drivers with ragged responses above the top of the range that are more problematic to cross over and equalize - any driver with a whizzer or poorly designed dustcap or phase plug qualifies here. These are the notorious directional peaks you've seen me complaining about - the famous KEF B110, as used in the BBC LS3/5a, had three directional peaks 100 Hz apart in the 3.5 kHz region, as well as a single broad peak at 1.5 kHz (which was equalized in the LS 3/5a crossover).
Magnetar said:
Intentional dipole radiation pattern with characteristic low horn levels of IM distortion and headroom. Done correctly, there would be a strong similarity to what the Audio Kinesis system did at the RMAF with their two independent back-to-back waveguides. Subjectively, electrostatic spatiality with horn vividness, tone color, and effortless dynamics.
High-efficiency direct-radiator dipoles are already partway there - I keep gravitating back to the multiple-driver mids because it's what I know. With horns, I hear weird colorations, but don't really know enough about the technology to describe and analyze what I'm hearing. I can measure it easily enough - big time-domain troubles with many multipath reflections - but don't know how to fix them in their own domain.
Lynn Olson said:
I think you should borrow (I'd send you some but I'm using mine) some good mid horns from someone and listen to them with a good driver. They'll do everything you want to do without a back horn. The back need not be enclosed on a front mid horn and yes it will be 'different' from the front but so are most other dynamic driver dipole systems.
Duke built a bipole - not a dipole.
Lynn Olson said:
What horns with what colorations? I have heard PLENTY of bad horns, usually in the midrange they sound bad because they are too long , short horns may not meet the criteria of a 'true horn' but they sound good. as low as an electrostat in coloration IME plus more life and 'infliction'
Magnetar said:
It was great to meet him at the show and chat about his very impressive and sophisticated system. The bass was bipole (or effectively omni at those frequencies) but the front and back horns had independent crossovers and could be switched between bipole and dipole.
At the RMAF show, the two horns were running in dipole mode - I asked. The difference is kind of small, though, since the rear horn had a shaped response that was pretty much something like a 6 dB/oct rolloff starting at 20 kHz - an old trick I did on my first loudspeaker in 1976, the TLM-200, which had a rear tweeter with same kind of slope and turnover frequency. As a result, almost none of the rear tweeter sound diffracts around the front.
How would a purpose-designed dipole horn sound? Dunno, never heard one. I completely agree about open-backed cone drivers in horns - that's the way to go from what little I've heard around here. Even very small cylinders and short pipes on the back part of horn-loaded cone drivers really screws up the response and adds huge colorations.
I've come to the reluctant conclusion that horns actually magnify driver colorations, since the horn (or waveguide) requires a near-perfect wavefront to operate according to theory. I'm now beginning to suspect a subtle advantage of a simple cone driver over a compression driver and its associated phase plug is the wavefront going into the horn is closer to spherical or planar than it is with a CD/phase plug assembly - and the horn, being a simple passive device, magnifies the irregularities of the wavefront as it transits the horn. Again, this seems more appropriate for proper finite-element modelling instead of my idle speculations.
Magnetar said:
This is an important point. What is your subjective cutoff point for maximum allowable length before "horn" colorations start to intrude? 12"? 18"? Something around there? Very curious to hear your personal experience on this score.
I personally don't understand the discussion over the correct usage of "horn" vs "waveguide" - this appears to be a theological argument far beyond my understanding, but I know it generates endless heat in the high-efficiency world. Reminds me of discussions I heard when I was younger about the mystical meaning of the Holy Trinity (for Christians), or the subtle difference between "rebirth" and "reincarnation" (for Buddhists and Hindus).
Lynn Olson said:
That's cool switch from bipole to dipole on the fly! I did that with a system where I could go from 0 to 180 degrees electronically between back to back two wide range mids. LOL
A horn can SUPPRESS driver colorations! It is a transformer mating the driver with the air..... a good one with a correctly mated driver is a thing of beauty. A cone driver to me can sound better than a compression driver. It won't go as high but through it's range it can be incredible. The problem I've always had is finding a bass system that will keep up with it. Now bass horns can be really colored. They NEED to be long to work, too short and it's a nightmare. These dipoles do the trick in the bass and take up less room.
Lynn Olson said:
LOL - you are as close on the wave guide horn thing as I am. It's either one - like left/ right politics.
The horn should be 1/4 of a wavelength long at the cutoff frq or flare rate. Most are, IMO that's fine for PA directivity and SPL but not so right for home reproduction. For example I'm listening to 360 Hz cutoff flare horns right now that are only 6.5" deep. To be frank, I am a picky guy when it comes to sound and music and this works as good as anything I've heard.
If you look at the Sensitive Open Baffle Thread I posted a link to some articles by Edgar and Dinsdale earlier. They are informative. Edgar likes to get his hands dirty and experiment. Some times it's better than math. What you want to do has already been done (even back to back horns) and the horns can be built for you.
Link to Edgar Dinsdale thread
I've gone back and forth between bipole and dipole configuration for the back-to-back waveguides in the bipolar speaker that I showed at RMAF. I'm no longer sure there's a difference that exceeds my imagination threshold. Theoretically I think dipole might be best, as that would tend to average out (in the power response at least) any crossover region anomalies. Because the rear-firing waveguide would be in reverse phase relative to its woofer, any crossover region front-hemisphere "zigs" would be offest in the power response by the rear-firing combination's "zags". Maybe.
Duke
Duke
Gentlemen ... I hope we are talking about a true very short wide angled (i.e., 120 deg) waveguide which ain't a horn in the sense of much increased amplification. Throat is equal to cone Sd which would be the same driver cone area as desired for your mids. We are not talking about small tweeter compression driver WG's. They would be a single 12" as I stated, to get a very big mid sound, not two drivers back to back bipoles. Length is determined by mouth area and the included angle only. The major point is that it is a pseudo Open Baffle, just where the Ariel+ is leading. The rear WG just acts to equalize cone movement.
If it won't couple to the air better than a conventional speaker I'll eat worms. That's what a WG does. The rear firing acoustical problems cannot be any different than any other OB. Is there some reason that the words, "ratty or distorted horn" pops up every time a WG is mentioned?
There is no reason not to look at large WG's. (yes, I know double neg.)
I hope some of you have looked at the WG spreadsheet Ed shares. Ask nicely ... Ed LaFontaine [gelafontaine@yahoo.com]
Earl ... help!
Zene
If it won't couple to the air better than a conventional speaker I'll eat worms. That's what a WG does. The rear firing acoustical problems cannot be any different than any other OB. Is there some reason that the words, "ratty or distorted horn" pops up every time a WG is mentioned?
There is no reason not to look at large WG's. (yes, I know double neg.)
I hope some of you have looked at the WG spreadsheet Ed shares. Ask nicely ... Ed LaFontaine [gelafontaine@yahoo.com]
Earl ... help!
Zene
I am thinking of combining the following speakers in open baffle, similar to what is being done here. I cannot afford some of the higher end options that have been listed here and was thinking of combining the following
4 x selenium 12pw3264 somewhat recommended over here by Magnetar
Price 40$ each and Specs
2x Peerless Exclusive 830883 - 7" woofers
price 76$ each and specs
1x bms4540 mounted to a DDS waveguide
price 69+96$ & specs from JonMarchall's measurements over at htguide forum
If anyone foresees any problem with these combinations or think I could make a better choice while still adhering to my budget, I would be grateful. I don’t want to order parts that will not work well together.
I have attached the measured SPLs from the links listed above for easier comparisons
4 x selenium 12pw3264 somewhat recommended over here by Magnetar
Price 40$ each and Specs
2x Peerless Exclusive 830883 - 7" woofers
price 76$ each and specs
1x bms4540 mounted to a DDS waveguide
price 69+96$ & specs from JonMarchall's measurements over at htguide forum
If anyone foresees any problem with these combinations or think I could make a better choice while still adhering to my budget, I would be grateful. I don’t want to order parts that will not work well together.
I have attached the measured SPLs from the links listed above for easier comparisons
