Homebrew Center channel speaker

[hjames]

My previous home theatre/multimedia system consisted of a pair of l36 decades on top of the shelves in my icon, and a JBL EC25BE 2-way Dual 5-inch Center Channel speaker (Beech) to match the beech shelves. It worked fairly well, sitting directly above the TV. I have a pair of G20s (I think) mounted on the back wall for surround, and a cheap Sony amplified Sub on the front-side of the room. I only use the sub and rear surrounds for movies - my JVC receiver is smart enough to remember settings, it just plays the front left/right speakers for music use.

In February I got the big 4320 monitors and have rebuilt them, adding 2405 slot tweeters and update the crossovers to match.

But now during TV and movies, the center channel audio (dialog) is distinctly different than the front left or right that comes from the horns (2420s - aka L85s) and slots of the big boxes.

After reading about similar projects from many folks here, I figured it just made good sense to make the front wall audio more consistant - so I've obtained another 2405 slot and an LE85 driver with 2307 horn and I plan to use them for the front center channel. I just ordered the parts to build another of Giskard's 4333/S300/L300 equivalent bandbass circuit - (the regular, not the Charge Coupled design) see - http://audioheritage.org/vbulletin/showpost.php?p=1042&postcount=3 (http://audioheritage.org/vbulletin/showpost.php?p=1042&postcount=3)I'm not in a rush to get another 15" just for center use - there should be plenty of Bass from the front left and right, the center is mostly dialog anyway.

I don't even think I really need to build a box for the compression drivers - maybe just a nice wooden tray to support them, tho it'd be nice to have a faceplate to velcro the lens to for the midhorn ...

I'll admit it - I've seen too many pictures of those Japanese collectors' systems with the exposed horns and lenses ... Geek tech!

[Robh3606]

Hello hjames

What are you going to use below the Le-85/2307 combo??? You need something to fill in the 70Hz- 1200Hz gap unless I missed something.

Rob:)

[hjames]

Hello hjames

What are you going to use below the Le-85/2307 combo??? You need something to fill in the 70Hz- 1200Hz gap unless I missed something.

Rob:)

Yes, I haven't chosen anything yet ... I'd like to stay with something smaller
not another 2215 - thats for sure ...

[toddalin]

The way my center channel is wired, I can use the 2235 woofer as the center speaker's woofer (with a 175/075), or in parallel with the W15GTI used as a sub mounted in the same cabinet (but separated). I use it in this configuration on occasion when using some of the Yamaha surround sound settings that do not use the center channel. (Talk about some thump!)

If I switch to DD and forget to reset the combined sub to the center speaker position, the sound is obviously weird and you would not want to listen like this.

I think you will need to strike a balance, and a 15" woofer may be the only really good way to do it. Besides, the center channel is the most important channel for movies. Why short change yourself there?

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/center-2235-w15gti.jpg

[hjames]

The way my center channel is wired, I can use the 2235 woofer as the center speaker's woofer (with a 175/075), or in parallel with the W15GTI used as a sub mounted in the same cabinet (but separated). I use it in this configuration on occasion when using some of the Yamaha surround sound settings that do not use the center channel. (Talk about some thump!)

If I switch to DD and forget to reset the combined sub to the center speaker position, the sound is obviously weird and you would not want to listen like this.

I think you will need to strike a balance, and a 15" woofer may be the only really good way to do it. Besides, the center channel is the most important channel for movies. Why short change yourself there?

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/center-2235-w15gti.jpg

Well - there is the Spouse Acceptance Factor -
There is no real room on the floor like in your home, and if I block any more of the window above the shelf ...

[clmrt]

Get out the fly hardware and paint it white?

You might have the most difficult room to make a center work.

What's that you have up there now, (edit - I just read le post) and is your TT sitting on it?

[hjames]

Get out the fly hardware and paint it white?

You might have the most difficult room to make a center work.

What's that you have up there now, and is your TT sitting on it?
The previous pix was from April -
I just updated it with a picture from a few moments ago ...

I have the 4320 on the left - my old Denon turntable next to it.
To the right is the JBL EC25BE center speaker - small, but it works - then some vases and art stuff, then the other 4320 on the far right.

All that sits on some 2000 CDs and a few less DVDs and videotapes -
the LPs are in another room ...

I do have a Sony subwoofer on the floor against the right wall, and I figure to replace that with a JBL sub one day.

Or just toss the whole thing out there on ebay and get a pair of 4345s that Ian and Ducatista47 are so hot for ...
why settle for 15s when you can have 18s ...

[John W]

It might be a good idea to set the drivers on top of your cabinet before you get too far and see if the magnets on the LE85 effect your TV. There may be a need to increase the distance from the picture tube or otherwise provide some magnetic shielding.

I just acquired a pair of woofers from an L46 that would make an interesting center channel with your other drivers, something like this. ;)

[JBLnsince1959]

hi Heather:


Rob is right in that you'll need something below the 85's

I'll recommend using one or two E110's or their equivalents ( or two E120's)for the freq. below the compression driver.

I used TWO C35's for my center and the E-130 is excellent for the mid bass and lower midrange, I'm sure the E110's would be great to..

One important thing to remember, keep the horns all about the same horizonal level if you can so when something pans across it doesn't jump up and down. Below is a picture of the C35's when I was using them, notice that they were upside down and sitting on a pair of professionally made 2235's so that the horns would be at the same level as the horns on the 4430's, the 4430's were my left and rights.

By the way, how's old Boz Scaggs sound thru those speakers.

Good luck

PS Edited later: you may also try two 2118's, but I think the E110's ( or E120's)would match better with the 85's, you may have to tone it all down a little to match with your left and right. Those E speakers are really something.

you could use the following configuration.

E110 - LE85 ( tweeter above) - E110

[grumpy]

:eek:

[hjames]

It might be a good idea to set the drivers on top of your cabinet before you get too far and see if the magnets on the LE85 effect your TV. There may be a need to increase the distance from the picture tube or otherwise provide some magnetic shielding.

I just acquired a pair of woofers from an L46 that would make an interesting center channel with your other drivers, something like this. ;)


Oh NO! Mr Bill!

[toddalin]

It might be a good idea to set the drivers on top of your cabinet before you get too far and see if the magnets on the LE85 effect your TV. There may be a need to increase the distance from the picture tube or otherwise provide some magnetic shielding.

I just acquired a pair of woofers from an L46 that would make an interesting center channel with your other drivers, something like this. ;)

Precisely why I put the ports on the top and components low in the cabinet. I used to sit my Mits 45" table top on the cabinet. Even with components mounted low, there was still some minor color aberations.

[JBLnsince1959]

Oh NO! Mr Bill!
:rotfl:

[jbl4ever]

Look for a 4612 used


http://dmbshare.org/pictures/20061018/1.jpg

[hjames]

Look for a 4612 used


http://dmbshare.org/pictures/20061018/1.jpg


No no no - I'm trying to NOT go completely overboard with the geek-with-big-speakers style ... but really, if I put one more big speaker on top of the shelf, I may as well board up the window ...
I mean - why not just get another 4320/4333? they'd match.

[jbl4ever]

4612 are 2-2118 and 1-2404. And yes smaller than the 4333 for my center

[hjames]

4612 are 2-2118 and 1-2404. And yes smaller than the 4333 for my center
Yeah - but if all I need is a woofer, why change the quality of mids and highs? I already have 2405 (alnico) and have a 2420 w/2307 horn (due Friday via FredEx) that exactly matches whats in the 4320s.

I've bought parts to build a Giskard 3133 crossover to feed the mids and highs to the horn and slot. If I feed the lows to the EC25, it won't be perfect, but I'll see daylight around it, and the mid & upper freqs will certainly improve ...
I could live for a while with such a "hybrid" - that JBL EC25 has a pair of 5" woofers -

Heck, I could do worse ...
at least its not ... uh, uh ... whats that brand that rhymes with Nose ...

[JBLnsince1959]

Hi Heather :

looks like you're stuck between a rock and hard spot for sure. If you get a center that matches the left and right speakers it's too big and blocks the window. If you get something small that doesn't block the window, it doesn't match the "voicing" of the left and rights..

and then there's the "spouse" factor......

Wecome to the JBL club.....;)

wish you all the luck with this...some times it's not easy being a JBL lover....

[grumpy]

Existing MF/HF over/under in the center and an LE10A type driver on each side?
-grumpy

[JBLnsince1959]

Existing MF/HF over/under in the center and an LE10A type driver on each side?
-grumpy

that's close to what I was saying ( only with E110's or 2118's). She needs something small that's for sure and it needs to be spread out horizonally and low....tough call

[grumpy]

that's close to what I was saying
Yup, so I was essentially agreeing ;) The older alnico units might cause less problems
with a CRT, and I'm partial to the foam-surround 10" driver. Let the square edges of the
frame go flush with the top/bottom and go deep for volume :) -grumpy

[JBLnsince1959]

I've bought parts to build a Giskard 3133 crossover to feed the mids and highs to the horn and slot. If I feed the lows to the EC25, it won't be perfect, but I'll see daylight around it, and the mid & upper freqs will certainly improve ...
I could live for a while with such a "hybrid" - that JBL EC25 has a pair of 5" woofers -



You may have to, however, there will a BIG imbalance between the lower Freq. and the mids and high. Most of the fundamental Freq of the human voice are around 110 to 1100 with most below 600.

You could always try watching your movies in stereo and see how it sounds. I'm not big into center speakers anymore ( altho I loved those BIG old C-35's - lady won't allow that tho:p )

for now doing movies in stereo might give you time. It sounds really good when you watch movies in stereo even I know it's not fashionable.

well, I've said enough...good luck

[Rusnzha]

Add a couple of 116h or 117h 8' speakers on ether side of the horn and slot and you would have a real nice center channel. 116As would be even better if you can find them. It would sound like the bass from your bigger speakers was coming out of it and it wouldn't eat up all your space.

[Zilch]

Add a couple of 116h or 117h 8' speakers on eother side of the horn and slot and you would have a real nice center channel.And do what about the crossover impedance problem?

Doubtless, there is an easy solution. I'm just not aware of it....

[Robh3606]

Those main speakers are a hard act to follow. To do a center is not all that easy with the restricted space you have overhead. I ended up with a Urei 811C clone but I had the room. Your on the right track though I found that the only thing that could really match my mains was a center with a compression driver and similar bass driver to match my mains. I tried a Jubal and it couldn't cut it. You may want to go with a pair of 2118J's but if that's a direct view TV that may not work at all. Alnico's would be the best bet if you can't get sheilded drivers.

Rob:)

[hjames]

Those main speakers are a hard act to follow. To do a center is not all that easy with the restricted space you have overhead. I ended up with a Urei 811C clone but I had the room. Your on the right track though I found that the only thing that could really match my mains was a center with a compression driver and similar bass driver to match my mains. I tried a Jubal and it couldn't cut it. You may want to go with a pair of 2118J's but if that's a direct view TV that may not work at all. Alnico's would be the best bet if you can't get sheilded drivers.

Rob:)

Yes - the set is a 34" Philips HD with CRT - big ol heavy picture tube thing!

Thanks to everybody for all the good ideas!

Ah well - all I can do is try and see what I can bear to live with. To be honest, even with the little JBL center speaker I still enjoy the sound of movies in 5.1 dts or DD format - I'm just not likely to watch many movies in stereo after experiencing Private Ryan or some other films in surround.
Now I need to build the crossover and hook up the horn and slots and see what I have ...

[Rusnzha]

Originally written by Robh3606


And do what about the crossover impedance problem?

They sounded nice in theory, but that shows you what I know.

[GordonW]

Anyone got any derelict 116A frames around? It'd be interesting to see if you could "shoe-horn" a 2118J cone kit into a 116A frame. That'd make an alnico 16 ohm 8"... inherently shielded. Wouldn't matter if it matched any existing designs... he's BUILDING a cabinet, anyway, so he can tune it for whatever the parameters wind up being!

Regards,
Gordon.

[Zilch]

How about this: Biamp the mids and highs with the $30 PE T-Amp?

Pair LE-10s gonna be the best woofer match, probably. Stack the mid/tweet between a pair of those.

116As in closed box would work, too, if Heather needs smaller, though LE10 sqircle frame's not that much larger....

[Pssst - Gordon, Heather's a girl. :) ]

[doyall]

Heather, maybe you just need a bigger house to support your habit! :D

[hjames]

How about this: Biamp the mids and highs with the $30 PE T-Amp?

Pair LE-10s gonna be the best woofer match, probably. Stack the mid/tweet between a pair of those.

116As in closed box would work, too, if you need smaller....
So - I wouldn't want to look for a pair of 2122s?

Dang!!

Guess I'll have to put them aside for now, until I get around to making up some 4345s ... sigh

[grumpy]

So - I wouldn't want to look for a pair of 2122s?

Sure you would! Just not necessarily for this ;) -grumpy

[Earl K]

Anyone got any derelict 116A frames around? It'd be interesting to see if you could "shoe-horn" a 2118J cone kit into a 116A frame. That'd make an alnico 16 ohm 8"... inherently shielded.

- Nice idea . I always enjoy your inventiveness . :p :)
- Though I do believe twin 2118a(s) "alnico/hybrids" / arranged with the DD66000 style of asymmetrical crossover, will better suit the sensitivitiy figure needed to keep up to her original woofers ( 2216s or le15b , unless I'm remembering her 4320(s)' components incorrectly ) .
- I'm thinking the target sensitivity for this box needs to be 96 or 97 db / a fairly tall order .



Wouldn't matter if it matched any existing designs... he's BUILDING a cabinet, anyway, so he can tune it for whatever the parameters wind up being!

- "She", Gordon ,,, "She" is having to build a cabinet for this project. :D


:)

PS - I don't do H.T. , so maybe I'll just shutup now .

[GordonW]

A few other options- I've used all of these woofers before, and can vouch, they DO work well:

Parts Express has a Dayton 6.5" shielded 4 ohm driver:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-308

A pair of these, wired in SERIES, would give 8 ohms. Very good bottom end whomp, good midbass, IME.

Or, for more horsepower, the 8" DVC driver. They call it a sub, but it's fine out to 1KHz:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-480

Wire the voice coils in each drivers in SERIES (to make 16 ohm drivers), then wire the two drivers in parallel, to get back to 8 ohms. These things have SERIOUS whomp, for what they are, and are pretty clean sounding to boot...

Regards,
Gordon.

[Earl K]

So - I wouldn't want to look for a pair of 2122s?

Dang!!

- Sure you should, everyone should own a pair . :D

- If you put new 2122H cone kits into K110 baskets ( alnico magnets ) you could use them for this project of a center speaker .
- I do have mixed feelings about "wasting" those cone kits in an alnico magnet-assembly.



:p

[GordonW]

- "She", Gordon ,,, "She" is having to build a cabinet for this project. :D


:)



DOHHHHH!!!!!!!!! :banghead: :banghead: :banghead: :banghead: :banghead:

Regards,
Gordon.

[GordonW]

- Sure you should, everyone should own a pair . :D

- If you put new 2122H cone kits into K110 baskets ( alnico magnets ) you could use them for this project of a center speaker .
- I do have mixed feelings about "wasting" those cone kits in a alnico magnet assembly.



:p

Still have the 8 ohm issue... 2122H are 8 ohm each. Would need 16 ohm kits.

2123J kits in K110, LE10A or D110 baskets would work, and would not "waste" scarce 2122 kits (and it would cost less, too!). Probably would want to have someone coat the cones with "wet look" or something, to tame down the rising response a bit, to make 'em match the 3133 crossover better...

Regards,
Gordon.

[Robh3606]

So - I wouldn't want to look for a pair of 2122s?

Dang!!

Ideally you would want 16 ohm drivers and Alnico at that. The 2122's will work however they are ferrite and 8 ohms. The 8 ohms may not be a problem depending on the amp. You could look for some older 10" frames like the 2121 or K110/Le-10A that are Alnico and drop 2122 cone kits into them after they are recharged and checked out. You need to make sure first that the 2122 kits will work in those cores. If you get a good working pair of Le-10A's just use them however box size may still be a proplem. If I were you I would do a cardboard mock-up of the front baffle to see just how much space a pair of 10" drivers the 5x10" Lense and the 2405 will take up. You may only end up wanting to do a single 2122/Le10 and lay it down like the L and Right. Would make things a bit easier.

Rob:)

[Earl K]

Still have the 8 ohm issue... 2122H are 8 ohm each. Would need 16 ohm kits.


Ideally you would want 16 ohm drivers and Alnico at that. The 2122's will work however they are ferrite and 8 ohms.

- I can see there's a fundamental difference in opinion on this matter of what driver impedances are needed to make this work ( assuming the use of midrange-efficient / bass-shy transducers ) .

- I was envisioning a crossover design that presents ( to the amp ) an asymmetrical impedance load from the twinned woofer section . ie; ( from LF to MF ) transitioning from @ 4 ohms, up to 8 ohms .
- The 4 ohms "pulls" more current only in the LF area and reinforces just this lower frequency range .
- ie; With a large inline coil ( on just a single woofer ) adding its' ever climbing series impedance into the overall ( paralleled ) load / by the crossover point the composite ( woofer ) load is more or less back to where it should be ( from a sensitivity perspective ).
- This of course requires an amp that is stable, driving a 4 ohm load into the lower frequencies .


:)

[speakerdave]

You do need the low loss Alnico magnet structures JBL used on its classic drivers, or, alternatively, a modern self-shielding neodymium driver. The LE10A (or L111A, if you prefer the black woofer cone) is likely the best match to your front L/R speakers. I'm not aware of 16 ohm versions, although the early literature lists them as 8-16 ohms under JBL's old flex-impedance standard. The easiest way to test this idea may be to set some L77's up there on either side of your horn and UHF. Custom cabinets could be minimum height, and you could get the required volume with your shelf depth.

There is a driver that would meet all your specified conditions, but it is rare, and that is the 2115B. That would give you plenty of life in the voice range, and it can be used in a 1-foot cabinet. The eight-inch frame would save you another 2" of cabinet height blocking the light. It wouldn't give you the bass depth of the LE10 family with their larger surfaces and aquaplased cones, but it would be a much better sensitivity match (92 dB plus acoustic coupling of 3 dB) and impedance match--the "B" is sixteen ohms. Be aware, though, these are not reconeable so you need a clean pair. The LE8T-2 is a similar driver, but I'm not aware of 16-ohm versions; it is somewhat less rare (used in the S109/Aquarius 4). The LE8T is much more common, but is unfortunately not a sensitivity match, even in pairs, making biamping, the only way to use them. Biamping would also solve the impedance issue, remember.

If you decide to surrender more light, there are a number of woofers in the 123A family that would work. A pair would have nearly the same cone surface as a 15, and you could make flatter custom cabinets. The 122A from the L65B might be the best of these for you, despite what Rob says about it not working for him (he's using E145 midbasses over LE14A's, after all!). In this size the very best modern self-shielding JBL woofer is the 252G from the LSR series, but it is 4-ohms. Again you could make your cabinet top and bottom tight to the woofer frame to leave as much window uncovered as you can and use your shelf depth to make up the volume you need.

David

[Zilch]

I'm seeing the stacked horn and slot as controlling the minimum height.

Biamp's not a big deal. The T-Amp can easily drive the MF/HF:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-952

Too cheap? There's also this one:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-956

Either one with the main amp would TRIamp a center channel, if you just HADTA tweak it to the max.... :p

[speakerdave]

I'm seeing the stacked horn and slot as controlling the minimum height....

Yes, but it could be a bump in the middle.

David

[Robh3606]

The 122A from the L65B might be the best of these for you, despite what Rob says about it not working for him (he's using E145 midbasses over LE14A's, after all!).

Hello Dave

The top didn't work! The Le-5 just doesn't cut it compared to a 2425:D . I like your suggestion of a single woofer and a 122A is good chioce. That worked just fine. I am just concerned about the overall baffle size and it being too big when all is said and done.

Rob:)

Rob

[speakerdave]

. . . . The top didn't work! The Le-5 just doesn't cut it compared to a 2425. . . . .

I think we came to the same conclusion about that. I finally had to put my L65's behind an upholstered chair.

David

[Robh3606]

Hello Earl


The 2122's will work however they are ferrite and 8 ohms.

More for the ferrite than the 8 ohms.


The 8 ohms may not be a problem depending on the amp.


transitioning from @ 4 ohms, up to 8 ohms .

It may a bit lower that that depending on the drivers.

http://www.audioheritage.org/vbulletin/showthread.php?t=10663

http://www.audioheritage.org/vbulletin/showthread.php?t=10637


Just trying to stay "safe". Center channels get quite a workout.

Rob:)

[speakerdave]

Pair of properly refoamed 122A's on ebay, $175 BIN. (I've no knowledge or connection with this seller--the usual caveats.)

http://cgi.ebay.com/Pair-JBL-Vintage-122A-1-ALNICO-Woofers-l65-Jubal-L100_W0QQitemZ300040404591QQihZ020QQcategoryZ61377 QQrdZ1QQcmdZViewItem

David

[grumpy]

one could consider laying whatever mid/bass driver back flat, or nearly so, and
reflect or poorly horn load it or them to lower the profile further. Sort of an Aquarius notion,
but less than 180 deg spew... driver would have to be of the type that is happy in a
horizontal load position regarding worries about sag (I don't have that list) -grumpy

[northwood]

The way my center channel is wired, I can use the 2235 woofer as the center speaker's woofer (with a 175/075), or in parallel with the W15GTI used as a sub mounted in the same cabinet (but separated). I use it in this configuration on occasion when using some of the Yamaha surround sound settings that do not use the center channel. (Talk about some thump!)

If I switch to DD and forget to reset the combined sub to the center speaker position, the sound is obviously weird and you would not want to listen like this.

I think you will need to strike a balance, and a 15" woofer may be the only really good way to do it. Besides, the center channel is the most important channel for movies. Why short change yourself there?

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/center-2235-w15gti.jpg
I noticed this one long time ago,I like it,it's the best of the best of the best center speaker

[Fangio]

So - I wouldn't want to look for a pair of 2122s?

Dang!!

Guess I'll have to put them aside for now, until I get around to making up some 4345s ... sigh
Heather, thanks for bringing this up - great advice assembled above, aplenty of info on issues from soo many knowledgables - particularly about the 8 ohms 2122H in a 16 ohm alnico environment..................

Interesting thread and project. There is some overlapping with mine - going to follow further considerations with attention. :)

[hjames]

Yes - the set is a 34" Philips HD with CRT - big ol heavy picture tube thing!

Thanks to everybody for all the good ideas!

Ah well - all I can do is try and see what I can bear to live with. To be honest, even with the little JBL center speaker I still enjoy the sound of movies in 5.1 dts or DD format - I'm just not likely to watch many movies in stereo after experiencing Private Ryan or some other films in surround.
Now I need to build the crossover and hook up the horn and slots and see what I have ...
Okay - I have the raw speakers in place - feeding my JVC receiver front center audio to the Giskard 3133 equiv network. Horn and slot seem to work fine tho its a bit bright on shows like NBCs Heroes in HDTV ...
not much bass feeding the LO side of the xover to the old center speaker (pretty much what we all expected) - but thats just a temporary placeholder until I find something better and figure what to do for a box (next month ...)

Meanwhile, the 2123s are on the way ...
now - how to integrate them into my 4320/4333clones?

[Earl K]

Meanwhile, the 2123s are on the way ...
now - how to integrate them into my 4320/4333clones?

- Were these 2123s purchased as an add-on to your 4320s ?
- What impedances are these 2123s ?
- If you're wanting to make your 4320s into a 4way / then download the 4344mkII network schematics. This schematic represents a good "study" of how JBL used network design to integrate the ( 8 ohm ) 2123H .
- Physical integration ? I believe you're pretty MUCH stuck with placing your 2123s in their own sealed enclosures / sitting outside of the main enclosures .


:)

[Earl K]

Okay - I have the raw speakers in place - feeding my JVC receiver front center audio to the Giskard 3133 equiv network. Horn and slot seem to work fine tho its a bit bright on shows like NBCs Heroes in HDTV ...
not much bass feeding the LO side of the xover to the old center speaker (pretty much what we all expected) - but thats just a temporary placeholder until I find something better and figure what to do for a box (next month ...)

FWIW ; I think a slot tweeter is superfluous to the needs of a center speaker.
- It's quite easy to take the le85 out to 12.5K / which / IMO / is more than high enough .
- Just my opinion / and you know I don't do H.T.

- The 3133 network was meant for use with the 2312 ( H92 ) horn / not the 2307 ( H91 ).
- I'd use a variation of the N200 which uses a 3-pole bump filter to reinforce the anemic performance of the 2307 ( that one octave just before cutoff ) . Zilch has done some relevant work to that circuit / for use with or without the 2405.


:)

[Robh3606]

FWIW ; I think a slot tweeter is superfluous to the needs of a center speaker.
- It's quite easy to take the le85 out to 12.5K / which / IMO / is more than high enough .
- Just my opinion / and you know I don't do H.T.


Hello Earl

That would be a big mistake.There is a lot more than voice in the center channel and more importantly you will hear it with any pans across the front speakers.

Hello Heather

I hope you realize those 2123's are unshielded ferrites

Rob:)

[hjames]

Hello Earl

That would be a big mistake.There is a lot more than voice in the center channel and more importantly you will hear it with any pans across the front speakers.

Hello Heather

I hope you realize those 2123's are unshielded ferrites

Rob:)

Yes - my long term plan is to use the 2123s with my corner speakers, the 4320s - (currently using all AlNiCo components) ...

From all I've read, I really doubt I'd use them in the center -
but they'll be good to save for the day I start mocking up a pair of 4344 clones from the existing 4320s... (yes, I know I need better than my existing 2215s to do that right).

I gather they would be good as a MidBass driver, just above the main Low Bass drivers (15s) which would handle say ... 35 or so to 300Hz, and under the 2420s which would be the HF ...

[JBLnsince1959]

Hello Earl

That would be a big mistake.There is a lot more than voice in the center channel and more importantly you will hear it with any pans across the front speakers.

Hello Heather

I hope you realize those 2123's are unshielded ferrites

Rob:)

exactly.....Rob knows what he's talking about....

[Earl K]

Hi Heather,

Once you get your 2123 midrangers you may want to play around with them.

- ie ; You may decide to try to make them work as drivers for a center channel .

- So; apart from the fact that the magnets are unshielded, there's another issue. That is , they are pretty "light" in the lower midrange area below 300 hz. I use these in some custom designed SR enclosures and they do require EQ below 300 hz to make them usable for even just a "balanced" voice sound .

- I've prepared a PowerPoint pic of some comparitive FR studies for various JBL 10 inchers. Unfortunately, the official "public" FR study for the 2123 is pretty optimistic / whereas the 251J and 2122H will be closer to the truth .
It would be nice to see a CLIO workup on the 2123 / measured close in / housed in a larger enclosure , such as .75 cu' or so .

- If you are going to attempt to make them work ( the 2123 ) then you'll need to get very creative in the design of the lowpass section for any crossover you buildup. I've included one creative solution ( designed by GT I assume ) for a driver that in balance, has a lot more lower mid than the 2123h. I included the 2122H for the sake of more comparisons.

:)

[Earl K]

- The 2123 can be put into a larger enclosure and ported / but it still won't "tune up" very well.
- It'll still need very creative network design to get a relatively flat response, from 80hz to 800 hz .

- I find that it's impossible to get flat response down to 100 hz (for the 2123 ) with any sort of alignment.
( OTOH, the 2012 is easier to tuneup into a more reasonable response . )

- Here's an alignment quite similar to what I presently use in my small cabinets ;
- The acoustic boost, occuring between 100 hz and 200 hz still won't completely flatten the 2123(s)' lowmid response, ( "in real life" ) .
- Note ; I've used JBLs' older ts parameters for this sim and the sim is done using software that is pretty iffy with my present operating system .
- Acoustically, I know the response is still droopy below 300 hz / even with this type of "boost" alignment .

:)

[JBLnsince1959]

-

That is , they are pretty "light" in the lower midrange area below 300 hz. I use these in some custom designed SR enclosures and they do require EQ below 300 hz to make them usable for even just a "balanced" voice sound .

I find that it's impossible to get flat response down to 100 hz (for the 2123 ) with any sort of alignment.


- :)

I have a pair of those and I've play with them for years and you are dead on. In fact I never cared for them much below 400, but that's a personal thing, just to "thin" for me ( I love the 2202 ;) )

trying to use the 2123's around 80 to 300 would be more trouble than it's worth and still they may not sound right. If she had the room a pair of 2206's may work pretty good. But then space ( or the lack of) is the real issue.

BTW, love those graphs....

[Earl K]

CLICK HERE ! (http://www.partsexpress.com/webpage.cfm?&WebPage_ID=3&ObjectGroup_ID=571&SO=2&CFID=136133&CFTOKEN=51263407) to see some "Bucking Magnets" available from Parts Express'

- If I was serious about making a center channel out of ferrite magneted drivers / I'd want to invest in a handful of these things,( even if just to try them out ) .
-Thankfully , these are quite inexpensive .
- Considering how much magnetic weight JBL uses in their drivers, I believe only the largest available from P.E. would come close to offering the needed CRT protection . I wonder if one can double-up these things.
- Being able to deal with Ferrite magnets should open up a broader range of possibilities by using JBLs' newer/smaller ferrite offerings ( maybe 4, 116h-1 or 127H-1s, wired in series/parallel - to get that sensitivity figure up ) .


BTW, love those graphs....
Thanks ! Also, don't take the sims that I run as gospel. They're done with software that is flakey at best with the operating system that I'm presently using. Others should run their own sims on BBP6 to check for themselves .

trying to use the 2123's around 80 to 300 would be more trouble than it's worth and still they may not sound right. If she had the room a pair of 2206's may work pretty good. But then space ( or the lack of) is the real issue.
It'll be some trouble for sure. Too much ? I don't know.
- I never want to underestimate the inventiveness of the "motivated" .
- I know from experience that 2123s can be used ( as mentioned, with EQ ) in a 2-way SR box, quite successfully ( as long as a sub is present for all the VLF duties ). I have clients who prefer this "sound" compared to what one is able to achieve with more "full-range" 2 way designs using 12s or 15s .

- "Inventiveness" could mean adding some weight to those 2123 cones ( ie; 10-20 grams of added cone weight, maybe aquaplas or some standin ). For sure it'll mean some "inventive crossover design" in the lowpass section ( ie ; extreme manipulation of the 2 drivers' FR curve / & very likely, utilising one 10" as a "helper woofer" for what little LF can be derived from it ) .

:)

[JBLnsince1959]

It'll be some trouble for sure. Too much ? I don't know.

:)

Well, I was speaking from my respective:p . Someone with your knowledge and experience could work it out I'm sure.

Everything I tried never worked to my likeing, so I'm planning to use them in my next "Super Center Speaker" incarnation. personally once below 400 I find the sound to "thin" for my likeing, but that's a personal taste. Other people didn't mind...

great idea, I never thought about adding mass:applaud: , but then I'm not that smart on buiding stuff and as far redesigning crossovers I'm brain dead...that's where I would personaly draw the line:D

I hope she gets something that both fits and matches in sound..

[northwood]

Look for a 4612 used



http://dmbshare.org/pictures/20061018/1.jpg
Jesus,so many...............
where r u my buddy:)

[hjames]

I'm looking at buying a cheap set of 2800s as auxiliary cabinets - pull the original drivers, seal the ports, and use the boxes to house the 2123s ... Box dimensions are 22.5 x 11 x 9.5 (mini-towers) but I can lay them on their side. Thats bigger than the 2121 midbass dogboxes in a 4345
(15.5 x 11 x 6), but not horribly so ...

Again - it does sound like they'd work better in the corners as quasi 4344 updates for my 4320s than as woofers for my center speaker.




Hi Heather,

Once you get your 2123 midrangers you may want to play around with them.

- ie ; You may decide to try to make them work as drivers for a center channel .

- So; apart from the fact that the magnets are unshielded, there's another issue. That is , they are pretty "light" in the lower midrange area below 300 hz. I use these in some custom designed SR enclosures and they do require EQ below 300 hz to make them usable for even just a "balanced" voice sound .

- I've prepared a PowerPoint pic of some comparitive FR studies for various JBL 10 inchers. Unfortunately, the official "public" FR study for the 2123 is pretty optimistic / whereas the 251J and 2122H will be closer to the truth .
It would be nice to see a CLIO workup on the 2123 / measured close in / housed in a larger enclosure , such as .75 cu' or so .

- If you are going to attempt to make them work ( the 2123 ) then you'll need to get very creative in the design of the lowpass section for any crossover you buildup. I've included one creative solution ( designed by GT I assume ) for a driver that in balance, has a lot more lower mid than the 2123h. I included the 2122H for the sake of more comparisons.

:)