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DAVID POHLER
11-10-2004, 05:23 AM
First, let me say what a great site this is, wish I found it sooner!! It's nice to know I'm not the only one obssed with the JBL sound.

I'm setting up a 5.1 surround system and could use some advise with the center channel. My thoughts:(2) LE10, (1) LE175, (1) 075 crossed at 1500hz & 7000hz using a LX10 & N7000 network. Each LE10 would be in its own 1.25cu.ft. compartment.

Most of the time I listen to music in 2channel format. For the most part Jazz is my game. My front channel is a pair of 4343B, (new arrivals). :D

Am I going in the wrong direction :confused: Should I find a factory setup and adapt it? Any thoughts would be appreciated.

Thanks much,
Dave

Robh3606
11-10-2004, 07:23 AM
Sounds like a good direction on the center. You should reasonable match the L/C/R and what you are proposing sounds like a good match. I would upgrade the 175 to a 2425 or 2426 though. Lot's of power in that front channel with HT.


Rob:)

GordonW
11-10-2004, 10:19 AM
I dunno, Rob. An original (re-gaussed) LE175, an original 075 or 077 supertweeter (I'd use the 077/2405, it's what's in the 43XX monitors), and a pair of original LE10As would all be ALNICO POT magnet assemblies, and should be reasonably well SHIELDED, as a result. A 2425 or 2426 would be a CERAMIC magnet, and would NOT have NEARLY the degree of video shielding.

If you DID want to use the bigger-magnet version of the driver, I'd use a 2420 or LE85. They're also alnico...

My only crossover change, would be to use the N8000 rather than the N7000. The preponderance of experience here on the LH board says (and my own personal experience bears out, too) that the supertweeters sound better crossed over, the HIGHER the BETTER. The last system I did using one (a 2404H) paired up with a 2410 (same as a LE175) wound up with the crossover point being around 11KHz. Now, that was for an extremely "high-power" app (the guy was matching it up with 4560 Perkins horns with 2225H woofers and 2445/2382 horns, on mondo power)... so 8000 Hz should be just fine, especially with a good 077/2405 alnico...

Robh3606
11-10-2004, 10:40 AM
"I dunno, Rob. An original (re-gaussed) LE175, an original 075 or 077 supertweeter (I'd use the 077/2405, it's what's in the 43XX monitors), and a pair of original LE10As would all be ALNICO POT magnet assemblies, and should be reasonably well SHIELDED, as a result. A 2425 or 2426 would be a CERAMIC magnet, and would NOT have NEARLY the degree of video shielding."

I have used a Jubal Center and the 077 was a PITA because of the very resticted Vertical Dispersion like 20 degress up high. The 075 has twice that. I know it doesn't go as high but if you have it why not try??

Opps correction the 075/2402 has the same almost at 15K!! Potentially the same problem got to be aimed at you.

Good point on the shielding:thmbsup: but if it's not direct view it doesn't matter. He doesn't say if they LE-10's are A's or H's. I guess we will find out!

Rob:)

DAVID POHLER
11-10-2004, 06:08 PM
Robh/Gordon:

I have a pair of LE10A baskets, (very bad surrond repair). They will need to be re-gaussed, cone kits as well. Should I have them reconed as 2121H.

I also own a spare 075 driver. I'll try that first. If I use a LE85 (2420) what horn should I use, HL87 or HL91? There is also a shorter version of the HL87, (for 1500hz) don't know the # off hand. If I go with the HL91 I'll also need a lens.

All opions welcome,
Thanks
Dave

Robh3606
11-11-2004, 02:18 PM
You know Gordon does raises a good point. Since you are using 4343's why not set-up the center to follow suite. Figure the 2 10's can act as the 2231/2121 combo with the compression driver and 075 as the top. That said why not cross the 10's over to the compression driver at the same frequency use the same horn and lense and then cross the 075 again at the same point. I would be worried about 2 10's in a horizontal layout. How are you going to set things up on the baffle??? Do you have to worry about shielding??? As far as reconning with 2122 kits?? I really don't know. I would be inclined to use a standard Le-10 kit as you have real woofers there. I don't know how low and with how much power you can run the 2122's. I have only used them as midranges from 300 to 1.2K

Rob:)

DAVID POHLER
11-11-2004, 03:07 PM
My original baffle plan was to lay things out horizontally. LE10 on each end, HL87 & 075 in center, (stacked with 075 on top). I was going to use the 1500hz crossover point because the LX10 seemed to be a good choice with the drivers I was using. It's also eaiser for me to purchase a crossover verses attempting to buid one. I chose the HL87 horn because it was not going to be positioned on top of the LF driver.

1. What problems can be encountered using -2- drivers on a horz. plane?

2. Please explain what video shielding I will need.

Thanks again,
Dave

Robh3606
11-11-2004, 03:42 PM
1. What problems can be encountered using -2- drivers on a horz. plane?

All center channels have issue using the arrangement. You get lobing and cancelation problems that end up in the horizontal plane. The idea is to get the crossover low enough so the driver spacing is not an issue. If you are on axis or not to far off center in may never be an issue.

2. Please explain what video shielding I will need.

Not video but magnetic shielding. A direct view TV as in your standard television does not like stray magnetic fields which is why all HT speakers have "shielding" which minimizes or cancels with a bucking magnet the stray magnetic field from you speaker drivers. If you want to see what it looks like very carefully approach your TV holding a driver. You will see the colors change. JBL Alnico drivers are shielded because they use magnetic structures that form a closed circuit so very little of the field escapes. By the way not all alnico just the ones with closed pots like JBL or Altec as an example. There are open pot alnico's which are not nearly as well shielded.

Good idea on the HL87. With the 2307/2308 you are pushing the 10's further apart or?? Why not set them up like a Lancer L 77 and put the 075/077 where the Le20 would go and drop the horn on top right over the 075/077?? That way you can get the 10's real close and you can use any horn you want.





Rob:)

Mr. Widget
11-11-2004, 03:51 PM
Is this the layout you have in mind?

If you are using all alnico drivers, they are inherently magnetically shielded. If you use the newer "H" versions with ferrite magnets it will be a bit of a challenge to shield them.

Widget

DAVID POHLER
11-11-2004, 04:05 PM
I was planning to space the le10's further apart, dropping the HF drivers between them, (stacked).

In a horizontal layout, is it best to have them close, (directly next to each other).

Thanks,
Dave

GordonW
11-12-2004, 10:51 AM
With an HL87 horn and a 1200 Hz crossover, it should be OK with the horn/tweeter "stack" to be between the 2 10" woofers. That's still a pretty close center-to-center distance. Heck, it's better phasing than most of the MTM center channels commercially sold... two 10" woofers with 1200 Hz crossover is LESS of a wavelength "alignment error" at crossover than 4.5" woofers at 3000 Hz (done on MANY center channel speakers)...

Here's how I'd place the drivers. Put the tweeter in the very center, raise the mid a bit... that'll get the closest CTC spacing possible without making a tall cabinet...

(oops, noted a typo... on the pic, where it says '077', it should say '075'...)

Mr. Widget
11-12-2004, 11:48 AM
I certainly agree that Gordon's layout looks nicer, though I would bet the layout I posted with the woofers closer together and the HF units stacked above would sound better.

This drawing is to scale. It would be difficult to construct with separate chambers for each woofer. I realize you can use a common enclosure, but dual chambers usually sounds better. There is also the issue of not much wood around the closely spaced cutouts. This could be a structural problem.

Widget

GordonW
11-12-2004, 12:40 PM
Yeah, WRT the baffle, I'd DEFINITELY use birch plywood, marine ply or something REALLY STRONG for the baffle. Also, I'd support the back of the HL87 horn with a top-to-bottom brace, to make sure the horn doesn't "lever itself" and break the baffle board.

As far as dividing the cabinet- personally, I've built lots of center channels with common cabinets- as long as the woofers are wired in PARALLEL, it shouldn't be a problem. This might require custom-reconing the LE10s, to use 16 ohm voice coils... but that shouldn't be too bad, for someone who does aftermarket recones. The coils in the LE10 are the same dimensionally as several other models, some of which are available in 'J' versions. I'd certainly think I could find a recone kit that would take care of this, if necessary...

Regards,
Gordon.

Mr. Widget
11-12-2004, 01:25 PM
Yeah, WRT the baffle, I'd DEFINITELY use birch plywood, marine ply or something REALLY STRONG for the baffle. Also, I'd support the back of the HL87 horn with a top-to-bottom brace, to make sure the horn doesn't "lever itself" and break the baffle board.
Exactly what I was thinking.


This might require custom-reconing the LE10s, to use 16 ohm voice coils... but that shouldn't be too bad, for someone who does aftermarket recones. You and your custom jobs....:hmm:

I agree with you about wiring the woofers in parallel. I would definitely use stock woofers and do a custom network though.

Widget

GordonW
11-12-2004, 08:58 PM
Well, if the amp is 4 (and preferably 2) ohm stable on the center channel, then the stock LE10As should work anyway. Just make sure that whoever does the crossover, compensates for the FOUR ohm load on the bass. Standard N1200 and such isn't going to work into 4 ohms... but you can probably just HALVE the inductor values and DOUBLE the cap values in the lowpass of an N1200, and have it work OK... that's the general effect of changing from 8 to 4 ohms, as far as crossover design is concerned...

If this is done, I would have someone run an impedence sweep on the completed system before putting into service, though. Just to make sure, there aren't any nasty little "near short" surprises at any frequencies for the amp to choke on. Doubt there will be a problem, as the DCR on an LE10 isn't THAT low, compared to other "8 ohm rated" JBL drivers... but it would be good to make sure.

DAVID POHLER
11-13-2004, 09:23 AM
You guys are very fast with the drawings!! Iím going to have to play catch up.



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S20RVERT
09-07-2010, 07:49 PM
28"W x 12"H x 18"D HDF with LE10A, PR10, 2405H, 2426J/2312/L94, 3110 & 3106. I tried a 2441/HL89 and 2410/2312/l94. I had a Klipsch Academy for a horn loaded center but saw this post and decided to go JBL to match my S20R's upgraded with 2450J/2380's.

Robh3606
09-07-2010, 07:54 PM
Nice that looks like a real kick ass center channel:applaud:. How do you like it? Do you run it fullrange?

Rob:)

S20RVERT
02-28-2011, 02:11 PM
Here are two more updates. I bought the fiberglas horn from a shop in Montreal and mated it to a 2450j and now have a 2397 on it. So far the 2397 sounds the best to my ear. I have no sound test equipment so I listen to one then change to another. Notice that I had to move the 077's when I exchanged the LE85/HL91's for 2450J/2380A's on my homemade S20R's built in 1974.

maxwedge
03-08-2011, 03:54 PM
Ah.......That spk is in the way of the TV sir!:crying: The Smith version looks quite cool. How do you keep it from falling over the back side? I know that the 2450 is some what light, but not that much?

I have some 2397's too but alas I have too many speakers in my living room already.:dancin:

toddalin
03-09-2011, 10:42 AM
Ah.......That spk is in the way of the TV sir!:crying:


It's a 4:3 screen. If you watch in 16:9 and place the image at the top of the screen, the speaker should not be in the way. ;)

At 78" dia., according to Stewart, I have the second smallest 4:3 Firehawk they ever made (at least at the time). Our 16:9 viewing is done at the bottom of the screen so you don't have to look "up" nearly as much. The smallest 4:3 Firehawk was 72" and I saw it being used in a booth at the CES in Las Vegas.
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/room1.jpg

maxwedge
03-09-2011, 07:21 PM
Ah.......That spk is in the way of the TV sir!:crying:


It's a 4:3 screen. If you watch in 16:9 and place the image at the top of the screen, the speaker should not be in the way. ;)

At 78" dia., according to Stewart, I have the second smallest 4:3 Firehawk they ever made (at least at the time). Our 16:9 viewing is done at the bottom of the screen so you don't have to look "up" nearly as much. The smallest 4:3 Firehawk was 72" and I saw it being used in a booth at the CES in Las Vegas.
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/room1.jpg
I put a thumbs up in there??:dont-know:

Nice room there, wish I had so much space. I need to move.

I don't know anything about the Firehawk, is that what his is too? I'm still in ctr mode with one of the last great ctr rear projection sets from Mitsubishi. It's very hard to beat the black levels of a good ctr.;) I just wish that when we got it we had the room for a 73 but had to settle for a 55.

I didn't know an image could be moved up and down like that except for the usual adjustments.:cool:

At least I can put a speaker on top of mine.:p

http://i76.photobucket.com/albums/j7/maxwedge572/Audio/DSC04945copy.jpg

toddalin
03-09-2011, 07:54 PM
I put a thumbs up in there??:dont-know:

Nice room there, wish I had so much space. I need to move.

I don't know anything about the Firehawk, is that what his is too? I'm still in ctr mode with one of the last great ctr rear projection sets from Mitsubishi. It's very hard to beat the black levels of a good ctr.;) I just wish that when we got it we had the room for a 73 but had to settle for a 55.

I didn't know an image could be moved up and down like that except for the usual adjustments.:cool:

At least I can put a speaker on top of mine.:p

http://i76.photobucket.com/albums/j7/maxwedge572/Audio/DSC04945copy.jpg

He appears to have either a Greyhawk or Firehawk. Both are grey screens for improved contrast and for viewing in less than black conditions. I think the greyhawk has a "gain" of 0.8 and the Firehawk has a gain of 1.3.

If the projector has a 4:3 native resolution, it can typicaly display the 16:9 at the top, middle, or bottom of the screen and is selectable. It's just a matter of whch pixels are switched on or off. Also they do upside down and backward for various mounting options.

Mine is LCOS with a 4:3 native resolution of 1,365 x 1,024. When I shoot HD format the resolution is 1,365 x 768. The standard is only 1,280 x 720, so even in HD format, my resolution is 13.75% higher than the HD standard.

maxwedge
03-09-2011, 08:11 PM
I guess I misunderstood. Those are screens and you use a projector? I've been looking over Stewart's web site.

S20RVERT
03-15-2011, 12:18 PM
I bought the Stewart Grayhawk (SNDQ90V) on Ebay for less than half retail price in 2003. I'm on my third ceiling mounted TV projector (Panasonic PT-AE-4000U-greatest for the price). I tried to buy some black Velux applique to convert the 4x3 to 16x9 from Stewart but they told me that they don't recommend installing it across the bottom.
The HDF center box is 18" deep so there is plenty of room for the 2450J. :)

toddalin
03-15-2011, 03:29 PM
I bought the Stewart Grayhawk (SNDQ90V) on Ebay for less than half retail price in 2003. I'm on my third ceiling mounted TV projector (Panasonic PT-AE-4000U-greatest for the price). I tried to buy some black Velux applique to convert the 4x3 to 16x9 from Stewart but they told me that they don't recommend installing it across the bottom.
The HDF center box is 18" deep so there is plenty of room for the 2450J. :)

Stewart can "cut down" the side frames, cut a section out of the screen, and add new snaps to make it into a 16:9 for you.

4343
03-15-2011, 04:54 PM
...

Mine is LCOS with a 4:3 native resolution of 1,365 x 1,024. When I shoot HD format the resolution is 1,365 x 768. The standard is only 1,280 x 720, so even in HD format, my resolution is 13.75% higher than the HD standard.

HD has a few "Standards". The top resolution is actually 1920X1080, called 1080I. (I for interlace.) A lot of projectors now do 1080P (P for progressive, i.e. no interlace) or higher, either by up-conversion or de-interlacing.

For film transfers 1080P is popular. I'm not going into all the different frame rates...:blink:

1280X720 is a "Native" progressive format, known as 720P.

toddalin
03-15-2011, 05:59 PM
HD has a few "Standards". The top resolution is actually 1920X1080, called 1080I. (I for interlace.) A lot of projectors now do 1080P (P for progressive, i.e. no interlace) or higher, either by up-conversion or de-interlacing.

For film transfers 1080P is popular. I'm not going into all the different frame rates...:blink:

1280X720 is a "Native" progressive format, known as 720P.

The "High Definition Standard" for broadcast television is 720P or 1080I. I, as many people, find that 1,280 x 720P from my Motorola cable box (upconverted to 1,365 x 768P by the projector) looks better, especially on action shots, than the 1,920 x 1080i, at least on my projector. While 1080P is now available on such things as BluRay or though deinterlacing/upconversion, the brodacast standards remain as they are.

bldozier
09-18-2017, 01:44 PM
Here are two more updates. I bought the fiberglas horn from a shop in Montreal and mated it to a 2450j and now have a 2397 on it. So far the 2397 sounds the best to my ear. I have no sound test equipment so I listen to one then change to another. Notice that I had to move the 077's when I exchanged the LE85/HL91's for 2450J/2380A's on my homemade S20R's built in 1974.


nice