Adding 2405H to my custom JBL system

[Beowulf57]

I'm in the process of adding 2405Hs to my system (pic below) and would appreciate comments on the decisions to be made.

I have Brociner-modified back-loaded folded corner horns (not identical: left has a D131 and right has a D130), LE85 compression drivers with HL91 horns and lenses; crossover is the LX5. Given the slightly lower sensitivity of the D131, the LX5 HF crossover level is set Low for the left channel and Mid for the right. This gives a fairly well matched balance between the two channels and the separate tube-regulated monoblock tube amps are adjusted to match channel levels.

I'll be using 3106 crossovers for the 2405s and plan to cascade the LX5 and the 3106.

At this point, my thought is to mount the 2405s in Minimus 7W (walnut) cases and locate the box horizontally on top of the LE85/HL91 enclosures which will provide a nice finished look and allow a bit of positional tweaking with respect to time delay between the LE85s and the 2405s.

Thoughts, suggestions?

Thanks,

Beowulf57

[Beowulf57]

Well, lots of views but no comments. I guess I should just assume that silence means consent...though there certainly won't be silence once I fire those 2405Hs up!

[Zilch]

Same suggestion I just made in another thread:

http://audioheritage.org/vbulletin/s...677#post209677

3106 alternative is shown, and the links indicate how to do 10 kHz, a better option, even, for 2405.

Biamp.

Behringer CX3400 or equivalent as the main crossver, $99 at Guitar Center or similar.

HL-91 is not a 500 Hz horn. You'll be able to find the optimum crossover frequency for your system by dialing a knob on the active.

Sonic Impact T-Amp II to run the mids and highs, if you don't have something already. $70 at Parts Express.

Tubes might be nice up top, too....

[Beowulf57]

Same suggestion I just made in another thread:

http://audioheritage.org/vbulletin/s...677#post209677

3106 alternative is shown, and the links indicate how to do 10 kHz, a better option, even, for 2405.

Biamp.

Behringer CX3400 or equivalent as the main crossver, $99 at Guitar Center or similar.

HL-91 is not a 500 Hz horn. You'll be able to find the optimum crossover frequency for your system by dialing a knob on the active.

Sonic Impact T-Amp II to run the mids and highs, if you don't have something already. $70 at Parts Express.

Tubes might be nice up top, too....

Thanks for the suggestions! I'll look into those crossovers.

Actually, the HL91 was used down to 500Hz with the LX5 crossover. This spec and configuration was provided in JBL's 1976 catalogue and was used in the S7 system.

[Zilch]

Actually, the HL91 was used down to 500Hz with the LX5 crossover. This spec and configuration was provided in JBL's 1976 catalogue and was used in the S7 system.

Yes, and it suc..., uhmm, did not do it well.

JBL subsequently used HL91 at 800 Hz in several products, but ultimately dubbed it a "1200 Hz" horn. Check later literature, and you'll see it was progressively derated.

At 800 Hz, even, the longer HL92 is preferred, as used in L300 and monitor products.

In 1976, JBL was still calling HL91 "500 Hz," but HL92, introduced around that time, "800 Hz."

http://www.lansingheritage.org/image...comp/page9.jpg

By 1979, HL91 was a "1200 Hz" horn:

http://www.lansingheritage.org/image...omp/page10.jpg

Horns generally have a reputation for sounding, well, "horny," and JBL's early [mis]application of HL91 played a role in that.

I'm saying using an active crossover will allow you to make an empirical determination of the optimum crossover frequency for your particular combination of components....

[Robh3606]

Here's what a 2307/H91 looks like on a baffle. It's with in a 5db window from 500hz till 10k. 500hz looks like the cutoff for the horn. You should never use a horn down to the cut-off point. Should try to use it an octave above so say aprox. 1K

Rob

[Beowulf57]

Thanks muchly for the advice...so how about I spring for a pair of N1200S to handle the LF to MF and raise the crossover point to 1200Hz and use them with my recently acquired 2405hs and 3106s? My system has sounded pretty good even using the 500Hz LX5 crossover, though I know it was never designed to be used with the D130.

P.S. Which horn is the 2307? I thought the HL91 was the consumer model of the 2391?

[Beowulf57]

Yes, and it suc..., uhmm, did not do it well.

JBL subsequently used HL91 at 800 Hz in several products, but ultimately dubbed it a "1200 Hz" horn. Check later literature, and you'll see it was progressively derated.

At 800 Hz, even, the longer HL92 is preferred, as used in L300 and monitor products.

In 1976, JBL was still calling HL91 "500 Hz," but HL92, introduced around that time, "800 Hz."

http://www.lansingheritage.org/image...comp/page9.jpg

By 1979, HL91 was a "1200 Hz" horn:

http://www.lansingheritage.org/image...omp/page10.jpg

Horns generally have a reputation for sounding, well, "horny," and JBL's early [mis]application of HL91 played a role in that.

I'm saying using an active crossover will allow you to make an empirical determination of the optimum crossover frequency for your particular combination of components....

Thanks Zilch! Very helpful. I'm afraid that biamping is a little out of reach in my present setup with two very large tube-regulated monoblock tube amps driving my corner horn systems from the room below my listening room. I don't have room to bring in more amps and I have worked on carefully voicing my present setup over the past 20 years. I agree with you that the "horny" sound can be an issue, though I have been able to tame it at least to a listenable point, running Class A push-pull directly heated triodes (6B4Gs).

What I'm thinking of now after considering your and others' advice is to add N1200 crossovers to raise the crossover point to 1200Hz and then use the 3106s to handle the existing LE85s and the 2405Hs that I'm adding to the system.

Sound okay?

I have two other concerns:

1. I could pick up a pair of N1200S crossovers, but don't know if these are modified from the N1200 model in some way I would need to consider.

2. My bass drivers are 16 ohm models and I believe the N1200/N1200S was designed for an 8 ohm load? Would this create a peak in the crossover region that I would have to compensate for, or will the 3-position level adjustment on the crossover allow me to compensate for this? I would note that I get very good bass response with the folded corner horns and have to shelve the LE85's level down at present.

Thanks for your help!

[4313B]

1. I could pick up a pair of N1200S crossovers, but don't know if these are modified from the N1200 model in some way I would need to consider.

Here is what Pro has. I'll try to scan my version and post it later today.

http://www.jblproservice.com/pdf/Net...tics/N1200.pdf

[Beowulf57]

Here is what Pro has. I'll try to scan my version and post it later today.

http://www.jblproservice.com/pdf/Net...tics/N1200.pdf

Thanks...and do you know if there are any differences with the N1200S? I'll be interested to se your scan.

[4313B]

Thanks...and do you know if there are any differences with the N1200S? I'll be interested to se your scan.

The N1200 and N1200S share the same schematic diagram. I'll try to remember to post it after I scan it later.

***

[Beowulf57]

Great! Thank you 4313B.

[Mr. Widget]

I have worked on carefully voicing my present setup over the past 20 years.

Then don't change the LX5s and go back to your initial idea of simply adding on the N8000s or 3106s and the 2405s and be done with it. If you pull the LX5s and start messing around it'll be another 20 years before you get it right again...

30 years ago I had a system that was nearly identical to yours and I improved it and improved it until there was no part of it still in my listening room. Pop in the tweeters and enjoy it. It has worked for you this long.


Widget

[Robh3606]

If you pull the LX5s and start messing around it'll be another 20 years before you get it right again...

Yes good point especially if you are happy with it.

Rob

[Chas]

30 years ago I had a system that was nearly identical to yours and I improved it and improved it until there was no part of it still in my listening room. Pop in the tweeters and enjoy it. It has worked for you this long.


Widget

Funny how that works, isn't it?