JBL Speaker Project

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Well Guys

I have not been in this part of the diy forum so here is my speaker project.
Actually there's quite a long journey behind this project.

I'm sure you'll find this interesting so here's the short version.

I originally moved away from bookself RCF monitors similar to JBL 4312's about 5-6 years when I heard my brothers 4343 diy which I built some 20 years ago... the temptation to enter the realm of big boxes again was too much.

So I acquired by stealth some Altec 515B bass bins and then quickly soon after added a JBL 2420 +2397 Smith horn for a nice 60's 2 way. It was very open and sensitive but lacked top end. I then scored a pair of original JBL Slots (which Robert now has) from a member of the Melbourne Audio Club who ran a local speaker building course at a tech college. He helped with the crossover using IMP with MLSSA upgrade.

This was close to a 4333A but I wanted better mids and more extended bass./ The 515B was limited with very low QTS of 0.17 and crazy Vas, so I put up with doctored QTS using 10 ohm series resistors for a time. I then added the Audax 210T 8" mid paper come which have served me very well and at that time I elected to build the current boxes as you see them here.

The front skin is 2" MDF with all other sides 1", very heavy 2x4 bracing and dual damping using plastic carpet underlay for surface standing waves and then 2" fibre glass.The 3 x 4" ports are mount in the side at the woofer level.

At that time I then spotted a single 2245 and promptly loaded it with my favourite honey moon tool to increase the hole from 15 to 18". So I had a 4340 4 way with 18" cones using a passive crossover in what looked like large stage monitors with the 2397 flares standing proud of the from baffles about 15 "

I then biamped this rig with a Phase Linear 400 +700 Clair Bros, this mother was seriously dynamic and the ultimate rocker/roller. From here I sort to refine the crossover ended up considering scrapping the 2397 and slot in favour of the now popular 2344 with titanium 2420. Through hell and fire a tried to make a passive eq crossover and eventually got the courage to email JBL for the 4435 +4345 crossover.

They (JBL) also relented with the 2245 tuning which is 28 hz in 9.5 cuft with 0.2 ohm in the 5.4 mh open E iron core choke which weighs 10lb. The total QTS is something like 0.285 and the 2245 is quite critical for tight tuning.

From that point I have never looked back and have a 3+-db window from 200 - 18,000 at 96dba with -3dba @32 hertz. Finally I have the 2122's thanks to Robert Hamel.

The 2344 is amazingly smooth for a single driver horn from 1 - 18K, the imaging is spot on and there is zero time displacement so the highs are silky and accurate with the modest but wonderful Aleph 5 60+60 Class A amp.

The finish is Dulux with decorator 2/mix which is applied with a sea sponge. Its quite nice and much easier than veneer. As you can see I like to play but the real fun starts here where we can all share information and assist with our projects.

Happy listening everyone.

regards
 

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G'day Macka

Though I am currently listening to Mangers I know what you are talking of when you are raving about the 2344 horn. I still own two boxes using 2344 horns (using a 2426 driver which is unfortunately one with a ferrite magnet only) and 12" 2206 (boasting a glass-fibre reinforced paper cone !).

I remember when I received the drivers I just had to try these horns out immediately by directly connecting them to an amplifier output (at a veeeeeeeery low volume of course !) and listen to a beautiful female voice (Khadja Nîn) - and I was shocked ! I didn't expect much, since I know that these have a lower cutoff frequency higher than a telephone and quite an early response drop at their higher end (they are of the constant directivity type which calls for equalization) but this voice sounded smooth and silky (very different to the honky sound that I was used to hear from other horns when tested that way)!

Though these speakers are not as accurate as the Mangers are, I still like to listen to these once in a while just because of pure fun. One of the great advantages of professional speakers used for domestic audio is the fact that they sound very effortless when driven at reasonable listenig volumes.

Regards
Charles

P.S. Your speaker looks cool ! :cool:
 
Ex-Moderator
Joined 2002
Hi Macka,

I too have been working a JBL speaker system for a long time. Currently I'm closer to the 4343 setup in a tri-amp, sat/aub arrangement, with dual 10" mid-bass per side. Instead of switching to the 2344, I went through a tweeking process on the 2312 horn/lens. I have a slight peak around 3k but it's not bad and it sounds very smooth. I'm still in the process of shaking out the bugs in the dual mid-bass. It may take a while, but after 25+ years, who's in a hurry. I have also replaced the 12" 124A's I was using in the subs with 15" TAD 1601a's. They are a ton more efficient and sound much tighter.

Have Fun.
Rodd Yamashita
 

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Ex-Moderator
Joined 2002
Macka,

The Aleph is what brought me to this forum in the first place. I've tried nearly 20 different amps on the horns over the years. A friend I met on the Audio Aslyum had a large JBL system down in Indy. I stopped to visit him on a business trip and he had an Aleph 3 just sitting as the backup for his 300B tube amps. He got me going on the Aleph. I was going to build the A40, but the consensus is that the Aleph has more of the "tube" character to its sound. The plan is to build an Aleph 3/5 once I have all the parts. I am currently using a NAD 2600 for the subs, a Bryston 4Bst for the mid-basses, and a NAD 2100 for the horns. I have a Heathkit AD 1702 electronic xover for the subs and a Nakamichi EC100 electronic xover for the horns. I too am very interested in Mr. Pass' new xover.

What Mid-Basses are you using now? What would you use if you had your choice?

Below is a pic of my friend's speakers. He has a 2344 inside the 2360 with 2445 drivers. That's sitting on dual 2220's 12" mid-basses. In the back corners of the room are the subs with 4 - 2235 15" woofers in each sub!

Rodd Yamashita
 

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Good God,


Talk about horn loaded head phones!!! just joking.

Rodd, Your current mid bass system looks fine.

Mid bass? It depend what you mean by that, some refer to 250 - 1000 hz, others 100 - 500 hz.

It also dpends on whether run the subs as just subs say to 80 hz or higher say 150hz.

If this is the case (80hz) then a 12 " running up to 400 would be good, then say an 8 " or 10" to 1200 and then cut over to the 2420.

My mid bass is a 2122 JBL I got from the JBL tent sale, it operates from 280 - 1000 hz and is in a sealed box.

The 2123 is the current model, suggest you look at the tent sale if interested.

regards

macka

:eek:
 
Ex-Moderator
Joined 2002
Macka,

Are you happy with the 2122's? How does their sound blend with the horn?

I considered 2123's from the local DJ's shop but it was going to cost me $800. I'll have to check into the tent JBL sale. I had 2 LE10A's and I bought a pair of Lancers77's for $125 off eBay. The mid boxes in the picture are the Lancer boxes reworked and covers with 1/4" oak ply. The baffles are 1-1/2" thick.

I alway thought my LE 10A's (I used to run one per side) were not dynamic enough. That's why I'm trying duals with the Bryston. I haven't got the levels quite set yet, but the drums do have more impact then they did with the single. I currently have them crossing over to the subs at about 112Hz, and running up the to the horns at 1200Hz. I don't think I want to use my horns much below 1200Hz. I believe each speaker needs a full octave beyond crossover.

Rodd Yamashita
 
I see your point now Rodd,

The 10A's were really a woofer/mid for small bokkshelf designs in 2/3 way. They are not a specialised device like your Tad or the 2122.

This is what I would do.

Phase one, clean up the mid's and improve dyamics.

The blend with the 2122 / 2344 is perfect. You will be in heaven, the 10" mid are why the big JBL monitor sound so great, a very light cone, 3" coil and 10 lb magnet!~!

So , based on available drivers in the market and your scene you will see there are some JBL 2123's in the tent sale.

Grab a pair of them as they a the next generation 2122, this batch is 16 ohms but that does not matter, they still clock high 90's (97dba @1 wattsensitivity), or you could buy 4 @ only $130.oo each.

The 2123 will run up to 3K but suggest you stick with 1200 for the best blend. I am open the PDF for the 2123 as we speak, it look good from here.

A quick simulation on JBL Bass Box suggest 2 boxes for the 2123.

Sealed 10 litres with normal fill, an f3 of 220 hz, or
(This option is for a 4 way+ Tad sub)

Vented 10 litres with an Fb of 90 hz give F3 115 hz, the vent should be 7.6 x 7.6 cm square and 12.4 cm long.

This will get you started, then later on Phase 2 up the upgrade could be to add a nice 12" mid bass JBL or Tad to run from 80 up to 300 hz.

Please let me know what you decide on.

There is a small 2nd hand out fit near JBL that specialises in JBL vintage parts, I will try and find it for you.

regards

macka
 
Hi Rodd

I was wondering about WAF of your friend's system :) ;) !

But the 2344 inside the 2360 horn looks rather smallish to me because it should have almost half the heigth and width of the 2360. Could it be that it isn't a 2344 (being 12" high and wide)but it's smaller brother that was used in the 4425 monitor ?

Regards

Charles
 
Ex-Moderator
Joined 2002
Hi Charles,

You're right, those are the 2404's. I believe the flange is about 6"X6" and they bottom out at about 3kHz. The WAF (P.C. term, SAF) in that home is not an issue. The wife is fine with the system, as far as I can tell (remaining P.C.).;) The living/listening room is to die for. 20ft across the back (the wall in the picture) and over 30ft deep with a vaulted ceiling. Opposite the back wall, the room opens to the large dining room down, and a full width loft up.

Macka,

One of the design parameters I've tried to keep is to not cross over in the fundamental voice range (~200Hz to ~1000Hz). That's not carved in stone for me, it's just something that made sense so I stuck with it.

I thought about 2 different drivers driven from the same amp. Maybe a 12" and a 2122, but I'd have to roll off the 12" somewhere around the baffle step range, and it would have to be about 3db to 6db more efficient the the 2122. That way I take care of the baffle step issue. My sats are about 14" wide so theoretically I should get an on axis boost around the 300-400Hz range.

I wonder what would be the result if the 12" were an 8ohm speaker and then I got a 16ohm 2123J and run them both in parallel from the same amp?

What do you think?
Rodd Yamashita
 
Ex-Moderator
Joined 2002
Macka,

I've got BassBox Pro from HT Audio. It allows me the to look at the response of multiple drivers on the same graph. I can see the individual curves for each driver plotted in the same axis. There are separate graphs for Normalized Response, Actual Level with XWatts input, Impedence, Phase, Group Delay, etc. The group delays are also line on line. I can't get a summed response yet, but I'm working on it.

The point is that when I ran a LE10A and A 2123J, the phase differential is about 70 degrees at 300Hz and increase very slightly to 75 degrees at 500Hz and drop to 30 degrees by 1kHz. Also at 100Hz the phase curves are line on line. I have a 2mH inductor in series with the LE10A and a 1mH inductor in series with the 2123J. I also include the inductance and DC resistance of each driver in parallel with the other driver.

I'll try to find a 12" to replace the LE10A and run it again.

Thanks for the help.
Rodd Yamashita
 
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