2470 Franken drivers

[Ian Mackenzie]

http://www.jblpro.com/pub/obsolete/A...ns_Family1.pdf

The above link to Jbl data sheet

The curve above is on axis

In use the compromises are listener position in the vertical plane is critical hence my comment it’s not CD.

The curves don’t tell you everything. See comments below.

The 2405 is required with the 2307/2308 in practice.

In terms of a single driver application the 2344 bi radial horn wins

It does a lot of things well and it’s diy friendly.
But mass break of the diaphragm is the limiting factor ultimately.
(THD rises quickly above the mass break up frequency due to the boost of the CD EQ for the 2344)

But it works in spite of the facts.

In comparison setting up the passive voltage drive and adjustment of the Lpads for the 2307/2308 is critical for optimum performance. But done precisely the addition of the 2405 has the alluring subjective piston range quality.

[Ian Mackenzie]

Up late and saw the measurements. Awesome to see this. I'm surprised at the levels down to 500 hz, as I expected it to roll off at 700. Definitely not making it to 20K.

I haven't decided on the horn. I've been using some 2410's with Smith horns I built for my main system, with O76/2403 above. Crossovers are 3110 and 3105's. I believe the xover is around 5k to the 076. I like the combination. I'm thinking an active xover and time delay might improve it a bit.

I suppose, if I can't get above 16k with the 2470's, I may have add an ultra high driver. That would probably affect my choice of horn.

On a fun note, I saw these mini Smith horns that use a 2404, on the forum and almost wanted to build a couple! LOL They are not as efficient as a stock 2404.

http://www.audioheritage.org/vbullet...-Smith-Selsted

Maybe a 2344 would work. The 2307/8's look smooth between 500 and 10k. I've heard 2370's can be harsh. On the other hand I've wanted to play with some modifications to the Smith horns and they would be less expensive, at least to get things going.

If you have suggestions, I'm pretty open to looking at options.

On your post above l have not personally used the 2307 on anything other than a 4343-4344-4345 system so crossover lower is something you would need to access. You can passively EQ the 2307 for more HF extension like the Jbl 4320 monitor
http://www.jblpro.com/pub/obsolete/4320.pdf
http://www.audioheritage.org/vbullet...-3110a-network

The mini smith horn combination sounds like fun.

“I've heard 2370's can be harsh.” If you meant the 2370 that is more a pro pa horn.
The 2307 it needs to be integrated carefully and the newer Jbl networks used in the 4344-4344mk11 do that.
Also the older 2420 aluminium diaphragm was not ideal and it got a reputation of being live sounding in the 4343.

Adding a uhf driver is the next step.

I would play around with a few options and see what works for you.

[ivica]

http://www.jblpro.com/pub/obsolete/A...ns_Family1.pdf

The above link to Jbl data sheet

The curve above is on axis

In use the compromises are listener position in the vertical plane is critical hence my comment it’s not CD.

The curves don’t tell you everything. See comments below.

The 2405 is required with the 2307/2308 in practice.

In terms of a single driver application the 2344 bi radial horn wins

It does a lot of things well and it’s diy friendly.
But mass break of the diaphragm is the limiting factor ultimately.
(THD rises quickly above the mass break up frequency due to the boost of the CD EQ for the 2344)

But it works in spite of the facts.

In comparison setting up the passive voltage drive and adjustment of the Lpads for the 2307/2308 is critical for optimum performance. But done precisely the addition of the 2405 has the alluring subjective piston range quality.

Hi,
I have 2420 with Ti diaphragm with 2312 and 2308. Its HF response is quite usable, and dispersion in the room (7x4m) is OK, I have to say without any beaming at HF, but its LF response is not something that I have to say 'enjoyable', so I have exchange such combo with 2441 (Radian) with 2311 and 2308 (usable up to 10kHz), but I have to put 2405 as UHF driver. I have to say that 2405 is very nice driver, especially A-version with JBL 'blue' diaphragms.
I can imagine that with 2441 using JBL Be (476 diaphragm, or JBL AL-2441 diaphragm) can be properly EQ up to 15kHz.
2441&2311&2308 is much better , especially in lower frequency range then 2420 & 2312 &2308. I can imagine that 2420 (2470 motor) &2307&2308 is very much the same
I have no experience with 2344/A horn

regards
ivica

[Ian Mackenzie]

Hi Invica,

Can you post some measurements?

Below is a link to some solid Jbl data on directivity of the Jbl 4331 system and the 2307.

See a fig 4 , figure 12.

As you can see the vertical polar reduces to 45 degrees above 5000 hz then falls away.

The impact of this is the height of the horn/lens assembly must be exactly at ear height much like your head in a vice situation. Just something to be aware of.

I don’t mind sitting still in my favourite chair listening to an album with a glass of Knobs Creek Bourbon if it sounds good....Lol (the good stuff)

The whole EQ of a room and power response thing was the intent of the bi radial approach in studio situation with the document below.

I won’t elaborate on that because it’s a big topic. But it can invite challenges in the diy space like CD equalisation and room curves and it goes on and on.

Depending on your own preferences and scenario this may be relevant.

http://www.cieri.net/Documenti/JBL/D...)%20(1983).pdf

Below is the raw driver response (top) and the EQ with the schematic posted in the link previously.

The raw driver is 110 dB at 1 khertz and 105dB at 10 khertz.

The equalisation gives 100 dB at 1 khertz and 10 khertz.

The lower curve is flattened and extended a bit and the crossover slope.

That’s the difference between just trying it casually and setting up the driver to perform its best. You of course need something to do reliable measurement with.

Again my acquplas dusted diaphragm being a tad more mass may not extend as much as the factory 2425 Ti diaphragm.

You may be able to do this with your drive rack

[GoldcountryJim]

Ian,

What you are pointing out makes sense. With the correct EQ, the hi frequency range may be extended out, possibly and hopefully, to the frequency range I'm aiming for. This is for the driver output. The horn selection is the second part that determines what I'm actually going to hear and the sound field. In reading the articles, the 2344 may provide a single compression driver solution, as it was designed as a two-way component. The 2307/2308 has a higher directivity and will roll off so that I need a UHF driver. I also noticed that the vertical alignment of the woofer and 2344 driver are closer, which may help with phase alignment. The 2344 was designed as a studio monitor, if I'm reading this right, and that means near field. This is not good or bad for me, just part of the trade offs. Much to think about.

I also read JBL Technical Notes Vol.1, No.8 focusing in on the differences of the 2" diaphragms vs 4" diaphragms (2445/2446's). This was pretty enlightening on the second and third harmonic distortion differences between the two sizes. I've worked with the 2445's on 2380 horns and compared them, subjectively to my 2" diaphragm drivers. The 2445's do have a "clarity", but I always attributed it, incorrectly, to the 2380's rapid expansion/lower distortion. I'm left wondering if it will be inevitable that I upgrade to 2445/2446's on this project in the future.

I have to assume the rapid roll off on the plots is the mass break-point frequency and -6 db/octave drop above that point. This is really interesting to me, as I am targeting a flat response. What constitutes a "studio" monitor "flat" versus listening "flat" may be subjectively different. The Driverack could store both as presets, which would be pretty cool. I'm going to have to look at what the cut/boost limits are in the Driverack. I do a little home recording with Pro Tools and I could see a use for this.

The Driverack PX has one crossover built in, though its really supposed to be used for the sub/main feed. I could use this if I go with the 2344's and have something (two way) that I can implemented quickly and then build on later. Its actually a pretty robust xover, but I don't think it has the ability to set a delay/phase correction. I'll have to explore it.

I'm also still reading up on why 1" throat drivers are not as good on Smith horns. Enquiring minds want to know.

I've got to thank everyone for the input. My brain is full and I'm going to bed!

[Ian Mackenzie]

One question

What are you planning on using your system for?

Home theatre?

If you plan to start off and use the 2470 cores then 2344 is a good entry point and can operate down to 800 hz.

What you learn from that can be applied to something more ambitious

Another option is this horn for a 1 inch driver

Elsewhere on the forums this thr as investigates some horn
Horns including a 1 inch horn here

http://www.audioheritage.org/vbullet...50-vs-PT-F95HF

[GoldcountryJim]

Music listening and home theater will be the primary use. Mixing and reviewing recording tracks would be a pretty small part of it. My experience has been that studio monitors reveal more about the recording process and content, while listening systems tend to be more "musical". I suppose its about psycho acoustics and whether you perceive a true flat response as "natural".

With regard to the difference I'm hearing between 2" and 4" drivers, I should be cautious of ascribing sound differences to particular causes. There's a lot of factors that could be involved. I do hear a difference, but it could even be the different rooms that I'm hearing. I am trying to be more methodical in analyzing these things.

I'll read the linked material tonight. I remember seeing something about those horns in my readings.

Thanks!

[ivica]

Hi Ivica,
Can you post some measurements?
Below is a link to some solid Jbl data on directivity of the Jbl 4331 system and the 2307.
See a fig 4 , figure 12.
As you can see the vertical polar reduces to 45 degrees above 5000 hz then falls away.
The impact of this is the height of the horn/lens assembly must be exactly at ear height much like your head in a vice situation. Just something to be aware of.
I don’t mind sitting still in my favorite chair listening to an album with a glass of Knobs Creek Bourbon if it sounds good....Lol (the good stuff)
The whole EQ of a room and power response thing was the intent of the bi radial approach in studio situation with the document below.
I won’t elaborate on that because it’s a big topic. But it can invite challenges in the diy space like CD equalisation and room curves and it goes on and on.
Depending on your own preferences and scenario this may be relevant.

http://www.cieri.net/Documenti/JBL/D...)%20(1983).pdf

Below is the raw driver response (top) and the EQ with the schematic posted in the link previously.
The raw driver is 110 dB at 1 kH and 105dB at 10 kH.
The equalization gives 100 dB at 1 kH and 10 kH.
The lower curve is flattened and extended a bit and the crossover slope.

That’s the difference between just trying it casually and setting up the driver to perform its best. You of course need something to do reliable measurement with.
Again my acquplas dusted diaphragm being a tad more mass may not extend as much as the factory 2425 Ti diaphragm.
You may be able to do this with your drive rack

Hi Ian,

You can see some of my measurements in the:
http://www.audioheritage.org/vbullet...with-2311-Horn

And if we are talking about the 2308 dispersion ( with 2307, 2311, 2312 ) JBL horns it is evident that its horizontal dispersion is respectable, reaching +/-45 deg ( I think just a few of known horns have such good results), but its vertical dispersion over 10kHz is almost less then +/-10deg (that is not so huge results,and is much LESS the 2405/2), but it has to be emphasized that from the seated position to standing position with the distance of about 3m from the speaker totally changed angle in the vertical plane would be about 15deg (that would correspond to +/-7.5deg), so even i such situation (without 2405) 2308 combo can be acceptable solution ( such as 4331 )

[GoldcountryJim]

Ian,

The PT's are an option. They certainly are easy on the pocketbook! I think the stx825 horn (JBL part #5006815) at Reconing Speakers is the 1" horn.

I checked out Jammin Jersey and he has some 2344's. It was difficult to know the condition.

Its a little harder to find 2307's.

I came across JBL/Selenium, which has some horns. Some are plastic, some aluminum. There's some discussion on the forum of the HL 14-50 as being similar to the 2311. The JBL/Selenium HL 14-25 is a 1" conical horn that may be based on the 2307. However, its ABS plastic or similar material. I didn't find much information on them other than you can get them for about $6. LOL

[ivica]

Ian,

The PT's are an option. They certainly are easy on the pocketbook! I think the stx825 horn (JBL part #5006815) at Reconing Speakers is the 1" horn.

I checked out Jammin Jersey and he has some 2344's. It was difficult to know the condition.

Its a little harder to find 2307's.

I came across JBL/Selenium, which has some horns. Some are plastic, some aluminum. There's some discussion on the forum of the HL 14-50 as being similar to the 2311. The JBL/Selenium HL 14-25 is a 1" conical horn that may be based on the 2307. However, its ABS plastic or similar material. I didn't find much information on them other than you can get them for about $6. LOL

HI JIm,

I think that for 1" driver you have to use
http://reconingspeakers.com/product/...ns-338800-001/

horn, as STX825 / 815 horns are 1.5" horn throat.

Mentioned HL-14-50 is 2" throat horn, but a kind of 2308 like lenses have to be applied to prevent beaming. The same would be for HL 14-25 as i it is 1" throat horn.....

regards
ivica

[Ian Mackenzie]

In terms the practical application of these various horns my recommendation is look at a Jbl design and see how Jbl used these horn component. For example have a look at the two way systems such as the 4320/4325 and the 4331 and the 4430. In particular the crossover schematics and the design specifications.

You can use the Drive rack to Biamp the crossover function and the passive EQ with the crossover to shape the horn response. This way you have the flexibility of Biamping and be close to on target with the EQ based on jbls measurement and engineering. Bi amping will allow matching the sensitivity of the 2226 woofer to the horn. I would not worry about the appropriateness of the 2226 with a particular horn at this early stage as your focus is on the horn.

That way you can audition the options and make a judgment call with the assurance you set up the horns close to optimum. Attempting to finalise a design on paper without auditioning some options first removes your auditorypreferences from the process. You also will miss out on some of the diy fun. Trust your own ears and take it step by step from there in terms of your final horn selection. It’s okay to get some opinions here on the forums but let your own ears do the listening. This isn’t about telling you how to suck eggs just stuff to be aware of in working out your project as you progress.

A short story:
For example way back l compared the 2397 horn, the 2344 and the 2307+2405 using Jbl crossover schematics and some measurements. I then narrowed it down to the 2344 and the 2307+2405. This took twelve months or more of listening.

Earlier on l used the 2397 (1 inch driver crossed over at 800 hertz on its own with an Altec woofer. I then added the 2405 and optimised the crossover with IMP measurements. That validated my design. I eventually sold the Altec woofers and used those proceeds to buy two Jbl 2245 and two Audax eight inch paper mid cones. I also used an online measurement software called Airr.

Using Audax crossover recommendations and measurements l had a response +-5 dB and it sounded smooth
I Biamp the woofers with a Crown two way active crossover with a Clair Bros Phase Linear 700B and a diy Pass Labs Aleph 5.

I then bought two Jbl 2122 10 inch mid cones at a tent sale and swapped out the Audax drivers.

At that point l started comparing the 2344 using the Jbl 3134 crossover with the 2397+2405.

I then acquired the 2307/2308. At that point l did not have a schematic for the 2122 transition to the 2307 so l email Jbl and to my surprise l got an email from Greg Timbers with the engineering notes for the Jbl 4345 design. With some collaboration an equivalent network was devised as the split core inductors used in the Jbl network were nla. That was back in 1998 -2003 when the internet was really primitive. Sometimes it pays to ask and l got lucky.

Adjustment of the Lpads for the 2307/2308 and the 2405 is tricky and l came up with an approach using an analogue Tandy spl meter and test tones by simply adjusting the Lpad to full then turning back the Lpad -3 db on the Meter on the Mid and -4 dB on the horn and 2405 to get the levels right.

So with further listening l started to hone in on my preferences. The Lpad adjustments on the Jbl 3134 are really cool btw. I also messed with class A amplifiers and crossover parts and found (then)class A amplifiers and Hovland capacitors had a significant influence on my impressions of the 2344 and 2307/2408+2308 compared to class ab amplifiers and Mylar capacitors. I still hold those views and today you can read about charge coupled crossover networks which is a really clever way of improving the performance of capacitors in these networks.

Comparing the 2344 and the 2307/2308 set up optimally it wasn’t chalk and cheese and it came down to what l thought was more accurate, my music preferences and that way my room acoustics interacted. I also weighed up the visual aspects of the system.

Back to the advice part in the diy loudspeaker space sometimes the horns are not setup correctly and the judgement call falls back on sub optimal application of the horn rather than the characteristics of the horns. In the absence of a measurement tool and Jbl crossover recommendations to validate the design any opinions are only opinions.

[GoldcountryJim]

Ian,

Appreciate you sharing your experiences. Validates that this is a journey not just a destination.

Today, I really have been thinking how the purpose of the system should dictate more of the design than I'm admitting. Do I need near field or long throw? And, will it always be in the same room? My living room is 22' by 32' with wood floors, but the man-cave is smaller. Plenty of time to refine this.

Totally agree that in the end, its about what sounds good to the listener. But, it should be guided by the hardware specs and design principles. And a bit of truth should be applied: never spend money on equipment that doesn't give you an audible difference that you can appreciate. I am at a point where I can hear deficiencies in my main system and this project is my effort to improve on that. I like the smith horns because they don't have the beaming or ringing that pro sound reinforcement can have or metal ring like Altec 811's. I can hear that! I'm now seeing the trade off in it.

I think my original question has been well answered: the 2470 will be usable and could have the characteristics that I'm looking for, depending on the purpose, horn, and a few other components that will impact what I hear. This is good. The discussion is rewarding and pushes my knowledge of why the systems behave as they do.

Somewhere on the forum there's pictures of wood 2308 lens. Appearance wise, they're pretty cool. Perhaps. . .

Off topic, I had need to contact a JBL authorized recone service and found out Orange County Speaker is closed, as is one in the bay area. Seems like there are fewer of them these days. Fortunately, I did not need a recone.

[Ian Mackenzie]

Near field is at the end of a mixing desk. It’s not that.

Long field is like pa to reach the back of a hall. It’s not that either

It must be “medium” throw.

If you imagine an equilateral triangle and ideally your speakers are say 3 or 4 feet from the side walls so they will be 14 feet apart. So you will be around 14 or so feet from each loudspeaker (ideally subject to waf)

Maybe put your 2226 in project boxes and sit your horns on top while your trying out ideas.

Btw l have a similar scenario in terms of room size. What to do? The big room sounds awesome!
The jury is still out in the big room....Lol. The pool’s done so l am told l can do anything as long as it looks good.

[GoldcountryJim]

"Short throw." I've seen that in some JBL literature.

2307's are difficult to find, but I'm more curious about them than a week ago. Experiencing this type of horn before spending $$$ seems like a good idea. I've decided to order a couple Selenium HL 14-25's (its $5.99 at Parts Express) and experiment. There's a bolt on adapter for $3. The HL14-25 more closely matches the 2312 and I wouldn't expect it to be identical to the JBL in performance. The Selenium does appear different at the mouth. Depending on the results, more $$$ could be spent for the real deal.

https://www.parts-express.com/pedocs...spec-sheet.pdf

Not sure what I'll do to model the lens.

Haven't seen a Phase Linear 700 in some time! Nice amp.

Ian and Ivica, I appreciate your time and knowledge.

[ivica]

"Short throw." I've seen that in some JBL literature.

2307's are difficult to find, but I'm more curious about them than a week ago. Experiencing this type of horn before spending $$$ seems like a good idea. I've decided to order a couple Selenium HL 14-25's (its $5.99 at Parts Express) and experiment. There's a bolt on adapter for $3. The HL14-25 more closely matches the 2312 and I wouldn't expect it to be identical to the JBL in performance. The Selenium does appear different at the mouth. Depending on the results, more $$$ could be spent for the real deal.

https://www.parts-express.com/pedocs...spec-sheet.pdf

Not sure what I'll do to model the lens.

Haven't seen a Phase Linear 700 in some time! Nice amp.

Ian and Ivica, I appreciate your time and knowledge.

Hi Jim,

But using HL-14-25 WITHOUT 2308 like lenses, would be a great mistake, either in the on axis response or off-axis response.
You can make yourself lenses like 2308 from cardboard keeping 'inter-plates' distance round 1/4", angled round 40degs, and the shape of the "V" curve can be found here on the forum, searching "2308 lenses".


http://www.audioheritage.org/vbullet...l=1#post296009

regards
ivica