HF driver comparison 23744 vs 34647

I finally landed some nice 802-8G HF compression drivers with the "lite" diaphragms part # 23744, so I thought I would do some measurements and see if there is a quantifiable difference between the lite frams and the replacement frams that came along shortly after (part # 34647).

To conduct the tests, I wanted to control as much variability as possible, so I used the same 802-8G driver for all measurements, and swapped out the frams only. I took measurements from exactly the same positions, using the same amp, same levels, etc. I measured using three different horns that I have on hand: the MR931-12, 811, and 511.

Here's the 802-8G I used. Great condition, very clean:
http://imageshack.us/a/img94/2340/img0449hd.jpg

http://imageshack.us/a/img195/6338/img0450jm.jpg

And the two frams used for all the tests. The 23744 lite:
http://imageshack.us/a/img692/3216/img0451fw.jpg

And the 34647 (slightly dimpled):
http://imageshack.us/a/img442/1529/img0452gf.jpg

Here are the measurements for the 34647 fram on all three horns:
http://imageshack.us/a/img593/5812/8028g34647.png

And here are the measurements for the 23744 on all three horns:
http://imageshack.us/a/img688/5825/8028g23744.png

Here is the fram side x side compare on the 511 horn:
http://imageshack.us/a/img577/8572/8028gframcompare.png

Now, put one of each diaphragm in a separate driver and horn combo and play some mono music though them at the same time and see if you can hear a difference.

Good info, thanks. The light fram is essentially better everywhere.

So Volvo, what is your point?
Just curious.

Ron

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...................see if there is a quantifiable difference

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Pretty difficult to do since used diaphragms don't have odometers or hour meters.

Certainly a difference is shown in your measurements(and that's not unexpected). But, there are no baseline or control samples to conclusively prove that the measured differences are the result of and limited to their manufacturing or material differences.

For the data to be considered empirical, you would need to start with multiple NEW diaphragms of each type under strict control, not diaphragms with unknown hours and magnitudes of use.

Just my .02 y'all understand.....................

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Originally Posted by RonSSS

Good info, thanks. The light fram is essentially better everywhere.

Ron

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If "better" is interchangeable with "more efficient" then yes. To me everywhere would include high volume tests, where the light fram will likely distort first. I does seem to have slightly better 9-12kHz response. I would also expect better transients, as a lighter mass accelerates quicker.

I suspect in an A/B on delicate tracks, like acoustic stuff, the light fram would be readily identifiable.

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Originally Posted by bowtie427ss

For the data to be considered empirical, you would need to start with multiple NEW diaphragms of each type under strict control, not diaphragms with unknown hours and magnitudes of use.

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no arguments, sir. I make no claims, simply wanted to get some data out there that was collected in a reasonably controlled manner. I also measured the same frams in a 908-8A driver, and also used a new, modern driver/fram in all three horns as a comparison point. I can post some of that data if there is any interest.

Another thing that I can do is try the same tests with the other two frams of the same part#, to see if there is any meaningful variations from fram-to-fram. But yes, it would be great to get new frams to use in this testing - maybe John would mail me his :D

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Originally Posted by Alien_Shore

no arguments, sir. I make no claims, simply wanted to get some data out there that was collected in a reasonably controlled manner. I also measured the same frams in a 908-8A driver, and also used a new, modern driver/fram in all three horns as a comparison point. I can post some of that data if there is any interest.

Another thing that I can do is try the same tests with the other two frams of the same part#, to see if there is any meaningful variations from fram-to-fram. But yes, it would be great to get new frams to use in this testing - maybe John would mail me his :D

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Don't get me wrong. I've heard enough of both that your measurements pretty closely show what i believe i hear, and i think there will be a consensus among those who have also had the opportunity to listen to multiples of both. Now if we could just get the fellas to pony up and break the seal on a couple of their NOS 23744's and send them to you for evaluation..................... ;)

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Originally Posted by RonSSS

So Volvo, what is your point?
Just curious.Ron

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I just meant that it all looks great on graph paper, but how do they sound side by side. Throw in a symbiotic and a pascalite for a total comparison. :)

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Originally Posted by VolvoHeretic

I just meant that it all looks great on graph paper, but how do they sound side by side. Throw in a symbiotic and a pascalite for a total comparison. :)

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Interesting that you bring this up. I am reminded everytime a measurement thread pops up, that frequency response measurements while useful and informative, don't tell the whole acoustic story of how something "sounds". You cannot measure "timbre" for instance.

Volvo, thanks.

When I said better, look at the graphs, it is better. Also smoother. The interesting thing is the bump at approx 12khz. They will sound extended.

I've done similar measurements, but it's been a long time ago. I saw similar things.

As far as swaping frams out and listening, I never had enough drivers to do that quickly. I know my brain will forgrt in the hour or so it takes to carefully swap the fram.....so not real sure I'd immediately go "WOW"...that one is better.

Again, good info.

Ron

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Originally Posted by RonSSS

When I said better, look at the graphs, it is better. Also smoother.


Again, good info.

Ron

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Mostly in agreement, just not sure they are any better. Better graphs, as said elsewhere here, do not always translate to reality. They certainly are more fragile.

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Originally Posted by bowtie427ss

Pretty difficult to do since used diaphragms don't have odometers or hour meters.

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But there's something that should be said for what looks like a 35+ year old diaphragm that is still outperforming a newer one on paper. (Flatter Response)

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Originally Posted by Alien_Shore

I finally landed some nice 802-8G HF compression drivers with the "lite" diaphragms part # 23744, so I thought I would do some measurements and see if there is a quantifiable difference between the lite frams and the replacement frams that came along shortly after (part # 34647).

To conduct the tests, I wanted to control as much variability as possible, so I used the same 802-8G driver for all measurements, and swapped out the frams only. I took measurements from exactly the same positions, using the same amp, same levels, etc. I measured using three different horns that I have on hand: the MR931-12, 811, and 511.

Here are the measurements for the 34647 fram on all three horns:
http://www.hostboard.com/forums/

And here are the measurements for the 23744 on all three horns:
http://www.hostboard.com/forums/

Here is the fram side x side compare on the 511 horn:
http://www.hostboard.com/forums/

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Nice Job Mike ! I've been meaning to do this myself and then 20 other things seem to take priority "Such as Life"...

2 things stand out to me.That is backed up by what I hear.. So there is a lot of validity to those measurements IMHO. First is the more extended and smoother response of the 23744 which is (My Favorite) small format diaphragm.. And the response on the MR-931 horn, which I never liked much.

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Originally Posted by Alien_Shore

Another thing that I can do is try the same tests with the other two frams of the same part#, to see if there is any meaningful variations from fram-to-fram. But yes, it would be great to get new frams to use in this testing - maybe John would mail me his :D

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Originally Posted by bowtie427ss

Now if we could just get the fellas to pony up and break the seal on a couple of their NOS 23744's and send them to you for evaluation..................... ;)

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You guys mean these ? :biggrin2:

http://www.hostboard.com/forums/hbmc...2013/03/22.jpg
HPIM2547 by Altec Best, on Flickr

http://www.hostboard.com/forums/hbmc...2013/03/23.jpg
HPIM2548 by Altec Best, on Flickr

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But there's something that should be said for what looks like a 35+ year old diaphragm that is still outperforming a newer one on paper. (Flatter Response)

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OK, let's toss a BMS 4550 ND into the pot. It easily outperforms any small format Altec driver in terms of frequency response, as well as sensitivity.

Remember the group buys of the BMS drivers, and the circle of wagons singing the praises of the measured BMS superiority at one of our other favorite audio forums, when small masses were swapping out their small format Altecs for the BMS?

Now, have you noticed over time that several individuals have gone back to their 802's and 902's ultimately preferring them over the BMS? There have also been several pairs of 4550's offered for sale in the forum marketplaces.

Two main points to ponder here: a) the "better measuring" transducer is not always perceived as the "better sounding" one, and b) a difference in frequency response between two different transducers is likely only one of several differences in sonic signature.

It's not just brand loyalty that drives the Altec enthusiast, the fact they sound so good has a lot to do with it..:D

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Originally Posted by bowtie427ss

OK, let's toss a BMS 4550 ND into the pot.

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That's not what this thread is about.. Altec diaphragms 23744 vs. 34647's :wink2: :biggrin2:


Exactly ! I will take an Altec driver any day of the week over any BMS driver... You also have to remember that Altec drivers haven't had any significant development except (GPA's) in a longtime and the BMS's are fairly new in comparison.. And the Altec's still sound sooo sweet to these ears..

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Originally Posted by Altec Best

But there's something that should be said for what looks like a 35+ year old diaphragm that is still outperforming a newer one on paper. (Flatter Response)

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Originally Posted by bowtie427ss

Two main points to ponder here: a) the "better measuring" transducer is not always perceived as the "better sounding" one, and b) a difference in frequency response between two different transducers is likely only one of several differences in sonic signature.It's not just brand loyalty that drives the Altec enthusiast, the fact they sound so good has a lot to do with it..:D

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So here are a couple of other measurements that are interesting, given your comments. The first is that same 34647 fram in a 908 ferrite driver, compared the 802-8G driver, mounted in the big 511B horn, again measured with all other conditions the same:

http://imageshack.us/a/img838/8475/908802compare.png

And here is the 802-8G with the lite fram compared to a brand new B&C DE250-8 driver (with its own new stock polyimide fram):

http://imageshack.us/a/img96/1/802bccompare.png

One thing to note is that the 23744 lite fram would not play well at all in the 908 driver body. One fram had fairly severe distortion 500-1100 Hz, and the other fram had less distortion but very low output 500-1100 Hz or so. I tried both since I was curious if it was either particular to the one fram, or if perhaps I had mounted it improperly. These tests of course did require me to employ the fram conversion kit, to put the newer 34647 fram into the 802 driver, and the older fram into the newer 908 driver. It was quick and easy, but you need to have that tiny star wrench to remove the binding posts...

Great tests,with results to see.I would use as a reference. The 511 shows good performance,maybe the acoustic loading of a 500Hz horn is a possible factor.It would be good to show your test at different levels, also I wonder what effect a loading cap would show with each fram. Another thought: 2 frams,same part # How would the one about 3 yrs.(let's say in cinema,arena,school) show against the other new from stock?

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Originally Posted by Alien_Shore

.... The first is that same 34647 fram in a 908 ferrite driver, compared the 802-8G driver, mounted in the big 511B horn, again measured with all other conditions the same:

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I swapped some light frams into 908 and the results were not good. I didn't measure it but it didn't take long to figure out that the sound with the pascalites was much better.

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Originally Posted by martyh45

I swapped some light frams into 908 and the results were not good. I didn't measure it but it didn't take long to figure out that the sound with the pascalites was much better.

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My guess is they sounded "thin"? The 900 series bandwidth is shifted upwards, so likely the lighter mass resulted in a weaker upper voice range?

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Originally Posted by Old Guy

My guess is they sounded "thin"? The 900 series bandwidth is shifted upwards, so likely the lighter mass resulted in a weaker upper voice range?

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Yep, thin and harsh. Not a good mix at all.