HF driver comparison 23744 vs 34647

[Old Guy]

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


Again, good info.

Ron

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.

[Altec Best]

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

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)

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:


And here are the measurements for the 23744 on all three horns:


Here is the fram side x side compare on the 511 horn:

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.

[Altec Best]

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

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.....................

You guys mean these ?


HPIM2547 by Altec Best, on Flickr


HPIM2548 by Altec Best, on Flickr

[bowtie427ss]

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)

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..

[Altec Best]

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

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


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..

[Alien_Shore]

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)

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..

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:



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):



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...

[kinomat]

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?

[martyh45]

.... 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:

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.

[Old Guy]

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.

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?

[martyh45]

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?

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