could it be the 2450's throat starts out at 1.5"?Originally Posted by 1audiohack
could it be the 2450's throat starts out at 1.5"?
No but I wouldn't hang my hat on it being the Neo. There are simply to many other variables.Is it irrational to wonder why?
Rob
"I could be arguing in my spare time"
Now put the diaphragm back in the 2441 and see if you get the same impedance curve that you got the first time...
I really didn't think I had.No but I wouldn't hang my hat on it being the Neo. There are simply to many other variables.
Rob
If we knew what the hell we were doing, we wouldn't call it research would we.
I did, I always A B A.
If we knew what the hell we were doing, we wouldn't call it research would we.
You put the diaphragms in the cores and adjust them to get the best sonic performance and then live with the resulting impedance curves. They are all going to vary. The primary focus is on sonic performance, there should be no objectionable resonances across the intended bandwidth. Once you get the drivers to that level then you start matching impedance curves if so desired. You'll need a bunch of drivers to get reasonably matched pairs. A micron shift in a diaphragm results in a different impedance curve as well as a potential resonance point.
The spec sheet for the 2452 is bogus.
The diameter measurement are also all wrong.
My 2452 is ~14cm in diameter and weigths less than 2.5kg
Sorry didn't mean to imply you had, 4313B has a very valid point in as they do change when installed as an example. Not getting into different horns and so on. Why don't you post what you are measuring and on what horn??I really didn't think I had.
Rob
"I could be arguing in my spare time"
confirmation from the engineering sheet:
http://www.audioheritage.org/vbullet...l=1#post215553
2kg it is
They managed to keep the flux density the same while deviding the weight by more than 2 !
I also like the fact that the wire plugs are directly fixed to the diaphragm: clever design, no more wire inside the back chamber, and a more direct connection!
They came back to the older design for the 476Be/476Mg though...
Maybe the longer copper sleeved pole piece and (larger magnet it implies) could not be installed in the new design? (as well as these new "tuned acoustic vents" under the surround)
When I first started this study my reasons for the original question was driven by one observation and a theoretical wonder.
First, one reads all the time that you often listen to these large format drivers at home driven at milliwatt levels and that any decent amp will be capable of making your ears bleed. I find this to be untrue. I don't drink and I'm not deaf, but,, when listening above background levels, a Crown D45 rated at 20 watts per channel into a 16 ohm load will clip easily, a D75 rated at 25 watts per channel into a 16 Ohm load will run them OK, barely if you get aggressive.
Proff. Marshal Leach Jr makes a good point in one of his papers about designing for maximum sensitivity rather than efficiency since power is so easy to come by these days. I haven't had the chance to measure any of the new horn / driver combinations but I do wonder what the combined operational impedances are for these. I need to get out the Pearson current monitor and O scope and see if I can figure out where all the power is going.
Second, I wondered if the difference in series L of the different impedances would make a notable difference in the very high frequencies. After measuring and listening for a couple of months now I decided it doesn't matter, none of these combinations I have here run high enough clean enough to make me not want to use a tweeter anyway. The TruExtent diaphragms are the best behaved all around I'm sure. The real issue now is that the Be's behave well enough upstairs that improper tweeter integration would be a spoiler where damn near any tweeter anywhere in the room would benefit some of the other combinations.
Looking into some of the newer super cool drivers that one can actually find measurements for like the 435Be and the 2435Be I found something I have never before noticed JBL do, they leave the fundamental and distortion curves in place on the sheet. I also noticed that all these measurements were done with TEF, the same system I use. I had measured the 435Al's and noted the divide between the fundamental and 2nd and 3rd harmonics as the cleanest driver I had yet measured, when I saw the JBL measurement set up was identical to mine and the graphs looked almost identical to what I was getting, I felt that at least I was looking at truly comparable data.
I want to thank all who shared, and if there is anything I might be able to add please ask. I think I have at least figured out what ranges to use the available materials in if the goal is minimum phase operation and best signal to noise. I know none of this is new, it's just some things aren't easily found in common literature and it's just plain fun to explore and learn.
All the best,
Barry.
If we knew what the hell we were doing, we wouldn't call it research would we.
If you are using a CD horn the HF roll off is likely quite considerable... the required compensation lowers the driver's practical sensitivity significantly.
Widget
This may be germaine, or maybe not, but I have a recollection that in the literature touting the large format Altec drivers--the 288 family--one of the arguments was that for the smaller 1" compression drivers the lower body mass gives rise to resonance issues in the lower frequencies.
Yes, and though the 4003 uses neodymium, it also weighs 30 lbs, about the same as a 288, 4001 or 2441.
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