Thank you, Tom. My assumptions regarding what Storm is listening to may be incorrect. I'm not seeing the rising midrange characterisic of early studio monitors there.Originally Posted by Tom Brennan
I hope more members will have curves to post for comparison, now.
Here's the CBS M19 curve blown up:
I examined that curve earlier today when you posted the link... I question its accuracy. How could the on axis and front hemispheric responses be so similar deviating primarily at a few points below 2.5KHz? That just doesn't make any sense. The 811 and 511 horns are radial exponential horns that tend to narrow the high frequency dispersion as you go up in frequency. The plots as represented must be erroneous or they have a pretty unusual method for averaging a curve.
Widget
The omni-directional (4-pi?) is certainly falling off above 5 kHz.
I agree that the axial and hemispheric (2-pi?) should not be the same.
These are not 180° horns.
I'm not ready to call it "wrong," but it certainly doesn't make sense.... :dont-know
I have Radian diaphragms on 802-8gs. How exact of measurements do you need? I have a TacT I could use to measure them but I'm not a professional, so I don't know how scientific the results would be.
Back in college, my physics instructor always told us to try to solve the problem in our heads and "know" the answer before plugging the numbers into our calculators. (computers were not so readily available back then) If you know what you're expecting you can be confident when the answer agrees with you.... if your calculation is an order of magnitude off or the phase has changed etc., then you need to rethink the problem. This plot can't be correct as stated.
Widget
Hi, Shane.
At this point, I believe it's all of interest. I'm sure you know the parameters: on axis, 0.5 - 2m away. It's just the general response we're looking at, so it doesn't have to be "calibrated." Pics of an RTA screen'd be welcome, too. Results by different methods are valuable if only for illustrating that difference alone.
I'm certainly not a professional, either. I've been dubbed a "hack" here, in fact, but that's never kept me from trying my marginally competent best....
Storm,
I like the look of your new Altecs
Bold of you to post about them here.
May I suggest if they sound good to your ears with your equipment then that is all that matters.
Requests for useful information, maintenance or modifications are best left to an expert.
I can highly recommend Cyctotronguy (Kent at Passlabs).
Ian
Zilch,
(806 or 806A)? The part number I gave you is the 294-724 sub Altec number in the catalog is they fit the (806) I'm assuming in the catalog 806 means 806A the tech at Parts Express said that it was a direct replacement???
If I decide to go this direction do you want to measure it? I can assemble it and send it to you so you can evaluate it.
Like I said in a previous thread in the DIY section I did get the dead horn/driver working, so I will see how they sound with the factory drivers in them. These 846A's have been sitting for over twenty years so as far as what the finished project will sound like I have no idea. I also do not know what abuse the other driver went through? If the two drivers don't sound up to par then I will do the Radian swap out. Then we can arrange a test session if you like???
J/S-S1A
Here's the Radian page listing their part, #1228, and the Altec drivers it fits: 602, 802, 806, 808, 902, MR902, 904, 908, 909. They only make one for Altec, apparently, in 8 or 16 Ohm variants:
http://www.radianaudio.com/products/...phragms#radian
I don't find the pdf spec sheet for it, though. I showed the one for JBL, because I have some (albeit limited) experience with that one. It includes the response curves and interchangeability claims, which I was unable to verify with that one (#1225).
I have a lead on an 811 horn here locally. Let's see how this unfolds with respect to driver(s) and diaphragms to test with it....
Here's a curve by Shawn Fogg of a light diaphragm 902 on a 511 horn. This should be somewhat indicitive of Model Nineteen performence potential.
Below that a plot Shawn made of a T-35
looks like the modeled M19 compensation is about right then... whaddya know
(and my 807 + Symb. diaphragms suck... in measurement comparison). -grumpy
Thanks again, Tom. A pattern emerges, looks like.
Also, the T-35 curve compares well with the one Mr. Widget posted.
Shawn's 1/24 octave TrueRTA is KILLER!
For reference, here's my sim analysis of M19 compensation, for any who might find it of related interest:
http://audioheritage.org/vbulletin/s...ary#post128826
A rework of M19 with LEAP would be a worthy endeavor....
Yeah, looks like EV had good QC. Here's a sheet on the ST-350 "butt cheek" (same motor and diaphragm but different horn) which shows similar behavior and a compensation circuit for use with it.
http://archives.telex.com/archives/E...350B%20EDS.pdf
Tom, the tweeters Jack is sending to Storm are T-35B. The T-35A has better frequency response than the T-35s Storm presently has. Any info on T-35B available?
http://archives.telex.com/archives/E...T35A%20EDS.pdf
Should I swap them out with what I currently have?
I love this forum and especially Jack! It is so wonderful that people like us can share and help each other out.
Thanks again Jack!
-Storm.
There are currently 2 users browsing this thread. (0 members and 2 guests)
Posting Permissions
Reply With Quote