Film-Tech Forum ARCHIVE: D-2 Analyzer Now Available

This is topic D-2 Analyzer Now Available in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=006351

Posted by Mark Gulbrandsen (Member # 72) on 07-11-2004, 03:51 PM:

After looking on the AcoustX web site I'm not sure that I want to get my R-2 serviced although I probably will. The new D-2 is certainly a triffle lighter, alot smaller, and less expensive than its predecessor the R-2 was. Was wondering of anyone here has bought one yet and given it a good wringing out? My R-2 needs some attention and I'll probably go ahead and fix it once more but after that D-2 here I come.
www.acoustx.us

Mark @ CLACO

Posted by Michael Schaffer (Member # 1204) on 07-11-2004, 09:36 PM:

There isn`t really that much information about what the software can do on the website. But I doubt it has anywhere near as many functions as the IE-33.
Since the mux/mic package is the same you get when you buy the USL set, what is the point in having this system? I use the USL set with the IE-33. It has a ton of RTA functions including quick memory and extensive memory management, and all the extra stuff like the phase checker, signal generator, RMS voltage display, NC and NR. They promised RT60 will follow. It can also play homemade test signals when you store them as wav or mp3 file. Then there is the little scope function. OK, I discovered it has a little phase offset, but you can work around that if you know it is there. Still, there are so many things you can do spontaneously that you would need to set up a lot of other equipment to do, like quick analog a chain test, or look at the timecode shape when you have a DTS problem. I also used the strip chart function to track down a reel with bad timecode by recording the output of the reader rather than standing next to the projector and staring at the green light for 2 hours.
Granted, there is a certain lag, but I guess the D2 system isn`t complete real time either since it`s PC based too.

Posted by Jonathan M. Crist (Member # 413) on 07-11-2004, 10:30 PM:

If they were to make a combination model would it be called R2D2?

Posted by Steve Guttag (Member # 268) on 07-11-2004, 11:33 PM:

Oh Michael, there is one HUGE difference...

The R2 and now the D2 have offset files for each microphone. Unlike your IE-33 and standard USL multiplexer...the software controls the multiplexer for the D2. Thus, the appropriate offset files are used for each mic to have an accurate display. With the USL multiplexer, you analyzer is only as accurate as your microphones and Countryman mics are not that flat (not horrible either). The D2 will also provide normalizing. That is, mics 2, 3 and 4 are referenced to mic 1 so that the display doesn't bounce all around. Sure, you can set up a USL multiplexer each time you set up your mics but with the D2 this should be automatic.

The Ivie is certainly handy and small but for accurate multimic measurements...it isn't in the same league as an R2 or D2. I've only played with the IE-33 a few times and I'm not convinced its RTA is accurate either...when A/Bing it against other RTAs of known performance...I need to do more testing though.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 07-11-2004, 11:49 PM:

I've always felt that the R-2 was the best thing to come out of the THX program by far. As for the D-2 I wouldn't expect it to do a whole lot more than the R-2 did except operate in a Windows 32 bit software environment. Its designed to perform a fixed set of tests. That its now Windows 32 bit based alone offers far more speed and data throughput than the Pocket based Ivie can do in its most mature version. As a bonus the D-2 does offer a bit better resolution than the R-2 did with the addition of 1/6 and 1/12 octave plus the usual 1/1, and 1/3 measurements. Its meant for THX, THX type systems, and those that want to design systems and work to that standard, which by the way is a very good standard. Those that are not interested in working to a standard, or doing work of that type should probably purchase the Ivie or something else similar. The R-2 or D-2 for that matter is still far superior for EQ'ing most other types of cinema speaker systems. The Ivie simply is not intended for the same type of job as the R-2 or D-2 which is Cinema work, simple as that. With experinece to back this up I can honestly say that about 9 years ago I went the Ivie route purchasing a PC-40 first like several others here have purchased the IE-33. I soon found out that the R-2 was so much more accurate for many of the reasons that Steve mentioned plus how well its software averaged out the response was so amazing that I immediately bought an R-2 after just my first exposure to it. EQ any decent cinema system with the R-2, take a good listen after EQ'ing with good source material at how much better the spectral balance is and you'll instantly wonder why you bought the Ivie. My PC-40 has been a wonderful backup analyzer though and I still have it and occasionally use it with just the single mic, mainly just for A chains and simple system balancing.
I for one look forword to ordering a new D-2 in the very near future. The second huge difference Steve forgot to mention is that the D-2 is priced at just a little more than half what the R-2 cost 9 years ago!

Mark

P.S. Its a very interesting experiment to EQ a system with the Ivie with either single mic or with the USL 4 mic setup and then check that EQ with an R-2. You'll be blown away by how far off the EQ is.

Posted by Michael Schaffer (Member # 1204) on 07-12-2004, 04:34 AM:

What I do to keep the rta from bouncing all over the place is to average mic 1 for 10 seconds, then go to mic 2 for the same number of samples, and so on. I also once set up the mics all next to each other, and the response wasn`t really very different between them (it was, but like Steve said, not dramatically). I also store and look at the individual microphone curves, and subtract them from the curve of the microphone in "the best spot" to determine where there are problems caused by the room in certain places. I haven't had an opportunity yet to compare it directly to an R2 system. However, I think that is just as good, considering that the room isn't static anyway, and it depends on so many factors, like exactly where you put the mics, so there is no "perfect" measurement anyway.

Posted by Mark Gulbrandsen (Member # 72) on 07-12-2004, 08:12 AM:

I've always felt the R-2's special ability lies more with the averaging part of the software than the normalizing of the mics themselves, but the normalizing is a nice featyure as well. The 10 second readings per mic that you are taking will just result in less accuracy but it may be adaquate for your needs. I tried the evact same thing with my Ivie PC-40 but got no where near as good of results as I get with the R-2. As as result I sold off my USL mic system years ago. The R-2 reads from a different mic every second with a user select of 20 to 60 seconds. It can slso free run average which is also very handy. Longer 60 readings will give increased resolution at low frequencies and is great for lookiing at subwoofers responses.
What I fould is that the net difference in sound quality after using the R-2 vs. my PC-40 and USL mics is huge.

Mark

Posted by Michael Schaffer (Member # 1204) on 07-12-2004, 11:00 PM:

Why should it make a difference whether you look at each mic for 10 seconds (or 15 or 20, whatever) and switching between the mics every second? Since the room is "breathing", it would seem to me that letting the reading settle before going to the next mic makes it more representative of the overall picture. In any case, switching between mics more or less rapidly (be it 1 or 10 seconds) only serves the purpose of getting 4 different hopefully valuable readings and then find the overall picture by averaging the readings. So I would think that the end results shouldn`t be that much different from each other.

Posted by Mark Gulbrandsen (Member # 72) on 07-12-2004, 11:34 PM:

Its as simple as this... The more samples you feed into an averaging device over a period of time the more accurate your averaged reading is going to be. Perhaps comparing it to the differences in digital audio sampling rate would be easier to understand. The R-2 has ten tmes the sampling rate that you are presently using. Yours can do more samples though and I used to use 1 to 2 per second with the USL on my PC-40. Since the room does breathe among other things, taking more readings at those four points gives you a far more accurate averaged response. By taking too long of reading per mic you are likely missing the short time constant variables that happen in the room into the averaged reading. Averaging these in are as inportant as averaging in the long time constant variables which the R-2 also captures and which yours is only really capturing while running at one sample per 10 seconds. Note that on the R-2 the once per second multiplexer rate is fixed while the length of time the readings are averaged is a user set variable of 20, 30, or 60 seconds, or free running. The R-2 does this in either one octave or 1/3 octave modes.The D-2 does all of what the R-2 does but offers higher resolution in an updated design running with more modern 32 bit software. the other advantage is as Steve G said. The mics are all calibrated and normalized and the files for mic calibration are stored in a software file for each mic. This built in calibration feature brings even more accuracy into the game.

Mark @ CLACO

Posted by Michael Schaffer (Member # 1204) on 07-13-2004, 12:45 AM:

How many samples does the R2 take per second and what is the decay setting?

Posted by Mark Gulbrandsen (Member # 72) on 07-13-2004, 08:18 AM:

I don't know what the sampling rate is of its A to D convertors but bsed on the available technology back then its probably 48khz. As I said above the multiplexer switches each mic in for one second. The averaging time is 20, 30, or 60 seconds long. Two seperate functions. It has a user selectable fast or slow decay time just like any analyzer does. There is a built in inverse ISO X curve which you can also program into your analyzer. I also have it ptogramed into my PC-40.
Mark

Posted by Gordon McLeod (Member # 33) on 07-13-2004, 10:44 AM:

I beleive the R2 does a 1 sec sample on each mic before switching to the next
Also doing a 10 sec sample then moving on does not average the SPL so there will be a display bounce

Posted by Michael Schaffer (Member # 1204) on 07-13-2004, 07:18 PM:

I think I worded this unclearly: I didn't mean one sample every 10-15 seconds, I meant 10 seconds of averaging, then switching to the next mic. The IE-33 takes about 10 samples per second. Or maybe I should say it "polls" to avoid confusion with samples as in a/d conversion. The sampling rate of the a/d converter is obviously much higher. That's what I meant in my question to Mark, the polling rate, the number of samples which go into the complete picture.
Anyway, in averaging mode, the IE-33 still takes about 2 samples per second, so you get 20-30 samples per mic which I think is enough to give you a good overall picture. Yes, the display bounces when you switch, but it settles quickly, and at the end you have averaged readings from all 4 microphones resulting from 80 readings.
To determine whether the level difference and the switching bounce spoil the result, I tested the method by reading each microphone separatley for 30 seconds, storing the result and clearing the display before going on to the next. Then I subtracted the 4 resultant curves from each other. Finally, I repeated the "live" switching and compared the result to this curve. There was no difference worth mentioning. I also repeated the test under "laboratory" conditions with a file of pink noise suddenly raising in 3dB steps every 10 seconds.
BTW, how well does the Dolby mux work?

Posted by Gordon McLeod (Member # 33) on 07-13-2004, 07:21 PM:

the dolby mux onl;y works with the cp500 I don't know if it works with the cp650 or not

Posted by Mark Gulbrandsen (Member # 72) on 07-13-2004, 07:46 PM:

"I meant 10 seconds of averaging, then switching to the next mic."

That is exactly how I understood it. Thats a low resolution method of doing it as I mentioned above. The R-2 is taking 10 readings in the same time period that you are taking in just one. I am also getting 2.5 readings from four different locations during that 10 second period. Hence its easy to see the greater accuracy you get with the R-2 aside from the very tightly done EQ files for each mic that loads with the software, the normalization of the mics, and all the other bells and whistles that I already mentioned. Hey, this is an analyzer designed to do just a certain job, and thats cinemas. All others are designed to do many things in many ways under many circumstances with many different mics, not just one specific job.

Mark @ CLACO

Posted by Michael Schaffer (Member # 1204) on 07-13-2004, 09:51 PM:

quote: Mark Gulbrandsen
The R-2 is taking 10 readings in the same time period that you are taking in just one. I am also getting 2.5 readings from four different locations during that 10 second period.

I still don't understand the big difference. With that method, I am not taking 1 reading in 10 seconds, but 20, which are averaged. The only major difference (as far as the number of readings and the averaging method is concerned), is that the R2 takes all those readings - actually only half as many as the IE-33 in the same time -, then takes a moment and averages all the readings, while the IE-33 averages as it goes. Under the bottom line, there is no difference: the analyzer takes in a number of samples, then calculates the average values of each of them. I don't see why switching every second is more accurate than switching after 10 seconds: the room is active, but the activity does not vary so much that you wouldn't get a representative picture if you look at it for several seconds. That appears to me to be the original concept behind using the mux, to switch around to heighten the chance of catching the room at various moments.
Applying the logic of time resolution you wrote about, the picture should be more accurate with this method, since in a given period of say, 40 seconds, you would get twice as many readings (2 per second as opposed to one per second) which are also averaged.

Posted by Mark Gulbrandsen (Member # 72) on 07-13-2004, 10:44 PM:

"I meant 10 seconds of averaging, then switching to the next mic."

"I am not taking 1 reading in 10 seconds, but 20, which are averaged."
________________________________________________________________

I appreciate your tryiong to explain things but what you are trying to get across seems to be somewhat contradictory which may be why you don't understand the power of the features built into the R-2 or how it works. I can say that I do know exactly what you are doing as my PC-40 will do the exact same thing as the new Ivie. With the R-2 the mic scan rate is fixed at one per second for very good technical reasons. If there were no good reason for the one per second scan rate then it more than likely would also be a variable user adjustment but its not.

Until you've used an R-2 don't assume that your method is doing the same exact thing or arriving at the same results because it is simply not and you would quiclky see that and most importantly hear the difference. Believe me, I already have been your route and gone, so have almost all the others that own an R-2.

I would reccomend that you call and talk to Tim Holmes the designer of thr R-2 and the new D-2 and let him explain why it is far superior and why your system is not as acccurate. He is certainly more qualified than anyone on this site, especially me, to explain it to you. Tim is a very nice guy and you will ennjoy talking with him.

Here is the phone: 415.785.2888

Mark @ CLACO

Posted by Michael Schaffer (Member # 1204) on 07-13-2004, 11:06 PM:

I have used the R2, I never owned one, but as part of a team equipped with it. I thought you said you used PC-40, but nor the IE-33? I don't know its properties, maybe you are right when comparing these to to the R2.
Why would looking at each mic for 10 seconds minimize the change to catch an anomaly? It seems to me that that actually heightens the chance while with 1 second switching you have to be very lucky to be on that mic just as the anomaly develops.
If my memory does not deceive me, the R2 does not average on the fly, but takes the readings in first, then calculates the average. There is the main difference, as the IE-33 does it while it is going, so when you stop it, the average is already there. That doesn't really make it better or worse though. So it doesn't really take much more time (40 seconds, or whatever time you allocate to each mic X4).
I really don't see a major difference here. Except if the R2 takes one sample or poll per switching (which I don't know), then you actually get twice as many samples to work with with the IE-33 (roughly, the polling time when in averaging mode is about 520 ms). It is all about looking at the room for a little while rather than just momentarily, and getting responses from 4 different places which are then averaged.
BTW, how much is the D2 system?

Posted by Mark Gulbrandsen (Member # 72) on 07-13-2004, 11:23 PM:

"If my memory does not deceive me, the R2 does not average on the fly, but takes the readings in first, then calculates the average."
_________________________________________________________________

Now what you are describing may have been how the first THX analyzer worked as it was based around an Ivie PC-40. However I've never seen one of those operate. Tim could tell you about that. But I am glad that you've had the opportunity to use the R-2. It very definately does average on the fly for the user preset times or continous. You can see the response actually "develop" on the computers screen. At the end of the preset time, 20 - 30 - 60 seconds, the averaging simply stops, the computer has already done the averaging. Running the averaging for longer 60 second times gets you a more accurately integrated response and is very useful for accurately integrating low frequencies from subwoofers. Normally I average stage systems for 30 seconds. However, when I am Eq'ing I often start out with it running on continous so I can see the EQ changes I am making as they happen and I don't have to keep re-starting the averaging process all over again. But I generally will go back and do a 30 second reading and then save that as the file. Call and talk to Tim, you will find him very interesting!! The D-2 costs 3495.00 and then you need a decent laptop running with two USB ports running XP Pro since the WinRTA software is a 32 bit software. XP Pro has been the most stable for me in all situations and boots up fast. But you more than likely already have the laptop.

Mark @ CLACO

P.S. There are very good reasons for looking at each mic momentarily. Let Tim explain to you why its done that way.

[ 07-14-2004, 04:26 AM: Message edited by: Mark Gulbrandsen ]

Posted by System Notices (Member # 2357) on 08-06-2008, 05:34 PM:

It has been 1484 days since the last post.