The Dude Posted April 27, 2014 Author Share Posted April 27, 2014 (edited) Well today was a failure for taking a reading. I did have a usb 2.0 extension cable, and I made a long 1/8" plug to rca plug. Which I have everything ran down stairs. I was adjusting my settings when I went from 75 dbs down to nothing. So I went down stair were the setup is and found the breaker on my amp popped. It is a older McIntosh MC2505 that probably needs to be gone through and rebuilt(guess its time to save for that). I noticed the one channel was extremely warm . I feel since it is raining out today that it would be a good day to read Rudy's thread, which I will shortly after running some errands. Chris that would be awesome, it would help a bunch, I am sure Dr. who and Rudy would have no problem with a little plagiarizing if it where to help the folks around here. I will be looking forward to it. Edited April 27, 2014 by duder1982 Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 The good information on that thread came from folks like Dr. Who. He helped me quite a bit with my understanding of the process. There is lots of information out there. For those of us who are new to this idea, the best thing is to dive in and play around with the software, measurements etc. It will start to make sense once you know the book knowledge and then try to apply it. Here is another thread that approaches this topic from a slightly different angle. It does provide some good explanations and graphs. http://www.hometheatershack.com/forums/rew-forum/38617-aligning-driver-phase-rew-v5-example.html Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 duder1982, If I'm not mistaken, you shouldn't have to do the math on drivers and horns to get the initial delay setting. You should be able to use the impulse response function to obtain the time to your listening position for each driver. With each driver's delay in hand, you just figure the difference from the slowest one and add that delay to the faster arrival times. Then, you can go into the crossover and make slight changes to the delay in order to obtain maximum db level with both drivers operating at the crossover frequency. I hope that makes sense. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 27, 2014 Author Share Posted April 27, 2014 duder1982, If I'm not mistaken, you shouldn't have to do the math on drivers and horns to get the initial delay setting. You should be able to use the impulse response function to obtain the time to your listening position for each driver. With each driver's delay in hand, you just figure the difference from the slowest one and add that delay to the faster arrival times. Then, you can go into the crossover and make slight changes to the delay in order to obtain maximum db level with both drivers operating at the crossover frequency. I hope that makes sense. Kind of, once I get up and running. I take a measurement with the impulse tool, from my listening spot. The lf will arrive at one time and the hf will arrive at another, subtract the one from the other, then add that time delay to the fastest( which may be the hf). Which would then slow down the hf to arrive at the same time the lf does. But verify with highest dp at crossover point. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 Correct. That is the basic idea. As you can probably tell, this whole timing thing is optimized for the position at which your mic is sitting, so it should be your listening position. IIRC, in my thread, you will see that Dr. Who recommends inverting the polarity for one set of drivers and shooting for the lowest db level while searching for the optimum delay. Once satisfied, then go back and set the phases correctly. This should also give you the maximum db level at the crossover, thus having the driver phases aligned....at that mic position. One thing to help you 'see' the issue is to take your first delay setting and then run a full sweep. Save it and then once finished tweaking, run another full sweep. Then, superimpose them and see if there is any difference at the crossover area. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 27, 2014 Author Share Posted April 27, 2014 OK I am back up and running and was able to take my first sweeps, I took one of the lf by its self, and one of the hf by its self. mic is approx 3 feet away, I know it not at the listening position but then again I haven't figured out were that will be, I know I will have to go back and do this all over again, but I will learn it now to where hopefully I can go back and do it again with out problems. Right now I am off to cook dinner but will be back later tonight. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 27, 2014 Author Share Posted April 27, 2014 ok, what am I looking at here. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 27, 2014 Author Share Posted April 27, 2014 Are those peaks distortion, Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 What you need to do is look at the system delay in the information box for each sweep and compare the two. Don't get into the IR graphs just yet, but they don't look all that bad to me. As far as the full sweep, take one with both drivers and 20Hz-20kHz. Are you looking at crossing somewhere near 450Hz? Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 BTW, for this to work, you must have one channel hooked up to loopback so that REW can compare the time of your signal to the time of the loopback signal. That is how it determines the difference. Reference the help file for REW for obtaining system delay. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 Are those peaks distortion, The best place to understand the graphs is to review the REW pages and help files. They will help explain what you are looking at. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 27, 2014 Author Share Posted April 27, 2014 Are those peaks distortion, The best place to understand the graphs is to review the REW pages and help files. They will help explain what you are looking at. Thats where I read they are distortion. I will look at the loop back. As far as the full sweep, take one with both drivers and 20Hz-20kHz. Are you looking at crossing somewhere near 450Hz? I was going to shot for 600 hz, when you say take one of both drivers do you mean with or with out them being crossed over. So set the gain to 75 db, and run the sweep from 20-20k. Won't that have a potential of damaging the drivers. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 27, 2014 Share Posted April 27, 2014 Yes, you definitely want to do this with the crossover set where you expect to set it. I mentioned 450Hz based on the graph you posted. Looks like a good place for both drivers. Your LF seems to start rolling off above 500Hz, but it is hard to know how you have things set up. If you want to see what might be the range of options, you can run a full sweep of the LF with no crossover so you can see the driver's full capability. Then, run a sweep on the HF, but set the crossover to protect the driver. Basically find out what the driver can do on the low end and run the sweep from an octave or so above that. Then, superimpose the graphs, which you did above, and see where the drivers have a common range. Then, you can pick a place in that range that suits your taste. Certainly, always protect your HF driver! The loopback channel MUST be set up so that REW can give you system delay. Regardless of what I say, back it up with the REW recommendations. I am going from memory here and I often lose brain cells. Quote Link to comment Share on other sites More sharing options...
jcmusic Posted April 27, 2014 Share Posted April 27, 2014 Are those peaks distortion, The distortion is on the left hand side of the graph. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 28, 2014 Author Share Posted April 28, 2014 BTW, for this to work, you must have one channel hooked up to loopback so that REW can compare the time of your signal to the time of the loopback signal. That is how it determines the difference. Reference the help file for REW for obtaining system delay. I am using a usb mic such as the UMK-1, so I don't think I can add a loop back, or one is even needed, as according to this. http://www.hometheatershack.com/forums/spl-meters-mics-calibration-sound-cards/10001-rew-cabling-connection-basics.html Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 28, 2014 Author Share Posted April 28, 2014 (edited) If you want to see what might be the range of options, you can run a full sweep of the LF with no crossover so you can see the driver's full capability. Then, run a sweep on the HF, but set the crossover to protect the driver. Thats what I did, I only posted the graph with them superimposed. I keep reading back and forth and keep getting confused, I had to have some coffee to wake me up to help read this. But turns out I don't have to calibrate as much since I have a calibration file for the umk-1. I will do some more research on the loop back, to see if I still need it, but if not I don't how I could system delay with out it. In the setup instructions, Its says On the Analysis preferences make sure "Use loopback as timing reference" is not selected Edited April 28, 2014 by duder1982 Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 28, 2014 Share Posted April 28, 2014 Do your research since I am no expert. My understanding is that the loopback is used by REW to establish the baseline timing for the electronic signal. That is then compared to the mic results in order to figure the delay to the mic vs. the signal delay. If you click on the i button on your REW screen, it will open a list of parameters. If the system delay is black, the delay has not been calculated because there is no loopback. Take your time and read the help file. I know it can be overwhelming. Been there, done that. Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 28, 2014 Author Share Posted April 28, 2014 Do your research That's what i am working on. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted April 28, 2014 Share Posted April 28, 2014 If you open the Preferences menu option and click on the Analysis tab, you can read the explanation on the loopback function under the 'help' line. I don't know of any other way to obtain the system delay. You will need a sound card in which you can set one channel for loopback and one for the measurement. Quote Link to comment Share on other sites More sharing options...
beeker Posted April 28, 2014 Share Posted April 28, 2014 There is indeed an active forum member who i met that understands this subject possibly better than anybody. I wish he would take his time to gather and post the facts.... I do understand although cannot describe..I would suggest reading the manuals of several avr's to get a detailed description to compare and create an outlook on this subject... Possibly this forum member may jump in and break it down... He speaks English on these topics that an average audiophile understands... Quote Link to comment Share on other sites More sharing options...
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