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Old 02-21-2013   #26
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by bikinpunk View Post
Woosey is right.

Think of a calibration file as not one that calibrates the frequency but the SPL measured at a given frequency.

You need this ability if you want to target a curve of any sort. Otherwise, you won't be guaranteed any accuracy.

For example:
Let's say your mic has a natural rise in response above 5khz (most do). If you don't have a calibration file to compensate for this and flatten this out, then this rise will show up in every measurement. In a fictional world, let's say your Car measured flat. If your mic has a rise above 5khz, you'd measure an apparent rise above 5khz and you'd start cutting it to flatten it (or whatever you'd do to target X curve). You'd be cutting something that's caused by the mic; not by the car.

Make sense?
So where do I get it cal'd at? I don't use any driverack or other device with this mic. Also what about the mic placement/direction questions.

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Old 02-21-2013   #27
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Default Re: The RTA Walkthrough and Usage thread. With Video.

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Originally Posted by 07azhhr View Post
So where do I get it cal'd at? I don't use any driverack or other device with this mic. Also what about the mic placement/direction questions.
it's late (to me) so forgive me for slacking...


you'd have to send it somewhere. Herb @ Cross Spectrum could probably do it. Personally, for the price of a cal + shipping, I'd just pick up the Dayton USB mic and call it a day.

Placement should be near the head area. The video I posted was an 'on the whim' video. I didn't necessarily pay attention to putting the mic exactly where I would if I were measuring and tuning. I plan to cover the nitty gritty with later posts. For now I just wanted to focus on getting people up and running with REW's RTA feature.

Direction will alter the measurement some but consider the environment. It has a more detrimental affect and really overrides the issue of pointing. I've read about pointing the mic up in a diffuse environment but I've not found it to be extremely helpful either way. However, microphones are like speakers, in that they are directional. So, there is some plausibility in placing and pointing the mic for higher frequency content. That said, at the end of the day, it's kind of a wash. A good head space average will yield good results.

When tuning via RTA you have to realize that the target curve may or may not result in the best sound you've ever heard. It really depends on a lot of things. But, if you go with this standard method of measurement, you at least get close... and up through about 5khz, you get a really good response. Above 5khz is typically where I have to do the most final shaping by ear to tailor things to my seated position. RTA'ing it gets you at least 70% there (obviously a made up number but you understand what I mean). And once you get experienced and better understand the correlation between measurement and subjective likes/dislikes, you'll get better at closing the gap from 70% to 90%. I still believe a well trained in will always be able to fix flaws a mic cannot, simply due to the environment you're measuring in.

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Last edited by ErinH; 02-21-2013 at 08:31 PM..
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Old 02-21-2013   #28
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Default Re: The RTA Walkthrough and Usage thread. With Video.

To anyone who has watched the video, be honest...

Did it help?
Would you like me to do anything different?


I ask because I can shoot those videos on my iPhone in minutes and upload them from there. It's incredibly easy on me. I do have a Canon pro-sumer GF10 that is flat out stunning in resolution but if I use that, it requires more effort on the back end and takes longer to get the videos published on youtube. In short, it's just a lot more work. If there isn't an advantage from the viewers' point, then I won't bother doing that. If, however, you guys would like better PQ and a more legitimate video set, then I'll go that route.




Secondly, as we go, let's really try to make this a group effort. Post up your own response curves and methods. Videos, too. I'd like to make this a means to help others learn about the use of measurements and possibly walk people through the basics of tuning. Let's make this an interactive tuning thread. Again, I'm not saying you should lean on measurements but I can guarantee that once you get the basics down and we get a couple more posts on here, you'll be using the RTA to garner some really impressive and quick results. And who doesn't like efficiency?

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Old 02-21-2013   #29
 
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by bikinpunk View Post
To anyone who has watched the video, be honest...

Did it help?
Would you like me to do anything different?

<snip>

Secondly, as we go, let's really try to make this a group effort. Post up your own response curves and methods. Videos, too. I'd like to make this a means to help others learn about the use of measurements and possibly walk people through the basics of tuning. Let's make this an interactive tuning thread.
Being honest, it didn't really help *me,* but that probably should come with a caveat that I'm a web developer and am in front of a computer for 10+ hours a day, so I was up and running with REW in just a couple of minutes after some clicking around. For others, though, I can definitely see the benefit and I'm sure it was quite helpful.

That said, I am by no means particularly knowledgeable about tuning. I've been fumbling through it as I go and feel like while I'm doing *okay,* I'm probably leaving 25% of the "essqueues" on the table, so to speak. A tuning thread is something I'd definitely subscribe to. Seeing how other people are going about getting their results would be interesting -- at least I'd get a better idea if I'm doing it the "right" way myself.
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Old 02-21-2013   #30
 
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Looking forward to following along with this. I'm hoping my install will begin next week so in due time this will be quite useful
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Old 02-22-2013   #31
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Erin has multiple videos on youtube, 21 of em, I think at this time.

I've enjoyed several.

Quote:
I.E. - Mosconi DSP 6to8 Testing
Mosconi DSP 6to8 Testing Part 2
Nice job Erin !
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Old 02-22-2013   #32
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by bikinpunk View Post
To anyone who has watched the video, be honest...

Did it help?
Would you like me to do anything different?


I ask because I can shoot those videos on my iPhone in minutes and upload them from there. It's incredibly easy on me. I do have a Canon pro-sumer GF10 that is flat out stunning in resolution but if I use that, it requires more effort on the back end and takes longer to get the videos published on youtube. In short, it's just a lot more work. If there isn't an advantage from the viewers' point, then I won't bother doing that. If, however, you guys would like better PQ and a more legitimate video set, then I'll go that route.




Secondly, as we go, let's really try to make this a group effort. Post up your own response curves and methods. Videos, too. I'd like to make this a means to help others learn about the use of measurements and possibly walk people through the basics of tuning. Let's make this an interactive tuning thread. Again, I'm not saying you should lean on measurements but I can guarantee that once you get the basics down and we get a couple more posts on here, you'll be using the RTA to garner some really impressive and quick results. And who doesn't like efficiency?
Still working with HOLM, but i hope this weekend I have my measuring "cart" ready ( basically a tool cart where i'm building a pc in an a lcd tv on top with mic and soundcard in the drawers haha... ) and then I will try using this software..

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Old 02-22-2013   #33
 
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by bikinpunk View Post
To anyone who has watched the video, be honest...

Did it help?
Would you like me to do anything different?


I ask because I can shoot those videos on my iPhone in minutes and upload them from there. It's incredibly easy on me. I do have a Canon pro-sumer GF10 that is flat out stunning in resolution but if I use that, it requires more effort on the back end and takes longer to get the videos published on youtube. In short, it's just a lot more work. If there isn't an advantage from the viewers' point, then I won't bother doing that. If, however, you guys would like better PQ and a more legitimate video set, then I'll go that route.




Secondly, as we go, let's really try to make this a group effort. Post up your own response curves and methods. Videos, too. I'd like to make this a means to help others learn about the use of measurements and possibly walk people through the basics of tuning. Let's make this an interactive tuning thread. Again, I'm not saying you should lean on measurements but I can guarantee that once you get the basics down and we get a couple more posts on here, you'll be using the RTA to garner some really impressive and quick results. And who doesn't like efficiency?
It helped me a little, as I have never used REW, and have played a little with TrueRTA. What would help me the most is a discussion on what to look for and what to change, as well as things that can't be changed.

I've used TrueRTA in the past to get a relative flat curve and it sounded horrible. I also found areas that I could not EQ, even with different speakers, installation techniques, etc. I'd imagine this was vehicle specific, etc. I think a video/discussion of you thinking out loud and tuning as you use REW, and come across things like this would be extremely helpful.

What you have posted is great and will help many people get started with the software and the use of an RTA to tune their car. What would be incredibly helpful to me would be now that I have it running, what do I look for? What do I do? I realize this is mainly subjective, but your opinion (based obviously on your expertise), would be greatly appreciated.

And finally....thanks for taking the time to do this!
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Old 02-22-2013   #34
 
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Default Re: The RTA Walkthrough and Usage thread. With Video.

The video was a big help for me. I bought the ď$100 RTAĒ a couple years ago but didnít really use it as much as I thought I would because I didnít really understand how the program worked. I look forward to trying REW.

Keep the videos coming and thanks for sharing all of your audio knowledge!

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Old 02-22-2013   #35
 
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by bikinpunk View Post
To anyone who has watched the video, be honest...

Did it help?
Would you like me to do anything different?


Definitely helped me and I am sure many many others like me would benefit a lot from it. MOAR please

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Old 02-22-2013   #36
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Can you do an impulse response in the car? just curious.

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Old 02-22-2013   #37
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Default Re: The RTA Walkthrough and Usage thread. With Video.

This helped. Thanks. I've had the omni mic system for a while now and not done anything with it/ This should motivate me.

What are your thoughts on sitting in the seat while you measure?
How would it change the results vs not being in the car?
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Old 02-22-2013   #38
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by Wesayso View Post
Can you do an impulse response in the car? just curious.
yes. but your question has multiple meanings. So, can you be more precise as to what you're asking?

Quote:
Originally Posted by goodstuff View Post
This helped. Thanks. I've had the omni mic system for a while now and not done anything with it/ This should motivate me.

What are your thoughts on sitting in the seat while you measure?
How would it change the results vs not being in the car?
I've measured in the Car and out of the car. This is the kind of thing that really needs to be experimented with by the user to see how it works. See my response above regarding mic placement/direction.

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Old 02-22-2013   #39
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by voyagerx View Post
It helped me a little, as I have never used REW, and have played a little with TrueRTA. What would help me the most is a discussion on what to look for and what to change, as well as things that can't be changed.

I've used TrueRTA in the past to get a relative flat curve and it sounded horrible. I also found areas that I could not EQ, even with different speakers, installation techniques, etc. I'd imagine this was vehicle specific, etc. I think a video/discussion of you thinking out loud and tuning as you use REW, and come across things like this would be extremely helpful.

What you have posted is great and will help many people get started with the software and the use of an RTA to tune their car. What would be incredibly helpful to me would be now that I have it running, what do I look for? What do I do? I realize this is mainly subjective, but your opinion (based obviously on your expertise), would be greatly appreciated.

And finally....thanks for taking the time to do this!

Yes. At some point this thread will start to get in to more of the explanation of what you're seeing and ways to attack it. I fully intend to film my process at some point with the caveat that it's not a one size fits all. But I need to try to get everyone who might be interested in that up to speed with knowing how to measure first.

I'd like to have a friend film this for me sometime but that may not be feasible if time is of the essence.

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Old 02-22-2013   #40
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Default Re: The RTA Walkthrough and Usage thread. With Video.

I've used REW a bit before seeing this thread and did not know about the averaging method you used with constant pink noise playing. I have instead used the sweep method by pressing the "measure" button, and the program (I believe) will average how ever many sweeps I choose to do.

Do you know if there is a benefit to your method vs using the built-in "measure" method? I do not think your method can view the more detailed time-domain information like impulse response and waterfall graphs, right? Can your method make use of the auto EQ functions or not? From what I remember reading, it relies heavily on time-domain information for making the best suggestions.

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Old 02-23-2013   #41
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Default Re: The RTA Walkthrough and Usage thread. With Video.

Quote:
Originally Posted by bikinpunk View Post
yes. but your question has multiple meanings. So, can you be more precise as to what you're asking?
While I asked about impulse response, what I wanted to know is impulse and step response. Just trying to figure out if John Dunlavy had a point with his opinion on impulse and step response. See: Loudspeaker designer John Dunlavy: By the Numbers... Page 2 | Stereophile.com

Quote:
Originally Posted by Dunlavy
I think a lot of people, especially those who don't listen to live music a great deal of the time, are not really concerned with whether the music they're reproducing matches the live performance. They're after more of an effect. And so the accuracy of their systems doesn't need to meet the same criteria that would have to be met if one wanted to make a loudspeaker where you couldn't hear the difference between it and the original performance. And that's what we're into. Certainly there's plenty of room in the marketplace for what might be called "good-sounding" speakers, "sweet-sounding" speakers, "nice-sounding" speakers, "pretty-sounding" speakers—everybody hears differently. On the other hand, there are a lot of people who regularly attend live concerts who want accurate reproduction.

Designing with higher-order crossover networks greatly simplifies the blending task between drivers. But what most people don't realize is that one of the really great difficulties in designing with higher-order crossovers is that they store energy. That's very visible when you look at the impulse response of a Speaker that has a second-, third-, or fourth-order network. And the step response also looks terrible.

Of all of the measurements that we take that come more close to predicting, or most close to predicting how a Speaker is going to emulate a properly recorded live performance, it's step response. Everything is implicit if you know how to interpret a step response...if my life depended upon my describing what I thought a speaker was going to sound like, all other factors being equal, I would choose step response. And feel very confident that I would be spot-on.
There's also a paper from Dunlavy going further into what he thought is important in speaker design. I'm just trying to connect the dots between your Power response case, backed up by views from Linkwitz, Geddes and Tool etc. and the views from Dunlavy, Vandersteen, Thiel... what if you get both Power response and timing right? Would that work even better? Is it possible?

Here's Dunlavy's digest take on power response:
Quote:
Originally Posted by Atkinson and Dunlavy
Atkinson: You talk about accuracy, but so far you've just defined that in terms of the impulse or step response on the speaker's intended listening axis. What about the speaker's power output into the room? That surely has as much effect on the perceived balance as the on-axis performance?

Dunlavy: That's certainly true. We pay an awful lot of attention to the power response of the speaker into the room. Because that's one of the things that permits us to determine whether we're listening to a live instrument, let's say with our eyes closed, in a typical room. We hear two things. We hear the direct sound of the instrument, but we also hear all of the reflected sound, the reflections off of all of the boundaries of the room. And the ratio between that direct sound as a function of frequency and the reflected sound determines to our ears whether we perceive it as being realistic or not.

We spent a lot of time and money, over 20 years ago, doing measurements in an anechoic chamber of the three-dimensional response patterns of 17 different musical instruments, including drums, string bass, cello—we measured a bassoon, a clarinet, a violin. If a loudspeaker's directivity pattern is incapable of emulating the aggregate, the average of the patterns of all of these musical instruments, it will never sound "accurate."

Most musical instruments are almost omnidirectional at low frequencies, as are most loudspeakers, so it doesn't pose a problem. But as you go higher in frequency, to between 100Hz and 300Hz, if you don't get the beam-width of the speaker correct in this range—and by "correct" I mean that it simulates most live instruments—it will add warmth, unnatural warmth, to the sound of voices and musical instruments. It'll make the average male voice sound too chesty, very unnatural. As you go up higher in frequency, if you have a tweeter that radiates too broad a pattern...it's going to produce shrieky sounds, it's going to sound too zippy. I think everyone's experienced that, especially from inexpensive speakers that have a rising high end.

So a good designer certainly knows that he has to pay a lot of attention to the polar response of a loudspeaker.
What does the step response look like now with 12 dB slopes and what does it look like if you used 6 dB slopes. (obviously louder volumes would be dangerous for the tweeter).

Just trying to learn, no hidden agenda here. I can relate to both theories, just trying to figure out what works. speakers like Magico get rave reviews and they use eliptical slopes, kinda like brick walls. So who is right, or is there even such a thing as beeing right? What theory comes closer to the real thing, that beeing the music that was recorded? I know it all sounds different compared to each other. Or am I not able to hear that? I was intregued by your test with 4th order and second order networks. If this is not the place for this question I understand. But if we can test the impulse response and step response we might get closer to our goals. I wouldn't know where and how to start, what software to use etc. but I'm sure that can be found somewhere. It's much to cold over here to do it myself in my Garage at this time but I thought it might fit in and make us learn something.

I looked at a lot of speaker reviews on stereophile to see their power response and the subjective opinion on them, just to learn. There were quite a few with good power response that showed a step response that was way different from the ideal step response Dunlavy descibes. I also focussed on resonances from the box itself, trying to figure out what combination would give us the best compromise. That last point is something Magico has high on their list of priorities. And that is something we deal with in the Car as well. The things Highly did with his sub construction to decouple it from the Car comes to mind.
I decoupled my sealed sub from the car the best I could and noticed improved low bass that seems to float giving more depth. It caused less resonances that way.

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Last edited by Wesayso; 02-23-2013 at 06:45 AM..
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Old 02-23-2013   #42
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I've used REW a bit before seeing this thread and did not know about the averaging method you used with constant pink noise playing. I have instead used the sweep method by pressing the "measure" button, and the program (I believe) will average how ever many sweeps I choose to do.

Do you know if there is a benefit to your method vs using the built-in "measure" method? I do not think your method can view the more detailed time-domain information like impulse response and waterfall graphs, right? Can your method make use of the auto EQ functions or not? From what I remember reading, it relies heavily on time-domain information for making the best suggestions.

-J
Please see my first and second posts. I discuss there the two main methods of measurement which should answer your questions. Bottom line: the RTA method isn't as powerful as the impulse method which I will focus on the most. This is what you're talking about, I'm pretty sure.

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Old 02-23-2013   #43
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While I asked about impulse response, what I wanted to know is impulse and step response. Just trying to figure out if John Dunlavy had a point with his opinion on impulse and step response. See: [

Snipped/.


This question is much better suited outside of this particular thread where we can discuss it in more detail. I think it's a really good topic but probably too in depth for here and I don't want to bog this thread down. Seriously, I want to discuss it so feel free to start a new thread.

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Old 02-23-2013   #44
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Default Re: The RTA Walkthrough and Usage thread. With Video.

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This question is much better suited outside of this particular thread where we can discuss it in more detail. I think it's a really good topic but probably too in depth for here and I don't want to bog this thread down. Seriously, I want to discuss it so feel free to start a new thread.
I agree, here it is: What are the key elements in reproducing audio? Power responce, time coherence, ...

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Old 02-23-2013   #45
 
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Default Re: The RTA Walkthrough and Usage thread. With Video.

I hope Erin was serious about making this an interactive thread, because I'm volunteering to contribute. As I said earlier, before installing this system, I'd never done any kind of active tuning. I think I'm getting it, but am fully prepared to embarrass myself here!

Erin's new Build log helped illuminate some of the finer points of the RTA for me a little bit and I also came across frequency response graphs for the Virtus 603s. After seeing both, I decided to bust open the DSP this weekend and redo some things.

I started by changing the crossover points. Without getting too longwinded, the midranges were previously bandpassed at ~600 and 5000. They're now at ~500 and 3000. I also removed all the EQ and re-ran the RTA to see what needed attention. There were a few particularly egregious peaks that I pulled down, but equalization is rather minimal. At least, I think it is. I had a lot more going on before, but don't have anything else to compare to. I hope that's the point of the thread

Here are the results from REW. The average of 4 measurements of 16 samples. This is stereo...forgot to save the individual L&R graphs. Here's the 1/3 octave smoothing. Not a bad start?


Here's 1/12, which reveals some of the trouble spots.


I have a few peaks that definitely need to be knocked down. 110, 750 and 1700 are probably up first. The woofer as a whole might need to be backed down a bit as well.

I also threw in the IASCA tools disc and gave that a listen and a couple of the spectral tests jumped out as problem areas. I noted those and, happily, they mostly matched up with the uglier RTA sections. So that was instructive.

Here's shots of each driver setting in the P-DSP:








I'll leave it alone for a couple days and then try a bit more tweaking. If there's any suggestions out there from people who actually know what they're doing (instead of just faking it like me!), I'd love to hear them.
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Old 02-23-2013   #46
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Default Re: The RTA Walkthrough and Usage thread. With Video.

awesome feedback and contribution! this is the kind of stuff I want this thread to contain. even if it's something that didn't work, the 'journal' of sorts really helps others out.

thanks,
Erin

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Old 02-23-2013   #47
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Default Re: The RTA Walkthrough and Usage thread. With Video.

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Originally Posted by bikinpunk View Post
Please see my first and second posts. I discuss there the two main methods of measurement which should answer your questions. Bottom line: the RTA method isn't as powerful as the impulse method which I will focus on the most. This is what you're talking about, I'm pretty sure.
I think we're talking about the same thing. I was mostly confused why you went through the effort of pointing out how the impulse method is more powerful, but then spent all your effort discussing the rta method.

Either way, I look forward to the discussion here!

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Old 02-23-2013   #48
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Default Re: The RTA Walkthrough and Usage thread. With Video.

I didn't spend "all my effort" on the RTA method.
I just wanted to highlight it for those who can't do the impulse method (ie: don't have an aux input to input signal in to their system).

I'll cover the impulse stuff soon. I've just got other stuff on my plate to finish up.

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Old 02-23-2013   #49
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Default Re: The RTA Walkthrough and Usage thread. With Video.

This is a great feature as well:





These two show the same thing a little differently. They can be used to observe modes and energy storage (for example). As you can see around 40Hz there some weird stuff happening, the SPL are not decaying with time as it does at other frequencies.

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Old 02-23-2013   #50
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This is a great feature as well:





These two show the same thing a little differently. They can be used to observe modes and energy storage (for example). As you can see around 40Hz there some weird stuff happening, the SPL are not decaying with time as it does at other frequencies.
I've got a pretty good example of this in my Build log and plan to go further with it once I get my new DSP installed (it has PEQ). This is the good stuff that I mentioned in my OP and can only be measured via impulse method.

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