My life with an RTA
Guest
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[/qb][/QUOTE]No, it's can't be that useful. My eq is only 1/3 oct. More then that would just be a toy. [/QB][/QUOTE]very, i mean very incorrect, there is a awful lot of freqencies that dont get addressed by a 1/3 oct eq and analyzer,never underestimate the power of control [img]graemlins/thumb.gif[/img]
Thread Starter
1000 Watt CAFz'r
Joined: Oct 2003
Posts: 1,783
I'm going to summarize what I'm reading here:
Some people without a high resolution RTA doubt it's usefulness, the person with one (me) find it useful.
So far I've shown NO graphs, explained no usefull gains I've aquired in SQ by using it, and...I've actually complained that my tuning using the RTA has resulted in POOR SQ!
Yes...it is starting to sound like a toy, but that would be my fault.
Here is what I've learned so far using the RTA:
I've got 6 areas of cancellation in my car.
My IB mounted door speakers have an area of increased sensitivity because of the mounting,(between 40hz and 150hz) not an area of cancellation(above 150hz)as I'd previously thought.
I've tried 4 different tweeters in the car, I now know where the car peaks in FR regardless of the tweeter or the position. This required 200 point per octave resolution to get repeatable response.
Ever wondered what your X.O. or EQ actually does? I've found numerous areas where the marked X.O. or EQ point is off, sometimes quite a bit.
I've put the Bag End ELF-1 processor in my car, and measured the response of that. It's a pretty radical processor so I'd advise using an RTA when EVER it is installed.
This one is a bit tricky. I've measured the effects of varying delay to drivers. Most people will have a hard time doing this, as the delay is controlled by a deck or processor. The RTA that I use, uses a signal level input, not a pink noise CD to generate FR graphs. So you basically can't measure the effect if your delay is "deck" based, or proc based without a line level in. I use delay modules in my Audison amps so I can easily measure this. But...with this too I found that the marked delay wasn't accurate. For this, I was able to use an impulse response test to measure induced delay and correctly mark that on the amps.
The effects of varying delay to drivers can be hard to measure. If you don't have a good understanding of where the vehicle naturally has some cancellation, tuning becomes pretty difficult. This was a very important baseline for me to have, as I found a total of 6 areas with some deviance. 2 of those areas fall within X.O. bands.
A few of you have mentioned using the RTA with a 31 band EQ. I would suggest using an RTA without the EQ on raw drivers without any X.O. (tweeter should have something at say 1khz) Why run a speaker outside it's optimum range and EQ it to fit your purpose? Find it's optimum range BEFORE you EQ or X.O. the driver.
A good reference that I have heard and used: Run the driver 1 octave above and 1 octave below it's natural ON AXIS roll-off. So for example, my Focal Utopia 4" mid will play from 100hz up to 8khz on axis. (In car response) I've crossed it over at 200hz and 4khz. Please note that this was correlated with hours of listening. I always take the theories I use to the judge...my ears.
There are many other examples that I can give of how the RTA has helped me so far. While I admit, I'm going way beyond what most people want to understand, it's good to learn.
I run an RTA to learn more about sound, in car acoustics, and to have fun.
I hope others enjoy this toy as much as I do.
Adam
P.S. I do have graphs coming....
[ May 18, 2004, 01:09 PM: Message edited by: PEI330Ci ]
Some people without a high resolution RTA doubt it's usefulness, the person with one (me) find it useful.
So far I've shown NO graphs, explained no usefull gains I've aquired in SQ by using it, and...I've actually complained that my tuning using the RTA has resulted in POOR SQ!
Yes...it is starting to sound like a toy, but that would be my fault.
Here is what I've learned so far using the RTA:
I've got 6 areas of cancellation in my car.
My IB mounted door speakers have an area of increased sensitivity because of the mounting,(between 40hz and 150hz) not an area of cancellation(above 150hz)as I'd previously thought.
I've tried 4 different tweeters in the car, I now know where the car peaks in FR regardless of the tweeter or the position. This required 200 point per octave resolution to get repeatable response.
Ever wondered what your X.O. or EQ actually does? I've found numerous areas where the marked X.O. or EQ point is off, sometimes quite a bit.
I've put the Bag End ELF-1 processor in my car, and measured the response of that. It's a pretty radical processor so I'd advise using an RTA when EVER it is installed.
This one is a bit tricky. I've measured the effects of varying delay to drivers. Most people will have a hard time doing this, as the delay is controlled by a deck or processor. The RTA that I use, uses a signal level input, not a pink noise CD to generate FR graphs. So you basically can't measure the effect if your delay is "deck" based, or proc based without a line level in. I use delay modules in my Audison amps so I can easily measure this. But...with this too I found that the marked delay wasn't accurate. For this, I was able to use an impulse response test to measure induced delay and correctly mark that on the amps.
The effects of varying delay to drivers can be hard to measure. If you don't have a good understanding of where the vehicle naturally has some cancellation, tuning becomes pretty difficult. This was a very important baseline for me to have, as I found a total of 6 areas with some deviance. 2 of those areas fall within X.O. bands.
A few of you have mentioned using the RTA with a 31 band EQ. I would suggest using an RTA without the EQ on raw drivers without any X.O. (tweeter should have something at say 1khz) Why run a speaker outside it's optimum range and EQ it to fit your purpose? Find it's optimum range BEFORE you EQ or X.O. the driver.
A good reference that I have heard and used: Run the driver 1 octave above and 1 octave below it's natural ON AXIS roll-off. So for example, my Focal Utopia 4" mid will play from 100hz up to 8khz on axis. (In car response) I've crossed it over at 200hz and 4khz. Please note that this was correlated with hours of listening. I always take the theories I use to the judge...my ears.
There are many other examples that I can give of how the RTA has helped me so far. While I admit, I'm going way beyond what most people want to understand, it's good to learn.
I run an RTA to learn more about sound, in car acoustics, and to have fun.
I hope others enjoy this toy as much as I do.
Adam
P.S. I do have graphs coming....
[ May 18, 2004, 01:09 PM: Message edited by: PEI330Ci ]
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those who think its a toy to have the ability to see 200 points instead of 30 or so have to see it and use it to see how usefull it can be. i have used the linear x and found it to be so much more usefull than the than the ac 3055, you have to use it to see and reap the benefits of it
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The problem with an RTA is it has no time measurement functions. I agree that they are cool to use and measure stuff with, but beware you don't waste time making measurements that have no bearing on how a systems sounds and start going in the wrong direction. For example find a big dip in response and try and eq it out with an RTA as a reference, notice how alot of dips can't be eq'd out? That's because the problem is also time dependant and not just a matter of level. Like I said, it will give you some foundation for why and how, but it is not the best tool to use for tuning. For $3000 I would rather bring my car to a big competition where people like Scott Buwalda, Jamie E, Tim Baillie, Matt Bogardt etc. are and have them tune the car while I am watching. I am sure they would be more than happy to with a few bucks thrown their way. That way you will learn some basics, see (and hear) a bunch of cool cars, and get some honest opinions of yours all in one, and probably end up spending less in the long run.
Thread Starter
1000 Watt CAFz'r
Joined: Oct 2003
Posts: 1,783
I wish I had the opportunity to have any one of the people DWVW has mentioned listen to and tune my car. I don't know if I'd pay $3000 for it, but it definitely is worth more to the average enthusiast than an RTA.
As for general comments about using your ears to tune: I whole heartedly agree with this. Our ears are able to hear details well beyond what I've accepted as measureable.
And just to clarify one minor point, defro mentioned the difference between 200 and 30 points of measurement. The A.C. 3055 does 30 points across 10 octaves, LMS can do 200 points across ONE octave. (up to a maximum of 800 points in a graph)
I'm still a relative beginner in car audio, there are many things that I continue to struggle to understand. Every little bit of info I get helps me build a better car stereo. The RTA is one source, but many of you on this forum are a much more realistic and real world source for this information. Sometimes I look outside the normal channels for information. The RTA being one of them, and it's a tool that I have a lot of prior experience with. Every time I use some sort of diagnostic tool, from a DMM to an RTA, I find that the knowledge employed by the user is more important than the quality of the instrument.
At this point I'd like to make one comment about my use of the RTA.
I'm still installing the equipment guys, I'm not even close to starting serious tuning. I'm working out how I need to install what I've got for the intended bandwidths applied to each driver. Every week I work on the car something changes. I'm currently considering re-installing my 4 8" subs in my rear deck a 3rd time. My mids have been installed 4 different ways now. (I built fiberglass kick panels last week and changed my mind about how I want to install the mids) I've had 4 sets of tweeters in the car. I've even tried a $5000 CD player in my system just to see how my Alpine deck sounds.
Lots more playing to be done...
Adam
As for general comments about using your ears to tune: I whole heartedly agree with this. Our ears are able to hear details well beyond what I've accepted as measureable.
And just to clarify one minor point, defro mentioned the difference between 200 and 30 points of measurement. The A.C. 3055 does 30 points across 10 octaves, LMS can do 200 points across ONE octave. (up to a maximum of 800 points in a graph)
I'm still a relative beginner in car audio, there are many things that I continue to struggle to understand. Every little bit of info I get helps me build a better car stereo. The RTA is one source, but many of you on this forum are a much more realistic and real world source for this information. Sometimes I look outside the normal channels for information. The RTA being one of them, and it's a tool that I have a lot of prior experience with. Every time I use some sort of diagnostic tool, from a DMM to an RTA, I find that the knowledge employed by the user is more important than the quality of the instrument.
At this point I'd like to make one comment about my use of the RTA.
I'm still installing the equipment guys, I'm not even close to starting serious tuning. I'm working out how I need to install what I've got for the intended bandwidths applied to each driver. Every week I work on the car something changes. I'm currently considering re-installing my 4 8" subs in my rear deck a 3rd time. My mids have been installed 4 different ways now. (I built fiberglass kick panels last week and changed my mind about how I want to install the mids) I've had 4 sets of tweeters in the car. I've even tried a $5000 CD player in my system just to see how my Alpine deck sounds.
Lots more playing to be done...
Adam
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the rta should be used as a starting point, for an initial reference, not as the only tuning tool you use, your ears should be the final tuning tool used always, i agree the rta cant tell you time variation problems, but it is a very usefull tool in setup and initial analyzing
