Yo Swez, I am currently very close to getting the remainder of the lab I had planned to put together. In case you forgot, I was needing a way of measuring the transfer function/ cabin gain of the vehicle when needed.
I already obtained the laptop a while back. I just purchased a used M-Audio preamp to drive a calibrated mic and feed back to the laptop. I have already selected the mic and necessary cables and probably will order them this weekend, if not today.
Only thing I am unsure about at this point is the spectrum analyzer software. What octave is good enough to work with in autos? I want to go 1/3 octave to save money as I have with the rest of the components, but only if it will be accurate enough to work with.
Replies (13)
swez on 08/4/2007 01:05:47
A 1/3 octave, (31 bands) should be adequate for this level of testing. Yes, there are systems that do 1/24th octave samplings, but that's pretty heavy for car audio work and even high end HT apps too.
Allen & Heath offers a good package that you can try for 14 days for free. If you like it and wish to buy, it's only $10.00 USD. It's worth a shot since you have 2 weeks free to learn about and use for free.
http://www.allen-heath.co.uk/US/DisplayProduct.asp?pview=32
A-H is a leader in live sound mixing systems and can be adapeted to recording studio needs too. They have been around a long time.
Swez
Ash on 08/4/2007 09:03:45
That's pretty inexpensive.. Does not offer much info though on other functions it is capable of though.
The one I had in interest was TrueRTA. Problem is I would like sweeping capabilities for quicker and more accurate measurements which is only offered starting @ level #3 ($69 USD). It does have import/export functions that will work with another program I'm running (BassBox/ Crossover Pro).
I played around with the free trial and it seemed simple, yet the higher levels are complete enough to handle most work beyond car sub material should I want to expand my work. Their support seems pretty good as well.
What do ya think?
swez on 08/4/2007 10:21:21
Yep, you may want to do a google search . Many programs are free to try for a short time. Once you find one that works well, then buy.
The key is features, integration and a good mike. Try to run these test at moderate SPL, as some mikes are very sensitive and 100-105 dB is plenty for near field testing.
Swez
Ash on 08/4/2007 11:31:50
I know you do a lot of pro audio work as well as car. Likewise I have a few goals in home, pro audio rental, and custom car designs.
What are the main basics that I would need to look for in a RTA to cover simple projects in those realms?
swez on 08/4/2007 13:47:46
Frankly, my brother is the lead tech on these items. (He handles the controls as I spot the field) What we try to do as a team is:
1. Set up an array of speakers in a given room
2. Use Pink noise as from a tone generator program
3. Mike each field through the RTA (Front, sides and far field monitors)
4. Search for room peaks and dips and attempt to "flatten" the dips and peaks w/ PEQ
Once we have finished each zone, we blend all zones with time alignment so that all zones are in time sync with the main stage. Then we play various forms of test music and EQ the material to the room so that it sounds as tight and balanced as we can get it.
Room reverberation, sound reflections and absorbtion characteristics are different in each venue. We do our best to dampen hot spots and brighten up the dead zones with speaker placements and EQing each segment in a given area. (We often deal with up to 6 zones in a larger venue like a hockey rink or large meeting hall)
There's more to it and we often have a few hours after the gear is hooked up to dial in a room. That means a team of two have to work rapidly, but accurately through the steps. Dale mans the control board and all electronics setting as I do the field test and zone to zone calibration locations. Unfortunately, that leaves little time to cross train the field guy on how the actual steps work at the mixing board. We use 2-way radios to communicate as we move through a given system setup. We are often working at 200 feet apart in larger rooms and the radios are much better than hand signals. (As we work through the various fields)
It sounds simple, but the guy, (Dale) at the console has a general feel for the room characteristics and does some basic presets to start the sound checks. Then he tweaks time delays and EQ settings based on what the RTA is showing at various sub-octaves on the RTA display to brink down the peaks and raise up the dips to flatten the room out as best we can.
In your application, things are much easier due to the confined area of space that is being worked on. Time delays are minimal, but flattening out the peaks and dips are your goal initially. (Pink Noise Generator, mike and RTA readings are the main tools here)
Once you have the peaks and dips under control, (Pre-EQ setup) and obtain a reasonably flat response showing on the RTA, most of your initial work is now completed. (The speaker responses and the acoustical enviorns have been nulled out... a best as is possible)
Now, you can move on to musical programing steps and adjust overall systemPost-EQ functions to get the type of sound desired.
In a nutshell, we are attempting to remove peaks and dips noted by the RTA. Some of these PEAKS will be reflections and/or speaker hot spots. Some are dip nodes. (Cancellations) The rest is overall speaker response characterization and how they react in the room, car and environs.
Swez
Ash on 08/4/2007 14:07:20
Gotcha. That was very informative and quite interesting. Even though it is work, sounds kinda fun in a way. I bet the results at times brings a smile to one's face, huh?
I noticed that time is of the essence with your work as well. I'll try to keep from going overboard with the software. At the same time, pink noise and a sweep will probably be the way to go? I kinda figure the sweep for the initial transfer function measurent. Then pink noise for tweaking after the install (if EQ is being used). Is that correct?
Here's the link if you want to check it out:
http://www.trueaudio.com/rta_abt1.htm
swez on 08/4/2007 20:52:55
Yes, it is fun once the hard work is done. The setup time is the time grabber. Often the client will request stage speaker placement needs and we do those as requested. The mains and far field monitors are generally based on coverage area and # of expected people in the room for a given event. That's covered in the bid section of the contract and my brother does all the contracts. He has to balance the amount of gear and techs needed to fit the budget of the program.
Yes, we do have to move quickly to get things done. It because the labor rates and such are very competitive in these bids and in order to maintain a reasonable profit margin on the whole gig, we do make every effort to put some pepper in the labor side. The more the labor costs, the lower the overall profits are to the biz. Make a mistake in this section of the bid and we break even or worse.
That's a pretty good program you have posted. I like the dual scope and RTA feature for the kind of things you'll be doing. (Input/output sync and signal camparator feature)
Also, since you'll be homing in on speakers, enclosure and cabin gain testing, sweep and single tones will be primary in the tool kit. Pink noise is great for big picture integration. But when characterizing components, enclosures and transfer gain/cabin gain effects, it's likely to be more like this:
1. Calibrations (Mike, soundcard, RTA and speaker bench tests)
2. Pink noise for an overview of the peaks and dips of a given test
3. Identify focal points on peaks and dips with tone burst tests/sweeps
4. Compare frequency bands from bench test numbers to "in car" numbers plotted
5. Calculate gain affects from step 1 and 4
6. Post EQ for desired overall sound preferences
Step 6 is a user preference step and music is the best source as we observe real time plots off the RTA. This is where time and hands on experience will help you most to dial in a given system in short order later.
Bonus: When using amplifier HP/LP and passive component filters, you can use the Pink and RTA to determine where the crossover frequencies are and their slope rates too. This will help determine phasing at each crossover point used and whether it's additive or subtrative at said points. (That's cool to see and manipulate)
Some of this will be intuitive and you'll eventually develop a solid feel for initial setups and then how to home in on range specifc tests. (Bass, MB, Mids, Upper Mids and Highs)
For now, just take the time to figure out the tool, how best to use it and get familiar with a systemematic test process that works. Too bad we are 1000 miles apart Ash. It would be fun to do these as a team and both of us would learn a lot in the process. ;-)
Swez
Ash on 08/7/2007 13:18:31
Okay.. The M-Audio unit is on it's way. The mic, gooseneck stand, test woofer (have to build box), cables, and other various parts are on their way too.
The only part that I'm missing to complete this is a amplifier to drive the test speaker(s). I started to build a small subwoofer w/ plate amp. It would have been convenient, but not usable beyond bass applications. I decided to go full range for more accurate readings and versatility.
I need a inexpensive, simple, ac powered amp to fit in. All I need is to feed signal to the amp from the program & M-Audio unit, and then from the amp to the speaker to be mic'ed.
I would like a small amp with enough rms power to get accurate readouts. I figure that shouldn't be much more than real 20 watts? Integrated tuners, eq's, and such will just be a waste of space, I would imagine. However those are the cheapest, and by far, the most abundant ones I could find.
What about small PA amps? Will they suffice? I have found a few Radio Shack's on ebay that may work if the inputs are correct. Don't know about the outputs though...
swez on 08/7/2007 14:49:52
You may find PA amps helpful but limited in loads they can handle. (8/4 phm usually)
If you plan to build a nice system someday, consider used Pro level gear like Carver, Crown, MTX, QSC, Yamaha or maybe TOA. (Used musician's/DJ gear) Here, ya get power, durability and clean amps)
The cheapest deal would be an integrated Home version preamp/mixer/ amp. Sony, Onkyo, Panasonic, Pioneer, Marantz, Kenwood and the list goes on. (Garage sale stuff... $30.00?)
Swez
Ash on 08/7/2007 16:26:17
I'm not sure what you mean by "integrated Home version preamp/mixer/ amp". Are you talking about a regular amp like in the days before all the home theater stuff became so popular? The kind that had no tuner or anything, just an amp with bass, treble (perhaps) , various preamp inputs?
If so, that is kinda what I had in mind, even though they are hard to find as they are almost considered vintage. I used to own a old Kenwood like that until one of the channels blew. It was very clean and quite powerful.
swez on 08/7/2007 16:59:50
Yes, like this one:
http://hollywooddj.com/gliproa6300.html
It has several inputs, (Tape, CD, DVD,Tuner, Phono and often has tone controls and Aux outs as needed for EQ loops or Record In/Out)
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=252-125
You can get just a mixer type preamp or integrated preamp/amp versions too. The older receivers had many of these features too, but we are talking "vintage" here bud. (Circa 70's -80's)
Most stand alone amps need a peamp/mixer to gain match the amp. I now use a Crown IC-150 preamp and a Yamaha 2150 amp for Mid/highs. My Peavey CS-800 took a poop for the subs, so now I use a JBL DA-1002 car amp for bass. (Powered by a charger and BAT)
Yeah, it's hack on the bass, but it does work. (300 + WRMS bridged and a 4 ohm load.
I love this vintage Crown IC-150 though. It has great features and has worked very well for over 20 years. The Yamaha amp has plenty of guts to run a pair of Polk 7a Studio monitors and some generic rear fills too. These are old too, but they were built to last if not abused.
Have you considered Pawn Shops in the area? Some decent gear can be had there too for cheap.
Swez
A garage sale is often the best place to buy such things as most have upgraded to Surround Sound HT systems and these are almost throw-aways to those who don't realize the vintage value.
Ash on 08/10/2007 21:20:07
Wow! Your'e not going to believe this but, I found a suitable amp on ebay. The stunning part is that it is the same exact model (Kenwood KA-3500 ) that I had before! Talk about luck. In fact I was the only one that bidded on it, so I wound up getting it for $34.?? shipped.
It is only about 35 real watts per channel but it is 4 ohm stable. Powerful and versatile enough to get decent measurements beyond 3db with various drivers.
It just feels so weird (in a good way) that I ran across the same model after remininscing over the old amp. Hopefully it's a sign of good things to come out of this project. I am hoping to expand it into a lucrative business in the long run
In the meantime, when I get a chance, I'll fiddle around with the TrueRTA free version to get familiar with it before buying.
Wish me luck!
swez on 08/11/2007 00:53:14
Uhmmm, that's not dumb-luck or serendipity Ash. That was a gift from on high.
Ever try the "Ask, Seek & Knock" type conversation with the Big Guy Upstairs? If yes, then you know exactly what this is about. If not, man... do I have a private message for you on that subject! (It's a bit too personal to share here, but the story line will knock your socks off)
Swez ><>
I already obtained the laptop a while back. I just purchased a used M-Audio preamp to drive a calibrated mic and feed back to the laptop. I have already selected the mic and necessary cables and probably will order them this weekend, if not today.
Only thing I am unsure about at this point is the spectrum analyzer software. What octave is good enough to work with in autos? I want to go 1/3 octave to save money as I have with the rest of the components, but only if it will be accurate enough to work with.
Replies (13)
swez on 08/4/2007 01:05:47
A 1/3 octave, (31 bands) should be adequate for this level of testing. Yes, there are systems that do 1/24th octave samplings, but that's pretty heavy for car audio work and even high end HT apps too.
Allen & Heath offers a good package that you can try for 14 days for free. If you like it and wish to buy, it's only $10.00 USD. It's worth a shot since you have 2 weeks free to learn about and use for free.
http://www.allen-heath.co.uk/US/DisplayProduct.asp?pview=32
A-H is a leader in live sound mixing systems and can be adapeted to recording studio needs too. They have been around a long time.
Swez
Ash on 08/4/2007 09:03:45
That's pretty inexpensive.. Does not offer much info though on other functions it is capable of though.
The one I had in interest was TrueRTA. Problem is I would like sweeping capabilities for quicker and more accurate measurements which is only offered starting @ level #3 ($69 USD). It does have import/export functions that will work with another program I'm running (BassBox/ Crossover Pro).
I played around with the free trial and it seemed simple, yet the higher levels are complete enough to handle most work beyond car sub material should I want to expand my work. Their support seems pretty good as well.
What do ya think?
swez on 08/4/2007 10:21:21
Yep, you may want to do a google search . Many programs are free to try for a short time. Once you find one that works well, then buy.
The key is features, integration and a good mike. Try to run these test at moderate SPL, as some mikes are very sensitive and 100-105 dB is plenty for near field testing.
Swez
Ash on 08/4/2007 11:31:50
I know you do a lot of pro audio work as well as car. Likewise I have a few goals in home, pro audio rental, and custom car designs.
What are the main basics that I would need to look for in a RTA to cover simple projects in those realms?
swez on 08/4/2007 13:47:46
Frankly, my brother is the lead tech on these items. (He handles the controls as I spot the field) What we try to do as a team is:
1. Set up an array of speakers in a given room
2. Use Pink noise as from a tone generator program
3. Mike each field through the RTA (Front, sides and far field monitors)
4. Search for room peaks and dips and attempt to "flatten" the dips and peaks w/ PEQ
Once we have finished each zone, we blend all zones with time alignment so that all zones are in time sync with the main stage. Then we play various forms of test music and EQ the material to the room so that it sounds as tight and balanced as we can get it.
Room reverberation, sound reflections and absorbtion characteristics are different in each venue. We do our best to dampen hot spots and brighten up the dead zones with speaker placements and EQing each segment in a given area. (We often deal with up to 6 zones in a larger venue like a hockey rink or large meeting hall)
There's more to it and we often have a few hours after the gear is hooked up to dial in a room. That means a team of two have to work rapidly, but accurately through the steps. Dale mans the control board and all electronics setting as I do the field test and zone to zone calibration locations. Unfortunately, that leaves little time to cross train the field guy on how the actual steps work at the mixing board. We use 2-way radios to communicate as we move through a given system setup. We are often working at 200 feet apart in larger rooms and the radios are much better than hand signals. (As we work through the various fields)
It sounds simple, but the guy, (Dale) at the console has a general feel for the room characteristics and does some basic presets to start the sound checks. Then he tweaks time delays and EQ settings based on what the RTA is showing at various sub-octaves on the RTA display to brink down the peaks and raise up the dips to flatten the room out as best we can.
In your application, things are much easier due to the confined area of space that is being worked on. Time delays are minimal, but flattening out the peaks and dips are your goal initially. (Pink Noise Generator, mike and RTA readings are the main tools here)
Once you have the peaks and dips under control, (Pre-EQ setup) and obtain a reasonably flat response showing on the RTA, most of your initial work is now completed. (The speaker responses and the acoustical enviorns have been nulled out... a best as is possible)
Now, you can move on to musical programing steps and adjust overall systemPost-EQ functions to get the type of sound desired.
In a nutshell, we are attempting to remove peaks and dips noted by the RTA. Some of these PEAKS will be reflections and/or speaker hot spots. Some are dip nodes. (Cancellations) The rest is overall speaker response characterization and how they react in the room, car and environs.
Swez
Ash on 08/4/2007 14:07:20
Gotcha. That was very informative and quite interesting. Even though it is work, sounds kinda fun in a way. I bet the results at times brings a smile to one's face, huh?
I noticed that time is of the essence with your work as well. I'll try to keep from going overboard with the software. At the same time, pink noise and a sweep will probably be the way to go? I kinda figure the sweep for the initial transfer function measurent. Then pink noise for tweaking after the install (if EQ is being used). Is that correct?
Here's the link if you want to check it out:
http://www.trueaudio.com/rta_abt1.htm
swez on 08/4/2007 20:52:55
Yes, it is fun once the hard work is done. The setup time is the time grabber. Often the client will request stage speaker placement needs and we do those as requested. The mains and far field monitors are generally based on coverage area and # of expected people in the room for a given event. That's covered in the bid section of the contract and my brother does all the contracts. He has to balance the amount of gear and techs needed to fit the budget of the program.
Yes, we do have to move quickly to get things done. It because the labor rates and such are very competitive in these bids and in order to maintain a reasonable profit margin on the whole gig, we do make every effort to put some pepper in the labor side. The more the labor costs, the lower the overall profits are to the biz. Make a mistake in this section of the bid and we break even or worse.
That's a pretty good program you have posted. I like the dual scope and RTA feature for the kind of things you'll be doing. (Input/output sync and signal camparator feature)
Also, since you'll be homing in on speakers, enclosure and cabin gain testing, sweep and single tones will be primary in the tool kit. Pink noise is great for big picture integration. But when characterizing components, enclosures and transfer gain/cabin gain effects, it's likely to be more like this:
1. Calibrations (Mike, soundcard, RTA and speaker bench tests)
2. Pink noise for an overview of the peaks and dips of a given test
3. Identify focal points on peaks and dips with tone burst tests/sweeps
4. Compare frequency bands from bench test numbers to "in car" numbers plotted
5. Calculate gain affects from step 1 and 4
6. Post EQ for desired overall sound preferences
Step 6 is a user preference step and music is the best source as we observe real time plots off the RTA. This is where time and hands on experience will help you most to dial in a given system in short order later.
Bonus: When using amplifier HP/LP and passive component filters, you can use the Pink and RTA to determine where the crossover frequencies are and their slope rates too. This will help determine phasing at each crossover point used and whether it's additive or subtrative at said points. (That's cool to see and manipulate)
Some of this will be intuitive and you'll eventually develop a solid feel for initial setups and then how to home in on range specifc tests. (Bass, MB, Mids, Upper Mids and Highs)
For now, just take the time to figure out the tool, how best to use it and get familiar with a systemematic test process that works. Too bad we are 1000 miles apart Ash. It would be fun to do these as a team and both of us would learn a lot in the process. ;-)
Swez
Ash on 08/7/2007 13:18:31
Okay.. The M-Audio unit is on it's way. The mic, gooseneck stand, test woofer (have to build box), cables, and other various parts are on their way too.
The only part that I'm missing to complete this is a amplifier to drive the test speaker(s). I started to build a small subwoofer w/ plate amp. It would have been convenient, but not usable beyond bass applications. I decided to go full range for more accurate readings and versatility.
I need a inexpensive, simple, ac powered amp to fit in. All I need is to feed signal to the amp from the program & M-Audio unit, and then from the amp to the speaker to be mic'ed.
I would like a small amp with enough rms power to get accurate readouts. I figure that shouldn't be much more than real 20 watts? Integrated tuners, eq's, and such will just be a waste of space, I would imagine. However those are the cheapest, and by far, the most abundant ones I could find.
What about small PA amps? Will they suffice? I have found a few Radio Shack's on ebay that may work if the inputs are correct. Don't know about the outputs though...
swez on 08/7/2007 14:49:52
You may find PA amps helpful but limited in loads they can handle. (8/4 phm usually)
If you plan to build a nice system someday, consider used Pro level gear like Carver, Crown, MTX, QSC, Yamaha or maybe TOA. (Used musician's/DJ gear) Here, ya get power, durability and clean amps)
The cheapest deal would be an integrated Home version preamp/mixer/ amp. Sony, Onkyo, Panasonic, Pioneer, Marantz, Kenwood and the list goes on. (Garage sale stuff... $30.00?)
Swez
Ash on 08/7/2007 16:26:17
I'm not sure what you mean by "integrated Home version preamp/mixer/ amp". Are you talking about a regular amp like in the days before all the home theater stuff became so popular? The kind that had no tuner or anything, just an amp with bass, treble (perhaps) , various preamp inputs?
If so, that is kinda what I had in mind, even though they are hard to find as they are almost considered vintage. I used to own a old Kenwood like that until one of the channels blew. It was very clean and quite powerful.
swez on 08/7/2007 16:59:50
Yes, like this one:
http://hollywooddj.com/gliproa6300.html
It has several inputs, (Tape, CD, DVD,Tuner, Phono and often has tone controls and Aux outs as needed for EQ loops or Record In/Out)
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=252-125
You can get just a mixer type preamp or integrated preamp/amp versions too. The older receivers had many of these features too, but we are talking "vintage" here bud. (Circa 70's -80's)
Most stand alone amps need a peamp/mixer to gain match the amp. I now use a Crown IC-150 preamp and a Yamaha 2150 amp for Mid/highs. My Peavey CS-800 took a poop for the subs, so now I use a JBL DA-1002 car amp for bass. (Powered by a charger and BAT)
Yeah, it's hack on the bass, but it does work. (300 + WRMS bridged and a 4 ohm load.
I love this vintage Crown IC-150 though. It has great features and has worked very well for over 20 years. The Yamaha amp has plenty of guts to run a pair of Polk 7a Studio monitors and some generic rear fills too. These are old too, but they were built to last if not abused.
Have you considered Pawn Shops in the area? Some decent gear can be had there too for cheap.
Swez
A garage sale is often the best place to buy such things as most have upgraded to Surround Sound HT systems and these are almost throw-aways to those who don't realize the vintage value.
Ash on 08/10/2007 21:20:07
Wow! Your'e not going to believe this but, I found a suitable amp on ebay. The stunning part is that it is the same exact model (Kenwood KA-3500 ) that I had before! Talk about luck. In fact I was the only one that bidded on it, so I wound up getting it for $34.?? shipped.
It is only about 35 real watts per channel but it is 4 ohm stable. Powerful and versatile enough to get decent measurements beyond 3db with various drivers.
It just feels so weird (in a good way) that I ran across the same model after remininscing over the old amp. Hopefully it's a sign of good things to come out of this project. I am hoping to expand it into a lucrative business in the long run
In the meantime, when I get a chance, I'll fiddle around with the TrueRTA free version to get familiar with it before buying.
Wish me luck!
swez on 08/11/2007 00:53:14
Uhmmm, that's not dumb-luck or serendipity Ash. That was a gift from on high.
Ever try the "Ask, Seek & Knock" type conversation with the Big Guy Upstairs? If yes, then you know exactly what this is about. If not, man... do I have a private message for you on that subject! (It's a bit too personal to share here, but the story line will knock your socks off)
Swez ><>
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