Calibration help...

[rumonkey2]

OK folks - I'm always tweaking my system/room. Moving speakers/sub/furniture,
playing w/ some sort of trap/absorption. It's a "square room of death" acoustically - 11.5x11.5x8
SPL can get outta hand in here pretty quick. The biggest problems are ringing at higher listening levels & the peaks and nulls from the sub. At moderate levels, things are really ok. But, when I'm home alone, I like to push it a little and some movies just call for it.
I've looked at RTA, REW & BFD briefly - just want something to "tell" me where the biggest problems lie. Which of these, or what other programs, are the most basic & easiest to use?? I still need to get a decent (read acceptable & cheap) sound card for my laptop - thinking the external Audigy. Already have RS Analog meter. Will the free version of TrueRTA be enough to get started? It even seems more complicated/in depth than I'm looking for - calibrating the mic/soundcard and such.
Gimme some ideas...I know to "do it right" it will take time & $$. But looking for a quick, cheap way to at least get started....

[craigsub]

I have not personally tried the REW, having the level 4 TrueRTA and a calibrated microphone set up - but a lot of guys have used it with a Radio Shack, and had good results.



Here is a roommode calculator : link

[rumonkey2]

Thanks Craig - now, showing my newbieness w/ this stuff...

how do I read & apply these calculations...:dizzy:

[craigsub]

Thanks Craig - now, showing my newbieness w/ this stuff...

how do I read & apply these calculations...:dizzy:

To simplify things - we will give you some suggestions for placement of our room treatments, when they come on line.

For now - if you want to play around - put lots of pillows around the room, including, for example, along the back of a sofa that is against a wall ... and perhaps try some heavy drapes, blankets ... and just listen.

You will be amazed at how well your ears can pick out changes in the system.

[rumonkey2]

Craig - do you think just toying with the "free" version of TrueRTA will give me a good enough feel for this - then I can upgrade as I see fit???

[m-fine]

Craig - do you think just toying with the "free" version of TrueRTA will give me a good enough feel for this - then I can upgrade as I see fit???

I know this is a few weeks old, but since you did not get a response let me pipe in.

The free version of TRTA does not really have what need for easy sub calibration. REW is the best free tool right now, although I must caution any reader that there is a TON of mis-information on their forum. The level 4 of RTA which includes sweeps is not all that expensive if you are going to use it for more than one setup, but $99 can be a lot of money to people in the market for items in the TCA price ranges.

If you download REW and follow the setup guide it is relatively easy to get started with taking measurements. It will run a quick sweep and plot FR for you, and you can also look at waterfall charts to see the decay times. RTA has been added in the latest version so you can run a pink noise signal and then make changes and see the impact. PM me if you need any help with getting it setup and getting your first measurements.

Once you have results the next step is what to do with them. You will find room treatments are by far the best way to deal with issues above 100 hz or so, since this is where inexpensive broadband absorption is effective and where EQ begins to become spotty. By that I mean EQing to a flat response in one seat can make another seat even worse. This is the downfall of Audessey and other full range EQ's but that is another discussion.

Room treatments can help a bit in the 50-100 hz range and tuned bass absorbers might work for you even lower, but don't expect a signifigant change in your subs FR curve just by treating the room. EQ is a cheap and effective way to tame bass response that is more effective in the sub woofer range. The Behringer BFD/FBQ units are in the $99-$149 range and are quite powerful for taming the subwoofer's response from 20hz to the crossover. Their biggest issue is the crappy interface not designed for EQ use but REW solves that by becoming a GUI for those units. For a step up in price there is the Behringer DCX2496 which I am a fan of and the QSC DSP30 that Seaton recommends. Prices for those are about $250 and $500. Whatever EQ you choose REW has a filter setting screen where you can look at your measured response, setup the EQ filters in REW and visually see what the corrected response should look like. This is a very cool feature IMHO, and even better, for those that are new to this, you can send your sweep file to anyone else with REW and they can look at it and recommend filter settings for you to try.

Once you have the sub response the way you want, you can use REW sweeps (or the new RTA features) to set the relative delay/phase at the crossover to the center and mains and to set the level of the sub. It is real simple, you make a small change, run a sweep, make a change run a sweep, etc. until you minimize any phase cancellation at the XO point and your levels line up where you want them.

The downside to REW is that even though the software is free, good hardware is not. You can get decent results with a radioshack SPL meter connected to your laptops onboard sound card...if you are lucky. The soundcard on my laptop has a crappy line in and I have a hard time getting any reliable results under 20 hz and forget measuring above 400-500 with that type of setup either. You can certainly collect all the info you need to calibrate a setup but you need to be on the lookout for false readings. If you go to an external USB sound card and a "decent" budget mic like a Behringer ECM8000 you can get better results. Have your mic professionally calibrated and or get a higher quality unit and the results get even better, well beyond what you need for sub calibration. I am thinking about picking up new mic and a USB sound device with built in mic phantom power and all the other goodies you would need for a good REW setup including the MIDI connection to control a BFD EQ. If I do, I will not need it very often, so I will have a chat with Craig about adding a sturdy case and maybe making it available on a loan out basis to TCA customers. I could ship you the tools and config files for REW so all you need to do is hook it up to a USB port on a PC and connect to your receiver and start measuring. Post the results on an FTP server and we can help with the EQ and speaker integration, and then when you are done ship back or on to the next guy.

[rumonkey2]

Thanks M....
Yeh, $99 is alot for me to spend on "extras" - program, mic & such.
I've gotta get an external sound card just to even make this work. I have been playing w/ free TRTA just to try & understand it...so it has helped.
I know anything I do ain't gonna be ideal/perfect. But some tool is better than none. I may try REW or plan to "upgrade" to 3 octave TRTA. But no way am I gonna spend much money on a mic right now. The one in the SPL meter is gonna "have to do" Someday, someday....
It's really more that I just want to learn & get a feel for this. Heck, if I spend too much time trying to "perfect" my system, I have no time to enjoy it...:dizzy:
And, I'm in no way "unhappy" with the way it is now....
Just another "toy" & tool to tweak when I can. But also something, once I learn, to help me setting up "friends" systems....

[m-fine]

A good mic, pre-amp, external soundcard and cables will end up at $200-300 which is a lot of money for one guy unless you do a lot of testing like Craig does, but if spread across a number of people it is cheap. Thats why I am thinking of some sort of loan out system would make a lot of sense.

I could ship it all down to you, and you could pass it around the Alabamma familly for a couple of weeks, then ship it on to Atlanta etc. Would you be willing to pay $5-10 plus shipping to have a quality measurment kit for a week or so? Ideally the shipping would be one way (just pay to send it to the next guy) and if you have a few people local you could split that cost between you.

I am thinking there are enough people who would be willing to rent the tools for a self calibration but not willing to buy them. What do you think? The key is to get the most out of it you would have to be willing to add an EQ to your sub so it may not be popular with <$200 Scamp buyers. OTOH, for those who are getting an MFW-15 from AV123 or future TCA offerings, a $100 EQ investment is relatively small, and another $15-$40 to borrow calibration tools (plus get technical support) might be attractive.

Again, let me know what you think.

[m-fine]

Just another "toy" & tool to tweak when I can. But also something, once I learn, to help me setting up "friends" systems....

If you have the Rat Shack meter, you can add an external USB sound card for $40-75 plus cables and have a very usable setup for REW. If you are looking at it as a toy or hobby, or you plan to use it multiple times this would probably be a better route then "renting" the setup.

The idea is to add a few solutions in between "no calibtation beyond ratshack level setting" and hiring a pro to come to your home, and then having a place to go for help that is more reliable and friendly than some of the forums that discuss this stuff today.

[rumonkey2]

Good idea M! I will pick up a soundcard though - likely the "basic" external Audigy.
So, I will have something to play around with & learn w/ a minimal investment.
I'm sure I'll look your way when I need some help! Thanks...:applause:

[Jakeman02]

Great Idea M, I just received the FBQ-2496 last week and have been getting use to REW and the RS Meter. I'm still pretty cluless except for running sweeps which I'm sticking with right now. The waterfall plots, decay etc, well :salute: maybe later.

I know I've got the least desirable mic to use for sweeps, personally I and I'm sure others with this basic setup would get in on this just to see the differnce in results at a minimal cost so that we can personally see with our own eyes if the upgrade is worth it.

[nwboater]

I know this is a few weeks old, but since you did not get a response let me pipe in.

The free version of TRTA does not really have what need for easy sub calibration. REW is the best free tool right now, although I must caution any reader that there is a TON of mis-information on their forum. The level 4 of RTA which includes sweeps is not all that expensive if you are going to use it for more than one setup, but $99 can be a lot of money to people in the market for items in the TCA price ranges.

If you download REW and follow the setup guide it is relatively easy to get started with taking measurements. It will run a quick sweep and plot FR for you, and you can also look at waterfall charts to see the decay times. RTA has been added in the latest version so you can run a pink noise signal and then make changes and see the impact. PM me if you need any help with getting it setup and getting your first measurements.

Once you have results the next step is what to do with them. You will find room treatments are by far the best way to deal with issues above 100 hz or so, since this is where inexpensive broadband absorption is effective and where EQ begins to become spotty. By that I mean EQing to a flat response in one seat can make another seat even worse. This is the downfall of Audessey and other full range EQ's but that is another discussion.

Room treatments can help a bit in the 50-100 hz range and tuned bass absorbers might work for you even lower, but don't expect a signifigant change in your subs FR curve just by treating the room. EQ is a cheap and effective way to tame bass response that is more effective in the sub woofer range. The Behringer BFD/FBQ units are in the $99-$149 range and are quite powerful for taming the subwoofer's response from 20hz to the crossover. Their biggest issue is the crappy interface not designed for EQ use but REW solves that by becoming a GUI for those units. For a step up in price there is the Behringer DCX2496 which I am a fan of and the QSC DSP30 that Seaton recommends. Prices for those are about $250 and $500. Whatever EQ you choose REW has a filter setting screen where you can look at your measured response, setup the EQ filters in REW and visually see what the corrected response should look like. This is a very cool feature IMHO, and even better, for those that are new to this, you can send your sweep file to anyone else with REW and they can look at it and recommend filter settings for you to try.

Once you have the sub response the way you want, you can use REW sweeps (or the new RTA features) to set the relative delay/phase at the crossover to the center and mains and to set the level of the sub. It is real simple, you make a small change, run a sweep, make a change run a sweep, etc. until you minimize any phase cancellation at the XO point and your levels line up where you want them.

The downside to REW is that even though the software is free, good hardware is not. You can get decent results with a radioshack SPL meter connected to your laptops onboard sound card...if you are lucky. The soundcard on my laptop has a crappy line in and I have a hard time getting any reliable results under 20 hz and forget measuring above 400-500 with that type of setup either. You can certainly collect all the info you need to calibrate a setup but you need to be on the lookout for false readings. If you go to an external USB sound card and a "decent" budget mic like a Behringer ECM8000 you can get better results. Have your mic professionally calibrated and or get a higher quality unit and the results get even better, well beyond what you need for sub calibration. I am thinking about picking up new mic and a USB sound device with built in mic phantom power and all the other goodies you would need for a good REW setup including the MIDI connection to control a BFD EQ. If I do, I will not need it very often, so I will have a chat with Craig about adding a sturdy case and maybe making it available on a loan out basis to TCA customers. I could ship you the tools and config files for REW so all you need to do is hook it up to a USB port on a PC and connect to your receiver and start measuring. Post the results on an FTP server and we can help with the EQ and speaker integration, and then when you are done ship back or on to the next guy.

Matt,

Have you pursued this with Craig? Or has lack of forum interest diminished your interest? Also I think I recall a post of yours (but cant find it now) from some time ago that you were going to do a system calibration write-up. Kind of a made simple thing. While I'm waiting for Sasquatch (gosh I sure hope it's THIS winter) I would like to get whatever else is necessary - a DCX perhaps and PC audio interface. And of course getting everything functioning and learn REW or whatever is recommended. I'd be interested in your current thoughts on all this.

Thanks,
Rod