AudioCircle
Audio/Video Gear and Systems => Enclosures => Topic started by: *Scotty* on 15 Sep 2012, 03:18 am
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It would be very helpful if those who have used advanced measurement techniques to solve bass problems, such as computer programs utilizing calibrated microphones and the like, would post their experiences.
For instance what programs you used and what approaches proved to be the most effective in defining the scope of the problem.
It would also be nice to know what methods you used to solve your bass response problems once you had them identified.
Scotty
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Scotty:
Great question! It would be great if those in the know would chime in with some answers as it would benefit all of those (like me) who are clueless in this area.
Jim
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The article by Nyal Mellor and Jeff Hedback would be worth a read. It's not exclusively about bass.
http://blog.acousticfrontiers.com/whats-new/2011/10/13/acoustic-measurement-standards-for-stereo-listening-rooms-pu.html
I guess I'm not really sure what *Scotty* wants to know. Using a mic and REW or some other measurement program is a faster and more accurate way to measure in-room response than RTAs or test tones, and will also measure some things that you can't with those other tools (see article above for some examples.)
I started by moving a subwoofer into every reasonable location and measuring the response. That also confirmed that my room behaved more-or-less as the modal simulator predicts. I then tried pairs of subwoofer, as per suggestions by Toole (I think). Sometimes response or decay was better, but it was hard to get them positioned just right. Then I tried dipoles in various locations and orientations. From all of that, I decided what was best for me, set it up that way, and thought about the best steps to take next (still in development).
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I would agree with REW. Great tool that gives a lot of good information and is pretty easy to use (and free!).
An RTA (which REW also has) can be useful for placing subs easily by leaving it on with the mic at the seating position and moving the sub around while watching. This allows you so put the sub on something that makes it pretty easy to slide and make very small adjustments continuous adjustments instead of placing the sub in 100 different places and taking 100 different measurements. When you get close, then you can look at the static measurements to help blend the sub with the mains.
Bryan
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What microphone should be purchased to use with REW?
Scotty
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Here's the actual article that JohnR referenced:
http://blog.acousticfrontiers.com/storage/acoustic_measurement_standards.pdf
Jim
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What microphone should be purchased to use with REW?
Scotty
I think this is a good choice. I'm just wrapping up a review of one now.
http://www.cross-spectrum.com/measurement/calibrated_dayton.html
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What microphone should be purchased to use with REW?
Scotty
I use the Dayton:
Behringer ECM8000 microphone or Dayton EMM-6 microphone
http://www.hometheatershack.com/forums/spl-meters-mics-calibration-sound-cards/10001-rew-cabling-connection-basics.html
http://www.hometheatershack.com/forums/rew-forum/11707-room-eq-wizard-rew-information-index-links-guides-technical-articles-please-read.html
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Thanks to all for the software and microphone recommendations. This is some of the information I was hoping to see.
It looks like the cost to get started measuring your room and your speakers is about equal to the cost associated with the Dayton microphone options, $75 for Basic Plus or $99 for the Premium Plus microphone.
There appears to be very little to stop the average audiophile, except a lack of interest, from measuring the interactions between their system and their listening room and making informed decisions about what steps to take towards optimizing the relationship.
I like Bryan's recommendation, leave the RTA on and move the sub around until you find the best location. In my case I will be moving the second sub on the wall at the rear of the room to find the spot where the bass measures the flattest.
Scotty
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*Scotty*, you also need to add the cost of an audio interface.
I'm not seeing how the method proposed by Bryan can be very effective. It won't be any faster, as you have to move between the sub and the laptop anyway, so you may as well press two buttons each time to get a measurement. Once you've moved it a few times, you won't be able to remember if this RTA is better or not than which other. And then, when you want to optimise decay times, you'll have to move the sub all over again and measure anyway. I'd suggest a methodical approach, mark a set of locations on your room diagram, move the subs there and measure. Then label them in REW for future reference. Then you can analyze them and decide on the next move(s).
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John, Is the audio interface you are referring to a mic preamp or some other kind of box separate from the computer and the Mic
Silly me. I thought the mic would just plug into the microphone input on my laptop.
Never mind, found phantom powered XLR USB interfaces from $29 to $100. It looks $100 to $150, with a worst case of $200 total to get started on measuring.
Scotty.
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Check carefully on the cheap ones before purchase, some of them don't work...
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I have my eye on a Tascam 122Mkii.
Scotty
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I was going to say I don't know why those seem to be popular, but I've realized that you can get them for less than half theprice I can:
http://www.bhphotovideo.com/c/product/657978-REG/Tascam_US_122MKII_US_122MKII_USB_2_0.html
http://www.amazon.com/Tascam-US122MKII-Audio-Midi-Interface/dp/B002TTOJUC
I haven't checked or measured it but a friend of mine is using it successfully with REW. You have to remember to turn the monitor contorl knob the right way.
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Sounds like I need to break down and get in the 21st century and see if my ears are as good as scientific measurements. Nothing gained by sitting on your keester!
Jim
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Sounds like I need to break down and get in the 21st century and see if my ears are as good as scientific measurements. Nothing gained by sitting on your keester!
No, not much. Although I think you're setting yourself up with the "measurements vs listening" angle. It's not a challenge, it's about (IMO) using the tools that you have (or can have) available to you to make your listening experience better.
At this point, it looks like the "cost of entry" for those in the US anyway is $70 for the calibrated mic and $80 for the interface, plus some postage charges. So $150+ total. Ask in the Path of Least Resistance for a "budget" interconnect or power cord and see how many answers you get below that figure. Just putting it into perspective...
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Sounds like I need to break down and get in the 21st century and see if my ears are as good as scientific measurements.
Jim
I'll put money on it that they aren't.
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Thanks guys! For better or worse, I just committed myself to enter the measured arena. I ordered the Cross-Spectrum Calibrated Dayton mic and the Tascam 122MKII mic pre. I guess it's time to familiarize myself with REW.
To be honest, I've been keen to measure for some time, but I am also aware that ignorance can be bliss. As it stands, I'm rather happy with things, but I also understand the degree to which our brains compensate - especially when it's all as familiar as we each find our own setups (which can work against neutrality in rating the sound of 'foreign' systems). Still, it will be very interesting to see how the ''feeling around in the dark'/'just plop the subs over there'' method measures. I've moved my Magnepan 3.7s around quite a bit, but I've only tried my subs in a few absolute (no micro-nudging) locations. The addition of room treatments has been done in a formulaic manner, but some of that isn't mobile (front wall diffusion is glued in place and the corner traps are designed for that specific location).
Thanks for the recommendations, but I fear that this genie is going to be tough to put back in its bottle. I confess a few OCD tendencies and tools like this definitely feed that monster. :lol:
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I'll put money on it that they aren't.
Thanks for you vote of confidence...
I agree with John, it's about the knowledge of it and using it to ones best advantage!
Jim
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Thanks guys! For better or worse, I just committed myself to enter the measured arena. I ordered the Cross-Spectrum Calibrated Dayton mic and the Tascam 122MKII mic pre. I guess it's time to familiarize myself with REW.
To be honest, I've been keen to measure for some time, but I am also aware that ignorance can be bliss. As it stands, I'm rather happy with things, but I also understand the degree to which our brains compensate - especially when it's all as familiar as we each find our own setups (which can work against neutrality in rating the sound of 'foreign' systems). Still, it will be very interesting to see how the ''feeling around in the dark'/'just plop the subs over there'' method measures. I've moved my Magnepan 3.7s around quite a bit, but I've only tried my subs in a few absolute (no micro-nudging) locations. The addition of room treatments has been done in a formulaic manner, but some of that isn't mobile (front wall diffusion is glued in place and the corner traps are designed for that specific location).
Thanks for the recommendations, but I fear that this genie is going to be tough to put back in its bottle. I confess a few OCD tendencies and tools like this definitely feed that monster. :lol:
+1
Jim
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Oh, to expand on my previous post, you will also need some cables, adapters, and a mic stand. The stand is somewhat optional I suppose, if you're only doing bass, I've seen people wedge the mic in the sofa, but it's pretty inconvenient not to have one.
Cables:
* Standard mic cable, 5-6 m
* Output from sound card into stereo, usually a TRS-RCA adapter and a regular RCA cable suffices
* Loopback cable for "calibrating" soundcard. I'm somewhat undecided whether this is truly necessary. If it's done I think it's actually best done with the line-level input, so that means a short TRS-TRS cable.
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Thanks for you vote of confidence...
Not about that whatsoever.
I agree with John, it's about the knowledge of it and using it to ones best advantage!
Jim
Uh yeah. That's why I've been such a proponent about it. Sadly most think they can do it all by ear. If you spend the time required your listening environment will be better.
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Jason:
I'm with Kevin360 on this, in that I really like the way my system sounds. At the end of the day, it is only me that I need to please, right or wrong.
At some point I will take proper measurements and see where it takes me. One thing I will not endenvour to do is go with a digital room eq correction, but that is me.
Jim
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John, I was planning on putting the mic at the listening position at ear level sitting on the back of the couch with enough cabling to
be able to place the laptop close enough to see the RTA from my position near the rear sub-woofer. The positions I can move the sub to are limited and consist of lateral motion towards the corner about 6ft. from its present location. The loading sub-woofer currently sees is something a little less than 2pi.
Moving the sub-woofer progressively closer to the corner would gradually shift its loading from 2pi to pi to 1/8 pi if the sub was fully in the corner.
Somewhere along this continuum should be the location that yields the greatest improvement in damping the room's longitudinal resonant behavior. This position will also yield the flattest bass response. I have a couple more subs I can try to position to tame transverse resonances that exist between the sidewalls but I don't hold out much hope of really knocking them down much without the addition of delay to their output.
EQ is also off the table for me as well. I don't have enough power available to boost the bass to fill in depressions in the bass response curve. This only leaves cutting the power to the response peaks on a parametric basis. In any case I don't have an equalization program for parametric digital equalization that will run on Linux anyway.
Scotty
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Somewhere along this continuum should be the location that yields the greatest improvement in damping the room's longitudinal resonant behavior. This position will also yield the flattest bass response.
I'm very interested to see how you go.
In any case I don't have an equalization program for parametric digital equalization that will run on Linux anyway.
Ah. Which player do you use on Linux? (Apologies if this was covered somewhere else already)
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I really like the way my system sounds. At the end of the day, it is only me that I need to please, right or wrong.
That is true. You are truly the only one that needs to be happy with your system. If you never look outside your box though you will never know what you could be missing. In this case, I'd suspect quite a bit.
At some point I will take proper measurements and see where it takes me.
Great. I look forward to the measurements.
One thing I will not endenvour to do is go with a digital room eq correction, but that is me.
I agree. I've been there and done it. :duh:
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I guess I don't get the anti-EQ bias. Like measurements, it's just a tool. You can learn to use it effectively, or not.
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I guess I don't get the anti-EQ bias. Like measurements, it's just a tool. You can learn to use it effectively, or not.
I try not to use it if it can be avoided. I tried DRC and although it does help there are much better ways to accomplish the same thing. Room treatments and maybe a slight eq if needed.
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You think DRC == EQ?
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You think DRC == EQ?
Yes but DRC (one box unit) typically is automatic with very little flexability.
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Yes but DRC (one box unit) typically is automatic with very little flexability.
Right... and DRC can do other tricks as well, like for example, adding random delays to try and make the response flatter. A bit like you do with your subs...
I mean, your statement above is a bit like saying "I tried an automatic pilot for my car and it didn't get me there as fast as I can drive myself, therefore I avoid using GPS units."
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Right... and DRC can do other tricks as well, like for example, adding random delays to try and make the response flatter. A bit like you do with your subs...
I mean, your statement above is a bit like saying "I tried an automatic pilot for my car and it didn't get me there as fast as I can drive myself, therefore I avoid using GPS units."
I guess what I'm trying to say is that I want to have complete control over what gets changed and know what is getting changed. All in one units that aren't automatic are fine but of course have their place and limitations. Personally I do not use any eq but that's just me and my system.
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I like to have control too. I prefer not to use DRC the way that you do, with delays messing up the timing just to make the steady-state response look good. Because the latter can be easily corrected with... um, EQ :green:
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with delays messing up the timing just to make the steady-state response look good.
I only use delays on my two subs that are in the back of the room. It's really the proper way to do it from what I've been told by many pro audio guys. And it makes sense,...That's exactly how they do live events when there are many speakers within the same event.
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jtwrace, what are you using to give delay to rear subs output and how many milliseconds or feet of delay do you have dialed in?
As far as EQ of the front mains is concerned I only have 100 watts a channel of power available, even a 3dB boost is going to cause me to clip peaks. EQ could be applied to the rear sub as it has a 350 watt amplifier driving it but I don't currently have the ability to EQ only the feed to that sub.
Scotty
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jtwrace, what are you using to give delay to rear subs output and how many milliseconds or feet of delay do you have dialed in?
Currently a DCX. IIRC it's ~3ms on one and ~7ms on the other.
As far as EQ of the front mains is concerned I only have 100 watts a channel of power available, even a 3dB boost is going to cause me to clip peaks. EQ could be applied to the rear sub as it has a 350 watt amplifier driving it but I don't currently have the ability to EQ only the feed to that sub.
Scotty
I do not use nor need any eq on my mains.
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John, I am using Rhythmbox as my music player, it is the only one that I have found that allows gapless playback. There is an EQ plugin but it is fairly crude and the EQ would be applied across the board to all channels. I could maybe cut down humps with it if they happened to coincide with the center frequencies of the filters that are available.
Scotty
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jtwrace, if both subs are in the same plane on the rear wall, why have you used two different delay times?
Scotty
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jtwrace, if both subs are in the same plane on the rear wall, why have you used two different delay times?
Scotty
Because they're not on the same plane and they're not on the rear wall.
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I thought you were maybe using the CABS approach to optimizing the bass response in your room, my bad. Different locations mean different delays.
Scotty
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Different locations mean different delays.
Scotty
Yep