I have a recording session today and tomorrow, so I don't have much time to analyze that properly yet, but on the calibration you went from the sublime to the ridiculous! It's saying that you did that test at around 120 dB :!: :shock: You sure got a great deal on those speakers, if they can produce 120 dB like that.... :) Are you sure you calibrated REW according to your sound level meter? You compared them while playing pink noise, and adjusted REW to match the reading on your hand held meter, with both of them set on "C" and "slow"?
Also, the curves are still different, and not making a lot of sense. In some places, the combined signal (both speakers) is 10 dB quieter than either of the individual speakers by itself! :shock: I don't know how to explain that at all.... Negative acoustic energy? :) They would have to be grossly out of phase to do that, but they don't seem to be: the phase is pretty much the same for all readings.
I'll try to take a closer look on the weekend, but I'm just not getting what is going on there. I would imagine that the stereo image is all over the place like that, and skewed different ways at different places on the spectrum... Something, either the speakers themselves or something in the room (perhaps close to the speakers) is skewing things, big time. Maybe some thing physical, like asymmetric furniture close to the front of the room? Dunno...
- Stuart -
Dog + Bear Studio build
Originally posted at johnlsayers.com, topic 17575.
I even read the 'instructions' on the calibration:) I'll take another look at it and figure out what I'm doing wrong. There's no way it was at 120db.Are you sure you calibrated REW according to your sound level meter? You compared them while playing pink noise, and adjusted REW to match the reading on your hand held meter, with both of them set on "C" and "slow"?
Hmmm, front of the room is very symmetrical. The only things that are out of whack are the rack gear which is behind the listening position on the left and a couple of single seater couches which are on the back wall middle and back wall right.Something, either the speakers themselves or something in the room (perhaps close to the speakers) is skewing things, big time. Maybe some thing physical, like asymmetric furniture close to the front of the room?
I'll put the test I did from a while ago in the dropbox again Stuart. It was done a few months ago when I'd just finished the acoustic treatment for the control room. You did comment on it back in the thread and I don't think you mentioned this kind of difference with the L and R signals. The only things that have changed in the room since then are the fabric on the walls and the furniture, desk, console etc. Maybe I'm doing something really screwy with REW somehow as I'm using the new console for the tests which I've only had for a week or so.Also, the curves are still different, and not making a lot of sense. In some places, the combined signal (both speakers) is 10 dB quieter than either of the individual speakers by itself!
https://dl.dropboxusercontent.com/u/416 ... tereo.mdat
here's the link to the older test Stuart, done in April this year. Let me know what you think of the correlation in the data for this. If these look okay for L and R then I'll switch back to using the Fireface which was what I was using initially.
Those curves are a lot more believable: The average around 75 dB, which is OK for REW tests. The left and right curves are not identical, but also not so different as to raise eyebrows, and the "both speakers" curve is about 6 dB higher than the other two curves across most of the spectrum, or at least up to about 2.5 kHz. Above that it starts getting weird too: I guess I didn't notice back then because I was looking at the low end, where the modal issues are, and never looked at the top end. But this is even more confusing, since the curves don't mach very well: In other words the original L curve is a somewhat different from the old L curve. Is the mic in the exact same location in the room as it was for the original tests? Even small changes in the position of the mic can show up as large differences in the curves. I really wish I could figure out what is going on here.... Very confusing... - Stuart -here's the link to the older test Stuart, done in April this year.
Original test: Galaxy CM140 SPL meter through a Fireface 800 Most recent tests: U89 through a Midas Venice F24. And the mic position will also be completely different. So the two tests can't be A/B'd. I'm a bad man :P The Galaxy meter is playing up and adding it's own signal to the reading so i've stopped using it till I can get it fixed. I'm using the U89 for the more recent tests as it has the least colouration of the mics that I have. I loaded up the old files more to see if the same 'oddities' were showing up in the original. It seems that they aren't as extreme as my more recent measurments so perhaps it's my REW technique thats not so good.In other words the original L curve is a somewhat different from the old L curve. Is the mic in the exact same location in the room as it was for the original tests?
Where are you in teh room while running the tests? Don't forget that your body affects the acoustics of the room somewhat... That could be affecting the readings, to a certain extent. - Stuart .perhaps it's my REW technique thats not so good.
Is there some way of running REW without being in the room? I was sitting to the right of the mic when doing those tests. perhaps behind would be better.Where are you in teh room while running the tests?
When you wired your live room, did you run CAT-5 cable along with the audio stuff? If so, you could use that with a KVM extender to get your keyboard, video monitor and mouse into the other room, and run REW from there.Is there some way of running REW without being in the room?
It's possible, for sure. What I try to do is to crouch down on the floor behind the chair or even under the desk, and run the test from there. I'm not convinced that this is causing all of your problem, but it might be causing come of it. And it's worth trying another test with you out of the way as much as possible, or at least located symmetrically in the room. - Stuart -I was sitting to the right of the mic when doing those tests. perhaps behind would be better.
yep. I'll look into the extender option and see what I come up with but for the mean time i'll have to be hands on.When you wired your live room, did you run CAT-5 cable along with the audio stuff?
See this is why i'm here. To get these inside and secret tips from the professionals 8) I can't wait for someone to walk in the control room while i'm sitting under my desk with the laptop. I'll just have to explain that it's all for a scientific cause before they get the straight jacket out :lol:What I try to do is to crouch down on the floor behind the chair or even under the desk, and run the test from there.
:lol: You can complete the picture for them by opening your eyes really wide and wild-looking, then babbling incoherently about the voices in your head that made you hide under the table... :) - Stuart -'ll just have to explain that it's all for a scientific cause before they get the straight jacket out
hi steve, i have decided to use the soundscreen 3.1 and the gg glue sealant and compound between 2 layers of 16mm fyrecheck, i was wondering what type of backer rod you could recommend using?? around the outside of each wall, joins, maybe a 5mm gap between sheets and the floor and 5mm between wall joins,
thanks Neil
hey Neil, I answered your question back over in your thread to keep all your information in one spot. That way if someone else is running through your build in the future they'll be able to keep track of it :D
phew....the last few months have been way over the top with work and many things have fallen by the wayside. This thread included :(
for starters, a belated happy new year to all and may everyones studio building/tweaking and designing be fruitful this year!!
It looks like the last thing I was up to here was doing some REW tests to explain some odd room modes. I'll have to get back on board with that and hopefully post some more useful results from REW. I'am however starting to suspect that it may be a problem with the monitors :shock: unless i'm really screwing up the REW tests.
There's a couple of small toggle switches on the back of those KRK V8's which adjust the freq at which the high boost/cut/flat response and low end roll off occur. It's possible (not that I want to think about it) that one got accidently knocked down or up during installation. That's about the only thing I can think of as the room symmetry is fine (according to me) and I think my REW technique is okay. I'll persevere with the REW tests as getting the monitors out for a look is something I can't even contemplate at the moment as I'm totally brain-fried after the last few months!
Oh COOL! Steve's back!!! :yahoo:
- Stuart -
yep, I'm certainly glad to be back Stuart :D It's not at all on the topic of building studios and it's probably common knowledge to anyone who runs thier own business, but if you prioritise work above just about everything else, you know what you get....work!
Hopefully a bit of a more even keeled year this year given that the studio is done, which is probably relevant to anyone who is doing a build. The amount of time, effort and thought that goes into building a quality studio is a significant drain on your personal resources (not to mention financial) and can really impact on your time if you don't plan accordingly. I reckon that I underestimated my build by about 50-60% in terms of time and difficulty. I'd be interested to hear if any other completed/in progress builds agree with that kind of figure.
Either way, as long as you're ending up with the right souding room then you've had a win :yahoo:
Very true Steve - people always underestimate how difficult it is to put a studio together., especially builders who are used to building square room homes.
good point John, and conversely, when I do the reno on our house I'll be using a lot of the techniques that I picked up from building the studio ie: 16mm plaster, high density insulation, air gaps sealed etc. I'm sure most builders would say to me "you don't need to do all that crap on a house". But I sure will be, given that the outdoor temps in Victoria were between 40-45 degrees all last week and the studio sat at around 20 degrees without the air-con on. 8)especially builders who are used to building square room homes.
Tell them - I'm building a recording studio - and that's the way it is.
Sooooo, I'm finally back in REW mode and I think I've finally figured out how to use it properly. Here's a few screen shots from my most recent test. L monitor is red and R monitor is yellow. There's a fair bit of defference in the L and R readings, (especialy the top end!!!) which I don't believe has to do with the room symmetry.
I'm really starting to think I've got an issue with the monitors themselves :cry: Especially that difference in roll off at the top. The monitors were re-tweeted a few years ago so I'd like to think it isn't the tweeters themselves. I could probably get the tweeters out and swap them over to do a test and see if I get the same kind of roll off on the tops.
If it's the roll off switches at the back of the monitor that have been tweaked during installation then it's a whole other world of pain to get the monitors back out of the soffits :shock:
well, it looks like I can rule out a dodgy tweeter. swapped them over and had the same results. The mic, levels etc have been changed between the first test and this one so they can't be A/B'd directly, but it's giving me the same roll off on the right monitor.
I don't want to take them out but it might be the only way to be sure.
Not necessarily. That type of response is typically what you see when measuring rooms: It's likely to be room-related, rather than speaker related. It might even be some type of phase cancellation that is happening in the highs at the specific location where the mic is. Use REW to measure with just just one speaker active, with the mic in several different locations around the room, and compare. If they all show the same roll-off, then I'd suspect tweeters. But if they all show different roll-off, then it's probably the room. If you post the actual MDAT file, or a link to it, then I'll download that and take a look. - Stuart -I'm really starting to think I've got an issue with the monitors themselves :cry: Especially that difference in roll off at the top.
great idea Stuart (as always :D ). hopefully i'll get a bit of time later this week to do this test and post results.Use REW to measure with just just one speaker active, with the mic in several different locations around the room, and compare. If they all show the same roll-off, then I'd suspect tweeters. But if they all show different roll-off, then it's probably the room.
since this is testing for high frequencies, it is imperative that the room should be identical for each test. The best way to achieve that is for you to NOT be in the room when the test is running, or your body itself could affect the readings. Fortunately, there's a new feature in the latest versions of REW that allows you to set a delay from the time you hit the "Start" button until the test actually starts, so you can get out of the room, shut the door, and a few extra seconds for things to calm down inside. So I'd suggest that you use that feature, and leave the room every time. - Stuart -hopefully i'll get a bit of time later this week to do this test and post results.
great, thanks for the tip Stuart, that's genius :D I'll update my version.Fortunately, there's a new feature in the latest versions of REW that allows you to set a delay from the time you hit the "Start" button
I finally got round to doing some serious testing of the monitors themselves and it's definitely a hardware problem :roll:
A/Bing the monitors with the same signal after removing them from the soffits reveals a top end roll off in the L monitor which I can't account for as the high and low shelf switches at the back are flat on both units. Adjusting the monitor in question by putting the +1db HF boost on and winding it up by 2-3 db above the other one certainly feels a lot more balanced.
looks like it's a trip to the doctors for them when I can get around to it :cry: