Steve Thomas Posted October 9, 2008 Share Posted October 9, 2008 Now I haven't got all the facts on this as this has come from our keyboard player...but, we are a live 5 piece covers band that now have a tidy rig of Martin Audio Blackline, L Gruppen amps and a newly aquired KT 360 eq. We play anything from 100-300 people venues and they vary from hotels, to clubs, to Marquees. My keyboard player brings a laptop to gigs and has been able to source some kind of spectrum analyzer programme. He believes the only issue we have is how to generate a signal back to his laptop to measure the room. His Laptop can be interfaced by a mini phono ( I think of them as home stereo audio conections) but is there a certain type of microphone needed to enable this programme to work. Sorry if we're wide of the mark but you know what boys and toys are like!! Link to comment Share on other sites More sharing options...
berry120 Posted October 9, 2008 Share Posted October 9, 2008 I'd actually question why you need a spectrum analyser? The program will work with any signal you send to it (as long as it's been coded properly) so you could just run it off a spare aux or output from the desk. In terms of mics, the frequency response you get on the spectrum analyser will depend on the response of the mic so you'll probably want something with as wide a response as possible. But unless I'm grabbing the wrong end of the stick completely it'll "work" with anything. Link to comment Share on other sites More sharing options...
revbobuk Posted October 9, 2008 Share Posted October 9, 2008 There are plenty of omnidirectional measurement mics around. Almost all are condenser mics, so will need powering - that's one issue. A second issue is that you won't have a clear idea of the frequency response, precise gain, or phase response of the laptop's audio input, so you'll need something precise to calibrate it against. You can deal with some of these issues with a good external sound card, which will have phantom powering and a predictable frequency response. But you will still need to calibrate against something. If this is just 'boys toys', then the Behringer ECM8000 is cheap and pretty good. Link to comment Share on other sites More sharing options...
Steve Thomas Posted October 9, 2008 Author Share Posted October 9, 2008 Berry, I think you are grabbing the right end of the stick. As to why its needed, to be fair it will not always be needed, but in certain venues it would be nice for something other than our ears to analyse the venue and then make the adjustments via the graphic.What type of mic would you say has a wide response (is it a normal vocal mic or something else) and yes we could feed it from an aux from the desk. Thanks in advance. Link to comment Share on other sites More sharing options...
soundo26 Posted October 9, 2008 Share Posted October 9, 2008 If you want to use a spectrum analyser to measure the room & line up the PA then you will need a reference microphone as stated by revbobuk. there is nothing to be gained by taking a line signal from your source, this will not measure the room at all! If you just want it to look cool then you could supply any input to it from the desk or source and you'll have lots of dancing lines to impress the audience with, but I'd suggest you find out what you need to do first as that would be a bit of a waste! Link to comment Share on other sites More sharing options...
Steve Thomas Posted October 9, 2008 Author Share Posted October 9, 2008 If you want to use a spectrum analyser to measure the room & line up the PA then you will need a reference microphone as stated by revbobuk. there is nothing to be gained by taking a line signal from your source, this will not measure the room at all! If you just want it to look cool then you could supply any input to it from the desk or source and you'll have lots of dancing lines to impress the audience with, but I'd suggest you find out what you need to do first as that would be a bit of a waste! No, it's nothing to do with looking cool (too old for that :D ) and also the plan is to measure the room at souncheck adjust accordingly...and that's it. If the laptop thing wouldn't work then when funds permit we would probably look at the Phonic PAA3. Link to comment Share on other sites More sharing options...
Rob_Beech Posted October 9, 2008 Share Posted October 9, 2008 From experience the best Spectrum analyser and RTA device is on the side of your head. An external sound card and a reference mic (Audix do one that's moderately priced, although the Behringer one at about £30 is more than adequate. Calibration is another issue, so a device to do this would also be required. The cost can quite easily mount, I'm not entirely sure what benefit you'd see from this. It's potentially a nice feature to have but I would always trust my ears. Link to comment Share on other sites More sharing options...
Stan Hope-Streeter Posted October 9, 2008 Share Posted October 9, 2008 Like Rob, I would advise caution when using a PC audio spectrum analyser. Unless you have a good background in acoustics you are more likely to be misled by it than to find it helpful. Judging by your equipment list, you appear to be a discerning listener. Your ears will tell you a lot more than a simple analyser, especially if you can learn what pink noise really sounds like (go up into the hills and listen to a large waterfall and commit the sound to memory) It's a big enough problem with experienced FOH engineers - some of them with major bands - regularly making fools of themselves with SMAART. There is a very steep learning curve associated with acoustical measurement systems and they are nowhere near as simple as they might appear. The most important thing is to understand their limitations. By all means give it a try, but do NOT let the results persuade you of anything that conflicts with what your ears tell you. Link to comment Share on other sites More sharing options...
Simon Lewis Posted October 9, 2008 Share Posted October 9, 2008 If the PC analyser is a simple real time analyser, then I'd suggest it's not really too useful, and can be misleading. Even the suppliers of such programmes will "helpfully" suggest you fill the room with pink noise, hack away at the graphic until the RTA display looks flat. Then you'll listen to some music.... and wonder why it sounds terrible! Dual channel FFT analysers such as SMAART do a better technical job, but you still need a fair amount of understanding of both electroacoustics and the analysis programme to make sense of the squiggly line on the PC. If this is all for 'fun', then by all means buy the Behringer measurement mic, and get a low cost USB sound card (the PC sound card won't really be up to it). You will get some interesting read outs, but don't let the pretty lights convince you of something that your ears don't agree with... Simon edit - almost identical response posted above... must type faster! Link to comment Share on other sites More sharing options...
drsound Posted October 9, 2008 Share Posted October 9, 2008 Just a quick note of caution that's already been alluded to. Different types of software and hardware use different algorithms to measure the response, some of which are more "accurate" than others. Please don't shoot me down in flames as this is just a thought from my days of studying communications theory (Stremmler wrote the book if anyone wants to buy it!!). With any digital system you aren't actually producing pink noise and measuring what the room does. Instead you are producing a sample that approximates pink noise using a pseudo-random algorithm and then measuring slices of the room sound as sampled by your input card. And here is the crux as I suspect it might be. Unless you have some way of synchronising the clock of the source and measurement, there's a chance the two will be totally mismatched and result in very odd and inconsistent measurements. This isn't usually a problem with all-in-one hardware devices as they use a master clock to sync everything up. Even so, I've found the dbx system built into the Driveracks to be pretty useless. Oddly the old Behringer Ultracurve one got me out of a few tricky situations in theatres. As I said, I might be totally wrong. If anyone's interested a google of "Nyquist's theory" should yeild some information. I'd stick with the common theme and use your ears. It's not by mistake that a large number of engineers have a load of "favourite" tracks that they use to set up the rig. Having said that, we all still manage to get it wrong on occasion. Link to comment Share on other sites More sharing options...
Steve Thomas Posted October 9, 2008 Author Share Posted October 9, 2008 Just a quick note of caution that's already been alluded to. Different types of software and hardware use different algorithms to measure the response, some of which are more "accurate" than others. Please don't shoot me down in flames as this is just a thought from my days of studying communications theory (Stremmler wrote the book if anyone wants to buy it!!). With any digital system you aren't actually producing pink noise and measuring what the room does. Instead you are producing a sample that approximates pink noise using a pseudo-random algorithm and then measuring slices of the room sound as sampled by your input card. And here is the crux as I suspect it might be. Unless you have some way of synchronising the clock of the source and measurement, there's a chance the two will be totally mismatched and result in very odd and inconsistent measurements. This isn't usually a problem with all-in-one hardware devices as they use a master clock to sync everything up. Even so, I've found the dbx system built into the Driveracks to be pretty useless. Oddly the old Behringer Ultracurve one got me out of a few tricky situations in theatres. As I said, I might be totally wrong. If anyone's interested a google of "Nyquist's theory" should yeild some information. I'd stick with the common theme and use your ears. It's not by mistake that a large number of engineers have a load of "favourite" tracks that they use to set up the rig. Having said that, we all still manage to get it wrong on occasion. As always guys, thanks for all the valuable insight and contribution to this thread. Link to comment Share on other sites More sharing options...
Simon Lewis Posted October 9, 2008 Share Posted October 9, 2008 David, The "single ended" systems (MLSSA etc.) use a maximum length sequence signal, and by windowing the impulse response a psuedo anechoic measurement can be made. Furthermore, the room impulse response can be determined. Systems such as Smaart are based on a dual channel FFT, and use a measurement channel aligned (via a software tool) to a reference channel. The test signal is sommon to both channels, and any variations in the measurement channel path will show up as variations in the system's frequency and phase response. Consequently, as long as the signal is reasonably broadband, one can use pink noise, or even the music of the concert as the test signal. Again, by careful selection of the FFT window, something of a pseudo anechoic response may be realised. In both cases, the problems you highlight are overcome. The fatal drawback of RTA based systems is that they are time blind, cannot window and cannot generate an indication of measurement data quality. Simon Link to comment Share on other sites More sharing options...
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