Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 424 - AVS Forum | Home Theater Discussions And Reviews
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post #12691 of 15449 Old 12-12-2014, 01:18 PM
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Quote:
Originally Posted by markus767 View Post
There's also something fishy about SEL. It should average over 1s but doesn't.
That is incorrect. SEL is the accumulated total sound energy over the measurement period, expressed as an equivalent constant level that would have the same energy if it lasted only one second. For more see http://www.bksv.co.uk/doc/BO0051.pdf
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post #12692 of 15449 Old 12-12-2014, 01:27 PM
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Quote:
Originally Posted by JohnPM View Post
That is incorrect. SEL is the accumulated total sound energy over the measurement period, expressed as an equivalent constant level that would have the same energy if it lasted only one second. For more see http://www.bksv.co.uk/doc/BO0051.pdf
I stand corrected and have been misinterpreting the very same paper you've linked:

"SEL is similar to Leq in that the total sound energy is integrated over the measurement period, but instead of then averaging it over the entire measurement period, a reference duration of 1s is used."

Markus

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post #12693 of 15449 Old 12-12-2014, 01:53 PM
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[quote=jim19611961;29854490]
Quote:
Originally Posted by randallhill View Post




Attachment 417554

This graph of yours clearly indicated 1/6th octave smoothing.
Yes, for the 5.0 speakers (FR/FL/CC/SL/SR)...in REW, I measure each 5.0 speaker separately using 1/6 smoothing, then I measure the dual subs without smoothing, the graph reflects 5.0 1/6 smoothing, dual subs no smoothing. I use REW with the simplified HDMI/UMIK-1/ASIO4ALL/Win7 Notebook multichannel HD audio setup.

AVR: Onkyo TX-NR3009 - Audyssey XT32
BD: Oppo BDP-103 - NAS - LenovoEMC - px2-300d 6TB
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Speakers: Infinity Interlude - IL40 Fronts, IL30 Surrounds, IL36C Center
Subs: Dual JBL - ES250P 12" 400W RMS
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post #12694 of 15449 Old 12-12-2014, 02:26 PM
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[quote=randallhill;29863698]
Quote:
Originally Posted by jim19611961 View Post
Yes, for the 5.0 speakers (FR/FL/CC/SL/SR)...in REW, I measure each 5.0 speaker separately using 1/6 smoothing, then I measure the dual subs without smoothing, the graph reflects 5.0 1/6 smoothing, dual subs no smoothing. I use REW with the simplified HDMI/UMIK-1/ASIO4ALL/Win7 Notebook multichannel HD audio setup.
randallhill,

Have you dealt with the large Center speaker sitting on the floor, which happens to be pointing towards your feet rather than your ears?

I think you can get an easy sound quality improvement by making a simple change.

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post #12695 of 15449 Old 12-12-2014, 02:27 PM
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[quote=AustinJerry;29856290]
Quote:
Originally Posted by jim19611961 View Post

Sorry, that was not clear.

Yes, thanks for your collective guidance...much appreciated!


So, based on your comments, I will need to re-post the SPL graphs with the correct FR axis limits and increments, with and without proper smoothing. In terms of the CC reflections, I understand that the CC FR will be an anomaly given my room constraints, I will however, measure again with REW with the CC angled up toward the MLP with no other obstructions in the way. Curious though, the dual subs waterfall graphs and spectrograms that I posted most recently, the graph limits that I used were the default settings, so, do the dual subs waterfall graphs with Audyssey On / Off represent fairly?


RE: Dual Subs Post-Audssey XT32 REW measurements...


The REW measurement settings for the dual subs were, FR - 20Hz-200Hz, 512K timing, -12dB sweep level, the "test" tab yielded -12.7dB "Level OK", the headroom was about 10dB. My noise floor using REW SPL meter with the UMIK-1, is about -44dB (z) and -57dB FS, my AVR's main volume was set at -15dB. The dual subs per Audyssey XT32 were manually set at 75dB to begin the calibration and left at that volume setting on the subs during the REW measurements. Post-Audyssey, the subs trim levels were both set at -2.0dB, the subs distances were set at S1(L) - 14.6' and S2(R) - 14.4'. The XO in the AVR was set at 40Hz for Fronts, CC and Surrounds. No AVR DSP was used during the REW measurements.

AVR: Onkyo TX-NR3009 - Audyssey XT32
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Subs: Dual JBL - ES250P 12" 400W RMS
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post #12696 of 15449 Old 12-12-2014, 08:43 PM
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Quote:
Originally Posted by LastButNotLeast View Post
Maybe you need to check the RS meter.





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post #12697 of 15449 Old 12-12-2014, 09:18 PM
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[quote=steveting99;29864730]
Quote:
Originally Posted by randallhill View Post

randallhill,

Have you dealt with the large Center speaker sitting on the floor, which happens to be pointing towards your feet rather than your ears?

I think you can get an easy sound quality improvement by making a simple change.

Actually, I just re-measured the CC with REW, 1.) Flat on Floor, 2.) 12.5 degrees tilted up and 3.) 22.5 degrees tilted up. Surprisingly, tilting the angle towards the MLP (UMIK-1) didn't produce the expected results. Audyssey XT32 calibrated, Audyssey On, 40Hz XO, no DSP, and no obstructions, i.e., clear path from CC to MLP.
The first graph shows Audyssey with on all three angles, zero, 12.5 and 22.5 degrees with no obstructions, the other graph shows zero degrees "flat" on the floor with Audyssey on and off, with no obstructions.
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AVR: Onkyo TX-NR3009 - Audyssey XT32
BD: Oppo BDP-103 - NAS - LenovoEMC - px2-300d 6TB
HDTV: Panasonic Plasma TC-P50G10
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Subs: Dual JBL - ES250P 12" 400W RMS
Turntable: B&O Beogram 1600 - REW Mic - UMIK-1 USB
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post #12698 of 15449 Old 12-12-2014, 09:58 PM
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^ randallhill,

Was the large center speaker still on the floor when you carried out the measurements?

Can you post the ETC graph with a 20ms window? Look at a the peaks where the reflections are happening.

Maranatz SR-7009, Oppo BPD-93, MTV 7000D, aTV, WDTV Live, Harmony 650 remote, KEF E301+T101, MiniDSP(2x4) & 10x10HD, Emotiva 2xXPA-5 (Gen2), Rythmik 2xF12G+2xF8, HiMedia Q16, LG 55EC9300.
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post #12699 of 15449 Old 12-12-2014, 10:36 PM
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Quote:
Originally Posted by steveting99 View Post
There's the problem with 1st reflections from your large center speaker bouncing off the floor and interfering with the direct signal going to your listening position. Try 'lifting' (via a stand) the large center speaker off the floor and point the tweeter to the Main Listening Position (MLP) and preferably where the ears are normal at. Unfortunately this may mean re-doing an Audyssey re-calibration and run REW again.

As pointed out by a few AVS members, please present the REW graphs in the accepted format for everyone. This is to ensure we're all on the same page and can provide guidance based on known standards. Re-read the wonderful guide provided by Jerry again.

Edit: What is the noise floor of your room in dB? Generally you would want to measure +40dB above the noise floor to get the decays shown in the waterfall and spectrograms. I.e. if the noise floor is 50dB, the average SPL should be around 90dB.

Thanks again for your feedback!


I re-measured in REW and corrected the graphical presentations with 5dB increments with the appropriate axis limits. The noise floor (relative silence at the MLP), measured using the REW SPL meter, is approximately -40dB(z) and 52dB FS, respectively.


In REW I measure each 5.0 (FL/FR/CC/SL/SR) speaker separately (HDMI/UNKI-1/Laptop/AVR), then I measure the dual subs separately. The baseline REW measurement parameters using the loaded UMIK-1 calibration file, (mic sensitivity, 9.6dB) are as follows:


01.) In AVR - Audyssey On (or Off) - XO is set post-AudysseyXT32, no DSP, no DV, no DEQ, no manual level or EQ adjustments
02.) AVR volume knob set to -15dB
03.) Win7 HDMI HD audio volume controls have no effect on the levels in REW, but it's at 50%
04.) the frequency ranges used is 20Hz-20kHz for 5.0 speakers and 20Hz-200Hz for the dual subs
05.) the sweep level is -6dB FS
06.) length = 512K
07.) sweeps =1
08.) the "check levels" for all 5.0 speakers fall in the -24dB level and -16dB level for the dual subs, where REW says "Level OK"
09.) after each measurement of the 5.0 speakers the "Headroom" ranged from +8.0 to +9.4, the dual subs were +10 headroom
10.) set the graph's axis dB limits with a minimum of 5dB increments
11.) set the 5.0 speakers with 1/6th smoothing, set the dual subs with no smoothing


See attached new measurements that reflect appropriate graph limits, the only changes were 1.) I removed the obstructions between the speakers and MLP and 2.) measured the CC, a.) flat on the floor, b.) with a 12.5 degree angle tilted up toward the MLP and c.) with a 22.5 degree angle tilted up toward the MLP.
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AVR: Onkyo TX-NR3009 - Audyssey XT32
BD: Oppo BDP-103 - NAS - LenovoEMC - px2-300d 6TB
HDTV: Panasonic Plasma TC-P50G10
Speakers: Infinity Interlude - IL40 Fronts, IL30 Surrounds, IL36C Center
Subs: Dual JBL - ES250P 12" 400W RMS
Turntable: B&O Beogram 1600 - REW Mic - UMIK-1 USB
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post #12700 of 15449 Old 12-12-2014, 11:15 PM
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Quote:
Originally Posted by 3ll3d00d View Post
Interestingly, though probably just coincidence, I find that audyssey produces a sub trim a few dB down on where I dial it in by hand. I believe it is because the surrounds are a few dB less capable so it brings everything else down to give them headroom. I don't listen at reference so I don't care about those 2-3dB and hence set levels according to what the mains/sub want not the surrounds.
In my case, I have just veirified that Audessey set my subs trim 5db lower than what it should be. The REW SPL meter were showing 70db (my newly purchased Radio shack digital SPL meter showed 67-68db) when I ran my receiver test tone at 0MV. Perhaps, this is the reason almost everyone bumps the sub trim up after Audessey.

Quote:
Originally Posted by 3ll3d00d View Post
your graphs say your system is off by a few dB, if I were you I'd run a full range sweep at -30 (MV at -30 and REW sweep at full strength) on a main channel, smooth it and check that your measurement is centred on 75dB (or use the RTA method with 1/1 octave smoothing)
Here is my left speaker + subs full range graph at -30MV. It looks like it is centered at ~67db. All speakers were verified with both REW SPL meter and RS SPL meter from running avr test tone at 0MV. REW spl meter showed 77db, RS SPL meter showed 79db from MLP for ALL speakers. Why my graph is centered at ~67db is where I need help? Thanks



Here is the compression sweeps and distortion graph for my highest sweep. Please explain the distortion part as I have no clue what or where to look. Thanks.


I still do not reach 115db at 0MV. Not sure why?



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Last edited by tvuong; 12-13-2014 at 06:21 AM.
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post #12701 of 15449 Old 12-12-2014, 11:21 PM
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Quote:
Originally Posted by AustinJerry View Post
Well, I follow this thread pretty closely as well, from the day it started, and I don't recall such a conversation. If you find a post, please reference it. If not, don't worry about it.
I cannot find that post but I just verified myself. My noise floor level from RTA is as follow:
With sense factor line: ~ 52db
Without sense factor line: ~ 34db
Does it matter?
Here is the exact graph from my directly above post with sense factor versus manual mic cal


There is a bit db difference probably due to my RS spl meter fluctuated back and forth between 78, 79,80, 81 when I calibrated my Umik-1
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post #12702 of 15449 Old 12-12-2014, 11:39 PM
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Quote:
Originally Posted by steveting99 View Post
^ randallhill,

Was the large center speaker still on the floor when you carried out the measurements?

Can you post the ETC graph with a 20ms window? Look at a the peaks where the reflections are happening.
Yes, the large CC (unfortunately, will be permanently placed flat on the floor, the HDTV placement prohibits this) so, for grins, I angled the CC upward toward the MLP at 12.5 degrees and 22.5 degrees. Flat on the floor position appears to be working better than angling it up. The CC placement seems difficult at best, the CC would have to be between 34"-44" off the floor at ear height, meaning the HDTV would have to be positioned at or above ear level from a sitting couch position. I created a few graphs of the CC with Audyssey on and flat on the floor and tilted upward toward the MLP with no obstructions to the MLP. Maybe it will help in understanding the nature of the fixed flat floor position of the CC?
The impulse graph gave me headache...LOL
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AVR: Onkyo TX-NR3009 - Audyssey XT32
BD: Oppo BDP-103 - NAS - LenovoEMC - px2-300d 6TB
HDTV: Panasonic Plasma TC-P50G10
Speakers: Infinity Interlude - IL40 Fronts, IL30 Surrounds, IL36C Center
Subs: Dual JBL - ES250P 12" 400W RMS
Turntable: B&O Beogram 1600 - REW Mic - UMIK-1 USB
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post #12703 of 15449 Old 12-13-2014, 02:02 AM
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Quote:
Originally Posted by tvuong View Post
Here is the compression sweeps and distortion graph for my highest sweep. Please explain the distortion part as I have no clue what or where to look. Thanks.


I still do not reach 115db at 0MV. Not sure why?
Generally speaking there is some debate about the absolute audibility of distortion at low frequencies. However what isn't up for debate is that high levels of distortion are a clear sign of impending distress for your sub, in my experience you are in the danger zone when you by past 10% and then really clearly in trouble at 30%. This percentage refers to how much quieter the distortion is vs the fundamental tone, 10% distortion = -20dB and 30% = -10dB.

When you run a sweep then REW extracts the harmonic distortion components up to the max frequency of the sweep divided by the harmonic, i.e. if you run a sweep to 120Hz then you only get 2nd harmonic to 60Hz, 3rd to 40Hz and so on. Therefore you need to run that sweep to a higher frequency to get a good view across the subwoofer passband. Ideally you'd go direct to the subwoofer with a full range signal but not sure how you'd do that with audyssey on, perhaps just upping the crossover to 250Hz would be sufficient though as this would at least give you 3rd harmonic all the way through and 4th harmonic down to 60Hz.

I mention 60Hz as you seem to have a clear spike in the distortion there upto ~5%, this must be audyssey boosting. You can then see you reach ~10% distortion at ~16Hz so this is getting the limits of your system at reference. Note that 3rd harmonic is escalating rapidly under 20Hz, AIUI 3rd harmonic is predominantly mechanical non linearity (i.e. magnet losing control of driver aka reaching xmax) so this shows that ~12Hz or so sees your drivers losing it.

This suggests that the limit of your system is ~105dB at 12Hz but >110dB at 20Hz therefore when it comes to boosting the low end (with your LS in jriver) then you need to decide how much you want to trade extension for output. If you wanted to be flat to 12Hz then you have to accept 105dB as your limit and not go beyond that. Alternatively if you wanted to roll it off below 20Hz then you can accept you have more output on tap (or more headroom hence lower distortion given you listen at -10) & boost harder to that point. Another alternative is to add more/bigger subs
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post #12704 of 15449 Old 12-13-2014, 02:05 AM
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Quote:
Originally Posted by tvuong View Post
Here is my left speaker + subs full range graph at -30MV. It looks like it is centered at ~67db. All speakers were verified with both REW SPL meter and RS SPL meter from running avr test tone at 0MV. REW spl meter showed 77db, RS SPL meter showed 79db from MLP for ALL speakers. Why my graph is centered at ~67db is where I need help? Thanks


The img tag is wrong, no pic there. Can you repost?
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post #12705 of 15449 Old 12-13-2014, 06:22 AM
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Originally Posted by 3ll3d00d View Post
The img tag is wrong, no pic there. Can you repost?
Not sure what happened there but here it is. I also fixed my original post. Thanks.


Last edited by tvuong; 12-13-2014 at 06:50 AM.
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post #12706 of 15449 Old 12-13-2014, 08:27 AM
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Quote:
Originally Posted by 3ll3d00d View Post
Generally speaking there is some debate about the absolute audibility of distortion at low frequencies. However what isn't up for debate is that high levels of distortion are a clear sign of impending distress for your sub, in my experience you are in the danger zone when you by past 10% and then really clearly in trouble at 30%. This percentage refers to how much quieter the distortion is vs the fundamental tone, 10% distortion = -20dB and 30% = -10dB.

When you run a sweep then REW extracts the harmonic distortion components up to the max frequency of the sweep divided by the harmonic, i.e. if you run a sweep to 120Hz then you only get 2nd harmonic to 60Hz, 3rd to 40Hz and so on. Therefore you need to run that sweep to a higher frequency to get a good view across the subwoofer passband. Ideally you'd go direct to the subwoofer with a full range signal but not sure how you'd do that with audyssey on, perhaps just upping the crossover to 250Hz would be sufficient though as this would at least give you 3rd harmonic all the way through and 4th harmonic down to 60Hz.

I mention 60Hz as you seem to have a clear spike in the distortion there upto ~5%, this must be audyssey boosting. You can then see you reach ~10% distortion at ~16Hz so this is getting the limits of your system at reference. Note that 3rd harmonic is escalating rapidly under 20Hz, AIUI 3rd harmonic is predominantly mechanical non linearity (i.e. magnet losing control of driver aka reaching xmax) so this shows that ~12Hz or so sees your drivers losing it.

This suggests that the limit of your system is ~105dB at 12Hz but >110dB at 20Hz therefore when it comes to boosting the low end (with your LS in jriver) then you need to decide how much you want to trade extension for output. If you wanted to be flat to 12Hz then you have to accept 105dB as your limit and not go beyond that. Alternatively if you wanted to roll it off below 20Hz then you can accept you have more output on tap (or more headroom hence lower distortion given you listen at -10) & boost harder to that point. Another alternative is to add more/bigger subs
Thanks for the detail explanation . So, what adding a third FV15hp in the rear gives me? I do want low extension and will use a +6db LS around 30hz but without running subs hot this time. I thought I was running my subs 5db hot but after verifying, Audessey set my subs 5 db lower than 75db manual calibration. The 0MV graph plus 6db LS gain at 30hz will be what I listen to at -15 to -10MV. Thanks.
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post #12707 of 15449 Old 12-13-2014, 08:35 AM
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Not sure what happened there but here it is. I also fixed my original post. Thanks.

I am not sure what the problem is exactly. Are you expecting that graph to be at about 75dB? What exactly is playing there? One main speaker plus the sub? what exactly are the mv and rew settings (inc output level)?
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post #12708 of 15449 Old 12-13-2014, 09:00 AM
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^^ that is my left speaker plus subs full range measured at -30MV. I thought you said to try that to see my graph is centered at 75db? Sorry but I don't understand inc output level? The blue graph is at the level Aud set, the green one is with +5 subs trim increased in compensation for Aud sub lower level setting.
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post #12709 of 15449 Old 12-13-2014, 09:09 AM
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^^ that is my left speaker plus subs full range measured at -30MV. I thought you said to try that to see my graph is centered at 75db? Sorry but I don't understand inc output level? The blue graph is at the level Aud set, the green one is with +5 subs trim increased in compensation for Aud sub lower level setting.
I mean the output level of the sweep in rew. Is it at -3dBFS?
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post #12710 of 15449 Old 12-13-2014, 09:10 AM
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I mention 60Hz as you seem to have a clear spike in the distortion there upto ~5%, this must be audyssey boosting. You can then see you reach ~10% distortion at ~16Hz so this is getting the limits of your system at reference.
Baby steps: from where are you getting those percentage numbers?

Did you really need to quote that entire post in your reply?
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post #12711 of 15449 Old 12-13-2014, 09:13 AM
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Baby steps: from where are you getting those percentage numbers?
Difference between the level of the fundamental and the level of the harmonic then converted to a percentage in the usual way (http://www.sengpielaudio.com/calculator-thd.htm)
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post #12712 of 15449 Old 12-13-2014, 09:22 AM
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I mean the output level of the sweep in rew. Is it at -3dBFS?
It was at whatever default. I will try at -3dBFS. Can you explain the reason for this? Thanks.
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post #12713 of 15449 Old 12-13-2014, 09:24 AM
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It was at whatever default. I will try at -3dBFS. Can you explain the reason for this? Thanks.
-3 is a full strength sweep, if the mv is at -30 then you will only see 75dB if you play a full strength sweep otherwise it is 75 minus however far below -3 you are. I don't recall what the default is but if you were at -12 say then I would say this looks about right.

This would affect your compression sweeps too BTW.

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post #12714 of 15449 Old 12-13-2014, 09:41 AM
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^
75?

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post #12715 of 15449 Old 12-13-2014, 09:44 AM
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^
75?
Approximately. I know you would be aiming for 73 with band limited pink noise on a main speaker but I forget exactly what the target level is with a sweep (ie whether it is peak or RMS level, my memory says peak but I may well be wrong). Not 67 anyway

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Doesn't compute. Reference is defined 85dBSPL C with pink noise -20dBFS RMS.

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post #12717 of 15449 Old 12-13-2014, 09:54 AM
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What doesn't compute? He wants to know to know what level to expect with a sweep when the MV is at -30.
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Now does compute

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post #12719 of 15449 Old 12-13-2014, 10:28 AM
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-3 is a full strength sweep, if the mv is at 0 then you will only see 75dB if you play a full strength sweep otherwise it is 75 minus however far below -3 you are. I don't recall what the default is but if you were at -12 say then I would say this looks about right.
I think it was at -12dBSF when measured. I measured at -30MV and my left and subs graph is centered about 66-67db. You lost me when mentioning 'if the mv is at 0 then you will only see 75dB if you play a full strength sweep'

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This would affect your compression sweeps too BTW.
in what way? What is the correct way to run compression sweeps?
Thanks.

Last edited by tvuong; 12-13-2014 at 10:38 AM.
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post #12720 of 15449 Old 12-13-2014, 10:45 AM
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I think it was at -12dBSF when measured. I measured at -30MV and my left and subs graph is centered about 66-67db. You lost me when mentioning 'if the mv is at 0 then you will only see 75dB if you play a full strength sweep'

in what way? What is the correct way to run compression sweeps?
Thanks.
typo, I meant "mv is at -30" (I edited my previous post). If it was at -12dBFS & -30 MV then 66-67dB looks bang on to me.

As to the compression sweep Q, you were confused over what level you should be getting and were thinking that MV=0 will automatically give you peak reference output. My point is that it depends on the REW output level so unless you get that right then youwon't get the output you were expecting purely because of a method error.
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