Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 523 - AVS Forum | Home Theater Discussions And Reviews
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Old 08-10-2015, 07:18 AM
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Quote:
Originally Posted by AustinJerry View Post
Perhaps someone else has a similar set of measurements so we can see if this is an REW anomaly? In the meantime, I view it as a curiosity, not a concern. Care to make a guess why what you are describing is occurring?
I agree its not a concern. A curiosity.

Here I did 2 plots. 85db and 93db respectively. One would predict that the distortion levels on the 93db plot would be 8db higher. But as things really are, some of the graph does jump about 8db, but other places, like 550hz, doesnt go up at all. This is curious.

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Old 08-10-2015, 07:24 AM
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Quote:
Originally Posted by AustinJerry View Post
@markus767 and @jim19611961 :

I have given this more thought, and I am now convinced that you both are misinterpreting the distortion graph. The upper curve, which shows the actual frequency response, is measured in dB. The lower distortion curves are not dB levels, they are percentage levels. In my example, the THD associated with the 95dB measurement is 1.07%, but it is not 54.3dB in loudness. This would be clearer if the graph had a vertical scale on the right side that showed percentages, not dB levels. IOW, for Markus to conclude that distortion levels are louder with the 80dB measurement than with the 95dB measurement is incorrect.
no, you're misinterpreting what it says. The graph shows that the level of the 3rd harmonic really is at 54dB, if you somehow could play only the harmonic then that's how loud it would register.

The percentage is then calculated as 10^(-(93-54.3)/20)*100 (which comes out at about 1.16% so presumably the actual levels are not quite 54.3dB and 93dB but lets not split hairs)

I would have thought the reason is minor variations in noise around the house/environment as in room measurement THD data is v sensitive to random fluctuation. If you run each one 10-20 times and it persists then you have something to investigate (if you really really really cared). Perhaps your amp doesn't perform so brilliantly in the 1st watt for example (random guess there).
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Old 08-10-2015, 07:25 AM
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Quote:
Originally Posted by AustinJerry View Post
@markus767 and @jim19611961 :

I have given this more thought, and I am now convinced that you both are misinterpreting the distortion graph. The upper curve, which shows the actual frequency response, is measured in dB. The lower distortion curves are not dB levels, they are percentage levels. In my example, the THD associated with the 95dB measurement is 1.07%, but it is not 54.3dB in loudness. This would be clearer if the graph had a vertical scale on the right side that showed percentages, not dB levels. IOW, for Markus to conclude that distortion levels are louder with the 80dB measurement than with the 95dB measurement is incorrect.
Your right that are two different things going on:

1) Distortion level
2) Distortion percentage

Your right that the levels are generally higher in the 95db plot. But the distortion percentages are lower. This can be true because the distortion percentage is taking into account the rise in SPL and the distortion level does not.

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Old 08-10-2015, 07:33 AM
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Quote:
Originally Posted by AustinJerry View Post
So we have a curiosity. Does anyone think this has any significance, or can we move on?
The curiosity part is insignificant, probably, yes. I think it is significant to know how to interpret the data properly.

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Old 08-10-2015, 08:01 AM
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Originally Posted by J_P_A View Post
I don't have the .mdat for the Fusion sweeps - noob mistake to not save them. Here is the link to the file on google drive - I hope.

Thanks for the help!!!
I'll have a look later tonight (and comment if no one else has).
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Old 08-10-2015, 08:03 AM
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Originally Posted by jim19611961 View Post
The curiosity part is insignificant, probably, yes. I think it is significant to know how to interpret the data properly.
what he said

I'd probably do a quick run with dirac turned off to check what happens to that 75Hz spike but would ignore a variation between 0.7% and 1% as noise.
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Old 08-10-2015, 08:05 AM
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Originally Posted by CherylJosie View Post
Then I immediately noticed that the center speaker is 3dB louder in the subwoofer output and speaker levels than the all surround channels including synthesized high/wide.

The front l/r are 3dB higher in the subwoofer output and speaker level than the center but that makes sense because there are two channels running simultaneously as opposed to one when I do the cal. The center should be 3dB lower than the rest of the system, not 3dB higher than the surrounds. This makes no sense from a calibration standpoint to put 6dB of attenuation into the surrounds.

Anyone run into this before?
This morning I think I figured out the issue.

For convenience I have been calibrating channels/room in pairs of channels since the EQ and crossovers function in pairs for the most part. The only way to energize some of the channels/speakers connected to my TX-NR929 without adding synthesized information to the mix is to use the Full Mono or All Channel Stereo setting, set non-tested speakers to full range or none (depending on interactions between crossover settings in the receiver) to eliminate bass managed crossovers from the subwoofer that are not being investigated, and disconnect all speakers that are not being measured at the time.

For convenience I have also been using the Stereo and Mono settings to calibrate the front LCR and subwoofer without having to unplug so many wires, as well as the Direct setting for REW calibration.

Examples: I used Mono with center disconnected and crossover at 150Hz to calibrate the subwoofer for its maximum expected frequency of operation. Then I reconnected the center to set its crossover and EQ. Then I used Stereo to set the front crossover and EQ, noting that as expected all the levels were up 3dB from Mono. Then when I switched to Full Mono to cal the rest of the channels (including the High and Wide that have no distinct stream content of their own in any case), I noticed the level mismatch.

I suppose the issue is that with Full Mono setting, the receiver is acoustically summing all channels with the exact same signal and that could result in significantly elevated SPL in that mode. Presumably Onkyo added 6dB of attenuation to that sound mode to avoid large jump in SPL.

My guess is that the degree of attenuation may also depend on how many of the 11 possible channels have been configured, but I have not tested that speculation.

This attenuation is not the sort of thing a novice would necessarily expect. I have worked as an engineer for decades and it caught me off guard simply because there is no detailed documentation on the actual function of each sound mode and I never gave such considerations any thought until now, being a relative novice at home theater calibration.

Does AVS Forum have a master thread on setting sound modes and other features such as Phase Matching Bass for manual calibration? A sticky or two explaining the intricacies of some of these functions would be helpful. I just got started and already Phase Matching Bass and Full Mono have caught me by surprise, as did the receiver losing its cal settings and getting confused in the sound modes when it loses power with the setup menu active and some channels shut off.
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Old 08-10-2015, 09:00 AM
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I have a simple but important question about checking speaker and sw trim levels to verify YPAO results. When I check the front left speaker in preferences and set the generator to pink noise and speaker cal, I get the desired 75 dB at -25.0 MV and with a -12.0 dBFS signal. When I select the LFE channel in preferences and set the generator to pink noise and subwoofer cal, I get 90+ dB (I'm running the sub trim 4 dB hot). Am I measuring the sub correctly?

EDIT: I mean I'm trying to check the (average) output levels for frequency response measurements, not trying to calibrate AVR speaker/sub trims to reference level. I want to be sure the test tones are loud enough for accurate measurements but not loud enough to annoy neighbors or damage my hearing.

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Old 08-10-2015, 01:04 PM
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Originally Posted by jim19611961 View Post
The curiosity part is insignificant, probably, yes.
In my book 10dB difference is significant.

Quote:
Originally Posted by jim19611961 View Post
I think it is significant to know how to interpret the data properly.
That's why I brought it up

Markus

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Old 08-10-2015, 01:22 PM
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In my book 10dB difference is significant.
Theories to cause and relevance?

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Old 08-10-2015, 01:37 PM
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Originally Posted by J_P_A View Post
I need some help with my first "real" measurements. I'm not sure what is causing the nulls at 3 kHz, 10 kHz, and 20 kHz. I'm sure i'm doing something (lots) wrong because this shows up in three different speakers in three different locations.
Here's the IR zoomed right in



I've never measured a coaxial driver but it does seem awfully noisy v early on. One possibility is that you have something v near the microphone element that is producing a v strong, v early reflection. A 1/4 wavelength cancellation at those frequencies would mean an object in the vicinity of 25-30mm for the 3kHz null, ~7-8mm for the 10kHz and ~3-4mm for the 20kHz. The most obvious cause of such a reflection is the mic stand itself. Can you share a pic of how you're actually setup to measure?

Do you get similar issues from an listening position measurement? What about in a different room? Can you try a different computer? (just thinking of the other variables in play)

I suggest taking this to the volt thread or a diysg thread btw, this thread is more focused on in room measurements as opposed to gated speaker measurements.
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Old 08-10-2015, 02:26 PM
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Originally Posted by jim19611961 View Post
Theories to cause
Poor signal to noise ratio.

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Originally Posted by jim19611961 View Post
and relevance?
Measurement data doesn't show what it's supposed to show.

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Old 08-10-2015, 02:30 PM
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Originally Posted by CherylJosie View Post
Based upon the verbage in the user guide (I quoted it). It states that changing some of the windowing etc. applies to new measurements. Maybe it is worded poorly but I got clear impression that the old audio was not available for some new settings.
right I'm with you now. Those options have no effect, that I'm aware of, on your ability to manipulate the measurements. It translates as "REW keeps sufficient data to be able to make full use of the measurement". The only limitation I'm aware of is if you subsequently wanted to export the response with linear spaced data points for consumption by some other program.

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By 'impulse' are you referring to the classic impulse (dirac function) or the sinusoidal sweep? Maybe I am just unfamiliar with the lingo here.
I am not referring to a dirac function, I am referring to the recorded impulse response of the system.

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Not following you here. What happens to it after it is copied? Can REW store both the microphone response and a direct electrical channel simultaneously?
it is stored a new, completely independent, measurement. For example, if you have accurate phase data and multiple subs then you can monkey with the timing in REW alone (by copying the response and then shifting the IR) & sum them to see what the summed response will look like if you applied such delays. Similarly you can calculate what n subs give you in FR terms with just 1 sub and multiple measurements. I don't think the REW help explains what each trace arithmetic option is for but section 6 of the Holm user guide does -> http://www.holmacoustics.com/downloa...eUserGuide.pdf


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Originally Posted by CherylJosie View Post
Code:
java -version
java version "1.7.0_79"
OpenJDK Runtime Environment (IcedTea 2.5.6) (7u79-2.5.6-0ubuntu1.14.04.1)
OpenJDK 64-Bit Server VM (build 24.79-b02, mixed mode)
I checked and I do actually use openjdk on linux as well. Perhaps you can try the oracle jdk to see if it fixes it, otherwise I suspect it is some fail on the part of your desktop environment/window manager.

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Originally Posted by CherylJosie View Post
Um... both. Pulse is installed by default but some of my applications hijack the sound card via alsa when outputting surround sound. Not sure which one REW is using but it does show up in Pulse 'applications' tab.
you probably need to work out exactly what REW is using to route audio. If it is ALSA then you may find the examples in https://wiki.archlinux.org/index.php...Configurations useful as it gives some info on how to create virtual devices and route/copy between channels. The alsa rc man is useful too http://alsa.opensrc.org/Asoundrc#Sim....asoundrc_file . I haven't mangled alsa recently enough to be able to comment in detail on exactly what you need to do. I did come across https://github.com/bmc0/dsp while googling those links though which looks pretty useful.
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Old 08-10-2015, 02:47 PM
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Originally Posted by 3ll3d00d View Post
......

I've never measured a coaxial driver but it does seem awfully noisy v early on. One possibility is that you have something v near the microphone element that is producing a v strong, v early reflection. A 1/4 wavelength cancellation at those frequencies would mean an object in the vicinity of 25-30mm for the 3kHz null, ~7-8mm for the 10kHz and ~3-4mm for the 20kHz. The most obvious cause of such a reflection is the mic stand itself. Can you share a pic of how you're actually setup to measure?

Do you get similar issues from an listening position measurement? What about in a different room? Can you try a different computer? (just thinking of the other variables in play)

I suggest taking this to the volt thread or a diysg thread btw, this thread is more focused on in room measurements as opposed to gated speaker measurements.
Thanks for taking the time to look at this!

Unfortunately I don't have a picture of my setup, but I will be sure to take one the next chance I get to do some measurements.

I see the same dips both near the speaker as well as at the LP. I've also measured two different types of speakers. The coaxial (Volt) as well as 2-way with a waveguide (Fusion), and both have the same dips. It has to be something to do with my setup. Is there a way that I should be positioning my mic and mic stand to prevent reflections from being picked up in the measurements?

Keep in mind I'm new to this, so even simple things that I "should" know, I probably don't
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Old 08-10-2015, 02:49 PM
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Originally Posted by AustinJerry View Post
I think I understand what you are trying to show. Place the vertical cursor on two different spots of the distortion curve that are the same height--why isn't the distortion percentage the same for both? The answer, as I see it, is that if you follow the cursor up to the frequency response curve, the cursor intersects the curve at different heights, which would result in different distortion values.

So, I'm not sure I agree that the graph is flawed. Why don't you ask your question over on the Home Theater Shack forum to see if JohnM will comment?
I posted at HTS and John responded. It looks like something is in the works to address my suggestion for later this year.
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Old 08-10-2015, 02:58 PM
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Quote:
Originally Posted by J_P_A View Post
Thanks for taking the time to look at this!

Unfortunately I don't have a picture of my setup, but I will be sure to take one the next chance I get to do some measurements.

I see the same dips both near the speaker as well as at the LP. I've also measured two different types of speakers. The coaxial (Volt) as well as 2-way with a waveguide (Fusion), and both have the same dips. It has to be something to do with my setup. Is there a way that I should be positioning my mic and mic stand to prevent reflections from being picked up in the measurements?

Keep in mind I'm new to this, so even simple things that I "should" know, I probably don't
there are some tips in http://www.troelsgravesen.dk/measurements.htm

here's a random pic of my speaker in the garden, not perfect but good enough for the job

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one other possibility is there is some reflection within the driver, not sure how likely that is (hence why I suggest asking on the volt thread) though seems v unlikely if it affects the fusion too. If the problem is in every measurement then it must either be the mic itself, the way the mic is mounted or some unspecified software fail.
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Old 08-10-2015, 03:00 PM
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Originally Posted by markus767 View Post
Poor signal to noise ratio.



Measurement data doesn't show what it's supposed to show.
A high noise floor could do it. At 80SPLdb, I thought the REW tracking filter would render normal ambient room noise irrelevant.

Air conditioning or the refrigerator being on might generate some anomalies. But in my experience, most of these are below 200hz. Not across the frequency spectrum.

Maybe some sort of noise within the PC itself seeping into the USB channels?

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Old 08-10-2015, 03:29 PM
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How do most here determine the optimal crossover between speakers and subwoofer? I find YPAO recommends anything from 80Hz to 120Hz and FR measures of CC+Sub and FL+FR+Sub look something like this:
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Old 08-10-2015, 03:37 PM
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When I select the LFE channel in preferences and set the generator to pink noise and subwoofer cal, I get 90+ dB (I'm running the sub trim 4 dB hot). Am I measuring the sub correctly?
Yes. Your AVR automatically boosts the LFE channel by 10db by design. If you want the LFE channel to "track" the other channels for a better visual appearance in REW then just remember to set the output level in REW to -22db or 10db lower than whatever level you use for the other 7 channels.
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Old 08-10-2015, 03:39 PM
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Originally Posted by dryeye View Post
Yes. Your AVR automatically boosts the LFE channel by 10db by design. If you want the LFE channel to "track" the other channels for a better visual appearance in REW then just remember to set the output level in REW to -22db or 10db lower than whatever level you use for the other 7 channels.
ok, thanks

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Old 08-10-2015, 03:49 PM
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Originally Posted by PlasmaPZ80U View Post
How do most here determine the optimal crossover between speakers and subwoofer? I find YPAO recommends anything from 80Hz to 120Hz and FR measures of CC+Sub and FL+FR+Sub look something like this:
Set the CC, FR & FL to LARGE.

Measure each speaker individually 15-300hz (could start the sweep at a higher frequency if you know your speakers limitations, i.e. 50-300hz).

Set LPF for LFE as high as it will go and take off any extra bass boost you added in the sub trim (you want all channels reading at the same level).

Measure the sub 15-300hz. If you use HDMI CH4 in REW, turn the sweep level (or MV) down by 10db.

Overlay each of the individual speaker measurements with the sub measurement and they will tell you where you should set your crossover for your speakers in your room.
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Old 08-10-2015, 04:05 PM
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Originally Posted by Alan P View Post
Quote:
Originally Posted by PlasmaPZ80U View Post
How do most here determine the optimal crossover between speakers and subwoofer? I find YPAO recommends anything from 80Hz to 120Hz and FR measures of CC+Sub and FL+FR+Sub look something like this:
Set the CC, FR & FL to LARGE.

Measure each speaker individually 15-300hz (could start the sweep at a higher frequency if you know your speakers limitations, i.e. 50-300hz).

Set LPF for LFE as high as it will go and take off any extra bass boost you added in the sub trim (you want all channels reading at the same level).

Measure the sub 15-300hz. If you use HDMI CH4 in REW, turn the sweep level (or MV) down by 10db.

Overlay each of the individual speaker measurements with the sub measurement and they will tell you where you should set your crossover for your speakers in your room.
Does this method ignore the sw distance (not affected by it)?
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Old 08-10-2015, 10:50 PM
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Quote:
Originally Posted by jim19611961 View Post
A high noise floor could do it.
The graphs have been removed, but IIRC, the distortion volume did not change in the first measurements. In other words, at lower volume levels the distortion is determined by the noise floor of the system (as Markus describes (SNR)).

As volume increases, noise floor remains the same.
As volume increases further, distortion volume increases. Presumably from the speakers or whatever.

IIRC Jim, you posted some distortion graphs many months ago that showed the same phenomenon (and we discussed it back then also).

At lower volume levels, distortion volume is limited by the noise floor of the system (SNR). As (signal) volume increases, the noise floor (distortion volume) remains the same, but the (signal) volume level increases, resulting in a lower distortion percentage.
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Old 08-11-2015, 06:01 AM
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Originally Posted by Alan P View Post
Set the CC, FR & FL to LARGE.

Measure each speaker individually 15-300hz (could start the sweep at a higher frequency if you know your speakers limitations, i.e. 50-300hz).

Set LPF for LFE as high as it will go and take off any extra bass boost you added in the sub trim (you want all channels reading at the same level).

Measure the sub 15-300hz. If you use HDMI CH4 in REW, turn the sweep level (or MV) down by 10db.

Overlay each of the individual speaker measurements with the sub measurement and they will tell you where you should set your crossover for your speakers in your room.
Based on these results, what crossover is recommended?
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UN46EH6030 Calibration/Settings
Samsung UN46EH6030; Yamaha HTR-3066, SVS Prime Bookshelf Mains and Prime Center, Rythmik LV12R; PS4, Xbox One, Motorola RNG150N
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Old 08-11-2015, 06:44 AM
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This is the best I could do with 80Hz...
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UN46EH6030 Calibration/Settings
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Old 08-11-2015, 07:00 AM
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Originally Posted by PlasmaPZ80U View Post
This is the best I could do with 80Hz...
Ok folks - don't try's this!
http://www.cnet.com/news/attention-h...annel-speaker/
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Old 08-11-2015, 07:26 AM
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Yup, centers always sound "boxy."
Don't you just love generalizations.
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Did you really need to quote that entire post in your reply?
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Old 08-11-2015, 09:56 AM
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Originally Posted by PlasmaPZ80U View Post
Does this method ignore the sw distance (not affected by it)?
The distance (delay) has no effect. You are measuring individual speakers. Time alignment only comes into play when there is more than one sound source playing.
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Old 08-11-2015, 10:12 AM
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Guyz please help with my waterfall graph...
this of my front 2 speakers taken together...

what does it tell about mlp ?
i am from India and have very low knowledge of acoustics

any comments appreciated
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Old 08-11-2015, 10:17 AM
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^^^

It tells me you need to read the REW guide linked in my sig...especially the part on how to post graphs.

Seriously though, that's some excessive ringing you got going on there. What kind of room is your system in (size, materials, treatments if any)? Some pics of the room might help.
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