Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 643 - AVS Forum | Home Theater Discussions And Reviews
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post #19261 of 19277 Old Today, 09:59 AM
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Originally Posted by indus1 View Post
I also experimented with different cross overs on hdmi3 from 80-110hz and that doesn't seem to make any difference either.
That is exceedingly strange. Did you back out of the menu to make sure the crossover change "took"?
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post #19262 of 19277 Old Today, 10:04 AM
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Originally Posted by indus1 View Post
I'm not having much luck. I checked under the 'analysis' tab of preferences and it was already set to no timing reference. So I'm assuming I've never been using a timing reference.

I took a fresh set of measurements including for left and right speaker just in case that sheds any light on the matter.

I'm not sure where to go from here.


https://www.dropbox.com/s/2wuyga4zcl...mdat.mdat?dl=0
Indeed, you were not using a timing reference. However, if you have Timing Reference disabled and you select a channel for Timing Reference Output, you are outputting to both of those channels at the same time. So, you haven't been measuring what you thought you were.
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post #19263 of 19277 Old Today, 10:08 AM
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Quote:
Originally Posted by Alan P View Post
That is exceedingly strange. Did you back out of the menu to make sure the crossover change "took"?
It isn't strange, or at least it is not necessarily strange.

He is boosting both channels beyond so as to remove the acoustic rolloff hence the crossover can function as a crossover (without interference from the acoustic rolloff of either speaker).

However typical prepro crossovers are asymmetric hence this strategy is liable to result in a non flat output which then needs further correction to flatten.

Breaking down the signal chain to the constituent parts would allow this to be measured and understood in depth if required.
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post #19264 of 19277 Old Today, 10:24 AM
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Quote:
Originally Posted by Alan P View Post
That is exceedingly strange. Did you back out of the menu to make sure the crossover change "took"?
I backed out one step but not all the way out. I'll back all the way out next time.
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post #19265 of 19277 Old Today, 10:25 AM
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Originally Posted by 3ll3d00d View Post
It isn't strange, or at least it is not necessarily strange.

He is boosting both channels beyond so as to remove the acoustic rolloff hence the crossover can function as a crossover (without interference from the acoustic rolloff of either speaker).
I didn't understand this sentence. Can you rephrase, please?
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post #19266 of 19277 Old Today, 10:28 AM
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Quote:
Originally Posted by Alan P View Post
Indeed, you were not using a timing reference. However, if you have Timing Reference disabled and you select a channel for Timing Reference Output, you are outputting to both of those channels at the same time. So, you haven't been measuring what you thought you were.

I'm a bit confused. I've selected 'no timing reference' under 'analysis' but under 'soundcard preferences' you have to have something in the box marked timing reference.
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post #19267 of 19277 Old Today, 10:33 AM
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Quote:
Originally Posted by 3ll3d00d View Post
It isn't strange, or at least it is not necessarily strange.

He is boosting both channels beyond so as to remove the acoustic rolloff hence the crossover can function as a crossover (without interference from the acoustic rolloff of either speaker).

However typical prepro crossovers are asymmetric hence this strategy is liable to result in a non flat output which then needs further correction to flatten.

Breaking down the signal chain to the constituent parts would allow this to be measured and understood in depth if required.

Matt, have you had a chance to look at my latest data? I've added left and right channels if that helps, I thought in case there is an actual fault with the centre speaker?

Timing reference was already switched off under the 'analysis' tab.

Any idea where I go from here to figure out my strange data?

Thanks
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post #19268 of 19277 Old Today, 11:39 AM
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Originally Posted by artur9 View Post
I didn't understand this sentence. Can you rephrase, please?
a typical (THX style) AVR crossover uses a 4th order low pass filter and a 2nd order high pass filter. The 2nd order HPF is meant to sum with the natural acoustic high pass filter of the main (satellite) speaker so that the total high pass filter is also a 4th order filter. If this actually happened in practice then the result is a flat response irrespective of whether the filters are at 80Hz, 120Hz or whatever.

If you look at indus's Dirac graphs then you'll see he is boosting his main speaker aggressively all the way down to ~30-40Hz, i.e. a full octave beyond the 80Hz crossover and more than an octave beyond what looks like the natural rolloff around 100-120Hz. Similarly the subwoofer is being boosted to flat to around 200Hz.

If those speakers are actually flat well beyond the crossover point then that crossover has a chance of working as intended to produce a flat output.

However real life gets in the way in that a) the typical AVR crossover is assymetric so further correction would be required to flatten out the result, b) the room makes a mess of it in this frequency range. The best solution is therefore to have your crossover algorithm also implement your crossovers so it can ensure a nice sum. No mainstream consumer equipment does this though so various other solutions exist that let people get close enough. A minidsp/dirac owner is probably well advised to use the BM plugin for this purpose.

Is this clear(er)?
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post #19269 of 19277 Old Today, 12:00 PM
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^^^

Most of what you say goes way over my head d00d , but if I understand this correctly, indus's FR graph won't necessarily change when adjusting crossovers (although mine does, each and every time).

Also, are you saying that indus is boosting his mains incorrectly? How would he correct that?
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post #19270 of 19277 Old Today, 12:40 PM
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Quote:
Originally Posted by Alan P View Post
^^^

Most of what you say goes way over my head d00d , but if I understand this correctly, indus's FR graph won't necessarily change when adjusting crossovers (although mine does, each and every time).

Also, are you saying that indus is boosting his mains incorrectly? How would he correct that?
I'm saying

1) his setup is attempting to minimise the extent to which changing the crossover in the receiver by a few Hz will make a difference
2) the result of this configuration is a fairly substantial midbass boost which might well be, or it might not be, what he's trying to fix (as an aside I think an 80Hz crossover is really pushing it for his speakers too)

so yes I am saying that boost is most probably incorrect if the goal is a more consistent response and the bass management employs asymmetric filters

He may be able to use the high pass filter to sum with his bass management filter to achieve a better result (or this might be terrible!) or the BM plugin is another option. Of course there might be other options too.
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post #19271 of 19277 Old Today, 03:12 PM
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Quote:
Originally Posted by indus1 View Post
I'm a bit confused. I've selected 'no timing reference' under 'analysis' but under 'soundcard preferences' you have to have something in the box marked timing reference.
you don't have to select something, you can leave it as is

the new data looks even worse, you have masses of data before the largest peak now. I really have no idea what this could be. Can you post a pic of your Asio4all config? perhaps that will shed some light. Take another measurement with the 2nd channel deselected too. Failing that it's over to HTS to see if JohnM can advise.

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post #19272 of 19277 Old Today, 03:24 PM
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^^^

Could it be a bad mic d00d??
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post #19273 of 19277 Old Today, 04:09 PM
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Originally Posted by 3ll3d00d View Post
...
That was great, thanks! I had bad luck with my minidsp so I just ordered a Xilica off eBay. Please let me know if you have any suggestions for how best to use such a device. My plan is to use it as a 1x4 splitter, time align my subs, and some PEQ to get rid of a room mode @ 31 Hz.
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post #19274 of 19277 Old Today, 06:43 PM
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Quote:
Originally Posted by 3ll3d00d View Post
you don't have to select something, you can leave it as is

the new data looks even worse, you have masses of data before the largest peak now. I really have no idea what this could be. Can you post a pic of your Asio4all config? perhaps that will shed some light. Take another measurement with the 2nd channel deselected too. Failing that it's over to HTS to see if JohnM can advise.


I had an issue with extremely noisy impulse response when I was using one USB interface with mic to measure with REW and another USB soundcard to output sweep to a speaker.
Using same USB interface for input and output doesn't have that issue.

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post #19275 of 19277 Old Today, 08:24 PM
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After some minor fixes to securing the amp onto my LV12R I decided to rerun some of my sweeps tonight moving the mic slightly as I went. Results are below. File can be downloaded here.



MLP vs Best alternative (happens to be SLP) Unsmoothed



Going to run same tests LFE only now at -22db. Anyone think I can do anything to improve this, other than Moving the sub for now and other than miniDSP for now?
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==============================
FS: Proficient GL6 Center Channel Speaker
==============================

My Current "Living Room" Home Theater!
==============================

Last edited by citsur86; Today at 08:27 PM.
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post #19276 of 19277 Old Today, 08:40 PM
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Just ran LFE only - looks like I have a considerable dip at MLP right before Xover pt (at 80hz). I tried the distance tweek and even at a foot further, there is no difference at all in the graph.



File can be downloaded here.
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==============================
FS: Proficient GL6 Center Channel Speaker
==============================

My Current "Living Room" Home Theater!
==============================
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post #19277 of 19277 Old Today, 08:55 PM
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Quote:
Originally Posted by citsur86 View Post
After some minor fixes to securing the amp onto my LV12R I decided to rerun some of my sweeps tonight moving the mic slightly as I went. Results are below. File can be downloaded here.

Going to run same tests LFE only now at -22db. Anyone think I can do anything to improve this, other than Moving the sub for now and other than miniDSP for now?
This shows that the MLP is not ideal for bass response. 1ft right is obviously the worst position, with a 50dB dip at 55Hz! 2ft left seems to be the best response.

The most improvement will come from what many would recommend--additional subs. You can certainly try EQ, but I suspect the improvement will be only at one listening spot.

BTW, when showing bass response below 300Hz, the graphs are normally shown with no smoothing.

Here is an example of what multiple subs can do:

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