Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 446 - AVS | Home Theater Discussions And Reviews
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post #13351 of 13374 Old 01-27-2015, 03:02 PM
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Originally Posted by Alan P View Post
Apparently.

When the subs are set to 75db they just don't satisfy like they do at 80-81db. I know I'm not alone.

I see folks on here saying that they are running their subs "3db hot" or "6db hot", I was just wondering how they know how hot they are running. Because by one method I'm ~10db hot, by another I'm onyl ~5db hot that is all.
Wouldn't a measurement show how hot the sub is running?
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post #13352 of 13374 Old 01-27-2015, 03:11 PM
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Jerry,

Well, that goes back to my OP (linked below)....I get seemingly differing results from a sweep than I do with Pink Noise and REWs SPL logger. I guess it really doesn't matter as long as it sounds good to me.

Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs
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post #13353 of 13374 Old 01-27-2015, 03:41 PM
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^^ you have to measure with -3dbsf in rew in order to have the correct absolute db. With this -3dbsf measurement at -30MV, your subs only (at Aud set level) should be along the 85db line, your speaker only should be along the 75db line. I always check these after running Aud and always find subs set -2db lower by Aud. Perhaps, Jerry should add the -3dbsf part to the guide if one wants to know the absolute db numbers. The default by REW is -12dbsf IIRC.

Last edited by tvuong; 01-27-2015 at 03:49 PM.
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post #13354 of 13374 Old 01-27-2015, 04:10 PM
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Ahhh, thanks tvuong. That makes sense.

That sweep above was done at -23dbsf and 0MV. When you say:

Quote:
your subs only (at Aud set level) should be along the 85db line
I'm assuming that be using the LFE output of REW (CH4), correct?

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post #13355 of 13374 Old 01-27-2015, 04:14 PM
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^^ yes sir, correct.
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post #13356 of 13374 Old 01-27-2015, 04:20 PM
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Sweet, gonna do some more sweeps tonight!


How bad is it I get excited when I have a REW project to do??
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post #13357 of 13374 Old 01-27-2015, 04:26 PM
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^^ running compression sweeps with -3dbsf will let you know the true highest db your subs can play before compression. Have fun.
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post #13358 of 13374 Old 01-27-2015, 04:53 PM
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Quote:
Originally Posted by tvuong View Post
^^ you have to measure with -3dbsf in rew in order to have the correct absolute db. With this -3dbsf measurement at -30MV, your subs only (at Aud set level) should be along the 85db line, your speaker only should be along the 75db line. I always check these after running Aud and always find subs set -2db lower by Aud. Perhaps, Jerry should add the -3dbsf part to the guide if one wants to know the absolute db numbers. The default by REW is -12dbsf IIRC.
I disagree. Read the Guide section titled "Using REW to Set and Measure Speaker Levels" starting on p. 95. After reading that section, we can discuss if you disagree with the procedure.
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post #13359 of 13374 Old 01-27-2015, 09:48 PM
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Originally Posted by markus767 View Post
In any room the number of modes increases with frequency:

Markus,

A little confused by your graph. I was referring to the axial room modes determine by Harmon calculator here: http://www.harman.com/EN-US/OurCompa...ID=Calculators

Is our graph counting all the axial, tangential and oblique room modes + their harmonics going up to infinity? Thought above 500Hz, broadband absorbers such OC703 are quite effective.

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post #13360 of 13374 Old 01-27-2015, 10:00 PM
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Originally Posted by steveting99 View Post
A little confused by your graph. I was referring to the axial room modes
The room modes do increase with frequency as per the graph Markus posted. But it is this increase in modes that negates their effect.
A room mode enforces SPL at the frequency of the mode. So if we have modes at every hz between 20-80hz, we don't really have a problem, because every hz has the same level. And this is what happens at higher frequencies, there are so many modes packed so close together.

This is different to an reflection, which at high frequencies (as you note), can be easily fixed. At frequencies below 200hz, not so easily (when one considers WAF etc).
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post #13361 of 13374 Old Yesterday, 02:17 AM
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Quote:
Originally Posted by steveting99 View Post
Is our graph counting all the axial, tangential and oblique room modes + their harmonics going up to infinity? Thought above 500Hz, broadband absorbers such OC703 are quite effective.
The graph shows all modes.
From 80Hz to 500Hz it's a long way

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post #13362 of 13374 Old Yesterday, 05:31 AM
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Originally Posted by markus767 View Post
The graph shows all modes.
From 80Hz to 500Hz it's a long way
All our problems would be solved if we had infinite modes all the way down to 5Hz.
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post #13363 of 13374 Old Yesterday, 05:44 AM
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^
Use headphones

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post #13364 of 13374 Old Yesterday, 06:39 AM
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Originally Posted by markus767 View Post
^
Use headphones
But...but... then how do I use my mad REW skillz?

I don't like headphones in any case. I feel like my head is in a vise. And IEMs and earbuds are really uncomfortable. I only really use them if I'm desperate.
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post #13365 of 13374 Old Yesterday, 06:42 AM
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^
Yes, a couple of fundamental things would have to change (like individual HRTFs, spatial signal processing, etc.) before headphones can declare victory over speaker.

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post #13366 of 13374 Old Yesterday, 09:12 AM
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Originally Posted by artur9 View Post
All our problems would be solved if we had infinite modes all the way down to 5Hz.
So how do I rearrange my furniture to get MORE nodes?

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Did you really need to quote that entire post in your reply?
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post #13367 of 13374 Old Yesterday, 09:38 AM
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So how do I rearrange my furniture to get MORE nodes?
IIRC, the paper that recommends multiple subs said 5,000 would do it. So, replace all your furniture with subs.
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post #13368 of 13374 Old Yesterday, 09:49 AM
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I would if I could.

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Did you really need to quote that entire post in your reply?
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post #13369 of 13374 Unread Yesterday, 07:46 PM
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I would if I could.
I was reading over at Salk how he made a subwoofer coffee table. We need more geniuses like that.
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post #13370 of 13374 Unread Today, 03:05 AM
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Originally Posted by artur9 View Post
I was reading over at Salk how he made a subwoofer coffee table. We need more geniuses like that.
Wouldn't it be better to put the (sub) coffee table near where the Main Listening Position (MLP) is at in order to get more tactile feel?

If Brian can do this, I reckon Rythmik will sell a few more subs just because the better half likes a nice looking coffee table than none. Maybe mention this over in the Rythmik thread?

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post #13371 of 13374 Unread Today, 08:35 AM
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Most people put a coffee table in front of the (main) seating positions. Absolutely terrible place for it, sonically speaking, regardless whether it holds a sub or snacks.

OTOH just about any sub can be used as a side table (except one of mine...). Many have been made specifically to look good/right for that purpose since the "beginning" of home subs (I have one of those too...), and it's much better sonically overall, and usually specifically for the sub's performance too.
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post #13372 of 13374 Unread Today, 09:55 AM
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Originally Posted by artur9 View Post
I was reading over at Salk how he made a subwoofer coffee table. We need more geniuses like that.
My question is, whats happens to the coffee during a loud movie?


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post #13373 of 13374 Unread Today, 11:00 AM
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My question is, whats happens to the coffee during a loud movie?

Well, I think that lends more meaning to the phrase, Shaken not stirred. On the other hand, shouldn't need coffee during such bombastic flicks.

More seriously, GoldenEars and other routinely demo subwoofers with no cabinet vibrations. I'm sure Jim Salk could do it as wll.
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post #13374 of 13374 Unread Today, 12:00 PM
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Originally Posted by cfraser View Post
Most people put a coffee table in front of the (main) seating positions. Absolutely terrible place for it, sonically speaking, regardless whether it holds a sub or snacks.

OTOH just about any sub can be used as a side table (except one of mine...). Many have been made specifically to look good/right for that purpose since the "beginning" of home subs (I have one of those too...), and it's much better sonically overall, and usually specifically for the sub's performance too.

That's exactly what I do: have two HNUS ULS-15s flanking either side of the sofa that serves as MLP. It's not a pure "near field" setup (where I'd put it behind the sofa) but it works, plus they're equidistant. We put a cloth or coasters on top when someone wants to have drinks and isn't sitting in the middle.


The only downside is that our one-year-old is getting frisky, and he might eventually get the idea of trying to use each sub as a jumping board.

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