Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 360 - AVS Forum
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post #10771 of 10793 Old Yesterday, 11:46 AM
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Originally Posted by AustinJerry View Post
It is not obvious from the room mode calculator that the 45Hz dip is associated with any of the room dimensions.
That's strange Jerry because the REW room sim clearly shows the 45hz dip...unless the sub is located in the back 1/4 of the room.
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post #10772 of 10793 Old Yesterday, 12:32 PM
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I am not familiar with how the room simulator works. However, the formulas in the room mode calculator are simple mathematics, and are accurate.
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post #10773 of 10793 Old Yesterday, 12:36 PM
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Originally Posted by jim19611961 View Post
That is easier said than done. Unfortunately, they dont explain how to graph the results in a comparative and helpful way. Instead, they want you to pay $75 for their analysis
Did you listen to the test signal over headphones? How does it compare to how it sounds when played back on your speakers?

Markus

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post #10774 of 10793 Old Yesterday, 02:33 PM
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Quote:
Originally Posted by AustinJerry View Post
I am not familiar with how the room simulator works. However, the formulas in the room mode calculator are simple mathematics, and are accurate.
the room mode calculator just tells you where the modes are, the rew room sim solves for modes and the listening position (and delays etc dialled into each source).

As far as I can see, placing the MLP and the sub at the same distances from each wall (at 1/3 the length) produces that dip at 45Hz. I'm not entirely sure why.

room_sim.JPG

It doesn't look a great room for 1 sub tbh, how big is the listening area? do you have multiple rows of seats? for a single seating position, sitting at 1/5 the distance from the rear wall and a sub in the corner looks about as good as you can expect.

room_sim_2.JPG
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post #10775 of 10793 Old Yesterday, 02:57 PM
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OK, let's see if he tries that, and what the measurements show. It will be interesting to see how accurate the room simulator is. It should work reasonably well in a rectangular sealed listening room. I have an open floor plan, and such simulators are of no use whatsoever, unfortunately.
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post #10776 of 10793 Old Yesterday, 11:03 PM
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Originally Posted by HDgaming42 View Post
I was shocked running REW with my new sub (empty room) to find a nasty nasty null. I've moved both my MLP and sub around to a number of positions and could use some guidance. My room's dimensions aren't THAT far off a recommended ratio--or so I thought.
Well... room dimensions ratio... My understanding...

A room (enclosed space) is going to have nodes - frequencies that produce standing waves due to reflections. A Cube is usually quoted as the worst, same nodes in all directions, so they reinforce each other. I suppose a sphere would be the ultimate bad room.


The recommended room dimension ratios don't eliminate nodes, but, the nodes for end to end, side to side, floor to ceiling, and the angular reflections, occur at a range of frequencies, not falling on top of each other, not reinforcing each other.

I suppose if the room is bumpy enough it looks smoother, as opposed to one with a few totally black holes in the response.

Close your eyes and see if what you HEAR is as bad as what you think you see when you MEASURE, and go from there.

Musical intruments are not one frequency, they have harmonics and overtones. The ear/brain is adept at filling in the gaps.

I have a big hole at 55hz, and never guessed until I measured it. Didn't notice anything wrong. Now chasing it. That's the hobby.

If you want no nodes, you need an anechoic chamber.

I see the science boys have created the blackest material yet, almost no reflectivity/emission for light. Maybe somebody is working on the same for sound.

https://en.wikipedia.org/wiki/Room_modes

I'll be back later...

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post #10777 of 10793 Old Today, 12:35 AM
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Originally Posted by RayDunzl View Post
I see the science boys have created the blackest material yet, almost no reflectivity/emission for light. Maybe somebody is working on the same for sound.
Already exists, it's called DBA:
Double Bass Array (DBA) - The modern bass concept!

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post #10778 of 10793 Old Today, 08:14 AM
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Originally Posted by RayDunzl View Post
Close your eyes and see if what you HEAR is as bad as what you think you see when you MEASURE, and go from there.

Musical intruments are not one frequency, they have harmonics and overtones. The ear/brain is adept at filling in the gaps.
Sadly this is one of the things that drew me to measuring my room. One of my favourite songs features successive piano chords descending the scale (Spoon--Beast and Dragon Adored). Playing it in that room made me want to weep. Some chords simply disappear. Others play too loudly. To hear them butchered like that in direct succession was like a knife to the heart after a $1000 subwoofer purchase!

If I have to fill 90% of this room with Rockwool, or teach myself how to build Helmholtz resonators / Metal Panel Absorbers I'll do it. This was to be my room of solace, and sadly listening to my Grados sounds better...

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Originally Posted by markus767 View Post
This is truely fascinating stuff. I can't believe there isn't more talk about this than there is! Here's some amazing results using a SBA: http://www.gearslutz.com/board/bass-...ts-inside.html
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post #10779 of 10793 Old Today, 08:33 AM
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Originally Posted by HDgaming42 View Post

This is truely fascinating stuff. I can't believe there isn't more talk about this than there is! Here's some amazing results using a SBA: http://www.gearslutz.com/board/bass-...ts-inside.html
There is not more talk about partly cause few have seen the thread or know of the concept. But secondly, perhaps more importantly, results just as great can be achieved through other, more conventional means. Extensive bass trapping.

rew r today.jpg

(1/24th oct smoothing)

This is mine. But at least half a dozen other posters here have gotten similar results, also through conventional means.

Mostly, folks with uneven bass don't provide enough bass trapping in their room. As ive seen posted several times, I have never seen a room with too much bass trapping.

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post #10780 of 10793 Old Today, 08:37 AM
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Originally Posted by jim19611961 View Post
results just as great can be achieved through other, more conventional means.
I beg to differ. DBA approaches free-field conditions. Passive absorption becomes unpractical when trying to achieve same results.

Markus

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post #10781 of 10793 Old Today, 08:54 AM
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Originally Posted by markus767 View Post
i beg to differ. Dba approaches free-field conditions. Passive absorption becomes unpractical when trying to achieve same results.
dba vs mine.JPG

The Cyan is mine, the Red is the waterfall from the dba page. I used similar scale and smoothing. I wouldnt say the dba blows me out of the water.

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post #10782 of 10793 Old Today, 08:59 AM
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^
Now compare your room to a DBA setup. That's why I've said "unpractical" Especially when one has concrete walls all around. Very common in Europe. Not such much in the US.

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post #10783 of 10793 Old Today, 09:08 AM
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^
Now compare your room to a DBA setup. That's why I've said "unpractical" Especially when one has concrete walls all around. Very common in Europe. Not such much in the US.
Are you insinuating my room is unpractical?

True, I wouldn't get the result I am getting in a concrete room.

Even in a concrete room, the room within a room concept would work pretty well I think.

RFZ 01.jpg

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post #10784 of 10793 Old Today, 09:54 AM
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Originally Posted by HDgaming42 View Post

If I have to fill 90% of this room with Rockwool, or teach myself how to build Helmholtz resonators / Metal Panel Absorbers I'll do it. This was to be my room of solace, and sadly listening to my Grados sounds better...
I still think the most impact will be from a second sub. Then additional bass traps. JMO.
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post #10785 of 10793 Old Today, 10:08 AM
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I still think the most impact will be from a second sub. Then additional bass traps. JMO.
Agreed.

But lets consider something else. If your mains are full range speakers, and you don't cross them over, and let their bass extend, you now have two more subwoofers in a sense (that is, two more sources producing in the low bass region).

For those with only one sub, it might be worth trying.

This is basically how my system operates. (2) main speakers run full range (no XO), plus (3) subs. So essentially, I have (5) sources in the bass region.

My Room 12-07-13 sub locations.jpg

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post #10786 of 10793 Old Today, 10:40 AM
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Quote:
Originally Posted by AustinJerry View Post
I still think the most impact will be from a second sub. Then additional bass traps. JMO.
Quote:
Originally Posted by jim19611961 View Post
Agreed.

But lets consider something else. If your mains are full range speakers, and you don't cross them over, and let their bass extend, you now have two more subwoofers in a sense (that is, two more sources producing in the low bass region).
My main front speakers are actually monitors - Mackie HR626mkII. They're what I use 8hrs a day at work, so I'm used to them. They're powered and pretty flat (which is what I wanted). Although your full-range idea would probably work, I don't think that's in my future.

My sub is an SVS PB-2000. The thing is a monster in a room my size (10' x 16'). Finding a home for two of them that doesn't interfere with a) L, C, R b) corner bass trapping or c) rear wall treatment d) my television might be a challenge.

Would I be safe to assume the flattest response would be to place both subs in the middle of the width of the room, front and back? I think that's what I gathered from the HK paper. Four subs is a non-starter.

I have about 3hrs a week to devote to that room, so I am now 1/4 the way toward building bass traps for the front two corners. Doing Roxul safe n sound superchunks with about a 32" face (freestanding units that can stack). Once I get those in I can roll the sub back in and do another sweep before and after to see what that does.

Next up--I'm guessing--will be to treat the back wall. My back corners have a door on one side, and a cubby for an equipment rack on the other, so no easy way to trap those corners unfortunately.

Thanks for the help / advice thus far!
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post #10787 of 10793 Old Today, 10:46 AM
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Have you tried the sub in the rear 1/4 of the room (as REWs room sim showed that to produce the flattest response)??
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post #10788 of 10793 Old Today, 11:25 AM
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Have you tried the sub in the rear 1/4 of the room (as REWs room sim showed that to produce the flattest response)??
Not extensively. I'd read that putting your sub behind you isn't really advisable with mains that cross at 80Hz. I know there are conflicted opinions on that. I'm also not sure how accurately REWs room sim fits my room (with a window and cubby for the rack).

I've attached it's prediction of listening position A, and the actual reading. Would you say that prediction is close (I'm not being snarky--I'm genuinely curious).

I've also attached a placement in the back 1/4 that I interpret as much easier to deal with. Is this what you're referring to? A peak at 70dB and 75dB to iron out instead of many nulls?

I should add my ceiling is 88".
Attached Images
File Type: png back quarter.PNG (95.8 KB, 5 views)
File Type: png room simulator position A.PNG (39.5 KB, 5 views)
File Type: png actual measurement position a.png (58.8 KB, 5 views)
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post #10789 of 10793 Old Today, 11:36 AM
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I would say that it is recognisably the same response, the sim has exaggerated the size/q of the first peak to null but otherwise it looks good.

In my experience, of room sim vs reality in a cuboid room that has some shallow alcoves, the sim accuracy degrades as the mic approves the non linear areas (ie the alcoves). The usefulness therefore varies with the listening position.
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post #10790 of 10793 Old Today, 11:40 AM
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80hz is actually where your crossover should be to eliminate localization....you'll be fine with the sub behind you.

I would say that REWs prediction is pretty spot-on to your in-room measurement. That's why I think it would be spot-on for the predicted response with the sub behind you.

Yes, Audyssey will be able to iron out those peaks much easier than it can try to fill in the huge null(s)....give it a go, you got nothing to lose but time!
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post #10791 of 10793 Old Today, 11:43 AM
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Quote:
Originally Posted by HDgaming42 View Post
Not extensively. I'd read that putting your sub behind you isn't really advisable with mains that cross at 80Hz. I know there are conflicted opinions on that. I'm also not sure how accurately REWs room sim fits my room (with a window and cubby for the rack).

I've attached it's prediction of listening position A, and the actual reading. Would you say that prediction is close (I'm not being snarky--I'm genuinely curious).

I've also attached a placement in the back 1/4 that I interpret as much easier to deal with. Is this what you're referring to? A peak at 70dB and 75dB to iron out instead of many nulls?

I should add my ceiling is 88".
Seems in your room sim capture that your MLP is in the center of the room, I thought it was 5'4" from the back wall...?
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post #10792 of 10793 Old Today, 11:58 AM
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Originally Posted by 3ll3d00d View Post
I would say that it is recognisably the same response, the sim has exaggerated the size/q of the first peak to null but otherwise it looks good.
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I would say that REWs prediction is pretty spot-on to your in-room measurement. That's why I think it would be spot-on for the predicted response with the sub behind you.
Thanks!

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Seems in your room sim capture that your MLP is in the center of the room, I thought it was 5'4" from the back wall...?
It was. The graph didn't look great (what did you come up with?) so I moved the MLP forward until it looked fairly flat (attached with original MLP).

Maybe I don't have the hang of the REW room sim, but applying both the 2 and 4 sub HK models to this simulator doesn't seem to really get me any closer to flat than 1 sub with placement in the back 1/4. What am I missing?
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File Type: png MLP 5foot4.PNG (101.2 KB, 3 views)

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post #10793 of 10793 Old Today, 12:12 PM
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piano keys original DB keys.jpg

In respect to our FR and house curve, I thought id post a variation of something id done before.

Red +4
Orange (Dark) +2
Orange (Light) +0
Yellow -2
Green (light) -4

So about 2db per color change.

Always looking for new ways to look at things.

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Rega - DAC
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Jenzen Next ( http://www.troelsgravesen.dk/Jenzen-NEXT.htm )
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