• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

First REW Measurements-Newbie REW Graph Interpertation- Help me interpret

tjm2

Member
Joined
Aug 14, 2024
Messages
12
Likes
5
Never used REW- but got it setup and took my first few measurements from my listening position. I need help interpreting the results.

I recently added 2 REL t/9x subwoofers to my Stereo setup. I have ELAC Navis ARF-51's. I am trying to integrate the subwoofers. This is an untreated room with carpet floor- 7ft celings and is roughly 16'x22'. The speakers are set along the 16' wall aproximately 2 ft from sidewalls and 1.5ft from front wall. I have the crossover on the subs set to come in around 50-60Hz (i think as REL does not have exact crossover settings).

I took a few measurements with the subs off for a baseline, and then with low, medium, and high gain settings. Can someone pelase advise what they think about the room acoustics? I am thinking the Sub @4 is the best integrated but am not sure if Sub @9 is more true sounding in room.

Let me know your thoughts.

Thanks!!
 

Attachments

  • Overlay Graphs.JPG
    Overlay Graphs.JPG
    124.1 KB · Views: 252
  • No smoothing.JPG
    No smoothing.JPG
    145.1 KB · Views: 245
Post the measurement without subs and then with subs only, that will tell us a lot.
 
Some questions for you.

1. What does "sub @4" and "sub @9" mean?
2. How are you connecting your REL's to your mains? Are you high passing your mains? Or are you doing REL's recommendation of letting the mains run full range?

From what I can see of your posted graphs:

- The yellow curve looks the best, because the bass rolls off the least.
- All 4 measurements have way too much bass. About 10dB too much.
- There is a severe dip at about 130Hz or so. I don't know the cause of that at the moment. I would like to see measurements with/without subs, as raindance suggested. I suspect your subs are kicking in much higher than the "50-60Hz" that you think. In fact it looks as if the subs might go up to 100Hz and the huge dip at 130Hz is phase cancellation at the XO point. I might be wrong.

Oh, and welcome to ASR!
 
he measurement without subs and then with subs only, that will tell us a
Some questions for you.

1. What does "sub @4" and "sub @9" mean?
2. How are you connecting your REL's to your mains? Are you high passing your mains? Or are you doing REL's recommendation of letting the mains run full range?

From what I can see of your posted graphs:

- The yellow curve looks the best, because the bass rolls off the least.
- All 4 measurements have way too much bass. About 10dB too much.
- There is a severe dip at about 130Hz or so. I don't know the cause of that at the moment. I would like to see measurements with/without subs, as raindance suggested. I suspect your subs are kicking in much higher than the "50-60Hz" that you think. In fact it looks as if the subs might go up to 100Hz and the huge dip at 130Hz is phase cancellation at the XO point. I might be wrong.

Oh, and welcome to ASR!
Hi Keith,

Thanks for helping! I obviously need it!

1.- Sub 4 and Sub 9 were the readings at different gain levels. I just realized you can't see what colors are what. I will attach new graphs for you.
2. The RELs and connected via RCA connection from my Preamp. My preamp does not have dedicated Sub out, and I have no way of connection via the high level speakon as reccomended. I tried to dial in the crossover via the instructions that came with the REL's. I have powered speakers. The preamp is a Naim Unity Atom HE. I am not high passing the mains- they do have the ability to be high passed internally at 60Hz or 80Hz.

I will attach new graphs for you. Red is without Subwoofer engaged. Blue is Low gain (4 clicks on the REL), Green si medium gain(8 clicks on the REL), and orange is high gain (12 clicks on the REL).

I am at the office at the momement but when I get a chance I will get a reading with just the subwoofers.

Thanks again!
 

Attachments

  • No Sub.JPG
    No Sub.JPG
    175.9 KB · Views: 104
  • No smoothing.JPG
    No smoothing.JPG
    145.1 KB · Views: 98
  • Medium Gain.JPG
    Medium Gain.JPG
    176.2 KB · Views: 99
  • Low Gain.JPG
    Low Gain.JPG
    178.6 KB · Views: 86
  • High Gain.JPG
    High Gain.JPG
    174.1 KB · Views: 104
I will wait for you to post the other graphs when you finish work. In the meantime, some hints for you to help us read the graphs:

- rename the graphs in REW so that the legends show what you are measuring instead of the date "L-R 14 Aug 2024" is not as helpful as "REL Sub Gain +4", for example.
- if you are comparing two or more graphs, it helps to overlay them. Posting two individual graphs if you want us to compare them makes comparison exceedingly difficult.
- posting .mdat's is even better.

Also, it is important to know if your measurement was taken correctly. It should be taken from the listening position, at ear level, and with a microphone tripod with a boom. Wedging the mic between cushions or perching it on top of books will affect the result.

1723662587550.png


I googled your sub to look at the back panel. It seems as if your REL is rather limited in terms of what you can control.
 
Also- important- post the impulse response so we can see how it's gated (assuming you're doing a chirp rather than pink noise). That's easy to get wrong.
 
Okay let's try this. I took some new measurements when I got home tonight. Ive attached them. I also put on my google drive the .mdat files.

I have the measurement mic in my listening position at ear level on a mic stand. Hopefully this helps.

Google Drive Links with .mdat files:

FS Only = Floor standing Speakers Only
SB Gain +9 only = Subwoofer only with gain set at 9 clicks
FS + SB +9 gain = Floor Standing Speakers and Subs with gain set at 9clicks
FS + SB +6 gain = Floor Standing Speakers and Subs with gain set at 6 clicks
FS + SB +3 gain = Floor Standing Speakers and Subs with gain set at 3 clicks

Thank you for being so welcoming and helpful, while I try and figure out this technology. I appreciate it!
 

Attachments

  • SB Gain +9 only.png
    SB Gain +9 only.png
    607 KB · Views: 100
  • Impulse response.png
    Impulse response.png
    646.1 KB · Views: 104
  • All .png
    All .png
    1.2 MB · Views: 104
  • FS Only.png
    FS Only.png
    807.9 KB · Views: 101
Okay let's try this. I took some new measurements when I got home tonight. Ive attached them. I also put on my google drive the .mdat files.

I have the measurement mic in my listening position at ear level on a mic stand. Hopefully this helps.

Google Drive Links with .mdat files:

FS Only = Floor standing Speakers Only
SB Gain +9 only = Subwoofer only with gain set at 9 clicks
FS + SB +9 gain = Floor Standing Speakers and Subs with gain set at 9clicks
FS + SB +6 gain = Floor Standing Speakers and Subs with gain set at 6 clicks
FS + SB +3 gain = Floor Standing Speakers and Subs with gain set at 3 clicks

Thank you for being so welcoming and helpful, while I try and figure out this technology. I appreciate it!
You can drastically reduce the gating of the impulse; you'll lose a bit of resolution, but get a more accurate idea of what the speaker is doing. That said, at first glance it looks like that severe notch at 120-130Hz is a function of where your speakers and mic are. Changing the gating definitely changes that notch so it's clearly a room mode. Before trying to add subwoofers, try some different speaker positions to smooth that out a bit.

Get the mains right first!
 
The preamp is a Naim Unity Atom HE. I am not high passing the mains- they do have the ability to be high passed internally at 60Hz or 80Hz.
(emphasis added)

I won't say that's your only problem, but I will say it explains a lot about the measurements.

Try setting the high pass on the mains and the Rels to the same frequency. I would try 60 first, but 80 might work better.

Absent that, turn the crossover on the Rels to minimum, turn up the gain and measure at various levels until you find something close, then correct as you can with with other settings/eq. For reference, when I did this with speakers that roll of at a similar level to yours, I ended up at like 2/10 on the gain and the lowest option for crossover (50hz in my case)... with one 100 watt sub. That was close, but there were still issues.

Feathering in a sub without using a crossover can be done, but it is a picky process to get right.
 
Thanks for uploading your .mdat files. I had a look.

1723723896567.png


These are your floorstanding speakers (red) and subwoofer (green) with 1/12 smoothing applied. ASSUMING that both measurements were taken properly and the mic was not moved, we can see:

- the subwoofer is massively down in gain compared to the main speakers. About 25dB down. They are contributing very little to the sound, mostly <40Hz. You did not indicate what gain setting you had on the sub when the green curve was measured, but my prediction is gain +6.
- the mains produce too much bass down to 40Hz, and then it drops off a cliff. About 10dB too much bass.
- the dip at 130Hz is likely due to improper positioning of the mains. It is going to be either SBIR or a room mode.

1723724231258.png


This is a comparison of mains only (red) and mains with sub on +9 gain (yellow). You can see that the two curves hug each other perfectly above 100Hz. Below 100Hz, the start to deviate. the amount of deviation from the red is what your subwoofer is contributing. So you can see ... 1dB here and there, but where it really kicks in is <40Hz where it fills in the missing bass adequately. Not as much as we would like, but at least it is doing something.

Diagnosis: main speakers are producing 10dB too much bass between 40Hz - 100Hz.

Comments:
- It does not look like you can high pass your mains above 100Hz because your subs don't go high enough, nor are they loud enough to take over bass duties if the mains are high passed. So the usual suggestion of "high pass your mains, low pass your subs" does not look feasible IMO. It is still possible, but most of the improvement can be made by EQ. So your best bet is to use EQ to cut down your mains by 10dB <100Hz. Then use your subs with gain +9. Remeasure after you do this.

There is more to see. You have a broad dip centred around 125Hz. This is what "Mains + gain 9" looks like with ERB smoothing:

1723725769919.png


ERB smoothing tries to replicate what you will actually hear. We can see that you have a huge suckout in your midbass between 120Hz to 360Hz ... it is 240Hz wide, and up to 10dB deep, about 5dB deep on average. Midbass is where punch and impact can be found. If you have a curve like that, with too much bass and missing midbass, it will sound a bit bloated and bassy but somehow lacking punch. But it does not tell us what the culprit is.

1723726271379.png


For that, we look at the same curve, but this time with 1/12 Gaussian smoothing. We can see that the culprits are two huge dips, around 125Hz, and another at 270Hz.

If we focus on the dip at 125Hz only, you will see that it is 40Hz wide, and 10dB deep. It's actually comprised of two dips merged into one - 121Hz and 129Hz.

You said your speakers are 2ft from the side wall, and 1.5ft from the front wall - this means the SBIR wavelengths are going to be 8ft and 6ft respectively - 140Hz and 190Hz. If this is due to SBIR, then it is possible that your front wall and side wall distances are closer together than you indicated. One rule is to avoid placing speakers equidistant from the front wall and side wall, because the SBIR cancellation sums and you get a dip which is twice as deep. Get a tape measure out and check the distances again. One of the distances is going to be 2.35ft, and the other is probably 2.2ft (depending on the speed of sound where you live) IF it is SBIR. Read more about SBIR here.

The other possibility is a room mode. The 270Hz dip is in the transition zone, also likely a room mode. The solution would be: move your speakers and listening position around a little bit and see if it improves. You can use REW's room simulator and see what happens.
 
Thanks for uploading your .mdat files. I had a look.

View attachment 386607

These are your floorstanding speakers (red) and subwoofer (green) with 1/12 smoothing applied. ASSUMING that both measurements were taken properly and the mic was not moved, we can see:

- the subwoofer is massively down in gain compared to the main speakers. About 25dB down. They are contributing very little to the sound, mostly <40Hz. You did not indicate what gain setting you had on the sub when the green curve was measured, but my prediction is gain +6.
- the mains produce too much bass down to 40Hz, and then it drops off a cliff. About 10dB too much bass.
- the dip at 130Hz is likely due to improper positioning of the mains. It is going to be either SBIR or a room mode.

View attachment 386609

This is a comparison of mains only (red) and mains with sub on +9 gain (yellow). You can see that the two curves hug each other perfectly above 100Hz. Below 100Hz, the start to deviate. the amount of deviation from the red is what your subwoofer is contributing. So you can see ... 1dB here and there, but where it really kicks in is <40Hz where it fills in the missing bass adequately. Not as much as we would like, but at least it is doing something.

Diagnosis: main speakers are producing 10dB too much bass between 40Hz - 100Hz.

Comments:
- It does not look like you can high pass your mains above 100Hz because your subs don't go high enough, nor are they loud enough to take over bass duties if the mains are high passed. So the usual suggestion of "high pass your mains, low pass your subs" does not look feasible IMO. It is still possible, but most of the improvement can be made by EQ. So your best bet is to use EQ to cut down your mains by 10dB <100Hz. Then use your subs with gain +9. Remeasure after you do this.

There is more to see. You have a broad dip centred around 125Hz. This is what "Mains + gain 9" looks like with ERB smoothing:

View attachment 386616

ERB smoothing tries to replicate what you will actually hear. We can see that you have a huge suckout in your midbass between 120Hz to 360Hz ... it is 240Hz wide, and up to 10dB deep, about 5dB deep on average. Midbass is where punch and impact can be found. If you have a curve like that, with too much bass and missing midbass, it will sound a bit bloated and bassy but somehow lacking punch. But it does not tell us what the culprit is.

View attachment 386620

For that, we look at the same curve, but this time with 1/12 Gaussian smoothing. We can see that the culprits are two huge dips, around 125Hz, and another at 270Hz.

If we focus on the dip at 125Hz only, you will see that it is 40Hz wide, and 10dB deep. It's actually comprised of two dips merged into one - 121Hz and 129Hz.

You said your speakers are 2ft from the side wall, and 1.5ft from the front wall - this means the SBIR wavelengths are going to be 8ft and 6ft respectively - 140Hz and 190Hz. If this is due to SBIR, then it is possible that your front wall and side wall distances are closer together than you indicated. One rule is to avoid placing speakers equidistant from the front wall and side wall, because the SBIR cancellation sums and you get a dip which is twice as deep. Get a tape measure out and check the distances again. One of the distances is going to be 2.35ft, and the other is probably 2.2ft (depending on the speed of sound where you live) IF it is SBIR. Read more about SBIR here.

The other possibility is a room mode. The 270Hz dip is in the transition zone, also likely a room mode. The solution would be: move your speakers and listening position around a little bit and see if it improves. You can use REW's room simulator and see what happens.

Thank you so much for the detailed response, much appreciated.

I will play around with main speaker positioning and see if I can get that dip around 120Hz and 270Hz to lessen. My front wall has the right channel on a wall aproximately 4" behind the left channel, I tired to account for this but maybe in doing so I created an issue. The speakers are about 9' apart tweeter to tweeter and my seating position is equalaterally 9' way. (arpoximately) I have good center imaging and sepearation, so I thought I had it locked in, but obviously not.

I will try to make sure they are not equadistant to the wall boundaries- increasing distance from sidewall and rear wall.

I do have more adjustment range in the subwoofers- I have a ton more gain I can increase as well as the crossover point. Do you think I should incease the crossover point? I was trying to do it as REL suggests in having the subwoofer kick in where my mains start falling off. Also should I Increase the volume more from where its set to have them more present?
 
I will try to make sure they are not equadistant to the wall boundaries- increasing distance from sidewall and rear wall.
Consider the floor and ceiling boundaries as well. Roy Allison wrote extensively about this and his stuff is incredibly useful to know.
 

Attachments

  • RoyAllison.pdf
    3.2 MB · Views: 73
I would first leave the subs allone and start with the mains set to 80Hz. Do another sweep. Your aim with subs is to improve on bass, but also to take some load of your mains, which improves their performance.
Then move them around and try to find a position that smoothes them out, with all their other switches, except the high pass, set to 0dB.
It will take quite some time to find the best position.
Then you can start with integrating the sub.
 
Thank you so much for the detailed response, much appreciated.

I will play around with main speaker positioning and see if I can get that dip around 120Hz and 270Hz to lessen. My front wall has the right channel on a wall aproximately 4" behind the left channel, I tired to account for this but maybe in doing so I created an issue. The speakers are about 9' apart tweeter to tweeter and my seating position is equalaterally 9' way. (arpoximately) I have good center imaging and sepearation, so I thought I had it locked in, but obviously not.

I will try to make sure they are not equadistant to the wall boundaries- increasing distance from sidewall and rear wall.

I do have more adjustment range in the subwoofers- I have a ton more gain I can increase as well as the crossover point. Do you think I should incease the crossover point? I was trying to do it as REL suggests in having the subwoofer kick in where my mains start falling off. Also should I Increase the volume more from where its set to have them more present?

Right now your subwoofers are not the problem. It is your mains that are the problem:

- the huge bass shelf is not due to the sub. It's due to your mains.
- dips in 130Hz and 270Hz are beyond the operating range of your sub, so they are not contributing to the problem.

As SIY said, fix your mains first. Reposition them until the bass is as good as you can get it.

And BTW, "centre imaging and separation" is a high frequency thing, not so much a bass thing. The advantage of owning subs is that you can place your speakers where they are most optimal for imaging, and place your subs where they are most advantageous for bass. Are you willing to add DSP to your system? Then you can really dial it in. If you add DSP, I would suggest low passing the subs at 60Hz, high passing the speakers at 60Hz, then EQ'ing the lower frequencies of the speaker so they blend in with the subs. When you done well, most people can't tell that there is a sub in the system.
 
Question: what are the subs good for as FR of the mains goes down to sub 30 Hz ?
 
Salt : The ELAC Navis ARF-51 are rated 43 Hz–28 kHz. They are to reinforce the mains- go a little lower. These speakers have 5.25" drivers.

@Keith_W : The mains are rear ported- I'm assuming I do have them too close to the front wall- I now see in the graphs how much the bass is boosted in those regions. I'm hoping moving them will help! Thanks for helping me undestand REW!
 
Question: what are the subs good for as FR of the mains goes down to sub 30 Hz ?
At what SPL?

Subs will (if they're decent) go to much higher SPL at lower distortion AND reduce the distortion of the mains by reducing displacement of the mains' woofers.
 
Salt : The ELAC Navis ARF-51 are rated 43 Hz–28 kHz. They are to reinforce the mains- go a little lower. These speakers have 5.25" drivers.

@Keith_W : The mains are rear ported- I'm assuming I do have them too close to the front wall- I now see in the graphs how much the bass is boosted in those regions. I'm hoping moving them will help! Thanks for helping me undestand REW!
You could leave them where they are and see what effect blocking the ports with some foam or a washcloth has.
 
Salt : The ELAC Navis ARF-51 are rated 43 Hz–28 kHz. They are to reinforce the mains- go a little lower. These speakers have 5.25" drivers.
What they are rated is one point. The other is how they behave in your room.
And if your provided data are reliable there is 30 Hz at 0 dB and a lot of boom above this frequency.
 
You could leave them where they are and see what effect blocking the ports with some foam or a washcloth has.
(Washed: personal recommendation) Socks and T-shirts are mainly recommended on this forum :cool:
 
Back
Top Bottom