REW for the first time

LCRLive

New Member
Joined
May 11, 2022
Messages
13
More  
Preamp, Processor or Receiver
Yamaha MGP16X, DBX Driverack Venue 360
Main Amp
Seismic Magnitude Series
So in other words, applying room calibration the same way we applied soundcard calibration so that it factors in and takes away what the room is doing to measurements. If a soundcard calibration can exist why can't a room calibration file to account for everything?

Basically a room correction calibration file is badly needed within this and other software like the Dayton one because most of us cannot afford or allocate space to build very large anechoic chamber testing rooms.

On soundcard calibration, this pic is what my pro 40 is doing. I was expecting this rack unit to be a lot cleaner than this.

Also wondering if there is some latency in the system, wont that completely screw up the measurement with some sort of phasing? or is the signal path for this thing properly compensating for all that?
 

Attachments

  • 16654635360077617658303639493590.jpg
    16654635360077617658303639493590.jpg
    231.9 KB · Views: 11
Last edited:

John Mulcahy

REW Author
Joined
Apr 3, 2017
Messages
7,212
The room's effect are in the time domain as much as the frequency domain, there is no static frequency compensation that can remove them. Reflections from the room's surfaces arrive later than the direct sound, so the primary method is to window the impulse response to exclude those reflections. The trade-off is that the shorter the window, the poorer the frequency resolution, so measurements need to be made with speaker and mic as far from room surfaces as possible. Measurements are sometimes made outside on elevated platforms for that reason.

There is always latency, even if it is only the time for the signal to travel from speaker to mic. It can be estimated and removed ("Estimate IR Delay" in the graph controls). A timing reference (such as a loopback connection on a second channel) allows consistent relative timing between measurements, the Measure dialog has a field to enter a timing offset figure to apply to measurements.
 

LCRLive

New Member
Joined
May 11, 2022
Messages
13
More  
Preamp, Processor or Receiver
Yamaha MGP16X, DBX Driverack Venue 360
Main Amp
Seismic Magnitude Series
The room's effect are in the time domain as much as the frequency domain, there is no static frequency compensation that can remove them. Reflections from the room's surfaces arrive later than the direct sound, so the primary method is to window the impulse response to exclude those reflections. The trade-off is that the shorter the window, the poorer the frequency resolution, so measurements need to be made with speaker and mic as far from room surfaces as possible. Measurements are sometimes made outside on elevated platforms for that reason.

What if I put large jenga-like random piles of foam on the floor in between the Mic and the speaker and replaced the drop ceiling tiles with special acoustic ones? (With a bunch of foam on top in behind up there too).
 

sam_adams

Member
Joined
May 23, 2017
Messages
285
What if I put large jenga-like random piles of foam on the floor in between the Mic and the speaker and replaced the drop ceiling tiles with special acoustic ones? (With a bunch of foam on top in behind up there too).

To achieve results like this:

55846


you will need several feet/meters of absorbing material on every surface in the room. This is not practical in rooms of average size. The above is the measurement of a single driver that was done in a very small room that has eighteen inches of dense polyester fiber fill on all the walls (floor to ceiling) and ceiling of the room. The measurement is 1M with no smoothing applied. The dips in response at 700 Hz and 1200 Hz were determined to be cancellations from the front and back of the baffle the driver was mounted on. The driver has pronounced breakup starting at 4500 Hz.
 

ddude003

AV Addict
Joined
Aug 13, 2017
Messages
1,403
Location
Somewhere Northeast of Kansas City Missouri
More  
Preamp, Processor or Receiver
PrimaLuna Dialogue Premium TubePre (2 channel+sub)
Main Amp
McIntosh MC152 SS Amp (2 channel)
Additional Amp
Yamaha RX-A850 Pro (the other 5 channels lol)
Computer Audio
MacBook Pro, Custom i7 7700k De-lid 2xAsus1080ti GFX Audirvana Studio, Hang Loose Convolver, Pulsar Massive & 8200, LiquidSonics, SoX
DAC
Chord Electronics Ltd. Qutest
Universal / Blu-ray / CD Player
Sony UBP-X700 /M Ultra HD 4K HDR & PS5
Front Speakers
Martin Logan ElectroMotion ESL
Center Channel Speaker
Martin Logan Motion C2
Surround Speakers
Martin Logan Motion 4
Surround Back Speakers
Martin Logan Motion 4 (yes, another set of these)
Subwoofers
Martin Logan Dynamo 700
Other Speakers or Equipment
Cifte 12AU7 NOS & Genalex Gold Lion Tubes in Pre
Video Display Device
Samsung The Premiere LSP7T UST Laser Projector
Screen
Elite Screens Aeon CLR3 0.8 Gain 103-inch
Remote Control
PrimaLuna, Lumin iApp, Samsung & Yamaha
Streaming Equipment
Netgear Nighthawk S8000 Streaming Switch, Lumin U1 Mini Streamer Transport
Streaming Subscriptions
QoBuz Studio Premier, Amazon Prime & Netflix
Other Equipment
ThrowRug, SaddleBlankets, WideBand & Bass Traps...
Along the lines of what @sam_adams suggests above... Look at the specs for a Vocal Booth... Google is your frenemy...
Basically a room 6x6x6 or 6x8x6 with acoustic absorption completely covering all and every surface... Not some random foam placement... Basically flat and dry from 20Hz to 20kHz and a reverb (RT60) of 0.2 seconds...
 
Last edited:

DanDan

Moderator
Staff member
Joined
Mar 10, 2018
Messages
743
Many many people have used REW for the first time. Many many of the questions are the same as it ever was....... They have all been answered a gazillion times.
 

LCRLive

New Member
Joined
May 11, 2022
Messages
13
More  
Preamp, Processor or Receiver
Yamaha MGP16X, DBX Driverack Venue 360
Main Amp
Seismic Magnitude Series
So once again I have been told by Parts Express that their Dayton measurement kit does room compensation for all the above discussed parameters but it only does so within a certain window so they still recommend treating as much as possible and with what i said I'm going to do in the room they said thats more than enough).

Although I dont know how the hell that is even possible because if you send a sweep with a particular speaker to get the room EQ, the how can the sweep itself be set to account for the speaker's own frequency curve? And same question goes for the actual room testing. If one is sending a sweep, we are at the limitations of the speaker's own inherent EQ curve in that sweep send so it would appear that even testing rooms would be compromised if a person is sending the sweeps with speakers which do not have perfectly flat frequency characteristics.
Which is now laughable in the most visceral sense of the term as most people have probably been running compromised tests.
 
Last edited:

JStewart

Senior AV Addict
Supporter
Joined
Dec 5, 2017
Messages
2,040
Location
Central FL
And same question goes for the actual room testing. If one is sending a sweep, we are at the limitations and test speaker's own inherent EQ curve in that sweep send so it would appear that even testing rooms would be compromised if a person is sending the sweeps with speakers which do not have perfectly flat frequency characteristics.

Uness you consider that the speaker and room (and the electronics in the signal chain) are working together as part of a system and it is the sound produced by the system you are measuring and correcting for.
Or am I not understanding your point?
 

DanDan

Moderator
Staff member
Joined
Mar 10, 2018
Messages
743
LCRlive said
Which is now laughable in the most visceral sense of the term as most people have probably been running compromised tests.

Seriously?
Abe Lincoln:- "Better to remain silent and be thought a fool than to speak and to remove all doubt"
 
Last edited:

DanDan

Moderator
Staff member
Joined
Mar 10, 2018
Messages
743
@LCRLive. I thought a little humorous jibe might help some cop on, but unfortunately not. You represent The Holy Trinity.... Loud Confident Wrong. Apparently you think most of us here are under some delusion, which you like to laugh at. Have you seen The Joker? In reality it is your fundamental ignorance of what is at play which is not funny, but sad. So ignoring humanity, to address your lack of technical understanding..........+1 to SStewarts effort to point you towards reality. I will add that the location of the speaker in the room changes how the room is driven, and indeed the room does also modify the output from the speaker to a smaller extent.
Most if not all measurement involves reference to a close tolerance standard. e.g. Metres of stone or platinum, or the original Kilo. in Paris, Atomic clocks broadcasting on the airwaves. Here, a Hi Fi forum, most of the speakers will have close tolerance and full range. Say +/- 3dB 30Hz- 20K. . Typical room anomalies can span 30dB and more.
 
Last edited:

LCRLive

New Member
Joined
May 11, 2022
Messages
13
More  
Preamp, Processor or Receiver
Yamaha MGP16X, DBX Driverack Venue 360
Main Amp
Seismic Magnitude Series
And
@LCRLive..... I thought a little humorous jibe might bring you to your senses..... Unfortunately not. Apparently you find the delusion which most of us here are under to be laughable. In reality it is your fundamental ignorance of what is at play which is not funny, but sad. So ignoring humanity, to address you lack of technical understanding......
Most if not all measurement involves reference to a close tolerance standard. e.g. Metres of stone or platinum, or the original Kilo. in Paris, Atomic clocks broadcasting on the airwaves. Here, a Hi Fi forum, most of the speakers will have close tolerance and full range. Say +/- 3dB 30Hz- 20K. . Typical room anomalies can span 30dB and more.


By you indicating a 30 Db or more variation, (why did you not write +/- 15 when you wrote +/- 3db for speakers?) you are including very acoustically unfriendly-shaped untreated rooms as a very invalid reference for this compare.

After a room is treated with panels and bass traps, a decent room would have a 15 db or less Window from which to begin to fine tune more professionally.

If one of the moderate to higher end builds, the +/- 3db window on speakers is about right. But I've seen even larger windows on stuff priced insanely high.

Compare to a +/- 1-ish db on an Adam S3V official measurements and one starts to realize that lots of snake oil seems to be greasing up the price tags in the speaker industry.
 
Last edited:

DanDan

Moderator
Staff member
Joined
Mar 10, 2018
Messages
743
why did you not write +/- 15 when you wrote +/- 3db for speakers?

Because- when two coherent signals sum, the peak is +6dB. When they cancel the null is zero. So, in a room cancellation dips are way bigger than peaks. Also the extents of whatever dB window is very much dependent on what smoothing is applied. I don't really get whatever point you are trying to make with the ADAM but I will point out that such extracts are pretty meaningless without considering the off axis responses. +/- 1 dB on axis strikes me as fanciful, I can't see ADAM claiming such nonsense. If you have questions they are welcome. But this strategy of enquiry by accusing everyone of delusion or ignorance is perverse. The Inquisition didn't work. Enough, or the naughty step.
 
Last edited:
Top Bottom