Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Help interpreting room acoustics measurements
Help interpreting room acoustics measurements
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th August 2017, 04:26 PM   #1
kaputt is offline kaputt  Germany
diyAudio Member
 
kaputt's Avatar
 
Join Date: Sep 2011
Location: Berlin
Default Help interpreting room acoustics measurements

I finally bought a measurment microphone to be able to guess a bit less when building speakers. To use what's offered I also did room measurements that seem off. First the gear:
Dr. Jordan microphon (IEC60651 Class 2)
RME Fireface UCX interface (set to 96kHz)
FuzzMeasure 4 software, loopback function enabled
Class D amplifier board, flat from 20 to 20k
The microphone was placed pointing downwards onto a carpet, room center distance to carpet 1.5 meters.

Plots:
Click the image to open in full size.Click the image to open in full size.
Click the image to open in full size.

I hear a distinct slap echo after the sweep is done and always was aware of a very distict slap echo when clapping my hands. When doing the measurements I heard the sweep ring for about two seconds after the sweep. Neither the waterfall plot nor the RT30 plot seem to show any of that, right?
Am I misinterpreting the graphs or just expecting too much?
I would be happy if you could could give me some input on that matter. If you need more details, let me know.

*Dear moderators, I didn't know where else to post this, if there's a more suitable subforum please move it. (hoping this doesn't turn into one of these that end up in the Lounge )*
Click the image to open in full size.
__________________
Oh boy, I live in the snake oil thread...
  Reply With Quote
Old 17th August 2017, 04:36 PM   #2
fatmarley is offline fatmarley  England
diyAudio Member
 
Join Date: Aug 2003
Location: Cheltenham
Quote:
Originally Posted by kaputt View Post
(hoping this doesn't turn into one of these that end up in the Lounge )*
Click the image to open in full size.
Yes It's shame when that happens. I don't think they realise the value of some of the threads that are placed In the Lounge.

BTW - Can't see any of your pictures.
  Reply With Quote
Old 17th August 2017, 04:43 PM   #3
kaputt is offline kaputt  Germany
diyAudio Member
 
kaputt's Avatar
 
Join Date: Sep 2011
Location: Berlin
Click the image to open in full size.
Click the image to open in full size.

Sorry, in the original post the links don't show up for some reason, here are the images.
__________________
Oh boy, I live in the snake oil thread...
  Reply With Quote
Old 17th August 2017, 05:48 PM   #4
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
These are too small for me to read, but a slap echo you will see a dip and re-appearance. I do see that towards the lower part of the range, just below the second numbers I can't read.

The first signal has a strong bass mode. See how it vanishes and comes back a couple of times?

Best,

E
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.
  Reply With Quote
Old 17th August 2017, 05:56 PM   #5
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
Sorry, look at the initial plot. On the left is the highest point, that's the bass mode I see. now follow the Z axis towards you and you see it go away and return.
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.
  Reply With Quote
Old 17th August 2017, 09:53 PM   #6
kaputt is offline kaputt  Germany
diyAudio Member
 
kaputt's Avatar
 
Join Date: Sep 2011
Location: Berlin
I see theLF mode, the slap echo is more in the 1kHz range.
I tried three image hosters and with two nothing shows up and with the third the thumbnails don't get bigger when clicked...
__________________
Oh boy, I live in the snake oil thread...
  Reply With Quote
Old 17th August 2017, 09:56 PM   #7
kaputt is offline kaputt  Germany
diyAudio Member
 
kaputt's Avatar
 
Join Date: Sep 2011
Location: Berlin
Quote:
Originally Posted by eriksquires View Post
The first signal has a strong bass mode. See how it vanishes and comes back a couple of times?
So the slap echo doesn't necessarily show as a long extension in the z axis, but more in the fact that it decays and comes back again?
__________________
Oh boy, I live in the snake oil thread...
  Reply With Quote
Old 18th August 2017, 01:59 AM   #8
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
Yep. If you can hear it as a distinct set of "bam bam bam"

DIYAudio does it's own image hosting. Use big pictures, and click "Go Advanced" and upload your pics. Then once uploaded you'll see a list of pics. Right click, copy link, and then you can use the image icon.

Best,

Erik
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.
  Reply With Quote
Old 18th August 2017, 05:54 AM   #9
fluid is offline fluid  Australia
diyAudio Member
 
Join Date: Jan 2009
Unless you have your room or speaker calibrated when you measure a speaker in a room it is a combination of the two.

If you want to see how the room affects the speaker the ETC (Energy Time Curve) or spectrogram graphs are very useful. In the ETC you will see the impulse and then later in time the reflections. The spectrogram will give a different representation.

The length of the sweep you use will have a big impact on what you hear when listening to it. If you use a short sweep at a high level a very large amount of energy is output in a very small time, in a room that sounds really loud and is likely to excite the echo. Use a longer sweep and it won't sound the same when you listen to it.

Without seeing the scale of the graph it's hard to judge but the RT60 seems quite even and if it is the range of 400ms then it is a fairly normal room without much treatment. Your room won't be ringing for 2 seconds unless you live in a concert hall

A waterfall or CSD graph can be very tricky to interpret because it depends very much on the window settings you have chose. In all the graphs there is a trade off between frequency and time accuracy. When one is more accurate the other is less.

REW Room EQ Wizard is free measuring software that has good graphs and is familiar to a lot of people on this forum. It is free, try it out.

Is your microphone calibrated and do you have a 90 degree file? If your mic is calibrated for 0 degree (pointed straight) and you use it at 90 degrees there will be quite a difference in the range above 1kHz, if it isn't calibrated at all that adds another unknown into the mix.
  Reply With Quote
Old 18th August 2017, 01:13 PM   #10
kaputt is offline kaputt  Germany
diyAudio Member
 
kaputt's Avatar
 
Join Date: Sep 2011
Location: Berlin
I tried another time to attach images. Looks like it worked finally. Thanks for the heads up, Erik!
@fluid I'll try a longer sweep, maybe 10 seconds? Might doing sweeps with a limited frequency range be helpful? Like sweep 20Hz to 200 Hz in 5 seconds?

Another thing: when I wrote that I can hear the ringing of the room for two seconds after the sweep is done I only assumed that there is an issue with my measurements. Is it possible that my ears are ringing and not the room?
Attached Images
File Type: jpg waterfall.jpg (432.7 KB, 36 views)
File Type: jpg RT30.jpg (284.8 KB, 35 views)
__________________
Oh boy, I live in the snake oil thread...
  Reply With Quote

Reply


Help interpreting room acoustics measurementsHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Usefulness of In-Room LF Measurements vs. No Measurements (ref FH) sayrum Full Range 66 19th February 2015 08:44 PM
Need help interpreting measurements jimjimmyjimjim Multi-Way 5 26th September 2013 07:52 PM
Room Acoustics - Need Help icor1031 Everything Else 4 8th September 2011 01:09 AM
Room acoustics BrianVG Everything Else 35 6th March 2011 09:10 PM
Room Acoustics systemerror909 Multi-Way 4 21st January 2006 01:42 PM


New To Site? Need Help?

All times are GMT. The time now is 04:34 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki