my room responses - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #31 of 46 Old 06-04-08, 07:18 AM
Elite Shackster
brucek
 
Join Date: Apr 2006
Posts: 7,514
Re: my room responses

bob,

A couple points.

Usually waterfall plots are useful for frequencies below ~200Hz (BTW, it's a good idea to switch your waterfalls to logarithmic mode rather than linear). Above that, RT60 is used, and only when the room is large. You certainly are a candidate for that.

RT-60 displays the decay across the entire band or a selectable section of it (i.e.octave bands). It's basically reverberation time, the time it takes a sound to decay 60dB or 1,000,000th from its initial impact, or sound pressure level. It's very revealing and will show the fruits of the work you're doing. Think of what a church sounds like and you know what high RT60 is.

Generate the RT60 from the impulse response screen (after a full range sweep) and then take a look at the RT-60 tab. The scale is frequency versus time (in portions of a second from 0 to 1 seconds).. Ignore below 200hz. A flat line of about 0.3 seconds would be considered ideal.

I would be very interesting in seeing an RT60 of your room. (both 1/3 and 1 octave). It might show if you have enough or too much absorption.....

brucek
brucek is offline  
Sponsored Links
Advertisement
 
post #32 of 46 Old 06-04-08, 08:13 AM Thread Starter
Senior Shackster
Bob
 
Join Date: Mar 2008
Location: Barkhamsted, CT
Posts: 164
Re: my room responses

Hi Bruce, Thanks for taking the time to write and correct me! And keeping me on track. Here is an RT60, Is this what you are asking for?
Bob
Attached Thumbnails
my room responses-rt60.jpg  

acoustat6 is offline  
post #33 of 46 Old 06-04-08, 08:29 AM
Elite Shackster
brucek
 
Join Date: Apr 2006
Posts: 7,514
Re: my room responses

Yep, but we want to see it to 20KHz (as long as you're using a full range mic and not a Radio Shack meter)........... both third and one octave graphs (selectable on the RT60 page).

brucek
brucek is offline  
 
post #34 of 46 Old 06-04-08, 08:34 AM Thread Starter
Senior Shackster
Bob
 
Join Date: Mar 2008
Location: Barkhamsted, CT
Posts: 164
Re: my room responses

Hi Bruce, I am using a Radio Shack meter. I usually measure up 1250hz. Generally speaking should I measure up higher? Tonight I will do a measurement up to a higher freq, what do you recommend?
Bob
acoustat6 is offline  
post #35 of 46 Old 06-04-08, 09:04 AM
Elite Shackster
brucek
 
Join Date: Apr 2006
Posts: 7,514
Re: my room responses

Quote:
Generally speaking should I measure up higher?
With the RS meter I would limit the upper end to around 3KHz (they tend to be unpredictable after that). Even with what you've shown, I think it's going to be obvious you have a very low RT60. Quite the accomplishment in basically a big barn.

brucek
brucek is offline  
post #36 of 46 Old 06-05-08, 07:53 AM Thread Starter
Senior Shackster
Bob
 
Join Date: Mar 2008
Location: Barkhamsted, CT
Posts: 164
Re: my room responses

Hi Bruce, Here is a RT60 out to 3000hz. I still have 5 traps to finish and will post a graph when they are done.

When setting sub to main speakers distance we all see changes in freq response , is this because of phase? Is there one test in particular or a combination of tests that would show when the subs/mains are in phase?

I did notice the RT 60 changes when the subs are moved, would I be best served by getting the flattest RT 60? And would that indicate they are in phase?

Bob
Attached Thumbnails
my room responses-rt60.jpg  

acoustat6 is offline  
post #37 of 46 Old 06-05-08, 08:58 AM
Elite Shackster
brucek
 
Join Date: Apr 2006
Posts: 7,514
Re: my room responses

Quote:
When setting sub to main speakers distance we all see changes in freq response , is this because of phase? Is there one test in particular or a combination of tests that would show when the subs/mains are in phase?
The effects of the phase control and receiver time delays are only realized when speakers are played in concert with each other (sharing the same frequency). You will observe no effect of phase and time with a single speaker playing.

So, with respect to a sub and mains (for example), the area where the two are mixed and sharing the same frequencies is at the crossover frequency (i.e. 80HZ). The phase of the sub is adjusted to obtain the smoothest transition at that crossover area where the two meet (and somewhat above and below that). Simply taking successive measures of the sub + mains from 0-200Hz and adjusting the phase of the sub is the best way to make the adjustment. Get the smoothest transition. Using the RTA feature of REW with periodic pink noise is the easiest way to make this adjustment, since it's dynamic - you turn the dial and watch the response change at the crossover....

The phase control of the sub is a close approximation of the time delay in the receiver and can be used if there is no phase control available on the sub..

Quote:
I did notice the RT 60 changes when the subs are moved, would I be best served by getting the flattest RT 60? And would that indicate they are in phase?
RT60 is really only useful outside the modal resonance bandwidth, so it should only be considered above 200Hz. The subs have very little effect at this frequency and above, so ignore the subs with respect to RT60.
The best value for RT60 is debatable. It depends on the venue and what you're looking for. A higher RT60 might give the effect of 'space' and some might consider that desirable (church and stadium soundfields come to mind). In a studio, the engineer might want a very low RT60 across the spectrum to ensure intelligibility. A studio may be as low as 0.2 seconds.
In a large HT room, especially when the surround system is there to provide the 'space' soundfield, I read that a target of around 0.35-0.40 would be ideal across the spectrum (but some might like it higher).

Note where your RT60 is sitting.... it's actually below 0.30 seconds (and amazingly flat over the area you have measured - too bad you don't have the RT60 graph before you added treatment. If you have an original mdat file, create an RT60 and look at it). You're certainly getting that room quite dead (at least the plot looks that way). That may be your goal, I don't know. Is the sound that you experience to your liking now? maybe it's time to slow down on adding more treatment - I just don't know.

Your graph is one-octave selected on the RT60 page - try selecting third octave for a bit different view.

My experience with RT60 is simply book learnt, so I can't claim to be any kind of expert in this. It would be nice if others who are experienced would post on this.

brucek
brucek is offline  
post #38 of 46 Old 06-05-08, 01:48 PM
Elite Shackster
Maverick
 
Join Date: Mar 2007
Location: Sandnes, Norway
Posts: 1,384
Re: my room responses

I can only speak for myself and my room/system, but my RT60 is in the 0.2-0.3 range, and the room doesn't feel 'dead'. Quite the contrary, I'd say. It's not echoey, but certainly not overdamped. Very precise and focused.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Status: Sold!

To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Status: Done


To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Status: Sold!


To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Status: Sold!
atledreier is offline  
post #39 of 46 Old 06-05-08, 05:03 PM Thread Starter
Senior Shackster
Bob
 
Join Date: Mar 2008
Location: Barkhamsted, CT
Posts: 164
Re: my room responses

Hi guys, I do not have a phase adjustment or time delays on my subs. So my concern is getting the subs/mains in phase (if that is indeed the correct termonology) by moving the subs closer and further away from the mains, all of the time of course watching the effect of moving the subs in and out of the corner. I probably have a lot of measuring to do!

I posted a graph of my earliest measurements with two RT60s Taken around the same time. At this time, though, I allready had in place all of the bass trapping (around 24 fullsize traps, most in the front of the room) except for the last 16, which are almost completed. I am finishing up two low bass panel traps and two broadbands tonight. Then its the last three. Trust me its a big project putting up 16 2'X8' traps on the ceiling.

So the early RT 60s shows quite a change from my current RT60. I really wish I had a measurement before any room treatment, who knows how long it was?Also any other measurements such as freq response and waterfall would have been interesting to say the least.

I really like the way it sounds now I do not find it overdamped or dry. I find the dynamics to be much improved, bass keeps getting lower and tighter, imaging improves etc. Voices and instruments become more complete and natural sounding. If they could slice and dice your vegetables, bass traps would be the deal of the century.

I was curious a few weeks ago about my house system and how it would sound in the barn. Its not much more than a boom box, but I wanted to see the measurements and hear how it sounded. Bass trapping helped the boom box the same as it did to my main system, of couse it is noisy, limited volume, limited freq, limited dynamics, the speakers rattle and it sounds cheap. But the sound did improve and it actually sounded "decent" in its own limited way.

I do believe that even a system with a single driver would be helped immensly by bass trapping, well any system/speaker would be.

Bob
Attached Thumbnails
my room responses-old-rt60.jpg  

acoustat6 is offline  
post #40 of 46 Old 06-06-08, 08:40 AM Thread Starter
Senior Shackster
Bob
 
Join Date: Mar 2008
Location: Barkhamsted, CT
Posts: 164
Re: my room responses

Hi Atie, Just keep going with more bass treatment.

Here is my take on it.
At an absolute minimum for any room is floor to ceiling bass traps in corners, the thicker the better along with first reflection points with broadband traps. This will "take care" of major problems in the room and really is not intrusive for a listening room. I felt this was a major improvement in my listening experience when I did this and it encouraged me to keep going. I did not have REW to measure any of this at the time

The next step is treating about 1/4 to 1/2 of the room with a variety of panel and broadband traps. I do believe that this will get you 90% of what is required for great sound and most people (myself included) would be very happy with this amount. It eliminates most comb filtering, gets a very good freq response and a very good waterfall. Any serious audiophile with a dedicated room would be well served at this level.

I am not sure yet and question that much more than this is required. But an entirely treated room would not be "bad" and actually is better than less treatment but at some point the "law of diminishing returns" takes effect. I will do some sq foot measurements at some point and let you know exactly how much surface area is treated in my room. Now for me I would not have it any other way as I always like to take things to the nth degree. So for me if I were able to, I would add even more treatment, but I have effectively run out of walls that I would like to treat in my room.

Bob
acoustat6 is offline  
Reply

Bookmarks

Tags
responses , room

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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 is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome