Best Approach to Analyzing 400hz-20,000hz

[dwillis60]

I've spent quick a bit of time looking at my room's low end and I'd like to get some opinions on the other side of the coin--analyzing REW results for the 400kz to 20,000hz range.

As I described in a recent thread, I have a small 20x21x8 room that is used for home recording. The room serves as both a recording room and a mixing studio. It has a fair amount of room treatments, including numerous bass traps and broadband absorbers.

Is there a general way of evaluating REW data for the 400hz to 20,000hz range that applies to this type of room? I've looked at the SPL chart as well as Impulse Response, RT60 (Topt), and the Waterfall graph. Is there anything else that would be helpful? And are there any standards or benchmarks that I should be aiming towards when using each analysis?

I realize that this is a rather broad question, but I would appreciate any help I could get. Sometimes REW can seem overwhelming to newcomers and imposing some order on the results is often helpful.

I've attached my latest .mdat file in case anyone wants to talk specifics.

Thanks!

 

[John Mulcahy]

The RT60 plot will give you an idea of whether the room is excessively lively or excessively dead, yours looks like a pretty heavily treated room with a lot of absorption. Beyond that the region above a few hundred Hz is best left alone, the ear and brain tune out what the room is doing and respond to the direct sound from the speaker and its overall sound power response, both properties of the speaker rather than the room.

 

[dwillis60]

The RT60 plot will give you an idea of whether the room is excessively lively or excessively dead, yours looks like a pretty heavily treated room with a lot of absorption. Beyond that the region above a few hundred Hz is best left alone, the ear and brain tune out what the room is doing and respond to the direct sound from the speaker and its overall sound power response, both properties of the speaker rather than the room.

Thanks! That's an interesting perspective and it certainly makes room acoustics much simpler once the low end is managed. This looks like one area where psychoacoustics takes precedence over physics and engineering.

Having said that, I'm still left wondering if there isn't more. For example, I've read that the RT60 measure doesn't apply to small rooms. I notice that REW includes T20, T30, Topt, and the EDT. The results for my room show subtle differences among these measures and I'm wondering if there are any actual substantive differences that are meaningful. Or is this simply a case of "dead is dead." And at what point can we declare death? Are there any generally accepted benchmarks?

I'm also left wondering if there are any other bits of insight to be gained from the ETC under the impulse tab. My results, for example, show a first peak at about 4ms. This suggests at reflection at about 4 1/2 feet. Does this type of data tell me anything in particular? Should I be worried about my desk?

Thanks for your input.

 

[dwillis60]

My results, for example, show a first peak at about 4ms.
Thanks for your input.

Just to clarify...

This finding was from another run of REW that I did today. So it might not be present in the .mdat file I uploaded above.

 

[John Mulcahy]

Reflections are part and parcel of everyday life, we hear through them. There is plenty of controversy around whether reflections are something to hunt down and kill or just something to ignore (first sidewall reflections being a particular point of contention). There is a fairly comprehensive review of the research conducted on that in Toole's Sound Reproduction, third edition, which is well worth a read. Chapters 7 and 12 are particularly relevant.

 

[dwillis60]

Thanks for the wisdom and for the link!

 

[EarlK]

I realize that this is a rather broad question, but I would appreciate any help I could get.

Sometimes REW can seem overwhelming to newcomers and imposing some order on the results is often helpful.

I've attached a very nice pdf that was put together by 2 Acousticians.
- It includes measurement results ( some from REW ) and then offers a few subjective interpretations/guidelines to follow ( for the creation of a better listening experience ).

ALSO:

Googling "Small Room Acoustics" will return an abundance of info ( all needing to be sorted through ).
- It's best to first digest the 30 page pdf that I attached ( before following all those links ).
- Start with the included YouTube videos ( some are quite good ).

 

[dwillis60]

Thanks for that PDF. I'm currently diving into it (reading from the end to the beginning as I often do) and I've already happened upon a concrete statement that appeals to my need for order:

Standard: In room low frequency (LF) response measurement at listening position should be:

• Within +/ 10dB at 1/24th octave resolution from 20Hz to 250Hz for both speakers measured together.
  
  
• Within +/5dB at 1/3rd octave resolution from 20Hz to 250Hz for both speakers measured together.
  
  

 

[dwillis60]

Fantastic read! I'm sure their standards can be debated, but at least they lay down some benchmarks and an approach for evaluating the data. Anyone who is new to REW and working their way through the room evaluation process should put this on their must-read list. Thanks again for uploading the information.