Did some RTA/Room measurements on my laptop.

[Beat_Dominator]

I found a cool program for checking the in-room response of your stereo and it's FREE!

The program is RoomEQ Wizard and can be found here http://www.hometheatershack.com/roomeq/

The program is aimed a little more towards setting the EQ on a subwoofer in a home theater but is capable of full-range response given that you use a suitable microphone. I used my trusty RadioShack condenser boundry mic, which has flat response from 20-18,000hz.

The forum that hosts that program has plenty of help available to set up the software and calibrate it.

Here is my initial measured response from 0-21,000hz. I was pretty happy to see it is fairly flat, there are a few dips that I'd like to work on but not too bad. Note that I do not own a SPL meter so the vertical scale is not calibrated.

 

[DTB300]

The program is RoomEQ Wizard and can be found here http://www.hometheatershack.com/roomeq/

RoomEQ is a great little program. ETF5 is another but it is limited until you purchase it, which makes REQ such a great deal.

Looking at the Graph, you are at about 40dB at 20Hz, with a 20+dB peak around 38-40Hz, then another similar peak around 160Hz or so, probably 2 octaves up from that lower peak. A low end EQ device like SMS-1 or Behinger would help tame those peaks and improve your overall sound tremendously.

It is great to see peaks instead of severe nulls, as peaks can easily be reduced, where nulls should not be increased.

To help really see the differences, run the test for results from 40dB to 80dB, and 20Hz to 200Hz, and see what the graph looks like.

BTW, great post as this is the new frontier of home audio.

Dan

 

[lugano]

Here is my initial measured response from 0-21,000hz. I was pretty happy to see it is fairly flat

Sorry Beat, but it's not flat at all. Flat is something you can judge on a scale which ranges from -3 to 3 db. Every 3 dB means a factor of 2 in amplitude. In poor words, 3 dB is twice as loud as 0 dB. Now, your measured amplitude range goes from 33 to 70 dB...

 

[Tj Bassi]

I'd like to try the EQ software but dont have a (good) microphone. Are there any particular mics I should be looking for?

I've spent the past week trying different crossover configurations but perhaps the software will help me iron it out better.

Tj

 

[Beat_Dominator]

Sorry Beat, but it's not flat at all. Flat is something you can judge on a scale which ranges from -3 to 3 db. Every 3 dB means a factor of 2 in amplitude. In poor words, 3 dB is twice as loud as 0 dB. Now, your measured amplitude range goes from 33 to 70 dB...

Oh I know lugano, it's just that I had seen much, much worse measurements from other people's posts. I didn't mean it was FLAT as much as free of any severe cancellations, by that I mean 20+dB dips that I saw elsewhere

This is all just a starting point of course. I have not moved any furnitur yet and there is a lot of stuff in my room.

I was thinking, would it be more worth while to measure only at the volume that I usually listen at? Or would higher volume be better for measuring?

 

[Beat_Dominator]

I'd like to try the EQ software but dont have a (good) microphone. Are there any particular mics I should be looking for?

I've spent the past week trying different crossover configurations but perhaps the software will help me iron it out better.

Tj

For affordable solutions I have heard that the Behringer ECM8000 Omnidirectional Measurement Microphone along with Behringer UB802 Microphone Mixer or Behringer MX602 Microphone Mixer are great choices.

 

[Kruppy]

Wow...this post comes at the perfect time for me. I've just started to run frequency measurements. DTB300 previous post on the RealTraps link got me going. I need to dig into this RoomEQ site. Thanks for posting it.

 

[Tj Bassi]

For affordable solutions I have heard that the Behringer ECM8000 Omnidirectional Measurement Microphone along with Behringer UB802 Microphone Mixer or Behringer MX602 Microphone Mixer are great choices.

Is a microphone mixer a must? What does it do for you?

Tj

 

[Beat_Dominator]

Most of the measurement mics are going to be condenser mics, they usually need "phantom" power to operate. The mixer will provide that as well as a more accurate method to set the gain.

 

[Beat_Dominator]

I took a lot more measurements, it seems that I have a pretty serious cancellation (I hope) at around 145hz.

I realize that it could also just be part of the woofer/panel integration, but I'm hoping it's just an acoustic issue

 

[SteveInNC]

Gee, just like this : http://www.martinloganowners.com/~tdacquis/forum/showthread.php?t=1245

As far as microphones, the original program doc recommended tying it into a RadioShaft SPL meter. I use the analog version. The author's site has or points to a downloadable correction table for the meter too. The software has a mode where you feed the output directly back into the input and it generates a compensation curve to handle the response characteristics of your PC's audio paths.

Note: I haven't touched this in awhile, so some of the features may have changed.

 

[lugano]

I was thinking, would it be more worth while to measure only at the volume that I usually listen at? Or would higher volume be better for measuring?

Well, what you try to achieve is a flat line at your normal listening volume, so I would measure only that.

For people like me, who don't have the possibility of moving furniture around, a separate equalizer off eBay might be the right solution. There have been some threads on that, search the forums with "equalizer" as search term.

 

[risabet]

Well, what you try to achieve is a flat line at your normal listening volume, so I would measure only that.

For people like me, who don't have the possibility of moving furniture around, a separate equalizer off eBay might be the right solution. There have been some threads on that, search the forums with "equalizer" as search term.

Why would volume matter? The FR of the room isn't amplitude dependent so it shouldn't matter.

Equalizers they tend to IME complicate things way too much. OTOH I haven't heard any of the newer DSP units.

 

[Beat_Dominator]

I'm in the "purist" camp, by that I mean an EQ in the audio chain is EVIL! Simplicity is my audio mantra and moving furniture is an easy fix

 

[DTB300]

I'm in the "purist" camp, by that I mean an EQ in the audio chain is EVIL! Simplicity is my audio mantra and moving furniture is an easy fix

I would agree for Mid and High end - but I have never heard the Tact system which most rave about. For low end, using a current model EQ (Behringer, SMS-1, SVS is coming out with one) to remove those peaks, which are shown in your graph, will not degrade the sound like you think it would. In fact once you attack and cure those, your low end will improve in sound quality.

I bet if you reduce the peak of the 38-40Hz area, the 160Hz area will also be aided.

Dan

 

[Beat_Dominator]

I have an NHT X1 crossover/eq for the substage..... when I add that

 

[lugano]

Why would volume matter? The FR of the room isn't amplitude dependent so it shouldn't matter.

Depending on your equipment, at higher volumes you are introducing some degree of distortion; the microphone's measuring capabilities may also suffer from a too strong amplitude.

 

[Beat_Dominator]

Depending on your equipment, at higher volumes you are introducing some degree of distortion; the microphone's measuring capabilities may also suffer from a too strong amplitude.

Yeah that's exactly what I was thinking. Though the differences might be slight..... might as well do it well the first time