Tuning my Legacy Audio Studio HD's with OmniMic

[guitar maestro]

Even though these speakers will be replaced, I wanted to tune the frequency response as-is, even in such a horrid listening room (my office, lol).



Testing Conditions:

• Room size= 11' W x 11' D x 10' H. Pretty much worst possible (almost a perfect cube) situation to start out with eh? lol
• Room treatments= none
• Speaker Location= Near middle of room, toe'd in to listening position
• Smoothing= 1/6 octave
• Reflection setting (all, blended, only to)= All, since that is how it will actually sound at the listening position with all the reflections.
• Input= full-range short sine sweep
• Electronic EQ/Adjustments/tweaks=
  • Subwoofer/Main Crossover Frequency= 41Hz, -48 dB/octave, Linkwitz-Riley on both the LPF of the subwoofer, and the HPF of the high output (The dbx Driverack lets you set each one completely independently of each other, thus the flexibility)
• Initial Observation= the addition of the subwoofer greatly amplified the 1st harmonic of the room mode right around 51Hz, and of course the huge room-mode peak right around ~102Hz, right around the 2nd harmonic of pretty much all 3 room axis.

Now after adding in PEQ


Testing Conditions:

• Room size= 11' W x 11' D x 10' H. Pretty much worst possible (almost a perfect cube) situation to start out with eh? lol
• Room treatments= none
• Speaker Location= Near middle of room, toe'd in to listening position
• Smoothing= 1/6 octave
• Reflection setting (all, blended, only to)= All, since that is how it will actually sound at the listening position with all the reflections.
• Input= full-range short sine sweep
• Electronic EQ/Adjustments/tweaks=
  • Subwoofer/Main Crossover Frequency= 41Hz, -48 dB/octave, Linkwitz-Riley on both the LPF of the subwoofer, and the HPF of the high output (The dbx Driverack lets you set each one completely independently of each other, thus the flexibility)
  • Added Parametric Equalization to both Low- and High-Outputs
• Initial Observation= NICE work Oscar ! :D

Afterthoughts:

• Flat-Response is nice, but for anyone that hasn't experimented with tuning Frequency-Response, if you aim for flat it indeed sounds "thin" on the low-end, and if you have a very reflective room, the top-end might be too bright.
• I personally liked the top-end after tuning, but I know that once I add in room-treatments, it will hopefully clear up the sound, and will drop the top-end a bit, which wouldn't be all that bad either to be honest.
• The "thin" low-end needs some "oomph" with heavy metal, so I might play with the PEQ and GEQ a bit more. When I attempt to boost up the low-end (<120Hz) I most certainly will do my best to try and not boost frequencies near the room modes (51Hz & 102Hz, for these frequencies are not only louder via the huge pile-up of room resonances, they produce time-smear that cannot be EQ'd out, since they can linger around longer than the initial excitation-sound. I'm gonna try and boost up some bass frequencies between the room resonances so only the loudness artifact is heard, and hopefully not time-smeared room resonances.

Here is before & after tuning (both plots over-layed):





Thoughts/input anyone?

[philthien]

Pictures aren't showing up any more, I saw them this morning when viewing the thread on my phone, but now I can't see them from my computer running IE.

Getting the bass right for me has been an interesting challenge. I do not have a parametric EQ, I'm using software graphic EQ and my frequencies are preset.

Still not too bad at 30, 62, 125, and 250-Hz. I'd say the problems in my room were centered near 60 and 120-Hz, and the 60-Hz problem was so bad I felt weird cutting that frequency on the EQ as much as I did. I fought it for a long while, but I found a lot of the music with which I was very familiar just didn't sound right. In the end, flat won.

Another problem I ran into with flat bass was THINKING it was too thin/anemic. That was true listening to a lot of classic rock. When listening to newer stuff, though, it sounded very good. I'd say that adjusted flat suits more music than any other setting.

I wonder if this thread would have been noticed more if posted to the main forum.

[guitar maestro]

My heavy metal has plenty of deep bass, lots of 5-string bass stuff (and downtuned 4-string stuff), which is the reason I'm gonna play around with eq a bit more.

The pictures might be taking long to load depending on your internet connection.

Can a moderator please move this thread to the main tech talk forum?

[philthien]

My heavy metal has plenty of deep bass, lots of 5-string bass stuff (and downtuned 4-string stuff), which is the reason I'm gonna play around with eq a bit more.

The pictures might be taking long to load depending on your internet connection.

Can a moderator please move this thread to the main tech talk forum?

Another thing I'll mention is that, according to Olive/Toole, they look for a 1db/octave drop in output from 20-20k, because they say the room adds about 1db/octave (almost universally). So 20-KHz should be about 10db down form 20-Hz.

So if you're EQ'ing flat, and your room is adding 1db/octave, then they would sound bass-shy I think, or overly bright which may sound bass shy.

If I'm interpreting the Toole/Olive stuff correctly.

Google it.

[guitar maestro]

I understand what you are saying, and I can very well believe that the room reflections keep on adding and adding, but the mic measures all, including reflections. It all depends if you can see the added output that the room is contributing via reflections.
Had I chosen the "blended" setting, to remove reflections, then a flat response would indeed sound wayy too bright afterwards, because the reflections not shown in the plot would then add in SPL after the fact. Luckily I RTFM to make sure to encompass and include literally everything to make sure I tune to reality.

[philthien]

I don't have an Omnimic so I use AudioTools with a cheapie PE calibrated mic. AudioTools runs on IOS devices (phones, tablets), they might have an Android version, I don't know.

So I wasn't sure how the reflections were being included with the software you're using.

In the case of my AudioTools approach, I run pink noise through my player (which has the software EQ). I run AudioTools RTA or FFT and adjust the EQ on my player to get as flat a response as I can achieve.

I'm wondering what you'd find if you checked your room now w/ AudioTools even using using a phone's built-in mic, if you'd get a similarly flat line.

I will say your graphs (which I can still see on my phone) look awfully smooth for 1/6 octave smoothing, when compared to what I get in AudioTools.

[guitar maestro]

I'm wondering what you'd find if you checked your room now w/ AudioTools even using using a phone's built-in mic, if you'd get a similarly flat line.

I will say your graphs (which I can still see on my phone) look awfully smooth for 1/6 octave smoothing, when compared to what I get in AudioTools.

Well, I do have pretty good speakers that are factory matched to very tight tolerances. ;)

I do have another setup I can use. I have the dbx Driverack with its own Mic. It can output pink noise for which the dbx Mic is calibrated to be flat for. It shows the RTA on its tiny screen. I'll be sure to check it out, but I dont know of how much use it will be because of limited resolution. Also keep in mind the mic was not pointed directly at the speakers on-axis.

[stellarelephant]

This is cool. I don't really know what I'm talking about, but from looking at your first photo, it seems you had your mic backed up all the way to the rear wall. Wouldn't you want the mic to be in your exact listening position for the measurement?

[guitar maestro]

This is cool. I don't really know what I'm talking about, but from looking at your first photo, it seems you had your mic backed up all the way to the rear wall. Wouldn't you want the mic to be in your exact listening position for the measurement?

Yes sir. That is exactly where I sit.

[badman]

I'd take a look at the deltas and/or your gatings. The problem with letting your "final" FR drive things entirely is that it includes reflections, etc, that are perceived differently than direct sound, so adjusting it all to be "flat" actually swings the needle too far in many cases. I'd consider setting a limit to your eq of 3dB (looking at your graphs) above 100hz. It's also generally preferred to have a gentle downward slope on your in-room curve, EQing flat as you have tends to sound too bright.