Why does the Audyssey MultiEQ target curve roll off on both ends?

[SundayAudiophile]

I've just used the Adyssey Multi EQ app for the first time, and I don't understand why the target curve contains a roll-off in the base and in the upper high range. I'm sure this has been asked many times, but I couldn't find an answer. My front speakers are reasonably hefty transmission line floorstanders, they are quite capable of room-shaking deep base (by "deep" I mean below 30 Hz), and they are set to "Large" - they should not be dialed down in the base region, and yet even for the L/R target curve rolls off the base.

So I guess my question is two-fold:
1) What is the reason they made the curve roll off on both ends way before sub-sonic base and ultra-sonic HF range? If they EQed from 15 Hz down and from 20 kHz up I wouldn't mind, I think that would have made perfect sense.
2) Should I use the curve editor to try to flatten it out on either end? That's very hard to do in the mobile app, by the way.

An additional observation: I've experimented with setting the filter cut-off frequency (the highest frequency up to which Audyssey will apply EQ) to 20 kHz, to 500 Hz, and finally to 20 Hz. I gave all 3 options a quick listen on a decently detail-rich and bass-rich piece of music, and couldn't hear any difference. Isn't that odd?
I'll try it with a tone generator and an SPL meter later to see if it really does EQ the base and the treble as expected.

 

[Pogre]

I forget the reason they roll off the highs, but on the other end it depends on your speakers. My Ultras were true full range speakers and Audyssey eq'd them flat all the way down.

You can always switch from reference to flat too. I don't think the highs are rolled off with the flat setting.

 

[SundayAudiophile]

Weird, I'm looking at the curve for my front speakers, they are set to full range, no crossover, I have no subwoofer (of which I informed the AVR properly) and you can see my curve above - it's rolled off in the lows.

With flat, I believe, you're not getting any room response correction whatsoever?

 

[Pogre]

Weird, I'm looking at the curve for my front speakers, they are set to full range, no crossover, I have no subwoofer (of which I informed the AVR properly) and you can see my curve above - it's rolled off in the lows.

With flat, I believe, you're not getting any room response correction whatsoever?

It depends on your speakers' bass capability, not the setting. What speakers do you have? What is their f3? I've measured my Ultra towers and they were flat almost down to 20 hz. My new speakers however, have a higher f3, which Audyssey measures and adjusts accordingly.

You can see there's a rolloff because they aren't as bass capable as the Ultras were. I have a pair of subs tho, so deep bass is a moot point there.

Flat is just that. Same correction without the rolloff, tho yours may still roll off the lows due to speaker limitations.

 

[SundayAudiophile]

Interesting, are you saying that Audyssey measures the low-frequency roll off point of my speakers (F3, F6, doesn't really matter which level exactly) and then applies a high pass filter at a slightly lower frequency? It's doing that to prevent the speakers (and the amp) from potentially overloading by the frequencies that the system cannot reproduce anyway, a sub-sonic filter, in essence, but finely tuned?

My speakers are hand-made by a local craftsman, so no brand to them. He claims F3 at 28 Hz but I don't quite believe him, it's likely somewhere in the 30s range. It also doesn't help that my MLP seems to be in a base null, although not a very deep one.

 

[Pogre]

An additional observation: I've experimented with setting the filter cut-off frequency (the highest frequency up to which Audyssey will apply EQ) to 20 kHz, to 500 Hz, and finally to 20 Hz. I gave all 3 options a quick listen on a decently detail-rich and bass-rich piece of music, and couldn't hear any difference. Isn't that odd?
I'll try it with a tone generator and an SPL meter later to see if it really does EQ the base and the treble as expected.

You should use a mic and something like rew if you really want to see what's going on. I've been deep, deep down this rabbit hole on several occasions. A few quick notes.

When you make a change with the app you have to save it and reupload to your receiver. I know this one is obvious but you'd be surprised how many folks don't realize that.
Any changes you make to the curve will only be applied to the "Reference" setting. Changes to the curve have no effect on the "Flat" setting.
There's a user made app/program out there called "ratbuddyssey" you can use to make really tight, precise curve adjustments. There's a little bit of a learning curve but it works really well.

Announcing ratbuddyssey - a tool for tweaking Audyssey...

Cornball name, I know, but it was that, or fraudyssey, and being a bit vain, I went with my name :p Anyway: I like the idea of the MultEQ app, but the execution left me wanting a bit more. I wanted to be able to precisely input my custom target curve points, rather than fiddling with a small...

www.avsforum.com

 

[Pogre]

Interesting, are you saying that Audyssey measures the low-frequency roll off point of my speakers (F3, F6, doesn't really matter which level exactly) and then applies a high pass filter at a slightly lower frequency? It's doing that to prevent the speakers (and the amp) from potentially overloading by the frequencies that the system cannot reproduce anyway, a sub-sonic filter, in essence, but finely tuned?

My speakers are hand-made by a local craftsman, so no brand to them. He claims F3 at 28 Hz but I don't quite believe him, it's likely somewhere in the 30s range. It also doesn't help that my MLP seems to be in a base null, although not a very deep one.

That's my rough understanding. It won't try to eq below your speakers' capabilities. My new speakers' f3 is ~34 hz in room and Audyssey rolls off the low end on them.

 

[SundayAudiophile]

Thanks for the explanation and the tips! I did upload after every change I've made, but it's good thinking on your part to point it out. And I have accidentally discovered the ratbuddyssey just yesterday as I was trying to find answers to my points of confusion. It's an awesome software to have, especially since the curve editing in the Audyssey app works very poorly on my tablet for some reason (as if the touch sensor doesn't work, but it really does).

 

[Gmoney]

It does that to help speaker sound better.