Best Room Response

[QMuse]

But I agree with this 100%.

I also point out that exactly the same would be true of a resonance introduced at 5kHz, or indeed any frequency at all.

What makes 800Hz different from 5kHz in your opinion?

Room can still slightly misbehave at 800Hz, much less so at 5kHz.

What do you mean? At 5kHz there is absorption, reflection, and transmission. Same as any frequency.

Uh-huh. The ratio of absorption vs reflection vs transmission within typical room changes very much as you climb the frequency range. And that is the only reason why we have differnt room influence on speaker's response in the 20-300 vs 300-900 vs 900-20kHz ranges.

 

[QMuse]

This is the point we disagree on.

I argue that below 300Hz the steady-state response should be corrected because it is perceptually dominant.

This is not about whether the speaker or room dominate the steady-state response, but about which dominates our perception.

So far you failed to prove that.

 

[QMuse]

This is the point we disagree on.

I argue that below 300Hz the steady-state response should be corrected because it is perceptually dominant.

This is not about whether the speaker or room dominate the steady-state response, but about which dominates our perception.

I think MMM as a measurement method may be interesting as it correlates well with our perception. I can't prove it, this is just my opinion, but if you ask me I believe that resonance I tested with (+2dB at 650Hz, Q=4) would be audible in both scenarios, caused by room or by speaker.

 

[andreasmaaan]

So far you failed to prove that.

The reason you don't have evidence from me yet is that I'm trying to avoid merely deferring to authority

In the meantime, here's Toole's opinion on the topic (Sound Reproduction, p 348, my bold):

...if the loudspeaker is properly designed, there is little need to look at room curves except at low frequencies. So, what does it mean when a room curve closely matches the idealized target in Figure 12.4d? It means that the customer has probably selected excellent loudspeakers, and that, above the transition frequency of 200–400 Hz, no equalization is required; leave it alone.

 

[andreasmaaan]

I think MMM as a measurement method may be interesting as it correlates well with our perception. I can't prove it, this is just my opinion, but if you ask me I believe that resonance I tested with (+2dB at 650Hz, Q=4) would be audible in both scenarios, caused by room or by speaker.

The question is: would a nonlinear direct response to create a flat in-room response sound better or worse than a linear direct response resulting in a non-flat in-room response?

 

[QMuse]

The reason you don't have evidence from me yet is that I'm trying to avoid merely deferring to authority

In the meantime, here's Toole's opinion on the topic (Sound Reproduction, p 348, my bold):

Looking at these fine examples @thewas_ posted few days ago it seems not everyone agrees with Toole as majority of the filters shown there have corrections above 300Hz.

 

[QMuse]

The question is: would a nonlinear direct response to create a flat in-room response sound better or worse than a linear direct response resulting in a non-flat in-room response?

That is indeed the question. My opinion is that when MMM sees a resonance peak up to 900Hz I'm affraid my ears would hear it as well.

 

[andreasmaaan]

Looking at these fine examples @thewas_ posted few days ago it seems not everyone agrees with Toole as majority of the filters shown there have corrections above 300Hz.

In these examples, correction is from 20Hz to 20kHz.

I'm not aware of any science supporting that.

 

[thewas]

Prof. Goertz does not only correct room or claim so (as this way all his corrections would be very similar) but also the loudspeaker behaviour before his listening test, that's why his corrections are full range.

 

[andreasmaaan]

Prof. Goertz does not only correct room or claim so (as this way all his corrections would be very similar) but also the loudspeaker behaviour before his listening test, that's why his corrections are full range.

Do you have some further info concerning Goertz's theory (German is ok)?

The graphs you posted are labelled "mit Raum-EQ", and in each case the target response is identical, with a +5dB shelf below 100Hz sloping linearly downwards before reaching a flat response from 1000Hz up.

 

[andreasmaaan]

The ratio of absorption vs reflection vs transmission within typical room changes very much as you climb the frequency range. And that is the only reason why we have differnt room influence on speaker's response in the 20-300 vs 300-900 vs 900-20kHz ranges.

I disagree with this BTW.

It is primarily a case of wavelength vs. room dimensions, although reflection/absorption/transmission is a secondary factor, too.

It is equally a case of room volume and reflection/absorption/transmission:

Where T is Rt60 and V is room volume.

(Noting that this formula is derived in the context of large rooms as opposed to small rooms.)

 

[QMuse]

I disagree with this BTW.

It is primarily a case of wavelength vs. room dimensions, although reflection/absorption/transmission is a secondary factor, too.

It is equally a case of room volume and reflection/absorption/transmission:

View attachment 60164

Where T is Rt60 and V is room volume.

(Noting that this formula is derived in the context of large rooms as opposed to small rooms.)

Wow, interesting formula, unfrotunately it misses some parameters like wall density (weight).

So, you think that 20kHz wave is passing through walls as easilly as 20Hz wave does?

 

[andreasmaaan]

Wow, interesting formula, unfrotunately it misses some parameters like wall density (weight).

So, you think that 20kHz wave is passing through walls as easilly as 20Hz wave does?

If 20Hz passes through your wall easily, there is simply no way it will be able to generate a standing wave in the room, and the room will have no influence on the steady-state response at this frequency.

But honestly, if you don't accept that room dimensions are a fundamental component of the determinations of where the so-called transition frequency lies, perhaps you should rewrite the textbooks on room acoustics?

 

[levimax]

..if the loudspeaker is properly designed, there is little need to look at room curves except at low frequencies. (Sound Reproduction, p 348, my bold)

Seems like a semantic discussion of "room correction" vs "speaker correction" is going on. While Mr. Toole's research of "properly designed" loudspeakers is scientifically verified has there been any scientific studies on listener preference for EQ above Schroeder frequency of "improperly designed" speakers? I have some home made speakers with fixed active crossovers that have some FR issues which I can measure near field and listening position using MM RTA. I use full range EQ and my subjective preference is full EQ measures and sounds better. Amir has also been using EQ for his subjective speaker test as well and reports subjectively positive results. I think research in this area would be very helpful... not sure who would do it or pay for it though.

 

[DanGuitarMan]

The evidence you guys are putting forward is helpful to the discussion (@QMuse 's experiment and @andreasmaaan 's formula). It fits the ethos of Audio Science Review . There are some assertions being made without corroborating evidence to back it up, and that's derailing the train so to speak.

 

[thewas]

Do you have some further info concerning Goertz's theory (German is ok)?

The graphs you posted are labelled "mit Raum-EQ", and in each case the target response is identical, with a +5dB shelf below 100Hz sloping linearly downwards before reaching a flat response from 1000Hz up.

Unfortunately there is to my knowledge no article about it from him, also personally I don't fully agree to his target and it being the same for any loudspeaker and had sent him an email on those issues, but unfortunately never got a reply.

 

[QMuse]

If 20Hz passes through your wall easily, there is simply no way it will be able to generate a standing wave in the room, and the room will have no influence on the steady-state response at this frequency.

But honestly, if you don't accept that room dimensions are a fundamental component of the determinations of where the so-called transition frequency lies, perhaps you should rewrite the textbooks on room acoustics?

If you don't understand what frequency response your neighbours upstairs are hearing you should maybe pay them a visit when your speakers are cranked up.

Without going deep into physics, doesn't it struck you that we wouldn't be having 3 distinct frequency regions if transfer function of absorbtion/reflection/transmission would be a constant? I suggest you go and measure it when your speakers are playing pink noise.

P.S. In your simple formula RT60 is acting as a frequency related transfer function, which is also related to walls characteristics (primary material density), and it is certainly not a constant

 

[mitchco]

An interesting chart from SynAudCon back in the day when I was dealing with studio control room acoustics. As @QMuse has mentioned, the transition between wave acoustics and specular reflections is not a switch, but a gradual transition:

 

[QMuse]

An interesting chart from SynAudCon back in the day when I was dealing with studio control room acoustics. As @QMuse has mentioned, the transition between wave acoustics and specular reflections is not a switch, but a gradual transition:

View attachment 60181

Yep Mitch, that's exactly what I was talking about.

 

[Ron Texas]

When Toole says a properly designed speaker doesn't need EQ above 400 Hz I believe he means a speaker which is flat on axis. It seems reasonable to conclude if the speaker isn't flat on axis then using EQ to make it flat should make it sound better. I have found this to be true with the LS50 bump at 2200 Hz.

I suppose a post EQ response curve could be run through Olive's formula and the result would be a higher preference score.