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PMC Twenty.21 Bookshelf Speaker Review

Frank Dernie

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In-room response should be smooth but sloping down. Reason is that high frequencies are directional and there is more absorption of them in a typical room. Anechoic response should be flat since reflections are not in there by definition.

If we can get the production to occur with speakers with similar response, then we are golden.
I have always been bemused by this line of reasoning.
I have read it often but it only makes any sense if people do not want the frequency response level when they are listening.
Obviously a speaker which measures flat in an anechoic chamber will have a downward sloping FR in a room for the reason you mention but, logically, that means either people don't actually like a flat response when they listen to music or that the actual recordings have had their FR tilted up in mastering because the mastering room is absorbent and the mastering engineer compensates.

I am not disputing findings which have been published, but simply that the in room response should be smooth but sloping down is not "high-fidelity" to the input signal in an engineering sense, unless the input signal is always identically sloping up.
 
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amirm

amirm

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I am not disputing findings which have been published, but simply that the in room response should be smooth but sloping down is not "high-fidelity" to the input signal in an engineering sense, unless the input signal is always identically sloping up.
Which is indeed the case (although inverted: bass is lower than what it should be). It is assumed that there was room gain in low frequencies when music was mixed. So the recording itself has less of it. Otherwise it would say that the talent/engineer that approved the mix has entirely different preference than the rest of us.

Of course we don't know to what extent the room gain existed in the mixing/mastering room. So for some content we have to have one slope and for others, a different one. Hence my comment about needing them to stick to one standard. Just like it is done in video.
 

Thomas_A

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I have always been bemused by this line of reasoning.
I have read it often but it only makes any sense if people do not want the frequency response level when they are listening.
Obviously a speaker which measures flat in an anechoic chamber will have a downward sloping FR in a room for the reason you mention but, logically, that means either people don't actually like a flat response when they listen to music or that the actual recordings have had their FR tilted up in mastering because the mastering room is absorbent and the mastering engineer compensates.

I am not disputing findings which have been published, but simply that the in room response should be smooth but sloping down is not "high-fidelity" to the input signal in an engineering sense, unless the input signal is always identically sloping up.

Your logic does not make sense to me. A basically flat on axis response will have a power/energy response that tilts down in a recording room. Why should that not be the goal also in the user listening room?
 

BikeSmith60

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People that actually think a flat spectrum response in audio transducers are ideal to the human ear are exactly like flat Earthers. It makes no sense whatsoever and such a reponse would guarantee massively excessive high frequencies. It would be brighter than the sun. The typical and commonly accepted Harman curve is not flat, to cite just one example, and slopes downward as frequencies increase. Ill-founded opiniated positions and decades of psycho-acoustic research are two distnctly different things. Lots of silly opinions here that are incoherent with "Audio Science". You enjoy your flat Earth screechingly ideal speakers, I'll listen to music. No offense intended to anyone of course.
 

Soniclife

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This is to my knowledge not a standard correction made during mixing.
How could it be avoided being fixed in mixing and mastering? They are using 2 channels during the process, and multiple sets of speakers, if it does not sound as intended they fix it, this correction will be automatically baked into the recordings.
 

Thomas_A

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How could it be avoided being fixed in mixing and mastering? They are using 2 channels during the process, and multiple sets of speakers, if it does not sound as intended they fix it, this correction will be automatically baked into the recordings.

If you look at other sources, TV etc. Is the error mixed into the sound? Also, if it would be mixed into the recording, how should the frequency response of a center speaker look like? Linear or corrected? The equation is not possible to solve unless there is a multichannel recording.
 
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Soniclife

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If you look at other sources, TV etc. Is the error mixed into the sound? Also, if it would be mixed into the recording, how should the frequency response of a center speaker look like? Linear or corrected? The equation is not possible to solve unless there is a multichannel recording.
You were talking about stereo, not multichannel.
 

Thomas_A

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You were talking about stereo, not multichannel.

Yes, and as I know of there is no standard "Shirley" filter applied to central phantom image/mono signal during recording, i.e.corrections in the range of +/- 1,5 dB 1 kHz-10 kHz.

Toole knows about these flaws in stereo reproduction and suggests that multichannel should be used. Meaning, a center channel may solve the stereo problem, matrix decoded, but in that case what should the frequency response of a center channel be if there is a correction mixed into the stereo recording?
 

Thomas_A

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Sorry that the above subject is off topic, and has been discussed in other threads. Don't remember which ones though.
 

Soniclife

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Yes, and as I know of there is no standard "Shirley" filter applied to central phantom image/mono signal during recording, i.e.corrections in the range of +/- 1,5 dB 1 kHz-10 kHz.
But all mono tracks recorded go through EQ when they are mixed over 2 channels, till they sound right to the creators, the correction will be automatically baked into the human operators feedback loop.
 

Thomas_A

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sergeauckland

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I have always been bemused by this line of reasoning.
I have read it often but it only makes any sense if people do not want the frequency response level when they are listening.
Obviously a speaker which measures flat in an anechoic chamber will have a downward sloping FR in a room for the reason you mention but, logically, that means either people don't actually like a flat response when they listen to music or that the actual recordings have had their FR tilted up in mastering because the mastering room is absorbent and the mastering engineer compensates.

I am not disputing findings which have been published, but simply that the in room response should be smooth but sloping down is not "high-fidelity" to the input signal in an engineering sense, unless the input signal is always identically sloping up.

I see the logic of the downward-tilting in-room response being preferred, my reasoning is as follows:-

Imagine a recording done in anechoic conditions, i.e. there is a flat in-room response at the time of recording. (Ignore the small effect of distance as air absorbs high frequencies more than low frequencies, so even an anechoic chamber has a small downwards tilt).

Play this recording in a normal room, using loudspeakers that are flat anechoically, i.e. the claimed preferred response. The recording will sound natural as the room's downward tilting response will be the same for the recording as for all other everyday sounds.

However, if the loudspeaker does not have an anechoically flat response,, say with the now common upwards tilt, then this will counter the room's natural response and so the recording will sound bright.

So far so good, I think. What I am uncertain about, however, is whether a recording done in a real studio actually has the same response as anechoic conditions, if the recording room has it's own downwards tilt, then of course the recording will come out that way, but then could be EQed flat, but then the studio Control Room will have its own tilt (or not)!! So, we're back to the wonderfully named Circle of Confusion.

My preference is for anechoically flat loudspeakers in a comfortable for everyday activities room, as that will sound, to me, the most natural, but of course as always, it depends on the recording.

S.
 

AudioSceptic

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I have always been bemused by this line of reasoning.
I have read it often but it only makes any sense if people do not want the frequency response level when they are listening.
Obviously a speaker which measures flat in an anechoic chamber will have a downward sloping FR in a room for the reason you mention but, logically, that means either people don't actually like a flat response when they listen to music or that the actual recordings have had their FR tilted up in mastering because the mastering room is absorbent and the mastering engineer compensates.

I am not disputing findings which have been published, but simply that the in room response should be smooth but sloping down is not "high-fidelity" to the input signal in an engineering sense, unless the input signal is always identically sloping up.
I was thinking much the same, and doesn't this mean that a speaker should have a smoothly rising anechoic response to compensate for the inevitable "correction" in-room? I can't help feeling, though, that this would seem far too bright, even in-room.
 

Soniclife

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Thomas_A

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I don't see anything in his response that addressed the EQ point you brought up, but I think you should start a thread specifically for this point rather than bring it up in many different threads.

Toole specifically addresses the dilemma of stereo and also admits hearing those errors now and then. All current research points on that a speaker should be perfectly linear in response, and most if not all of this research has been done listening to a single centered speaker in mono. Placing the same perfect speaker in stereo will sound different with the same mono source playing. The equation is thus "impossible", and is the dilemma of stereo.
 

Sgt. Ear Ache

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People that actually think a flat spectrum response in audio transducers are ideal to the human ear are exactly like flat Earthers. It makes no sense whatsoever and such a reponse would guarantee massively excessive high frequencies. It would be brighter than the sun. The typical and commonly accepted Harman curve is not flat, to cite just one example, and slopes downward as frequencies increase. Ill-founded opiniated positions and decades of psycho-acoustic research are two distnctly different things. Lots of silly opinions here that are incoherent with "Audio Science". You enjoy your flat Earth screechingly ideal speakers, I'll listen to music. No offense intended to anyone of course.

You seem to be missing the point of what people here are saying. What you said is essentially the same as what Amir has just been saying. The decades of psycho acoustic research you refer to are what this site is pretty much founded upon, and also what is essentially ignored by the golden eared audiophile crowd.
 

Soniclife

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Toole specifically addresses the dilemma of stereo and also admits hearing those errors now and then. All current research points on that a speaker should be perfectly linear in response, and most if not all of this research has been done listening to a single centered speaker in mono. Placing the same perfect speaker in stereo will sound different with the same mono source playing. The equation is thus "impossible", and is the dilemma of stereo.
This is not addressing the point you were making about EQ. If you care about this start a new thread about it.
 

Thomas_A

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This is not addressing the point you were making about EQ. If you care about this start a new thread about.

Yes it is indeed addressing the point. If you accept the research that a perfect linear speaker evaluated in mono is the preferred one, you can mimic this sound in a stereo setup by applying slight EQ in the 1-10 kHz region. This will of course be a compromise, since a full compensation will apply to the center phantom image.
 

Sgt. Ear Ache

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I see the logic of the downward-tilting in-room response being preferred, my reasoning is as follows:-

Imagine a recording done in anechoic conditions, i.e. there is a flat in-room response at the time of recording. (Ignore the small effect of distance as air absorbs high frequencies more than low frequencies, so even an anechoic chamber has a small downwards tilt).

Play this recording in a normal room, using loudspeakers that are flat anechoically, i.e. the claimed preferred response. The recording will sound natural as the room's downward tilting response will be the same for the recording as for all other everyday sounds.

However, if the loudspeaker does not have an anechoically flat response,, say with the now common upwards tilt, then this will counter the room's natural response and so the recording will sound bright.

So far so good, I think. What I am uncertain about, however, is whether a recording done in a real studio actually has the same response as anechoic conditions, if the recording room has it's own downwards tilt, then of course the recording will come out that way, but then could be EQed flat, but then the studio Control Room will have its own tilt (or not)!! So, we're back to the wonderfully named Circle of Confusion.

My preference is for anechoically flat loudspeakers in a comfortable for everyday activities room, as that will sound, to me, the most natural, but of course as always, it depends on the recording.

S.

Recordings aren't made just by listening on monitors in the studio. Headphones are used. A variety of speakers are used. I don't think the goal is ever to produce a recording that is "flat." It seems to me that the audio research done over the years has essentially found that a neutral, well-behaved speaker will sound the best in "most" environments. Then, we'll have to EQ from there to achieve the maximum audio nirvana.
 
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