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An Enticing Marketing Story, Theory Without Measurement?

MRC01

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... A reason some people give for not liking any room equalisation is that ,even at bass frequencies, it messes up the direct sound which they believe they can hear as seperate from the room sound...
I use EQ and have not noticed this effect. I've always found the benefits far outway any possible defects, ...
I agree, yet with an important reservation: if the EQ gets too strong it starts sounding wonky. For example boosting a bass frequency more than about 6 dB can make it sound bloated, and this shows in group delay and distortion. Room treatment doesn't have this issue, and I've seen it make big differences, sometimes 12 dB or more, without any negative side effects so that's plan A for fixing room modes with EQ as a last resort.

Question: when correcting higher frequencies, does the reasoning go like this: If the higher frequency rise is caused by certain reflections, use room treatment to reduce those reflections if you can, before resorting to EQ. Because that will address the root cause making the sound cleaner, where EQ just tames the rise yet still clouded by the reflections that are still causing it.
 

j_j

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Again, you can't do much with room correction if your room stores way too much energy. Bear in mind that "fixing a dip" at bass frequencies means you have standing wave cancellation at the mic/seat, and that by adding more energy, you're increasing energy at the frequency that already stores too much.

Some degree of this is ok, but not too much.

Balancing overall shaping between speakers is, however, a big win.
 

j_j

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Can you please explain in more detail how to "balance overall shaping between speaker" in a typical listening room?
Simply put, you want the direct sound to be the same from all speakers, including delay, gain, and spectrum equalization.

Note, "direct sound". I said nothing about reverberation, and I would suggest that you not have highly pathological early reflections.
 

Krunok

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Simply put, you want the direct sound to be the same from all speakers, including delay, gain, and spectrum equalization.

Note, "direct sound". I said nothing about reverberation, and I would suggest that you not have highly pathological early reflections.
I see, thank you!
 
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Note, "direct sound". I said nothing about reverberation, and I would suggest that you not have highly pathological early reflections.
The reason an omnidirectional mic does not measure loudness is because no mic can measure loudness. Loudness is a subjective parameter in two senses. First, it is personal. Second, loudness varies with various factors even known to engineers as well as with attention. But you can devise measurement systems using mikes that relate to loudness.

To get Toole's critique you need to start by realizing that engineers are not omnipotently producing the sound at your ears. They are adding sound to your room. So efforts to make the sound at your ears match the electric input - the dream of engineers - are not targeting the relevant issues. You might say the correct sound at your ears is the electric signal plus the room minus the room. (There's an argument about headphones and the "knot-hole view" that I'll make another day.)

Improving sound means ensuring the cues defining the virtual sound object are minimally distorted by the process between the orchestra and your ears. Some of the cues to identity and localization are irretrievably lost early in the recording process. Others are scrambled in the room. So the improving stereo through psychoacoustics arises from addressing the scrambling in the room.
 

MRC01

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... "fixing a dip" at bass frequencies means you have standing wave cancellation at the mic/seat, and that by adding more energy, you're increasing energy at the frequency that already stores too much.
...
Yes, that has been my experience. EQing a null is pouring energy into a black hole. You're sitting at a null and the room is just going to soak it up without making much difference in level. And you're taxing the amp & speakers pumping out that extra power. Meanwhile, the extra energy can actually be counterproductive, worsening distortion and decay with only a minimal increase in level at the listener position.

I found the only good solution to a null is tackle it at the source with room treatment or repositioning.
 

Floyd Toole

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Yes, that has been my experience. EQing a null is pouring energy into a black hole. You're sitting at a null and the room is just going to soak it up without making much difference in level. And you're taxing the amp & speakers pumping out that extra power. Meanwhile, the extra energy can actually be counterproductive, worsening distortion and decay with only a minimal increase in level at the listener position.

I found the only good solution to a null is tackle it at the source with room treatment or repositioning.
OR, using multiple subs to attenuate the modes. There are generic arrangements for rectangular rooms and Sound Field Management addresses modes that are problematic at specified listening locations in rooms of any shape. In my room with four small SFM processed subs fhere are no audible modes in the sub range - the room is "gone", leaving only deep tight bass :) No bass traps required.

Not everyone realizes that multiple subs are highly efficient - more small subs are vastly preferable to a single monster sub.

All explained in Chapter 8 of the 3rd edition.
 

amirm

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Not everyone realizes that multiple subs are highly efficient - more small subs are vastly preferable to a single monster sub.
Indeed. The issue is accessibility of SFM. It is a shame Harman discontinued the JBL BassQ. Porting that into minidsp or some other DSP solution would be fantastic.
 
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Not everyone realizes that multiple subs are highly efficient - more small subs are vastly preferable to a single monster sub.
So for example 15m2 room which has all kinds of nasty modal issues would benefit 4x Genelec 7350 (8") subs with GLM (Their "sounfield management solution)? This fun would cost 4000Eur including the subs and GLM. Easy and affordable?
 

Floyd Toole

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So for example 15m2 room which has all kinds of nasty modal issues would benefit 4x Genelec 7350 (8") subs with GLM (Their "sounfield management solution)? This fun would cost 4000Eur including the subs and GLM. Easy and affordable?
My understanding of what GLM does is not at all what Harman's Sound Field Management does. See Chapter 8 in the 3rd edition of my book or:
Welti, T. and Devantier, A. (2006). “Low-frequency optimization using multiple subwoofers”, J. Audio Eng. Soc., 54, pp. 347-364.

However there are passive multi-sub solutions for rectangular rooms:
Welti, T.S. (2012). “Optimal Configurations for Subwoofers in Rooms Considering Seat-to-Seat variation and Low-Frequency Efficiency”, Audio Eng. Soc. 133rd Convention, Preprint 8748. Go to www.harman.com/innovationto download color versions of the plots in this paper
 
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Ron Party

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Indeed. The issue is accessibility of SFM. It is a shame Harman discontinued the JBL BassQ. Porting that into minidsp or some other DSP solution would be fantastic.
Shameless plug. I pulled my BassQ out of my system last year when I upgraded my SSP which now handles all bass management. If anyone is interested in a fully functioning BassQ...
 

Krunok

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Not everyone realizes that multiple subs are highly efficient - more small subs are vastly preferable to a single monster sub.
While I dont' have any doubts that this is indeed as you say unfortunate fact is that space-wise I can only afford to have one sub. My mains are linear downto 33Hz (-6dB) and 40Hz (0dB). I am kindly asking our advice reagrdin integration of one sub. I have planned to purchase Kef Kube 12b , it's a sealed box with FR as measured on the pic below. Sub has a feature to switch off the internal filter so I can construct my own XO and EQ filter on 2 separate convolution channels for the sub. My question is: is the optimal strategy to implement linear-phase high pass filter for mains at 40Hz with say 12dB slope and implement the same low-pass filter filter on sub or should I cut-off the sub at say 80Hz so that in the 40-80Hz range both sub and mains work together to help fight the room modes?

KEF-Kube-12b.jpg
 

Floyd Toole

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You said: "My question is: is the optimal strategy to implement linear-phase high pass filter for mains at 40Hz with say 12dB slope and implement the same low-pass filter filter on sub or should I cut-off the sub at say 80Hz so that in the 40-80Hz range both sub and mains work together to help fight the room modes?"

Linear phase is not critical, but acoustical summation of subs and sats is. This cannot be perfectly achieved for all channels - be prepared. Room modes are problems up to frequencies higher than 40 Hz so I would recommend 80 Hz, in a bass-managed system. 12 dB/oct is too shallow - too much overlap where acoustical interference can happen - it depends on the rolloff characteristics of your mains.

What will happen if you allow your mains and the sub to operate simultaneously is a lottery because "position is everything" when it comes to room modes. Chapter 8 in the 3rd edition explains. Personally, I would do everything possible to get at least two subs, preferably four into the room and bass manage them. Then your mains can be smaller, less expensive, and the subs do not need to be large. Small powered closed box subs are preferred.
 
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I wonder if it is helpful to consider the matter of multiple subs from POV of Toole's critique and cues for virtual sound objects. After all, if a real drum were played in your room, wouldn't it distort from the same eigentone influences? What's different about a virtual drum? How can a distribution of subs - no matter how beneficial to the FR at your chair - in any possible way more closely propagate the cues for the virtual drum than a single sub behind the main speakers at the origin of the virtual image?
 

Kal Rubinson

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After all, if a real drum were played in your room, wouldn't it distort from the same eigentone influences?
That is not the right way to look at it. You need the drum to sound as it was when recorded, not how it would sound in your room.
 
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That is not the right way to look at it. You need the drum to sound as it was when recorded, not how it would sound in your room.
First, are we talking about (1) the listener being "there" or (2) the drum being "here"? "1" has no defensible definition in light of Toole's critique except partially defensible with headphones or anechoicly maybe. But recordings can aim for an imaginary world that feels kind of like "1" - esp for people who don't go to real concerts and can produce great dramatic listening experiences like being in the Concertgebouw, esp with headphones.

"2" doesn't make a lot of sense either but it resembles the familiar proscenium theatre conceit and satisfies the Toole critique. "2" also leads to more productive thinking in terms of stage-managing the cues for virtual sound objects.

So, does Kal Robinson want to "play" the virtual drum in your room as per "1"? Is he recommending taking whatever sound is picked up from the spot the mic or mikes were mounted in, in whatever room it happened to be in, and drop the drum and the recording room into your room? Which delivers to your ears the drum, the recording room, the playback room, less the frustrating effort of your brain to subtract your room.

So you may ask, should we record anechoicly? I don't know but I think the explanation is something like Toole's observation about why omnidirectional mikes don't hear your room right.
 

Rijang

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Apologies if this is not the right thread, I asked in another thread but got no reply so thought I try here. With regards to sidewall reflection, does what Thiel is claiming for their powerpoint speaker ( early 90s?) have any technical merit?
1568250348046.png

with the driver position 45 degrees to the sidewall, the first point of reflection is significantly reduced right? The way I have it mounted right now, the coincident driver are aimed straight to my ears. Subjectively its like listening to headphones with the imaging of a loudspeaker. The stereo image is wider but with the vocalist still in the middle.
 

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amirm

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After all, if a real drum were played in your room, wouldn't it distort from the same eigentone influences?
The real drum has no sound of any room. The one recorded does. That is, the drums were not recorded in anechoic chamber. If you add your room sound to it, you are doubling up.
 
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