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In the Forum: Playback Listening
In the Thread: About speakers Imbedded Macro-Positioning.
Post Subject: There are no such a things as the “room problems”.Posted by Romy the Cat on: 5/25/2007
 George wrote:
I am not quite understanding part of what you say:

"It is very difficult to make a generalization about it but generally this quite “large bloomy space” will be a space equal to, I would say, 1/8-1/12 of the room dimensions."

Picking a room that is 15'x25' and applying 1/10 would give an AEZ of 1.5'x2.5'.

Next you say:
"Now you need…. to place both of your loudspeakers in the AEZ, trying to position the right channel in the most polarized region of your AEZ."

Is putting both speakers in the 1.5'x2.5' AEX temporary?

George, I was planning to go there in my next article but very briefly: the really of the rooms is not so exact. The "large bloomy space" in your room not will be 1.5'x2.5' but it will be rather a wide field with max gain concentrated along any size of that field. It is not the "active spot" in the room but rather an active zone in room and it is why I usually call it "Macro-Positioning" (as opposite to DPoLS Positioning that is very-very precise micro-positioning).

So, our task is not to fill the "active zone" wish loudspeakers but to place loudspeakers somewhere within the zone. For instance in my room of approximately the same demotions as your the "active zone" is ~3x6x3 and the speakers are ~ 12" apart across the long wall. Surely it is imposable to stick the speakers in the “zone” but it is possible to locate the speakers that the zone might be used. Let go for some practicality and use the standard off the shelf products for a common reference. Before the Macondo I used Avantgarde Trio upperbass horn. It was 140Hz Tractrix with no back chamber. Anechoicly the AG’ bass horn do on the people’s rooms those 140Hz – I measured it. However placing “active region” of my room the AG’s horn had minus 3dB at 85Hz right channel and 105Hz left channel. 85Hz and 140Hz are huge difference but it is not all – there are other factors. The major factor is that being placed in the “active region” the horn has a capacity to “turn to room on”  and the you begin to integrate your MF channels not with the upperbass horn but with the sound of the entire room. So, the key is to consider the sound of the upperbass in the “active region” as a new base reference and to build up the rest of the sound in the room from it, USING the room gain instead of fighting with it.

Yes, playing with hot spots in listening room it will be always a presumed not evenness of gain between right and left channel – it is not good. But here is where the DSET concept kicks in – who prevent you to fix the levelness between channels modifying gain for each channel? For instance I know that I have 1.7dB difference between the right and less bass channels, the little less then 1dB difference between the right and less upper-bass channels. With DSET it is very easy to put a little divider into input of a necessary channel to set the acoustical right-left channels balance leveled.

BTW, in my past whan I used Lamm’s ML2 for Bass the chasing that precise right-left channels balance was a major pain in ass to me. When I was asking Vladimir about prospective options of changing the ML2 gain he insisted that (paraphrasing and mocking) “ML2 is a perfectly calibrated mashie with very properly and precisely implement feedback and any changes in depth of that feedback will remove the amplifiers from the Stereophile recommended component list”. Then the very same Vladimir came up with his “ingenious” solution recommending me to substitute with 12AX7 in the ML2 input stage with 5751 that has 30% less gain. I remember I hanged up phone and was laughing... as proposing to change the gain of the open loop Lamm… did in fact changed the affective death of the feedback… (BTW, ML2 become very unstable with reduction of feedback).

Anyhow, the summation of this post is to get best (means more) out of room and the feel the rest with efforts of electronics. BTW, did I mention that doing it there is suddenly no such a thing as the “room problems”?

Romy the Cat

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