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Old 28th December 2011, 02:05 PM   #1
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Default "Sense of depth" in loudspeaker soundstage ?

I am becoming a little obsessed on the above question

I'm currently listening to a pair of DIY open baffle speakers in a rather large-ish room(~20'x15'). I took me some time (years) to arrive at a loudspeaker that has a very good tonal balance to my years, low levels of distortion and a controlled (dipole) polar response, at least to my notion. I consists of Eminence Alphas 15A up to about 200Hz, where a 2D array of 8 "progressively" tapered 3" wideband drivers (Visaton FRS 8) takes over up to some 4kHz where they are crossed to a Neo3 PDR (open back).

These speakers perform quite well. The only (kind of) missing piece is the often-quoted three-dimensionaity of the soundstage some systems are able to convey with proper recordings. I am NOT talking about the sensation of diffuse "spaciousness" sensation, which is there, and also the speakers are able to render a wide scene with well-positioned instruments. I am talking about the sense of depth in the scene - which is well defined, but rather 2D.

Am I chasing ghosts here ? Any suggestions to what exactly make a loudspeaker+room capable of conveying depth ?
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Old 28th December 2011, 02:15 PM   #2
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Stereo recordings can convey depth only via amplitude clues and those clues being properly delayed from the main signal.

In the end it is an illusion that we interpret as "depth".

Among the things that can confound the perception of depth (or forward presence) are included early reflections (room reflections) of too high an amplitude and time/phase issues in the speaker itself. Placement and angle of the speakers and seating location also can make a big difference in the perceived sound stage.

Perhaps certain sorts of distortions in the system will also confound the perception of "depth".

To really see what ur speakers are doing, I suggest using only "acoustic" recordings, preferably ones that were recorded with two mics in true stereo. There are a number of labels that do this, Chesky is one (not for all though), there are numerous others. AND you can always go and record your own these days!

These statements represent the opinions of the poster and are not reflective of the staff or management of DiyAudio.com or any other person or organization on this planet. .

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Old 28th December 2011, 02:20 PM   #3
Salas is offline Salas  Greece
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This depth element is depending more in the electronics given the speakers are OK in my experience.
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Old 28th December 2011, 02:33 PM   #4
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I find depth difficult to do. As Bear says, reflections can kill it, especially reflections from the front wall. Absorption and/or diffusion there can help. Abortion is easiest, but can kill the mid-bass of open baffle speakers. With no wall at all behind an open baffle rig, I've heard depth that was simply amazing, but the low end suffered.

Getting the crossover right is a big help with depth perception. A digital crossover with variable delay and phase can be a big help with depth. It can be a long process, so don't be discouraged.
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Old 28th December 2011, 02:43 PM   #5
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Quote:
Originally Posted by bzfcocon View Post
I am talking about the sense of depth in the scene - which is well defined, but rather 2D.

Am I chasing ghosts here ? Any suggestions to what exactly make a loudspeaker+room capable of conveying depth ?
You may want to try out some horns. The quality ones are not only smooth but they convey a sense of depth that is lacking in domes and ribbons.
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Old 28th December 2011, 03:48 PM   #6
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I've always found small sealed boxes with high quality drivers can do the depth thing really well when partnered with excellent amplification (tube or solid state - krell always sounded more 'liquid' to me than any other solid state). I just prefer the sound of open baffle speakers these past few years (with their wider, more ambient and lifelike sound).
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Old 28th December 2011, 05:00 PM   #7
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i think if you've got a crossover in the midband (~2-3khz) then it needs to be really, really good and phase aligned over a very wide bandwidth. I really like the following "rule" to phase integration:

Quote:
Originally Posted by Phil Bamberg
Always expect to see a phase difference of less than 5 degrees at the cross frequency, 10 degrees within an octave on either side of crossover, and typically less than 35 degrees over a four-octave span centered at the crossover.
If your speaker follows the above, it could have that coherency that you're looking for. Your mention of "8 progressively tapered" midrange drivers was a bit of an indicator that the speaker probably lacks driver-to-driver coherency... and that's where the depth goes.
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Old 28th December 2011, 05:23 PM   #8
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IMHO a significant part of the sense of "depth" perception comes from the correct balance of low midrange/upper bass frequencies ranging approximately from about 150-300Hz. If there are deep notches measured at the listening position in this range due to floor and front/side wall boundary cancellation effects, (very common) sense of depth can suffer.

These boundary induced notches can NOT be fixed with EQ, but rather must be addressed with speaker design and placement. For example notches due to the floor bounce reflection and/or floor/ceiling modes that occur with a "high" woofer placement (anything above about 0.4m from floor to woofer centre) can be addressed in a number of different ways such as:

1) Lower mounted woofer (<0.3m) with suitable crossover frequency
2) Multiple vertically spaced woofers so the notch frequency of one woofer is filled in by the other(s)
3) Flanking subs with a sub very close to the main speaker and running as high as ~200Hz or so, etc.

For notches due to front and side wall reflections your options are generally limited to flanking subs as above, (for example just behind and to the outside of the main speaker) and/or making sure that the distance from the front of the speaker to front wall and side walls is different so both notches don't stack on top of each other.

If you can get a relatively notch free response at the listening position from 150-300Hz through placement/speaker design its then just a matter of applying a small amount of EQ in the <300Hz region to get the right balance - an overall error of only 1dB either way over the 150-300Hz octave (relative to the rest of the frequency range) I find can affect the sense of depth quite a lot.

I generally adjust this balance by ear as I haven't found a way to get a good correlation between the exact frequency response in this region (as measured in room at the listening position) and the balance sounding right. There are just too many room effects going on in this frequency range for this to be possible.

As pointed out by bear, sense of depth in a recording is an "illusion", and a delicate one at that which is easily upset, but it can be quite convincing with the right speaker/room setup and recording. (Many recordings don't impart any sense of depth, the best to test with are generally minimalist acoustic recordings)
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Last edited by DBMandrake; 28th December 2011 at 05:31 PM.
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Old 28th December 2011, 05:25 PM   #9
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Placing my speakers(closed boxes) right in the middle of the room and sitting at the sweet spot is the way i get this depth.
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Old 28th December 2011, 05:35 PM   #10
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Quote:
Originally Posted by Salas View Post
This depth element is depending more in the electronics given the speakers are OK in my experience.
3D is something i always strive for.

It is important that electronics preserve the information, but the speakers are very important.

Seems to be one of the things that EnABL enhances. In my experience it is almost an expected result transforming a flat soundstage into one that often blows out the wall behind the speaker. I often "measure" how good an untreated speaker is by how much it can portray a 3D stage. The new CSS VRX126 wide band mid (heard only once in a somewhat unfamiliar system) is the latest driver to impress.

3d-ness (with the appropriate recording) is the clue i use to tell an EnABLed speaker from its untreated version in blind tests.

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