"Phil Allison" wrote in message
u
"Arny Krueger" ..
"Phil Allison"
** Hang on Arny, what multi driver array has the 901 really got
?????
The answer is none. There is only ONE driver facing the
listener.
You are mixing the 901 up with the 802 PA speaker.
Phil, what are those two arrays of 4 speakers on the back of the
901? Or, am I imagining that I saw them there?
** Oh come on Arny !!!!!
OK, so we agree that there are in fact two arrays of 4 drivers each
back there, right?
** That is a red herring - Arny.
There is no significant "lobing and comb-filter effects" with a
driver array that is **NOT** facing the listener - compared with
one that is.
In most cases the back drivers on a 901 are facing a smooth wall.
Lobes bounced off a wall are still lobes.
** The lobes are spread way out by the off angle reflection and
lost to the listener.
A listener seated in the usual central position could not detect
them.
Furthermore, there are those oddities where the array has a critical
distance,
** Define your terms, please.
I've cited this paper once already, and it's clear that there aren't a lot
of people on this thread who have actually even glanced at it:
Author(s): Keele, Jr., D. B. Publication: JAES Volume 38 Number 10 pp.
723·748; October 1990.
Well, not everybody has the kind of library I have at my disposal. Sadly, I
can't find any online references with enough detail. The "critical distance"
w/r/t to an array of speakers is the point where the sound from the array
drivers starts to fuse into a single pattern. This is independent of the
reverberant nature of the room - it is actually most noticeable in an
anechoic room. The parameters of the fusion are frequency and array-design
dependent. This has the result that even aside from the lobing, the
frequency response of the array changes quite a bit as you move away from
it. At some point it stabilizes, but this is usually some distance from the
array.
So much for arrays in general. One strength of a good Bessel array is that
this effect is minimized. The dispersion gets smoother as you move away, but
the average response is more consistent at most practical distances. Just to
clarify, I'm not recommending using any kind of multi-speaker array for near
field critical listening.
This affects 89% of the sound coming out of a 901, if Bose is to be
believed.
** The "Hass" effect plus the extra proximity and brighter sound of
the forward facing driver normally makes it the apparent source for a
centrally positioned listener.
Already considered. Since I've been doing SR quite a bit I've learned to
love the Haas effect and figuratively take it to the bank every opportunity.
However, Haas Effect fusion is not perfect - there is some perception of
added fullness or fuzziness, depending on the individual perceptions.
The other rear facing ones will produce a delayed and duller sound
- depending on the nature of the walls, distance away and their
coefficient of absorption at various frequencies. If the walls are
far away and acoustically dead then the forward facing driver
dominates strongly.
Agreed that if the back wall is dead than much of what the back speakers do
is moot. However, most architectural features are not good absorbers below 1
KHz, less below 500 Hz, and very few below 200 Hz. Since all drivers in the
901 are supposedly full-range...
The "lobing ... effects" are only going to be audible if the
listener moves their head in the direct field where the lobes exist
- ie behind the 901.
Or as I've said once and feel somewhat put-upon to have to repeat - the
lobes will exist in front of the 901s if the walls are good reflectors. Bose
seems to recommend using a reflective back wall, see page 6 of
http://www.bose.com/pdf/customer_ser...ers/og_901.pdf .
The "...comb-filter effects" are audible where rear wall proximity
and reflection of sound creates them - it is not due to the way the
drivers are arrayed.
I've cited this paper once already, and it's clear that there aren't a lot
of people on this thread who have actually even glanced at it:
Author(s): Keele, Jr., D. B.
Publication: JAES Volume 38 Number 10 pp. 723·748; October 1990
Abstract: The Bessel array is a configuration of five, seven,
The title of the paper is misleading in that some of the "Bessel Arrays"
that are analyzed are really common configurations that we know and maybe
*love*.
IME both the 901 and 802 suffer from *gross* IM and Doppler
distortion at high SPL levels - nauseatingly so to my ears.
Well, that too. I think we're now agreeing about one of my earlier points
about how many small drivers it takes to equal a larger one. On a good day a
Bose 901 should be equaled or bettered in the bass range by a single long
stroke (i.e., JL Audio W7 series or equivalent) 8 or 10 inch driver.
On detailed inspection, the Bose 901 suffers from what now looks like a
really bad basic design. It was controversial when it was new, but that was
then and this is now. It's been around for about 30 years, right? I suspect
that even Bose would like to send it out to pasture.
For serious listening, if that's possible at all with a speaker with so many
inherent flaws, 901s should be used with a competent subwoofer.