The BOSE 901 is placed about a half meter away from the wall, eight drivers facing the wall, four speakers tilted ~30° inwards, four drivers ~30° outwards. When the name Bose is mentioned there is nothing else than bashing, even that A.B. has invented something mustn't be said.
Yes, I remember those. John Cockcroft had some dotty TL designs in Speaker Builder magazine which referenced them.
Here's an interview with Roy Allison from 2010
Roy F. Allison Interview | Hi-Fi
and a Stereophile interview which talks more about room boundary effects
A Glorious Time: AR's Edgar Villchur and Roy Allison Allison Part 1 | Stereophile.com
Actually Bose and Allison's designs are discussed on p2 of the first interview
Page 2 | Roy F. Allison Interview | Hi-Fi
Page 2 | Roy F. Allison Interview | Hi-Fi
all I say is that theory of the "ideal" direct:reflected ratio of 8:1 is completely unscientific and that even from that theory it doesn't follow that You can realize that "ideal" in home hifi by using one speaker firing in the direction of the listener and 8 firing back and sideways into the walls as in Bose 901
this is all that I say, is it really "bashing"?
The logic of the Bose system was somewhat flawed (it's adding room reflection to the reflected sounds from the concert hall) but some people I know heard it and liked the effect. I've heard smaller Bose systems and thought they sounded fine for their intended, non-purist market.
The Jimmy Hughes ideas may be more specific to his type of speakers. The commercial Impulse design grew from the Lecson HL1 from the 70s. That had a mid horn from 400Hz and a treble horn above that. The original WW design, from which the Lecson was derived, had only one horn from 400Hz to cover mid and treble. The treble horn was added to make it sound better in showrooms (according to one of their major retailers with whom I corresponded at the time).
The Impulse has horn plus a dome tweeter, AFAIK. I'm not sure the same reflecting technique would necessarily work with all other types of designs, particularly if they had a broader spread of sound.
I'm sure reflector systems can be made to work - I heard an experimental one recently which sounded very good - but it may depend heavily on speaker/room combination.
The Jimmy Hughes ideas may be more specific to his type of speakers. The commercial Impulse design grew from the Lecson HL1 from the 70s. That had a mid horn from 400Hz and a treble horn above that. The original WW design, from which the Lecson was derived, had only one horn from 400Hz to cover mid and treble. The treble horn was added to make it sound better in showrooms (according to one of their major retailers with whom I corresponded at the time).
The Impulse has horn plus a dome tweeter, AFAIK. I'm not sure the same reflecting technique would necessarily work with all other types of designs, particularly if they had a broader spread of sound.
I'm sure reflector systems can be made to work - I heard an experimental one recently which sounded very good - but it may depend heavily on speaker/room combination.
as I understand the speakers that Jimmy Hughes' used in his setup were some highly directional horn designs so when one directs such speakers towards the back wall then basically what one hears (in the frequency band critical for spatial hearing) is just reflection off the back wall whereas with Bose 901 we have both full range direct sound which reaches the listener first and then a lot of reflections which generally come from behind the speaker
for me those two approaches are rather different but perhaps I am wrong
Look up the chapter about the Klippel experiments in Toole's "Sound Reproduction". From his experiments, a diffuse field of +3 to +5 dB (relative to direct SPL) was preferred by listeners, depending on the type of signal.
The problem that remains is that reverberant sound in typical listening rooms is not really diffuse, so it could very well be dependant on room size, acoustics. It might be more useful to measure the level of early reflections. Who can say?
In my room with an estimated critical distance of ~90cm (Omni) and a listening distance at 1.8m or a bit less it just works fine although the soundfield is not really diffuse. And you can easily hear when you are too far out in the room.The problem that remains is that reverberant sound in typical listening rooms is not really diffuse, so it could very well be dependant on room size, acoustics. It might be more useful to measure the level of early reflections. Who can say?
yes, +5 dB for music
The problem that remains is that reverberant sound in typical listening rooms is not really diffuse, so it could very well be dependant on room size, acoustics. It might be more useful to measure the level of early reflections. Who can say?
no problem - Klippel results are valid for typical listening rooms - exactly therefore Toole refers to him, it is because "diffuse" in this context means just "reverberant" or even "reflected" as it becomes clear when Toole concludes (page 459) about: "a requirement for a 3 to 5 dB difference between the reflected and direct sound fields"
Good point about the terminology used !
The practical way, though, will lead you via the RT60 route and that value is theoretically only valid in a diffuse field. But even if you use RT60, the result ("a little less than twice the critical distance") in a typical listening room is close enough. The last cm (or inches) are subject to taste anyway.
I first heard of the Jimmy Hughes ideas from one of his magazine articles, where he suggested that his readers try it, with whatever speakers they had.
If you have your speakers on stands and a suitable back wall, it would only take a few seconds to try it out. It is sort of whacky, and so pondering whether or not it would work, if it only works with midrange horns etc, is far more time consuming and inconclusive than simply trying it.
If you have your speakers on stands and a suitable back wall, it would only take a few seconds to try it out. It is sort of whacky, and so pondering whether or not it would work, if it only works with midrange horns etc, is far more time consuming and inconclusive than simply trying it.
unfortunately the usual way of things here is that...
an hour? how about many hours in 4 years??
I want to point out that diffuse field is a modern mathematical concept, and has existed on earth only a few hundreds of years after build up the first big churches and concert halls. Diffuse field is no requirement for anything. Human perception has not been excelled in perception of it in any way during the evolution.
Exactly. But this may also make a generalization about the required level of "reverberant" sound fields in small rooms (< 30 ms or so, above that pulse density would probably be sufficiently high, see also Bech's experiment) difficult since the direction and delay of the discrete components can be very different. That would not be the case if the sound fields would approximate a diffuse field (although a diffuse field is indeed not a necessity for spaciousness).
perhaps therefore Toole makes recommendations both as to the required general level of the "reflected sound" vs "direct sound" and as to the angle/direction and delay and also frequency spectrum of individual early reflections
a thought experiment: imagine a "Type 1" shaped loudspeaker but higher and wider and instead of just one tweeter a directional horizontal line of small tweeter-size fullrangers like for example Visaton BF32, sixteen of them for example - a horizontal array around 50cm long
let's forget about the (mid)woofer for a moment as for frequency band <500 Hz it can probably be placed almost just anywhere in the box as far imaging and soundstaging are concerned
in such a case of a floor level horizontal line array situated at the bottom of large tilted back baffle there would be no first order floor reflection, no first order front wall reflection and first order side-wall reflections will be very significantly attenuated because of high directivity of the array
only there would be a first order ceiling reflection and a lot of later ceiling and floor reflections
I wonder if such a speaker - with attenuated side-wall reflections - would retain the realistic recreation of space ability of a horizontally omnidirectional flooder, there would be still a lot of reflected sound
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Wouldn't that be the same as placing the 1 element flooder in front corner ? No 1st order floor, 1st order side wall and 1st order front wall reflections.
- Elias