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#432303 - 05/24/19 11:30 AM Re: LFR1100 Active [Re: Ian]
Mojo Online   content
axiomite

Registered: 01/21/07
Posts: 6308
Because the mids and highs are enforced within the room lending a flat in-room response rather than a boosted response.

Now this of course depends where you sit in relation to your speakers. If you are sitting near-field, you are receiving mostly direct sound and hence an attenuated mid and high response. If you are sitting in the diffuse field, the response is flatter.
_________________________
A-LFR/1000-8/500v4x2 coming
1000-2,3,1500-3
100,160,QS10x2,800,M5,M3,M50 v4
had v2
Air N2 (someday)

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#432304 - 05/24/19 12:04 PM Re: LFR1100 Active [Re: Ian]
rrlev Offline
local

Registered: 09/25/09
Posts: 204
Loc: Boston Area
Originally Posted By Ian
Ah yes, the perfect 360-degree sound radiator. We are a still a long way off from that. I wonder how you would mount it in the room?

like a pendent lamp ... a chain from the ceiling. Back when I was an undergrad I worked as a tech for the Dept of Electronic Music at the University of Illinois ... the head of that department designed a pair of round faceted speakers that looked to be over a meter in diameter with drivers pointing in all directions. I saw and heard it once in a concert (with a drummer) but the music was one of his compositions and ... "electronic".

Originally Posted By Ian

The response curves of this device would all be identical and would need to have a similar downward tilt like we see in the LFR curves. As to how it would actually perform, all I can say is I would love to be in that blind listen test!

I'm missing to reason to the downward tilt to the curves as I thought that only had to do with matching the sound power of a bipole ... and ditto on being included on the blind test.


Originally Posted By Ian
Technically an LFR is a Bipole design but the linearity of the front and rear off-axis responses make it operate more like an omnidirectional.

In the listening window with walls in place ...



Edited by rrlev (05/24/19 12:15 PM)

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#432305 - 05/24/19 12:35 PM Re: LFR1100 Active [Re: Mojo]
rrlev Offline
local

Registered: 09/25/09
Posts: 204
Loc: Boston Area
Originally Posted By Mojo
Because the mids and highs are enforced within the room lending a flat in-room response rather than a boosted response.

Hmmm ... makes sense ... and answers my question to Ian

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#432306 - 05/24/19 12:44 PM Re: LFR1100 Active [Re: rrlev]
Mojo Online   content
axiomite

Registered: 01/21/07
Posts: 6308
Originally Posted By Ian
Technically an LFR is a Bipole design but the linearity of the front and rear off-axis responses make it operate more like an omnidirectional.

In the listening window with walls in place ...

Exactly!
_________________________
A-LFR/1000-8/500v4x2 coming
1000-2,3,1500-3
100,160,QS10x2,800,M5,M3,M50 v4
had v2
Air N2 (someday)

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#432307 - 05/24/19 01:47 PM Re: LFR1100 Active [Re: Ian]
rrlev Offline
local

Registered: 09/25/09
Posts: 204
Loc: Boston Area
The interesting concept for me is the idea of designing a speaker which is designed to interact with a room rather than making a perfectly flat one. To make this work you must be delaying the front signal to get the rear signal to your ears at the same time (with in the time window of human perception). The key must be distance from front wall because any other path would be unknowable and probably too long.

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#432310 - 05/24/19 05:14 PM Re: LFR1100 Active [Re: Ian]
rrlev Offline
local

Registered: 09/25/09
Posts: 204
Loc: Boston Area
Originally Posted By Ian
I had a chat with Andrew yesterday about the sub-out. We think this is a good idea. We can also add a switch to the DSP that would allow you to set the High Pass crossover for the LFR to match the subwoofer. It would be for use with at least two subwoofers (right and left) as there is one DSP per channel.

This is interesting for 2 channel music to get a perfect crossover match ... but for movies one would probably want to use the processor/receiver outputs. This allows one to use the LFRs low frequency output as part of the base room smoothing equation with the subs. Or is that the thought for when the DSP high pass is off?

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#432311 - 05/24/19 05:16 PM Re: LFR1100 Active [Re: Ian]
Mojo Online   content
axiomite

Registered: 01/21/07
Posts: 6308
This concept of a speaker playing nice with the room comes from the 50s. Bose was the early pioneer who exploited the concept mostly with a lot of marketecture. While everyone, including me, laughs at the Boses, there were a lot of things he did right. I can drop my 601 series III in any room, and to the untrained ear, they sound great! In fact, if you have an open concept, and are listening to music while grazing around, they are terrific! One of the things he did right was to kill the bass. In any typical room, bass is very difficult to wrestle with and that just turns off people who want to just "plug and play". I've lent my Boses out to four different friends over the years and they love them dearly. Of course then they listen to my v4 and are blown away with what they've been missing.

The rear LFR drivers enforce the "Early Reflections" curve. When this curve is brought up closer to the level of the Listening Window, magic happens! You get an enormous sound-stage and wrap-around with virtual images to die for. It's not as simple as just slapping on some rear drivers though. The front and rear drivers have to work in concert across the mids otherwise you get attenuation in the response. Bose knew that too. That's why his "free space array" at the top of the 601s has multi-directional tweeters yet a mid-range that points forward. He could not control mid-range reflections using analog means so he chose to reflect highs only.

Like you say, there is a delay somewhere but I can't be sure where or how much. I say that because those rear drivers are also reflecting off the front wall. To understand where you need to add a delay and how much that delay should be and for what frequency range(s), you really need to characterize loudspeaker behavior all the way around. Then you look at the curves and decide what you need to boost, what you need to attenuate, what delay needs to be added and of course that is some of the secret sauce right there. The DSP makes implementing all that so easy.

Here's the poem sung to the tune of "We Three Kings from Orient Are". This is my interpretation of the spinorama from stuff I've read mostly from Floyd Toole:

We six curves of Axiom are
30 years old we've come so far
every one eighteenth pi rad, an anechoic curve we add
of spinorama data not scalar.

Refrain:

O curves of tone and SPL
curves with similar shape and flare
gentle slope, low Q nope
perfect sound these curves foretell.

Direct sound real flat without any gain
"Axial Response" that is my name
simple content, most important
over all curves I reign.

Repeat refrain

A "Listening Window" nine curves mean am I
0 to +/-30 degrees across, 10 degrees down, 10 degrees high
within a dB, these curves must be
for listeneners to joyously sigh.

Repeat refrain

Image width, stability, timbre to tame
+/-40, 60, 80 across and 50 down and high's the game
most that we hear, bounce from quite near
"Early Reflections" is my aim.

Repeat refrain

A speaker's signature doth we take now
weighted mean of 70 curves is how
downward tilting, no broad wilting
"Sound Power" curve art thou.

Repeat refrain

The "DI" curve is the cash cow
the "Listening Window" from "Sound Power" take away now
closer to zero, it's a hero
listeners will procalaim a big "Wow!"

Repeat refrain

One last curve is for finesse
"Early Reflections" from "Sound Power" we minus
lateral prophylaxis, from far-off axis
"Early Reflections DI" shows polar bias.

Repeat refrain

Low DI with curves smooth and similar
disperse the sound as not to be insular
audio pornography, via sonic holography
sharp images spaced out renders them singular.

Repeat refrain

Axiom's direct radiators sound great when they're played
sound power declining 3dB per decade
if that DI, is a bit high
constant, low DI LFRs can be yours via trade.
_________________________
A-LFR/1000-8/500v4x2 coming
1000-2,3,1500-3
100,160,QS10x2,800,M5,M3,M50 v4
had v2
Air N2 (someday)

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#432314 - 05/25/19 12:35 PM Re: LFR1100 Active [Re: Ian]
Mojo Online   content
axiomite

Registered: 01/21/07
Posts: 6308
Rich, I don't know if these active LFRs will work in Massachusetts with that funny electrical code of yours...LOL!
_________________________
A-LFR/1000-8/500v4x2 coming
1000-2,3,1500-3
100,160,QS10x2,800,M5,M3,M50 v4
had v2
Air N2 (someday)

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#432315 - 05/25/19 03:46 PM Re: LFR1100 Active [Re: Mojo]
rrlev Offline
local

Registered: 09/25/09
Posts: 204
Loc: Boston Area
The laws of physics may be a bit different down here too.

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#432319 - 05/25/19 06:00 PM Re: LFR1100 Active [Re: Ian]
Mojo Online   content
axiomite

Registered: 01/21/07
Posts: 6308
Yeah...you pilgrims brought different laws over.
_________________________
A-LFR/1000-8/500v4x2 coming
1000-2,3,1500-3
100,160,QS10x2,800,M5,M3,M50 v4
had v2
Air N2 (someday)

Top
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