'Flat' is not correct for a stereo system ?

[dewardh]

Originally Posted by Davey

Nope, incorrect.

Here's what SL wrote about it:

"The midrange to tweeter transition region from 700 Hz to 3 kHz for the 1.4 kHz LR4 crossover was now level with the frequency regions below and above for a flat overall response. Extensive listening tests with known program material that I and Don Barringer (on the East Coast) performed with our modified Orions pointed to about the right level setting for the tweeter, but were otherwise not quite on the mark. When analyzing the theoretical shape of the frequency response curve it seemed obvious that the transition from midrange to tweeter was too steep. We therefore left the tweeter at its flat level setting and started to use shelving lowpass filters to shape the response. Immediately we found great improvement . . . "

ORION-3

Is he wrong about what he did ? ? ?

[Davey]

Deward,

No, he's not wrong, but nowhere in that statement does he specify that an electrical -3.2db shelving filter was applied to a "flat" acoustic response to achieve the final result. (You fellas are inferring something that he doesn't actually say.)

The "net" result of the ASP modification is a down shelving action, yes, (yielding a final non-flat acoustic response) but not anywhere near a -3.2db acoustic down-shelving action. It's less than 1db.....relative to the pre-Orion-3 specification/response.

I've posted electrical plots of the ASP before/after response.......I've explained the details of the electrical modification......I've stipulated that SL's description is confusing......etc, etc. John K. appears to be the only one grasping this modification.....and even for him it took awhile.

Why is this so difficult to grasp?

Cheers,

Dave.

[dewardh]

Originally Posted by Davey

Deward,

No, he's not wrong, but nowhere in that statement does he specify that an electrical -3.2db shelving filter was applied to a "flat" acoustic response to achieve the final result. . . . Why is this so difficult to grasp?

Perhaps because further down in that link he writes the following:

"Revision 3 of the ORION is now in its 3rd implementation with Version 2. This became a necessary evolution because the frequency response of the loudspeaker can not be flat for stereo reproduction. The response has to roll down towards higher frequencies, but how?"

and presents a graphic showing Ver.0 (the referant in the previous post) at -1.8 dB, and Ver.2 (current) at -3.2 dB for the tweeter rolloff (relative to "Flat Woofer & Tweeter Setting") ? ? ? That graphic is pretty explicit . . . it's not difficult to see why it would be taken literally. You seem to be comparing the present tweeter response curve to some previous (unpublished) response curve . . . SL's own words seem to compare it to "flat" . . .

[gainphile]

Originally Posted by dewardh

SL's own words seem to compare it to "flat" . . .

That's how I read it.

And it's not difficult to grasp

[6.283]

See my post 471

The 3.2dB are compared to flat and "less than 1dB" is compared to Orion pre rev. 3.
Again, Orion was not flat before because it would have been too bright (and that is kind of normal with such speakers).

Originally Posted by Davey

John K. appears to be the only one grasping this modification.....and even for him it took awhile.

Sure ?

[Pano]

And why are you guys so hung up on the Orion? Did I miss something?

[kevinahcc20]

It was the Orion 3.2.1 modifications and SL's analysis of the technical basis of those mods that launched this thread.

[dewardh]

Originally Posted by Davey

I agree it's confusing.

As I read (and experienced) the “history” it went as follows:

+ Adding the rear tweeter made Orion+ too bright (if there was no tweeter level change)
+ Lowering the overall tweeter level (to correct the brightness) caused a noticeable midrange dip in on-axis response
+ That was “corrected” (to some extent, in rev3) by (mostly) restoring the overall tweeter level while adding a 1.8dB hf rolloff (among other attempts) with a higher inflection point and some other midrange adjustments
+ That proved not enough, and subsequent revision led to a 3.2dB hf rolloff on-axis (rev3.2) while maintaining the higher inflection point, which is where it stands now.

The “other” obvious solution, keeping it flat on axis and applying the hf rolloff only to the rear tweeter was not done because it would require additional amplifiers and electronics (not available in the asp) or a “passive” shaping circuit on the rear tweeter (fairly easy to do, but wouldn’t that be weird on an otherwise all-active loudspeaker). And there’s no single “right answer”, because so much depends on the behavior of the room . . . particularly the wall behind the speakers.

It all keeps coming back to the question of why we need the roll-off in power response, and whether it is acceptable to get it (in a constant-directivity loudspeaker) by rolling off the on-axis response or better to get it by changing the speaker’s polar response as frequency rises (which is what happens, by the way, in PLUTO).

[speaker dave]

I thought SL's main arguement was that he started with free field flat (outdoors, on axis) and found that too bright. He realized that a speaker at +- 30 degrees was at an angle where HF hearing is stronger, and so a centrally placed phantom source (equal level both channels) would be too bright. The several dB/decade slope was a correction for speaker position. Flat anechoic response is still his basic assumption of the best starting point.

In this discussion, whenever anyone says "flat" they really should be more precise. Flat on axis anechoic? Flat power? Flat reverberent field in a live room? They all mean different things.

David S.

[Pano]

Originally Posted by kevinahcc20

It was the Orion 3.2.1 modifications and SL's analysis of the technical basis of those mods that launched this thread.

Thanks Kevin, I guess I did miss that. (too many threads).