Beyond the Ariel

[Zen Mod]

http://www.troelsgravesen.dk/philips9710.htm

4 pages of interesting info

[Salas]

Originally posted by Lynn Olson

Of course, it doesn't help that $tereophile measures the wrong distance (50 inches) when the industry standard has been 2 meters (80 inches) for many decades. Even for minimonitors, the wavefront doesn't "gel" until you get a minimum of 1.5 meters away - and the distance is correspondingly larger for large speakers.

5 times the woofer's nominal diameter a distance, is enough to 'gel'.

[ScottG]

Originally posted by mige0
Hi



Puuhh, just finished reading the whole thread - it's all there - outlined in detail.

Bottom line: use the ALNICOs if you like its specific sound originating from its magnetic behaviour - otherwise stay away, there are severe disadvantages.

Greetings
Michael

And here I thought it was just the page..

Actually there are some problems with Alinco and suggesting a specific sound from the magnetic behaviour generally based on counter current flux modulation (..perhaps its somewhere in the thread, but after many pages I gave up).

Dan says something like "stay away from Alinco because it has soft compression like character due to an IN-ability to resist flux modulation.." Well.. that depends entirely on the field strength of the magnet (and any iron used to augment it - if any), its field "structure", the vc in relation to the field, and the amount of resulting counter current flux modulation (which is highly mms, excusion, current input dependent).

(..of course while stronger motors resist counter current flux modulation they also return stronger counter current flux modulation than weaker motors (all else equal). But it isn't equal. Again, you really need to look at mms and excursion to get a "feel" mechanically, then factor in how much current is being "pushed in" for how much counter current will be generated.)

A weak guitar speaker motor *MIGHT* display this behaviour. I would think that it almost certainly WOULD display this if the VC starts to leave the gap (..but then ANY moving coil will do that). Inside the gap its largely dependent on how long the gap is and how linear force is distributed by the motor.

However, most of these designs are very short gap "affairs" with low moving mass and low linear excursion. Keep the driver operating linearly, and it would likely NOT exhibit compression like behavior.

Ironically, consider what Dan sells to the public and industry alike..

HIGH MASS

HIGH EXCURSION

WEAK MOTORS along a LONG GAP

Now who's designs exhibit compression like effects at normal spl's?

[Variac]

The write-up on the Celestion Blue says it was derived from a radio speaker, ie an audio use. Might well explain its decent smooth and extended response. You are right, the Gold doesn't have the same charm- at least on paper.

Well, it looks like the Tone Tubby comes out of this recent discussion looking better than ever. After all this , I'm more curious and hopeful that the hemp drivers: TT and HA both are still prime candidates.

Lynn needs to order a pair of TT's ASAP!

[SunRa]

Hello,

I've read about the new proposed drivers. I was wondering... can't some more specific design guidelines help more when choosing the driver?

For example, it seems that 1st order crossovers are out of discussion, but what do you think about higher cross points in order to preserve a coherence (in phase, in distorsion character) in the midrange?

I know that Mr. Lynn Olson uses a rather high cross point in his Ariel (especially being a d'Apolitto configuration) at 3.8Khz. There are some other advantages when crossing that high besides the coherence in the midrange... like low distorsion coloration for the tweeter. Would this be for example a design tag worth discussing?

[Lynn Olson]

Originally posted by salas


5 times the woofer's nominal diameter a distance, is enough to 'gel'.

Not when there's a crossover and enclosure added to the mix. When you measure a speaker with a high-resolution realtime system (MLS with rapid updates), you can see the rapid fluctuations in FR as the microphone is slowly swept from left to right, and up and down. Beyond a critical distance, these smooth out - if the speaker is competently designed, that is.

The entry into the smooth region is quite abrupt and obvious when measuring different speaker systems. In practical terms, it marks the transition from the near-field, with its chaotic changes in response with changes in microphone position of a few inches, to the far field, where the microphone has to be swept across quite a wide arc to see any significant changes. In addition, the fine-grained ripples start to smooth out as well.

Obviously, there's no point to optimizing a speaker for best response at 1 meter unless it is specifically designed for near-field use, and marketed as such. Speakers designed for domestic listening are optimized for performance at 2 meters and beyond. In a multiway speaker, you can't optimize for nearfield and far-field response - you have to choose one or the other. This is especially true for any speaker larger than a minimonitor.

The $tereophile method of measuring at 50 inches falls between the two stools, being neither useful for a true far-field measurement nor close enough for near-field monitoring applications. A speaker optimized for $tereophile's 50-inch distance will in fact be wrong for distances of 2 meters or more.

[Salas]

5 times a 15 inch is 191 cm Lynn. 5 times a 12 is 153 cm. We followed this rule of thumb for 15 inchers and 12 inchers in prof reinforcement when setting up processors by unit then taking samples 15, 25, 50, 100m from a 2 or 3 channel array field as a whole or even further if delay towers were involved. In home audio I go 1.6m and over all the time. But your project is gonna use biggies so I did not mean 5 times a 5 incher or something.
The proper technical thing is: ''The engineering definition of the "far-field" is |Rp|>2D2/λ, where D is the diameter of the smallest sphere that can enclose all of the sound sources. ''
Hey! I am not a $tereophile proponent! You had the 'Ariel' published in PF and I had 'The Slim', remember? I dont think they ever published something else for building a speaker. Or not?

[Lynn Olson]

It was a conversation I tried to have with the S'phile staff many years ago at the CES and got absolutely nowhere. At the time, all of their speaker-measurement graphs were showing 15.75 kHz artifacts (in addition to the nonstandard measuring distance) I let them know they were getting broadcast TV signals in their microphone, which would corrupt the rest of the data with TVI.

I found that out the hard way by listening to my own microphone on occasion, and hearing the distinctive sync buzz noise of TV breakthrough. In the magazine, though, they "explained" the data by saying the computer monitor was interfering with the microphone. Wrong. I own MLSSA, and it doesn't run at the CGA display rate - it supports EGA and VGA only, which have quite a bit faster horizontal rates than NTSC television.

A few years later when I was on the editorial board of PF magazine, I was told the (unattributed) story that S'phile was actually proud of their lack of technical knowledge - that they felt it kept them "objective."

Frankly, I hoped it was nothing more than a rumor, since the magazine still has a make-or-break power for the US hifi industry. All it takes is one bad review, or possibly worse, one of those "damn-with-faint-praise" reviews, and bye-bye startup company. That's too much power in one set of hands.

[Lynn Olson]

Originally posted by SunRa
Hello,

I've read about the new proposed drivers. I was wondering... can't some more specific design guidelines help more when choosing the driver?

For example, it seems that 1st order crossovers are out of discussion, but what do you think about higher cross points in order to preserve a coherence (in phase, in distorsion character) in the midrange?

I know that Mr. Lynn Olson uses a rather high cross point in his Ariel (especially being a d'Apolitto configuration) at 3.8Khz. There are some other advantages when crossing that high besides the coherence in the midrange... like low distorsion coloration for the tweeter. Would this be for example a design tag worth discussing?

Well, this is an area where personal preference enters into the design. I aim for flat response and low coloration first, but dynamic range and low IM distortion follow closely behind. Other designer prioritize maximum SPL's, others go for perfect square waves, other adhere to THX criteria for home theater. All of these pull the speaker design in different directions.

The way things look now, I'm leaning towards:

HF: Radian 850-PB or 950-PB 2" compression driver + Azurahorn AH-550 Le Cleac'h-profile horn. (Alternates for the tweeter are the Mundorf Heil AMT tweeter, or possibly one of the big prosound ribbons.) The most likely crossover for the Radian + Azurahorn will be around 1.2 kHz at 12, 18, or 24 dB/oct, depending on what sounds best. The attenuator will be a custom 1-dB step autoformer or transformer from BudP or Dave Slagle.

Rear HF: One or two 18Sound XD125's horn/drivers facing backward and mounted directly below the MF driver, on the rear surface of the open baffle. They will have crossovers at 2.5 kHz or higher, and will have attenuation in 1 dB steps. Working together with the front HF driver, the rear HF drivers generate a hypercardioid pattern instead of the usual 90-degree dispersion of horn systems. One of the most important criteria for selection for the rear HF drivers are smooth responses free of narrowband resonances.

Widerange MF: 12" 18Sound 12NDA520 or 12" Alnico Tone Tubby, with a lowpass filter around 1.2 kHz. The to-be-determined topology of this filter would be developed first, and aim at the smoothest possible rolloff - this to be determined by measurement and audition on full-range source material. I don't think I'll be using a highpass filter on the MF driver, although this can be determined by audition. The MF driver is mounted at the top of an asymmetric open baffle, with the L/R distances to the edge of the mounting surface a Golden Section ratio of 1:1.618.

Midbass: Either a 15" Tone Tubby, a 15" 18Sound, or a pair of 12" drivers operating in push-pull. The push-pull variant would have the drivers in 16-ohm versions connected in parallel, and mounted side-by-side with one driver reversed (magnet facing out). The midbass drivers, of whatever type, will be mounted at floor level in a short box with an open rear and filled with recycled-cotton damping material.

The midbass drivers will have 1st-order lowpass filters tuned to offset the 1/f loss of the MF driver, which will start dropping off around 200 Hz or slightly lower. The midbass drivers will also have additional steeper-slope filters set to about 1 kHz or so, to prevent interference with the HF driver.

The expected response of the speaker system should be from about 70~80 Hz to 20 kHz, and efficiency in the 97 to 100 dB/metre range. The design target is flatness comparable to the Ariel, as good or better energy storage, 10~15 dB more dynamic range, and a dipole/hypercardioid radiation pattern over most of the frequency range of the system. It would nice if it sounded good.

[ScottG]

Hmm..perhaps something of an esthetic cross between a Linkwitz Orion and this:

http://www.sonicflare.com/archives/v...rald-audio.php

..obviously more in-keeping with the Orion's size.

I think a stable "resistive" impedance will need to be considered to keep with the "flat response" objective and still be used with amplifiers that react with impedance.