Beyond the Ariel

[BudP]

Russell,

Copy that opinion on the sweet sixteen, though, after a 32 cone EnABL treatment, it was at least musical at low levels.

The Nestorovic and Speaker Lab speakers were a bit unusual. Mille used a normal low pass filter for the smaller diameter woofer, at about 1K for an 8 inch, and then used his patented low low pass filter to turn off the larger woofer as it approached 50 Hz or so, gradually becoming a passive radiator. This system produced prodigious amounts of superbly colorful music at the bottom of the spectrum. Also required an incredibly robust smaller driver.

I know, I built them at his Lab for a number of years and got to participate in his design process while pretending to be his R&D engineer. I was that, but this mans fluency in combining test data with corrective listening procedures was just astounding to watch. I felt like a kid in a candy store, every day, for 5 years.

He does have a patent on this crossover so you may be able to dredge it up. He also has a number of other patents from his work at McIntosh.


Bud

[Pano]

Originally posted by Lynn Olson
Note the key concept is to select the widerange driver and build outward, starting with the tweeter.
........
You want all the drivers to complement the wideband driver, not the other way around, since it is the center of the spectrum

This seems like a great approach. Get the middle right, that's where the music is. Build up and out from there. The midrange is the heart of the music - you only fill in the rest of the spectrum to compliment the mids. Getting that good midrange is the challenge.

Very much the approach taken by Lukasz Fikus on his Lampizator Site.

[Graham Maynard]

Without wishing to criticise Lukasz' designs, there are two aspects puzzling me.

Yes the main (fullrange) driver is the most important, but Lukasz wires his out of phase with the supporting (bass-treble) drivers, which means that the predominant range responses of those supporting drivers are going to be out phase.

Also Lukasz tends to mount his tweeter below the fullrange, as opposed to what I think of as giving it 'air' above.

[agent.5]

If you are not familiar with this speaker, here's a picture (note the current design has 3 not 4 15" bass drivers, and the bass drivers are all in one panel which is attached to the mid/hi panel, logically, so one piece per side, not two):
http://tinyurl.com/32pgwe

Are the woofers attached to the front baffle? It is an interesting way to do a dipole speaker. More interesting than the standard big baffle, attached to a stand on its bottom.

I can see that the black pieces can be replaced with acrylic, and the woofers are attached to a separate, thin metal frame. It will be similar to an I-beam used in construction, but with two pieces of plastic connected by a piece of metal.

[Zen Mod]

Originally posted by Graham Maynard
Without wishing to criticise Lukasz' designs, there are two aspects puzzling me.

Yes the main (fullrange) driver is the most important, but Lukasz wires his out of phase with the supporting (bass-treble) drivers, which means that the predominant range responses of those supporting drivers are going to be out phase.

Also Lukasz tends to mount his tweeter below the fullrange, as opposed to what I think of as giving it 'air' above.

his spks are just from another realm

you can't realy criticize anything.......mebbe even xover schmtc is incorrect

but - with that approach,usual hair splitting is less important than in "usual realm"

[Variac]

Lukasz tends to mount his tweeter below the fullrange, as opposed to what I think of as giving it 'air' above.

I did that also, and it seems fine. I suppose there is a shorter path to the edge at the top that way but is that really an advantage? The side distance is the same... There's a lot of disagreement as to whether a small baffle realy gives "more air "

Or is that just the way you are used to seeing things? I did it to keep the tweeter at proper height in my speakers and because tweeter and mid are mounted in a single open baffle on top of a boxed bass speaker. By putting the tweeter below the mid, I was able to raise the dipole mid away from the horizontal surface of the box. Since the tweeter only fires to the front, it isn't affected by the proximity of the box below. I could have mounted the tweeter in the bass box but I wanted to be able to isolate the baffle from the box with rubber feet. I could have made the box shorter, but it was getting pretty deep and wide already. Sometimes it's fun to try other ways to do stuff.

I know Lukasz used to follow established ideas more rigorously, but seems to have "broken free" from over thinking this stuff. As choky says, he's on an other plane now!

Now with Lynn pointing out that the drivers are to be mounted off center in the baffle, I suppose I'd be more tempted to mount it above as it would be close to both the side and top. I am also influenced by how people normally do things...

Maybe Lynn has a more specific reason why having the tweeter in the middle might not be optimal. Might depend on you crossover freq. Mine crosses from bass to mid at about 200hz so I imagine I have some room to play around.

[rjb]

Re bass speakers in parallel on OB, it is interesting to read G.A Briggs experiments in the late 40's. See Chapter 17 in his book, "Loudspeakers"

[Lynn Olson]

Originally posted by panomaniac


This seems like a great approach. Get the middle right, that's where the music is. Build up and out from there. The midrange is the heart of the music - you only fill in the rest of the spectrum to compliment the mids. Getting that good midrange is the challenge.

Very much the approach taken by Lukasz Fikus on his Lampizator Site.

Originally posted by Zen Mod



his spks are just from another realm

you can't realy criticize anything.......mebbe even xover schmtc is incorrect

but - with that approach,usual hair splitting is less important than in "usual realm"

What a great site!!! I approve! Lukasz is a serious engineer - his CD mods are pretty much exactly what I'd do. Not mentioned are how the miserable op-amps found in just about every CD player - and I include the Sony SACD-1 - are too slow by a factor 20 to 100.

I am not joking. Looking at what comes out of the DAC chip, my friend Matt Kamna and I measured a flat comb spectra extending out to 20 MHz, and only descending into the noise at 50 MHz. That works to a slew rate over 1000V/uSec, far above the 13V/uSec of the ubiquitous 5532/5534. If the op-amp slews, it is 100% distortion during the slew interval. Even though this is lowpass-filtered (rather badly by the op-amp), the slewing distorts the amount of energy that should be present in the sample, creating a lot of HF distortion that is program-dependent.

Feeding the DAC output through a transformer that is electrically screened between primary and secondary, then straight into a tube grid, sidesteps the slewing, and also filters the RFI quite effectively. The output from the DAC is actually pretty good so long as it isn't slewed by an op-amp.

----------------

As for driver polarity, there are ways to keep all drivers in the same polarity, so long as you're willing to accept a 360-degree phase rotation at the crossover frequency. That's what the Ariel does, with an electrical 2nd-order network and an acoustic 4th-order crossover.

So if your constraints are mounting all the drivers on the same baffle (which puts the tweeter acoustically ahead of the woofer), and you want all the drivers in the same electrical polarity, increase the slope of the HP and LP network. The ratio of the HP/LP slopes sets the phase angle between the drivers, which in turn controls the vertical polar pattern.

I prefer an in-phase relation, with less than 10 degrees spread between the drivers. I find this inter-driver phase angle much more important than the broad-brush horizontal polar pattern - again, because the inter-driver phase controls the vertical polar pattern. Most important of all, small ripples on the skirts of the rolloffs shift the inter-driver phase, making the vertical polar pattern shift abruptly with frequency, which is very undesirable.

To continue the discussion of the previous page, after you select the widerange driver to meet your tastes (hemp or paper cone, Alnico or Neo magnets), you start the crossover design by coming up with a smooth (and I mean textbook-smooth) rolloff curve for the widerange driver. The driver will tell you where it wants to cross over - follow its guidance, not an arbitrary formula of driver size vs recommended crossover frequency.

You want to listen to the lowpass-filtered widerange driver with pink-noise (most important) and music before you add the tweeter. You want silky-smooth sound, rolled-off, but silky-smooth nonetheless, and most of all, musically valid and pleasant to listen to.

After you get a good-sounding widerange driver with a smooth rolloff, then you add the tweeter and its network - as before, designing a HP network with smooth curves, and trimming the crossover frequency to get a desirable in-phase relation between the drivers. Since inter-driver phase is difficult to measure at high frequencies, I temporarily reverse-phase the HF driver and measure the depth of the null. The null in the Ariel is 25 to 30 dB deep, indicating 3-degree phase match.

It takes a fair bit of adjusting and trimming to get really smooth transitions between the drivers - since the widerange driver and the tweeter are working at the edge of their ranges (that's why we need a crossover, remember?), we have to move things up and down in order to find a smooth region. Crossover smoothness translates to a vertical polar pattern that doesn't go through sharp transitions with small changes in frequency.

This can be confirmed by turning the system on its side, and auditioning with pink noise from a distance of one or two feet. It should like one driver, not two - if it sounds like two, you have phase-angle problems, and you need to re-visit the crossover.

[dmason]

I am another one who heard the Emeralds in Denver; I also was highly impressed by the overall presentation. Many people who were bowled over by the sound, while attributing it to Emerald Physics' implementation, I believe were in fact hearing the gestalt attributable to open baffle dipole sound itself. I asked three people, and in fact it was there first exposure to it. To be honest, I was impressed by just how similar it was in the midband and bass presentation to my own DarkStar. More similar than different.

I have ALOT of faith in Ciare's current offerings, and they have been putting out new designs like sparks off the ol' grindstone, and the Italians in general. For anyone interested in following Emerald's lead with Nd 8, might want to know that Ciare also offers an 8 inch and a 6.5 Nd wideband driver buried in their Home Line. The 8 looks as though it employs the same basic basket and motor, and could not but be a great driver. Its plot indicates to me that it could use some active contouring, which to me as well is fine, as I consider DSP pretty much mandatory, to get the most out of multi-driver open baffle rigs. Flattened out, it shows an honest ~96db all the way out. I like the 6.5 model even more, for a scaled-down condo rig, and I am about to order a pair from our friend "Validator," Thorsten Weber, at www.boxen-baustelle.de one of the good guys.

I also like that new Eminence Nd DeltaLite. The Kappa looks even better for $14 more. Now you can dive into a simple 2 way rig with state of the art drivers with Nd magnets. I also have great faith in Eminence, and their published FR plots. They have zero to hide. I would appreciate any more discussion on the idea of using the DeltaLite as a wideband driver; a low-rider rig, with just this and a compression driver on top. Using boundary gain with this one, you could add cheap bass on your way out of Costco. There are some outstanding choices right now, it would seem.

[Pano]

I was wrong about the Eminence Neos.
It's the KAPPALITE 3015LF that my buddy John has.

He's says it a slamming bass driver, very loud, very clean, but does not go high. Big X-max, too.