Ascendant audio testing results?

[gbegland]

I've looked around here and found lots of info leading up to the release of these drivers, but not much info after that. Jon, how did the tests with the ones you got turn out? You got some of the Atlas 12's, right? Still favoring the TC's for the Arvos? Thanks for all of the great information you guys. It is really appreciated.....going back to lurk mode now. Bye.

Greg Begland

[JonMarsh]

The TC's, especially with just a single VC connected, have performance better suited to a dipole application going up to 200Hz+. The Atlas have higher VC inductance, even just with the single standard 4 ohm VC. The Atlas will have higher output level in the 45-65 Hz area.

~Jon

[jdybnis]

Did you try wiring up a pair of Altas (Atlases?) in series using the 2 ohm coils?

http://ascendantaudio.com/Atlas%2012%20-%20Infinite%20baffle%20and%20dipole%20wiring.htm

Higher Qts. Lower inductance maybe?

[cjd]

Er... wasn't it the Avalanche 12 that was being tested as a possible TC competitor?

[JonMarsh]

Never did get any avalanche 12's- was initially promised, then I think they went somewhere higher priority.

The 2 ohm VC's are supposedly quite low power- weren't normally supposed to be used for a connection. I didn't see the Q modification I expected when testing for variable Q operation (different impedance on "tuning" coil)- level changed, but slopes and response didn't.

My interest at the moment is primarily dipole operation, and I also want good response up to 200 Hz+, which is kind of specialized or unusual for nominally sub woofer drivers.

One other driver I've seen with a lot of potential is a 10" RS sub prototype MarkK has- very nice behavior, and reportedly it's being improved further. That's some time away though- mid summer or possibly later?

[jdybnis]

According the AA website the 2ohm coil can be used in IB/dipoles. The idea is the drivers are excursion limited in IB and dipole configuration. (Chad also recommends wiring 2 drivers in series to get back up to 4ohms.)

That is strange about the Q not changing.

[Dennis H]

One guy on another forum said the Atlas drivers he tested chuffed pretty badly because of the small pole vent. Naturally, he got soundly thrashed by the AA fanboys for daring to speak such blasphemy. The Avalanche drivers look like they have a big pole vent so I'm guessing they would be more suited to dipole use.

[JonMarsh]

Yeah, my Atlas's did chuff pretty bad once I pushed them a bit, but initial testing was done at just 4V RMS. It was audible then, too. Push them to 10 VRMS, and Whoaa Momma!

Nice build quality, though, and fairly sensitive.

I'm familiar with the series wiring of the secondary windings, it wasn't possible in my test stand (single driver), and the VC inductance and chuffing kind of killed my interest. But I'd expect these to kick butt in a normal enclosure against similarly priced competition, like the Shiva.

[jdybnis]

The Le of the Atlas is spec'd at 0.86mH and the TC2+ at 1.04mH. I did some googling and I found that thread about the TC2+ and inductance on Madisound from a few months ago. It looks like the specs might not be worth much here.

What is the highest crossover frequency you would use for the Atlas in the dipole configuration that you tested?

[Dennis H]

What is the highest crossover frequency you would use for the Atlas in the dipole configuration that you tested?

As Jon already said, the Atlas is unsuitable for dipole use because of its chuffing (excess wind noise from the backside of the driver at large excursions.) It should be fine in a box or an IB where you don't hear the noise coming from the backside.

[jdybnis]

The chuffing shouldn't be a problem for me. I'm planning on using a pair of drivers back to back in a compact push-push W-frame. The backs of the magnets are going to be in contact with each other (or maybe with something solid in between them).

-Josh

[Mark Seaton]

The Le of the Atlas is spec'd at 0.86mH and the TC2+ at 1.04mH. I did some googling and I found that thread about the TC2+ and inductance on Madisound from a few months ago. It looks like the specs might not be worth much here.

The specs are accurate as they are defined... That is in comparing the Z at 1kHz vs. Re. Of course that tells us little about what it does closer to 100Hz or lower. LspCAD has two additional parameters of Leb and Reb. These two components are in parallel and both in series with Le. At low frequencies the shorted inductance can be very high in some woofer designs, and it is a bit more prevelant in higher excursion designs (long coil over lots of steel).

I recently measured both the Atlas and Avalanche 15 in the same, small sealed box. The Atlas indeed has an inductive peak and shelving of the higher frequency response. It is a good deal lower with the 2R coil shorted, and pretty significant with the two coils in series as a 6 Ohm setup. The Avalanche has a larger inductance at low frequencies pushing the bump in the response to lower frequency, although it is a broad hump, not a more defined peak as was often seen with the Stryke HE-15. You can certainly get smooth response to say 100Hz, but you will need some EQ.

If you look at the response to much higher frequencies you see the initial downward shelf after the lower frequency peak (below 100Hz) and then the response continues a more gradual downward slope out to 1200-1500Hz before a sharper top end roll off.

Measuring some of these super woofers makes you appreciate what some of the Lambda Acoustics drivers had achieved, even though the production versions weren't yet optimized for big excursion or small box suitability.

[Mark Seaton]

The chuffing shouldn't be a problem for me. I'm planning on using a pair of drivers back to back in a compact push-push W-frame. The backs of the magnets are going to be in contact with each other (or maybe with something solid in between them).

-Josh

You won't be happy if there is no venting capability for the rear pole piece. I would guess you would want a few inches between the back plate of the two drivers. Maybe you can re-configure such that they are both firing same way with the rear driver's cone facing the front driver's magnet.

[jdybnis]

Thanks for the input Mark.

I keep hearing about those old Lambda drivers. They're turning into something quite legendary. Those things didn't come cheap though. If I remember the prices right, from when I looked up lambdacoustics on the wayback machine, they were over $500 each for the all-out Apollo models.

EDIT: $469 for the 12" (with "only" 10mm xmax)

On my sub, are you thinking I'll run into heat problems without the venting? I might be trying to get too clever without making some dust and doing some experiments.

-Josh

[JonMarsh]

On top of what Mark pointed out, if you only use a single 4 ohm VC with the TC2, then the inductance is cut in half.

The Atlas has a more pronounced inductive roll off. Like other drivers, including the HE15 I have, you can EQ it flat, but that doesn't help the upper harmonic distortion, which also tends to suffer with high LE. This is why I like the balance in TC2+.

Note this plot:




The black line is the nearfield dipole FR with both VC's in series, and the measured distortion products at a relatively low drive level- 4 VRMS- that's still moderately loud. For comparison is the yello plot as a reference level, which is the output with one 4 ohm VC driven- note the difference in top end roll off and output level. I have distortion plots for that configuration, too, but not where I can quickly plot them.

Pole piece chuffing can also be an indicator for even order non-linearity. A push pull W cabinet will cancel that, but won't cancel the pole noise.

~Jon

[Mark Seaton]

Adding to what Jon commented on, I noticed significant air venting noise through the motor and gap venting as the pole vent was brought too close to a boundary. In other words, you want probably 2-3" behind it clear to allow reasonable airflow. When blocked, there were some odd other effects going on which were hard to identify as separate from the airflow noise through the gap, but regardless could be called undesireable.

On the Lambda designs, AE Speakers, formerly Stryke Audio, has the stock of the old Lambda parts and should likely be offering more of those in the future. We'll see where the price and performance fall relative to others.

[jdybnis]

Thanks for the info guys.

I'll probably revive this thread in a few months when I get the drivers and run some tests myself.