Beyond the Ariel

[DeonC]

Forgot to add: the Rhythmic Audio system even corrects for things such as memory distortion. Here is a link to the Rhythmic Audio website:
Rhythmic Audio products page

Enjoy,
Deon

[DeonC]

Also forgot to add, the RA subs also have toggle-switch adjustments for the steepness of the XO slope (12dB/24dB), a rumble filter, adjustment for low frequency extention (14Hz,20Hz,28Hz), and damping (lo,mid,hi).

Greg, I'm curious to know what was your experience with the adjustments. How easy or how hard, and how different for the different venues and needs (studio vs. home).

Thanks,
Deon

[pos]

Originally Posted by Lynn Olson

I have no idea if servo feedback is audibly cleaner than a non-feedback setup, partly because perception of IM and THD in the sub-80 Hz region is fairly low (compared to the much more critical region between 1~5 kHz). Maybe it sounds better, maybe it doesn't.

The problem with VLF distortion is that it happens at frequencies where the ear is much more sensitive, and can easily appear louder than the signal itself:

Woofer measurements

This means that if the 40 Hz 2nd harmonic of a 20 Hz tone is at a 24 dB lower level, then it will sound equally as loud as the fundamental. This corresponds to 6% 2nd harmonic distortion. The 3rd harmonic distortion would have to be below 1%, or over 38 dB down, in order that it is less loud than the 20 Hz fundamental. It all leads to very low distortion requirements. The fundamental frequency sound pressure level needs to be above 70 dB to even become audible and it should not be masked by higher frequency distortion products.

[studiotech]

Originally Posted by DeonC

Also forgot to add, the RA subs also have toggle-switch adjustments for the steepness of the XO slope (12dB/24dB), a rumble filter, adjustment for low frequency extention (14Hz,20Hz,28Hz), and damping (lo,mid,hi).

Greg, I'm curious to know what was your experience with the adjustments. How easy or how hard, and how different for the different venues and needs (studio vs. home).

Thanks,
Deon

Well, we've ended up with pretty much the same settings at my home and the studio. Max extension(14Hz), highest damping setting(this switch has a tremendous effect and can take the subs from typical floppy sounding to super controlled and tight) and about 60hz crossover. I should note though, that at the studio we are using the BSS Omnidrove that controls the mains(Lambda and Beyma TPL-150) for crossover and EQ functions for the subs. At my home, I use the built-in crossover and parametric EQ on the Rythmik plate amps.

I've also heard others claim that the Rythmik stuff is just average or not that good. Well, it's all up to integration, isn't it. If you don't get them adjusted and mated with the speakers very well, of course the resulting outcome might not sound that good. Properly implemented, these subs are excellent.

Also of tremendous sound and quality would be Dannys take on open baffle servo subs over at GR Research. He is partnered with Brian at Rythmik on these. I've heard them several times and they are superb and dig really deep. He uses them successfully with his open baffle, high efficiency models with no problem, so in practice, low efficiency open baffle drivers are working just fine with nearly 100db/spl sensitivity speakers.

I also have to note that Bob Katz of Chesky Records and masterng fame has heard the subs and is impressed as well. Once he hard the mains, he thought they might be the best large monitors he's ever heard in a studio setting. Now they we added the subs, we are possibly surpassing the sound of his own mastering studio. I used to be an assistant for him many years ago and he is local in town here in Orlando.

Greg

[soongsc]

Originally Posted by Lynn Olson

Although I'm not always on the same page as Dr. Geddes, I agree about the desirability for multiple subs scattered around the room - three or four, for example.

One of the more annoying things about 2-speaker stereo is the conflict between speaker locations for smoothest bass and the speaker locations for best imaging. It is very unlikely these will be the same, and I personally prefer to optimize image quality, and use other methods to smooth out the bass. This is where multiple subs come in handy - and the more subs you use, the less acoustic power they need to radiate, since you're not trying to push power into an acoustic null.

...

What multiple subs do is to use lower energy to excite multiple modes so that the energy is scattered. This can improve performance such that you do not hear the concentrated peak or dip. The tradeoff is that the low frequency phase is now not coherent with the nature of the original musical instrument which may contain complex spectrum. What I have not tried is the double bass array arrangement which seems like a more technically desirable solution. Has anyone had any experience with it?

[DeonC]

What I have not tried is the double bass array arrangement which seems like a more technically desirable solution.

How does this work? I am familiar with the multiple sub solution, but I'm not sure I know this one.

Thanks,
Deon

[Josephjcole]

Red Spade Audio: Double Bass Array (DBA) bass integration

[charliemb]

Originally Posted by Lynn Olson

As with the Ariel, both the enclosure alignment and crossover architecture are optimized for source impedances in the 1~2 ohm range, which is typical for direct-heated triode amplifiers that do not use feedback. ... ... The new loudspeaker is optimized for moderate-power vacuum-tube amps in the 4~60 watt range, which covers most tube amps.

Wow serendipity. I was just getting around to asking about this and above is my answer.

An amp like mine with a Susan-Parker Zeus output power stage, also with no global feedback, and with the output transformer wired in 2:1 mode has an output Z of 1 ohm (right in the pocket). With a nominal 16 ohm load, the power output is ~26 Watts, again in the pocket.

This speaker is looking good.

In 4:1 mode, output is ~7.5 Watts, but the output Z is 0.25 ohms, perhaps too low. However, if only half of the windings are used, then output Z can be 0.5 ohms. Output Z easily can be brought up to the 1~2 range in 4:1 mode by using resistors instead of external links to wire up the 4:1 mode. If 7.5 Watts is enough (it should be), then the 4:1 OPT mode with the external resistor used as a link could be the best match because 4:1 mode measures the cleanest.

[DeonC]

Thanks for the link. Very interesting.

[hum4god]

Hi Lynn

are there more details about your resistive-vent enclosure for the Altec/GPA 416B Alnico documented somewhere ?
i am also intrigued by the concept but cannot find a lot of information .
so if you could shed some more light on that concept , and the results your are getting, that would be much appreciated .

regards
malcolm