Marantz AV7005 - Page 313

Thanks, avman09. I look forward to your results. Take all the time you need, no rush. I'd rather you be careful and methodical rather than rush to post.

[I'm sure many people outside of this thread would be interested too. Maybe you should start a new thread about it (since LFC is now found in several devices people might be curious about) ? Just a thought. ]
Edited by m. zillch - 5/16/13 at 7:44pm

I tested frequencies between 36 hz to 160 hz. It appears to be just an attenuator on a sliding scale. Physics prevails once again. The following readings were taken with LFC at its default setting of 4. I tried 1 and 7 as well and the results were as expected.

36,40 Hz -35 db

63,71 Hz -21 db

89,100 Hz -16 db

125 Hz -9 db

142.5 Hz,160 Hz -5 db

I did take reading from the other room downstairs but there really was no point because nothing above 71 Hz could be picked up by the RS meter due to the heavy attenuation. This tells me the other night whatever I was listening to did not have much low bass below 125 Hz, as I really did not perceived missing much whether LFC was on or not.
Edited by avman09 - Yesterday at 9:09 am

Thanks for testing! This is exactly what an AV SCIENCE forum should be all about, instead of the typical, "My external DAC has a much better sound stage, so I use Pure Direct" sort of drivel.

It would seem LFC doesn't do anything we couldn't replicate by simply turning down the bass, mostly the low bass, ourselves. Pretty much as I predicted.

Actually I thank you, it wasn't until you expressed your doubt that I suddely woke up and started wondering how could there be any magic other than just a more complex way of tone control. Yes your instinct turned out to be correct, it is not to say LFC not a smart and effective tool for some applications, but it is not some kind scientific breakthrough, most likely not patentable for example and for argument sake.

Your test has shown us what it does with a steady state signal. There is, I guess, a possibility that there is also a dynamic aspect, which, for instance, attenuates loud sharp peaks in the bass even further than what your measurements show. Who knows? Audyssey has a track record for not being entirely upfront with what exactly their technologies do: "It's like WAY better than our old gizmo, um, like 32 times better even! Instead of just taking X number of measurements we now take 32 times X number of measurements, for a grand total of a very large, impressive number called 'Y' !"

There was once a "magic" system, BTW, which reproduced deep bass using a weird psychoacoustic trick of generating the perception of deep tones by producing two other, higher frequency tones that had a beat frequency of the target low tone. [Aiwa or Panasonic maybe had it, I forget.] It came and went so I assume it was just a useless gizmo. I never did understand how they thought you wouldn't hear, and be annoyed by, the parent frequencies used to generate the target low frequency. Hmmm...

Good point, never thought of that possibility. I was also thinking of a painfully stupid but effective way to achieve something similar. That is, change all speaker crossover to 160 Hz and turn all subs off. Painful to do but if only have to do when you must watch a movie after midnight than it is at least viable.

AFAIK, when the sub is set to OFF, the FL/FR speakers are automatically set to LARGE so the crossover setting for those speakers would not be in effect.

Also, from the Audyssey website on LFC ....

Yes, I am aware of that, but that's why I said turn all subs off (meaning the power switch, not via speaker configuration) the sub instead of setting it to OFF, and that it would be a painful thing to do. Audyssey and the prepro/avr have no ways of knowing the subs are actually powered off, right?

That may be why the other night when I tried it I did not perceive a loss in bass. I thought it was mainly due to the content of the material I was watching, well that could still be part of the reason though. I should try it out again another time.

Zillch did mention there was some psychoacoustic "trick" used in the past, I guess what Audyssey is doing with LFC may have something similar in principle but probably can do a better job than whatever Zillch referred to in the past. Regardless, I do think it is a feature that I would use, albeit only very occasionally.

Ah ... yes, that would likely work then, although painful to be sure.

Although I agree neighbor complaints are due to more than just the sub frequency range bass, we now know thanks to avman09's testing [], that the sub range is definitely where the LFC acts most aggressively:
So simply disengaging the sub could maybe be a "poor man's" LFC control, in a rough sense, and if one found that getting up out of the Barcalounger and walking all the way over to the sub to turn it off [ especially without a beer and bag of potato chips in-hand, for the long journey} was too much of a schlep, one could easily make it a one-touch, remote control affair, by wiring in one of these (or similar) as a temporary "sub mute/LFC" switch, simply by selecting a unused input for "mute".


P.S. Having one's sub on an instantaneous A/B switch (no "warm up" delay or volume ramping time involved) also makes demonstrating to visitors, "Here's what a sub does", about a thousand times more effective. I speak from experience; I have it in my car and use it often. New folk "get it" instantly when you give them the control and allow them to toggle it on and off, instantly, at will.