Axiom Home Page Forums General Discussion Technical Questions Crossover Setting for Subwoofer?

joema,

In reply to:

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For a bass management setting of LFE+mains with M60s or larger, isn't there a potential problem with "bass doubling?" IOW from 60 to about 200Hz you have both M60s and sub producing bass.

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This is why you have to turn down the crossover on the subwoofer (not in the receiver) when you switch your mains to large or LFE+main.
You need to find the point of integration between the natural droppoff of the main speakers and the subwoofer crossover.
For example, my EP350 is set to about 50-55Hz on the cross which i find integrates pretty well with the M60 mains. A frequency sweep in my setup revealed no bass doubling and a pretty smooth transition from the mains to the sub.

Peter, I like this approach and have used it myself out of necessity, since my ancient DD receiver lacks variable LFE (though for simplicity, because of this absence, I usually just set everything to small on movies). But just curious, why do you need to set the xover on the sub instead of in the receiver? I thought the point of variable LFE was to allow you to fine tune that xover via the receiver?

Bman

Peter?
Who's Peter?
Isn't he gone for the day?

As I understand it, the stress relief benefits of adding a sub aren't trivial-

Earlier in the thread people questioned the benefits to the speaker, but the benefit to the receiver (less power to the speakers at the same volume, hence less distortion/clipping) seem pretty good as bass is what sucks up amplifier power.

I'd guess that each octave takes equal power to reproduce?

There is an alternative - the Outlaw ICBM-1 bass management unit. Outlaw recommends you select "LARGE" for all speakers, and then set the cross over point for each channel with the ICBM. It also allows independent volume settings for both subwoofer and LFE channels. I set the fronts at 60Hz (M60 like towers), the center at 80 Hz (Klipsch KLF C7 center channel speaker) 100 Hz for the side and back surrounds (QS8s and M2s). Another benefit of using the ICBM is that you have bass management even using multi channel direct for SACD or DVD Audio. If you put the ICBM between an SACD/DVD Audio/DVD player and your receiver, you will have bass management control for movies and music from that source. If you put the ICBM between a processor and external amps, you'll have bass management control for any source.

Seems to me that if you set your receiver/processor so it sends full frequency information to the speakers you risk overdriving the drivers, overheating the drivers, and taxing the amp section. It takes more power to put out bass than treble. If you set your speakers to small or use a bass manager like the ICBM, you relieve the amp of working hard to put out low frequency information, you also relieve your speakers of trying to do what they're not good at doing - producing low frequency output.

My .02 - give yourself an hour to try everything... trust your ears and your spouse's ears (if you're male - women's hearing is usually better than men's) choose what sounds best after that hour and rip off the knobs. Keeps you from being one of those annoying twiddlers that gets up and grabs the remote every 15 minutes during a movie and makes adjustments. This promotes healthy relationships with everyone else in the room.

Failing that... there's always pink noise and an SPL meter.

Bren R.

Bren, you make a good point. I normally go deep to get things set up and then leave them pretty much alone. The HT is a "Twiddler-free Zone". The only adjustments I expect to make on a go-forward basis are volume and taking the sub up 3-4dB for movies or back down for music.

I put all of this equipment together to enjoy, not to spend endless hours squeezing it for nano-improvements. Last night was the first time since I got the speakers (last Friday) and moved/calibrated them that I sat down & enjoyed them.

Other than a few stray trips to this forum, I did a 3 1/2 hour review of my CDs in a semi-dark room with my eyes closed sipping on some Gentleman Jack. Sublime.

Peter is a friend we're visiting in London, whom I emailing constantly this week for details on the trip ... and whose name crept in as a typo. My mistake, CHESS.

I have not used an Spl meter However I had turned off my sub just hear what the M22's could do on their own. Then turned my sub back on and readjusted its output to my liking. I feel I have achieved a better balance in sound when watching movies this way. A little more sound from left and right than before. And as others have noted WAF is much higher now than before. So it really is a subjective thing. Looks like I opened another can of worms. Almost to the extent of speaker cables. But that's a few other threads.