LFE info goes to main speakers if set for no sub?? (1 Viewer)

[Matt Tucker]

When I moved recently, I set up the AV system with a electronic crossover I made. I prefer the sound of my crossover (especially for music) to the built in crossover of my Marantz AV-550. The Marantz has the x-over frequency set higher (100HZ) and possibly uses a less steep slope. My homebuilt x-over is 24db/octave at 85HZ.
Music sounds great, but I keep thinking that the movies are not hitting me with bass as hard as they use to. I was using the LFE channel with all speakers set for "small" before I moved.
I now have all non-main speakers set to small and have the main speakers set to large. The Maraantz manual says that it routes all bass from the small speakers to the main speakers (if set to large)if the subwoofer option is turned off.
I was thinking that maybe I am missing some bass because I am not using the LFE channel. Perhaps this is all in my head because a Dolby information page http://www.dolby.com/tech/L.mn.0002.5.1Guide.s.pdf says "If no subwoofer is present, the bass (including the LFE channel, if it exists) is redirected to the speakers best able to produce it, usuall the main stereo pair" I used 20-60HZ sine waves to listen for any dips in response for the current subwoofer location and like I said, music bass sounds great.
Is it in my head, or is it possible the LFE channel is not getting routed to the main speakers?
Thanks,
Matt

 

[Steve_Ma]

With your setup, I am virtually positive that the LFE is (or should be) getting redirected to the mains (as well as the material below the x-over for channels set to small).

--Steve

 

[Brian Fellmeth]

Two possibilities. Since you moved when you made this change, its possible that your old place provided more room gain and that your new room is swallowing up some of the "punch" you used to have. The other thing to look at depends if your current setup provides a high pass filtered signal to your mains. With the old setup, the sub got everything below the receiver's crossover plus the LFE channel exclusively. With your current setup, if your crossover is not being used to high pass the mains, then both the LFE and other deep bass are being played by both the sub and the mains. So, calibration tones (if you use them) will include a contribution from the mains leaving the sub relatively cold. Further, with deep bass comming from 3 points, deep cancillations at some frequencies are possible, and further furthermore, your main performance at midrange will be degraded by your mains (and their amps) struggeling to put out energy

 

[SidH]

I was about to post something about this very subject. An audio dealer told me that when you send the LFE to the mains, most receivers/processors attenuate the signal because full-range speakers are not designed to accommodate fullblown LFE. I was very skeptical since I have never heard of this practice anywhere.

Have you tried reverting to your previous setup (using the Marantz crossover and a small speaker setting for the mains) to see if it makes a difference?

Sid

 

[Matt Tucker]

Thanks for the input. My active crossover is both high and low pass. I should have clarified that the x-over sends >85HZ to my main speakers (6.5" with 1" tweeter) and

 

[Harold_C]

I don't really understand the urge to circumvent Dolby's digital crossovers and bass management system. By not using the Dolby processor's bass management features as intended, you are making things needlessly complicated.

For example, while the setup you describe should work, you have no way to calibrate the system using the built in pink noise tones or an Avia disc because you have given up the ability to easily isolate the subwoofer from the other five channels.

Make life easy: Hook up the subs to the processor's sub output. Set all of your speakers to SMALL. Use the receiver's crossover. Their isn't going to be a lick of difference between an 85 Hz crossover and a 100 Hz crossover. Might as well do it in the digital domain and simplify things.

 

[Matt Tucker]

I did go back to using the built-in bass management of the pre-amp/decoder. I agree that there is not much difference between 85HZ and 100HZ of same order crossovers, but between 12db/octave and 24db/octave slopes the difference is apple vs. orange. From the sound of the Marantz filter I would say it is at least 3rd order if not 4th order and there is not too much audible difference. Maybe there is a specified slope for all D. Digital decoders? I was able to put the subs in the corner across from where I sit. I was going to put one in each corner opposite the sitting position, but there was a horrible null at 50 and 60HZ in the corner by the walk-in closet. I did the old put the sub where your head is during listening and walk around the room trick. When I would approach that corner (especially near the floor) the bass response rolled off a bunch.

Now I am happy with the AV room, I can finish unpacking everything else.

Thanks everyone for the input,

Matt

 

[Harold_C]

From the sound of the Marantz filter I would say it is at least 3rd order if not 4th order and there is not too much audible difference. Maybe there is a specified slope for all D. Digital decoders?

Pretty much standard. Generally Dolby Digital processors follow THX's crossover characteristics: 4th order Low-pass and 2nd order (electrical) high-pass. The digital crossovers are all built into the Dolby Digital chipsets with default values. A manufacturer could change them using chipset registers if they felt like it, but there's not much to be gained from that.

 

[SidH]

Matt,

I infer from your last post that going back to your old setup resulted in more punchy LFE, is that so?

Sid

 

[BruceD]

To get the highest quality sound from my speakers, sub and room for both music and HT, I've found using an external active electronic xover @60Hz with symmetrical L-R -24dB slopes to be superior to my prepro manufacturer's digital xover and sub-out setup.

I intentionally don't use the 100Hz xover and sub-out of my prepro because I want my mains crossed at a lower frequency to the sub i.e. 60Hz, which is just about an octave above my mains -3dB of 31Hz (Dynaudio Contour 2.8 tower).

I have measured these setups with an MLS-based RTA system to confirm that what I hear is in fact supported by the facts.

So Matt, you can get better sound from your Marantz by using an external electronic xover, but it does depend on your main speaker's -3dB rolloff characteristics, main speaker placement, sub placement, xover frequency selected, and calibration.

An additional benefit is the use of the sub(s) in 2-channel.

By the way, when I didn't have the xover connected to my mains, the mains would rattle the bass drivers and PR when all the re-directed and LFE bass was routed to the mains.

 

[Matt Tucker]

Location, Location, Location. The bass is more punchy now, but when I went back to using the built-in crossover I also moved the subs to a corner opposite the sitting position. Too many variables to know if the change to the built-in crossover helped or just the sub location. I do have a feeling the sub position in our apartment gave a lot of gain. That was good, but I never could turn it up. Now in the house I am ready to watch movies the way they should be watched (HEARD!).

That is good to know about the 4th order slope being standard with DD systems.

Bruce, I always have liked a nice steep low pass filter for subs. I would eventually like to try changing my crossover cutoff fequency down near 60HZ. Right now I can't because my main speakers have an f3 of around 80HZ. I know that is high, but at the time I built them I knew I would be using a crossover at 85HZ or 100HZ. When time and money become more available, I may try building another pair of speakers with more bass extension or maybe I will actually buy a pair. I have always liked Paradigm and Dunlavy speakers. The Paradigm are more my price range and size range. I am getting off subject.

Bottom line... I am happy with my setup now and I will stop playing with it and go watch some movies!

Thanks everyone,

Matt