I want to run my mains as large ... (1 Viewer)

[Marcus Lewis]

Harold thanks for your very informative and helpful post ...

I'll do just as you suggest.

Too, I may still look into the Outlaw ICBM so I can experiment with the crossover setting, possibly settling

on the 80hz THX spec ...

Anyway, thanks again for sticking with me on this one ...

 

[Scott Merryfield]

Scott,

I own B&W 604S2's, and have settled on an 80Hz crossover and SMALL setting with my setup for providing the best blend between mains and subwoofer in my room. With my old receiver, a Sony 50ES with a high 100+ Hz crossover, I did run the 604's as LARGE, but the receiver allowed me to also send the main's bass to the sub as well (Sony referred to this as either MIX or BOTH, I can't remember which). I did this because my sub is located in the rear of the room and I could localize some of the higher bass frequencies with the Sony receiver's high crossover. With my new Pioneer Elite receiver set at 80Hz, I no longer can localize the subwoofer.

 

[Arron H]

Scott,

My receiver has the "both" option. Were there any drawbacks to using "both?" Based on Harold's comments, it would seem like you would lose some midbass, midrange, and highs because the mains would still be working harder set to large. However, having the mains' bass going to the mains and to a sub in the back of the room would probably offset any localization problems as you already mentioned. It sounds like a tradeoff. If the Pioneer Elite had the "both" setting, would you still use it or at least experiment with it to see if it sounded better than with all speakers set to small?

 

[Harold_C]

This is not correct. The receiver crossover settings on the "5" speakers does not affect the ".1" LFE output. The crossover is only for the selected speaker line levels.

I am looking at the block diagrams for the bass manager function in the Cirrus Logic application guide (AN163).

When you have speakers set to SMALL, they do NOT receive any LFE signal, period.

Furthermore, the bass management system combines the LFE channel and all redirected bass from the other five channels BEFORE it goes through the lo-pass filter to the subwoofer.

In a system with all SMALL speakers, the subwoofer is the only speaker that can reproduce the LFE channel and that LFE channel will pass through the low-pass filter before it is output to the subwoofer. Therefore, if you set your receiver's crossover below 80 Hz, you will be throwing away part of the LFE channel. The subwoofer won't play anything above the crossover -- not from the normal bass recorded in the main channels, not from the bass recorded in the LFE channel.

 

[Harold_C]

My receiver has the "both" option. Were there any drawbacks to using "both?"

It's considered bad design practice to have different drivers overlapping in the same frequency range.

Look at it this way:

Forget the subwoofer entirely for a minute and just think about a two-channel system with the B&W 604s.

The 604 is a three-way speaker system. The dual 7 inch bass drivers play up to 450 Hz. The 6 inch midbass driver plays from 450 to 2700 Hz. The tweeter plays from 2700 Hz on up.

Now, we know that the 6 inch midbass driver can play down to 60 Hz, because that's how it's used in the B&W 2-way speakers. So why chop off it's bass at 450 Hz? Aren't we "leaving something on the table" and "not getting the most out of the speaker"?

No. It's crossed over at 450 Hz because the woofers in the system do a better job at reproducing low bass and because the midrange driver sounds better if it's not moving back and forth as far as it would if it played bass. In other words, the reason the 604 sounds better and handles power more effortlessly in the midrange than the 2-way systems is BECAUSE the midbass driver is not reproducing the lowest bass. Additionally, if you had the midrange driver and the woofers both playing the same low bass, you would introduce a whole range of cancellation nodes.

Removing the 450 Hz high-pass filter from the midrange driver in the 604s is EXACTLY the same thing as running the receiver in the "both" mode. Nobody (with any sense) would go in and disable that crossover in the 604. For exactly the same reason, it wouldn't be sensible to run the receiver in the "both" mode (that the quality of the powered subwoofer is roughly on par with the rest of the speakers). Doing so would note only negate the benefits of the powered sub, but would also create new problems.

 

[BruceD]

Therefore, if you set your receiver's crossover below 80 Hz, you will be throwing away part of the LFE channel. The subwoofer won't play anything above the crossover -- not from the normal bass recorded in the main channels, not from the bass recorded in the LFE channel.

Actually this statement is not correct for the latest Cirrus chip used in the Outlaw 950. If you have your mains xover @60Hz, center xover @100Hz, and surrounds xover @80Hz you won't be throwing away any LFE at all.

 

[Harold_C]

Actually this statement is not correct for the latest Cirrus chip used in the Outlaw 950. If you have your mains xover @60Hz, center xover @100Hz, and surrounds xover @80Hz you won't be throwing away any LFE at all.

But, that is only because the low-pass filter would be set to 100 Hz in that configuration. I'm looking at the Cirrus bass manangement application guide dated Feb. 02. The entire output of the bass mixer (normal channels + LFE) still goes through the low-pass filter.

As a practical matter, I'm not sure that setting different high-pass filter points for the various speakers (all within less than an octave of each other) really buys you anything. People might convince themselves that it sounds "better" just like they convince themselves that one $500 speaker cable sounds "better" than another $500 speaker cable. But, I'd love to put money on a blind A-B comparison to see if anyone on earth could identify the difference between that crossover setup and just setting everything to 80 Hz.

The totally unpredictable room effects at the crossover region with five speakers and a subwoofer interacting in various ways depending on the bass content of the program would totally dwarf any predictable intention for setting the crossovers differently.

The main thing you would gain would be an additional 2-thirds octave of overlap between the front speakers and the subwoofer. In reality, you'd ideally prefer a little less overlap since the 2nd order high-pass filters presume a 6dB acoustic rolloff for optimum Linkwitz-Reilly alignment. With speakers capable of bass below 80 Hz, you already have a little too much overlap.

 

[Philip Hamm]

Wow Harold, that's a really poor bass management implementation you've described there.:frowning: The LFE should always be sent to the sub with no low pass filtering at all (except that in the sub itself). What you've described is crazy. So what happens with the LFE low pass filtering if all speakers are set to LARGE all the time?

As a practical matter, I'm not sure that setting different high-pass filter points for the various speakers (all within less than an octave of each other) really buys you anything. People might convince themselves that it sounds "better" just like they convince themselves that one $500 speaker cable sounds "better" than another $500 speaker cable. But, I'd love to put money on a blind A-B comparison to see if anyone on earth could identify the difference between that crossover setup and just setting everything to 80 Hz.

My center channel speaker sits on a RPTV. When it is crossed over at 80 Hz I get some distracting bass reactions caused by the huge empty box that's acting as a speaker stand. When I switch the crossover to 100 the effect is noticably decreased. I'm not sure if you consider 100 and 80 Hz to be in the same "octave", but my RPTV definitely counts as a "room effect".

 

[Philip Hamm]

And a little off topic, if I had the money for a set of DM604S3 speakers and I was planning on using a sub anyway, I'd take a good listen to the low end CDM speakers.

 

[Scott Merryfield]

My receiver has the "both" option. Were there any drawbacks to using "both?"

Arron,

The main drawbacks are the possibility of frequency cancellation between the mains and subwoofer, and the fact that your receiver's amps will need to work harder to produce the lower frequencies via the mains that are already going to the sub.

In my case, though, the trade offs were worth it, as I did reduce the localization of the subwoofer in the back of the room due to the Sony receiver's high crossover. Overall, the system sounded better to me with the receiver set to both and the mains to LARGE. The only way I was able to fix the problem completely was when I upgraded to a newer receiver with a lower crossover. Moving the subwoofer to the front of the room was not an option, since there was no room there to place the sub.

My Pioneer Elite does have a BOTH mode (it's called something different, though) that I tried as I was experimenting with different speaker settings. In the end, I thought setting the mains to SMALL with a crossover of 80Hz worked best in my room. The receiver also has crossovers of 50Hz and 120Hz, but the setting is applied to all channels (i.e. I cannot set a different crossover for the mains, center and surrounds). Since my center and surrounds are not designed to handle frequencies that low, I ruled out the 50Hz crossover right away.

Since room environments can vary greatly in different home theaters, the only way to find out for sure what works best for your particular room is to experiment with different settings to see which sounds best. Just remember to recalibrate your speaker and subwoofer levels when you make changes.

 

[Harold_C]

So what happens with the LFE low pass filtering if all speakers are set to LARGE all the time?

That depends. If all five speakers are set to LARGE and there is no subwoofer, the LFE channel is sent directly to all of the speakers with no filtering. That's "Dolby Configuration 0" and the LFE channel is boosted 10 dB relative to each other channel.

If there is a subwoofer, the "LFE_ONLY_SUB_ENABLE" register is set to "ON" and the LFE is output directly to the subwoofer with no filtering. This does not appear to be one of Dolby's required configurations, although it is surely implemented by virtually all receivers.

In both cases, there is no high-pass and no low-pass filtering anywhere in the system.

Mixed LARGE and SMALL systems get quite complicated. There are even "alternative" Dolby configurations that can be implemented for exactly the same speaker combinations -- for example, in a LARGE FRONT, SMALL CENTER/SURROUND, and SUBWOOFER system, one Dolby Configuration 2 mixes a little of the redirected bass and LFE into the LARGE speakers (this is probably PLUS mode). Dolby Alternative Configuration 2 leaves the front LARGE speakers alone to do their own thing and the redirected bass and LFE is played entirely by the subwoofer. Either of these could play heck with an SPL meter calibration -- which is why I think calibration should always be done with either ALL SMALL or ALL LARGE.

 

[Duke]

That's why the LFE is boosted 10 dB in a 5.1 channel system. But, if you have fewer than 5 speakers or different combinations of large and small, then that 10 dB number changes.

I don't know where you got that from, but you are total off base !

The LFE of DD/DTS is recorded at -10, thus requiring a +10 LFE boost, excet for DTS CD's that are recored @ zero cut/boost.

 

[Luke M]

The LFE channel has a bandwidth of 120Hz, so any processor that uses the "standard" bass management described (correctly, as far as I know) by Harold, with a crossover less than 120Hz, is indeed throwing away part of the LFE channel. Not what I would call good bass management. (Of course, the LFE channel shouldn't exist in the first place, but that's another story).

Presumably those receivers that permit really low crossovers (e.g. Sony 5ES) are forced to implement correct bass management.

Alternatively, you can set subwoofer to "no", mains to "large", and use the external crossover of your choice.

 

[Harold_C]

I don't know where you got that from, but you are total off base ! The LFE of DD/DTS is recorded at -10, thus requiring a +10 LFE boost, excet for DTS CD's that are recored @ zero cut/boost.

The information comes from Dolby's 5.1 Channel Production Guidelines:
link to PDF
The LFE channel uses the full bandwidth of the digital data stream just like any other channel. Full-scale digital amplitude (0 dbDF) is the same for the LFE channel and for the other 5 channels. That's why any of the main channels can produce a 105 dB output at Dolby reference levels while the LFE channel (after the 10 dB boost on playback) is capable of 115 dB maximum ouput. The 10 dB boost is not there to get the LFE channel up to the level of a single main channel; it is to get the LFE channel up to a level 10dB HIGHER than any single main channel.
What actually happens is that the mixing engineer's playback system is calibrated to duplicate the 10dB boost that consumers will hear. He then mixes the 5.1 channel recording so that the LFE channel he hears will balance properly with all five channels operating in unison.

 

[Harold_C]

Presumably those receivers that permit really low crossovers (e.g. Sony 5ES) are forced to implement correct bass management.

Seems to me that "correct" bass management in a Dolby Digital decoder is whatever Dolby says it should be. After all, it is their recording/playback format. All of us might have our own ideas about how it "should" be done, but the main purpose of Dolby Digital is to have a fixed standard so that playback matches what the recording engineer hears. Dolby Digital mixing studios are configured with the assumption that what they are recording will be played on properly configured Dolby Digital decoders, including what Dolby defines as "proper" bass management.

Although they use a somewhat different compression and encoding scheme, DTS essentially matches Dolby step for step on bass management. With the exception of DTS music discs, "proper" bass management for Dolby will also be proper bass management for DTS. It all basically goes back to the gospel according to THX.

 

[Marcus Lewis]

Harold I just wanted to say thank you!

I got home, made some adjustments as you recommended, all of a sudden everything has tightened up and is audibly much improved.

You were right on, my problem was too much bass ... way too much, lol

I'm still waiting on my RatShack meter, but just reducing the gain on the amp alone has transformed the system for music playback ...

Thanks again my friend.

 

[Scott Merryfield]

It's not uncommon for people to set their subwoofer volumes too high if they do not have calibration tools, Marcus. My next door neighbor did the same thing with his system. He and his wife were amazed at the improvement after I calibrated the system with Avia and a Rat Shack SPL meter. I, on the other hand, was amazed that they could stand listening to the system before I calibrated everything -- it was horrible.

 

[Harold_C]

No problem. Your note that you had the subwoofer setting at full minimum was the dead giveaway. I don't know why I didn't think of that sooner -- it just took a while for me to come to full grips with your dual sub 1000 watt rig and the implications of that much gain on balancing the system.

You are one guy who is not going to have any trouble at all getting full impact from the LFE channel! You've got the opposite problem -- how to tame that monster.

 

[Harold_C]

I, on the other hand, was amazed that they could stand listening to the system before I calibrated everything -- it was horrible.

I don't know any subwoofer owner who hasn't made that mistake. It's only natural. You set up your fancy new subwoofer and, by god, you expect to hear it booming away 24/7.

The problem is that we forget that deep bass is relatively intermittent in most recordings, so to "hear the subwoofer" all the time, the bass levels have to be through the roof. I had my sub set about 5 dB too loud at first and the darn thing kept scaring me on movie soundtracks. But, is sounded like a special effect rather than something that blended with the rest of the soundstage. Bass shouldn't draw attention to itself THAT much!

I've gotten to the point where I listen to the lower registers of a male voice. Even though that is way above the crossover point, if it sounds at all "heavy", it's usually a dead giveaway that the sub is too loud.

 

[BruceD]

Harold,

As a practical matter, I'm not sure that setting different high-pass filter points for the various speakers (all within less than an octave of each other) really buys you anything. People might convince themselves that it sounds "better" just like they convince themselves that one $500 speaker cable sounds "better" than another $500 speaker cable. But, I'd love to put money on a blind A-B comparison to see if anyone on earth could identify the difference between that crossover setup and just setting everything to 80 Hz.

I can't speak for your ears Harold, but in my tests in my listening room with active electronic crossovers, my own ears, and MLS based impulse response graphs (with a calibrated mic), I can certainly tell when I get better low-pass to high-pass xover integration at different xover frequencies. Yes, there are differences between a 60Hz and 80Hz high-pass with speakers that have a -3dB to 30Hz. Now some of this can also be due to specific room nodes, but the whole point of adjustable xovers is optimization for a specific environment.

Another useful option for adjustable xovers is setting the center channel to a higher xover (like 100-120Hz) than the mains, so that the center channel's output can be optimized for the speaker position, like when it's on a shelf in a wall unit above a TV.