Adding sub to "full range"... - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 48 Old 03-26-08, 07:43 AM Thread Starter
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Re: Adding sub to "full range"...

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WmAx wrote: View Post
The only way to get ideal integration and sufficient main protection as you seem to desire, it seems, is with an external active crossover with a great deal of flexibility/adjustment that your internal AVR crossover lacks(nearly all receivers have limited crossover adjustments). You could use, or example, a Behringer DCX2496, which would allow perfect integration, as this is a very powerful DSP outboard crossover/filter processor. But unless your receiver has a way to feed out the pre-amp signal AND feed the now processed signal back into the amplifier section of the AVR - you will not be able to use this method. The only way to get this method to work would be to use an outboard amplifier for the mains, thus using the AVR only as a pre-amp for the mains. The total cost, best case scenario, to add both the procesor and the amplifier, is probably in the $500 USD range.

-Chris
I was thinking about an outboard crossover, sounds like fun, but I'm jhoping for a more elegant solution... I'm not familiar with teh 2496, but I'll look it up...
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post #12 of 48 Old 03-26-08, 07:44 AM Thread Starter
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Re: Adding sub to "full range"...

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what is the model number of your AVR?
Sony, DTB940... I think...
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post #13 of 48 Old 03-26-08, 07:57 AM Thread Starter
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Re: Adding sub to "full range"...

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Mike Cason wrote: View Post
I've played with the speaker setups in all configurations many, many times. My final optimal quality listening results for both music and movies to get the full benefit of the mains and the subs, is to set my mains to small, even though my mains are monsters, and have set my xover to 60 hz cutoff to the subs through the LFE sub outs.
One question I have is: when you had the cross set lower than 60, did you play a bit with altering the positions of the mains to avoid interference? different listening positions?

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I would definately use your LFE output to your sub(s), and set the mains to small and give it a try. That's what those LFE outputs are for. I think you will be very happy with that setup. I've seen the daisy chain of the main speaker wires from the receiver wired to the sub, then out of the sub to the mains. I've never liked that and have always had less than desirable performance this configuration. I've tried it on a couple of systems.
Sorry to get semantic, but strictly speaking, the LFE is a channel on the program media, not an output from the decoder or preamp... the decoder/preamp processes this channel (in conjunction with the other channels and the settings its given) to create a sub output... strictly speaking, the LFE is not intended to necessarily be the sub output... see this article from Dolby... http://www.dolby.com/assets/pdf/tech_library/38_LFE.pdf

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You mentioned you're desire was intended for music so I've included a chart showing the range of most musical instruments. By looking at this chart, you can see how much more musical reproduction has to be carried by the sub between 60 and 80 hz.
Yes, indeed... I've seen the chart before... I'm in agreement about preferring 60Hz to 80Hz crossover... another question... how does say a bass drum fit into this chart? How about a bass guitar?

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I hope this helps and have fun.....
It certainly does start to help... and if this isn't fun, why are we doing it?

Thanks everyone for all the info and help... I hiope this continues a while until I figure out what I want to do...
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post #14 of 48 Old 03-26-08, 08:46 AM
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Re: Adding sub to "full range"...

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I was thinking about an outboard crossover, sounds like fun, but I'm jhoping for a more elegant solution... I'm not familiar with teh 2496, but I'll look it up...
Elegant - certainly not. But it is the best solution from a functional standpoint. The unit allows for precise variable control and virtually any type/slope of crossover that you could practically want to use. It also has dynamic protection systems that you can set to limit output at specific frequencies at specific output levels. You will not be limited as to your options to find the best crossover point/type/rate. You can also use the DCX to apply room correction filters for bass in order to compensate for some room acoustic issues. You can also use the DCX to customize the roll off characteristics of your sub-woofer: this is a huge bonus because many subjective sound quality preferences(subjective bass 'tightness' is one very largely effected factor, for example) are directly related to the bass cut off point and slope of the LF system. It offers transparent operation and is very easy to use, especially if you use a laptop PC to hook up to it using the Behringer GUI software. You can do all settings from the front control panel of the DCX as well, but it takes more time to do so for many parameters. Main problem with this approach as I stated before: having to use an outboard amplifier for the main speakers due to lack of method to re-feed the processed pre-amp signal back to the internal AVR speaker amplifiers.

-Chris
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post #15 of 48 Old 03-26-08, 09:10 AM
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Re: Adding sub to "full range"...

I think I would use the 60Hz crossover point from mains to the sub and connect the sub to the sub-out on the AVR. If you crossover too close to the lower range of a speaker then the natural roll-off of the speaker combines with the crossover roll-off to make a total roll-off slope steeper than expected by AVRs. You could potentially have a dip in the systems response in the crossover region.

However, if you really want to take mains to their full range, I would set them to large and set the AVR to send the LFE to the mains. Run pre-amp mains to the sub and use the sub's built in Low pass crossover to limit it's upper extension. I've never seen a powered sub that didn't have one. You can then use a passive crossover before the mains to limit their low end to whatever frequency you want. A first order high pass filter should do it. This is basically a capacitor (or group of capacitors) in line between the receiver and the speaker and should cost about 15$ per side. I believe speaker makers already build this into their crossovers to keep you from over-driving the speaker with material that is too low. Granted that the built in ones are probably better tuned and a little more sophisticated, but the concept is the same. Regardless, it isn't as flexible as the active crossover/external amp solution, but it is a very inexpensive thing to try.

Last edited by hddummy; 03-26-08 at 09:19 AM.
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post #16 of 48 Old 03-26-08, 10:18 AM Thread Starter
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Re: Adding sub to "full range"...

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hddummy wrote: View Post
I think I would use the 60Hz crossover point from mains to the sub and connect the sub to the sub-out on the AVR. If you crossover too close to the lower range of a speaker then the natural roll-off of the speaker combines with the crossover roll-off to make a total roll-off slope steeper than expected by AVRs. You could potentially have a dip in the systems response in the crossover region.
Never thought of that... on first inspection at least...I wonder what other people have to say about that...

Don't the "guidelines" usually state to set the crossover at the rolloff point of the mains (and of course to set the crossover control on the sub to maximum)? Woudn't this then cause an issue more often than not?
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post #17 of 48 Old 03-26-08, 10:49 AM
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Re: Adding sub to "full range"...

I've just always followed that rule and I don't think any guidelines would convince me otherwise. If recommendations don't agree then I'll bite my lip about it. I'm sure the crossover slopes built into the AVR also have an influence on how close to the speaker roll-off you can crossover. That is one of the nice things about external active crossovers...you have complete control over these sort of things.
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post #18 of 48 Old 03-26-08, 11:56 AM
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Re: Adding sub to "full range"...

Why not set up your system for no sub at all during music playback? If your mains as you say can go below 40hz, it's unlikely a sub will help much depending on how loud you listen, the type of music you listen to (hip hop/rap will require a sub) and the power of your AVR. I listen to music in stereo (most of the time) with my mains set to large and my subs off. When viewing movies, I go ahead and cut in the subs (I have 2) which are crossed over at 80hz (I use the recommended THX crossover point despite the fact that my mains are easily usable to ~24hz). In most cases, IMHO your speakers will handle 90% of all music no problem, but as others have said; you should try it both ways as simply by crossing over at 60hz or 80hz will take a huge drain off of your AVRs output as well as the bass drivers of your speakers and in all likelihood make your system sound a lot more "open", "detailed" and "smoother".
Just my 2 cents worth...hope it helps!
Cheers,
Konky.

I get up...I get the paper...I read the obituaries...if I don't see my name; I go ahead and have breakfast! George Burns.
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post #19 of 48 Old 03-26-08, 01:42 PM
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Re: Adding sub to "full range"...

The thing is, and like I said before, a properly set up sub will outperform your mains. A properly set up sub will have EQ and freedom of location that you don't have with your mains. The response from a properly EQ'ed and placed sub will be smoother and have more headroom than your mains. Music or movies, there is no fundamental difference. It's all sound. Movies often put more of an emphasis on extension, where music demand more agility and precision. This is a broad generalization though. 50% of a movie soundtrack is music.*

*Non-scientific guesstimate


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post #20 of 48 Old 03-26-08, 01:52 PM
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Re: Adding sub to "full range"...

Quote:
glaufman wrote: View Post
One question I have is: when you had the cross set lower than 60, did you play a bit with altering the positions of the mains to avoid interference? different listening positions?



Sorry to get semantic, but strictly speaking, the LFE is a channel on the program media, not an output from the decoder or preamp... the decoder/preamp processes this channel (in conjunction with the other channels and the settings its given) to create a sub output... strictly speaking, the LFE is not intended to necessarily be the sub output... see this article from Dolby... http://www.dolby.com/assets/pdf/tech_library/38_LFE.pdf



Yes, indeed... I've seen the chart before... I'm in agreement about preferring 60Hz to 80Hz crossover... another question... how does say a bass drum fit into this chart? How about a bass guitar?


It certainly does start to help... and if this isn't fun, why are we doing it?

Thanks everyone for all the info and help... I hiope this continues a while until I figure out what I want to do...
Well, I don't have an arguement with the Dolby link because I'm certainly not a pro. I'm just a novice builder but have built a system that everyone who has listened to it says it's the finest sounding they have ever heard, bar none. I'm just providing you with the settings that I've found to give me the most, and best, sound I can get with my system. I usually listen to music and some concerts in two channel only because the mains are so good.

My Rotel has the sub output and that's the one I use. I am to assume that is the LFE rca jack as well. The Rotel was their top of the line unit so that may explain why my subs get the freqs I set the crossover to.

As far as bass guitar reproduction, I hear everything, even the real low bass that leaves your shirt sleevs wobbling in the air due to the long sound waves. Joe Satraini and the Blue Man Group is literally chest pounding at high levels. Kick and kettle drums are clean. I've ordered the Reckhorn B-1 to fine tune it even better and am expecting a real treat.

As far as placement, my system is so large I can't move it around so I've stacked my subs as shown in the Avatar. I did try having them in two different places, but the co-locating works fantastic. I've even broken the seal in my 5' x 6' plate glass window in the living room. I'm attaching a photo to show why I can't move it around and still maintain decent seating.

Good Luck....
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Adding sub to "full range"...-finished009.jpg  


Last edited by Mike Cason; 03-26-08 at 02:01 PM.
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