Surround Subwoofers - Page 2

Yeah, I actually am curious as to whether it will work, and I'm glad someone else is spending the money and time on it. It's like our own little acoustic petri dish.

Here is an interesting experiment for you. Blindfold yourself and have a friend bang two rocks together. You will be able to point out where he is. Cover both your ears and try it - much less obvious where the sound originates. We get a lot of the localization from our ears and the ridges in them that reflect sound to help us localize them. You can localize sound with only one ear.

As far as having multiple subs, I am dealing less with theory and more with actual experience here as my old system I had for many years was true full range on every channel - prodigious bass capabilities on all 7 channels - I didn't even use a sub but just fed the LFE back into my mains. You could tell where the bass was coming from although it was more subtle. If oyu have a lot of high frequency stuff coming at the same time, as is usual in film, then you localize it together in the same place as the high frequency stuff.

A good yet very short overview of hearing and how it works for localization is here:
http://www.physorg.com/news119100877.html

I have done experiments with my audio system in the past and some people look at them as experiments and try to increase their understanding (as do I) when looking at the results. Others will often just dismiss the results if they do not fall in line with their preconceived notions based on hypothese that may not be true.

Depends on where your crossovers are for your subs. AFAIK,there really is no scientific debate about localization of deeper bass notes (the typical 80 Hz crossover works for most folks, but it varies somewhat byindividual). And my experimental/experiential "research" is entirely consistent. When I first got a sub for my car, the crossover was too high, and it sounded like the bass player and part of the drummer were in my trunk. when I switched to a 70 Hz crossover, the whole bass player sounded like he or she was in front - - maybe right or left, but not coming from behind me. Although the deeper part of the notes actually came from behind me, it did not sound that way anymore. Same thing with my current HT setup. Sub is slightly left of center, and bass players on the far right sound cleanly and clearly on the far right.

Because bass notes from real world instruments include overtones that reach well into the localizable area. When I cross over my sub at 60 or 80 Hz, it does nto send every bass note with the fundamental tone 40 Hz (about an E) to the sub. It sends the part of the sound of that note below say 100 or 120 Hz (accounting for rolloff and assuming an 80 Hz crossover) to the sub. The rest stays in whatever main speakers it started in. Of course one can localize a bass instrument or sound when the localizable frequencies are in a specific location.

But if you find yourself turning to look at your subwoofer when the bassist goes low, or on each kick drum beat, your crossover is too high. If you don't, that tends to prove that the lower part of the bass is not localizable.

I would suggest that, technically, if deeper sounds from the surround speakers (assuming they go to a sub now) don't sound disjointed or jump to the location of the sub, you will not experience improved localization with subs on each channel. But if you're crossing over failry high, or even if you just want to do it for fun, it's not likely to hurt anything to add subs. Although since most program material puts the deeper tones across the front and in the LFE, some would argue you're not getting the best use of the subsif you feed them only the individual surround channel. Again, though, your system, and you get to make yourself happy.

If you have preouts on all channels:

-Set all satellites to Large
-Route an RCA from all channels to the individual subs
-Maintain a dedicated LFE channel, off the sub out.

Sound like a plan?

What if his satellites can't handle playing low bass?

Do you know what the frequency of the fire cracker is? I would bet its higher then 80Hz.

There is no reason to run surround subs you can pass all content through the LFE and its none-localized below 80Hz or whatever your room dictates.

There has been many discussions over running larger surrounds and that discussion focuses on the content in the surround channel below 80Hz...some have argued that not everything is sent to the LFE channel so running larger surrounds has a bettter impact then small surrounds/LFE.

FWIW, I ran a test with my SC-8 subs on my surround channels. I didnt find it better then having them as part of my main LFE. My overall room bass response was worse when running them through my surround channels. My main subs are twin 15" DIY ported subs but the sc-8s are great for fixing my 40Hz null.

THen obviously they need to be XOed much higher.

Having XOs way past 80Hz has nothing to do with localization. THey allow it because some speakers just suck and do not play low enough. People can place subs near the mains and run the mains just down to 150Hz without an issue.

Im actually designing some 2-ways with high end mid/tweeter that only runs to 200Hz. I will then build a bass bin that runs from 25Hz to 200Hz....I will run them with an AVR XO at 200Hz. Its just another project.

You can still have issues, since the "subs near the mains" are playing a summed mono signal, not just the bass information from the nearby main channel.

So if you have a male voice in the left channel and you set your AVR XO at 200Hz, then part of that voice will come from the bass bin near your left speaker and the bass bin near your right speaker, thereby making localization less directional.

I agree completely. This isnt for my HT, its a small project for my office with left over drivers and I do not want to add any extra devices for a 3-way so its a 2-way and just bass management. The speakers are less then 3 feet apart. Im not concerned about any of the known issues (Im definitely aware of them).

The only way to route a full-range surround channel signal to a sub (or subs) that might be connected to a surround channel (or channels), either via the AVR's pre-outs or via a speaker-level connection, is going to be to set the surround channels to LARGE. There is no other way to set up a dedicated surround channel sub. Yes, that the satellites might not be very capable down low can be an issue especially if high levels of output are desired and/or if the satellites do not reach down to the sub's high-end capability. With a surround channel sub that is connected via a speaker-level connection, the corresponding satellite might be able to be high-passed off of the sub's speaker-level outputs (provided it has them and they are high-passed). This can help to remove those frequencies below the high-pass point but if the satellites do not reach down to the sub's high-end capability you will still have a problem with a frequency hole between the satellite's low-end capability and the sub's high-end capability. With a surround channel subwoofer connected via the AVR's surround channel pre-out, there are a few ways to high-pass the satellite externally.

The 'original' CSW Ensemble ("2+2") models managed this in a clever manner. The [both passive] satellite and woofer modules for each channel were connected in parallel and contained complementary high-pass and low-pass filters respectively. While these units were designed as a system, it would also be possible to fabricate a device with a similar function, but I suspect only a true believer might go to the trouble...!

I will like to mention that using the "pre outs" to drive the subs is what i have done in the past. IN my situation i have run my 2 subs off of the main front left and right pre outs and it worked very well. For some reason my reciever does not cross over the "pre outs" like i thought it should so in my case, and maybe others you can run a sub off of any channel of the "pre outs" without running the speaker off that amped channel full range. For music i liked it better with my subs running off the left and right "pre outs" and when i add more subs in the future i may do this again with 2 subs as left and right and the other 2 running off the lfe channels.
Other recievers may cross over the "pre outs" to what ever the corresponding amplified speaker out is crossed at though so i would suggest testing first.

Are you certain that your AVR behaves this way? I do not know of any that do not apply the same settings that would be applied to the amplifier channels to the corresponding pre-outs. This includes bass, time, and level management. What is your AVR?

The high-pass slope on most AVRs is only 12dB/octave so you will still get a fair amount of output below the crossover setting from a sub connected to a SMALL channel that is being crossed at 80Hz. 40Hz output will only be down 12dB. With the ability to adjust the sub's own low-pass and master volume, knowing exactly what might be happening can be tricky. Measuring the sub's output over a range of tones above and below the crossover setting is only marginally useful (at best) if the room is selectively reinforcing frequencies below the crossover setting and/or canceling frequencies above the crossover setting.

My understanding is that if you don't attach any sub to the Pre-Out(SUB) terminal, most AVRs will force the Front L/R Main channels to be LARGE+LFE.

He's talking about his front channel L/R pre-outs, not his subwoofer pre-out.

Until you run Audyssey (or other auto-cal program) or configure the AVR manually as such in its setup menus, an AVR doesn't automatically know what is (or isn't) attached to its sub pre-out. Once an AVR is configured either via Audyssey (or other auto-cal) or manually as not having a sub attached to its sub pre-out, yes, of course the front channels are defaulted to LARGE and the LFE channel is rerouted there.

when i changed the sub setting to "no sub" it then changed the front to large but i left it thinking there was a sub and the front's were indeed still crossed at 80 hz. The subs acted almost exactly as they did when ran of the LFE signal so im 99% sure the "pre outs" where not crossed. I though that all the proccesing would be done to the " pre outs" as well but with my reciever this is not the case. It could be that my reciever is an older less expensive model but i was surprised at this discovery as well.

Well, assessing exactly what is happening by ear is difficult. Even with measurements it is difficult.

Yeah i used REW to reset up my sub levals and tune in room response. I am pretty confident if my subs where high passed at 80 hz even only at 12db per oct that i would have seen some differences. Maybe my AVR is an odd ball?

I have attached subs directly to the AVR Main-L/R-Pre-Out RCA connectors and just allowed the sub's internal LPF to delete the unneeded content (no F-mods or receiver-as-LPF-Pre-Amp required.)

Note that some AVRs specifically warn against using the Main-L/R-Pre-Out RCA connectors and the corresponding on board power amps simultaneously (for unspecified reasons.)

I thought you specifically wanted surround channel subwoofers?



You don't need F-mods in front of the subs. Don't the subs already have onboard variable low-pass filters (sometimes incorrectly called crossovers)?



No, that won't do much of anything.



Yes. I don't think you really know what it is that you want or how to do it. Sorry. Just being honest.

Looks like he's switched to stereo sub woofers . . . still problematic, of course.

Not sure what he wants. He claimed earlier to be happy with the front channel bass he gets from his speakers.



Well, not really, as long as you know what and why you're doing whatever it is you are doing.

With the sub crossover it may be only 12db per octave. So if you dial it to 80hz lowpass and run a 120 hz tone it will still be audible just not as much. If you use 80hz and its a 12db slope you will have 12db less output at 160hz. So lets say your putting out 100 db at 80 it would be 88 db at 160hz. I believe 160hz is an octave higher then 80 if i remember right. Most subs use a 18db or 24db slope though so they would have a bit less output at 160hz. Make sense?
Let me know what your plan is i may be able to help with how to make it work for ya.
The 2nd amp may be able to get used how you want but i need a bit more info for the whole overall picture of what you want in the end.

Do your subs not have their own variable low-pass filters (often incorrectly called a crossover knob)? If so, just use them. That's what they are there for. No need for any filtering upstream of the subs if they have their own variable low-pass filter.

A receiver's bass and treble controls are not high and low pass filters. The bass and treble controls usually simply adjust a single frequency up or down 10dB (or so). So, for example the bass control may adjust 100Hz +/-10dB.