Two subs makes my system sing. I recommend it for everyone!!! (1 Viewer)

[Legairre]

Oops, sorry Vin. I guess I was on a roll typing away. I didn't know you already answer his question.

Jason,

I almost fogot. You get to the sub calibration from AVIA'a main audio calibration menu(chapter 7 I think. I'm at work and can't check for sure). It's called "subwoofer calibration".

 

[Jason Wolters]

OK. I am familiar with that. I just thought someone said there was a seperate calibration for high level. I didn't think there was. thanks.

 

[Ryan Schnacke]

80db) is non directional.

First, I assume that you meant to say bass 80Hz.

As the car audio guy drives by on the street he's not only making those thud....thud....thud noises but also engine noises, tire friction noises, air friction noises, etc. So even if his thuds were non-directional, the other noises are not. And your brain is smart enough to automatically associate those directional car noises with the bass noises. The car's position is given away by ALL the noises it makes.

Now lets talk about why low bass might be non-directional. Sound travels at, what, 700mi/hr or so? I'll use that number since I don't know exactly. So that's 1026.7ft/second. Now lets say that your home theater room is 12 feet long. So it takes 11.7ms for the sound to travel 12ft. 11.7ms is also the time it takes for one complete cycle of 85.6Hz sound. If you have a lower frequency sound then it takes even longer for a complete cycle and the sound travels farther than 12ft before it completes that cycle. So any sound with a frequency lower than 85Hz has very likely bounced off a wall or two before you hear a complete cycle.

I believe this is why low bass is non-directional when you are enclosed in a small room (Can someone verify or disprove this?). By the time you've heard a full cycle, the bass has bounced off walls and is coming at you from several directions. So you don't know where its really coming from.

This would mean that with a bigger room the bass must be lower before it is non-directional. But that car that drove by with the sound system thumping wasn't in an enclosed room. It was outside in the open. So the bass would have to be near 0Hz before it was non-directional. Not that you could actually hear anything that low.

 

[Vin]

That answers my question. So if you set to no sub and use low level where does the LFE go? Back to the mains or is there no LFE in this case?

Using the line level output (sub pre-out) from your receiver and setting the sub to NO will send the LFE to the mains if set to LARGE.....if mains are set to SMALL with a sub setting of OFF, LFE will be lost, as will deep bass for any speakers set to small.

Vin

 

[Vin]

Oops, sorry Vin. I guess I was on a roll typing away. I didn't know you already answer his question.

No problem buddy, seems we got some good teamwork going here.....
Vin

 

[Dustin B]

I have a question. Don't most sub plate amps have a variable low pass filter, but a fixed high pass some where around 100hz? I never understood how this could work. If the high pass is fixed at some frequency around 100hz (I've seen 90hz and 125hz) and you set the low pass at 60-80hz aren't you leaving quite a hole in the frequency response?

 

[Dustin B]

I just did a little more looking. The cheaper plate amps from Audio Express and Adire all have the high pass fixed at 125hz. The much more expensive one at Audio Express has it fixed at 90hz. The much more expensive HS series at Adire have the high and low pass filters independantly variable (ie the amp appears to have 2 dials, one for the low pass filter and one for the high pass filter).

 

[Lewis Besze]

I agree with Tom and Wayne here.
They already explained why this isn't a very "good" idea,but there is also something else here as well.
Do any of you who using a back sub with the surrounds via speaker level,do you still high pass the surrounds with either the subs highpass filter[not so common on commercial subs,and usually with a single xo point which usually too high],or with an external crossover box?
If not do you think that those very "realistic" bass moments will reach the surround speaker's woofer as well?
What do you think will happen?
Just because a speaker doesn't rated below say 70hz,it will still try to reproduce frequencies below that point as well,except it most likely will distort badly!
Sounds like a quiet a few things to consider just to move that sub back there!

 

[Legairre]

Lewis,

My rear subs have a high pass. I set my crossover to about 65. My four surround speakers are only rated at 100 watts each and only have 4" woofers(my power amp is a Rotel 1095 200x5). With woofers that small it wouldn't take too much low bass to distort or even make them Pop. I've had my system cranked during movies and haven't noticed any distortion at all during action scenes when the rear subs are really used.

I have tried setting my surround speakers to LARGE and running them WITHOUT the subs connected and they do distort and pop like crazy during action scenes with low bass(yep they can't handle bass that low). With the subs connected they no longer distort or pop, so it would lead me to beleive that the low bass is going to the subs and not to the surrounds.

 

[BruceD]

Legairre,

So you're sure you don't have any holes in the frequency coverage between your surrounds and their rear subs crossed over at 65Hz?

I find it hard to believe the 4" woofers on the surrounds can be a good match for a 65Hz crossover to the rear subs.

If your surrounds are what you listed on your web-site

4 JBL HLS410 (surrounds) with a Frequency Response of 75 - 20kHz, then you have a definite hole in your rear soundstage, probably from 65-80+ Hz.

Proper crossover frequencies make a big difference. My mains are crossed over at 60Hz to my sub and my mains have a response down to 32Hz.

 

[Legairre]

Bruce,
I can't complain it sounds good over here. I couldn't be happier. What can I say the crossover my rear sub is set at works in my room. Yours works in yours, mine works in mine. At least we're both happy.