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post #61 of 64
3/1/12 at 12:50am
Quote:
Originally Posted by Scottthehat View Post

I don't know the exact db just know that's how i use mine and it does make a noticeable difference.

What do you mean that how you use yours? The sub should be adjusted to the same output level whether you use a Y adapter or not. But it doesn't provide any advantage to use one. It doesn't increase the sub's available headroom. And if you are operating your sub at its maximum volume level (doubtful) already, then you have some problems that a Y adapter definitely won't help you with.
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post #62 of 64
3/1/12 at 1:04am
Quote:
Originally Posted by kawie01 View Post

If I have towers for my fronts & backs, should I change the Audyssey from small to large/full?

Only if your main speakers are larger than you are and wall mounted or a healthy distance off the wall (4-5' is a nice start; otherwise the SBIR null is significant) or your sub-woofer sucks and you can't stand the sound of it.

When speaker companies (honestly) claim response to a given frequency they don't state at what SPL and in many cases you won't don't get usable output (or even audible) levels at those frequencies.

When crossing to a sub-woofer things get more complicated because the output from a port which unloads the active driver isn't usable since it's 180 degrees out of phase with the rest of the spectrum and will cause sub-woofer integration problems.

1. Reference level home theater takes up to 105dB peaks at the seats which can translate into 108-110dB+ at the speakers.

2. Output at the maximum linear excursion for various representative drivers at 3 feet is as follows at 80 and 20Hz. Many lower quality drivers have less excursion and lower output (one noted speaker designer commented that an $8000 MSRP allowed for an $80 mid-range driver). Subtract 3-5dB for living room dimensions and more for a larger space.

You can add 6dB for a floor mounted woofer (as in a 3-way) and 6dB if there are a pair of bass drivers. For a 2-way the numbers are what they are although in all cases you can add 6dB at the cross-over point when using an even order sub-woofer cross-over.

Size Driver Sd (cm^2) x xmax (mm) 80Hz 20Hz
5 1/4" Peerless 830873 88 x 3.5 88dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 94dB 70dB
7" Seas W18EX001 126 x 5 95dB 71dB
8.5" Seas W22EX001 220 x 5 99dB 75dB
10" Peerless 830452 352 x 12.5 111dB 87dB

As you can see consumer 2-way speakers don't have enough for an 80Hz cross-over and floor standers with just a couple of 10" sub-woofers don't have enough for full-range use.
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post #63 of 64
3/1/12 at 1:38am
Quote:
Originally Posted by sivadselim View Post

What do you mean that how you use yours? The sub should be adjusted to the same output level whether you use a Y adapter or not. But it doesn't provide any advantage to use one. It doesn't increase the sub's available headroom. And if you are operating your sub at its maximum volume level (doubtful) already, then you have some problems that a Y adapter definitely won't help you with.

I use a y adaptor that's what i mean and as for reference volume i prefer more bass at lower volumes so kind of make reference volume unless as i never have it at that, -15 to 20 is mental enough for my 20x12 room.
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post #64 of 64
3/1/12 at 7:43am
Quote:
Originally Posted by sivadselim View Post

OK, I'll try.

We're talking about a line level signal, here, which means we're dealing with voltage. When you split a line level signal into two inputs, as long as the input impedances are relatively high compared to the output impedance, there shouldn't be much of a (if any) voltage drop in the system. The sub's inputs do have a high impedance and the AVR's sub pre-out does have a relatively low impedance. As I said, the Y adapter doesn't just simply split the voltage in half. It doesn't work that way. Potentially, the same voltage signal can reach each of the sub's inputs as would reach a single input were only one input used. And since the sub sums the inputs, the result is a higher input signal to the sub's amp than would be there were only one input used, which results in an increase in output.

The same sort of thing happens when a Y adapter is used to split a line level signal into two separate subs, or into a sub and an amp, or into 2 separate amps. As long as the signal is feeding inputs with relatively high impedances, there is no appreciable signal loss. It is certainly not split in half. Ask anyone who uses multiple Y adapters to connect multiple subs if they think there is significant signal loss across the Y adapters.

The exact increase in output that results from using a Y adapter and both of a sub's inputs has been measured and reported here in these forums many, many times. It's real. It's just not a useful and/or usable increase.


Now, I may have boogered something up in that explanation. I'm not an EE. Maybe someone else can explain it more succinctly or in more understandable or simpler terms than that. You can also read, yourself, about how line level signals behave when they're split into high impedance inputs.

But that is about as much time as I want to waste on this.

OK thanks! But you're right. On to other things!
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