Understanding input impedance...

[felipe]

I've been wondering why when I ran my auto-cal on my setup it always set the SW level to +10(max)...Even if I set the gain on my sub to near max. I even tried moving the sub to different locations...same result. Eventually I placed my sub in its current location and adjusted the settings on my sub and AVR (after I ran auto-cal) to blend it in with my system.
I looked up the AVR sub output specs (2V/1kilohm) and looked my subs input impedance specs (47kohms unbalanced).
Could the fact that the subs input impedance is much higher than the AVR sub output impedance have anything to do with it?
Did some research, and it is stated that it is ideal to have a low output impedance and a higher input impedance. But, is there such a thing as the input impedance being "too high" in this instance?
Help me understand...please

I currently have the SW level set to +6 and my gain on the sub set at around 10 o'clock. TIA guys.

 

[Irvrobinson]

The impedance ratings do not indicate any problem at all. I see two possibilities (beyond a defective sub), you have an AVR sub output level / sub input sensitivity mismatch (unlikely), or the sub has too little output for your room.

 

[TLS Guy]

I've been wondering why when I ran my auto-cal on my setup it always set the SW level to +10(max)...Even if I set the gain on my sub to near max. I even tried moving the sub to different locations...same result. Eventually I placed my sub in its current location and adjusted the settings on my sub and AVR (after I ran auto-cal) to blend it in with my system.
I looked up the AVR sub output specs (2V/1kilohm) and looked my subs input impedance specs (47kohms unbalanced).
Could the fact that the subs input impedance is much higher than the AVR sub output impedance have anything to do with it?
Did some research, and it is stated that it is ideal to have a low output impedance and a higher input impedance. But, is there such a thing as the input impedance being "too high" in this instance?
Help me understand...please

I currently have the SW level set to +6 and my gain on the sub set at around 10 o'clock. TIA guys.

That input match sounds optimal. I suspect your sub is not up to the job.

 

[Irvrobinson]

I currently have the SW level set to +6 and my gain on the sub set at around 10 o'clock.

BTW, what does this mean? I'm unfamiliar with AVRs (I don't use them, and I don't use subs in my HT system.) Have you tried setting the sub gain at maximum, or increasing the SW level?

 

[markw]

Generally, the output impedance of a device has a much lower impedance than the impedance of the input stage of the next item in the chain. this is normal and good.

 

[felipe]

BTW, what does this mean? I'm unfamiliar with AVRs (I don't use them, and I don't use subs in my HT system.) Have you tried setting the sub gain at maximum, or increasing the SW level?

On my particular AVR, the SW level goes from -10 to +10. When I run the calibration, it sets the SW level at +10..even if I set the sub gain near or at maximum. It's overbearing if I leave it at +10 and max sub gain, so that's why I adjusted both settings to level match with everything else.
As a general rule/guideline, when setting up a sub for HT with an AVR, set the sub gain at the 12 o'clock position initially. As for the SW level, they say to keep it between 0 to +3. Like I said, this is just a general rule/guideline.

 

[felipe]

I just thought of something. My AVR has two sub outputs(non-discrete), and I have a y adapter (2 male to 1 female). What if I used the y adapter to connect both sub outs to the sub? Would that boost the signal?

 

[Irvrobinson]

On my particular AVR, the SW level goes from -10 to +10. When I run the calibration, it sets the SW level at +10..even if I set the sub gain near or at maximum. It's overbearing if I leave it at +10 and max sub gain, so that's why I adjusted both settings to level match with everything else.
As a general rule/guideline, when setting up a sub for HT with an AVR, set the sub gain at the 12 o'clock position initially. As for the SW level, they say to keep it between 0 to +3. Like I said, this is just a general rule/guideline.

If it's overbearing, then this sounds like just an adjustment problem. Perhaps you need to use a manual calibration strategy than relying on software to get it right.

 

[sterling shoote]

OP,

Do you have any settings which seem very distorted, such as from too much gain. This would be perceived as clipping? Usually, gain mismatching will produce a very low or very overloaded signal. The mismatch can come when converting from balanced to unbalanced or vis versa. You may just need to adjust gain for the type of line outputs/inputs you are using, XLR's or RCA. For example, if your gain was adjusted for balanced connections but you were actually using unbalanced connections you might get a very hot signal, or what you might call overload, which will produce a distorted signal. Problems like this occur when using consumer audio equipment with professional equipment. The pro stuff will have balanced connection, which work well with long distance connection runs, while consumer stuff will have unbalanced line connections, which work great for relatively short connection runs. Thing is, something like an active sub does not know what sort of line outputs you have; and, thus, they are sometimes adjustable for gain even when the sub can receive balanced, as well as unbalanced signal. BTW, most professional recording devices which are designed to be compatable with consumer electronics will have a gain adjustment range from -24db to +24db. Also note that gain mismatching can be between source component and amp and or between control amp and active sub. Be sure to look at everything between source and sub.