Pairing subwoofer with a speaker system; volume control amidst OSX/iTunes/amp

[Libertine Lush]

Hello,

I have a general, novice audio question.

I'd like to hook up a subwoofer to a Ferguson Hill amp+speaker system that'll be connected to my MBP. I was told by a Ferguson representative that as long as it's a powered sub, I can choose any sub. That I don't need to worry about matching impedance. Is that true?

Also, do I need to match the RMS either?

And, where should I set the numerous volume settings available. I will have my MBP hooked up to an external DAC (HRT's Music Streamer II), which will connect to the Ferguson amp. So there will be the volume setting in iTunes, OSX, and the Ferguson amp to consider. Where should I set all 3 volume controls--and why?

Thank you for any help.

 

[John T]

There is nothing to suppose that the Ferguson rep was wrong in his advice regarding impedance matching. Remember, you are only connecting up computer sound - not a hi-fi system where impedance matching can be important.

What do you mean by, "do I need to match the RMS either?"

As far as setting the various controls, you'll find it's best to try various settings to determine which you prefer.

 

[Libertine Lush]

What do you mean by, "do I need to match the RMS either?"

I've since learned it only matters with an passive sub.

As far as setting the various controls, you'll find it's best to try various settings to determine which you prefer.

I'm most curious whether it would have any affect on the audio quality.

 

[John T]

I've since learned it only matters with an passive sub.

With respect, I get the feeling that someone is trying to take advantage of your obvious lack of knowledge of audio reproduction. RMS stands for "Root mean square" which is used in the definition of the output power of an amplifier, for example "the output of the amplifier is 25W RMS". By it's very nature, the output of a passive sub cannot be varied. However, the output of an active sub (as 99.9% of them are) can be varied to conform with that of the amplifier it is working with.

I'm most curious whether it would have any affect on the audio quality.

The best way to find out is to try it and see which adjustment gives the most satisfying result.

 

[Libertine Lush]

With respect, I get the feeling that someone is trying to take advantage of your obvious lack of knowledge of audio reproduction. RMS stands for "Root mean square" which is used in the definition of the output power of an amplifier, for example "the output of the amplifier is 25W RMS". By it's very nature, the output of a passive sub cannot be varied. However, the output of an active sub (as 99.9% of them are) can be varied to conform with that of the amplifier it is working with.

I know what RMS means.

From googling--results mostly referring to car subs+amps--they would all mention matching impedance and the RMS output. The Ferguson Hill rep told me I can choose any amp, and that I don't need to match impedance since the sub is powered. Then in a different forum, where I posed this question as well, I was told: "You don't have to pay attention to the watts, at least not matching your system. I've used a 1500 watt subwoofer with a 50 watt per channel amp."

So which part of that do you disagree with? In which case, if any, do I need to match the RMS?

 

[John T]

I know what RMS means.

From googling--results mostly referring to car subs+amps--they would all mention matching impedance and the RMS output. The Ferguson Hill rep told me I can choose any amp, and that I don't need to match impedance since the sub is powered. Then in a different forum, where I posed this question as well, I was told: "You don't have to pay attention to the watts, at least not matching your system. I've used a 1500 watt subwoofer with a 50 watt per channel amp."

So which part of that do you disagree with? In which case, if any, do I need to match the RMS?

Your question has been answered three times! By me, by the Ferguson Rep and by the Forum responder. Try to ignore terms like RMS. As the Ferguson rep stated, the sub is powered (therefore it is active and not passive as you earlier stated) and so its output can be adjusted to suit the output of the power amplifier (as I said in my earlier post).

 

[quasinormal]

From my experience adjusting the volume of the sub is quite difficult. You need to make very small adjustments with an aim to subtly improving the body of the music, rather than than pronouncing the bass. (certain hip hop is an exception for me) If the sub sounds separate (ie. if it doesn't disappear) from the full range speakers the phase control on the sub may need adjusting.

 

[Libertine Lush]

From my experience adjusting the volume of the sub is quite difficult. You need to make very small adjustments with an aim to subtly improving the body of the music, rather than than pronouncing the bass. (certain hip hop is an exception for me) If the sub sounds separate (ie. if it doesn't disappear) from the full range speakers the phase control on the sub may need adjusting.

Thanks. Kept in mind.