Pairing subwoofer with a speaker system; volume control within OS/iTunes/amp

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 laptop. 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 laptop 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, the OS (OSX Lion), and the Ferguson amp to consider. Where should I set all 3 volume controls--and why?

Thank you for any help.

 

You have to match the impedance or it can stress the amp. You also need to match the RMS or it can pump too much power and blow your woofer.

Just remember that amps are usually rated for Peak RMS, while speakers/woofers are usually rated in continuous RMS.

 

Is that the case even with a powered sub though? The Ferguson rep told me I only need to match the impedance when it's a "non powered subwoofer being driven by a power amp."

Thanks.

 

If you get an active subwoofer(powered by its own individual amp) then none of the things your worried about matter. You can simply send it a line level signal(RCA) to it and plug it into the wall and its done. They generally have their own frequency cross-overs in them so you don't even have to worry about that.

 

Nope. My bad i assumed the amp was gonna drive the sub you were planning to get.

If its a self powered sub then all you really need to worry about is an input signal as Syndrome pointed out.

 

Great to get confirmation of the rep's statement.

I merely intend to get an entry level sub, as the Ferguson Hill will already set me back a bit. So taking the top 2 sub results in Amazon, which happen to be in the <$100 range, could you help me confirm that they are indeed powered subs? They seem to be from what I can tell:
Amazon.com: Polk Audio PSW Monitor Series Powered Subwoofer (Single): Electronics
Amazon.com: Sony SA-W2500 Performance Line 100 Watt Subwoofer: Electronics

While you say I can just forget about ohms and RMS, I wonder is there still some sort of RMS recommended range for a powered sub in relation to the amp it'll be attached to? (Or maybe I'm just finding it hard to let go of the ohms and RMS matching thing after all the time spent googling about it yesterday. What a relief.)

Is frequency cross-over related to Phase or Low Pass? Just 2 terms I noticed in the back panel of the Polk Audio sub (the first Amazon link)?

Thank you for the info.

 

Crossovers are the low-pass basically. The phase adjusts it so it sounds 'right' with your system, most lower end sub's have a switch on them instead of a knob. But for the most part a switch is plenty good enough.

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. More importantly look at the frequency response, which is how 'low' it will go. The watts is going to effect how 'loud' it will be. But with a ported subwoofer then 100 watts isn't to bad.

If your tight on space and willing to up your budget a bit then this is a good option. Its high end stuff and sounds pretty good for the size.

If you have the space, go with a ported sub though, you get more noise for your money, and they use less power.

 

Space isn't an issue for me, as I'll merely place it beneath my desk, which works out fine as the cheapo sub I have underneath now also offers to be my foot stool.

I'm really intrigued by the Energy sub you mentioned, due to it's compact size. However, its frequency response doesn't go as low as either of the 2 subs (<$100 Polk Audio and Sony) I posted. Add that to the fact that it's much smaller as well, can it actually be better? What makes it particularly high end?

Thanks.

 

I do have one of these so I will tell you that the frequency doesn't go as low as I would like it to. But being closed like that makes it so the bass it does have is much tighter and more crisp sounding. The highest end thing is just how much sound it can make for its size and its got the better controls, like a phase knob instead of switch. If you don't need to squeeze it into a small location then I think a good open subwoofer is your best option.

The only issue I have with those two subs you showed, they rate the frequency response but they don't show a tolerance. A real measurement would say +/- a number of dB. Without that then they could very well be 'cheating' to get that low of a frequency response. Or if it actually does go that low then it will be so low of a dB(loudness) that it wouldn't actually matter in a real world listening situation.

Edit: just seen this deal, Its a great sub really thumps and goes very very low. I've spent a few good nights listening to one of them. I know its above your budget, but hey is sound equipment, thats what you get for asking.

 

Is a lower tolerance # better? I googled keywords "frequency response" and "tolerance," but couldn't find any layman's explanation of it, but it did seem like the lower the dB the better. And is there a certain db # or range that would be considered preferable?

Thanks for the other sub suggestion. I'll definitely look into it.

 

Yes the lower the +/- the dB the tighter 'tolerance' which means the more honest the company is being with you. I've seen many subs list that they go down to 28hz, but they wont list how many +/- dB, which means that it may go down to 28hz, but so quiet you will never hear it.

I usually aim from around +/- 3dB at the highest.

 

Got it.

Thanks for all the great help you've provided in this thread, Syndrome.