[Joe Bloggs]

Well, I don't exactly want to buy one, but I'd like to know if any such thing exists! My friend is driving a pair of minimonitors out of a subwoofer output with more than 100W power, and they still have this grainy sound, which has been diagnosed by his uncle to be a problem with inadequate power! I knew that speaker efficiency is not directly related to size, but I didn't know such inefficient minimonitors existed??

 

[Budgie]

Generally, as speakers get smaller the efficiency gets worse. One of the trade offs with small speakers. The smaller drivers have to work harder to produce the same volume level, compared to a larger woofer, requiring more power from the amp. Also one of the reasons small speakers don't go low in frequency response.

 

[Joe Bloggs]

... And if the sensitivity is still high, they won't be able to play bass worth a damn, right?

Funny how big ass speakers are always driven by big ass amps? Are you telling me that my Onkyo 20Wpc amp will have no trouble driving most of the floorstanding speakers out there?!?

Those ole hand-me-down Sherwood speakers are 8ohm 90dB/W--maybe I should try them with the Onkyo amp?

Also, I wonder what are the sensitivity figures for subwoofers like?

 

[yage]

Uh... aren't subwoofer outputs for *subwoofers*?

Subwoofer amps aren't designed to handle the full audible spectrum and are, usually, Class D devices.

You might be listening to a double whammy of suckiness...

 

[Joe Bloggs]

Where did I mention anything about subwoofer outputs and subwoofer amps?

 

[darkclouds]

Joe, what ya smoking?

"My friend is driving a pair of minimonitors out of a subwoofer output with more than 100W power, and they still have this grainy sound, which has been diagnosed by his uncle to be a problem with inadequate power!"

I'd expect a whole lot of problems beyond graniness when driving speakers out of the subwoofer output.

In anycase, graininess can be attributed to everything from source to quality of amps and speakers. Basically, you can have a high power amp and still end up with a less than smooth sound.

 

[Joe Bloggs]

Well, since her amp doesn't have a subwoofer output, it goes like this:

amp speaker output -> subwoofer -> speaker output on subwoofer

So the amp is acting as a crude preamp while the amp inside the subwoofer is acting as the real power amp for the main speakers.

So I agree about the potential poor quality of the subwoofer amplified output, but that output WAS designed for driving main speakers, after a fashion--I assume there would even be a crossover cutting out the low freqs.

And the input signal is from the speaker output on the original amp, not the subwoofer output that it does not have

Sorry that I haven't been clear enough

 

[elipsis]

Quote:

Originally posted by Joe Bloggs Well, since her amp doesn't have a subwoofer output, it goes like this: amp speaker output -> subwoofer -> speaker output on subwoofer So the amp is acting as a crude preamp while the amp inside the subwoofer is acting as the real power amp for the main speakers.

I'm not sure about that.

My sub has high-level inputs and outputs, and I'm almost 100% that it does NOT amplify the main speakers, it simply uses the already amplified incoming signal as a pre-out to drive the sub, then sends the amped signal straight on through to the mains.

 

[ze-ant]

....

 

[Joe Bloggs]

Well, one way for you to check is to feed your subwoofer with a line-level input instead of a speaker-level input and see if it can still drive the main speakers.

 

[yage]

wait, so if the chain is:

amp speaker output -> subwoofer -> speaker output on subwoofer

then that should mean that the subwoofer is *not* powered by its own amp. otherwise, why would you take the output from the speaker terminals of the amp? so there is a crossover component for the sub and a passthrough for the main speakers.

if the sub is indeed not powered, then maybe it's draining away too much power from the amp causing the harsh sound coming from the main speakers...

 

[Joe Bloggs]

It IS powered, okay? As I told you, the minisystem she uses does not have subwoofer output (nor does mine). How would you connect a subwoofer to such a system then? You use the speaker output as a variable line output. You can use the headphone out for the same purpose...

Me, I preferred to 'bi-wire' (I don't suppose that's what the name is actually used for

) both the subwoofer and main speakers directly into the minisystem amplified output, to bypass the intermediate subwoofer stage for the main speakers. I shorted out my first unit because I forgot to insulate the pin plugs, which were all metal

 

[yage]

Oh okay. Well, look, I've only heard of two ways to connect a sub to a system.

Method 1:
Use the pre-outs (or sub-out) on a receiver (RCA-RCA connection) to the subwoofer inputs. The sub has its own amp because this is a line level connection.

Method 2:
Use the speaker outputs from the amp to the sub (speaker wire connection). The sub doesn't have an amp (or doesn't need one) since the signal is already amplified. Then either connect the main speakers to the passthrough on the sub or to the speaker outputs on the amp.

 

[Joe Bloggs]

I'm pretty sure that my powered subwoofer, at least, only takes a line level input even on the speaker binding posts. That's because I measured a DC resistance of well over 10k. While not an accurate measurement of the impedance throughout audio frequencies, that impedance should still be within the ballpark.

 

[yage]

Huh.

Well I'll be damned...