Axiom Home Page Forums General Discussion Stereo Connecting Integrated Amp to Sub

Mojo: Good thought. Haven't audio vendors pretty much standardized on things like that. 47K seems to come to mind as the impedance of the O/P stage of a pre-amp and amp.

Impedance isn't the only issue but gain (output voltage) is also important of course.

If your pre-amp has an output impedance of 50K and the Polk sub has an input impedance of 10K Ohms, you may be in trouble particularly if you use long interconnects. The voltage across the sub may be too low to drive it.

So try to use a short interconnect between the sub and the pre-amp outs to see if it's any better. If it is, then your pre-amp output impedance is too high. It's probably not too high to drive most power amplifiers but it may be too high to drive the sub.

Also try turning up the volume of the pre-amp all the way to see if it makes a difference. If it does, then gain/output impedance is at fault.

Mojo: I think I've tried every combo of amp and sub wiring. The only one that seems to work is to connect the pre-amp to the LFE sub I/P. But if I do that, and listen to the sub, I hear the full spectrum of music making its way true. So the sub is acting as 3rd full spectrum speaker, perhaps with somewhat better bass?

Okay, your last post gives a clue: if you get reasonable output using the "LFE" input(which bypasses the sub's internal low-pass filter), that indicates that the internal filter may be defective or the setting inaccurate. If by "60 degrees" you meant that you set it at 60Hz, that may be shutting off everything but the very lowest rumbles(which is actually what a sub sounds like; in no way are they "musical"), so try higher settings on the sub low-pass filter.

Hi John: If my sub is set correctly, should I be hearing any vocals (baritone opera singer excluded.) If I switch to playing instrumental music (pipe organ), and put my ear to the sub, I only hear some kind of 'dirty' bass. If I fool with the volume knob on the rear of the sub to get rid of the 'dirty' bass, I get nothing.

What should a properly set up sub sound like in terms of vocal and instrumental. Again, maybe I'm expecting something the sub can't do.

Every musical note is composed of a fundamental frequency and overtones. What distinguishes a C note on the oboe from a C note on the piano are these overtones.

A sub will be produce the fundamental frequency with a few overtones depending on the instrument. If you listen to the lowest note on a pipe organ for example, you will hear the fundamental frequency of 16 vibrations a second and a few overtones up to the cut-off frequency of the sub. For the vast majority of music, your sub will produce the fundamental frequency and your mains will reproduce the overtones. So when you listen to just your sub, expect it to sound like a feeble beast that's had the wind knocked out of it and is now burping, farting, moaning and groaning. When you turn on your mains, they'll add the overtones that define the music.

Now having said all of that, your sub may just be crap .

Finally someone’s tells it like it is, I was wondering how long it would take.

Mojo:

"A sub will be produce the fundamental frequency with a few overtones depending on the instrument."
This true, but so will every other speaker in the world. It's what you do to the speaker that determines what it spits out. My amp can only control volume.

"For the vast majority of music, your sub will produce the fundamental frequency and your mains will reproduce the overtones."
My mains reproduce everything, not just overtones, while the subs add 'garbage'. The mains by themselves sound absolutely magnificent (M60's v2).

You'll have to remember that I have a plain-Jane integrated amp with no controls to play with, except volume. I have two pre-amp O/Ps. The amp is incapable of any type of 'management'.

I'm beginning to believe the sub is CRAP!

Wid: Perhaps all subs are crap, and you, along with some others have been indoctrinated into accepting that crap as enhancing your AV experience.

Take twenty people (arbitrary, but statistically meaningful number?), ask them what's crap, and I'll bet that between all of them, they'll have named every sub ever made.

Finally I may have said it like it is; I was just wondering how long it would take.

Mojo: After hours of screwing around, the sub is set not to play vocals, or any mid-frequency stuff - all I get out is what sounds like muddy bass. And I don't know what else I can do, except bring it back.

Suggestions for a replacement for ~$500, or am I wasting my time for something in that price range? I wanted to start small, and see if I'm going to encounter the same experience I just had.