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

I have a tube integrated amp and a Polk PSW505 sub. I've connected the left amp O/P to the left main speaker & the right amp O/P to the right main speaker.

I've connected the left pre-amp O/P to the left Line In of the sub, and the right pre-amp O/P to the right Line In of the sub.

I get no sound out of the sub, except a low level rumble.

I have connected the polarities correctly.

Any ideas?

Well, thoughts are, can this amp be a unit that disables the pre-outs when the speaker outputs are in use, or does it have a setting that's required to be turned on to activate the pre-outs? Besides checking the manual for some obscure setting requirement, try things one at a time. Run the sub from the pre-outs without the speakers connected; if no result, connect it with the speaker wires to the speaker level inputs to see if it's even working correctly.

Try disconnecting one of the pre-amp outputs to the sub.

Manarex, are you trying to use the pre-out of the main speakers to the sub or the "subwoofer" pre-out?

Also, what are you using to determine that sound is coming out or not? Most material don't have enough low frequencies to be drive a sub loudly.

I should have told everyone that the sub is a Polk PSW505 (rear-slotted vent, with 12" driver, and DSP circuitry). I'm playing Bach & Widor organ music. I've taken off the sub's grill so I can watch the diaphram move, and put my hand in front of the rear slotted port to feel air movement.

I can barely see the diaphram move, and there is no air coming out of the rear-slotted vent. Volume is set at 12 o'clock, and the low pass filter to 60 degrees.

I should also told everyone that this is an integrated tube amp. There is a connection for CD, SACD, DVD, and tuner, all of which are controlled from one multi-position switch. There are also two pre-amp O/Ps, which are not dedicated to anything. I am using one of the pre-amp O/Ps to drive the sub. I'm feeding the positive wire into the Line In+ terminal, and the negative wire into the Line In- terminal.

The main speakers are connected to the amp speaker O/P. The sub low pass knob is set to 60 degrees, the phase to 0 degrees, and volume is at 12 o'clock.

The integrated amp is just a plain-Jane integrated amp, with no processing.

The sub has two pairs of "Speaker Level O/P", and two pairs of "Speaker Level Input". I assume they are for home theatre stuff. I'm using Line In R and Line In L.

The integrated amp has two pre-amp outputs, which I presume were meant to feed two amps. The are no sub O/Ps from this amp.

Ok, I don't know enough these type of connections to be of any help to you since I am not convinced this can work at all. Hopefully, someone more knowledgeable will come along soon make sure of the additional info you provided.

Disconnecting one of the pre-amp O/Ps from the amp, silences the sub completely.

Using the preouts from the amp to drive the sub should work fine. Have you disconnected the mains and see if you can hear anything from the sub?

Unfortunately, there is no manual with this Chinese knock-off integrated amp. I'll try all the suggestions you made.

Many thanks to you and all the other guys for the good suggestions. Looks like I've a busy Friday night ahead of me.

This link provides many different set-up options with diagrams. Hopefully, it'll help.

I see in the article that they joined together the right and left signal out of the amp. It has been my understanding this is not the best thing to do.

Check this out

Well, shoot, maybe my link won't help.

I had thought it would work too until someone at Hsu directed me to the same link.

I just did that, and the sub outputs very distorted audio and low-level thunder or hum.

Thanks very much for your suggestions EFalardeau.

The Polk may be overloading the pre-amp outs. Do you have some other way of testing them?

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.

No I think not, I have a set of M80s powered by a Rotel amp so I know what sounds good and what does not. I also have a Hsu sub with proper bass management and to my ears it sounds better with the sub than without. You very well might have a piece of crap sub that you are trying to get to sound as good as the M60s. If this Polk, not know for good subs BTW, isn't sounding good with what ever you do then it might be time to try a better sub.

Wid: That encourages me to return the sub back to my friend (maybe that's why he gave it to me), and hunt for another one. As for Polk not being known for good subs, you can find people to say HSU, SVS, and all the others are crap. The same for any piece of audio gear, TVs, etc. So, in general, I don't make decisions based on hearsay and the opinions of casual users. And I've read some good reviews on the PSW505, by so-called pros. But we know they're paid off.
I have an acquaintance in Toronto who has bought and tried most of the big-name brands, and says nothing compares to the Polk PSW505. He's had the Polks for a year now, and uses some of the other subs to demonstrate their inferiority to the Polk.
I have a cheap integrated amp driving M60's, and although some may think it's bottom-of the-line equipment, I love it - and that's all that matters to me.

I think collectively, this site has a lot of seasoned and knowledgeable users, and that's why I visit frequently for advise.

Eric, although that particular sub isn't one that would be on my shopping list in that price range, I doubt that it should be described as "crap". It's hard to evaluate someone else's subjective description of sounds, but the "muddy" term that you use may be what any sub playing only the fundamental frequencies with little or no harmonics produces. When you set a sub to roll off above 80Hz or lower and then disconnect the mains, you hear dull thuds, which can't be termed "fast", "tight", "musical", etc. Nevertheless, when combined with the harmonics which the mains play, the net result is full-frequency music.

Hi JohnK: You're right; they're not crappy. It's just after two days of trying to set up the sub I'm getting very frustrated, and letting that frustration get the better of me. I've read many posts and articles that gives you the impression that you just hook up the sub, and away you go to Musicland. The cheap little booklet that comes with the sub doesn't even talk about stereo on its own, so I've wired the sub according to the picture which best depicts my situation. I've also tried the various combos suggested by members of this forum - thank you all for making suggestions that may be a loosing battle. Even Polk's Tech support hasn't responded yet.

John, your post sums up everything very nicely. My problem is that the music sounds considerably better with the subs off. The M60's are sweet, while the sub produces a distorted muddy sound. The peculiar thing is if I plug the pre-amp to the sub LFE I/P, I get the full spectrum of music and it doesn't sound that bad, but the sound is very poor compared to just the M60's playing by themselves. And I've tried every combo of amp, speaker, and sub. My speaker placement is wrong (house being renovated, and my bedroom has become a dumping grounds for anything you can think off). But I would still expect good sounding music. And it seems when I change the CD I'm listening to, I have to adjust the sub's volume.

Can you borrow a different sub from someone else? Perhaps the Polk is damaged in some way.

Mojo: Everyone I know that are running subs have 5.1. Won't this 'manage' the bass?

Mojo: I bought my son the same Integrated Amp that I have. He's driving some no-name speakers he literally found in the garbage, and some Sony stereo car bass speakers with a rip in them. The sound is very good, relatively speaking. Voice never comes out. Everything sounds like one complete system.

If anyone is interested in the 9,000,000 ways to connect your receiver/amp to the PSW505 sub, click on the this link.

http://www.polkaudio.com/homeaudio/products/individual/subwoofers/psw505/

I think I've tried every configuration that makies sense, only to be confronted with failure.

At first I thought subs stink. But after listening to my son's setup (the main speakers and sub are BAD), I think there may be hope.

With those garbage speakers of his, his sytem sounded quite nice. Surely I should be able to pass him in leaps and bounds.

Faulty sub?

Sorry for calling your sub crap, it was uncalled for.

Hi Rick: Were subs invented before the advent of HT. Maybe my amp just doesn't have the voltage levels required to sustain a sub (I think someone on this thread suggested that already). A faulty sub sounds like a reasonable conclusion, since I've tried almost everything suggested on this Forum, and none of them worked, or if they did work, it was to a limited degree.

As for calling my subs crap, I would rather have you call it the way you see, rather than just pussy-footing around. I am not offended in the least bit. It was a straight-forward call after all suggestions were tried, and not a personal attack on me. All you did was put into words what other people might be thinking. Please carry on using descriptives that you think are appropriate. No apology needed, only your good advise.

I ran an M&K sub in a stereo set up long before it was the thing to do. I used the preouts from a Kenwood preamp, Parasound preamp and from my current Rotel before I bought an Outlaw ICBM for my bass management. I never recall having any issues with doing so.

Is there someone you can borrow a receiver from to test the sub?

Manarex you have said your sons setup' sounds not too bad with bad speakers, so the conclusion I come to is the much better M60s now require a much better sub to come up to the same quality and a more powerfull amp would certainly help.

Your friend you mentioned that swears by Polks might consider the big boomy/muddy sound to be better as many people do feel this is the way a sub should sound. I have a boomy muddy sounding Sub and after hearing some much better quality sub, EP600/EP400/HsuSTF1 the Polks/Paradigms and a few others in the stores are not quite in the same league for the same price, IMO. I am now aching to get an EP500 or Hsu.

If you are not happy with that sub I would certainly take it back if you can, no use paying for something you are not happy with, then put that money towards another and try again.

Jason: The M60's are very efficient, so I shouldn't need much drive (should I?). If I just play the M60's, they sound marvelous, and they're loud. I think the subs are rated at 300W continuous and 460W dynamic, so I think I might have the same problem with other subs.
I've talked to other guys at work, and most of them say they use their subs for HT only (that seems like quite a waste).
The EP500 was my first choice. Then I saw that Future Shop put the PSW 505 on for $299, so I couldn't resist. Anyways, I think I can bring them, even though they were advertised by Future Shop as only being available over the Net.

I believe it is only 14 day return policy for FS.

You are correct you should have enough power for the M60s. As it has been suggested on the other Subwoofer thread I think trying to set up the sub calibrated to the same SPL as the M60s at the M60s lowest drop out out point might help, possibly in that 30-50hz range, just to fill in that extreme low end that the M60 can't produce.

I just tried my old D-Box(they make Butt kicker furniture now) sub that goes down into the 25hz range calibrated at 80hz crossover point and it sounded pathetic. I have to drop its calibration point to the M80s lowest output to get it to sound even, still nowhere near what I heard with the EP400 but better.

Jason: It seems to me if I do that, I'll very seldom hear bass or very weak bass. My thoughts so far are that subs are for people who are interested in HT (unlike me). I like plain old stereo (and quad when it was the rage in the early 70's), and I don't think a sub can add anything to stereo. That's just my opinion. Pls. tell me I'm wrong, otherwise I'm going to have to lug a 58 lb. box to futureshop.

You're wrong.

This statement is false.

If "This statement is wrong", then I'll clap with one hand. Let me know what you hear.

Polk got back to me, and told me to to send the DSP section of the sub to California for repair.

Hey hey hey! Sounds like you're not insane, congrats!

Thanks for the confidence booster - I was ready to turn myself in so I wouldn't hurt myself.

Many thanks to all the forum members that guided me through this.

What if they don't find anything wrong?

And so far as not hearing any bass, the sub is there to fill in the gaps the M60s don't play that well so setting it that low to the same SPL as the M60s means you should hear the sub at those levels blended with the M60s not over the top like most people seem to like. Just try it before you send it out or when you get the sub back, it can't hurt.

I see you did try this in the subwoofer thread so never mind!

I feel that you do need a sub for music regardless whether it's stereo or not. Many feel that it's not needed for music. With some music I agree that I don't need it but for the majority, I'm glad it's there to fill in the gap.

I can't see myself ever going without a sub, I've been running one for so long. Even with the M80s in a stereo set up.

Ya know, I just realized that I have been going without a sub in a M80 stereo setup. Of course, I mostly listen on extracted surround (L7 or Neo6).

I just took the sub back to Future Shop for a full refund, less the freight charge of $45, to deliver from Alberta?

I am now free from the shackles of bondage to pursue another sub.

It appears that if you went without a sub for a long time, you didn't miss it, and hence, you simply don't need it. But I don't think that's what you want to hear.

That is no longer my problem (I'm not trying to sound cocky or arrogant) - I got my money back, and I'm now stalking new prey.
The problem is finding stores to audition choices. I'd rather buy on the Internet, play with them if they sound like they have potential, and then make a buy or return to vendor choice.

Actually, no, I had it that way when I was experimenting with stereo listening. i have since returned to surround listening.

Try Hsu's or Axiom's subs. AV123 may also have some models that interest you.

I know Paradigm is going to be releasing their new DSP based subs very soon, might be worth a listen if you can find a dealer.

I noticed you said the sub didn't play anything at 40hz so there was something wrong with it, not sure if that makes you feel any better about subs.

Initially, I got the impression that all you do is plug in a few cables between the sub and amp, and away you go. And that certainly is not the case - there's a lot of work involved. After putting 8 hrs of experimenting, I didn't know whether I was coming or going and finally I went into sub-overload. Any derogatory remarks I may have made about subs, were the ravings of a frustrated man.
I apologize for bringing the forum 'down'. But now I'm ready to give it another whirl.

Jason: At 40 Hz, there was a bit of buzzing, and you could bearly hear CD audio trying to make its way out. I presume that if you listen to pop music, you'll barely hear anything coming from the sub?