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Bi-amping gone wrong....need help!

post #1 of 22
Thread Starter 
Hello all first post. TIA

This is using a Denon 3805

What is the correct process for bi-amping a Denon 3805

Speakers are Polk Audio rti12s with the bridges removed.

This is what I did last night to no avail....all I got was a low hum from the low range but not actual sound production outside of the low hum.

1. Connected a short pair of RCA cables from the front pre-outs to an un-assigned input (VDP in this case)

2. Used the remote to turn on Zone 2 Power

3. Selected VDP for Zone 2

4. Disconnected RCA cables from the front and hooked them up to Surr/Multi Pre-out and into VDP input.

5. Removed connectors for bridging the speakers

6. Connected the standard L & R fronts via speaker wire to the High Freq. inputs on the speakers.

7. Connected the surrounds (lower far right speaker wires outputs) from the Denon 3805 to the low frequency on the speakers.

I get a bad hum but no sound.

I adjusted the Zone 2 Master Volume up to 0.0. I then turned it up a couple dbs and the hum gets louder and when it goes up to 3 dm I get a nasty feedback from the low range and then rec. shut offs and flashes blinking red lights meaning it is protecting itself.....

What the am I doing wrong?

My 4806 power supply took a dump and is back in for service and this is my old rec
post #2 of 22
Don't bother. You will gain zero benefit unless you replace the crossover network in the speaker with an electrical one anyway.
post #3 of 22
Thread Starter 
Aren't the speakers bi-amp and have crossovers for the upper and lower range?

So wouldn't biamping provide more clarity in the upper & lower range?
post #4 of 22
Quote:
Originally Posted by zoeybadm View Post

Hello all first post. TIA

This is using a Denon 3805

What is the correct process for bi-amping a Denon 3805

Speakers are Polk Audio rti12s with the bridges removed.

This is what I did last night to no avail....all I got was a low hum from the low range but not actual sound production outside of the low hum.

1. Connected a short pair of RCA cables from the front pre-outs to an un-assigned input (VDP in this case)

2. Used the remote to turn on Zone 2 Power

3. Selected VDP for Zone 2

4. Disconnected RCA cables from the front and hooked them up to Surr/Multi Pre-out and into VDP input.

5. Removed connectors for bridging the speakers

6. Connected the standard L & R fronts via speaker wire to the High Freq. inputs on the speakers.

7. Connected the surrounds (lower far right speaker wires outputs) from the Denon 3805 to the low frequency on the speakers.

I get a bad hum but no sound.

I adjusted the Zone 2 Master Volume up to 0.0. I then turned it up a couple dbs and the hum gets louder and when it goes up to 3 dm I get a nasty feedback from the low range and then rec. shut offs and flashes blinking red lights meaning it is protecting itself.....

What the am I doing wrong?

My 4806 power supply took a dump and is back in for service and this is my old rec

IF your receiver is biamp capable there will be a "redirect" mode that you have to use. There will be no need to run anyhting from your preouts to an unused input. Everything will happen internally.

In short check your maunal.

DonoMan, I'm sure the OP really appreciates your very thoughtful (read:stupid) reply.
post #5 of 22
Quote:
Originally Posted by Nuthed View Post

DonoMan, I'm sure the OP really appreciates your very thoughtful (read:stupid) reply.

It was true, though. Feel free to explain otherwise if you disagree.
post #6 of 22
Quote:
Originally Posted by DonoMan View Post

Don't bother. You will gain zero benefit unless you replace the crossover network in the speaker with an electrical one anyway.


Grow up! For the final time read this link.

This is the TRUTH whether you or Tom believe it or not.
post #7 of 22
Thread Starter 
I was using this as my guideline but I don't get any sound at all.

I thought I followed the instructions to the letter but apparently something is not working properly.......

http://www.audioholics.com/reviews/r...st-impressions
post #8 of 22
Thread Starter 
I assume by redirect you mean I can select the input. I was using the surround amp and feed the preout into an used input (VDP) in this case. I assumed that this would feed the full range surround signal from the preout into the input thus using the surrounds to drive the lows and the fronts for the highs with the internal crossovers doing their thing........
post #9 of 22
If you read that link, you will see that you did not follow the instructions. You are supposed to set it up for zone 3, not zone 2. Then there are a bunch of remote presses you didn't do either.

As for the efficacy of doing this... I tend to agree with the nay-sayers. I don't see the point of bi-amping if the two power amplifiers are amplifying full-range signals, which is a separate issue from removing the crossover from the speaker. As I understand it, the point of bi-amping is to prevent large bass-power transients from overloading the midrange and treble amplifier, by separating the bass and treble signals with active filters. If both amplifiers are amplifying a full range signal, the bass frequencies can still overload the treble amplifier. An audio power amplifier is a voltage-controlled device, and you can drive it into clipping even with no speaker attached. Connecting two full-range amps will provide improvements more on the order of bi-wiring than bi-amping.

The crossover is another issue. It does provide phase-coherence at the crossover point, so replacing it is a tricky business. You would have to know its response, and synthesize the same filter in the electronic crossover. This is probably beyond the ken of the average user. However, leaving the crossover in the speaker, and using gentle low pass and high pass filtering on the bi-amps will give the desired result. Low frequencies are attenuated by the high pass filter so they don't overload the treble amp, and the crossover still controls the speaker cones at the crossover frequency. The user still needs to set the high pass filter so it is low enough to overlap the crossover frequency, but this is a relatively easy adjustment.
post #10 of 22
Quote:
Originally Posted by zoeybadm View Post

Aren't the speakers bi-amp and have crossovers for the upper and lower range?

All 2way speakers have such crossovers.

Quote:


So wouldn't biamping provide more clarity in the upper & lower range?

No. The signals are separated by the same crossover with one amp or two (unless you replace the built in crossovers with a custom-designed electronic one placed before the amps).
post #11 of 22
Thread Starter 
Oh I read the link several times using the setup for Zone 3........never got any sound from the low range.......

In fact I was not able to adjust the Zone 3 adjust. I checked the manual and the zone 3 is fixed out with no volume adjustment so I don't know how I am supposed to match the dbs from low to high.
post #12 of 22
Answered in your other thread, but I'll post it here, too. Your receiver has no way to assign the 6th and 7th channel amps to bi-amp duty. You seem to be on the right track to doing it as described in your link, above. Not sure why you aren't getting any output from the 6th and 7th channel amps. Did you assign the input you used to loop the front pre-outs back into the receiver to Zone2?

And I'm not going to tell you flat-out NOT to bi-amp this way, but since your receiver has no provisions for assigning the extra amps to bi-amp duty, and since the method you are trying to bi-amp with is, for the most part, a "dirty" method, and since the benefits of passively bi-amping are marginal, my recommendation would be to forego passively bi-amping your speakers.


http://www.audioholics.com/reviews/r...denon-avr-5803

Note the steps taken to level-match the Zone2 output with the front channel output prior to removing the jumpers.
post #13 of 22
Quote:
Originally Posted by gsmollin View Post

If you read that link, you will see that you did not follow the instructions. You are supposed to set it up for zone 3, not zone 2.

It doesn't matter whether you use Zone2 or Zone3 to try this "dirty" bi-amp method. In the link to the method he tried, they point out that the only reason they use Zone3 is to leave Zone2 available for a true multizone setup.


Quote:
Originally Posted by zoeybadm View Post

In fact I was not able to adjust the Zone 3 adjust. I checked the manual and the zone 3 is fixed out with no volume adjustment so I don't know how I am supposed to match the dbs from low to high.

Hmmm...................?

According to the link you posted, they used Zone3 and their instructions would lead one to believe that the Zone3 output IS adjustable.
post #14 of 22
Quote:
Originally Posted by zoeybadm View Post

I assume by redirect you mean I can select the input. I was using the surround amp and feed the preout into an used input (VDP) in this case. I assumed that this would feed the full range surround signal from the preout into the input thus using the surrounds to drive the lows and the fronts for the highs with the internal crossovers doing their thing........

No, the "redirect" he is referring to is for receivers that DO have provisions for assigning the 6th and 7th channel amps to bi-amp duty.

Are you looping the front R/L pre-outs into the "VDP" input or not? Once you do this you also have to assign the input you used (ie. VDP) to the Zone (2 or 3) that you are trying to do this with.
post #15 of 22
Quote:
Originally Posted by Nuthed View Post

If your receiver is biamp capable there will be a "redirect" mode that you have to use. There will be no need to run anyhting from your preouts to an unused input. Everything will happen internally.

Nuthed, his receiver has no provisions for assigning the 6th and 7th channel amps to bi-amp duty. What he is trying is a "trick" that loops the front pre-outs back into an unused pair of analog inputs on the receiver. This unused input (VDP in his case) is assigned to Zone 2 (or 3). Then the Surround Back/Zone 2 (or 3) speaker outputs will output an identical signal to that which is output from the front R/L speaker outputs.
post #16 of 22
I'll post this once more zoeybadm, in case you missed it:

..................I'm not going to tell you flat-out NOT to bi-amp this way, but since your receiver has no provisions for assigning the extra amps to bi-amp duty, and since the method you are trying to bi-amp with is, for the most part, a "dirty" method, and since the benefits of passively bi-amping are marginal, my recommendation would be to forego passively bi-amping your speakers.
post #17 of 22
Thread Starter 
Quote:
Originally Posted by sivadselim View Post

I'll post this once more zoeybadm, in case you missed it:

..................I'm not going to tell you flat-out NOT to bi-amp this way, but since your receiver has no provisions for assigning the extra amps to bi-amp duty, and since the method you are trying to bi-amp with is, for the most part, a "dirty" method, and since the benefits of passively bi-amping are marginal, my recommendation would be to forego passively bi-amping your speakers.

Noted........I am going to try it both ways and see what sounds better. I am going to start from scratch by matching the sound levels prior to taking the bridges off and see if that helps.

Yeah it is a dirty method but driving only 120 wpc which is more likely 60-70 at best seems like very little. I would prefer to use a separate amp but nothing within my price range is reasonable to drive the fronts (at least what the wife will let me spend if you know what I mean).
post #18 of 22
Quote:
Originally Posted by zoeybadm View Post

Yeah it is a dirty method but driving only 120 wpc which is more likely 60-70 at best seems like very little.

Even if the power when passively bi-amping was completely additive (and it's not; it's far from it) the very most you'd stand to gain is +3dB of headroom.



Quote:
Originally Posted by zoeybadm View Post

I would prefer to use a separate amp but nothing within my price range is reasonable to drive the fronts (at least what the wife will let me spend if you know what I mean).

What is your budget? If you want to get more power to them, skip bi-amping altogether and just buy a more powerful amp for outboard use.
post #19 of 22
Took a look at the owners manual and it does not say anything about bi-amping.You can not feed a output back into an input on the same receiver/amp.
post #20 of 22
Quote:
Originally Posted by brendy View Post

You can not feed a output back into an input on the same receiver/amp.

Yes, you can. Is it kosher? That's arguable.

READ
post #21 of 22
I know this is very, very old, but I just ran across it and for whatever reason, I read it. I felt like there was an un-resolved issue that I could address. The OPs initial problem started here:

"4. Disconnected RCA cables from the front and hooked them up to Surr/Multi Pre-out and into VDP input."

You should not have done that. you need the RCA cables to go from the LR Main preouts INTO the VDP input assigned to Zone 2.

I did have trouble back when I first tried this with the hum, but I switched out my first pair of RCA cables for another set with better shielding, and the hum disappeared completely.

As for the benefits of doing this, I imagine it depends completely upon your speakers and their internal crossovers/etc, but if you have the right kind of speakers, there is an obvious difference in the quality of 2-channel sound.

I have a set of Axiom T80m towers that went from pretty good to really good when I finally removed the jumpers and did the bi-amp hack.

I was skeptical, having read a lot of "it won't matter" posts on the internet. Then I realized it would only take me 10 minutes to change it back if there wasn't a noticeable improvement, so why not give it a try?

I was very, very surprised by how much improvement there was in the overall sound coming from the speakers.

Maybe the Axiom towers needed more than the 3805 was feeding them through just 2 channels. I don't know.

But if you have a 5.1 setup and aren't using Zone 2/3 for another physical zone, it will only cost you a few minutes to find out if your speakers will appreciate the additional amping. And there is at least a decent chance that they will.

Feel free to let this post sink back down to the depths. But at least now when someone goes searching for this topic, they won't be left wondering...
post #22 of 22
If it sounds good to you, great, but I wonder whether there is any reason to believe the levels of the loopback preouts are necessarily precisely the same as the internal feeds. Which is to say maybe you changed the balance of woofer to tweeter by using signal paths that are unmatched. So it might be different and even more enjoyable to you but unbalanced from a FR perspective. Or it might be perfectly balanced.

The power gain is unlikely to make a difference. It is really modest, since real program material has about 80 percent of the power to the woofer and 20 percent or less to the tweeter. Assuming the whole 20% extra available power to the woofer is used that's less than a decibel of added clean headroom.

On the other hand if you listen really loud it's possible you have occasional clipping. Although the tweeter channel receives a full range signal and produces full range voltage swings, the very high effective impedance of the crossover means the tweeter amp is not putting out significant current at those lower frequencies, so it is making much less power than the woofer amp. WHich might mean that you're keeping the high frequency artifacts of clipping entirely out of the tweeter. Which I'd expect to sound better.
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