Bridging

[HackMan55]

I have recently purchased a used avr, an Integra 70.2. I have owned a few other receivers over the past five years or so, but this is the first that has an option to bridge the front speakers.

I'm still mostly ignorant about home theater in general but have read enough to know the general consensus is that biwiring is a waste of time. Does bridging offer noticeable improvement? I assume the Integra can more than power the speakers without it but it would be easy enough to do if there is any point to it.

Front speakers are Polk s55's in a 7.2 setup at a listening distance of about twelve feet. Thanks in advance and for all the great advice in general this forum offers. I rarely post but am a frequent lurker.

 

[Kvn_Walker]

Bridging an amp just approximately doubles its power to the connected speaker. If your Polks already get loud enough without it, then it isn't necessary.

But try both ways and see if the change is an improvement for you personal tastes.

 

[lovinthehd]

You lose impedance capabilities when bridging, the amp would see lower (half) impedance from your speakers when bridged so you generally don't want to bridge the amp without that consideration. I don't see detailed measurements of the S55s for impedance (they're nominally 8 ohm rated) but think they probably do dip down near 4 ohm at times.....so I'd probably not bother with that amp at least....if the amp were rated to 2ohms perhaps, but I don't even see a 4 ohm rating for the Integra.

 

[OHMisback]

biwiring is a waste of time.

But Biamping isn't. If you're using the bass section on the speakers. Do you have a preamp option out? That's a nice option on an AV. HTs preamps usually have it..
It's easier on my HT to just add SS class D amps. I run valves on the mids and highs. Hybrid LS planars.. The bass sections in separate cabinet.

Same difference, though.

I have a couple of older AV that let you biamp the mains in the setup.. 5/7.1 systems HK, Mac, Krell Denon. They can get LOUD if not anything else. Good party setup. The timing is still off though.. DSP is a wonder though..

 

[lovinthehd]

But Biamping isn't. If you're using the bass section on the speakers. Do you have a preamp option out? That's a nice option on an AV. HTs preamps usually have it..
It's easier on my HT to just add SS class D amps. I run valves on the mids and highs. Hybrid LS planars.. The bass sections in separate cabinet.

Same difference, though.

I have a couple of older AV that let you biamp the mains in the setup.. 5/7.1 systems HK, Mac, Krell Denon. They can get LOUD if not anything else. Good party setup. The timing is still off though.. DSP is a wonder though..

How does passive bi-amping, particularly with an avr, get noticeably louder?

 

[mono-bloc]

Bridging an amp just approximately doubles its power to the connected speaker

All bridging of an AVR, [or by-amping / by-wireing ] is completely pointless, it serves no point except for the fact you need to buy more wire. All it's going to do is. increase the headroom of the amp. Output volumes are controlled by the volume control on the amp. Nothing more nothing less .

 

[fmw]

You lose impedance capabilities when bridging, the amp would see lower (half) impedance from your speakers when bridged so you generally don't want to bridge the amp without that consideration. I don't see detailed measurements of the S55s for impedance (they're nominally 8 ohm rated) but think they probably do dip down near 4 ohm at times.....so I'd probably not bother with that amp at least....if the amp were rated to 2ohms perhaps, but I don't even see a 4 ohm rating for the Integra.

Lovin' makes a critical point here. Bridging is seen often enough in commercial sound reinforcement applications where amplifiers are designed to handle low impedances. I doubt that it will produce anything positive in a home AVR. I even suspect that the designers of the AVR put in circuitry to protect the amps from overheating due to low impedance making the feature pointless in the first place. Because a piece of equipment has a feature doesn't require you to use it. I, like Lovin' recommend you not use it in your application.

 

[TLS Guy]

I have recently purchased a used avr, an Integra 70.2. I have owned a few other receivers over the past five years or so, but this is the first that has an option to bridge the front speakers.

I'm still mostly ignorant about home theater in general but have read enough to know the general consensus is that biwiring is a waste of time. Does bridging offer noticeable improvement? I assume the Integra can more than power the speakers without it but it would be easy enough to do if there is any point to it.

Front speakers are Polk s55's in a 7.2 setup at a listening distance of about twelve feet. Thanks in advance and for all the great advice in general this forum offers. I rarely post but am a frequent lurker.

I would be very reluctant to bridge receiver amps. The speakers must have twice the impedance rating of ones required for non bridged application. Unless you have a reliable impedance curve, or can measure it, you will very likely blow up the receiver. In addition, if you make a mistake in the set up, it will be a receiver destined for recycling.

Even if it is safe, and possible, you will only gain 3 db. Bridging should only be undertaken by the experienced.

 

[HackMan55]

Really appreciate all the input, everyone. That's what is great about this site, you can always learn something.

 

[Audiophile Heretic]

I think in terms of power, voltage, current, and impedance. Amplifiers are voltages sources. Bridged amplifiers are amplifiers in series. The voltage is doubled, but the current everywhere in the circuit must be the same, so driving one 8 ohm resistor with bridged amplifiers is equivalent current to driving one 4 ohm resistor with each amplifier. The total power in the bridged amplifier circuit driving 8 ohms is double the 4 ohm power of the amplifiers. Most amplifier current limits do not allow double the 8 ohm rated power into 4 ohms. The voltage gain of bridged amplifiers is +6dB. Because of amplifier current limits, the power increase of bridging is +6dB or less. Bridging can be significantly louder.

Passive biamplification is very different. Passive biamplification divides separate low and high frequency speaker impedance, current, and power between separate amplifiers. Amplifier voltage driving separate low and high frequency speaker circuits must be the same to preserve speaker frequency balance. The impedance, current, and power of separate low and high frequency speaker circuits is the same whether both low and high frequency speaker circuits are driven by one amplifier or separate circuits are driven by separate amplifiers. The only advantage to passive biamplification is that less current and power is required from each amplifier and separate amplifiers have independent current limits. Passive biamplification insignificantly increases current and power driving low complex impedance speakers with music signals. Most of the additional power of two amplifiers can't be used with passive biamplification. Passive biamplification does not make the sound significantly louder.

 

[Audiophile Heretic]

All bridging of an AVR, [or by-amping / by-wireing ] is completely pointless, it serves no point except for the fact you need to buy more wire. All it's going to do is. increase the headroom of the amp. Output volumes are controlled by the volume control on the amp. Nothing more nothing less .

Bridging is not like passive biamping or biwiring. Bridging does not require additional wire.

Bridging places amplifiers in series. Bridging potentially increases the amplifier voltage +6dB, but does not increase the available current.

The volume control controls system voltage gain. Amplifiers are voltage sources. Speaker impedance determines amplifier current and power output.

Passive biamplification divides separate low and high frequency speaker circuits between parallel amplifiers. The voltage output of both amplifiers must be the same to preserve speaker frequency balance.

Active biamplification is totally different than passive biamplification. Active biamplification of the main speakers cannot be simply implemented from an AVR. Active biamplification requires elimination of the speaker passive crossover network low and high pass filters. Active biamplification has many advantages over passive biamplification.

 

[Audiophile Heretic]

Bridging an amp just approximately doubles its power to the connected speaker. If your Polks already get loud enough without it, then it isn't necessary.

But try both ways and see if the change is an improvement for you personal tastes.

Amplifiers are voltage sources. Bridging inverts the polarity of one amplifier and places amplifiers in series to produce a balanced output. Bridging potentially increases the amplifier voltage and power output +6dB. +3dB power increase assumes doubling the speaker impedance.

 

[TLS Guy]

Amplifiers are voltage sources. Bridging inverts the polarity of one amplifier and places amplifiers in series to produce a balanced output. Bridging potentially increases the amplifier voltage and power output +6dB. +3dB power increase assumes doubling the speaker impedance.

In most cases you will need certified 8 ohm speakers, certainly if you bridged a receiver. Most receivers will not tolerate an impedance of less then four ohms. That means you need 8 Ohm speakers for bridging a lot of amps. Few speakers actually are truly 8 ohms these days.

 

[BMXTRIX]

Your receiver allows for bridging?

I think that's the first question that popped into my head.

In fact, I think people are mostly talking out of their butts on this one.

If a receiver is designed to be bridged, which is not a feature I think I've seen, then that receiver is designed to work with speakers that have a 8 ohm nominal resistance and work properly and reliably. Otherwise, the feature would actually be stupid, stupid, stupid. But, if it is included, you better believe that they gave it some serious thought and consideration.

I've bridged some amps over the years for sure for speakers in certain locations, where I had it available and just wanted a bit more headroom for things, but mostly... no. Still, the concerns brought up only matter if you aren't using 8 ohm speakers. Just in case that hasn't been drilled into you enough yet.

The owner's manual will also state that 'when bridging, you must use 8 ohm speakers' and I've read those words at least a hundred times when going through manuals for different amps.

But, the first question I had was that if you are using the Onkyo and not a dedicated amplifier, then how are you bridging? If the AVR supports it, that's a pretty cool feature.
I did go ahead and look at the manual and it clearly does, but that is a first I've seen. It then states the obligatory:
"• Use only front speakers with an impedance of 8 ohms or higher for bridging. Failure to do so may seriously damage the AV receiver"
So... yeah.

Your speakers are rated at 8 ohms, so bridging is certainly an option, and there is nothing wrong with doing so.
Likewise, you could bi-amp things up as the speakers support it and this would keep some headroom on the receiver for dips below 8 ohms. While I don't expect any real world improvement on almost any of the setups, I do think that if the receiver and speakers give you some options, then they are worth playing with.

One of the bigger issues with bridging and bi-amping is that the receiver typically shares the power supply across all channels, so you can't draw as much power when more channels of the receiver are used. This is (typically) different from a dedicated amplifier which maintains full power to all channels at all times.

I think I would be temped to bi-amp the setup. IMO, wire is fairly cheap and I often run 14/4 to all my speaker locations so I can double up wiring, or bi-amp as I choose.

 

[Audiophile Heretic]

One of the bigger issues with bridging and bi-amping is that the receiver typically shares the power supply across all channels, so you can't draw as much power when more channels of the receiver are used. This is (typically) different from a dedicated amplifier which maintains full power to all channels at all times.

A single-ended or unbalanced amplifier has one hot speaker terminal and one zero potential or ground terminal.

Amplifier power supplies have positive rails and negative rails. A single-ended or unbalanced amplifier draws current from the positive supply rail when the waveform is positive and from the negative supply rail when the waveform is negative.

A one channel monoblock amplifier avoids more than one amplifier channel drawing current from the same power supply rail.

A bridged amplifier uses two unbalanced amplifiers to produce one balanced amplifier. Both speaker terminals are hot, but opposite polarity. A balanced amplifier draws current from both positive and negative power supply rails simultaneously. Two amplifiers are always drawing current from different rails. Repurposing surround channels for bridging does not draw current from the same rails for additional channels. The bridged amplifier voltage output is double that of one amplifier, but the current limit is the same, so the minimum load impedance is doubled.

However, passive biamplification does not increase the power to the speaker like bridging. Separate low and high frequency speaker circuits have the same impedance and draw the same current and power when driven by one amplifier or separate amplifiers. Passive biamplification divides low and high frequency speaker impedance, current, and power between separate amplifiers. Both amplifiers always produce the same full spectrum voltage output. One amplifier drives both low and high frequency speakerr circuits with the same voltage. With passive biamplifiication, both amplifiers must produce the same voltage to preserve speaker frequency balance. Neither amplifier can produce full power output with music signals. Only one amplifier can produce full power with sine waves. Separate amplifiers have independent current output and independent current limits. The power supply is not the only limit to amplifier current output.

 

[witchdoctor]

On page 15 in the manual it says you can biamp (or bridge) the front speakers with the outputs for the surround back speakers. Don't do that, use those terminals to power your surround back speakers instead. Use the Audyssey DSX guidlines to set the angles of your speakers as close as possible. If you have a narrow room this may require moving your chair/sofa forward closer to the speakers so the L and R channels are at 45 degrees. Next setup your center in front and side surround speakers at the 110 degree angles (for direct radidators) shown in the file I have attached. Once you have your 5 channel setup I would recommend setting up wides next at 60 degrees and the rear surrounds as in the diagram. Very imporatnt to have the angles as described in the setup guidelines. This will use all 9 channels on your receiver and if you want to setup the front height channels you will need to use the "preouts" on the back of the receiver to an external amp. If you need a link to an entry level model amp let me know.
As for subs, when you have budget get a second one and see Genes post on sub setup guidelines. Check out this thread for further info from Audysseys blog:

https://audyssey.zendesk.com/hc/en-us/articles/212343383-How-does-DSX-work-

 

[witchdoctor]

Can you list the rest of your speakers? Are they all Polks?

 

[HackMan55]

Can you list the rest of your speakers? Are they all Polks?

Yes, all Polk. I was getting a 40% discount for Polk products through my employer. Fronts are the s55's with the s35 center. Surrounds are s15's and rears and front heights are t15's. Subs are an hts12 and dsw440. Most content is streamed from a Nvidia Shield Pro. Just yesterday, I put in a cheap audio extractor to send audio to the Integra and video to the 65" Sony.

I know it isn't high quality gear or anything but I'm mostly happy with it other than the center channel speaker.

A customer from a church gave me a two channel amp that had quit working. I fumbled around and somehow got it going and just recently added it to the pre-outs to drive the fronts if that makes any difference.

 

[witchdoctor]

Again you are in great shape, your speakers match and you already have an additional amp. Just for a test try taking the rear T15's, place them on stands so you can get the tweeters approximately the same height as your front L-R speakers. Then place them at the 60 degree angle (+/- 10 degrees) needed for wides. See how you like audyssey dsx for movies with the wide channels engaged. Don't buy any more speakers yet, just test it out and post a reply. Remember to run audyssey calibration with the microphone again after you change your speaker setup. Thanks

 

[HackMan55]

No, thank you. I'm starting to pay closer attention to positioning now. Try to get it set good rather than good enough. I really am going to have to invest in at least a couple speaker stands. I've tried a couple different places here and there but mounted on the wall. My fiancee is a good sport but I figure it's only a matter of time until she's had enough of me drilling. My room is really tough; corner-mounted tv,, 12' ceilings and three 30"×96" windows. I think I can get things to where they need to be, but I'll have to put careful study into it.

Was adding the amp any kind of benefit over using the avr's amps? Sounds fine so far, but I haven't really pushed it much at all and haven't noticed any difference either way. I figured at the least, maybe it would help the Integra run cooler? Also, it has gain knobs for each channel. Should these be turned wide open? I guess it's just some old pa amp and I didn't find much info about it. I'm thinking maybe attention should be given to the avr's preamp voltages and the amps specs but that's just a guess.