What is the benefit of bi-wiring?

shaneybrainy

I am a little new to complex audio setups and was wondering what the benefit of bi-wiring was or if their is any benefit at all. I also have questions about what the phase switch on the back of the Polk PSW-10 Subwoofer does, and could someone please explain lowpass to me?

quadzilla

A lot of people will say there's none. Others will argue with that. Really, you have to try it and see if you can tell any benefit over a good pair of jumpers.

Drenis

quadzilla wrote: »

a good pair of jumpers.

Even that's better then stock plates. Experiment OP.

shaneybrainy

Would Banana plugs increase the sound quality of my setup?

bobsauto49

No! Bare wire is always best,and banana and spades are for convienence!

F1nut

Would Banana plugs increase the sound quality of my setup?

If you mean by simply adding banana plugs that the sound quality will suddenly become better, then the answer is no. If you mean by adding them to replace oxidized bare wire, then the answer is yes.

Bare wire is not best as exposed copper slowly oxidizes its way into causing transmission issues. Soldered connections to bananas or spades are the way to go.

pyrocyborg

shaneybrainy wrote: »

I am a little new to complex audio setups and was wondering what the benefit of bi-wiring was or if their is any benefit at all. I also have questions about what the phase switch on the back of the Polk PSW-10 Subwoofer does, and could someone please explain lowpass to me?

I also think that you might try to experiment by replacing your stock jumpers with "homemade" ones made off large quality cables (you can search on google about this "replace speakers jumpers with cable" for a tutorial). If you can hear a difference, it might be worth it to bi-wire. I might get flammed for this (as there is a lot of conflicting information and opinions about wires and cables), but I'll give my opinion from my personal experience: I never heard a difference from bi-wiring from multiples systems, nor did I heard a difference with new jumpers. In my opinion, new jumpers are useful if your jumpers are old or stained, but not that so if they're brand new. It's like replacing an old oxidized wire with a new one.

As for you second question, the phase switch depends on your room bass dynamics and your other speakers themselves. This switch is here to help you obtain the best bass output, depending on your needs and preferences. Generally, you can either use the switch at the back of your sub, or the "phase" setting on your receiver: it does the exact same thing. To configure it, you should sit at your preferred spot and play a song you know which have some bass. Switch back and forth between those 2 settings (normal or reverse; or 0 or 180) and choose whatever which one you prefer. The bass should blend better, not be boomy and be "in phase" with the front speakers. With the other setting, the bass should be partially cancelled by the speakers as this is what happens when speakers and sub are out of phase. So generally speaking, the setting with the most bass is the best, but it might not suit your tastes.

The lowpass filter (if that's what your talking about) is there to send only certain frequencies to the subwoofer. A subwoofer can reproduce frequencies between 20 and 120 Hz, depending on the model and driver size. The first recommended setting would be to set it at 80 Hz, as frequencies higher than this become directional (i.e. you can hear where they come from, which you don't want from a subwoofer). Under 80 Hz, frequencies does not seem to come from your sub, but from your speakers. You should set both the knob at the rear of your sub and your receiver lowpass setting at 80 Hz.

There again, you gotta do something do get the best out of your system: you must set your speakers size to SMALL (not LARGE), even if they are towers as your subwoofer is now doing the lowest frequencies. This way, your speakers will concentrate on doing every frequencies over 80 Hz (as you actually set your crossover at this point... if you set it at 60Hz, your sub will do 60Hz and lower while your speaker will reproduce 60 Hz and more... but 80 Hz is a good start for bookshelf speakers, while 60Hz might be good for large towers).

If you do not set your speakers to SMALL, you could have an effect called double-bass, which is basically too much bass during movies. While it can sound great for music, it isn't that good for movies IMO... it's not as good as putting 2 subs for example. It is better to let speakers do what they do best : higher frequencies, and let subwoofer do the lowest. Otherwise, you send a lot of power to your speakers so they can reproduce bass, and there is less power to make every other frequencies, which is a waste as your sub are already making the bass.

kuntasensei

pyrocyborg wrote: »

The lowpass filter (if that's what your talking about) is there to send only certain frequencies to the subwoofer. A subwoofer can reproduce frequencies between 20 and 120 Hz, depending on the model and driver size. The first recommended setting would be to set it at 80 Hz, as frequencies higher than this become directional (i.e. you can hear where they come from, which you don't want from a subwoofer). Under 80 Hz, frequencies does not seem to come from your sub, but from your speakers. You should set both the knob at the rear of your sub and your receiver lowpass setting at 80 Hz.

I respectfully disagree with this practice, despite the fact that I have seen this advice given to people for a long time now. If you're using the crossovers on the AVR, the lowpass dial on the subwoofer itself should always be turned to its maximum setting so that you don't cascade the filters. Additionally, if your receiver has a "lowpass of LFE" setting, the only correct setting for this is 120Hz, as the LFE channel is brickwall filtered by design at 120Hz.

I agree that bass above 80Hz is generally considered directional, which is why the crossovers for the individual speakers should be set to 80Hz or lower if at all possible. The lowpass filter of LFE, however, only exists to maintain compatibility with older THX-spec'd subwoofers and should not be used unless you are using one of those old subs. The audio mixers rarely put any significant content above 80Hz in the LFE channel anyway, however, there are harmonics above 80Hz in the LFE channel that can give deep bass its perceived tone and you are MEANT to hear that (and they aren't directional because the significant energy is below 80Hz). Setting a lowpass filter on the LFE channel to anything below 120Hz throws away those harmonics completely, as they are not redirected to the other channels in that case. IMPORTANT NOTE: LPF of LFE does not affect the sound redirected to the subwoofer from the other channels via bass management - ONLY THE LFE CHANNEL OF A DIGITAL SOUNDTRACK.

It's also important to recognize that crossovers are not a sudden change from speaker to subwoofer, but a gradual transition using two filters - a highpass and a lowpass. (For more info on this specific application, see Linkwitz-Riley filter.) This is why you don't want to use the lowpass on the sub AT ALL if you're handling the crossovers on the AVR itself. Crossovers on digital receivers are designed to mimic the behavior of analog Linkwitz-Riley filters.

Let's say you have your speakers set to an 80Hz crossover on your receiver. In this case, 80Hz is the point where both your speaker and your subwoofer are reproducing the sound in roughly equal amounts. If you then set a lowpass filter of 80Hz on the subwoofer itself, you are attenuating the bass to the subwoofer further below 80Hz and essentially destroying the smooth transition from speaker to sub. In this example, you're cascading two lowpass filters, which is a no-no. Setting a crossover on your receiver ALREADY lowpass filters the sound going to the subwoofer from that channel, which is why the lowpass on the sub itself is unnecessary (and creates a gap in frequency response if used on top of your system crossovers).

An additional consideration is that analog lowpass filters on the subwoofer itself can change the delay characteristics of the signal, whereas digital filters on the AVR are designed to maintain proper phase/delay across the transition. Turning the lowpass on the sub to its maximum (or preferably bypassing it altogether) is the best way to avoid this issue, which can cause the proper distance/delay setting for the sub to be different than its actual physical distance from your main listening position. If you're using an auto-equalization routine such as Audyssey or MCACC, this delay in the signal is taken into account because the mic picks up on the delay when doing its measurements. However, if you're calibrating yourself, the correct setting to maintain the phase relationship across the transition can often differ by a half-foot to a foot distance/delay if you're using the lowpass on the sub.

In summary: Turn the lowpass on the sub all the way up or connect to a LFE input that bypasses the lowpass filter if your sub has one. Set LPF of LFE on the receiver to 120Hz. Set your system crossovers on the AVR to 80Hz or lower if at all possible to avoid sending directional bass to the subwoofer.

pyrocyborg

We continue to learn everyday! Thanks sensai :cheesygrin:

Mon40CSMM10

The only advantages I had with bi-wiring (in my case Monitor 40's) was a slight detectable high end increase and also that my receiver did run slightly cooler than with single wiring and leaving the brass jumpers on.

Now that I've switched to 3-way speakers for the front mains--but they also have legacy spring clips rather then the newer 5-way binding posts--bi-wiring is not even an issue because it's not supported.

But I've also learned something. The home theater recommendation of 80 Hz is just that--a recommendation for home theater. For music, I've learned that--to my ears--any frequency gap is not really audible, so then set the crossover to the lowest value that does not meet or exceed the lowest frequency response of the speaker. Still set the speakers to small, but then do this: 40 Hz is the lowest the speaker can go? Set crossover to 50 Hz. 60 Hz is the lowest? 50 Hz is too low so set to 80 Hz (same goes for 60 and 70 Hz); 80 Hz is the lowest, well, then crossover at 80 Hz would be at the lower bound of the speaker frequency response so then crossover at 100 Hz. (And so on). This is done with the receiver crossover, not the subwoofer low pass dial--that one goes all the way to LFE when using subwoofer out from the receiver into the LFE input of the subwoofer.

kuntasensei

Mon40CSMM10 wrote: »

But I've also learned something. The home theater recommendation of 80 Hz is just that--a recommendation for home theater. For music, I've learned that--to my ears--any frequency gap is not really audible, so then set the crossover to the lowest value that does not meet or exceed the lowest frequency response of the speaker. Still set the speakers to small, but then do this: 40 Hz is the lowest the speaker can go? Set crossover to 50 Hz. 60 Hz is the lowest? 50 Hz is too low so set to 80 Hz (same goes for 60 and 70 Hz); 80 Hz is the lowest, well, then crossover at 80 Hz would be at the lower bound of the speaker frequency response so then crossover at 100 Hz. (And so on). This is done with the receiver crossover, not the subwoofer low pass dial--that one goes all the way to LFE when using subwoofer out from the receiver into the LFE input of the subwoofer.

One of the big reasons the 80Hz guideline exists (other than the research that says that's where most people lose bass directionality) is that it frees up headroom on your receiver's amp section to use for transient bursts of sound, making the entire system sound cleaner. The amp in your subwoofer is typically better for reproducing bass, arguably because the damping factor (the ability to stop a driver from moving after a sound has stopped playing) of sub amps is usually higher than the very minimal damping factor used in AVRs (which is typically around 60, vs. >200 for sub amps and external amplification). Because of this, you can often get tighter, more controlled bass by leaving your crossovers set near 80Hz even if your speakers are solid down to around 40Hz. This is also important because the power ratings of AVRs are almost never as advertised with all channels driven, which is more important for home theater than music listening.

Because of the crossover slopes used in most systems, my general rule of thumb is to give the speaker a half-octave transition before the speaker's -3dB point. Basically, take the -3dB point and multiply it x 1.5. Therefore, if your speaker goes down to 40Hz per the anechoic spec, 60Hz is a safe starting point for a smooth transition from speaker to sub without a gap in response. That said, you CAN often go lower than this because the anechoic specs of a speaker don't represent a speaker's true in-room performance, which is typically 5-10Hz below the anechoic spec. So your recommendation of setting it 10Hz above the -3dB point will usually work out well.

However, as I said, you have to balance the power needs of the speaker based on the amp section of your AVR and the amp of your subwoofer. If you're using external amplification (which I just recently added for my front three channels, and I can't recommend it enough), you can get the same tight bass you would get from a good sub amp from the speaker itself, because you're now using an amp with a better damping factor (among other things). It's all about finding the sweet spot for your particular system. If you're using crossovers below 80Hz while running all your speakers off your AVR and you notice harshness when listening at high levels, try giving the receiver more breathing room by bumping the crossovers up a notch.

Here's the thing I want to stress most: All of the above is why you often see people here recommend a solid subwoofer as one of the most noticeable upgrades you can make to your system. Entry level subs get your foot in the door... but once you add a subwoofer that can troll down near 20Hz and remain tightly controlled in the process, the effect it has on the sound of ALL your speakers will breathe all new life into your home theater. It not only gives you the visceral subsonic bass that you feel in the movie theater, it also improves the sound of bass from your other channels and, when carefully dialed in for the smoothest transition, can give your AVR more headroom to cleanly reproduce highs and mids (where the effect of damping factor is negligible).