Hi all,

My receiver (Onkyo SR702) has a single "sub out" jack.  Aperion instructions are to connect it to the Right input of the 10" subwoofer (which is labeled for 5.1 input), "or you can use a "y" plug to connect to both the left and right inputs."  Obviously not using a "y" plug is cheaper than using one, so using one must in some way be better, right?  How is it better?

Curiouser and curiouser,

Fred

Fred, the only benefit I've ever heard of by utilizing a 'y' adapter to wire both the R and L of a subs input is to ease the draw of current to the sub. Allowing the lower frequency signals to be easier to detect by the sub. The only benefit in this is a soundtrack that may not use or have any bass for a longer amount of time than the subs 'auto-off' timing is set for - helping the sub stay on, rather than powering off and then being forced to power on when receiving it's next sub frequency.

It isn't better. It is a matter that admitting to its use is a lot easier than explaining why it isn't necessary. Here is the reason why it isn't better.

The subwoofer's amplifier is a one channel amplifier. All inputs are summed into a single input before the preamplification stage. A "Y" cable causes the incoming signal to be split, thereby reducing its signal strength and making it more susceptible to RF and magnetic interference. However, if excellent quality cable is used this should have a very, very small, probably inperceptible effect. After the split, the signal has to be summed again. There may be a slight signal loss if the Y connectors are off in length, capacitance, conductance, resistance but with good connections and excellent cable, the loss is not significant and can only be measured by silicon life forms and not by carbon units...ha, ha!

The best way to get the signal from a receiver's LFE (low frequency effects) RCA output to a subwoofer's amplifier is with high end signal cable. Cable rated for digital transmission has very high standards (almost no interference whatsoever) in its shielding and makes an excellent analog subwoofer transmission line. However, when digital transmission lines get long (5+ meter) it gets expensive. The Aperion aluminum and copper shielded subwoofer cable is a quiet and  economically practical and excellent cable as long as strong RF and magnetic sources are avoided by several inches.

The receiver manufacturers know what they are doing. They have extracted the LFE and BASS information, usually through an excellent digital preamplification section, and summed it, in digital, to the LFE output before it is converted to analog at the final step.

The subwoofer amplifier manufacturers provide dual inputs in case you have an older amplifier or receiver, or an inexpensive late model receiver, that does not sum the LFE/BASS to a single RCA output.

It might occur to some sharp stereophiles: how does the RF and magnetic interference issue apply to the Aperion Towers that have a powered sub in them and have no allowance for signal cable? The answer is that with 12 guage OFC wire and the high current of a full range audio signal with bass, the wire creates its own electromagnetic environment. As long as the speaker cables are not run under a refrigerator compressor or a washer's motor or near an oil furnace's high voltage apparatus the high current that is inherent to a full range signal arrives at the speaker and subwoofer amplifier unaffected by minor background RF and electromagnetic fields.

How much can a 12 guage wire handle? About 2400 watts continuously with excellent connections. Heavy guage OFC wire is extremely important to amplifier/receiver dynamic range and the performance of the speakers. Sure 22 guage will do, but the dynamics will suck and a really powerful amplifier might actually melt the line..good!

Soooo... buy the best cable to make the connection and don't worry about the subwoofer cable being less expensive. Its not "cheap" by any means, just not rated for digital transmission over its length. But it is excellent analog cable and very, very quiet. The cable that a bass guitarist uses to get the microphone signal from the guitar to a bass amplifier is very similar in construction and that signal is much less than a receiver's LFE/BASs connector.

I realize that this is an old thread but since it has been revitalized I decided to check my S-10 Sub regarding Y connector use as input.

 

I measured SPL on axis at one meter while outputting the test tone from my AVR to the Sub.

 

Using only the right line in on the S-10 I measured 89db.

 

Using both right and left line in with a Y connector I measured 93db.

 

Obviously signal strength is increased with the Y connection and not reduced, as the post above seems to suggest without real data pertinent to the S-10. I provided actual data via measurements not speculation.

 

I agree with Jim Waters in that lower levels of bass content will be easier to detect by the Sub’s circuitry using the Y connector.

 

Jack

Jack, please try it with the "on" feature selected on the S-10 instead of "auto" and see if you get the same results. If you do, then something else in the circuitry is causing the increase in SPL on the test tone.

Perhaps the "Y" cable takes the sub out of "Dolby Pro-Logic 5.1" parameters and puts it into some generic bass parameter or perhaps its due to the place in the signal path that the preamplifier re-sums the right and left signal.

There is no switch to turn the subwoofer crossover on or off so it is logical to assume that when the right side "5.1 sub-W input" is used alone, the subwoofer crossover is by-passed by the nature of Dolby Pro-Logic II that uses the receiver's crossover and sums LFE to one output.

If the left side subwoofer line input is also used, such as when a "Y" cable is employed, perhaps it turns on the subwoofer's crossover circuit (well, something must activate it) and even if set to the same frequency as the receiver's crossover, the subwoofer's crossover circuit may add some gain to the signal. If the subwoofer's crossover is the "active" variety (I would expect it would do its work before the power amplifier rather than after-duh!), it probably has a little signal boost to it that may account for the higher SPL you measured.

A 4db increase in sound pressure is more than a doubling of the power reaching the driver (3db being a doubling of power) so this is no small amount and its cause should be uncovered.

Two things trouble me: 1) the subwoofer instructions make no mention of a problem with the "auto" sensing feature causing a reduction of transient output with low level bass signals and 2) the instructions mention a "Y" cable as being OK to use, but with no indication of any change that would occur as a result. More information would have been desireable.

I don't have the S-10 so I cannot check your findings and there is no need since I don't doubt you. My subwoofer has a switch to enable or disable the subwoofer's crossover. Your rebuttal is interesting with an unexpected result and although I concede to your findings regarding the S-10, I don't think the "straight wire with gain" has been discovered yet and I haven't quite bought into the "auto sensing circuit" that lazily slips into power-saving mode only to be abruptly stirred from its slumber with a -4db SPL yawn.  I'm sure S-10 owners would love to hear the real reason. I suspect its an "activated crossover circuit" with its own contribution to gain. Until I have an S-10, I just won't know.  :)

Hey Poppy,

I just checked my S-10 and the Auto and On selection yielded the same results.

Your post caught my attention since you appear to have some experience in the electronics field.

On the other hand if you submit unproven or not verifiable conclusions regarding specific applications or implementation of equipment, I find that misleading and a mal-service to forum readers here.

I would like to welcome you to this forum and I hope that I have not seemed harsh although sometimes my mouth and fingers get the better of me.

Jack

That's very interesting results. I think the second line (left) brings the active crossover to life. They are almost always very high grade pre-amplifiers and a good thing to have in the signal path.

Your concern about misinformation was very appropiate and I sensed it from your post. I see now that I was too specific although I had the best of intentions originally and meant no harm, but apparently there are equipment differences that I should have considered rather than just my own experience. (It was late, I was tired, etc.) Didn't even notice the date of the original submission, but its an issue I've read many times on the internet and I was just in a mood to type!

Experience is perhaps the best teacher, and in this area between a split bass signal versus a one side only LFE signal, experimentation, preferably with a sound meter, is probably the best way to go. The S-10 (which is a superb musical sub and would be my first choice) apparently benefits from an input that feeds both right and left. I love a 10" for its tight attack in difficult passages, and they can get way down too if placed carefully to take advantage of modal characteristics.

Best of regards Jack Gates, 

Poppy

Hi Poppy,

 

I don’t use a “Y” connection to my S-10 although it does increase output by 4db. My S-10 is set at about 30-35 % level with my AVR set at 0db and watching a DVD movie today the Sub actually caused the couch to vibrate.

 

I have changed some settings on my AVR that enables the S-10’s output with any source I use. I changed the front Mains from Full Band to 50 HZ.

 

It may be advantageous for some to use the “Y” connection depending on system configuration.

 

I highly recommend the S-10.

 

Jack