Method Sub Inputs - The Ins, Not So Much The Outs
Method Subwoofer Input Options and Usage
There are three ways to feed the audio signal you want your system to play (program) to your Method Sub and each has a reason for consideration. The three audio inputs are: SPEAKER-LEVEL, LINE-LEVEL via RCA, and LINE-LEVEL via XLR. Do not connect more than one input.
Speaker Level
Speaker level refers to an electrical audio signal that has been amplified to drive passive loudspeakers. Method Sub has an input connector (Phoenix-type, four-pin green inlet) and circuit engineered for speaker-level signal input. To use, simply plug the patch cable with the phoenix connector at the Method Sub side, and the other end to your amp via bare wire, spades, or banana plugs, whatever works best for your situation. Left hot (+) usually red, and cold (–) usually black sometimes white; then connect the right channel just like you did with the left. Speaker-level input does not draw any meaningful power from your main speaker’s amplifier, it just taps the signal and the main amp is not effected. Method Sub’s speaker-level input is electrically balance so you can safely connect any amplifier, receiver or integrated.
The advantages of using speaker-level input are many:
Input is electrically balanced and not referenced to ground which removes a point of possible hum.
Input impedance is 3.3k ohms for each channel—high enough not to draw power from the main amplifier supplying the signal, but low enough to allow long-ish interconnecting cable distances without degrading signal.
You don’t need an open set of RCA or XLR outputs, or Y-cables—connecting to your amp’s output binding posts is usually pretty easy.
Tapping signal from your main amp ensures that polarity, phase-at-frequency and main amp sound qualities are received by and thus echoed by the Method Sub. Generally, speaker-level is the easiest way to get the sound of your main speakers into the Method Sub, giving the listener a more seamless blend of the whole sound. (This assumes you are not running a high-pass filter on your main amp, the main amp needs to be outputting full bandwidth signal.)
Input of the Method Sub sums left and right signals so you aren’t missing any bass content in program material that has deep bass left/right differences.
Disadvantages of speaker-level input:
Method Sub output level can only be adjusted at the subwoofer (a few home audio preamps have a subwoofer volume trim knob, so you can more conveniently match subwoofer and main speaker levels—some songs or albums need more bass, other less, having such a knob is handy).
Method Subwoofer input signal characteristics and quality is that of the main amp feeding it, for better or worse.
Adjusting the Method Sub for room integration, personal preferences and other desired qualities requires user to make such changes within the Method Sub’s digital signal processing, which requires a PC and the free Hypex Filter Design software.
Line-Level Via RCA
Line-level refers to an electrical audio signal used to patch line-level devices such as tape decks, converters, processors, preamps…. Generally, and loosely, consumer audio line level is in the neighborhood of one volt peak-to-peak when the output is “fixed” or in the case of a preamp sending signal to an amp, when the volume knob is turned up. To use the RCA line-level input on the Method Sub, simply insert an RCA-type cable, with the other end, the source side, going into the RCA-type connect of the preamp, processor or integrated. The Method Sub sums the left and right RCA inputs. If you are using an RCA feed that does not filter at the preamp or processor side, you will get best results connecting left and right on both ends. Output connectors marked SUB-OUT are almost always filtered so all but the bass is already filtered out. SUB-OUT outputs are also almost always left/right summed so you only need to connect a single RCA-type cable to the Method Sub, left or right, it doesn’t matter. Outputs on the preamp, receiver or controller marked PRE-OUT are typically unfiltered and signal is attenuated by the main volume knob. Outputs marked FIXED are at line-level full signal strength, and not effected but the volume knob. FIXED outputs are what you use when you want to record the program material, not what you use to feed your subwoofer.
Advantages of line-level RCA input are:
If you have unused RCA outputs, well, that’s even easier than connecting to your amp via speaker-level.
The RCA inputs on the Hypex amp used in Method Sub sound great and have reduced chance of hum compared to other subs and their RCA inputs.
If you have been chasing the audio dragon for a while, you likely already have some longer RCA cables to use.
Sometimes the pre-filtered SUB-OUT sounds good, and you might also have ability to shape the filter in an already known user interface.
Disadvantages of line-level RCA inputs are:
Chance of hum due to a ground loop. RCA connectors are typically referenced to ground. In the case of the Hypex Fusion amp there is a reduced chance of hum as the circuit puts the RCA input ground 100 ohms above speaker-level ground, and on an internal technical ground.
You might have a less seamless sonic matchup between main speakers and subwoofer compared to speaker-level as you aren’t referencing the electrical signal characteristics of the speaker-level feed.
Line Level Via XLR
As used in Method Sub, and generally true for most a home audio subwoofer application, there is little difference in usage between RCA and XLR, thought they are not the same. If you have an XLR line-level output free on your preamp/processor, you are less likely to have a hum issue compared to the RCA input. And you are likely able to run extremely long runs of XLR cable without causing any signal issues. Outside of these points RCA and XLR inputs are not all that different in practice for home audio subwoofer integration. The pros and cons mentioned on the RCA also apply to the XLR, save the one about hum.
In consumer audio gear XLR-type connections and lines are used similarly to RCA, but where RCA is a single-ended electrical signal type, XLR is typically balanced, or should be. Balanced lines do not need a ground reference as they are balanced and create their own virtual ground. The XLR input on the Method Sub does reference the speaker output’s negative left and negative right to pin-1.
So yeah, pick what works for you. But if you don’t know, and prefer one-and-done with less knobbing about, less fiddling with your sound, go with speaker-level input and get back to reading album liner notes and dancing with your music.