Secrets Q & A
- Written by Robert Ebeling & Chuck Barger
- Published on 02 December 2013
I've got a Pioneer receiver and a Polk sub along with Pioneer's Andrew Jones HT speakers. I want to place the electronics in a closet. I'm bouncing between the RedMere HDMI cables or cat6 with baluns for the TV. The sub will be 50 feet from the receiver. What are the best ways to get the signal to the sub using the LFE input?
- Don C
Answers from two on the SECRETS Team:
First, let me say you are already ahead of the game by using your sub's LFE input. This allows your sub to listen only to the receiver's crossover point and not the one that can be set on the sub itself. If you did not use the LFE input you could have significant bass degradation as having two different crossover points generally "don't play well together".
To your question about the cable . . . yes, there is a length at which (almost) any cable starts to have signal degradation from electromagnetic interference and/or radio frequency interference (EMI/RFI). This interference comes from radio waves, TV signals, wireless signals other wires in the walls, and even the individual components themselves. It is important to note that a "subwoofer cable" is any cable with RCA terminations; there is nothing particularly specific to subwoofers in "subwoofer cables" so this article could be addressing any number of different cable types. I can personally attest 100 feet of standard subwoofer cable, especially when run with other cables (speaker cables, interconnects, power cords, home wiring, etc.), is past the point where a detrimental effect on sound quality can be noticed. EMI and RFI often manifests as an undesirable "hum" or "buzz" coming from the speaker/sub. The longer the run of cable, the more interference it can pick up, and the more pronounced the effect becomes.
Some receivers have a true balanced XLR output for the subwoofer, and the subwoofer has a true balanced XLR input. In these cases, I would suggest using an XLR cable as your subwoofer cable; you may also see these cables listed as "microphone cables". Because these cables are designed to be used in either studio or stage environments (which have more cables going in every direction than you can imagine) they are constructed in such a way as to reduce EMI/RFI to the lowest threshold possible. XLR cables are not only shielded against EMI/RFI, the positive and negative conductors, referenced to ground, yield common mode rejection of RF and other electrical noise picked up by the cable.
By this point you have looked at the back of your sub and receiver and thinking, "But neither my sub nor my VSX-1121 have XLR input/output hookups." In this case, XLR cables are not an option unless you want to waste your money. XLR to RCA adapters are available, but as soon as you use such adapters on XLR cables, you lose all the higher sound quality and noise rejection advantages of the cable, since pins 1 and 3 are shorted inside the adapter, and you are subsequently just using a single-ended cable. The main source of interference pickup is in the cable itself, and as stated earlier, the longer the run, the worse the problem. The relatively small amount of unshielded cable outside the wall (and not running with multiple other cables) should not have a noticeable effect on the sound.
So, in summary, XLR cables are only effective if the source, such as a preamplifier, has true balanced outputs, and the other component to which the XLR cable is connected, such as a power amplifier, has true balanced inputs. No purpose is served by using an XLR cable with XLR to RCA adaptors, other than a situation where one component only has an XLR input or output, and the second component only has an RCA input or output. In this case, the XLR cable is used for convenience only - there will be no sound advantage. Since your situation is RCA at both ends, just place the cable carefully, by making sure it does not run in parallel with other audio cables in your system, and certainly not parallel with any power cables.
You will find my answers can be, well, unorthodox. For me, it's all about getting the most bang for the buck, much like those Pioneer speakers by Andrew Jones. So my recommendations are made to try to make it sound as good as it possibly can, without breaking the bank. One of the methods for running a subwoofer cable for any distance over 20 feet is simply quad shield RG-6. Our integration company has done it for years, with success. I do stress quad shield. While dual shield will certainly be adequate, quad shield is what is used in areas such as apartment complexes near heavy areas of radio frequency interference (RFI) and electromagnetic interference (EMI) from cell towers, TV and radio broadcasting antennas, or even interference found in a home. To terminate you can use F connectors with RCA to F adapters, or better yet, universal RCA ends from Planet Waves. I am a proponent of the "fewer connections less degradation" camp. Planet Waves also makes the digital coax cable and it is very small (3/16") in diameter making it easy to conceal. You can find a 100ft spool of their premium HD finish wire for under $100.00, and the top of the line HD RCA ends for less than $7.00 each. These also make an incredibly good and inexpensive custom digital (S/PDIF) interconnect, so buy extra ends. The design allows you to reuse the ends should it be the wrong length or not perfectly seated. A special cutter that will actually test the finished cable continuity is available for a mere $30.00 or so. If you have never heard of Planet Waves, they come from the highly respected pro A/V interconnect company D'Addario, a major player in the music scene. I believe you will be quite pleased with the end result.
A suggestion to get the best performance from your subwoofer and speaker combination, is to cut your speakers off at their lowest frequency, and match the subwoofer. Your Pioneer speakers drop down to 40Hz, so set the cutoff at 40 Hz, and your Polk subwoofer to 40-50 Hz. This will bring out the musicality as well as tightness in bass for your speakers.
As far as getting HDMI to your display, I would lean towards an HDMI extender. A little more expensive is the highly-recommended HDBaseT extender; far more stable, and it will pass IR and even RS232 for control. Atlona makes an outstanding system.
Good HDBaseT systems like the Atlona will require one CAT 5 and one power supply located at the source. I have a lot of experience with Monoprice RedMere HDMI. Sometimes their chip set causes HDMI handshake issues, the very thing they were designed to prevent. Another benefit of extenders, should Brand X not do the job, the Cat 5 is in place so you can add Brand Y at any time. Sometimes with HDMI it is a matter of trial and error.
Now about controlling the equipment remotely? That is another discussion. Good luck.