PLEASE, PLEASE, PLEASE Give my subwoofer Balanced XLR connections

[b_panther_g]

I would love to see XLR input connections become the standard on all subwoofers. I’d also love to see XLR outputs become the standard LFE/subwoofer output for receivers or pre/pros. Here’s why…

More placement options. I’d love to place my sub(s) on the back wall (i.e. the wall behind my couch). But I don’t like the idea of running a standard RCA connection for over 25 ft. Even with the best shielding, there will still be a lot of signal loss. If there were an XLR subwoofer output on my receiver and an XLR input on my sub, the signal loss would be minimized.

Most people have active or powered subs. Since the amp is built into the sub, there would be no need to get a special amp that accepts balanced XLR inputs IF balanced connections were the standard for subs.

Also, it won’t cost much. All the manufactures would need to do is add 2 balanced XLR connections. That’s 1 XLR output on the receiver and 1 input on the subwoofer. How expensive could it be?

Bottom line…Of all the speakers in a home theater, subwoofers have the most flexible placement options. Why should the user have to suffer signal loss for longer cable runs? Balanced XLR connections on the LFE channel and on the subwoofer would give the user even greater placement options because they won't have to worry about signal loss.

That's my opinion. Please tell me your opinion. How would you feel about XLR connections being standard for subs? Do you think they are the best choice for longer runs or are they unnecessary?

Thanks for your input.

Later,
B

 

[mtrycrafts]

More placement options. I’d love to place my sub(s) on the back wall (i.e. the wall behind my couch). But I don’t like the idea of running a standard RCA connection for over 25 ft. Even with the best shielding, there will still be a lot of signal loss.

Why would there be so much loss? Interconnects rely on voltage signals, not current. Interconnect signals have very small current transfers.

If there were an XLR subwoofer output on my receiver and an XLR input on my sub, the signal loss would be minimized.

Get a better cable with larger center conductor.


Also, it won’t cost much.

Buy an RG6 type video cable used for TV.



Of all the speakers in a home theater, subwoofers have the most flexible placement options.

Mostly corners

Why should the user have to suffer signal loss for longer cable runs?

I think you worry over a non issue.

 

[b_panther_g]

Why would there be so much loss?

Because, when dealing with long cable runs (i.e. runs greater than ~10 ft.), the shielding used in an unbalanced cable is not as affective as the common mode rejection technique used by balanced connections. There will be more noise introduced to the signal if an unbalanced connection is used vs. a balanced connection.



Get a better cable with larger center conductor.

In an unbalanced connection, once the noise makes it past the shield there is no way to remove it from the conductor. I don’t see how a larger conductor would help eliminate the added noise. Could you please explain this further? Thanks.



Mostly corners

That’s true - if you like to place your sub in the corners. I don’t like to place my sub in the corners. I’ve read (I’m try to remember where) that placing the sub in the corners is good if you want to excite all room nodes evenly. But to here the benefits you’d have to sit in the opposite corner of the room. That’s not for me.

I like to place my subs in the center of the front wall. Then I use a PEQ to get the smoothest response. I also like to place the sub as close to the listening position as possible. That’s why I want to move at least one sub to the back wall.



I think you worry over a non issue.

Maybe…



Now that I’ve reread my post, I see that I could have been clearer. I agree with you that signal loss MAY not be that much of an issue. I guess what I should have said is signal degradation instead of signal loss.

An unbalanced connection allows more noise to enter the signal than a balanced connection. The added noise degrades the signal.

To give you some perspective, I live in a city. I also live within a few miles of a cell tower. There’s a lot of noise around here that I don’t want getting into my system (although I don’t think I’m that much worse off than most city dwellers). Anyway, that (the noise entering the signal) was what prompted me to write my original post.

Sorry if it caused any confusion.

Later,
B

 

[Rob Babcock]

Balanced inputs/outputs are sometimes seen on more expensive gear, but I doubt you'll ever see it much on the cheaper consumer stuff. Mfg'rs tend to only include features that help a product sell (ie what the consumer thinks they want vs what the mfg'r thinks they need). An audio engineer who frequents another board (I won't say who, but you'd recognize his name) claims that some cheaper gear with XLRs don't really have balanced outputs, but basically make the claim. I dunno if it's true or not...

At any rate, a trihedral corner will create the most bass reinforcement, but not necessarily the most even bass. While that's where most people (including a lot of experts) plunk down their sub, Russ Herschellman often advises in his articles that it's not the best place for one. A recent paper by Floyd Toole advocates multiple subs pulled out from the corners into the room. He says imagine virtual walls of a room 1/3 smaller than the actually room, then place 4 subs in those 'virtual corners.' His research indicates that's a near optimum placement in most rooms.

The corner can be a good location, especially if you need the extra room gain. You can site them in a corner, do a little testing/tweaking placement, then use parametric eq to even things out. That works pretty well, assuming you don't boost, only cut.

 

[b_panther_g]

You’re right, Rob B. Balanced connections are usually found on Hi-End gear, but the price/performance ratio of most hi-end gear (or more specifically Hi-$$$ gear) really doesn’t make much sense to me.

But, depending on what others think, we could make some noise and let manufactures know that we want true balanced connections for our subs. I suspect that manufactures (or their reps) at least read these forums. They pay to advertise here don’t they. Or we could ask the Audioholics Team to write something about it.

IMHO it makes sense to have a balanced subwoofer connection. Unlike other HT speakers the sub could go many places. Also it’s usually an active speaker – so the benefits of the balanced connection really have on opportunity to be heard.

I’d really like to know what other forum members have to say about it. Maybe we could come to some sort of consensus.

Thanks.

Later,
B

 

[djoxygen]

Some of the haunters of these hallowed boards already know that I'm a big proponent of balanced interconnects, so I have pre-seconded your request to the manufacturers. I am slowly working toward a system where all the external audio connections are either digital or balanced. It is sadly rumoured and probably true that some XLR connections are not truly balanced, but any company that has its roots in the pro audio world won't be fooling you (Lexicon, Mackie, Sunfire (other criticisms aside) for example).

If you already have a non-balanced receiver and want to put your sub more than a few feet away, I still believe that a balanced cable run would be beneficial. A relatively inexpensive way to do this is to use a .5 meter RCA cable to run from receiver to a transformer like the Aphex AX124A (~$200), which uses active electronics to turn your -10 unbalanced signal into a true +4 balanced one. Then run your XLR as long as you like.

If you haven't yet purchased your sub, check out the Mackie HR-series or the Genelec 1092. Both are good enough for pro audio ears, so they ought to turn your XLR goodness into pressure waves that will shake your booty accordingly.

 

[moverton]

Sonance sells a balanced/unbalanced converter set. LS1 and LR1. The sender (LS1) converts from unbalanced to balanced, you run the long run, then hook back to the LR1 right before going into the sub (or active speaker). I think they are about $80 each.

http://www.sonance.com/subs/products.php?category_id=36&option=get_category&thread_one_cat_id=29&thread_one_cat_name=Electronics&thread_two_cat_id=&thread_two_cat_name=

Some of the haunters of these hallowed boards already know that I'm a big proponent of balanced interconnects, so I have pre-seconded your request to the manufacturers. I am slowly working toward a system where all the external audio connections are either digital or balanced. It is sadly rumoured and probably true that some XLR connections are not truly balanced, but any company that has its roots in the pro audio world won't be fooling you (Lexicon, Mackie, Sunfire (other criticisms aside) for example).

If you already have a non-balanced receiver and want to put your sub more than a few feet away, I still believe that a balanced cable run would be beneficial. A relatively inexpensive way to do this is to use a .5 meter RCA cable to run from receiver to a transformer like the Aphex AX124A (~$200), which uses active electronics to turn your -10 unbalanced signal into a true +4 balanced one. Then run your XLR as long as you like.

If you haven't yet purchased your sub, check out the Mackie HR-series or the Genelec 1092. Both are good enough for pro audio ears, so they ought to turn your XLR goodness into pressure waves that will shake your booty accordingly.

 

[Rob Babcock]

I agree with you, BPG. I just don't know if there's enough of us to influence the marketing guys.

 

[b_panther_g]

Thanks for the responses so far. I didn’t know about those devices that convert an unbalanced signal to a true balanced signal. Again thanks.

Rob. You may be right, unfortunately. There may not be enough interest in balanced connections to get the manufactures’ attention. I guess all anyone could do is buy the “Hi-End” stuff or hope for a trickle down affect. Oh well.

Later,
B

 

[plhart]

Guys-

We're talking about very low frequency information run at low voltage levels over long distances. I use RG-6 or RG-59, whatever I have laying around because the signal gets there with theoretically Less chance of attenuation than speaker wire. Gene can do the calculation but it works out to a ridiculous calculation, something like -1dB attenuation at 20KHz running a voltage signal over 28 gauge coax for a 100 feet (I'm doing this from a rather foggy memory of this supposed "dilema").

The concern running coax to a rear sub (which I do) is that 60Hz hum may be introduced into the system as a ground loop. To solve this I usually just make sure the coax shield "return" is not connected through to the case of the RCA going into the rear sub.

Re: placing subs. Read Todd Welti's piece on harman.com. The bottom line with a high performance subwoofing system is that two subs work better than one, three work better than two and four work best of all. Corner placement gives you a theoretical +9dB gain, floor-wall placement gives you +6dB, floor placement gives you +3dB. What you are trying to achieve is the highest free SPL level possible because of the human ear's horrible insensitivity to low frequencies (see the Fletcher Munson curves). The balanced-bass ideal that we're trying to achieve is the real problem in a room because 90% of rooms will have a strong bass peak somewhere in the 20Hz to 100Hz range.

If you shrink yourself down and stand on a frequency response curve at 200Hz and look down the scale toward the 20Hz to 100Hz range wherever that peak can be seen (say at 80Hz) becomes a fence and you will not be able to clearly hear well the frequencies below that 80Hz. You'll hear the one-note bass at 80Hz.

This is where you've got basically two options. You start moving one woofer at a time around the front of the room (with the others off) until you get the smoothest bass response at your listening position using a test tone CD and point-by-point graphing. Then you do the same with the second sub at the rear of the room with the first sub off; you must graph this out using a test CD! Your ear is Way too insensitive to do it by ear. Finally you turn both subs on and re-adjust the levels of each woofer listening to movies and music. This is where psychoacoustics takes over because you want to hear the bass from the front where the music is most of the time.

I'll cover more later. Just know that the other way to do this is and be able to place the subs pretty much where you want them (except for a null!) front and rear is if you have a single band parametric EQ cabable of a Minimum of 1/12 octave resolution. This includes outboard devices like the SOS or onboard setups like those found in some Velodynes, Infinity RABOS, AV123 or the just introduced JL Audio home subs.

Bottom line on the corner vs sidewall placement is that corners produce the most stong standing waves so that makes them technically most efficient couplers to the room. But that also means that corner placement will produce the highest dB standing wave so it's real helpful to have some 1/12 octave or better device to attentuate it. More detail in articles forthcoming...

 

[b_panther_g]

Plhart,

If I’m not mistaken, you’re saying that the .1 channel signal loss of an unbalanced connection is not an issue as long as shielded RG-6 cable is used – correct?

If so, that’s great news. Then I don’t have to worry about the placement of my subs or balanced connections.

For a PEQ I like the Behringer Feedback Destroyer. It’s essentially 2 PEQs in 1. That’s a 12 band PEQ (with independent settings) for 2 subs. Plus it’s only about $100 online. It works for me.

Later,
B

 

[djoxygen]

If I’m not mistaken, you’re saying that the .1 channel signal loss of an unbalanced connection is not an issue as long as shielded RG-6 cable is used – correct?

As you yourself clarified, panther, the primary issue isn't signal loss, it's outside interference which will be manifested as unwanted noise at the sub. Any wire has the potential to become a giant antenna. Properly shielded and grounded cabling will usually reduce that effect to a reasonable level, especially over a short distance.

The concern running coax to a rear sub (which I do) is that 60Hz hum may be introduced into the system as a ground loop.

*A* concern, sure, but *the* concern? Ground loops can be a bear to isolate and resolve in complex systems, but when the only things involved are the receiver and the sub that may or may not be humming, there aren't too many grounds to lift. I think panther's primary concern is (rightly) outside interference acquired over the long, unbalanced cable run to the desired sub placement, and a balanced cable run will, if all other issues are properly addressed, help mitigate that potential problem.

 

[b_panther_g]

I knew it was too good to be true.

So regardless of what cable I use for the unbalanced connection, the balanced will still have less noise or signal degradation. Oh well, back to square 1.

I just noticed that the subs at AV123.com have XLR inputs. Does anyone know how they sound? Are they a true balanced connection or just an XLR jack?

Thanks,
B

 

[happy540i]

M&K pro have XLR connections. I have 2 MPS 5310 and they have both an XLR and RCA connections.

 

[Francious70]

You do know that XLR cables arn't the only balanced connection right?? RCA's can be balanced too. Check your manual for you reciever, it may already send out a balanced signal. If not, you can buy a line driver to step up the voltage and a balanced/unbalanced converter.

Reciever>line driver>Cable run>converter>amp

Paul

 

[markw]

Let's keep this in perspective, shall we?

I use balanced cables and XLR connectors. In fact, I swear by them. There's no way I could get those microvolt microphone signals 75' to the mixing console at the church w/o noise.

But a subwoofer signal is a different creature. It's a "line level" signal, which generally is anywhere from one to several volts. It doesn't go through the gain stages that a microphone signal needs. So, unless EMI is a major issue in your environment, it's my opinion that all this worrying about not having balancd input accomploshes nothing except adding worry and strife.

IOW, You are worrying about a non-issue. If EMI were strong enough to impinge on a line level signal and adversley affect it, you would already know it by it's having manifested itelf with other equipment in your system. A coaxial cable with a decent shield should be more than adequate for most home situations.

Now, if we're talking microphone feeds, that's a different story.

 

[b_panther_g]

“M&K pro have XLR connections.”

Yes but that’s more subwoofer than I’m looking for at this time. Also that’s only ½ of the equation. I’d also like to see balanced outputs on more receivers and pre/pros.



“RCA's can be balanced too.”

I didn’t know that. I know of balanced XLRs and balanced tip-ring-sleeve connections but not balanced RCAs. Could you please point me to a web page that has more info about it? I’d like to learn more. Thanks.


“It doesn't go through the gain stages that a microphone signal needs.”

I don’t know much about pro recording or microphone gain stages. Could you explain how they are different from amplifying a line level signal?



Thanks for the input.

Later,
B

 

[markw]

“It doesn't go through the gain stages that a microphone signal needs.”

I don’t know much about pro recording or microphone gain stages. Could you explain how they are different from amplifying a line level signal?

The lower a signal is, the more stages of gain it needs to go through before it's usable to a speaker. The more amplification stages a signal goes through, the more any noise is amplified along with the signal. In the case of a microphone, it's possible that the noise could possibly be just about as strong as the signal itself.

If a signal is very low, any noise that is picked up will be proportiontly more of a problem than that same noise would be with a more powerful signal.

Look at it as if you have a magnetic phono cartridge, which is actually a stronger signal than a microphone but can serve as an example.

It puts out a very small microvolt range signal, travels through a few short wires and then the first thing it sees is a "phono preamp" which, along with some RIAA FR massaging, goes through a major, major gain stage. This brings the signal up to a "line level" signal which can be used by a line stage preamp and even some power amps, if it has enough gain. These "line level" signals can traverse fairly long distances without degradation, particularly when talking home audio.

Most Hi fi units used to have these but as of late, these seem to be disapearing and fall into the realm of aftermarket products.

So, in essense what I'm saying is that while there may be a problem with noise pickup when starting with low, low level signals and going through major gain stages, if the signal is strong enough, and the shielding is strong enough, it can become an audio non issue, except as a source of worry and argument.

 

[djoxygen]

You do know that XLR cables arn't the only balanced connection right?? RCA's can be balanced too. Check your manual for you reciever, it may already send out a balanced signal. If not, you can buy a line driver to step up the voltage and a balanced/unbalanced converter.

I don't want to say such a beast doesn't exist, but in 15 years of travels in pro and consumer audio I've never encountered an RCA connector that claimed to be balanced. By definition it couldn't be because the definition of a balanced connection is positive, negative, and ground/neutral - requiring 3 conductors which an RCA jack simply doesn't have.

I guess that you could stretch the definition a little, though. Let's assume a zero voltage neutral/ground by using the chassis of the gear rather than the cable's ground. Then you'd be probably using the shield/ground of the cable as the negative. Since the shield is specifically designed to attract outside interference and keep it away from the positive in the central conductor, you'd be treating all that noise as a valid part of the signal when it reached its destination (whether that destination is a tranformer to make it a true balanced signal, or it's a subwoofer on the other side of the room).

So while it would be possible, I really don't think it would be a wise choice.

 

[djoxygen]

But a subwoofer signal is a different creature. It's a "line level" signal, which generally is anywhere from one to several volts. It doesn't go through the gain stages that a microphone signal needs. So, unless EMI is a major issue in your environment, it's my opinion that all this worrying about not having balancd input accomploshes nothing except adding worry and strife.

IOW, You are worrying about a non-issue. If EMI were strong enough to impinge on a line level signal and adversley affect it, you would already know it by it's having manifested itelf with other equipment in your system. A coaxial cable with a decent shield should be more than adequate for most home situations.

It *could* be a non-issue, but panther did say that he was in a high-interference environment. If, for the sake of argument, we say that the rest of his (unbalanced) interconnects are 1 meter and the run to his sub is going to be 10 meters (not unreasonable if he runs the cable around the perimeter of the room), then he's got 10x the potential antenna in his cabling. It's possible that he doesn't even have analog audio interconnects at all, so he wouldn't have any audible interference already apparent in the system.

When I was in college in Boston's Back Bay area, I could pick up WBCN on my Sony MDR-V6 headphones as clear as day, and without the added expense of any kind of radio tuner. A headphone cable's signal level is much closer to line than mic. It's not a stretch that panther and others could face similar challenges. Only they can make that decision. In no (properly wired) case will an unbalanced connection pick up less noise than a balanced one, but whether or not the listener can hear the difference...