REL Sub High Level Connection Question

Looking at a REL S/2 subwoofer at my dealer yesterday. It was advised to use the high level Neutrik Speakon cable connected directly to the amplifier speaker terminals. I have a two channel amplifier with one pair of speaker terminals.
I asked if you connect the main speakers to the same terminals as the subwoofer cables in a parallel connection and this was told that it was OK to do this.
It just seems kind of odd to connect the subwoofer and main speakers to the same terminals on the amplifier.
The subwoofer manual does not mention this at all. It says to connect the subwoofer cable to the speaker terminals but does not mention anything about the main speakers.
I assume it is OK to connect in parallel, I mean how else are yo going to send a signal to the main speakers, but why doesn't the manual say this?

 

I had a REL sub and did connect the sub to the same binding posts as the main speakers. It worked perfect for me as I used banana plugs on the speaker cables and spades on the REL connector.

 

REL is great for music. I believe this type of connection is the best for integrating the main speakers with the sub. Just follow the instructions.

 

Seems odd but works great. The wording of the manual assumes that your speakers are already connected, so is actually saying to connect the sub cable to the same output.

 

Word to the wise...be VERY careful that your amp is NOT a balanced design!!
REL uses a balanced amp for their internal amp on their subs, this amp cannot be connected by the Speakon connector to a external balanced amp output.
It will damage both the amp and the subwoofer if you connect the sub without the proper grounding protocol. Best to talk to the dealer if you suspect
that the amp may be balanced. Don't ask me how I know this...

 

I do not understand what you mean by a "balanced amp output"? Please give us more detail. All of the amps I have ever seen have plus (+) and minus (-) terminals that the speaker cables are connected to, weather or not the amp itself is a balanced design. I use several REL subwoofers in my two systems. The high level Speakon connection works on the principle that because the REL internal amp has very high input impedance that it draws almost no current (and thus no power) from you amp that drives your speakers. The input impedance of your speakers is typically 4 to 8 ohms and the input impedance of the REL amp is around 10K ohms. Since the REL amp and speakers are connected in parallel to the main amp a simple application of Ohm's Law and Kirkhoff's Law tells us that the ratio of the current to each is the inverse of the ratio of the input impedance of each. Thus, current to REL amp divided by current to speakers is equal to speaker input impedance divided by REL amp input impedance. Let's say the speaker input impedance is 5 ohms (to make the math easy) then the current to the REL amp is 1/2000 of the current to the speakers. Since the voltage to each is the same this says that the power from the main amp to the REL amp is 1/2000 of the power from the main amp to the speakers. This technique is referred to as "the REL amp is riding the gain or following the voltage of the main amp".

Now, there is a way to screw this up and damage either your amp or your speakers (as I unfortunately learned). In my main audio system I use monoblock power amps and have two small REL T1 subwoofers (these are no longer in the REL product line) to make a 2.2 system. The easiest way to make the actual connection to the REL's if you have true five way binding post on the main amp and the main speaker cables use spade connectors (the best connector for high current applications) is to connect banana connectors to the loose ends of the cable that goes to the Speakon connector and because of the monoblock amps the two positive wires on the REL cable are twisted together so you end up with one positive and one negative banana connector that go to the monoblock amp. Since these are banana connectors you simply slide them into the hole in the back of five way binding post on the monoblock. Well, if you are bending over and looking at the amp upside down in a poorly lighted area it is possible to accidentally confuse the polarity of the banana plugs and plug the positive banana into the negative binding post and the other way around for the second banana connector. This will cause a power surge from your amp when you turn it on and it damaged a tweeter in my main system (which I had to replace at significant cost).

 

Davey, I looked at your profile, I assume the problem you had with the REL sub was with your Rowland Model 8 amp. I see that it has two sets of speaker binding post for each channel. I must say that is a new for me.

 

Thanks to all responses.
The manual should have at least mentioned and illustrated the connections of the main speakers in parallel with the subwoofer cable. The connections for the sub to the terminals were clearly illustrated but the main speaker wires were not shown or accounted for.

This is an excerpt from the JL Audio D110 manual, for example-

"To use the “Speaker Level” inputs feature, simply connect the full-range speaker outputs of your receiver or integrated amplifier to the “Speaker Level” plug of the Dominion™, in parallel with the main speakers. In this application, the main speakers will remain full-range and their sound will not be affected by the connection to the Dominion™"

BTW I heard the JL Audio D110 and it sounds incredible. Adds lots of deep, fast musical bass to the sound- even if the main speakers do not go very low. The dealer had it paired with the KEF R100, the BOTL of the R-series with 5-1/2" woofer and the sound was completely seamless and had tons of bass response.

 

The speaker-level inputs on subwoofers have such a high impedance the receiver or amp won't ¨see¨ them. One or several pairs of speaker out on the amp are electrically in parallel, so hooking two cables to the same terminal will yield the same safe result.

I should know; been using this same setup for several years to great result; a vintage Pioneer receiver with a JBL sub.

 

Tony, let me see if I can expand a little on the issue. I have a couple of amps that I use in my system right now, the as noted, Rowland model 8 ( which is actually at Jeff's right now getting mod'ed) and an ARC D70 Mk2 tube amp. Both amps are balanced designs. I do not think that they have balanced outputs, but they do have a balanced input configuration. The grounding on both of these amps floats. From what I understand, and I am no elec engineer, the grounding of the REL is dependent on the Speakon connection seeing ground on pin 1. If the REL connector is not properly grounded to the amp, due to the balanced design...and because both amps float ground, then a ground loop will be evident with potential damage to both the amp and the sub due to a continuous short.
REL in their instruction manual does allude to this, although I think they do a VERY poor job of explaining the issue.
On the Rowland amp, the dual speaker ouputs are designed for bi-wiring or bi-amping, the outputs are connected in parallel.

Anyhow, If one owns a balanced design tube amp, like the older ARC's, then the connection protocol to the amp with the REL is: Red to right at the 8ohm speaker terminal, Yellow to the left at the 8ohm speaker terminal and the ground wire...black, to the left or right 4ohm speaker terminal.

 

Connection works great. Positive in each channel, plus one ground.

 

I've had my REL connected to several power amps including my ARC D240, VS110, Parasound A23, Peachtree Decco65, NAD D3020, and others (but covers most amp types out there!) and have always had great results with the high level inputs.

Only issue I did have is that the Peachtree would cause an annoying hum when ever the Decco was powered off.

I can also say that I moved my REL T3 to the den and replaced it with a tiny Sumiko S.0. I plugged in the REL cable and it was fine.

 

This is how I have had my REL T-5 connected for years and never thought anything of it.