Speaker Selectors

[michaelman2]

Hi all,

I am needing some advice regarding using a receiver where I have connected a power amplifier. I want to connect the power amp to three sets of large speakers which I have in three different rooms. I understand a unit called a "speaker selector" is necessary. I would like to have separate volume controls for each room/set of speakers.

I play the speakers (Cerwin Vega D-9s) at at fairly loud volume at times. What do I need to purchase? I am very green on this and have read several reviews on these selector units. Some have damaged receivers/amplifiers and some have not been powered and lost fidelity etc....

Any advice or wisdom will be happily received and I will be grateful!

 

[whirlcool]

Do you mean you are connecting a pre amp to a power amp up front? A receiver is an amp and a tuner combined into one unit. You don't need a receiver if you have a power amp. But then again even I have used a receiver as a pre amp before. It had pre-outputs that went to the power amp before the amp that was built into the receiver.

Maybe if you told us the makes and models of the equipment you have now it would help us understand more.

 

[kb0nes]

Mike,

There are devices like say a Pyle Audio PSPVC4 (look at www.parts-express.com ) which gives you a 4 speaker pair capable box that allows you to switch and control volume independently to each speaker set. Of course it is doing all the level control by placing a variable resistance L-pad inline with each speaker. It should maintain a reasonable impedance to the amp so I doubt it would cause any damage. Perhaps this is just what you need.

Personally I suggest using separate amps though. Adding resistive level controls in between the amp and speakers reduces the ability of the amp to control the speaker movements by reducing the damping factor. We spend all that money (some more then others!) for big low-resistance speaker cables, adding the resistive pad goes against the grain for me, Heck I don't even like passive crossovers in the speakers, but I digress... For background music you'd do fine with the L-pads, but if you like to play loud or listen critically I'd look into having an amp for each room.

You didn't mention the amp you plan to use, I remember we talked about a Hafler at some point. A DH-220 would easily drive 3 pairs of speakers (although you may need to increase the speaker fuse size). Many of the Japanese receivers from the 70's & 80's may not take kindly to the low load impedance imposed by more then a couple pairs of speakers. They protected their output stages from overloading with sensitive protection relays. The Hafler has no such protection (doesn't need it), the speaker fuses are there to protect the speakers only. Again if I were to do it I'd look for some NAD or Yamaha (Silver face preferred) integrated amplifiers and place one in each room. This would give a lot more versatility then the simple level matching box.

 

[michaelman2]

Thanks Allen and Phil,

I should have posted the original equipment being used, my mush brain was in gear, sorry.

I am using a:

Marantz 2270 receiver as the pre-amp (this model has a connection that allows for a external power amp).

Rotel RB9808-RX (120 watts per channel, reading from the specs)

(2) Cerwin Vega D-9 Speakers 5W-350W Max- 8 OHM

(2) Cerwin Vega RE-30 Speakers 5W -250W Max - 4 OHM

The Marantz receiver has enough outputs for two sets of speakers, however I suspect this is really placing a load on the amp in the receiver when I crank the volume up?

I also am using a very heavy gauge speaker wire and one set will be about 20 feet away from the amp.

The room is large and the two D-9s driven with the Marantz did pump some volume. I would like to place the RE-30s at the other end of the room so there is a decent balance in the room. I am trying to figure out what the best route would be for playing the four speakers simultaneously and at a loud volume. Hence the speaker selector question.

Years ago and being a total novice, I would have simply placed two speaker wires in to each of the outputs and run the wires to the speakers. So instead of one speaker connected to the output there would be two connected. I realize that this is not smart and can damage the speakers and amp/receiver.

Guys, thanks for reading this and any guidance you might provide is absolutely appreciated.

 

[kb0nes]

Mike,

A few things that are in your favor.

That Rotel amp is a robust design with lots of current capacity. It will drive 2 pairs of speakers easily.

The CV speakers are typically a few db more sensitive then many typical home speakers so they won't need as much drive power to rich a given volume.

You did mention a 3rd pair of speakers too.

One option may be running the 2-pairs of CV's all off the Rotel just by paralleling the leads. Of course this doesn't give any options for volume matching etc.

The 3rd set of speakers could run off the 2270's internal power amplifier. You'd need some "y" adapters to split the pre-outs into the internal amp and the Rotel. The preamp would easily drive both amplifiers.

I'd start simple and build onto the basics. You may not need anything you don't have currently.

And as a general rule of thumb, if you are hearing clean distortion free audio you probably aren't hurting anything. If it starts to sound bad turn it down and find out why! Generally its impossible to hurt a speaker with too large an amp if you live by the above rule. Amazingly its often smaller overloaded amps that cause speaker damage. For this reason I have never looked at speaker power ratings. Also a competent amp like that Rotel could live with a very low load impedance. It will sound bad, trip protection or blow fuses before you are likely to damage the amp. It will likely let you know its unhappy!

 

[michaelman2]

Hey Phil....music to my ears, pardon the pun.

Okay the Rotel only has one pair of speaker outputs? I am not sure about "paralleling the leads". Would I simply connect two sets of speakers to the same outputs on the Rotel?

You are correct, I do have a third set of speakers however they are in a completely different area of my home and I am pretty much relegated to using a completely different receiver for those and be done with it.

Also, does the length of cable lessen the quality of sound, impedance etc?

Thanks again Phil for indulging me.

 

[kb0nes]

Indeed you can just parallel the speakers across the pair of outputs on the amplifier. Be sure to keep note of the phasing though. If an amplifier has a 2nd set of outputs in 99% of the cases it is simply paralleled internally, although often there is a selector switch for convenience.

A great way to connect speakers to amp like your Rotel is to use dual-banana style plugs. These are standard banana style plugs that have 3/4" spacing to plug straight into your binding posts on the amp. The cool thing about this style connector is that they are stack-able so you can plug one into the rear of the other to parallel a pair of speakers. You can also easily flip them over since they aren't polarized making altering phasing easy! Unfortunately most receivers don't have decent speaker connectors that accept banana plugs, but most all quality HiFi power amps do. You may want to confirm your Rotel appears to have 3/4" spaced binding posts but I'd bet it does. You can buy dual-banana plugs at Parts Express and many places on the web. You can likely use double-banana connectors to plug into your CV speakers too.

One handy trick if you want to test speaker phasing is to touch the speaker leads to a 1.5v battery and observe the direction the woofer cone moves (inwards or outwards). You want all the cones in the room to move the same relative direction when you apply a positive voltage to the "red" lead to the speakers. The actual directions the cones move isn't critical, but they all must move together in the same direction though. There is a cool iPhone app for speaker phasing too!

Finally to the speaker cable, for runs under say 50 feet as long as you have 16ga or larger wire you should be just fine. Normal old 2-conductor lamp cord is just fine. I have bought 50 foot 14ga extension cords and cut the ends off them too. Total resistance for both legs of a 50 foot 16ga run would be ~.4 ohms (14ga drops to ~.2 ohms). Shorter runs are obviously preferable.