Speaker switch vs hard wiring? Need informed opinion

[Aadams]

I have searched this site for discussions of wiring multiple identical speaker systems in close configurations and playing simultaneously but I cannot find an instance where my question has been discussed. 

 I will be configuring three pairs of identical 2 way 8 ohm speakers to be fed from a single amp that has a 2 ohm rating but the amp has only one set of left and right speaker outputs.  Speakers will be triple sets of left and right stereo.

The question: Does anyone here have experience with Niles speaker switches? 

The Niles boxes seem to simplify the wiring problem and stabilize the load at 4 ohms but I don’t want to introduce audible noise.  Are they audiophile quality?  My alternative, without additional amplifiers, is to gang wire the speakers in parallel which is not complicated but it is a bit messy or even worse I could wire in series parallel which to me is really messy. 

[Jeff_C]

I am unsure of your use purpose for the proposed Niles Speaker Switcher but these switch boxes are primarily used to locate multiple speakers in multiple rooms. If you intend to use a bank of 3 x left speaker and 3 x right speaker in the same location I would definitely wire them up without the speaker switcher. I have just had a quick look at this article

http://www.audioholics.com/diy-audio/how-to-use-a-speaker-selector-for-multi-room-audio

The way the Niles boxes seem to 'stabilise at 4 Ohms' is by adding in some impedance when the 'protection' is switched on. That means losing some of the available power from the amp. Another thing is that the spring type speaker terminals will not take decent gauge speaker wire, and if the wire runs are long then the sound quality could be impaired.

Depending on what you want to set up I would go with some DIY passive wiring arrangement. With three sets of speakers the option to wire series-parallel is not available. You would generally need 4 sets of speakers for that.

 

 

[Aadams]

Jeff

Thanks

The wire runs will be no more than 10 ft and the Niles Switchbox which I believe is rated to handle 250w per channel will take 14G wire

The rated 4 ohm output of the amp in question is 350/channel so each speaker will still see around 115 if I am understanding this correctly.  I never drive systems hard so I don't think the switchbox will be in danger though it does appear to be the weak link.

The system envisioned will have 3 identical 2 way speakers on both left and right accompanied by left and right 8 or 10 inch powered sub woofers.  

The speaker switch would be either a 4 or 6 pair switch with one switch position used to wire the pair of subwoofers.

If I can use the switch then every connection becomes a straight wire run.  If no switch I have to route through the left and right sub back panels and onward to the parallel wired triple sets on the corresponding side.  The main purpose of the Switchbox in this case is merely to simplify the wiring for the person who will get the system after it is completed. 

My main concern is that the Niles or whatever brand box not introduce audible noise, which is not usually a concern when these boxes are used to power remote speakers in areas of ambient noise produced from social activities that are loud enough to make an added noise component irrelevant.   However, the goal for this system is to be audiophile grade and I want to avoid spending money on a box that will add audible noise.

Adams

 

[ra.ra]

I do this sort of thing all the time using an Adcom GFS-6 speaker selector, which includes a protection switch for simultaneous use of multiple speakers. The only info I have for Niles products is the SS-4/6 selector, but its rated power handling is limited to 100 watts, so I presume you're considering a different model. Both of these mentioned models have speaker wire connections that are a little bit awkward, but perhaps you can find a model that has convenient banana jacks.  

[Aadams]

Have been looking at the Niles HPS-4 but there are some nice used Adcom GFS-6s for sale.  Banana Jacks would be nice but I can tin the leads for this project.  Thanks

Adams

[ra.ra]

If you can find the Adcom GFS-300 (see pic), that'd be nice - - it looks just like the lower wattage GFS-3, but has a 200w limit and multi-binding posts. Also, the Rotel RSS-900 looks to be a fine unit - - up to six pairs, 200 watt limit, rocker switches on front, multi-banana jacks on rear.

correction: I just looked at GFS-3/6 manual, and those models also have a 200 watt limit. 

[Aadams]

Ra Ra

This is good stuff. 

Question:  Is there an audible change in sound quality, in your opinion, when the speaker protection circuit is switch in.  The Adcom lit seems to recommend  not using it if it is not needed. 

Another question.  You said you do this sort of thing all the time.  Are you using arrays of identical speakers or comparing different models and brands?

Adams

 

 

 

[Jeff_C]

19 hours ago, Aadams said:

(1) The rated 4 ohm output of the amp in question is 350/channel so each speaker will still see around 115 if I am understanding this correctly...

(2) If I can use the switch then every connection becomes a straight wire run.  If no switch I have to route through the left and right sub back panels and onward to the parallel wired triple sets on the corresponding side.  The main purpose of the Switchbox in this case is merely to simplify the wiring for the person who will get the system after it is completed. 

My main concern is that the Niles or whatever brand box not introduce audible noise, which is not usually a concern when these boxes are used to power remote speakers in areas of ambient noise produced from social activities that are loud enough to make an added noise component irrelevant.   However, the goal for this system is to be audiophile grade and I want to avoid spending money on a box that will add audible noise.

Adams

 

Re (1) It is not likely to be as straightforward as that. If the amp can deliver 350W into 4 Ohms then if 3 pairs of 6 Ohm speaker are wired in parallel the resulting load will be nominally 2 Ohms. Then the protection switch may add in 2 Ohms (or more) to the circuit making the resulting load nominally 4 Ohms. Now here's an important point about power dissipation. The 350W will divide up so that 175W will be dissipated across the 3 speaker set (with a nominal 2 Ohm impedance) and the other 175W will be dissipated across the protection circuit's added 2 Ohm.  For the reasons explained above it will be beneficial to know exactly what the protection switch does to the circuit.

Re (2) It would be possible to run a single decent gauge wire from the amp to the location of the speakers and from there make it branch out to wire up the 3 speakers. So just a single wire on show across most of the room. 

[Aadams]

Jeff

RE Item 1:  I am sure you know more about this than I.  The array speakers are Boston CR65s 88db sensitivity.  If with triplets, it takes 3 watts instead of 1 to get 88db at 1 meter then, even with only 175 watts available, I should have around 15 db of dynamic range at around 3 meters before adding room gain.   I am not all certain about the math BTW.

There will be an equalizer ahead of the amplifier that will be used to only cut, not boost, frequencies below about 125hz so I should get some relief ahead of the switch box.

Frequencies below the approx. 125 will be re-boosted as needed by the plate amps in the sub woofers .

I am not trying to argue FOR the box.  I see it mainly as a device to simplify the wiring and as a safety precaution.

RE Item 2:  I absolutely agree. If I were not forced to wire through the subwoofers and absolutely trusted what the amp mfr says about the 2ohm capacity of the amp I would go straight wire to a harness without question.

 The amp candidate is a Crown xls 1002 series 2.  I got an email from a crown engineer saying “ stereo 2ohm load in a home environment ..no problem” but it is not his money and time.  If someone here has actual experience with the amp it would be good to hear some feedback.

Adams

[ra.ra]

4 hours ago, Aadams said:

Are you using arrays of identical speakers or comparing different models and brands?

Adams, I use the Adcom speaker selector simply because I enjoy having multiple pairs of loudspeakers wired up simultaneously in order to have a variety of listening options. Unlike many ardent members here who are attracted to large speaker models and mega-watt power, all of my equipment is small, modest, and low wattage. The speaker selector is currently connected to a Crown D-75 power amplifier, and I think right now I have four pairs of Classic-era 8-ohm AR's connected. For me, this set-up allows for a simple arrangement to make casual comparisons of various small AR two-ways - - - AR-4's, 4x's, 4xa's, 6's, 7's, etc - - - but at other times, I may wire up several pairs of the same model (say, three pairs of AR-6's) to evaluate these differences as well. At other times, I'll listen to multiple pairs at the same time (with circuit protection "on").   

4 hours ago, Aadams said:

Is there an audible change in sound quality, in your opinion, when the speaker protection circuit is switch in

Engagement of the protection circuitry is only recommended when you play two or more pairs simultaneously, and probably even unnecessary when playing two pairs of 8-ohm speakers at moderate levels. I tend to listen at fairly low levels, so I've probably never really challenged this to the extreme, but I could probably say there may be a very slight reduction of SPL when the switch is activated and the resistance is added. 

Pic attached shows inside of Adcom GFS-6 (not mine) with three pairs of the original twist connections replaced with multi-posts. The lower right black switch button activates the protection, and the two big green iguanas are the 2.5 ohm resistors, measuring almost 4.5" in length each!  

[Aadams]

Thx Ra.Ra

I will most likely get the gfs 6 but if a 600 pops up in time I will try for that .  I am still accumulating speaker pairs and testing my idea with a small 4ohm capable receiver before I scale up.

Adams

[Jeff_C]

Adams - I have found out that the CR65 have nominal impedance of 8 Ohms. I would try and find out what the minimum impedance is and at what frequency(ies) the lowest impedance occurs. The fact that the CR65s are 8Ohm makes things a little easier because wiring in parallel gives a nominal impedance of 2.66 Ohms. If you set this up without a switchbox it should fall within the amp's operating spec, and you will have the advantage that the full power availability into that 2.66 Ohm load will be being used to create sound, (rather than being wasted as pure heat dissipating across a protection circuit resistor). In turn that will mean that you will not need to crank the volume up so much to get to the desired listening levels. If it were me I would try the setup without a switchbox especially if the switchbox would only serve as 'protection'. It is worth investigating whether the amp features any protection circuitry. Many just shut down if safe operating limits are exceeded. As for the wiring harness  you could code all the up the cables with matching codes on the speaker terminals so the end user cannot go wrong.

The only thing I am unsure about is how the subwoofers affect things as I have never used subs or even contemplated using subs.  But as the subs are self-powered with their own amplifiers I doubt that they affect impedance calculations but I would certainly want to be sure about that first. 

[Aadams]

Ok Jeff

I did fire off emails to the tech support at Outlaw and Crown.  I am still waiting on answers but I have done some internet searches and it looks like I can have it both ways. Anecdotal evidence indicates the XLS series has no problem carrying a stable 2ohm load and has speaker protection circuitry built in with power peak and thermal peak limiters.  I could use the Adcom box for wiring and only use the protection switch as a safety valve.  Anecdotal info also indicates the Sub woofer impedance at the high level speaker inputs is so high that the power amp does not see the sub woofer as a load.  Will let you know more when I hear from the tech people. Writing rhetorically, I wonder if this 7 to 9 drivers per side is why LSTs were a bear to drive and if it is a reason they had an autoformer?

Adams

[Jeff_C]

12 hours ago, Aadams said:

Anecdotal info also indicates the Sub woofer impedance at the high level speaker inputs is so high that the power amp does not see the sub woofer as a load...

That fits perfectly with my thoughts on the affect on impedance of adding subs. I hope that proves to be the case.

[Aadams]

On ‎3‎/‎29‎/‎2017 at 9:40 AM, Jeff_C said:

Adams - I have found out that the CR65 have nominal impedance of 8 Ohms. I would try and find out what the minimum impedance is and at what frequency(ies) the lowest impedance occurs. The fact that the CR65s are 8Ohm makes things a little easier because wiring in parallel gives a nominal impedance of 2.66 Ohms. If you set this up without a switchbox it should fall within the amp's operating spec, and you will have the advantage that the full power availability into that 2.66 Ohm load will be being used to create sound, (rather than being wasted as pure heat dissipating across a protection circuit resistor). In turn that will mean that you will not need to crank the volume up so much to get to the desired listening levels. If it were me I would try the setup without a switchbox especially if the switchbox would only serve as 'protection'. It is worth investigating whether the amp features any protection circuitry. Many just shut down if safe operating limits are exceeded. As for the wiring harness  you could code all the up the cables with matching codes on the speaker terminals so the end user cannot go wrong.

The only thing I am unsure about is how the subwoofers affect things as I have never used subs or even contemplated using subs.  But as the subs are self-powered with their own amplifiers I doubt that they affect impedance calculations but I would certainly want to be sure about that first. 

Jeff C

Got the answers from Product Tech Support. 

Subwoofer:  When using high level inputs and outputs on the subwoofer panel the effect is as straight wire.

Amp : Crown XLS 1002 .  Feature is called Peakx. It prevents the amp from operating beyond its design limits and damaging speakers or self immolating.  Peakx can be turned on or off.  All of the amp's functionality is firmware managed through a DSP developed in cooperation with Texas Instruments.  This is the bottom of the line and still way cheaper than high power vintage units with less capability.  We shall see how it goes, 215 watts/channel 8 ohms or 512 watts at 2 ohms and only $62 in 1974 dollars.  I paid $299 in 1974 for a Crown D 60 w/30 watts at 8 ohms, inflation adjusted to 2017 that's almost $1500.

Adams

[Aadams]

On ‎3‎/‎29‎/‎2017 at 9:40 AM, Jeff_C said:

As for the wiring harness  you could code all the up the cables with matching codes on the speaker terminals so the end user cannot go wrong.

The only thing I am unsure about is how the subwoofers affect things as I have never used subs or even contemplated using subs.  But as the subs are self-powered with their own amplifiers I doubt that they affect impedance calculations but I would certainly want to be sure about that first. 

It will be straight wire no switch.

[Jeff_C]

To my mind that is the neater solution, especially if the switch was never going to be used to direct the signal to different rooms. What swung your decision that way finally?

[Aadams]

4 hours ago, Jeff_C said:

To my mind that is the neater solution, especially if the switch was never going to be used to direct the signal to different rooms. What swung your decision that way finally?

Everything you said along w/ the built in safety features on the amp and its threshold indicators or are they anxiety meters .   Anyway, reading back over the thread, everything you said.

[Aadams]

On ‎3‎/‎27‎/‎2017 at 7:22 PM, ra.ra said:

If you can find the Adcom GFS-300 (see pic), that'd be nice - - it looks just like the lower wattage GFS-3, but has a 200w limit and multi-binding posts. Also, the Rotel RSS-900 looks to be a fine unit

This project is still alive.  It turns out I will parallel wire and will also need a switch box to make it convenient to connect subwoofers that don't have high level pass through terminals. I will use the switch box to share the subs among multiple speaker pairs. Sounds crazy I know.  I have too much time on my hands.