New memberUsername: Lear45jim
Post Number: 1
I wish to add 2 pairs of speakers. One to my garage from the existing distribution center to a new volume control to a new set of 8 Ohm speakers. This seems straight forward enough. The other new pair of speakers will be to my newly expanded deck. It currently has a pair of speakers controlled by a Niles volume control and I want to know if I can splice into the speaker wires after the volume control to feed the new pair of speakers. This is desired so that I can control the volume from 1 volume control. It is also very simple to do since I can easily access the wires in the attic.
Also, is my amp up to the task? How do I calculate the number of speakers it can handle? The specs are EIA 1kHz output at 8 Ohms of 140 watts and FTC full bandwidth output power at 8 Ohms 120 watts.
Thank you very much for your help.
Platinum MemberUsername: Jan_b_vigne
Post Number: 18184
The Niles volume controls are an autoformer type, which is ideal. When you add another pair of 8 Ohm (nominal) speakers to the existing vc, you will have to make the connection either in parallel or in series.
A parallel connection will essentially half the total impedance of the load (of both speaker pairs) while a series connection will essentially double the impedance. The highest impedance is always the best bet for safety of the amp though higher impedance will slightly - slightly! - reduce total volume potential.
This isn't a big problem for you since the impedance load on the amp is actually being determined by the setting on the selector. I'd go for the series connection.
You will then need to reset the vc for the total impedance load of the two combined pairs. The owner's manual for the vc has the instructions for this setting.
The power amplifier is claimed to be capable of safely driving loads down to 4 Ohms (nominal).
The idea of the autoformer vc's is to maintain a near constant, single impedance load for each speaker system to the amplifier - or, in your case, to the selector.
The selector, however, is not an autoformer type, it uses a power load resistor according to the owner's manual.
As you add speakers to the total system, you must make adjustments to the selector to maintain a safe load on the amplifier. You want to keep the total impedance load as high as possible at the selector.
You'll have to adjust the selector for the new speaker pair in the garage and the new setting on the vc where you've added an additional pair of speakers. Read your owner's manual or contact the manufacturer for more specific instructions.
It looks as though the selector can be set no higher than 4 Ohms total load value. Most solid state amplifiers can handle a 4 Ohm load when it remains fairly stable, which is the intent of the selector and the autoformer vc's.
In your system, the amp is driving the selector (not the individual speakers or vc's) and you must make the adjustments to it to maintain the amp's safety.
The impedance setting of the individual vc's is what you add up to determine the total impedance load the selector is seeing. In other words, the actual impedance of the speakers is inconsequential to any of your calculations
The autoformers isolate the amp from the actual individual speaker load and all the amp is concerned with is the impedance of the vc's autoformer as it loads the selector. In the end, the amp is seeing the load of the selector.
You need only look at the total impedance of the vc's to make your adjustments to the selector.
Any issue with compatibility would be a function of how hard you push the amp and the total number of speaker pairs/vc's
you are driving at the time.
(The advantage of the autoformer is they will always show the amp/selector a consistent impedance no matter the volume setting of the control or how many speakers are connected to the vc.)
Typically, whole house systems do not run all speakers at the same time. If all speakers are connected simultaneously, then the volume levels are normally rather low across the board.
The exceptions are the outdoor speakers which, due to the lack of reflective surfaces as found in a room, will almost always require higher wattage to achieve adequate volume levels.
Since the new speakers in the garage will only add up to a total of six pairs of speakers on the system, there shouldn't be much of a problem there.
With the speakers added to the existing pair/vc, the adjustment on the vc will maintain a decent impedance load and shouldn't bother the amp to any great degree if you then make the appropriate adjustments to the selector.
The exception is the same as any other system. If you decide to crank the volume one night, pay attention to the sound quality.
If you hear the amp distorting on peaks, the amp is clipping and you need to reduce the total volume level coming from the amp. That translates into not turning down the volume of the individual vc's which would only load down the amp further. You'll need to adjust the overall volume of all speakers by making your adjustment at the pre amp (your receiver's vc).
If you run more than, say, three pairs of speakers simultaneously, I would suggest you monitor the heat build up at the power amp.
I don't know this specific amp so I can't tell you how warm it will be during normal operation. You need to determine that by running just one set of speakers at a "normal volume level" for about thirty minutes.
As you add speaker pairs and raise volume levels, make sure the amp doesn't begin to show signs of distress by heating up quickly and not cooling down or by distorting the sound quality.
IMO there isn't a better answer to how many speakers you can drive since you probably won't be driving all speakers at all times.
You know your volume requirements and I don't. You should have sufficient wattage for most situations though.
Pay attention to the amp as you drive the system with higher volumes and/or more speakers. As long as the temperature of the amp doesn't rise dramatically, the system should be fine.
New memberUsername: Lear45jim
Post Number: 2
Platinum MemberUsername: Jan_b_vigne
Post Number: 18185
Use the system with the master volume control on the receiver set to the loudest volume level desired based upon the "loudest" (highest output Voltage) source. The master vc on the receiver feeds Voltage to the main, multichannel power amp and should be used to determine the maximum volume the system can achieve. Individual area volume levels are then determined by the vc's located in each area.
This can, in some cases, be problematic when you have more than one pair of speakers on one vc. As you move around the room you may desire slightly different volume levels from each pair of speakers. Do your hook ups with this in mind and allowing for the possible addition of another vc for the second pair of speakers.
In most cases, maximum volume is not at full rotation of the vc on the receiver. With a rather old fashioned vc as we used on "vintage" receivers, this maximum level would typically be around 1-2 O'Clock on the control.
With the newer controls however, you have a digital readout of "something". Not necessarily anything relevant to the actual Voltage output of the receiver, just something the receiver designer thought was OK for marking changes.
It is impossible therefore to suggest a readout for your receiver since nothing really matters on the digital readout other than the fact the power amp is not being overdriven and the speakers are not producing distortion components.
Since each source component has a slightly different output Voltage potential, there is no ideal, single vc setting.
You determine what the maximum is by listening to each source in the set up. The volume control on the receiver has the ability to compensate for low Voltage output from one source but does not have the ability to not overdrive the amp if another source has a significantly higher output Voltage. You'll need to set the master vc at a point where you do not risk overdriving the amp if someone switches to that louder source and doesn't compensate by lowering the master volume control.
It's a bit of a dance you do with whole house systems and it has some fudge factors built in as long as you realize the main goal is not to overdrive the power amp.
Determine the loudest volume level you would desire with all of the individual vc's in each area set to maximum. When you hear distortion on the loudest peaks or with the deepest bass signals from the source with the loudest output, you're beginning to overdrive the amplifier.
There's something on the amp's website that claims it will reduce peaks to reduce distortions. That's an imperfect system and I wouldn't suggest you rely on that for safety. Pushing the power amp while it is running into a limiter is like driving your car into a brick wall.
Simply set your master volume at a comfortable level and don't change that setting unless it is to further lower the overall volumes.
One common issue with a whole house system is the potential for too many locations where volume can be set. Over time people tend to lower the individual area vc's and they end up raising the master volume to compensate.
With autoformer vc's in each area the amp isn't being loaded in the same fashion as a resistor based control. The still present danger of individual vc's is you constantly ask the main power amp to drive into what the amp sees as that same brick wall.
This means you want to use the individual vc's set as high as possible for the maximum level desired. The master volume control should then also be set to the maximum desired volume that will not result in overdriving the power amplifier.
Once the master control is set, it needs to stay set, with the one caveat of lowering the overall volume to avoid distortion or heat build up from the amp.
The power amplifier should have good ventilation in all directions around it. That particularly means beneath it as most amps draw cool air in from under the amp and expel hot air above the amp. Allow at least 1" in all directions around the power amp and more if you can.
Small whisper fans can be added above the amp to draw more cool air through the chassis but that shouldn't be needed if you are not pushing the system on a regular schedule. As I suggested, simply monitor the warmth of the amp when you are driving the system to its loudest, most speakers being driven situation.
If other people have access to the master volume control, they need to understand it is not to be used other than to lower volume.
Lowering the vc's in each area is then perfectly acceptable practice as long as you don't try to raise the overall master volume while one area vc is set to a minimum setting.
Enjoy your system!