[Fredly]

Hello, Fred here from Toronto, I have an issue that I hope someone can assist me with.

For the last 4 years, I’ve had 5 in-wall speakers throughout my house, which were successfully driven by a 30 watt amp.

Each Speaker is connected to the Amp by a Volume Control switch, which has jumpers so, when jumpered correctly, can run up to 8 speakers. (Runco and Monoprice sell these Volume Controls)

At any rate, life was good and the amp performed perfectly and could easily play music loudly throughout the house, with no signs of distortion/clipping.

So…recently I added a 6th  pair of in-walls, again ensuring that the jumper was properly set, yet NOW the Amp gets incredibly hot and starts clipping at medium Volume.

Why is this?

With the addition of the last pair of speakers am I now pushing the Amp to its max?

Perhaps the Amp is becoming unstable and is incapable of driving this load?

I have been considering pickup up a cheap T-Amp as a replacement, which I’ve been told are very forgiving and running incredibly cool.

I did a resistance check at the speakers ends, where all the speakers join, and got a 2.2ohm reading, (I would have thought it would be more like 4ohm)

Anyways, any advice or words of wisdom would very much be appreciated.

Thanx much for your attention to this matter, Fred

[srb]

Many amplifiers will have a problem driving a 2 ohm load.  In addition, the ohmmeter measurement is a DC resistance measurement - the reactive load with a music signal may even dip below 2 ohms at certain frequencies.

Most inexpensive T-amps will also have a problem driving ~ 2 ohm loads.  What equipment are you using?  What are the models of amplifier, volume controls and speakers and how are they wired together?

Maybe an alternate series/parallel wiring scheme could result in a higher impedance load?

Steve

[JLM]

30 watts + long cable runs+ 6 pairs of speakers = trouble (too little power, too long of cables that "deaden" the sound, too many speakers - possible very low impedance)

Distributed sound is best done via digital feeds (many options, but more expensive) to separate amp/speaker pairings.  Not only will you get better sound, but it can be varied per feed.

[hoxuanduc]

You can rewire the speakers for parallel/series instead of all parallel to get the impedance up. e.g. for a pair of speakers, connect + from one speaker to - on the other speaker, then the remaining - and + can be connect to the amp, effectively double the impedance.

[srb]

I'm not sure how you managed to run 5 pairs of speakers off of a 30W amp in the past, but obviously the 6th pair broke the camel's back.

If the speakers all have 'home run' cable runs back to a central location, you might also consider a 12 channel distribution power amplifier that is designed for this purpose with each speaker getting its own ~30W or > channel.  Distribution amps like the Sonance 1230 or 1250 come up occasionally on Audiogon for ~ $200 to $250 used.

It also might depend upon your present amp having a preamp output that can drive the power amp, particularly if you have more than one program source.

Steve

[Fredly]

Thanx all for your input/feedback, much appreciated.

The Volume Controls and in-walls are all from Monoprice (don’t worry my main system is of much high caliber) 

The Vol Control link is here;

http://www.monoprice.com/products/product.asp?c_id=109&cp_id=10903&cs_id=1090302&p_id=8244&seq=1&format=2

The Vol Control jumper setting chart (which clearly shows it’s capable of running up to 8 speakers) can be found here;

http://www.monoprice.com/products/product.asp?c_id=109&cp_id=10903&cs_id=1090302&p_id=8244&seq=1&format=3#specification

The in-wall speaker link is here;

http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10837&cs_id=1083702&p_id=4100&seq=1&format=2

Changing the speaker from parallel to series really isn’t an option at this point as everything is wired to go through/via the Vol Controls and the 6 speakers in question are in entirely different locations through the house.

Getting an amp with mutli Zones is also not an option, as the all 6 speakers affectively join to 1 main “trunk” line throughout the house, so all I have available where the amp connects is a single +- right and left channel cable.

Again, life was good with 5 speakers, but adding the 6th pair simply brought the config to its knees.
I’m confused as to why the Vol Controls even have the jumper setting to accommodate up to 8 speakers IF this configuration would simply kill a amp.

The amp I’ve been using for the past 4 years is a Jolida 30W. It has a tube pre/solid state backend. It’s a nice amp, but I think it’s being pushed to the max, so am hoping that a more powerful (50+W) chip amp may resolve.

Again, I look forward to any thoughts/input , Fred in Toronto

[CSI]

Hello,

For my day job I do trouble shooting on exactly the kind of problems you are having. You are running up against Ohm's law. As pointed out, very few amps can drive a load as low as the one you are presenting to your amp. The impedance matching volume controls have allowed you to side step the issue by raising the total system impedance and they are the best band aids in the business. But they are still band aids. Each time you raise the impedance and/or add more speakers you are decreasing the amount of total power available to drive each one of them. Series wiring can help but it brings its own sonic issues to the mix and it not an option in your installation anyway. There are simple formulas available on line that will calculate these loads for you (as well as the system impedance). You will find that you may be marginally able to drive the loads from an impedance standpoint but the power available to each one is seriously diminished. Doubling or even tripling the power might help but your real problem is impedance. The bottom line is, your amp was designed to drive one or two pairs of speakers and beyond that you are just trying to fool mother nature. Best advice? Use a purpose designed distribution amp like the one mentioned in the string (I'm not affiliated in any way with them) or, better yet, use a multi-channel amp. Horses for courses.

[randytsuch]

What is the impedance of the speakers you added?
Of the speakers already installed?

BTW, you can rewire the speakers to change some to series at the volume control, but it might cause other problems as stated.

I was also wondering what the monoprice actually does when you change the jumper settings.  The simpliest thing would be to add resistance as required, but I was wondering if it did something more sophisticated than that.

Randy

[CSI]

Randy,

I don't know about the Monoprice controls but most impedance matchers are autoformer based. All they really do is move the taps so that your highest available setting still has more transformer windings (and thus higher impedance) in the circuit than they would if the control were completely bypassed. That way, even at full clockwise rotation, the control "multiplies" the impedance so that the amp is seeing the nominal impedance of the speaker (say 8 ohms) plus an X factor (say X2) for a total of 16 ohms. Safe territory. Then, as you turn the control counter clockwise, even more windings are added to the circuit and volume is further attenuated.

[Fredly]

Gents, thanx again for your input, very much appreciated.

CSI, its sounds like you know what you’re talking about, and I agree with you, ohm’s law is simply winning here.

Just curious, would an amp like the one below, potentially solve my issue?

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-812

It does have 5X the Wattage and is T-Amp, which I understand are FAR more forgiving with speaker load and run extremely cool.

Thankfully, if need be, I can separate the 6 speaker pairs, into two bundles of 3 pairs, at the Stereo end, so if the amp doesn’t resolve my issue,  I can run the 6 speakers through two different amps in a pinch.

Again, baffled why they even sell this kind of Vol ume Controller, if most amps are incapable of running multiple speakers off of one amp.

Russound also sells a similar Vol Control,
 
http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/55031415_PM_EN.pdf

Kind regards, Fred

[srb]

It's possible that the Dayton APA150 may be up to the task, and it is fan-cooled, but the only way to know for sure would be trying it in your system.

I would be more inclined to find an amplifier that has an actual 2 ohm load capability such as something like the Onkyo A-5VL, although it is 2X+ the cost of the Dayton APA150.  Some of the NAD integrateds are also stated to be able to drive down to 2 ohm loads.

BTW, the Dayton APA150 is not a T-amp, but is a conventional Class A/B amplifier, fan cooled, with a linear power supply.

Steve

[Fredly]

Thanx for your input srb, I think I'm going to order the APA150 in the near future and give it a try.

Fred