Im

I'm having problems with connecting eight speakers to a Yamaha or Dennon receiver, utilizing impendence-matching volume controls. I am using this setup in a doctor's office with 8 speakers, each with a dedicated volume control (each is used as a mono speaker).

I don't like 70-volt stuff. I would like to stay with 8-Ohm speakers. I have been using either Posh 528 speakers or Sonance TR-622s. I have tried three brands of volume controls, all with impedence compensation, Sonance, Russound, and Jamo. The receivers are Dennon DRA-395 and Yamaha RX-496.

This is the problem. No matter what I do, the thermal cutout keeps kicking the receiver off. I used both Yamahas and Dennons in the past without a problem, but recently (in the last year or so), they won't handle the load. I have even tried to use the 4X winding of the controls, which should bring the impendence to 8 Ohms. So why does it keep shutting down? Have Dennon and Yamaha receivers turned to crap like so many other brands? Or is it the controls? I don't own an impedence meter, but I would think either Dennon or Yamaha receivers would be comfortable with 4 Ohms, let alone 8 Ohms!

I know what some of you will say-- use a speaker selector box. I am well aware of speaker selector boxes, and how poorly they can make a speaker sound. I am also familiar with big autoformers and resistance boxes. Resistor boxes make speakers sound like half of their value typically. Autoformers create less of a compromise in sound in my opinion, but they are expensive.

Can any one tell me why the impedence-matching volume controls don't do the trick? I have even had problems driving 6 speakers with impedence-matching controls. That's 5.3 Ohms-- shouldn't the receiver be able to handle that? If it's the receiver, is there any moderately priced stereo receiver that will do the job?

I'd love to hear your input on this. Thanks guys.

Stew, there are other factors that limit an amplifier from being able to handle a group of speakers with volume controls, of which I am not going to go into detail. I have used Denon & Yamaha gear extensivly with volume controls with no problems. There could be something else causing the amps to thermal out. First you say you have 8 mono speakers, are you using mono vc's? With 8 vc's your impedance match setting should probably be 8X. With a mono vc harder to find - I use Elan), you could put 4 vc's on the left channel and 4 on the right channel with imp match at 4X, that will decrease the load on the amp a bit. But you still may want to try 8X if that load is a problem. Otherwise be sure there are no shorts etc. in the lines and that all the volume controls are hooked up properly (not backwards). With stereo vc's, the second channel should not be connected, but you will be wasting 1/2 the vc. A speaker switcher should not be necessary & does not fix your impedance/reactance problem. Usually these switchers employ resistive impedance matching when used (selectable). As far as sound quality, a speaker switcher imho is usually the best, with the autoformer picking up the rear, but convienience trumps the switcher every time. As far as volume, there is always a sacrafice when you are trying to make the amp happy with the increased load, in every application. Others may disagree with me, on this forum that happens a bit. But you are sure to get some ideas to help you. When in doubt, call your local installer to check things out for you, usually it is money well spent. Good luck.

Had same problem once(and in a dentist's office) One of the vc was wired backwards. Also, unit was DRA-395, works great.

I appreciate your advice, guys. However, I am not new at this. I have thirty-five years experience and an engineering degree. Never the less, I appreciate your response.

While the volume controls are stereo, I am using only one side for mono. I haven't found a really good control with mono. I have heard that Audioplex is good however, so I might give it a try. That is still not the problem.

I am also familiar with the problems caused by hooking up a control backwards. As soon as you turn it all of the way down, it shorts out the amp.

I think the problem is either with the controls or the amplifier. Either impedence-matching controls don't work as they are suppose to, or the amplifiers are not stable below 8 Ohms. I suspect the latter. I may have to break down and buy an impedence meter, but simple math has never failed me in the past. Surely others have experienced the same problems and I would like to hear your take on it.

Thanks again for your help.

Hi Stew you know all this already but i have found this site helpful.

[Link: colomar.com]

bob

Hi,
I've not used impedance matching controls in the past, but inherited a job where Sonance 1x-2x-4x-8x were prewired. I turned off the protection on the speaker selector box, thinking that the controls would take care of it. Checked the wiring of each. Amp kept cutting out. (By the way, this is not a thermal overload you are experiencing. You are seeing a CURRENT overload. The amp senses the current flow in the output stage is excessive and is engaging the protection circuit. As another aside, very few amps have thermal sensors that cause the amp to cut out. All have thermal sensors to stabilize the current flow in the output stage, but if you are cutting out, it is 99% of the time going to be excessive current flow in the amp, which equals the amp trying to feed a near-short circuit). Back to the topic: I re-engaged the protection (resistor) on the switch box and it's singing happily to this day.
I know this is corny, but I took the path of (not) least resistance, in a manner of speaking.
=Tom

Had this same experience once (except I was using both channels instead of just one). The house only had two volume controls in it (set for X2), which should have been no problem, but the customers amp would kick off, especially when adjusting the volume controls. Like you I have put hundreds of these in (I still wire one up backwards every now and then), but everything was right (had other people check it). The only thing different is that our shop had received vol controls from another manufacturer when we always have used Russound. I ended up pulling the other brand vol controls and replaced with Russound and the system has been working problem free for several years now. I don't know if I had a bad one or if the design of the other vol controls was poor (although they were not cheapo's), but they were manufacturers first time release of these units so maybe there was something not quite right with them.

Anyway, I don't know if this helps any, but if you can try using a different manufacturers product, it may help out.

I have tried Russound volume controls with impedence matching. Actually, I had more trouble with them than I did with another brand (Jamo). I set the impedence jumpers to 4X, which supposedly brought the net impedence to 8 Ohms. I was using four 8-Ohm speakers per channel. I still kept popping the protection circuit on a Dennon DRA-395 if I raised the volume past about half way up on the receiver. Yes, the controls were hooked up correctly, and no, there were not shorts in the wiring or speakers.

My question is this: Do the controls really double or quadruple impedence? I'm not sure they do actually work as they are suppose to.

To check the Dennon for the problem, I hooked up two pairs of the same speakers (Sonance TR622) without volume controls. With each pair rated at 8 Ohms, that should equal four ohms. I turned on the receiver and had no problem with it shutting down, even at louder volumes. Okay, then I tried four pairs of the same speakers using impedence-doubling volume controls. It shuts down the amp at about half volume on the receiver. Is there something that I'm missing here? Doesn't the problem point towards the volume controls?

I know that I can solve the problem with a speaker selector with built-in series resistors. However, I don't want to spend unnecessary money on a speaker selector, and ruin the sound of the speakers in the process. Lets face it, speaker selectors that use series resistors have the same effect as using lousy speaker wire-- it adds a lot of resistance, which leaves it sounding lifeless.

Any help would be appreciated, even if I have already tried it. Thanks.

i vote for the multi-meter ..... i have 10 years in car audio before i got interested in custom home and always start there from habit .... its amazing how often the sheet rock guys stick a screw into stuff if you dont watch it ...

I also have had a problem with brands of volume controls that have two jumpers , and set the whole house "right" channel on 8x before i realized what was going on ..

curious to see what the meter reads per side .....

There are some amplifier designs that do not mate well with impedance matching controls. Typically this is a fuction of over correction or error in the feedback loop of amplifiers that use high negative feedback to reduce audible distortion. You clould try a different amplifier, or one of the few resistive volume controls, I belive both Phoenix Gold and Knoll make one.

jcmitch

[Link: phoenixgold.com]

[Link: knollsystems.com]

Stew,

First things first. Get yourself a Goldline meter.

Then you'll be able to ENSURE that you've got the 8 ohm load you want, rather than assume you have an 8 ohm load.

Second thing?

Why not use dual voice coil speakers? That way both channels will be introduced into each location, rather than just the left or right.

Bear in mind that you are placing an extra load on a stereo amp by having no load on one of the channels. That may well be the reason the amp is going thermal on you.

Last thing.

Russound volume controls?

I've used Russound for many, many years. Had 1 (one) bad volume control out of maybe 200. And the only thing bad about that particular control was that it wouldn't stop at the limits (yes, it still worked). Sorry, but I can't believe that Russound volume controls were ever the cause of this problem.

I use RX-496's all the time in similar applications without any problems -- most of the time.

When I do have trouble it is almost always my own fault. It is just too easy to hook a control up backwards. If you have any splices in the wall, find them and check them. I won't say I've never had a bad control, but it is very very unusual.

In your case, since you've been through so many controls, start looking at the wiring. Use an Ohmmeter to check the wiring. Look for shorts between the wires and also check for shorts to the building ground. Set the controls for 8x. It won't hurt anything and will make the system more goof proof. Note that some controls have two jumpers per channel.

I work with D-I-Y's who are all very smart (much smarter than anyone in this industry), have all sorts of degrees, are very careful to hook everything up correctly (this is so easy), and "must have bad controls or amplifiers". "I even had my buddy check it out and he says I have a bad control." -sigh- It's a problem. We always get it straightened out, but it usually takes several lengthy phone calls before they will actually check their work.

You are not having a thermal shutdown problem. There is an over current "protection" circuit that will shut the amplifier down for a few seconds after an "event". A thermal shutdown would last at least a few minutes (while the unit cools) or be permenant if you abused the unit to the point where the fire protection link in the power transformer opened.

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If you want a really odd problem to chase, consider that you could be saturating the autotransformers. If you sock the autotransformers with too much bass, the transformer cores will saturate and the control will present a very low impedance to the receiver, thus tripping the protection. You will notice this only on very large bass peaks. Unless you are dealing with "disco Doc", I don't think this is your problem.

I've never had this sort of issue with an RX-496.

When I've had similar issues and the customer wouldn't cooperate, I installed filters in the speaker leads that reduced the bass current.

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Has the customer been complaining that the system is not loud enough? Check the remote volume control settings. Sometimes the customer will have them all turned down and have the receiver turned up to the point of clipping in an effort to get the volume in the rooms up to a useful level. Customer education will usually cure this problem, but you may have to charge them for a service call to get their attention.

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Once you have assumed that (...) is or could not possibly be your problem, it is likely that you will never solve it.

Stew,
Good advice about getting that impedance meter, but in the meantime, why not take your multimeter and individually read the resistance at terminus of each wire leading to the VC's after making sure they are all set at max, then 1/2 way, etc. Obviously, you won't be reading impedance, but it may show something amiss on one or more of the loads. I know you have checked for shorts between conductors, but what if you have a conductor shorted to ground somewhere?
Jeff

Xantech, Russound, and probably others offer some plug-in 4-conductor junction strips. They allow quick, easy, clean, and neat interconnection of the speaker wires at the receiver.

Best of all, you can break the system apart in a few seconds for diagnostic purposes.