Regardless of the fact that you spent a minor (or major) fortune on your home stereo or theater system, it still is possible that a breakdown can happen. Since loudspeakers always manifest the problem regardless of where it actually occurs, many are quick to blame them. Sometimes folks are right - the loudspeaker failed. But often there is a failure elsewhere in the system that is merely being passed on to the speakers.

Even The Best Isn't Perfect

Gary Dayton | THIEL Loudspeakers

December 2008

Even The Best Isn't Perfect

Even The Best Isn't PerfectAuthor: Gary Dayton, THIEL Loudspeakers

Regardless of the fact that you spent a minor (or major) fortune on your home stereo or theater system, it still is possible that a breakdown can happen. Since loudspeakers always manifest the problem regardless of where it actually occurs, many are quick to blame them. Sometimes folks are right - the loudspeaker failed. But often there is a failure elsewhere in the system that is merely being passed on to the speakers.

Some basic troubleshooting skills and knowledge of fundamental concepts can go a long way towards quickly and correctly identifying the problem. Rather than calling your dealer or gear manufacturer at the first hint of trouble, doing some preliminary investigating yourself will arm you with answers to some likely questions. You'll be able to get the correct piece of gear repaired more efficiently than if you just took a stab at it and sent off what you thought was broken (speakers probably).

No experience necessary! Apply within

Don't know the the difference between XLR and RCA? If there was an electronics version of a green thumb yours would be brown? Don't fret! Ninety percent of knowing what you're doing is understanding the concept of signal flow, about 8% more is knowing well enough to use "known good" components to verify the integrity of others, the last 2% you can fake or guess at and still be doing very well.

 

Signal flows

Audio signals follow a path that starts at the source which is some type of media. They are extracted from the media by the player and sent through some kind of interconnect cable of either the analog or digital variety to a preamp or processor which among other things handles basic functions like volume control and switching between sources. From there, the audio travels through another set of interconnect cables and arrives at a power amplifier. The amplifier does just that to a level suitable to push speakers hard enough so that they can transform that signal into sound. Simple enough, and we already knew all this. Some systems add levels of complication like transforming digital signals into analog, stripping video off and sending it separately to a display, etc. Fundamentally though, they still follow the rules of signal flow.

 

Basic 2-channel system description

Let's look quickly at a very simple one-source system that's all analog and has only 2 speakers. This system has only 4 basic elements: CD player, preamp, power amp, and a pair of speakers. In between each is cabling of the appropriate type. The signal is born when the CD is read by the CD player. The CD player puts out a left and right signal on left and right interconnect cables respectively. Signal flows down the interconnects into the preamp. As long as the preamp is set to listen to the CD player, the signal will pass through it and down along another set of left and right interconnects to the power amplifier. The power amp does it's thing and sends the well amplified signal on to each speaker, left and right respectively, where the electrical signal is transduced into sound.

 

Known Good

It's always a good idea to have some "known good" components around to use for troubleshooting. Known good simply means that you are certain beyond any shadow of a doubt that the piece of gear (speaker, amp, etc) works as advertised. Known good gear doesn't have to be known good quality. To the contrary, the best known good gear is expendable. If you blow it up, you don't want it to be missed. Many of us already have known good gear. It's the old stereo from college that's at the bottom of the pile in the basement. Known good pieces are useful really just to substitute in place of suspect units in your good stereo to see if signal is passed or not. If you don't have extra gear laying around, you are free to use gear in your system that IS functioning properly. Substitute the right speaker for the left, use the right channel of the amp instead of the left. It may be more convenient anyway. In the example below, we're trying to figure out if a speaker is actually dead. You could replace the suspect speaker with a known good one. If the test speaker plays, you know the other one must be dead.

 

Last minute words of advice

Before we dive into our example system below and try and figure out where the issue lies, permit me to offer a few words of advice.
         

1. It's most effective to troubleshoot from one end of the signal path to the other. It doesn't matter which end you start with, just don't start in the middle.

2. Turn gear off before you start messing with connections. The best way to blow a speaker is to send a gigantic pop through the system when you pull out a live signal cable.

3. Keep the volume low. It doesn't need to be very high for you to know whether or not you've fixed a problem. Besides, you'll forget you had it cranked until after you press play.

4. Only change one thing and test one thing at a time. Otherwise, you haven't narrowed down the problem any further.

 

Trouble is...

One evening after a particularly rough day of meetings with clients you don't like, you come home to a rarely empty house and have a chance to listen as loud as you want to your favorite music that your spouse despises. When you fire it up, the left speaker is silent. What a fine way to end a fabulous day.

Since the right speaker is playing and the left one is not, we know we haven't done something silly like selected the wrong input on the preamp. Starting at the speaker end, we check and make sure the speaker cables are securely fastened to the speaker. If so, we look at the other end of the cable and make sure it's securely fastened to the amp. If so, look at the left interconnect cables and make sure they're still hooked up. Checking connections is really just a sanity check. Unless you've got kids or cats, cables are not likely to just fall out of place.

 

Step by step - don't skip ahead

Starting at the speaker end of our signal path, disconnect the speaker cable from the back of both speakers. Connect the left speaker cable to the right speaker. The right speaker is known good, so if once it's hooked up to the left channel signal path, you get sound you can confidently say that the left speaker has failed and needs service. If however, the right speaker now falls silent, the problem must lie somewhere else in the left channel signal path. Hook the speakers back up to their correct cables (left to left, right to right) and move on up the signal path.

Again, since cables are highly unlikely to fail unless messed with, we can move past the speaker cables to the amp. Check to see if the left channel of the amp is working move the right channel interconnect cable to the left channel amplifier input. Do you get sound out of the left speaker now? If so, your left amplifier channel works just fine and you'll need to move up the signal path yet again. If no sound, you must have a dead left channel in your amp.

 

Situational advice

If you get noise or hum in your speakers, you might want to start troubleshooting at the source end of the path. When you select different sources on the preamp does the noise or hum remain constant? If not, the source component needs service. If so, try unhooking the signal input cables from the amplifier. So, break the signal path at the amplifier input. Then power your amplifier up with no input connected to see if the noise remains. If so, the noise must be generated by the amp, therefore the amp needs service. If all is quiet as it should be, the hum is being generated by the preamp which needs service.

There is one exception to the above. Sometimes hum is created by "ground loops" which can be caused by interactions between pieces of electronics rather than the electronics themselves. Google "audio ground loop troubleshooting" for help there. you'll still use your signal flow knowledge, but a bit differently. Ground loops rarely creep up at random. More likely, they are discovered when new systems are setup for the first time.

Surround sound systems or distributed audio systems can be troubleshooted in the same way as our simple stereo system above. Whole house audio systems are much more laborious as you might guess since there are so many more paths the signal can take. The fundamentals remain the same however.

 

Voice of experience

Sometimes gear does randomly fail, but more often there is some known stimulus that causes the failure. Examples are particularly raucous listening sessions that overstress amps or speakers. Making or breaking connections between components while they are powered on can wreak havoc. Static electricity can also cause problems especially among digital components. Cats seem to take a shine to speakers. Claws can work speaker cones over in no time. Consider these or other noticed anomalies when you're troubleshooting. You'll get to the root of the problem much more quickly. I know it sounds obvious, but I'm always amazed people that don't draw the connection between last weekend's party and this week's problem stereo. It's nothing to be embarrassed of, it happens!

But, don't let guesses and assumptions get in the way of good troubleshooting technique as described above. You may miss an otherwise obvious clue. For example, don't assume that since you've played the speaker louder than that before, it didn't blow this time. It may not be your fault, the speaker may have a defect that's unrelated to your playback level. Don't dismiss a component as the source of the problem unless you can logically prove yourself right by troubleshooting in an orderly fashion.

 

Best wishes for a fail-proof system

Hopefully you won't need to exercise you new found technical know-how anytime soon, but don't be afraid to try and track down problems yourself if need be. Identifying a problem isn't as difficult as fixing it. Some folks just don't want to fool with troubleshooting themselves, but if you've made read this far, that probably isn't you. Give it a shot. You may not only surprise yourself, but will likely lessen your system downtime by providing the repair guys some much appreciated detail about the true nature of the problem.


Gary Dayton
Customer Service/Technical Support Manager

Click HERE for periodic updates about THIEL

THIEL Loudspeakers
1026 Nandino Blvd.
Lexington, KY 40511
Tele: 859-254-9427; ext. 203
Fax: 859-254-0075
gdayton@thielaudio.com
www.thielaudio.com


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