2. tech-talk
  3. 1067441853

Inactive speakers in the room...any effect?

A recent thread degenerated into a discussion about whether an inactive speaker in the listening room affects the sound of active speakers. I should have been more tactful, and called it a "hypothesis" instead of a "myth".

Now, a hypothesis can be proven by analytic means or by experiment. This particular hypothesis, from the analytic approach, is very unlikely to be true. So, we go on to an experiment.

A listening test was described where a group of listeners were unanimous in saying that sound quality was degraded by an inactive speaker. (By the way, I don't understand why, if there were any effect, it would have to be a degradation rather than an improvement).

However, to be acceptable as a proof, the experiment would need to be done as follows:
1. The inactive speaker should be introduced and removed from the room in such a way that the subjects, and the person conducting the experiment, cannot tell if it is in or out.
2. The listening test should be performed a number of times. A dozen might be sufficient. More would be better, but the subjects would get bored and results would be degraded.
3. The subjects should record their observations (Speaker IN/Speaker OUT) in such a manner that they do not know how the others are voting.
4. The results must be tabulated and analyzed in a statistically valid way.

I doubt that the reported experiment was done this way. It apparently convinced the subjects, but does not constitute a proof acceptable to an objective non-participant like me. Lacking a valid experiment, I must rely on the analytic approach, and find the hypothesis untrue.

Another game that would be fun would be to conduct the experiment in the manner that I suspect it was done, where everyone knew when the speaker was in or out, but use a speaker that, unknown to the subjects, has had its cones immobilized with glue and the vent (if any) closed off.
I think I know how that would come out if the subjects were believers. (Or, for that matter, if they were nonbelievers). This exercise would indicate how much confidence should be put in the experiment that was done.

Are we having fun yet?
eldartford

Showing 5 responses by eldartford

eldartford OP
4,262 posts
 
Believers...What you are saying is that a "room treatment" device having only about 1/2 square foot of active area has a significant effect. If this is so, why don't the room treatment merchants design a box with a passive radiator (or an active device) to accomplish their purpose without acres of foam on the walls.

By the way two things I can accept.
1. An inactive speaker placed immediately adjacent to the active speaker will function as a passive radiator, and will have some impact.
2. A small audio shop listening room with the walls lined with dozens of speakers would sound different if they were all removed.

A telephone! Now I know you are spoofing me.
eldartford OP
4,262 posts
 
I would be delighted to participate in such an experiment if there is anyone near western Mass who is interested. An audio club perhaps?
eldartford OP
4,262 posts
 
Sidssp...Yes I agree that in close proximity to the active speakers they would function much like passive radiators (which, by the way, some people think are a bad idea).

I can't do that particular experiment because the walls behind my three MG1.6 speakers are already occupied by embedded multiple subwoofer drivers that are very much active.

I remain to be convinced that a couple of inactive box speakers at the opposite end of the room would have any audible effect. As for a telephone...

Regarding helmholz resonators...they were used during WW1, connected by tubes to a set of earpieces, to detect approaching aircraft long before they were detectable by other means. Poor man's radar. It worked.
eldartford OP
4,262 posts
 
Sean...Your point about subtractive differences is very well-taken. The best known example of this is that a performance hall has very different acoustic characteristics when it is full of people vs when it is empty.

Of course speakers function as microphones, many (if not most) handheld communication devices make the speaker do double duty. Just for fun I will measure the output of a box speaker/microphone at some measured SPL. But what to do with this data? Perhaps I should express the signal in terms of the SPL which the speaker would produce if that voltage were applied. The idea is to assess whether the effect, which certainly exists, is of any practical significance.
eldartford OP
4,262 posts
 
Linn is the "certain British manufacturer" who tried to pressure dealers into having a dedicated Linn room. The extra speaker thing was part of it.
More to discover