Monitoring Laboratory
Until now KDX has run slim with exclusively monaural sound for speech quality monitored wirelessly on radios.
However, because KDX carries a small amount of classical music recorded in state-of-the-art stereo, we want to install a laboratory quality speaker monitoring array on a small tower located near the control desk.
Because the speakers will be near the operator relatively little amplifier power is needed, and we will determine the exact power needed by matching to the power-handling capacity of the loudspeakers which already exist, it will be a matter of locating the speaker spec sheets in our tech file.
At this stage of the project we are estimating that 20-Watts will be the approximate objective and have been shopping around.
Two choices look appealing at this early stage... Lepy Amplifiers are available in the right power range with very attractive pricing. Other amplifiers are comparatively much higher priced; or we have a book showing a DIY circuit in the range 15 - 25 Watts.
When finished the new speaker system will allow switching between stereo and mono so we can judge the phase accuracy of the mixture of left and right channels, very important for common 1-speaker radios.
In Praise of YouTube
There are many videos on YouTube about the Lepy line of low cost 20X2 Watt Amplifiers, and one of them includes precise electronic measurements of these Chinese imports.
Besides many other flaws the actual power of the amplifier measured was about 6-Watts per channel. So much for that quick solution.
I don't completely understand what your doing, but wouldn't an easier and less expensive method to compare the stereo vs the mono version listening experience, to just record the stereo into a combined channel then play it back and comparing it to the original stereo version?
But like I said, I'm not completely understanding why you need to buy new hardware to make the determinations
Simplicity & Efficiency
R.Powers: "Wouldn’t an easier and less expensive method to compare the stereo vs the mono version listening experience, to just record the stereo into a combined channel then play it back and comparing it to the original stereo version?"
That would not be easier, it is a whole extra time-consuming step which delays finding out what could be determined very quickly with the throw of a switch.
I can already do what you mention, Rich Powers, by using Audacity.
Let's start fresh.
I am setting up a close-field monitor with small loudspeakers within about 4-feet of the operator, that can
A.) Monitor Left and Right Channels to judge the quality of the stereophonic effect;
B.) With the throw of a switch monitor the combined L+R Monaural Mix to determine phase compliance.
Every stereo studio should have that capability.
I get radio shows from time to time that contain out of phase material, which you know causes the signal to cancel itself out for mono listeners.
I already have some excellent speakers and only need small amplifiers.
I have a 150-Watt amplifier but that's way too much power for close-up listening.
Important, as I said at the opening I need to look up the actual power rating of these small speakers... I was only guessing when I checked out the Lepy 20 Watt amps.
Maybe today I can go into the files and get the right Wattage.
Ok, I'm still not getting it... Let's forget about using Audacity to record it..
The 150 watt amp you currently have which you say is too much for near field listening.. well, isn't that actually variable with the volume control? If you have the volume low then it's pushing a fraction of that wattage then it's perfectly suitable for near field listening.
So why not from the original audio source (be it a cd, a stream, or actual tuner) put an audio splitter from it's output and feed the same stereo outputs to two different inputs of your existing amp; one input A being unmodified, and input B being wired with an RDL audio combiner (or some similar device) prior to entering the amps B input.
The result is then all you have to do is flip the A/B source switch on the front of the amp back and forth to compare the difference in real time.
I don't comprehend why you would need new equipment to accomplish your objectives.. you probably already have some kind of audio combiner in your junk drawer.
If I'm still not getting the point you are trying to explain, then what exactly is it I'm missing about the quest in the scenario you are expressing?.
Not So Involved
Whoa, hold up, slow down, cool your heels!!
Rich Powers. Listen to me. I am glad you have taken an interest in providing guidance in this situation and I want you to stick with it, so here's the deal:
I'm not talking about all those things you bring into it, like "combining" and "sources" and what not.
There is only one subject under discussion.
The matching of amp & speaker power ratings.
This comment of yours is right on point: "The 150 watt amp you currently have which you say is too much for near field listening.. well, isn’t that actually variable with the volume control? If you have the volume low then it’s pushing a fraction of that wattage then it’s perfectly suitable for near field listening."
Well, sort of, and no doubt a lot of people would do it that way but I have a reason for doing it another way.
I recall reading in a technical book that there are substantial reasons to match amplifier power outputs to speaker power-handling capacity, but that it's NOT a 1-to-1 match. The author said something like,"amplifier should be rated for more power output than the speaker handling capacity", or, maybe it was vice-versa.
Since my memory isn't clear, I need to look it up in a book and also look up the speaker's specs.
Then finally, we will be limited to what kind of products are available in the catalogs.
Oh.. I thought you were just trying to compare the results of a mono conversion to the original stereo presentation of the same audio.. in that you could switch back and forth instantly in real time to more easily determine if the combined channel mono version still provided an acceptable representation of the original source.
Though you may have said it, I just wasn't hearing that the objective was speaker matching.. or whatever.
As Rosanna Danna Nana would say.. never mind.
Busy Working
It's been over 10-years since I last consulted my library of loudspeaker books, papers and articles, but I have most of it now and need to spend time looking for the relevant info.
Meanwhile, on the notion that a 150-Watt power amplifier can be used to drive a low Wattage speaker, here's one reason that's not the best idea:
A burst of excessive sound at the input to the amp could possibly blow out the speaker voice-coil, the voice-coil could be set on fire, and the amplifier output stage could be damaged.
We wouldn't hook the output of a 50 kW RF amplifier to a 30-Watt indoor antenna.