Polk PA4A Oscilloscope Testing

[FloJet]

I am using an app (f Generator PRO V4.1.0) to generate the test tones on the fly. I believe this is outputting 160 Kbps MP3 over the USB connection. I do believe that clipping is occurring earlier at 40hz but the volume control on the PA4a is far from linear and closer to exponential which is why I likely did not observe that. Final speaker level out to all speakers being driven must be tested. sound is produced be sending alternating current to the speakers. The frequency of that alternating current is what dthe magnet reacts to causing the speaker to move in and out. More voltage means the magnet will produce more push and pull at that frequency. More voltage = louder to a point. I tested the speaker level outs on the Polk head unit because I am using that to drive some of the speakers otherwise it is not needed. I did run new 14 or 12 awg knukonceptz speaker wire to all of the speakers. My testing so far has been done in my driveway with the bimini stowed. I would love to test a ws420 to see what gains can be had but have not committed to buying one as of yet. I really like the large Connext jog dial for controlling volume (quick to crank it when once the boarder is up and engines are high rpm then turn quick to reduce the volume once throttled down) all without having to look.

Ok gotcha. Makes sense. I did forget you did run new wiring. I do believe 160 kbps is too low of sample rate to tune with tho but you probably know better on that side than me. Before I started using .WAV files, I was tuning my system using mp3 320 kbps at 90-92% volume. The cleaner .WAV tone gave me slightly higher volume to tune with. I would love to send you the file and see if you get different results with that if you ever up for it lol.

My volume control only comes from my phone. My WS420 volume never changes when I get on the water, Connext is always locked in at 95% volume and I only manage my music from my phone and watch. Every once in awhile I will mess with my sub volumes to compensate for the music I'm listening. This is why I tune the WS420 at full tilt.

 

[Mainah]

Ok gotcha. Makes sense. I did forget you did run new wiring. I do believe 160 kbps is too low of sample rate to tune with tho but you probably know better on that side than me. Before I started using .WAV files, I was tuning my system using mp3 320 kbps at 90-92% volume. The cleaner .WAV tone gave me slightly higher volume to tune with. I would love to send you the file and see if you get different results with that if you ever up for it lol.

My volume control only comes from my phone. My WS420 volume never changes when I get on the water, Connext is always locked in at 95% volume and I only manage my music from my phone and watch. Every once in awhile I will mess with my sub volumes to compensate for the music I'm listening. This is why I tune the WS420 at full tilt.

I am sure the app is capable of outputting 320 kbps but my guess is that the usb connection on the Polk is choking it to 160 kbps. That is just a guess. Could be a .wav as well all depends on the Polk headunit. I am sure it is the best the the Polk can handle. The phone output is the cleanest it is going to get so keeping the phone cranked and adjusting from there is your best bet for cleaner output but human interface plays an important role too.

 

[FloJet]

I am sure the app is capable of outputting 320 kbps but my guess is that the usb connection on the Polk is choking it to 160 kbps. That is just a guess. Could be a .wav as well all depends on the Polk headunit. I am sure it is the best the the Polk can handle. The phone output is the cleanest it is going to get so keeping the phone cranked and adjusting from there is your best bet for cleaner output but human interface plays an important role too.

Oh ok. So the .wav is at 1535 kbps so that high of quality should give slightly higher results as that's a fairly clean file.
What I can't get my head wrapped around is I have music files that sound way better at 160 kbps than 320 kbps. Yes majority of the time the 320 kbps is and should be the best but I've seen it otherwise. The program I use states what's the recording sample rate so technically the 160 kbps should never be louder than the 320 kbps? This is where I believe the source recording is critical. But because of this I will not tune my system now without at least .wav or cd quality file which is almost impossible now days to get lol.

When I setup my first system on this boat in 2016, I tuned it at 320 kbps, now with the .wav, I'm getting louder tuning volume than before. But I don't know if my overpriced Audioquest RCAs have anything to do with it. Lol.

 

[Mainah]

Oh ok. So the .wav is at 1535 kbps so that high of quality should give slightly higher results as that's a fairly clean file.
What I can't get my head wrapped around is I have music files that sound way better at 160 kbps than 320 kbps. Yes majority of the time the 320 kbps is and should be the best but I've seen it otherwise. The program I use states what's the recording sample rate so technically the 160 kbps should never be louder than the 320 kbps? This is where I believe the source recording is critical. But because of this I will not tune my system now without at least .wav or cd quality file which is almost impossible now days to get lol.

When I setup my first system on this boat in 2016, I tuned it at 320 kbps, now with the .wav, I'm getting louder tuning volume than before. But I don't know if my overpriced Audioquest RCAs have anything to do with it. Lol.

The issue is that there are two different classes of usb audio and three different types of communication for each of those types the lowest common denominator will determine the quality. If paying a file at a very high rate on a system that does not support it then it needs to be compressed by the root source. This on the fly compression may not be as good as being done before hand. I could test this by listening in on the usb connection with one of digital oscilloscope channels but since there are varied file formats and qualities in the music apps I am leaving it at it is what it is. If I were building a competition system this is something I would want test and optimize. I am past feeling the requirement to win at anything. Don't get me wrong I do enjoy winning and strive for success but I have learned there is always someone better and there is more to life than bringing home trophies or claiming I am the best. As for my kids I still do encourage the competitive attitude and winning so they can learn how to be their best. A bit derailed I know but just my way of saying this can be taken too far and I am already at that point as it is. For those that want to take it further please do post results.

 

[Jgorm]

I think the loudness or bass boost is useful at low volumes, but agree it doesn't work well at high volume.

 

[FloJet]

The issue is that there are two different classes of usb audio and three different types of communication for each of those types the lowest common denominator will determine the quality. If paying a file at a very high rate on a system that does not support it then it needs to be compressed by the root source. This on the fly compression may not be as good as being done before hand. I could test this by listening in on the usb connection with one of digital oscilloscope channels but since there are varied file formats and qualities in the music apps I am leaving it at it is what it is. If I were building a competition system this is something I would want test and optimize. I am past feeling the requirement to win at anything. Don't get me wrong I do enjoy winning and strive for success but I have learned there is always someone better and there is more to life than bringing home trophies or claiming I am the best. As for my kids I still do encourage the competitive attitude and winning so they can learn how to be their best. A bit derailed I know but just my way of saying this can be taken too far and I am already at that point as it is. For those that want to take it further please do post results.

Makes sense. Not worth all that extra time at times. Thanks for the results you posted

 

[Brian McIver]

Great 4+ year old post. I was looking for pa4a info after installing 2 JL m800/8 and to run the 4 pair m650, 2 m880 tower and an m10 sub. Previously I was running these speakers on 2 Polk Audio amps, 4000.4 and a 5000.5 successfully. I remember tuning them a number of different ways and I do not remember which method I settled on last, but it worked fine. however I followed the JL method of setting the volume at 75% and I couldn’t get the desired output voltage on the bridged sub channel. Strangely, I remember having the same problem tuning the polks and I’m sure I set the head unit volume to 95 percent also. If you are still here @Mainah , or anyone willing to chime in, I have a couple questions:

The JL manual states the input sensitivity can be set to Low (200mv to 2v) or High (800mv to 8v). If the head unit is producing 2.88v as you found, are you setting it to high? This was WITH loudness on I think you said, and in the final tune did you have that off?

my main problem having it tuned with the volume 75% and loudness off and eq flat, I’m getting a fine buzz at listenable levels and I’m ony getting the volume up to 20-30% before it gets too loud. Perhaps the gain is set too high with the volume set at 75%? I may just drop into the helm storage and pull the oscilloscope out ditching the JL method. Can’t hurt, but I’m interested to hear everyone’s thoughts.