I got a lot of much-appreciate help from some folks in a thread I created about getting a box working. I hope sharing this info might "pay it forward" a little for those who really like to tinker with audio,
Finally got a 'box I've wanted since I was a teen (Panasonic RX5150).
My ears are a little more discerning with age, and I was thinking about ways to make it sound better.
I wanted to keep it stock, so my only option was to digitally EQ the music it was playing.
This will not work for FM (unless you have a whole-property transmitter, which I do) but can be done with mix tapes, digital music (via a line-in), or even with homemade mix CDs. It seems cumbersome, but I'm a tinkerer and it really only took about an hour of time (I've burned hours on things a lot less fun). 'Something to do on a rainy day.
Plus, I'm not a collector, so I only need to do this once.
What you'll need: dB meter (or smartphone with calibrated mic and free dB meter app); Audacity (free download); JRiver Media software (free trail) or similar software with a parametric EQ option (31 band EQ option is next best); 1/8"-to-RCA audio cable (or a blank CD to burn your own test disc)
Process
1. Use Audacity to create your own test tracks. Click "Generate>Tone" to create a sine wave ten seconds long of each of the following frequencies with a 5 second break between each tone (create silence by clicking "Generate>Silence"): 50Hz, 63, 100, 125, 250, 500, 700, 1K, 2K, 4K, 6K, 8K, 10K, 12.5K, 15.5K, 17.5K.
Export to a wav file if you want to burn a test CD.
2. Play the test tones through the 'box (using the audio cable or your burned CD) and measure each frequency with your meter. Create your baseline volume setting by starting with 10KHz. Set the box volume so the 10K tone registers at least 3dB louder than background noise on your meter.
Write down the results.
3. Go into your music software and open the parametric EQ. Pick the "quietest" frequency in the 60-250Hz range from your written results. This is the baseline you'll use to adjust the others ('tis better to reduce than to boost when it comes to EQ).
Using a Q of 2, set negative gains for the frequencies that go above the "target" by more than 1 dB.
If two frequencies right next to each other need to be reduced, split the difference ( ii.e. if 250Hz and 500Hz both need a 2dB reduction, do a 1.5 dB reduction each).
Remember to allow for a normal high-end rolloff.
4. Apply the EQ to some music you are very familiar with (as played through a quality audio system) and play it through the 'box.
You can also apply it to the test tones and measure the difference it makes.
If you are satisfied with the changes, you can apply it to CDs that you burn for 'box use, apply it to tapes as you record them, or to all music you put on a digital player (I have a dedicated old phone I can use as a source for the Panasonic).
i'd bet a nickel there is a tinkerer out there who would put a miniDSP inside a box and apply it to the signal chain.
What surprised me about this test was that (despite what I've heard about boombox tweeters), my spectrum analyzer was picking up output from the Panasonic all the way up to 20Khz. It was low level, but it was definitely there.
What didn't surprise me (based on what this this sounds like) was the sloppy upper mid-bass. It dropped 5 dB between 63 and 125Hz, shot up 8dB between 125 and 250Hz, then dropped 6dB between 500 and 700Hz. Another problem area was a 7dB dropoff from 4 to 6KHz. From 6KHz on up, the roloff was actually pretty consistent.
Smoothing that mess out made a huge difference.
I'll try to post a picture of the spectrum analysis plot if I can.
Finally got a 'box I've wanted since I was a teen (Panasonic RX5150).
My ears are a little more discerning with age, and I was thinking about ways to make it sound better.
I wanted to keep it stock, so my only option was to digitally EQ the music it was playing.
This will not work for FM (unless you have a whole-property transmitter, which I do) but can be done with mix tapes, digital music (via a line-in), or even with homemade mix CDs. It seems cumbersome, but I'm a tinkerer and it really only took about an hour of time (I've burned hours on things a lot less fun). 'Something to do on a rainy day.
Plus, I'm not a collector, so I only need to do this once.
What you'll need: dB meter (or smartphone with calibrated mic and free dB meter app); Audacity (free download); JRiver Media software (free trail) or similar software with a parametric EQ option (31 band EQ option is next best); 1/8"-to-RCA audio cable (or a blank CD to burn your own test disc)
Process
1. Use Audacity to create your own test tracks. Click "Generate>Tone" to create a sine wave ten seconds long of each of the following frequencies with a 5 second break between each tone (create silence by clicking "Generate>Silence"): 50Hz, 63, 100, 125, 250, 500, 700, 1K, 2K, 4K, 6K, 8K, 10K, 12.5K, 15.5K, 17.5K.
Export to a wav file if you want to burn a test CD.
2. Play the test tones through the 'box (using the audio cable or your burned CD) and measure each frequency with your meter. Create your baseline volume setting by starting with 10KHz. Set the box volume so the 10K tone registers at least 3dB louder than background noise on your meter.
Write down the results.
3. Go into your music software and open the parametric EQ. Pick the "quietest" frequency in the 60-250Hz range from your written results. This is the baseline you'll use to adjust the others ('tis better to reduce than to boost when it comes to EQ).
Using a Q of 2, set negative gains for the frequencies that go above the "target" by more than 1 dB.
If two frequencies right next to each other need to be reduced, split the difference ( ii.e. if 250Hz and 500Hz both need a 2dB reduction, do a 1.5 dB reduction each).
Remember to allow for a normal high-end rolloff.
4. Apply the EQ to some music you are very familiar with (as played through a quality audio system) and play it through the 'box.
You can also apply it to the test tones and measure the difference it makes.
If you are satisfied with the changes, you can apply it to CDs that you burn for 'box use, apply it to tapes as you record them, or to all music you put on a digital player (I have a dedicated old phone I can use as a source for the Panasonic).
i'd bet a nickel there is a tinkerer out there who would put a miniDSP inside a box and apply it to the signal chain.
What surprised me about this test was that (despite what I've heard about boombox tweeters), my spectrum analyzer was picking up output from the Panasonic all the way up to 20Khz. It was low level, but it was definitely there.
What didn't surprise me (based on what this this sounds like) was the sloppy upper mid-bass. It dropped 5 dB between 63 and 125Hz, shot up 8dB between 125 and 250Hz, then dropped 6dB between 500 and 700Hz. Another problem area was a 7dB dropoff from 4 to 6KHz. From 6KHz on up, the roloff was actually pretty consistent.
Smoothing that mess out made a huge difference.
I'll try to post a picture of the spectrum analysis plot if I can.
