O-Scope Question

[nathanotis]

Somethings off.

Oh, yes. I am fully aware. I know what it SHOULD look like and how to read a clipped signal. I just don't know enough to know what the problem is. So, I'm trying to clean up the power source, and the connection, and we'll see what happens next.

 

[nathanotis]

I currently have my head unit completely flat. No EQ, no effects.

I AM running crossover from the head unit, however. HPF to the mains (2 pair 5.25") @ 100 Hz, 12 dB/octave slope. LPF to the powered sub @ 80, 18 dB/octave slope.

1. Should I clear the crossover settings while testing the RCA outs at the head unit for clipping?

2. Later, we can discuss advisable crossover settings.

I never mentioned this... This is a Jeep Wrangler. I like clear sounding music, but I have realistic expectations. I run top down and doors off pretty much all the time if it's not raining. Road noise and wind noise is REAL. I haven't built an audiophile system because it would be wasted in this application (IMO). But I want it to sound good.

Just thought I'd throw that out there.

 

[Firewalker]

I've always made sure that everything is set to zero and no boost, no nothing when setting gains, only thing I have up is the bass knob to full along with the volume set to 75% or so of the maximum volume it can go. Nothing crossed over at all just a flat eq across the board. But I know others that do it differently. Was always told to do it with a flat eq.

 

[dangerdan86]

I currently have my head unit completely flat. No EQ, no effects.

I AM running crossover from the head unit, however. HPF to the mains (2 pair 5.25") @ 100 Hz, 12 dB/octave slope. LPF to the powered sub @ 80, 18 dB/octave slope.

1. Should I clear the crossover settings while testing the RCA outs at the head unit for clipping?

2. Later, we can discuss advisable crossover settings.

I never mentioned this... This is a Jeep Wrangler. I like clear sounding music, but I have realistic expectations. I run top down and doors off pretty much all the time if it's not raining. Road noise and wind noise is REAL. I haven't built an audiophile system because it would be wasted in this application (IMO). But I want it to sound good.

Just thought I'd throw that out there.

I agree with Coolhand20th, turn everything off and run a completely flat curve. I found on my kenwood that i can run a +1 on the s/w and it doesn't clip and gives me 5v, so make sure to check that as well. You want the most gain the earliest on, so figure out what the safe maximum is for everything at the head unit first.

I've always made sure that everything is set to zero and no boost, no nothing when setting gains, only thing I have up is the bass knob to full along with the volume set to 75% or so of the maximum volume it can go. Nothing crossed over at all just a flat eq across the board. But I know others that do it differently. Was always told to do it with a flat eq.

Funny you mention a bass knob, i went through and did a ton of measurements on my head unit and the helix pro mk2, was getting ready to move onto setting the amp gains, and realized that the URC.3 connected to the helix was set at about 75% for the main and S/W had to go back and redo all the helix measurements.

 

[nathanotis]

PROGRESS!

If you recall, I was suspect of my universal power block I had running my o-scope. Long story short, that was DEFINATELY introducing a lot of noise to my readings. This week I received a new 9v power supply and the BNC to RCA adapter for my o-scope. I had clean .wav test tones from Kicker. I headed onto the garage to try again.

First I tried playing the wav files from my MacBook to the AUX on the head unit. I had to CRANK the V/Div on the scope to see sine wave at all. Realized the volume on the computer was probably too low. Turned it up and it helped, but the readings still seemed low. I ditched the computer and switched back to using the test files on a USB stick.

For the first time since I started this process, I had the same smooth sine wave I see in all the videos I've been watching. Still a little glitching in the o-scope display (I'll wager the 9V battery connector would have yielded cleaner results), but what I had was workable!! The sine was clear, the settings were in the correct range, the frequency showing on screen was correct and the o-scope reacted appropriately to volume changes at the head! I found myself zooming in on the sine wave to really study the shape of the tips but in the end, I confirmed on the scope what I could hear with my ears. I now has a max volume for my head unit... ON TO THE AMP GAINS!

I switched back to the alligator clips, disconnected all the speakers and connected directly to the outputs on the 4ch amp. The same clear, positive results presented themselves and I was able to easily dial in the max gain for the front, and then the rear speakers. It was so easy I couldn't believe it had taken so long to get to this point. POWER SUPPLY MATTERS!!

I have a nagging suspicion that while I was setting amp gain, I wasn't at max, distortion free volume on the head unit, so I'm going to re-check that tomorrow. But it'll be a quick thing.

I ran out of time before being able to dive into the powered sub. What's the best way to measure the gain setting there?

 

[dangerdan86]

PROGRESS!

If you recall, I was suspect of my universal power block I had running my o-scope. Long story short, that was DEFINATELY introducing a lot of noise to my readings. This week I received a new 9v power supply and the BNC to RCA adapter for my o-scope. I had clean .wav test tones from Kicker. I headed onto the garage to try again.

First I tried playing the wav files from my MacBook to the AUX on the head unit. I had to CRANK the V/Div on the scope to see sine wave at all. Realized the volume on the computer was probably too low. Turned it up and it helped, but the readings still seemed low. I ditched the computer and switched back to using the test files on a USB stick.

For the first time since I started this process, I had the same smooth sine wave I see in all the videos I've been watching. Still a little glitching in the o-scope display (I'll wager the 9V battery connector would have yielded cleaner results), but what I had was workable!! The sine was clear, the settings were in the correct range, the frequency showing on screen was correct and the o-scope reacted appropriately to volume changes at the head! I found myself zooming in on the sine wave to really study the shape of the tips but in the end, I confirmed on the scope what I could hear with my ears. I now has a max volume for my head unit... ON TO THE AMP GAINS!

I switched back to the alligator clips, disconnected all the speakers and connected directly to the outputs on the 4ch amp. The same clear, positive results presented themselves and I was able to easily dial in the max gain for the front, and then the rear speakers. It was so easy I couldn't believe it had taken so long to get to this point. POWER SUPPLY MATTERS!!

I have a nagging suspicion that while I was setting amp gain, I wasn't at max, distortion free volume on the head unit, so I'm going to re-check that tomorrow. But it'll be a quick thing.

I ran out of time before being able to dive into the powered sub. What's the best way to measure the gain setting there?

Glad to hear you got it figured out.

What powered sub are you using? You should be able to do it the same way you did the others. Use a 50hz, but use the -5db file.

 

[nathanotis]

Glad to hear you got it figured out.

What powered sub are you using? You should be able to do it the same way you did the others. Use a 50hz, but use the -5db file.

This is a Sound Ordnance B-8PTD from Crutchfield. I guess it's their house brand. I can already tell I might be replacing it, though. Even with the crossovers in place, it seems muddy and doesn't pack much of a punch. I prefer "tight, clean and punchy" to what it seems to be putting out currently.

To this point, I'm accustomed to taking measurements at the output of a device. Since the sub is the end of the chain, where do I measure?

Or do I just listed to the 50Hz test tone and do it by ear? (I'd prefer to measure if possible).

 

[dangerdan86]

This is a Sound Ordnance B-8PTD from Crutchfield. I guess it's their house brand. I can already tell I might be replacing it, though. Even with the crossovers in place, it seems muddy and doesn't pack much of a punch. I prefer "tight, clean and punchy" to what it seems to be putting out currently.

To this point, I'm accustomed to taking measurements at the output of a device. Since the sub is the end of the chain, where do I measure?

Or do I just listed to the 50Hz test tone and do it by ear? (I'd prefer to measure if possible).

Hmmm, I'm not really sure how you would measure the output of the integrated amp. The only way I can think of is to pull the speaker out of the enclosure and get to the amp terminals.

If they used insert nuts to secure the sub to the box it shouldn't be too bad to remove.

Maybe look online to see if there's a teardown instructions somewhere.

 

[dangerdan86]

Looks like you might be able to pull the heatsink off the side and access the amplifier.

 

[nathanotis]

Hm. I may have to pull it apart. With a 50Hz tone I hear what I think is distortion before I get to 30% of the level knob. And it's NOT loud enough... I'm interested to see what the scope says.

Planning to try by ear in a minute with a 60Hz tone ... Maybe the enclosure was vibrating?

 

[Firewalker]

Most people use 40hz test tones on the subwoofer so try that as well. And yeah I would take it apart and make sure everything was nice & tight on the screws. Who knows if something from the factory is loose. Plus you can always return it for something better.

 

[nathanotis]

10-4, will do.

 

[nathanotis]

Hey all. Long time no post... It seems everything in the powered sub is snug. At this point I'm forced to admit I don't know what I'm listening for... I turn up the head unit to it's distortion free limit, play a 40, 50 &/or 60Hz signal via USB thumb drive and turn up the level on the sub... I don't know if what I'm hearing is distortion or not... Is there anywhere I can find an example in a video or something?

Thanks.

 

[dragon.breath 10+ year member]

Setting the gain by ear is done playing music. Not tones.

 

[Firewalker]

Lot's of people do 40hz test tones by multimeter or O-Scope when doing a subwoofer or a 1K hz for tweeters and what not. Done it that way for years and never an issue. Some prefer doing it by ear, did it that way in the '90s. Both work just fine all depends on what you prefer. Or they use said test tone with a DD-1 like a few people I know do.