My first autotuba build (with a question)

[climbikejk]

Jude here. Well I finally did it. After buying the plans probably 2-3 years ago, I finally finished one autotuba (the other is about half finished). The finished one still needs some exterior cosmetics, but I couldn't wait to start listening to it. I first hooked it up to a small Sherwood amp. I sent all the 50Hz and under tones to it (from an EQ off the Sherwood), while the other channel played 80Hz and above. It sounded impressive and I was measuring ~110dB right at the mouth around 50% volume.

So the next thing I did was put the autotuba in my car. The previous weekend I installed the oft recommended Blaupunkt THA-1250 PnP 1 Channel 600W Amplifier. I'm an electrical engineer and former SPL competitor, but that was about 20 years ago, (2 Kicker C-12s and a Sentrk amp, I was hitting 133dB. I never said I was a good competitor ) so I'm confident I installed everything correctly.

Here's my problem. I'm surprised how much I have to turn up the factory radio in order to hear anything from the autotuba. I've set the gain on the amp to max, I've set the HP filter to max, and I've set the LP filter to min (~50Hz). Now I know the autotuba is presenting an 8ohm load to the amp, but still.... The one place I think I might be experiencing a problem is my line level converter. I've always hated these things, but w/o upgrading my radio I'm stuck with using them. The one I'm using is http://www.bestbuy.com/site/Fierce+Audi ... cp=2&lp=13. It was the only one that the Best Buy near me had at the time. I've played around with the pot, but all it does is reduce the sound from the autotuba, so I'm leaving where I'm hearing the most from the AT. I suspect I'm getting around 80-90dBs in car.

I took my voltmeter and set it to AC and measured the voltage across the speaker terminals while playing some low bass music. I was ranging 0.8 - 1.0 VAC. I'm pretty sure I've read other people seeing ~5VAC.

Any ideas?

[Radian]

Flip-flop your HP and LP filter settings. They're working against one another, a stop-filter if you will. Set HP (subsonic filter) to minimum for now, And the LP (or crossover freq) to anywhere's from 50-80 to taste. That should bring up your voltage considerably.


Glad to see you made it over here!

Cheers,

Radian

(aka. TerdFurg3zon)

[Tom Smit]

+1

[climbikejk]

Wow, thanks for the quick reply (disregard my youtube question ). I'll definitely try that.

[Radian]

Make sure you turn the gain down around to 1/2 ~ 1/4 also before you power back up....don't want to blow the darn thing up on the first day out.

[climbikejk]

Bleep me if you have to, but Holy Shit, What a difference! Here I was thinking I'll push all the HF away from the driver so it won't have to deal with them. Wow, now I am really impressed. Before I played any music, I unplugged the remote bass knob (which I was maxing out before) and I turned the input voltage level down to min. While playing some music I turned up the voltage level to about half and had to turn down the volume from my radio by about 25%.

Thanks guys!