Autotuba almost....

[WB]

I wonder what the Untitled freq marks are?

The other peak is at 66.8 Hz.

[Tom Smit]

Near got the air leaks taken care of...bad sealing at the driver mounting screw holes. I fabbed up some hold-down clamps (4), and the gasketing that I installed didn't cover the holes, so I hot-glued the holes....and that took care of the "wheezing?" noise. I still have a couple of whispers of air leak at the covers (which I will rectify).
There is one thing that bothers me. Even though this AT does a beautiful, wonderful job for whatever seat position one is sitting, when listening directly behind the mouth, one can hear a "phwack" on the impacts of kick or bass notes. The volts are typically peak around 8-9 at those points. On sustained notes, there is no problem (6-7 volts?). I do have the brace notched semi-circular at 1" depth and 1" across. Any ideas? Thanks.

[Bill Fitzmaurice]

Near got the air leaks taken care of...bad sealing at the driver mounting screw holes. I fabbed up some hold-down clamps (4), and the gasketing that I installed didn't cover the holes, so I hot-glued the holes....and that took care of the "wheezing?" noise. I still have a couple of whispers of air leak at the covers (which I will rectify).
There is one thing that bothers me. Even though this AT does a beautiful, wonderful job for whatever seat position one is sitting, when listening directly behind the mouth, one can hear a "phwack" on the impacts of kick or bass notes. The volts are typically peak around 8-9 at those points. On sustained notes, there is no problem (6-7 volts?). I do have the brace notched semi-circular at 1" depth and 1" across. Any ideas? Thanks.

That's far too little voltage for excursion to be a problem. It could be harmonic distortion, especially if it's only heard on the mouth axis. And it could indicate the amp isn't getting adequate supply current, a larger supply wire gauge might help.

[Tom Smit]

And it could indicate the amp isn't getting adequate supply current, a larger supply wire gauge might help.

This could be the problem. In my case it actually would be the amp ground wire since the amp is fed 2 times 14 gauge from the battery. Thanks Bill!

[Tom Smit]

Well, today was a holiday here in the Great White North, and my family had a picnic and I finally got to show off my AT to my Dad. I down-loaded some pipe organ music to use as a demo, and got Dad in my wagon. He liked the sound, and the depth. So I went to show him the finished product and discovered that the Rockford fosgate was running! I apologized and asked him if he would mind listening again, but this time to the AT. Sure, he said. After half a minute he said that it was a really nice sound...nice and clear. Not sure what he exactly meant, I asked if he meant the sub sound...and he said 'yes'! The notes were nice, clear and clean...and he doesn't know much about the different aspects of music! (his words).
This past Friday night I was alone at work so I listened back and forth between the Rockford and the AT for about 5 hours. What I noticed was that the Rockford had good punch for the kick drum but the bass notes were somewhat hiding. On the AT, all the bass notes came through no problem. And this was before I repaired a couple of air leaks.
My favourite third son took his amp because he moved on to college, so now I have to try find one somewhere and do without my AT

[Rickisan]

Pretty easy build, so I plan to build another AT to replace the one that finally made it in to my daughters car

And as you probably already know the AT is so efficient pretty much any old amp will push it to adequate volume levels

[Scott Brochu]

And as you probably already know the AT is so efficient pretty much any old amp will push it to adequate volume levels

I second that......I still have the bass booster only at 1/4 turn and the gain at 1/3.
It is such clean bass it is unreal. I have never heard bass this smooth and punchy when it needs to be. At all levels.

[Tom Smit]

I'm back! with an update. My favourite third son has moved back home from college, and brought a different amp with him...Soundstream EGA900D. I just got it installed and figure that it could put out 120 Watts into 8 ohms. While making adjustments on the gain with a song (DnB?) and actually was hitting 30 volts at times, and then falling down to 20ish volts. I figure I can keep the amp gain up, and back down the sub level on the head unit since I don't have a limiter. I also thought about running a small gauge pair up to the car front to install a DVOM to watch the speaker voltage to keep it limited to 15 volts.
So, what's it sound like? Great! Like I always wanted. My favourite third son says it definitely keeps up with his 12" Rockford (but not his 2x12). At 15 volts, I can see how some how some would desire to have a second AT. But even still, I had a quick listen to a couple of songs of a Bob Marley collection CD and the bass was very well anchored and defined.
I have finally reached the point of satisfaction with my AT.

[RubiconProSound]

...There is one thing that bothers me. Even though this AT does a beautiful, wonderful job for whatever seat position one is sitting, when listening directly behind the mouth, one can hear a "phwack" on the impacts of kick or bass notes... Any ideas? Thanks.

... it could indicate the amp isn't getting adequate supply current, a larger supply wire gauge might help.

And as you probably already know the AT is so efficient pretty much any old amp will push it to adequate volume levels

just don't push the little amps too hard...

Both my AT and T18 made the same exact sound when hooked up to a little 25 watt plate sub amp (parts express #300-782). As soon as I switched amps the sound went away. The stronger higher wattage amp did a much better job.

I'm guessing the small transformer and power supply on my little plate amp equates to the same issue as a limited current supply with the car amp. (not enough oomph...) The replacement amp has a huge torroid and stiffening caps on the power supply end. no more issues even though it's a lot more power.

[Tom Smit]

I'm back again with another report.
Nobody was home for five hours so I brought the AT into the living room and hooked it up to our budget music system. The absolute most that this thing can output is 1.2 volts with the volume at "25". When I set the volume down to "10", the voltage would swing from .1 volts up to 1 volt. I realize that this is far from what alot of us would like but that's what the budget restricts us to at this time. Even still, the Autotuba did a real nice job of filling the bottom end. I'm very pleased!
Here are pics of the setup http://picasaweb.google.com/tammojsmit/ ... sicCentre#