I have not used the subwoofer out on the receiver before.

Maybe someone in here can help with that. Is it true that
the sub only kicks in at certain frequenmcies.

Also, my setup instructions from the receiver shows
an RCA connection out of the Yam and into some sort of
Yam sub. My question is: even if the connection to the
outboard amp is necessary for whatever add-ons Yamaha
sells, should I not hear something out of the speaks?

No info in the documentation. I'm going to have a friend
bring his meter over here and see if he can get a reading.
But nothing came through given I just did an alligator
clip connection on thin wire. Could be the cheap plug
I cut off was no good too. Lots of variables at that point.

I did the battery test on the speaks and they are both okay.

So maybe somebody can walk me through the troubleshooting.

The plug is located just below all the input jacks and
a tape out pair. The directions show a connection of
RCA at both ends to connect the add-on Yamaha sub.

Ok, I have the little Radio Shack SA155 amp out on the
bench doing nothing. The SA155 uses RCA jacks for speakers
as well, plus it has a 3 way switch for input selection
including phono preamp.

Are we saying that a small plate amp should be a part of the
project? PE has those for $30 as does MCM.

If I had a tuba 18 would these same issues apply? From the
audioXpress writeup Fitz did on the build, there's not much mentioned
about hookup that I recall-- and no plate amp showing anywhere.

I just made the hookup to the little RS amp.

I would say there is a problem from connecting the Yam
to the tuner in on the amp. I had to jack the amp up to
full volume to get any signal at the speakers. This cannot
be right.

Maybe I'd need the phono preamp connection to get
any juice. But I'm not going to procede until I know more.

Your suggestion sounds right though and the RS should
be the ideal unit without buying a new piece of gear.

Maybe a y-connect from the subwwoofer out on the Yam to
the left right connects on the RS? I haven't tried the
phono in to check this. What kind of damage can I do?
I've already spent some dough on a repair guy to
fix the RS (amp chip replacement) once for about the cost
of what I paid for it. :-/

This is measured response of the autotuba. Notice peaks at 40hz, 80hz and 160hz which is the musical note D. There is more than 15dB (50x power) varience between D and A in the same octave.

I used a high q and fs driver (ApexJr Super8), while the horn is designed with a low q and fs driver (MCM 55-2421) in mind.

So please don´t use this as an example of how the AutoTuba response is.

Kim

Local audio guru sez a plate amp is needed and that it will
give a useable volume level, unlike patching through the
Radio Shack. But I'm wondering what the difference is (?)

Looking up the cheapie plate amp at PE....

Well it gives some detail but not what I was looking for.

About the most efficient entry level product I can gather
is one of these and the MCM 6 in subwoofer driver w/16 mm
Xmax as shown with the Tuba 18.

Interestingly, the tubas are getting a bit of discussion
over at the Full Range Driver Forum.

• PE compact subwoofer