Good question Mr. Chips. The answer is that I like the looks of my gear! And that it pretty much why most of the guys looking around the web ask about bridging. Obviously I could just buy a high power radio with a high power bridging amp for subwoofer.

And it is not a money thing.

I am an old school Alpine guy.[ Any others on the forum?] I love the way old school Alpine looks. If you look at their old amps, all of the input / output connections are at the rear and the face is very clean and good looking. This system will go in the back shelf of my Miata so I want a very clean no
seen running in the front and out the back look.

There is indeed a simple and non-destructive way to SUM the two amplifier outputs, and it does need a transformer rated for the power of the amplifier. The solution is a one-to-one ratio audio transformer with one winding connected across one of the amplifier channels, and the second winding in series with the remaining channel, feeding the speaker load. With the correct polarity the speaker will get the sum of the two power outputs, while with the wrong polarity it will get the difference, which will be much less. The transformer will be simple to wind, with about 50 turns of #18 wire and a stack of about 3/4 inch of 3/4 inch center laminations. There are lots of texts on winding transformers so those instructions are easy to find. And it is cheap since you can use the core of a failed audio output transformer and possibly even the wire and paper.

I really didn't want to get too deep in the woods about my set up because it is the circuit solution of the "Proposed Interface Circuit" that I was looking for. I appreciate all the interest. And I am also thinking that maybe I should give up on bridging the outputs. I am not in love with the monaural subwoofer. So why not just buy a new subwoofer that has two coils. They exist. But my intellectual curiosity WILL REMAIN. Surely there has to be such a circuit when it is so much in demand. Something simple. Passive. Off the shelf.

I think the power is 25 W per channel But will have to buy a manual to know for sure.

Finally, I agree about too loud. I run my speakers at normal power. Which in my mind means, what, maybe 7 watts? Audio engineers have a word for TOO MUCH BASS like the kids like to run. And any audio guys can correct me if I am wrong. They say the system is "boomy" [in a bad way]

Well. Unfortunately. I am 70 years old.

So. I am going to close this thread. But. I know their are a lot of guys on the web always asking "How can I bridge my non-bridging output" and I was hoping there might be a simple solution.

Thanks again for all the help And the interest.

Gary

 

Please see attached diagram.

Imagine an instance where the amplifier outputs are out of phase......... You don't need such a setup to blow the amps.....Direct connection does the same.

 

I agree that the output transformer shorts together the radio's amplifiers that could destroy them.

5V RMS into a 4 ohm speaker is (5 squared)/4= 6.25W which is not likely since 5V RMS is 14.14V peak-to-peak which is impossible. The car battery charges at about 14V then the radio output is about 12V p-p which is 4.2V RMS producing 4.4W into 4 ohms.

4.4W into 4 ohms has a current of 4.4W/4.2V= 1.05A which is the maximum RMS current the amplifiers were designed for. Bridging will almost double the current which will probably blow up the amplifiers the same as using two 2 ohm speakers.

Bridged car amplifiers produce about 14W just below clipping into 4 ohms per channel. But 14 Watts with low distortion is 25 Whats with a lot of clipping distortion. Then a car radio salesman says, "Hey, isn't the 25 Whats with a continuous sinewave but the peaks of a squarewave produce double the power?". Then they say the 14 Watts is 50 maximum Whats and a 4 channels amplifier is 200 maximum Whats.