tri mode amplifier

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ianarian

Copper - Posts: 516

Joined: April 24, 2009

Location: California, United States

Posted: April 21, 2010 at 10:44 PM / IP Logged

Tri-mode does anyone use it? Has anyone tried it? I recently found a use, but I am curious if anyone else has.

This is what I do for FUN!

i am an idiot

Platinum - Posts: 13,667

This member consistently provides reliable information

Joined: September 21, 2006

Location: Louisiana, United States

Posted: April 22, 2010 at 6:15 AM / IP Logged

It has been many many years since i had a single amp setup in my car, but yes I have used it, it works just fine. There is a problem with the impedances they have listed in that diagram. The only safe way to do it is to bridge an 8Ohm driver, and connect a single 4Ohm driver to each of the 2 channels. This will yield a 4Ohm mono load on your amplifier.

It really has 2 different applications that are useful, 1 is a single amp full range system, bridge an 8Ohm woofer, with an inductor in series. Connect your Door or dash speakers to the appropriate channel with a capacitor in series with each of them. The inductor and capacitor are Passive Crossover devices. They block unwanted frequencies from each set of speakers.

Second use is if you have a Subwoofer enclosure with 3 seperate chambers, you can bridge an 8Ohm driver, and connect a 4Ohm driver to each channel. The 8Ohm woofer which is generally less efficient than the 4Ohm drivers will be receiving more power than the 4Ohm drivers. Thus making all 3 drivers work very close to the same level.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: April 22, 2010 at 9:03 AM / IP Logged

Thanks Idiot for a real reply...

I was tempted to mention how close it was to pseudo-quad from stereo - ie, fronts are normal left & right; rears are the same impedance but bridged between the front actives (ie, L+ & R+).

The rears could be in or out of phase (ie, interconnect between rear speakers are - to + else - to -), but the rears are effectively the difference between the front R & L speakers.

Hence bass was often lacking in the "pseudo" rears (lower frequencies being more in-phase between L&R than higher frequencies). (And should arguably have thus been the front speakers now that I know more, but it worked well, and I still like the "stage-like" front thumpers as I have now imitate my larger door speakers and 2" headrest speakers with my MASSIVE 4x16W Alpine (RMS of course!!).

But as I said, it was only a temptation.....

(I was going to buy an 1800W tri-mode until I found out it was only 900W RMS. Now I'm starting to search for hi-power 8-Ohm speakers... When I was a kid, Fender had a bass (guitar) speaker with a life guarantee.... )

ianarian

Copper - Posts: 516

Joined: April 24, 2009

Location: California, United States

Posted: April 22, 2010 at 6:51 PM / IP Logged

Thank you gentlemen,

I was on the way home from work today, "slappin", and wouldnt ya know it... the smell. I had each side bridged @ 4ohms and she didnt like it very much.

This is what I do for FUN!

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: April 22, 2010 at 7:17 PM / IP Logged

Idiot! That's makes Idiot look right doesn't it?

[Didn't he question the 2x4Rs & suggest a bridged 8R? That's how my pseudo quad (3 channel?) was done - (say) 4R for L & R, and 2x4R = 8R between L+ & R+; not center-to-amp/GND connected as in the diagram.]

GOOD! I can have another go at the title....

(Idiot has provided too many really excellent replies lately IMO!)

At least now we know what the third mode is, else that it has a undocumented feature - or 4th mode.

i am an idiot

Platinum - Posts: 13,667

Joined: September 21, 2006

Location: Louisiana, United States

Posted: April 22, 2010 at 7:54 PM / IP Logged

The diagram is accurate. Any bridgeable amplifier that does not have a physical switch to allow bridging uses Positive from one channel and negative from the other channel to bridge. Positive to positive will play only one channel. On a bridgeable amp the 2 non bridge wires are connected together inside the amp. If amp bridges Left positive and Right negative, the left negative and the right positive wires are both common with each other.

ianarian

Copper - Posts: 516

Joined: April 24, 2009

Location: California, United States

Posted: April 22, 2010 at 9:13 PM / IP Logged

I am doing my best to keep up here... If I have a positive and negative in common with each other...what does that do to my stereo separation if I am using std. 4ch operation? In tri-mode, the front becomes the left side and the rear, the right side. So in that sense, it would not matter if they shared a common.

This is what I do for FUN!

ianarian

Copper - Posts: 516

Joined: April 24, 2009

Location: California, United States

Posted: April 22, 2010 at 9:21 PM / IP Logged

So, the way I had it wired was safe, and the smell I got was not due to impedance being too low?

This is what I do for FUN!

i am an idiot

Platinum - Posts: 13,667

Joined: September 21, 2006

Location: Louisiana, United States

Posted: April 22, 2010 at 9:36 PM / IP Logged

I have no idea what you were smelling. That amp should handle a 4 ohm mono load. With the amp turned off, what is the resistance across the 2 bridge wires of the amp. Speakers connected to amp, but amp not powered on.

ianarian

Copper - Posts: 516

Joined: April 24, 2009

Location: California, United States

Posted: April 23, 2010 at 7:30 PM / IP Logged

The smell of electronics overheating...

I have 6 4ohm speakers that I use to have 2 amps for.(1 spkr/ch) I had to remove a amp so I tried it tri. Either way I can run 4 spkrs at 2ohm stereo without issues.. Are you sure you werent right the first time? As long as I had 4ohms across that pair... I'm safe on impedance..BECAUSE...the +&- are in common? You make we want to switch it back to take a reading...

This is what I do for FUN!

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