Axiom Home Page Forums General Discussion Stereo Big Project, outstanding outcome

With the help and blessing of Ian and James Tanner, I went down the road of converting my Bryston Model T's from the internal passive crossover to the external PX1 Signature series crossovers.

Ian said that I run the T's so hard and loud and so much power, I'd be well served with going over to the PX1's as they handle a significant amount of power over the internal units. It was decided that it was going to be too costly and potentially dangerous to the health of the T's to ship them back to Canada and then endure the return trip to me in the states. I offered to use my shop here to do the work as I have a lot of cabinet making experience and also electronic wiring expertise.

James found a pair of new PX1's he had on hand which he shipped to me and Ian made up the new triple input plates which were sent along with a good supply of the high end Axiom 12 gauge fine stranded copper speaker wire. I spent three days doing the work along with making up new super duty wiring harnesses with very heavy duty mil spec navy surplus spades, all soldered connections of course.

It was a rather involved project as I had to do some cabinet reworking to fit the new input plates, custom make urethane gaskets and do a lot of internal rewiring. However the final product is beyond anything I anticipated. Not only do the PX1's handle huge power input (these things are huge), but the output level of the drivers is at least two to three times that of the stock internal crossover Model T design. The noise floor is dramatically reduced, I mean it's creepy.... no crackle/pop sound from vinyl records between songs, it's disappeared.... and the detail in the music is amazing. I have never heard such beautiful bass/mid with powerful definition and the upper end is nothing but open air. The instruments are 'in the room'.

A huge thank you to Ian. I am very appreciative of his insight and guidance. This company is truly a step above.

Slim

The dedicated external cross over idea has me excited to.
Pretty good chance I'll go this route to but with smaller speakers (small room).

Craig, it looks like you're missing out big time!

The lack of dust and static sounds from vinyl is very puzzling.

Puzzling to me too...

TAM

Slim, are you still putting in 2000W RMS into each T? What is the dynamic capability of those amps? I hope the outboard cross-overs have 12 ga coils or they'll ignite.

The crossover feeds the amp zero load on the amp.

Richard, each of Slim's Ts are sinking at least 20A RMS. That current is displaced not only in the speaker but also the cross-over. The coils can act like heaters if not appropriately designed.

I told Ian I was working on a liquid cooled heat pipe mod for the PX1's similar to the M1 monoblocks which yes, are at 2000 watts per channel into 4 ohms with 240 volt/15 amp dedicated inputs.

However, after running the new upgrade for three days now at levels that have not melted the crossover coils, but have sagged the glass on my living room windows and still have not caused the PX1's to get warm to the touch, I am abandoning the heat pipe project.

The snap crackle pops of the records are not dust. The records are clean; it's just normal typical vinyl lead in to cuts. But it's way down now.... I mean way down. No idea what is going on.

I was speaking with James Tanner on this today, he's perplexed too. He's wondering if this might be due to transients in the signal. OK you engineers out there. chime in.

In fact the entire noise floor is to the point where its almost gone and signal is way up. S/N ratio is so much nicer

The cooling system is still a good idea because it will prolong the cross-over's life. An even better idea though is to chill the voice coil.

OK, well I have had the Gap Band on the turntable with a 12 inch single of "you dropped a bomb on me" playing multiple times over two hours at blistering levels.... the crossovers are cold to the touch. The M1's are at best luke warm at 87 degrees reading from the infrared heat reader and I need to have Bryston lend me a pair of 28B3's to test vs. the M1's.... The 28B3's have a lot more in the power supply back up for dynamic range. Lets see if we can get the PX1's at least above room temperature!

The only possible explanation for the removal of clicks and pops is a built-in notch filter. This pre-supposes the clicks and pops are in a very narrow and well-defined band or bands.

Can you stick a thermocouple in the woofer's air gap? LOL!

he is goin active so the crossovers are before the amp at least thats what it seemed. forgive my poor comprehension but i see no point in passive external.

I see. No, they won't be fully active.

Agree that if he is using active crossovers and separate amps per frequency band there shouldn't be a need for passive crossovers as well but I didn't see any mention of active crossovers.

That said, one thing that occurred to me from reading this thread is that the beauty of an external crossover (apart from things like power handling) is the ability to switch to active crossovers and tri-amping without having to change the speaker itself.

I am not fully active here. Still using one M1 mono block per Model T, entering into the input stage of the PX1 with all the jumpers connected. The outputs are individual cables feeding each individual section of the Model T's. I cut all the internal wiring and made up new wiring from tweeter section, mids and woofers all dedicated individual runs independent from one another. Each run goes directly to a new input plate Ian supplied which has three separate speaker terminals labeled "high", "mid", "lower". One only has to make sure that they run the interconnects from the output of the PX1 from the appropriate section to the correct speaker bank. It's rather simple. But the external crossover is between the amplifier and the Model T. The internal crossover is no longer functional, it's been disconnected.

If I ever wish to go fully active, I just need to get 2 more amps per Model T and purchase the Bryston fully active crossover which would go between the preamp and the amps.

New Addition to the stable.....
I got in a wood veneer black ash Bryston Model T sub woofer. I am now up to three subs, and counting.

The Model T mains are of course up front, the EP800V4Bourbon/Gin switch is to the left at 90 degrees, the EP500V4 is to the rear at 180 degrees and the new, gorgeous Model T sub (105 pounds) is at the right at 270 degrees.

Pretty interesting: the bass is much smoother, more musical, well rounded and just soothing. No big nodes in the room and it's just like being in a small club with a really good bass player mixing in with the music. But the house shakes; I love it.
OK, now Ian said I hit sub nirvana at 3 but 4 is where the amplitude really kicks up a notch along with the smoothed response I am hearing. It's a good thing I am now single, I can do what I want.....

So...now you need a sub up front, right?