Connecting monoblock tube amps to single subwoofer.


Hi all,

I have added a REL5TX sub to my system which is driven by VTL225 monoblocks.Currently the sub and amps are connected via the low level outputs on my preamp. I would prefer to use the high level connection to the REL by direct  connection to the the VTLs. I am concerned about creation of a ground loop that will cause hum on the system. I have been told that the ground loop can be avoided by running a ground wire directly between each amp. Is this a possible solution, and if so, where / how should the ground "jumper" be connected to each monoblock?

Many thanks in advance for any comments or suggestions.

rbanathy

Showing 6 responses by ieales

High level connections are a bad idea.

Any time there is a loop, there is a potential for problems. The main amplifiers could be oscillating above the audible range at a low level.

Ideally, you should be rolling the low end out of the mains. This gives an effective power increase to the mains and simplifies getting the phase correct between mains and subs.

I figured REL knows their products a lot better than I do. 

Possibly.

Connecting a sub to the speakers is generally a bad idea. It's an archaic Band-Aid.

Connecting to one speaker only ½ works for mono bass such as on LPs. Master tapes do not have mono bottom. 

With a separate power amplifier or pre-out/pwr-in on an integrated, much better results can be obtained by rolling the bottom octave[s] out of the mains with a simple passive first order filter and driving the sub from line level.

Bottom octave[s] are slightly above the anechoic -3dB frequency.

It's not about wavelength. It's about origin. I had single subs for HT and HiFi for about 15 years before I got duals. In both cases the subs were well integrated and time corrected with REW.

There is no comparison.                        

Dual subs are closer to control room large monitors than any single sub can ever hope to be.

the addition of a second sub is exponentially harder to set up, with the blend and the correct positioning, than just one sub.

 

Nope

What we are talking about is two REL T5x’s. They do have a phase adjustment switch and adjustable xover settings.

OOPs. The 0-180 switch is hidden in the logo. A 0-180 switch is the equivalent of moving the sub 14 feet @ 40Hz.

The XO control is frequency only. No filter type or order.

I've been setting up subs in systems for decades. Today with room correction and tools like REW, setting up two subs is actually easier than one.

My room is ±5dB from 20Hz. Show me a plot of your room and then we'll talk.

Assuming the op means he has a T/5x, setup is going to be very, very difficult:

  • No continuous phase control
  • No polarity inversion
  • No crossover order
  • No delay

If he has ported mains, fuhgeddaboudit.

See Subterranean Homesick Blues Guide to Subwoofers

As a composer once said of one of my systems:

"Those little speakers aren't putting out all that gorgeous bass?!?!?!?!?"

- No, there's a Force subwoofer at the end of the sofa. - 

"Every other subwoofer I've ever heard just boomed!"