Help Troubleshooting HSU VTF-2 MK2 Output Drop. Sub Dying? Seeking Advice!

[petrichor]

Hi all. I've got a 10" HSU VTF-2 MK2 that's about ~6 years old. Usually it performs like a champ: mated to a Harman Kardon AVR 645 I've had to keep the sub channel at -5db and the gain on the sub at around 50%; any higher and lows would be uncomfortably loud & overpowering for both music and HT. And I'm in a big (28x18x9) room. If I cranked it, window panes would vibrate & my desk would start to walk away.

Then, one day, I noticed a dramatic drop in low-end frequency response in the~30-150 range. I found myself maxing out the gain on the sub and setting the channel on the receiver to +10db just to get any low end out of the same tracks & movies for which I'd previously had to turn the sub down. I initially dismissed it as a product of my imagination, but after running some tests with the sub on & off I'm hard pressed to even tell the difference.

This is my first & only sub, so I'm not familiar with how/why they die, or what might be the problem.

The cone travels, so it's not utterly dead, and I'm stumped. Not sure if A. the sub is failing, B. the receiver is failing, or C. I'm nuts. Any thoughts, tips, & troubleshooting advice would be most greatly appreciated.


-P

 

[shadyJ]

Isn't there anything else you can hook the sub up to in order to see if its the sub or receiver? That's what I would do. If it's the sub, call Hsu customer support on Monday, because something probably went wrong on the amp.

 

[petrichor]

Isn't there anything else you can hook the sub up to in order to see if its the sub or receiver?

Unfortunately no, which has been the biggest obstacle in troubleshooting myself. I may steal a friend's receiver to that end...

 

[shadyJ]

Unfortunately no, which has been the biggest obstacle in troubleshooting myself. I may steal a friend's receiver to that end...

You don't necessarily need a receiver to see if the sub is working, just anything that can shoot out a line level signal. An ipod might work. An output jack on your computer. maybe your TV has some audio output jacks. Some desktop stereos have extra output jacks. A music keyboard with an output jack.

 

[petrichor]

You don't necessarily need a receiver to see if the sub is working, just anything that can shoot out a line level signal. An ipod might work. An output jack on your computer. maybe your TV has some audio output jacks. Some desktop stereos have extra output jacks. A music keyboard with an output jack.

Oh, hell -- an excellent idea. I hadn't thought of that. Will certainly give it a try. See, this is exactly why this site is invaluable.

I'd need a 3.5mm to RCA x1? (I've got myriad gadgets with 3.5mm output, but the "sub in" is a single RCA. It also has "Low level input" which looks like RCA x2, left and right; would that work? I do have a 3.5mm to RCA x2 adapter handy.)

 

[Grador]

Oh, hell -- an excellent idea. I hadn't thought of that. Will certainly give it a try. See, this is exactly why this site is invaluable.

I'd need a 3.5mm to RCA x1? (I've got myriad gadgets with 3.5mm output, but the "sub in" is a single RCA. It also has "Low level input" which looks like RCA x2, left and right; would that work? I do have a 3.5mm to RCA x2 adapter handy.)

That will work just fine, just make sure to start out with the sub gain turned all the way down. Use the "low level input" as this will use the subs built in crossover, you don't want to feed the sub full range signal.

 

[shadyJ]

The VTF2 mk2 probably also has speaker level inputs, you could just use your speaker wire to hook it up too. Like Grador said, you will want to turn the volume all the way down at first and gradually raise it up. Use a test tone or some music that has a sustained bass line to test it.

 

[petrichor]

The VTF2 mk2 probably also has speaker level inputs, you could just use your speaker wire to hook it up too.

It does. Will that bypass the sub's amp, getting power from the receiver, or would the sub just amplify that signal? And that wouldn't send a "full range" signal to it?

 

[Grador]

The speaker level inputs would still use the amplifier built into the sub. The sub will use it's internal crossover when using them.

 

[shadyJ]

It does. Will that bypass the sub's amp, getting power from the receiver, or would the sub just amplify that signal? And that wouldn't send a "full range" signal to it?

The sub will just amplify that signal. It would be full range, but you don't have to worry about that, you are just testing the sub to make sure it works. I wouldn't want to have the sub try to play full range in a finished setup, but for testing purposes, it won't matter.

 

[petrichor]

The sub will just amplify that signal. It would be full range, but you don't have to worry about that, you are just testing the sub to make sure it works. I wouldn't want to have the sub try to play full range in a finished setup, but for testing purposes, it won't matter.

Makes sense. I ended up running it from my phone & then ipod using just the "low level input" RCA jacks. Both produced the same results (or lack thereof): very muddled, barely audible output. When deactivating the internal crossover, I could faintly hear higher frequencies, but again no low-end to speak of. It's crippled. This would be the amp failing? (As opposed to the motor, etc? Not very familiar with inner workings of subs.)

 

[shadyJ]

I'm guessing its the amp. You need to call Hsu at this point, they will walk you through some steps to diagnose the problem. You may end up needing to send the amp in to get fixed.

 

[j_garcia]

I'd definitely call HSU on this one.

 

[petrichor]

I'd definitely call HSU on this one.

Will do just that. Despite the bad news, I much appreciate all the troubleshooting tips. Thanks fellas!

 

[Grador]

Good luck! Hope you get it all worked out.