HSU STF-3 issue: update, help choosing options

[The Jay]

Hi;

I previously posted about this STF-3.


But to sum it up, I saw it on Kijiji. I went to the seller's home and he turned on some music on relatively low volume and I heard the STF-3 working just fine. He turned up the music to around middle volume and the sub's power and volume were quite evident. I felt underneath and the driver was moving normally. But I got it home, hooked it up and it barely made a sound. The volume was barely audible, no matter what I'd do. Tried everything, including another reciever.

Update:

I took it to a repair shop who gave up and said they couldn't even get a schematic on it and couldn't say what is wrong with the amp, but that the amp likely needs replacing.

HSU says that I can upgrade to the VTF-3 MK4 amplifier. That would run $235 plus $25 S/H if in the lower 48 states. But I'm in Toronto....

So that would run $323 CAD for the unit. I have emailed HSU asking for a quote on shipping to Canada; they haven't responded yet.

I paid $220 for the unit.

My dilemma is obvious. Repair or cut my losses now? With shipping that would amount to well over 500 invested in this sub....To compare, a new SVS PB-2000 runs about $1265 up here after taxes.

Thoughts?

 

[shadyJ]

The STF-3 is a simple sub compared to the VTF subs, so you could use almost any amplifier of sufficient power. I would be looking at 250 watt to 500 watt amps, preferably with some kind of DSP or high-pass filter onboard to protect the driver below tuning (18 Hz). You do not have to buy Hsu's amp. You can get an outboard amp and install binding posts in the cabinet, and just power the driver from another amplifier. The STF-3 is still a relatively powerful subwoofer, and it probably wouldn't be that far behind in performance from a PB-2000. The STF-3 driver is pretty good.

 

[rojo]

@The Jay Did the repair shop test the sub assembled, or did they just look at it and say, "Never seen this before. Buy a new amp"? I'm wondering whether it's possible that your LFE channel is turned all the way down, or maybe you've got a DSP mode enabled that disables LFE -- "stereo" or similar? If you've got a 3.5mm -> RCA Y cable, you could try plugging your phone directly into the subwoofer and see whether it makes noise while playing a YouTube video or similar, thus bypassing the AVR to rule out a signal problem.

 

[everettT]

Do you have all your speakers set to small bu chance?

 

[The Jay]

Hi the shop charges 40$ for diagnosis, then if you go with the repair, that counts towards the labour. First they asked for more time with it, because they were trying to find a schematic, then said they couldn't get enough info to repair it, and that it "must be the amp because it's the only board in there". When I went to pick it up they refunded me 20$ because they weren't able to diagnose.

All speakers are set to small, I've been through every function that could do this with both of my recievers.

Thanks for the replies. What do you recommend I do with this? Would anyone know of a seperate or plate amp that would be a good fit?

 

[rojo]

@The Jay Any clue what the dimensions of the cutout are? If not, can you at least measure the exterior of the plate?

 

[everettT]

http://www.musiciansfriend.com/pro-audio/crown-xls1002-2-channel-350w-power-amplifier-with-onboard-dsp?rNtt=crown xls&index=1

 

[lovinthehd]

http://www.musiciansfriend.com/pro-audio/crown-xls1002-2-channel-350w-power-amplifier-with-onboard-dsp?rNtt=crown xls&index=1

That amp doesn't have the dsp to place the needed protective HPF (the dsp it has is for crossover implementation). Behringer iNuke DSP series amps do, though.

 

[The Jay]

I appreciate the advice and help....this is new territory for me. The sub would be connected to LFE from either my Denon E400 or the Marantz SR7010..I was thinking of a plate amp off of parts express. Is there a reason to go external over a plate amp?

Was looking at these:

Yung SD500-6 500W Class D Subwoofer Plate Amplifier Module with 6 dB at 25 Hz
$238 - Do I need a 6db boost?

Yung SD500 500W Class D Subwoofer Plate Amplifier Module No Boost - same cost $238

The original amp is 300W RMS. So if I went with that level of power there's these:

Yung SD300-6 300W Class D Subwoofer Plate Amplifier Module with 6 dB at 30 Hz - $139

Yung SD300 300W Class D Subwoofer Plate Amplifier Module No Boost - Again, same cost $139

Bash 300S Digital Subwoofer Plate Amplifier 300W RMS - $154



What do you think of those choices?
Thanks for all the help.

 

[shadyJ]

The problem with a plate amp is if it does not fit the existing cut-out, you will have to modify the sub cabinet to make it fit. Easier and less expensive to use an outboard amp. If these plate amps do fit the cut out, then yes, go for them, otherwise, just get an outboard amp.

 

[Verdinut]

I agree with shady j.
If you decide to go for an outboard amp, I would suggest a used pro amp such as the QSC RMX850 which you can get on eBay for a very decent price. There are always some for sale. At present, there is a new one selling for $274 CDN.
That kind of amplifier with the two channels bridged, would give you a good 600 watts at 4 ohms and would outlast any plate amp.

In Canada, the AV Shop in Markham and Studio Economik in Montreal have decent prices on QSC products.

 

[lovinthehd]

I don't see dsp for a suitable protective high pass filter on the RMX series amps....

I agree with shady j.
If you decide to go for an outboard amp, I would suggest a used pro amp such as the QSC RMX850 which you can get on eBay for a very decent price. There are always some for sale. At present, there is a new one selling for $274 CDN.
That kind of amplifier with the two channels bridged, would give you a good 600 watts at 4 ohms and would outlast any plate amp.

In Canada, the AV Shop in Markham and Studio Economik in Montreal have decent prices on QSC products.

 

[Verdinut]

I don't see dsp for a suitable protective high pass filter on the RMX series amps....

Why should someone need a high pass filter on an amp which is to drive a subwoofer?

 

[lovinthehd]

Why should someone need a high pass filter on an amp which is to drive a subwoofer?

See shadyj's post #2. I'm assuming he knows enough about this particular sub/box to justify it, but many ported subs do need such a protective high pass filter to protect the driver from over excursion below tuning.

 

[TLS Guy]

I appreciate the advice and help....this is new territory for me. The sub would be connected to LFE from either my Denon E400 or the Marantz SR7010..I was thinking of a plate amp off of parts express. Is there a reason to go external over a plate amp?

Was looking at these:

Yung SD500-6 500W Class D Subwoofer Plate Amplifier Module with 6 dB at 25 Hz
$238 - Do I need a 6db boost?

Yung SD500 500W Class D Subwoofer Plate Amplifier Module No Boost - same cost $238

The original amp is 300W RMS. So if I went with that level of power there's these:

Yung SD300-6 300W Class D Subwoofer Plate Amplifier Module with 6 dB at 30 Hz - $139

Yung SD300 300W Class D Subwoofer Plate Amplifier Module No Boost - Again, same cost $139

Bash 300S Digital Subwoofer Plate Amplifier 300W RMS - $154





What do you think of those choices?
Thanks for all the help.

Yes, Plate amps are about the most unreliable piece of gear in your system, as you have found out.

That is really bad form of HSU not to send a schematic to a repair shop. This is common these days and it's a disgrace. Strike that a big bad mark against HSU.

An external amp is much more likely to give long service. Unless you are going to play it very loud, then I would not worry about the high pass filter.

The problem is that all this talk of big amps to drive subs is bogus. There is very little power in sub range and the amount of power a sub should take is small except for the odd effect.

The power really is from 80 Hz to 500 Hz and that is where power resources need to be concentrated.

Most subs are turned up way to high, most of the time it should appear they are not working.

This sub abuse has made properly balanced and integrated bass a real exception and that's a pity as it really spoils a good performance.

 

[shadyJ]

Yes, Plate amps are about the most unreliable piece of gear in your system, as you have found out.

That is really bad form of HSU not to send a schematic to a repair shop. This is common these days and it's a disgrace. Strike that a big bad mark against HSU.

I would guess Hsu are probably are not permitted to send any schematics out without authorization from whatever company owns BASH designs. They didn't design that amp, they just use it for their subs.

 

[Verdinut]

See shadyj's post #2. I'm assuming he knows enough about this particular sub/box to justify it, but many ported subs do need such a protective high pass filter to protect the driver from over excursion below tuning.

I agree with you there. The situation all depends on the tuned frequency of the box and the source frequencies being fed to the sub. Of course, the volume being played is an important factor as well.

 

[TLS Guy]

I would guess Hsu are probably are not permitted to send any schematics out without authorization from whatever company owns BASH designs. They didn't design that amp, they just use it for their subs.

I know that is likely the reason. The HSU should not use a BASH amp. They should only buy serviceable amps. This is where we need a change on law. This seldom happens with good vintage amps.

May be the OP should buy an old but good vintage amp that can be serviced.

I do not own power amps I don't have a service manual for and never would. Keep the old gear running.

 

[shadyJ]

I know that is likely the reason. The HSU should not use a BASH amp. They should only buy serviceable amps. This is where we need a change on law. This seldom happens with good vintage amps.

May be the OP should buy an old but good vintage amp that can be serviced.

I do not own power amps I don't have a service manual for and never would. Keep the old gear running.

There probably isn't a plate amp they could use where they would be permitted to release the schematic. They would have to design it themselves. And the manufacture of their own design would multiply the cost of their products.

Having serviceable amps is nice, but those kind of amps are relatively expensive. What you are proposing is ideal, but not practical for most middle class people.

 

[TLS Guy]

There probably isn't a plate amp they could use where they would be permitted to release the schematic. They would have to design it themselves. And the manufacture of their own design would multiply the cost of their products.

Having serviceable amps is nice, but those kind of amps are relatively expensive. What you are proposing is ideal, but not practical for most middle class people.

What is here about issue a schematic and service manual that makes it expensive? It does not! Also it gives a living to repair technicians. Middle class people bought the electronics of old and service manuals were always available. For just about any item of 70s and 80s gear you can find and download a service manual in minutes. As we progress to this MBA/marketer driven era, not a fat chance.

There is no excuse for the current state of affairs and there needs to be and should be a change in law.

This disposable electronics trend is polluting the planet with dangerous toxins. Making people pay the TRUE cost of disposal up front with purchase would change things in a hurry. Then longevity would be the key marketing issue.