Bringing an old Subwoofer back to life.

[fmw]

For the past dozen years this old B&W AS6 subwoofer has been a reliable member of my collection of AV components and has served my home theater well. It is a 12" ported unit that weighs about 75 lbs. It certainly isn't a high end unit but has enough stuff to shake the room with LFE despite its modestly sized 100 watt plate amplifier. Replacing it would cost $500 or $600 so I decided to open up the the back to see what is going on.

I removed the plate amp, plugged it in and took some voltage measurements and discovered that the power supply is as dead as a door nail. No voltage at all was found between the supply and the amplifier board. I checked the internet to see if a replacement plate amp is available. The only thing I found was a factory replacement unit for $720, not a very good bargain. The old plate amp is 9 3/4" square and is fairly deep as you can see from image of the back of the unit.

I went to Parts Express and found this for $119.95. It is a 250 watt amp with a plate that is, by some stroke of luck, 9 13/16" square so at least it will cover the old hole. Will the amp fit into the cavity on the back of the sub? I don't know but I ordered it and will see what it is going to take to install it in the AS6. So the mystery continues until next week when the amp should arrive. My fingers are crossed. I'll post the rest of the story after that happens.

 

[Adam]

Cool - good luck with it! The perimeter design and bolts around the woofer sure look familiar. I had an ASW1000 for years. Nice sub, but it didn't dig as deep as I wanted, so I splurged on my PC13. I never took the amp out (that I remember), but I did take the woofer out of the first one that I got (it was defective and rattled) - that was one heavy magnet! I forgot about those heat sink fins. The SVS's that I have don't have those (Class D, and all).

 

[fmw]

No need to remove the woofer. I'm sure it works. I have no problem getting it to move with a battery. If the new amp doesn't fit I'll have to remove that composition cavity and do some sawing. I have a positive feeling that the new amp will fit right in. We shall see. The Amp is AB biased and so is the new replacement.

 

[AcuDefTechGuy]

You guys already know what I'm going to say about that.

......... It's why I only buy unpowered subs - so that I can use WHATEVER amp I want.

Less expensive, more durable, more versatile.

 

[AcuDefTechGuy]

This also reminds me of how little power is needed.

A 100 watt amp (probably into 4 ohms like most sub amps), which means about 60 watts into 8 ohms.


My first sub was a 10" NHT unpowered sub which was powered by an ext 80 Watts NHT amp. And that sub shook the walls like a rag doll.


These days we see subs with 2400 watts and the numbers keep getting higher and higher.

 

[fmw]

Well, it's an unpowered sub at the moment. If it weren't for the short wait for the new amp, I'd hook up the Yamaha pro audio amp and let it fly. I'm too lazy to solder and unsolder things. One of the advantages of using the plate amp is that it has auto on. That way I can leave the sub alone 24/7 and that appeals to me.

Yes, the entire audio industry has had a love affair with high amplifier power for a long time. Back in the 50's people were content with 20 watt amps. In the 60's I had a Harmon Kardon 11 and 12 combination that was solid as a rock. The amp was 60 watts, weighed nearly 40 lbs and would drive anything and probably would drive anything today as well. This B&W sub has never had a problem shaking the walls of my family room at 1/3 power. I have a 30 watt per channel integrated in my exercise room. It is way more than enough. Yet people feel the need for power they never use.

 

[Irvrobinson]

This also reminds me of how little power is needed.

A 100 watt amp (probably into 4 ohms like most sub amps), which means about 60 watts into 8 ohms.


My first sub was a 10" NHT unpowered sub which was powered by an ext 80 Watts NHT amp. And that sub shook the walls like a rag doll.


These days we see subs with 2400 watts and the numbers keep getting higher and higher.

And this coming from a man who uses two Funk 18.0 subs with his Salon2s (-3db @ 23Hz) running full-range. Oh yeah, and the same guy who got a little bent out of shape because Funk said some confusing things about the 18.0's maximum output versus the 18.3's, which, incidentally, is on the high side of 120db. Okay...

FMV's B&W is a ported design with a -3db point of 30Hz. The 2000+ watt products are sealed designs in relatively small enclosures with heroic drivers and usable output at 15Hz. If you want that 120db of advertised output, 500 watts won't do it. If Funk put a 500 watt amp in the powered 18.0 and Ricci tested it and found its output limited to, say, 105db, wouldn't you feel upset (even though you buy the passive versions)?

Don't mind me, I'm just rattling your cage because I'm in a weird mood this morning.

 

[Adam]

Yet people feel the need for power they never use.

Which is why, some day, I'm going to make a mint off of my LightningStrike(R) amps. 1.21GW of pure audio excitement - assuming that someone has the storage space for the external capacitor bank...

 

[AcuDefTechGuy]

And this coming from a man who uses two Funk 18.0 subs with his Salon2s (-3db @ 23Hz) running full-range. Oh yeah, and the same guy who got a little bent out of shape because Funk said some confusing things about the 18.0's maximum output versus the 18.3's, which, incidentally, is on the high side of 120db. Okay...

FMV's B&W is a ported design with a -3db point of 30Hz. The 2000+ watt products are sealed designs in relatively small enclosures with heroic drivers and usable output at 15Hz. If you want that 120db of advertised output, 500 watts won't do it. If Funk put a 500 watt amp in the powered 18.0 and Ricci tested it and found its output limited to, say, 105db, wouldn't you feel upset (even though you buy the passive versions)?

Don't mind me, I'm just rattling your cage because I'm in a weird mood this morning.

Well, the AT3000 (probably 600+ watts RMS into 4 ohms @ 1% THD) is powering two Funk 18.0N.

The AT2000 (500 watts RMS into 4 ohms 1% THD) will be powering five RBH SX-1010N.

RBH recommends 500W RMS, so that's good.

Nathan really wants me to use 2400 watts RMS to power the Funk, but I am adamant about using my dear ATI, even if it is underpowered.

 

[fmw]

I'm trying to imagine the ear pain I would suffer with 120db of sound in my family room. No thanks! Looks like AcuDef is all set in case he decides to move his system out to the patio or deck!

 

[fmw]

It wasn't bad at all. The amp arrived today. All I had to do was remove the plastic cavity, chisel out a little of the rabbet, solder up the wires and screw it in. Works like a charm. This is a pretty simple repair for any handy person to do. No question this amp has more gain. I have the gain knob at 15%.