Easily replaceable plate amp for Acoustic Research 15" S115PS sub??

[cam94z28]

I have had this sub for years sitting in my dads living room. He hates bass, so it's been sitting unplugged. Today I hooked it up, and noticed that it was cutting out (going into standby, then turning back on) when the receiver sub level, or sub-amp gain was above a certain point. I would assume it's a problem in the amp.

Are there any plate amps sold here that would be a relatively direct replacement? I can get actual dimensions if needed. There don't appear to be many specs for this model online. Also since I'll have it apart, any good 15" that would be a bit more musical? The existing sub appears to be relatively cheap.... ribbed, laminated paper cone, vented voice coil, decent size magnet. It actually has a rubber surround, though.

[Brent_S]

Your description suggests the amp is probably working properly. The "sleep" circuit needs to see a certain amount of voltage to wake up. If the signal level drops below that threshold for some period of time (typically 10-15 minutes), the amp goes back to sleep. One typical fix is to increase the sub out level in the receiver and reduce the gain on the plate amp. This will maintain the same SPL output from the sub for a given master volume setting, but send more voltage from the receiver to the sub.

To start identifying potential replacement drivers, you need to know the net internal volume of your enclosure. If it's ported, you also need to know the current tuning frequency...can be backed into via port diameter/length/net cabinet volume. It might be possible to retune, if needed, depending on the cabinets physical construction, or simply seal up the port.

-Brent

[cam94z28]

Your description suggests the amp is probably working properly. The "sleep" circuit needs to see a certain amount of voltage to wake up. If the signal level drops below that threshold for some period of time (typically 10-15 minutes), the amp goes back to sleep. One typical fix is to increase the sub out level in the receiver and reduce the gain on the plate amp. This will maintain the same SPL output from the sub for a given master volume setting, but send more voltage from the receiver to the sub.

To start identifying potential replacement drivers, you need to know the net internal volume of your enclosure. If it's ported, you also need to know the current tuning frequency...can be backed into via port diameter/length/net cabinet volume. It might be possible to retune, if needed, depending on the cabinets physical construction, or simply seal up the port.

-Brent

It actually appears to be the opposite. It's like the amp goes into some type of shutdown mode when the gain or sub level reaches a certain point. For example, if I leave the gain at 100% on the sub amp with music playing, and turn up the sub level on the receiver. When it reaches a certain point, the amp cuts out, then cycles back on anywhere from 2-10 seconds later. If I don't lower the sub level, it will shut down again nearly immediately. I can achieve the same thing by maxing the sub level on the receiver, and slowly turning up the gain on the sub amp.

Anyway, the sub is kind of boomy as it is. A replacement amp will cost a minimum of $100 (original amp is 250 watts). I was doing some reading, and it appears a modern day subwoofer can be had for about the same price that will probably be more efficient, more musical, and possibly even be louder with a smaller woofer. I think it might be time to retire the S115, for something like a polk psw10.

Thank you for your reply though.

[generic]

It actually appears to be the opposite. It's like the amp goes into some type of shutdown mode when the gain or sub level reaches a certain point. For example, if I leave the gain at 100% on the sub amp with music playing, and turn up the sub level on the receiver. When it reaches a certain point, the amp cuts out, then cycles back on anywhere from 2-10 seconds later. If I don't lower the sub level, it will shut down again nearly immediately. I can achieve the same thing by maxing the sub level on the receiver, and slowly turning up the gain on the sub amp.

Anyway, the sub is kind of boomy as it is. A replacement amp will cost a minimum of $100 (original amp is 250 watts). I was doing some reading, and it appears a modern day subwoofer can be had for about the same price that will probably be more efficient, more musical, and possibly even be louder with a smaller woofer. I think it might be time to retire the S115, for something like a polk psw10.

Thank you for your reply though.

Don't turn the sub plate amp up to 100%. Try no more then 50%. How are you turning the sub up from the receiver?

Are you using a RCA low level cable out to the plate amp?

It kinda sounds like your over driving it. The shutoff could be some sort of overload protection. It could be boomy because it's not a good sub, or because it's being over driven to distortion.

[cam94z28]

Don't turn the sub plate amp up to 100%. Try no more then 50%. How are you turning the sub up from the receiver?

Are you using a RCA low level cable out to the plate amp?

It kinda sounds like your over driving it. The shutoff could be some sort of overload protection. It could be boomy because it's not a good sub, or because it's being over driven to distortion.

I am setting the sub level (SW level + or - 10) on the receiver. I am using a subwoofer cable (from the receiver pre-out) into the left channel input on the plate amp. The plate amp does not have a LFE input.

I guess I could have been overdriving it, The output wasn't very loud, and the subwoofer itself wasn't even close to bottoming out.

Other weird things are happening though. For example. I can plug the sub cable into the left or right input, as well as the left or right OUTPUT, and it receives a signal, and sounds exactly the same. Additionally, if I flip the phase switch, the output goes down to nothing. It's not just out of phase, it goes from having the plate amp gain at 30-40% and the sub level on the receiver at +2 or +3, to having to max the sub gain, and nearly max the receiver sub level in order to get any output. Also, it seems the higher I set the crossover on the receiver, the lower the output gets. For example, 40hz xover is much louder than 80hz. I have a Sony SA-W2500 in my bedroom. With the same receiver it does the complete opposite. It's a very boomy sub too, but it properly reacts to the crossover point.

I think, overall, the sub is just too boomy, though. I have tried it both in the living room (where it was), and in my very small bedroom.

[generic]

Do you have a db meter? One person's, it's not very loud could be another person's TURN IT DOWN!!!

Is this sub ported? If so, and you have a spare amp, you could hook it up to any amp just to test it. Just run a wire through the port and to the speaker. Just don't push the amp hard if it isn't rated for 4ohm. Just test with it. Just be careful trying to remove the woofer. It can be easy to bend thin frames. I find that the flat blades made for patching dry wall work well for prying stuck on drivers. Do at your own risk though.

As for the boomy subs, you can try stuffing the ports and see if you like that better. Some sub manufactures put peaks around 60-80hz to make the sub louder. I plugged a old Infinity BU-1 many moons ago and I liked it a lot better.