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The Village Idiot
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Discussion Starter · #1 ·
I'm trying to decide which plate amp to buy to modify a POS I picked up for cheap. Its an Acoustic Audio with a rather large fan base . I paid 98$ for it so it isn't a bank breaker that it turns out to be a steaming pile.

Its a 10" slot ported down firing sub with 200 watt amp and a driver that can't keep up - I've replaced it with one a neighbor sold me for 10$ - a Rockford Fosgate 10" P110s4 model.


Specs are:


Sensitivity: 85.5 dB RMS

Power Range : 50-150 Watts

Peak Power Handling: 300 Watts

Impedance: 4 Ohm

Low Frequency response: 20 Hz

High Frequency Response: 200 Hz

Diameter: 10 Inch


After putting the Rockford driver in it sounded much better. On the LOTR intro where Isuldor whacks the ring off the bad guy it actually sounded pretty good for as small as it is. Trouble is the amp gets very hot - it will blow - just a matter of time - so I need a cheap solution so I can get on with other things. The original AA driver is a dual voice coil - the Rockford is a single so I 'bridged' the dual leads from the amp to the new driver and tried it out. With single leads very little sound is produced.


So....recommendations on a plate amp for this that will work with this driver? I've looked at a few such as this
Hafler being offered up on ebay - a Foster which I've never heard of before but the price certainly is compelling. It puts out 110 watts - will that be that enough for the Rockford? I'd really like to keep this under $100 - the Rockford driver will end up beating the hell out of this enclosure as it is. Another one I've been reading up on is the Dayton SA240 . At some point I see myself visiting my buddy Mick to saw up some MDF and building a decent sealed enclosure for this.


FWIW if anyone reads that forum I linked to and is thinking of trying one - don't. I've seen fan based forum threads but have never seen one quite like that. The main 'cheerleader' of the AA subs is also a moderator and tends to mildly flame any detractors that has a bad experience - his minions do not exhibit the same restraint, following along thinking they are in audio nirvana by having one of these subs. His graphs and charts showing a 12" AA sub besting a DIY with a Dayton 15" Titanic driver is laughable. In that 'test' the Dayton barely got over 100db.
 

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Just above $100, but the PE 240w w/ Boost would probably would as well as can be expected with that drive and enclosure. I'm not sure where the high-pass is set, but it should give some protection against bottoming.


Another option a bit more in line with the overall budget nature of the build would be the surplus Foster WF-100K for $35 from the NHT Surplus Sale if there are any left. It's 110w at 4ohm, has a 29hz high-pass, and an adjustable 10db shelve can be modified using data available from the sale website.
 

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The Village Idiot
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Discussion Starter · #3 ·
The Rockford recommendation for that driver is for a 1 cubic foot sealed enclosure - nearly the same as what I have so sealing the slot should work and help the driver from bottoming out as well.


Do you think the Foster amp will drive this with any reasonable SPL levels?
 

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Keep in mind that the Rockford Fosgate reccomendation for that driver is for car-audio (enclosed space, cabin gain) as well as music (far less subsonics and near subsonics). I'd play some modeling software and compare enclosures for the driver. You know the volume (roughly) and port size/length, so you're really just comparing the FR curve and output of sealed vs. vented. Since you're looking to replace the amp anyway, you don't have any unknown boost characteristics to deal with.


I'd say the PE amp would noticeably increase output over the Foster, which may or may not noticeably increase output over the stock amp... but with the Foster amp you have a clean slate (no unknown boost) and you're not sinking a lot of money into an unknown. A $110 amp probably isn't going to make this project $75 better than the cheaper Foster amp. Buy the cheap amp to play with what you have, and buy or build a better sub when you're ready to upgrade.
 

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Very happy with several NOS Hafler/Rockford 100 W plates I have used. E-Bay for around a buck, something like that. Don't know if there are any left. I might grab a couple more myself.
 

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The Village Idiot
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Discussion Starter · #6 ·

Quote:
Originally Posted by Stephen Hopkins /forum/post/17039663


Keep in mind that the Rockford Fosgate reccomendation for that driver is for car-audio

The original driver made some horrible noises. Playing the intro to LOTR where Isuldor hacks the ring off the bad guy - when the sound visually and audibly radiates out - the only way I can describe how it sounded is like a Jake Brake on a big rig coming down a long steep incline. Not even close to the sound from my Infinity PS212 - a decent if not great sub. With the Rockford driver it sounded almost exactly like the Infinity - just not as loud.

Quote:
Originally Posted by tvrgeek /forum/post/17039709


Very happy with several NOS Hafler/Rockford 100 W plates I have used. E-Bay for around a buck, something like that. Don't know if there are any left. I might grab a couple more myself.

I just ordered 2 of the Foster amps from this guy . If they don't work out where can I get one of those? I have a link in my first post to a 220 watt Hafler on ebay - just not willing to spend $130 + for it.


The Foster amps can be bridged making them 220 watts into 8 ohms. Can they together drive a 4 ohm speaker such as the Rockford I have?
 

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Quote:
I just ordered 2 of the Foster amps from this guy. If they don't work out where can I get one of those? I have a link in my first post to a 220 watt Hafler on ebay - just not willing to spend $130 + for it.

I was late to this thread, I have 4 of Jack's amps in my garage unused.
 

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I don't think you're going to have much luck bridging them with a 8ohm load. I really wouldn't sink much more than the cost of one of the Foster amps into this unless you plan on reusing it building an HT oriented design later on. Any more than the $35 a surplus Foster 110w costs seems like throwing good money after bad.
 

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The Village Idiot
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Discussion Starter · #9 ·

Quote:
Originally Posted by penngray /forum/post/17040063


I was late to this thread, I have 4 of Jack's amps in my garage unused.

Any reason why you haven't used them yet? Are they any good?

Quote:
Originally Posted by Stephen Hopkins /forum/post/17040141


I don't think you're going to have much luck bridging them with a 8ohm load. I really wouldn't sink much more than the cost of one of the Foster amps into this unless you plan on reusing it building an HT oriented design later on. Any more than the $35 a surplus Foster 110w costs seems like throwing good money after bad.

This works out for me - I have a friend with a old sub that quit working and he's been bugging me to help him fix it. Its a single coil driver and these Foster amps are single lead output. Maybe I'll sell him one of them for the price of two.
Won't cost me anything!
 

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Quote:
Originally Posted by Knucklehead90 /forum/post/17040226


This works out for me - I have a friend with a old sub that quit working and he's been bugging me to help him fix it. Its a single coil driver and these Foster amps are single lead output. Maybe I'll sell him one of them for the price of two.
Won't cost me anything!

Now that's thinking with your dipstick, Jimmy!
 

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Discussion Starter · #11 ·

Quote:
Originally Posted by Stephen Hopkins /forum/post/17040376


Now that's thinking with your dipstick, Jimmy!

Which is why I ordered two!

And my buddies name is Jim(my)!

I'll charge him what the amp cost - I'd never do that to a friend. I just hope it'll fit on his little sub - its a plastic one - an Insignia I think. Maybe we could duct-tape it to the top His wife would love that. She likes the little bitty speakers - but can't figure out why my HT sounds better than theirs!


Funny thing - when they went shopping for a new TV she kept wanting bigger!


Typical woman.
 

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Quote:
Originally Posted by Knucklehead90 /forum/post/17040226


Are they any good?

Just wanted to drop in and say I picked up 4 of these to put onto some unpowered eD 12" subs I had left from the last upgrade and sell them on Craigslist (I'm keeping the EP2500
). I'm quite happy with the performance and believe they put out a true 110W (that's not just their "rated power" it's actual).


Funny story, I had a guy come over to look at the subs. He'd just bought an Infinity sub rated at 500W from Best Buy but was unhappy with it. He demo'd the large ported eD sub using one of these plate amps and was blown away. He didn't want to spend the $175 on the sub I was selling since he already had the Infinity and didn't want to pay for return shipping (we're in the middle of nowhere!) but asked if I'd sell just the plate amp. $75 later and he was on his way with one. I wouldn't have charged him so much but I figured if I sold it at $75 he'd be back to trade up to the ported sub for another $100 for sure. I emailed him the other day and he was ecstatic with the performance of his Infinity with the new amp. He said the "500W" infinity amp wasn't half the size or weight of the Foster amp, go figure
 

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Quote:
Originally Posted by Stephen Hopkins /forum/post/17040141


I don't think you're going to have much luck bridging them with a 8ohm load. I really wouldn't sink much more than the cost of one of the Foster amps into this unless you plan on reusing it building an HT oriented design later on. Any more than the $35 a surplus Foster 110w costs seems like throwing good money after bad.

Are you saying they are no good? Im pretty sure Jack, NHT would disagree with your opinion. You can ask jack about the Bridging, from what I have read it can be done.
 

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Quote:
Originally Posted by penngray /forum/post/17040624


Are you saying they are no good? Im pretty sure Jack, NHT would disagree with your opinion. You can ask jack about the Bridging, from what I have read it can be done.

Definitely not saying they're no-good... just saying that bridging them with a 4ohm load might be pushing the limits of their abilities... that would be the equivalent one amp driving a 2ohm load. If Jack says it can be done, I definitely believe it, but his site says they can be bridged for an 8ohm load.
 

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Quote:
Originally Posted by Knucklehead90 /forum/post/17040226


Any reason why you haven't used them yet? Are they any good?


For the $$$ they can not be beat period!!


I haven't used them for the same reason I havent used the other $2000 worth of drivers sitting in my garage



Too many projects, too little time....I couldnt pass up on them and the 10" 081s that Jack was selling many months ago. A bass bin for $70 is sick and Im happy I bought many things from him including incredible VR-3 kits! Most of the stuff now is sold out but I have great value for future projects.


Any neighbor or friend that wants speakers is going to love me
 

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Quote:
Originally Posted by Stephen Hopkins /forum/post/17040637


Definitely not saying they're no-good... just saying that bridging them with a 4ohm load might be pushing the limits of their abilities... that would be the equivalent one amp driving a 2ohm load. If Jack says it can be done, I definitely believe it, but his site says they can be bridged for an 8ohm load.

Oh, sorry I misread your post....Yeah 2 ohm wont work.


but since he has a 4 ohm driver two bridged amps giving him 200W into 4 ohms?
 

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The Village Idiot
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Discussion Starter · #17 ·

Quote:
Originally Posted by lennon_68 /forum/post/17040617


Just wanted to drop in and say I picked up 4 of these to put onto some unpowered eD 12" subs I had left from the last upgrade and sell them on Craigslist (I'm keeping the EP2500
). I'm quite happy with the performance and believe they put out a true 110W (that's not just their "rated power" it's actual).


Funny story, I had a guy come over to look at the subs. He'd just bought an Infinity sub rated at 500W from Best Buy but was unhappy with it. He demo'd the large ported eD sub using one of these plate amps and was blown away. He didn't want to spend the $175 on the sub I was selling since he already had the Infinity and didn't want to pay for return shipping (we're in the middle of nowhere!) but asked if I'd sell just the plate amp. $75 later and he was on his way with one. I wouldn't have charged him so much but I figured if I sold it at $75 he'd be back to trade up to the ported sub for another $100 for sure. I emailed him the other day and he was ecstatic with the performance of his Infinity with the new amp. He said the "500W" infinity amp wasn't half the size or weight of the Foster amp, go figure

Thats encouraging, thanks. It should power the Rockford Fosgate driver I have OK. 110 watts is in the middle of its handling ratings. Those amps are being sold for $35 each. I don't see how you can go wrong - and for under $100 for 2 its a cheap education if they prove to be dogs - which sounds unlikely with what you are saying.


I'm stuck at home today waiting for a new sub to show up - I bought an eD A5-350. It should be capable of showing my Infinity PS212 how to sound off. Not sure if the Infinity will go into the bedroom or if I should let this little sub go in there.


We shall see what we shall see - or hear in this case.
 

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Quote:
Originally Posted by penngray /forum/post/17040645


Oh, sorry I misread your post....Yeah 2 ohm wont work.


but since he has a 4 ohm driver two bridged amps giving him 200W into 4 ohms?

Not sure where I read it but Jack said he tried bridged into 4ohms and the amps went into protection so that's a no-go. I'll see if I can find it.


Edit: Found it, it's in the FAQ located on his page:


"When two WF-100k amplifiers are bridged together, the load must 8ohms or greater. I tested this setup with a 4ohm load and the amplifiers instantly went into protection. It may work with a 6ohm load. I don’t know. Into the 8ohm load, the amplifier pair delivered 220W at 1% THD at 50Hz."
 

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The Village Idiot
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Discussion Starter · #19 ·

Quote:
Originally Posted by lennon_68 /forum/post/17040714


Not sure where I read it but Jack said he tried bridged into 4ohms and the amps went into protection so that's a no-go. I'll see if I can find it.


Edit: Found it, it's in the FAQ located on his page:


"When two WF-100k amplifiers are bridged together, the load must 8ohms or greater. I tested this setup with a 4ohm load and the amplifiers instantly went into protection. It may work with a 6ohm load. I don't know. Into the 8ohm load, the amplifier pair delivered 220W at 1% THD at 50Hz."

If these amps work as well as suggested I may have to pick up a couple more before they are gone. Using 2 of them on a dual voice coil driver should produce some amazing results. Maybe a 15" DVC.


Do you have a link to that thread you are referring to?
 

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Quote:
Originally Posted by Knucklehead90 /forum/post/17040974


Do you have a link to that thread you are referring to?

Which thread? If you mean the quote from Jack I got it from the Foster WF-100k amplifier FAQ, it's the first link under the Foster amps on his page that you linked above:

http://home.comcast.net/~jhidley/


There is a thread here that Jack's been posting in regarding the items he has for sale but there's not much discussion of these amps there:

http://www.avsforum.com/avs-vb/showthread.php?t=1125860
 
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