Forget the Sonic T amp.

[Seth=L]

I am a tinkerer of sorts and had a great idea not long ago to use a computer speakers amplifier to power full range speakers. It sounds like a silly proposal, but I gotta say I couldn't be more satisfied.

At Wal-Mart they sell a 2.1 PC speaker system for $24.99 before tax. The system is from a reputable company, Altec Lansing. Just in case you were wondering, the model number is "121i".

Here is a link- http://www.alteclansing.com/product_details.asp?pID=121i

What comes in the box is the powered woofer, two satelites, and a familiar green color coded 1/8" mini-jack cable. It is very easy to hook up and provides the average user with reasonably good sound from a set of $25 speakers. but it has it's problems, like lame 2.5" single driver satelites and a pathetic, boomy, cheasy 4" "sub".

Needless to say I am not the average consumer, and right away I was trying to figure out how to make the thing sound better. I did find that if you take a almost empty paper towel roll and push it into the bass port it decreased the SPL's but, decreased boominess, and increased the extension. This made it sound better but not satisfactory.

So it sat in a box for a few weeks, then it dawned on me. Why not connect some efficient bookshelf speakers to it. After all the Sonic T amp isn't breaking ground as a powerfull amp and neither are single ended triode tube amplifiers.

It just so happened that I had some reletively nice and efficient bookshelf speakers, Infinity Interlude 10s. The powered 4" woofer has speaker clip terminals instead of 1/8" mini-jack or RCA jacks. The speaker clip terminals will accept 16 gauge wire, so that is what I used.

The front of the "sub" has one tone knob, and volume knob and a woofer volume knop. The woofer volume knob is marked as "BASS". Now you can turn the woofer all the way down on the unit, unlike some other PC speakers where the sub is always on. There is also a very bright, annoying blue LED on the front that you may want to cover with electric tape.

I figured to utilize the "sub" unit as an amp would be to just disconnect the woofer, that way I know that it is not robbing me of power, even though it probably isn't necessary. To disconnect the woofer, be sure it is unplugged, remove the ten screws on the outer edge of the amplifier plate on the rear. There may be some glue holding the amplifier plate in place, but it should still come out relatively easy to remove.

Once the amplifier plate is off you may find somethings semi-surprising. The first thing I notice is the output stage has discete transistors, all equal in size. The power ratings state 5.5 watts RMS for the 2 channels and 9 watts for the woofer. I figure after removing the woofer from the loop that frees up some watts for the 2 channels. The power rating also states 20 watts RMS system power, so I am probably only going to get something shy of 10 watts per channel if I really need it. It also has two 2200uF caps and a descent size power transformer, considering.

Anyway, back to disconnecting the woofer. There are several removable cable clusters, on 2 wire black and green is the woofer. If it is not black and green, just check and see which 2 wire bundles is coming from behind the woofers mount. The best way could be to disconnect it from the amp and tape it to the side of the box, in my case I took the woofer entirely out of the enclosure (note that I had to cut the wire to do this).

How does it sound?:

I put it back together once I had removed the woofer and proceeded to do a test a using my NHT 1.5s. Of course it did the 1.5s no justice, they just aren't efficient and as they are acoustic suspension they don't have much bass to start with. Puny amps and bass light speakers just don't work.

Next I tried the Infinity Interlude 10s, much better. These speakers have a tendacy to be bass heavy anyway so the Altec did a little more than round it out, but in near field who needs tons of bass anyhow?

The good:

There are a lot of things to be liked here. The attenuation knobs all move smoothly. The tone knob can tame the highs down, that is a very nice feature instead of fixed highs. Now that the speakers that came with it where naturally dull so they needed lots of highs to sound right, so I am surprised it wasn't fixed frequency. The enclosure is very basic, unlike many of the PC speakers you see that are kind of gawdy and unsightly. It has one 1/8" mini-jack in, so you can get your own 1/8" to RCA stereo cables. It has discrete transistor output stage. And most importantly, IT IS CHEAP!

The Bad:

No bass control, and the thing is weaker in the bass department. Then for that you could buy the Sonic T preamp. There is also the annoying blue LED on the front, but you can fix that with some tape. The power switch is rear mounted so if the enclosure is somewhere hard to access you may want to just leave it on at all times. And lastly it doesn't have lots of power, but that is the competition here, low powered amplifiers.

Conclusion:

If you want descent sound on the cheap and you have some extra speakers laying around, I know I do, then, hey it is only $25. If you don't have speakers You could get those Insignia NS-B2111s for $50 at Best Buy.

Here are some pictures, there will be more posted below, where the unit is taken apart and the sub or power woofer is taken out.

The main unit itself in my living room, it is know powering more efficient BIC floorstanders-

And the rear-

It looks nasty on the back because I got tired of air leaks before when I was still using it as a pc speaker system.

So I just thought I would share this wonder with the world, I hope that someone will try it out and post what they think.

 

[Rob Babcock]

Very ingenious! Another suggestiong, although not quite as cheap, is the Griffin PowerWave. It's a 10 or 15 WPC (depending on the impedance) amp was designed ostensibly for Mac's, I think, although it's not white or styled like a mac. It works well with PCs, too having both line level inputs and USB. I used it for a long time to run bookshelves fed by my PC, and lately I've kept it in my laptop bag to use as a headphone amp (it works fantastically for that!).

Now I have an NAD C-320BEE integrated at my PC, with the USB output feeding my Stereo-Link USB DAC. Good as it sounds, in some ways I think the cheapo P-Wave was better!

The P-Wave is about $90, though. No volume control, it relies on your PC or MAC for that.

 

[Seth=L]

Thank you, that is very interesting. I will have to look that one up.

Sorry I forgot a few details here. I am using a Pioneer Elite PD-65, Radio Shack 1/8"-stereo RCA, Magnavox 16 gauge speaker cable, and Infinity Interlude 10 bookshelf speakers.

I swear if you heard what this thing sounds like you would be stunned, I know I am.

 

[Ampdog]

I could be misunderstanding you Seth, but if you meant that you were using the (separate) sub-amplifier as full range, perhaps some caution. As these amplifiers are not intended to handle much higher than a few hundred Hz, they are sometimes not designed to be clean at all audio frequencies (easier to accomodate NFB over a narrow band, etc.). Some are also used in some +/- current feedback system particularly tuned to control the speaker they drive, but I would expect that in high-end systems only.

Anyway, you would probably have detected it if it was a limited bandwidth amplifier or such.

 

[Seth=L]

It has discrete output transistor stage and the one used to power the sub is not being used at this time. The reason for not using it is to allow the other two upper range output channels get everything the power supply and caps have to offer. The only limitation of brandwidth is a forced low-end roll-off which happens to even out my naturally boomy Infinity Interlude 10s. The amp has yet to get hot, only mildly warm.

Here are some pictures of the unit taken apart-
Top view of amplifier unit-

Side view of amplifier unit-

Output devices, three transistors for discrete output-

The green and black powered woofer cable-

Powered woofer cable removed from circuit-

This is where the woofer was-

This is the power supply-

 

[Seth=L]

----repost, or edit, whatever.

 

[xboxweasel]

Cool. I like playing around with stuff sometimes too. Home grown mods.

I always wanted to make my own speakers. No money for materials though. However, I am keeping my eye open on garbage day for wooden furniture. I might find a piece big enough to make a pair of bookshelf speakers.

 

[Seth=L]

Cool. I like playing around with stuff sometimes too. Home grown mods.

I always wanted to make my own speakers. No money for materials though. However, I am keeping my eye open on garbage day for wooden furniture. I might find a piece big enough to make a pair of bookshelf speakers.

I vant to beeld zubvoofer.

 

[xboxweasel]

Haha. The only reason I want to try this/came up with the notion is because a speaker manufacturer (can't remember who) is making speakers out of old kegs. They said the aged wood makes for a better cabinet.

 

[mardelgo]

I’m thinking of doing the same with my Logitech Z-2300,(add a pair of bookshelf’s) only that I plan to keep the subwoofer. I did some mods, to improve the sound but the speakers of this 2.1 systems still perform subpar. With some equalization the sound improve, but still far to recommend to any audioholic. Here are some pics.The las 3 pict, are the mods.The amp has 2 10,000mf caps by the way...

 

[Seth=L]

I’m thinking of doing the same with my Logitech Z-2300,(add a pair of bookshelf’s) only that I plan to keep the subwoofer. I did some mods, to improve the sound but the speakers of this 2.1 systems still perform subpar. With some equalization the sound improve, but still far to recommend to any audioholic. Here are some pics.The las 3 pict, are the mods.The amp has 2 10,000mf caps by the way...

Holy shite, it has a toroidal power supply! That is superb!

I think that that system could hold a lot of value as a stereo amp and sub. Of course it is all in the eye of the beholder, but some of us on a budget can't ignore such great, cheap audio opportunities.

 

[nav]

Haha. The only reason I want to try this/came up with the notion is because a speaker manufacturer (can't remember who) is making speakers out of old kegs. They said the aged wood makes for a better cabinet.

Pioneer is using whiskey barrels.

 

[Seth=L]

That was very interesting to read about. Thanks nav.

They even made the bass ports out of wiskey barrels, and they also said it takes a whole barrel to make one pair of these speakers.

 

[xboxweasel]

Pioneer is using whiskey barrels.

That's the one. I thought it was Pioneer.

Thanks.