Audio amplification for old bookshelf speakers?

[spkack]

I have an old set of Boston Acousitc bookshelf speakers I'd like to connect to a PVR system I just built. I used spare parts that I had to build the PVR, so the sound card is an old SounBlaster Live! Value that came from an older system.

I am getting sound from the speakers, but no where near what it should be. It's obvious I need some sort of amplifier for them, but I don't want to use a stereo amplifier to do it.

Anyone know of a decent (relatively inexpensive) amplifier (with power pack or USB driven) that will amplify these 60W speakers?

If the amplifier gets too expensive, it makes more sense for me to purchase a set of powered speakers for this system. I'm just trying to use what I already have.

Thanks!

 

[George Powell]

If you can plug the speakers straight into the soundcard then they must be very old indeed. The last time that I came across passive speakers on a new build computer was back in 1998.

I would be tempted to go for a pair of new powered speakers, PC speakers have come on a long way since the days of soundcard amplfied passive ones.

 

[0roo0roo]

are u sure those are bookshelf speakers? why would they have 3.5mm plugs?
i swear there used to be some usb soundcard/15wattish computer speaker amp sold at frys, but that was years ago and i haven't seen em since. its cheaper to just buy new computer speakers. or buy used home audio equipment.

 

[spkack]

Yes, they're old style stereo bookshelf speakers. They date back to the mid 1980's and have direct wire "spring" type connectors on the back where you connect bare wires. I have them converted from that connection to the 3.5mm connector via an adapter. They're still in great shape and produce terrific sound from my Yamaha AV receiver, but I just invested in new speakers for that system so these older ones get put in the spare room. Was just hoping to utilize them elsewhere since they are still in great shape.

 

[YOyoYOhowsDAjello]

Sonic T-amp?

 

[spkack]

Originally posted by: YOyoYOhowsDAjello
Sonic T-amp?

Yep! This is what I was looking for - just need to add the power pack so I don't have to keep replacing batteries. I wonder if 15W will be enough to power my 60W speakers and get adequate volume??? Any ideas roughly how many watts per channel a typical sound card produces?

Thanks, YOyoYOhowsDAjello, Good suggestion.

 

[YOyoYOhowsDAjello]

Originally posted by: spkack

Originally posted by: YOyoYOhowsDAjello
Sonic T-amp?

Yep! This is what I was looking for - just need to add the power pack so I don't have to keep replacing batteries. I wonder if 15W will be enough to power my 60W speakers and get adequate volume??? Any ideas roughly how many watts per channel a typical sound card produces?

Thanks, YOyoYOhowsDAjello, Good suggestion.

I have never looked up power output on a soundcard.

Do you know the sensitivity of the speakers? It might be written on the back label. (would say something like 85dB)
Or do you have the model number, we might be able to look it up.

EDIT: You might also consider a used integrated amp / receiver off ebay
http://electronics.listings.ebay.com/Ho...14970QQsbrsrtZdQQsocmdZListingItemList
http://electronics.listings.ebay.com/Ho...94903QQsbrsrtZdQQsocmdZListingItemList

EDIT2: oops, forgot you said you didn't want to use one

 

[George Powell]

Sound cards these days don't produce watts per channel. They only provide a line level out.

As for is 15W enough to power my 60W speakers you run into the what watt scenario.

Passive speakers have 2 measurements that give an indication of how loud they can go.

The first and more important is speaker sensitivity. This is usually measured in decibels per watt at one meter distance from the speaker. Hifi speakers vary typically from about 85 to 91. This means that a normal speaker will produce between 85 and 91 decibels of sound pressure one meter from the drivers when provided with one watt of power.

The second figure is maximum power handling of the speaker - in your case 60W per channel (think box).

A 15W amplifier should have no trouble at all at making them go to neighbour annoying volumes.

However in practice most amps - especially cheap ones tend to distort the sound when pushed too hard.

 

[YOyoYOhowsDAjello]

There are some measurements at the bottom of this page on the t-amp.

(NSFW ads)

http://www.6moons.com/audioreviews/sonicimpact/t.html

Into 8ohms, after 5.5 watts the distortion picks up rapidly

If your speakers have a pretty good sensitivity you should probably still be ok... and certainly better than whatever your soundcard is doing.

 

[EvanAdams]

The best way to ruin a good set of speakers is to underpower them. So buy some powered PC speakers or the cheapest Stereo reciever/amp you can find.

 

[spkack]

Great suggestions! I'll take a look at it all and let you know how I make out.

Thanks to all for your help.

 

[spkack]

Well, I received my T-Amp and gave it a shot. It worked as anticipated, but the sound quality was not very good - a lot of buzzing at all levels, and could not get the volume up beyond "normal" listening mode (which indicates to me the speakers are underpowered). I'm no expert, so it could also be the sound the SB Live! is putting out which is causing the problem. The speakers work fine and sound great when connected to my Yamaha A/V receiver, so I have to believe it's either the T-Amp or the sound card causing these problems. It was worth a shot, and I appreciate everyone's input on this. Looks like the only (best) solution is to go back to EvanAdams suggestion and see if I can get a used A/V receiver/amp to power these babies.

 

[YOyoYOhowsDAjello]

Have you tried hooking the t-amp to another source to see if it's the soundcard that is the problem? (like using the amp with a cd player or mp3 player, etc?) Have you tried changing the output level on the soundcard end of things? Do you have a set of computer speakers you can plug in and see if they work right when connected to the SB? Are you using batteries or a power pack to power the t-amp?

I'm sorry this didn't work for you. Even with just a few watts output, I thought it would have been significantly better than your soundcard's output.

When I needed cheap power, I got a used Sherwood receiver off ebay for $40 shipped. I agree that it's probably the way to go for you, but I thought you were pretty set against using one.

 

[spkack]

Originally posted by: YOyoYOhowsDAjello

I'm sorry this didn't work for you. Even with just a few watts output, I thought it would have been significantly better than your soundcard's output.

No need to be sorry. It was a great suggestion, definitely worked better than the soundcard output alone, and was exactly what I was looking for. It just hasn't worked out yet. I'm sure I'll be able to use the T-Amp in another situation.

At the time I purchased the speakers (mid 1980's), they were considered one of the best in their league. It could just be that they don't pair well with what I'm trying to do. As I said earlier, I had them lying around not being used so I thought I'd put them to good use. No harm, no foul. Thanks for the suggestion - I know more now than I did when I started the project!!

 

[YOyoYOhowsDAjello]

Originally posted by: spkack

Originally posted by: YOyoYOhowsDAjello

I'm sorry this didn't work for you. Even with just a few watts output, I thought it would have been significantly better than your soundcard's output.

No need to be sorry. It was a great suggestion, definitely worked better than the soundcard output alone, and was exactly what I was looking for. It just hasn't worked out yet. I'm sure I'll be able to use the T-Amp in another situation.

At the time I purchased the speakers (mid 1980's), they were considered one of the best in their league. It could just be that they don't pair well with what I'm trying to do. As I said earlier, I had them lying around not being used so I thought I'd put them to good use. No harm, no foul. Thanks for the suggestion - I know more now than I did when I started the project!!

I'm glad you're not mad at me

I've been considering getting one just to play around with it, but I really don't have any use for one yet.

 

[Slammy1]

You could just get a cheap solid state amp, should be pretty cheap esp if you can find it used at a used electronics store (aka, the pawn shop).

 

[YOyoYOhowsDAjello]

Originally posted by: Slammy1
You could just get a cheap solid state amp, should be pretty cheap esp if you can find it used at a used electronics store (aka, the pawn shop).

I thought about trying a pawn shop when I was looking to get a bass shaker amp, but maybe I've seen Pulp Fiction too many times.