Speaker level inputs, waste of amp power?

[yepimonfire]

ok so i have a small 2 ch setup with 80hz extensions in the low end, needless to say its not as thunderous as my main system, and compared sound quite flat and empty. i was thinking of adding a sub using the speaker level inputs, but the amplifier can only deliver a total of 50wpc and i know that alot of power is used up reproducing the low end, would i be wasting much of my power using speaker level inputs? how does this work?

 

[j_garcia]

What do you mean by wasting power? A powered sub won't use any power from your receiver/amp. A passive one will and depending on the sub, it will use a lot.

 

[yepimonfire]

i mean where is the power that is put through the sub going? the amp is obviously sending out a full range signal, but 80 hz and below would never reach the speakers.

 

[TLS Guy]

ok so i have a small 2 ch setup with 80hz extensions in the low end, needless to say its not as thunderous as my main system, and compared sound quite flat and empty. i was thinking of adding a sub using the speaker level inputs, but the amplifier can only deliver a total of 50wpc and i know that alot of power is used up reproducing the low end, would i be wasting much of my power using speaker level inputs? how does this work?

I don't think your post makes any sense to any of us. What is a speaker level input for Heaven's sake?

 

[lsiberian]

They are called line level inputs and the power from the amp is simply filtered and sent to two different sources. Your mains and the sub.

Basically your post makes little sense because you don't understand crossovers. I suggest you do some reading on them.

 

[Seth=L]

I don't think your post makes any sense to any of us. What is a speaker level input for Heaven's sake?

Speaker level inputs - High level inputs (not to be confused with line level inputs)

 

[TLS Guy]

Speaker level inputs - High level inputs (not to be confused with line level inputs)

I still have no idea what you are referring to here. I have never seen any thing higher than a line level input on domestic equipment, unless we are talking about a link between pre outs and amp in that some receivers used to have.

So I still have no idea what the OP is trying to ask us.

 

[markw]

Two answers in one post.

I still have no idea what you are referring to here. I have never seen any thing higher than a line level input on domestic equipment, unless we are talking about a link between pre outs and amp in that some receivers used to have.

So I still have no idea what the OP is trying to ask us.

First off, there are a myriad of subwoofers that offer speaker level inputs as well as line level inputs. There's more out there than your rarefied world wants to acknowledge. IOW, you should broaden your scope of available products.

Second, to the OP, as far as "wasting power", it's not an issue. While your amp will be producing the bass, it will be at the same level as the rest of the spectrum. The sub crossover/amp will "siphon off" the bass frequencies it handles and generally provides a high impedance load to your amp at the frequencies it handles. The sub will then provide any additional amplification you want. End result, no additional strain on your amp. If anything, you might want to use the filtered "speaker outputs" on the sub to keep the bass away from your bass-shy mains.

 

[yepimonfire]

sorry for the confusion, i understand x-overs very well. what i mean is this, amp supplys 50wpc and supplys a full range signal, no x-over in the amp, goes directly to the high-level inputs on the sub, sub x-overs at 80hz, sends the higher frequencies to the speakers, my question is will i still be getting 50wpc to my speakers (in theory) or since i know that a large amount of power is used to drive low frequencies, will i be wasting that power by using a sub. a rough example that is probably inaccurate: 30w of low frequency information comes from the amp, 20w of mid/high freq information comes from the amp, when the sub takes over the low end will i lose the 30w or will it be redirected into the mid/high end? i want to know what is going to be happening to my power basically.

EDIT: read marks post, so basically instead of full power being drawn at 80hz down it will only be drawing small amounts of power because the imp, will be very low, so i will be able to get full amp power at 80hz+?

 

[TLS Guy]

First off, there are a myriad of subwoofers that offer speaker level inputs as well as line level inputs. There's more out there than your rarefied world wants to acknowledge. IOW, you should broaden your scope of available products.

Second, to the OP, as far as "wasting power", it's not an issue. While your amp will be producing the bass, it will be at the same level as the rest of the spectrum. The sub crossover/amp will "siphon off" the bass frequencies it handles and generally provides a high impedance load to your amp at the frequencies it handles. The sub will then provide any additional amplification you want. End result, no additional strain on your amp. If anything, you might want to use the filtered "speaker outputs" on the sub to keep the bass away from your bass-shy mains.

Now I've got it, I thought the OP was referring to his receiver.

So the OP will not waste amp power as he will be feeding into a high impedance input.

I have not seen one of those subs around for a while, but I guess they still exist.

 

[yepimonfire]

90% of the subs i have had in consideration before have them.

 

[Seth=L]

Now I've got it, I thought the OP was referring to his receiver.

So the OP will not waste amp power as he will be feeding into a high impedance input.

I have not seen one of those subs around for a while, but I guess they still exist.

There are very few active subwoofers that don't have High level inputs (signified by binding posts or spring clip terminals) You may be thinking of passive subwoofers, those are pretty dead.

 

[skers_54]

sorry for the confusion, i understand x-overs very well. what i mean is this, amp supplys 50wpc and supplys a full range signal, no x-over in the amp, goes directly to the high-level inputs on the sub, sub x-overs at 80hz, sends the higher frequencies to the speakers, my question is will i still be getting 50wpc to my speakers (in theory) or since i know that a large amount of power is used to drive low frequencies, will i be wasting that power by using a sub. a rough example that is probably inaccurate: 30w of low frequency information comes from the amp, 20w of mid/high freq information comes from the amp, when the sub takes over the low end will i lose the 30w or will it be redirected into the mid/high end? i want to know what is going to be happening to my power basically.

EDIT: read marks post, so basically instead of full power being drawn at 80hz down it will only be drawing small amounts of power because the imp, will be very low, so i will be able to get full amp power at 80hz+?

Your amp won't be sending any power to the sub, so all the power will reach your speakers. The sub inputs have a very high impedance compared to the impedance of your speakers, so the current that flows into them is very small. Therefore power dissipated at the speaker level inputs is essentially zero. Your speakers will still see a full-range, full-power signal just as if there was no sub connected. If you have speaker A and B outputs I'd recommend using the B output for the sub just for make it neater and easier to connect everything.

 

[yepimonfire]

yep. unless your buying concert subs, ive done alot of looking around for a passive sub and could never find one, theres really just no point in making them for home use because that means you have to get a new amp capable of large amounts of current around 300w at least, you need crossover equipment etc.

 

[yepimonfire]

Your amp won't be sending any power to the sub, so all the power will reach your speakers. The sub inputs have a very high impedance compared to the impedance of your speakers, so the current that flows into them is very small. Therefore power dissipated at the speaker level inputs is essentially zero. Your speakers will still see a full-range, full-power signal just as if there was no sub connected. If you have speaker A and B outputs I'd recommend using the B output for the sub just for make it neater and easier to connect everything.

no i inteded on using the subs x-over so i can get the same clean sound i get from my floors with my bookshelfs.

the reason for doing that is so i can get undistorted sound, all my speakers are from the same line, the floors and bokshelfs used in my main system have very large bass woofers and midranges along with the tweeters, the small bookshelfs im using in my 2ch system are 2-ways with very small woofers (5") and all that bass turns into distortion instead of getting that crisp sound from my floors i like so much, i get muffled bass mixed in with the mids/highs.

 

[ski2xblack]

EDIT: read marks post, so basically instead of full power being drawn at 80hz down it will only be drawing small amounts of power because the imp, will be very low, so i will be able to get full amp power at 80hz+?

Mark's answer was concise and correct. Keep in mind that when feeding a sub speaker level signals that the input impedance of the sub is so high that it is (for all practical purposes) invisible to your main amp, and all power is available at all frequencies, just as before. You will get full amp power above and below 80 hz. (Some subs, but very few in my experience, actually do have passive high pass filtering on their speaker level outs; if that's what you have, then the power below the sub's passive crossover is simply heating up the passive parts, which is still a waste, but at least you're not delivering full power at frequencies your speakers can't reproduce.)

Indeed, any amp power below the lower limits of your speakers capability to reproduce is 'wasted', but unless you're using active bass management of some sort that is the case with or without a sub.

Now, if you're really blasting it on this system you may run into trouble (you may run your amp dry pushing a full range signal, in which case you would benefit from some dedicated bass management for proper allocation of limited amp power, or bigger amps.)

 

[yepimonfire]

this is basically just a pre-pro amp, it has inputs, and a vloume control and a two band eq that is pretty useless, no digital processing at all.

 

[lsiberian]

There are very few active subwoofers that don't have High level inputs (signified by binding posts or spring clip terminals) You may be thinking of passive subwoofers, those are pretty dead.

We'll let's not get carried away. Passive subs are still used in the pro audio sector which can have overlap with consumer stuff.

But many plate amps do have L-R speaker wire input and outputs including the Dayton SU series that is the budget recommendation here.

 

[Seth=L]

We'll let's not get carried away. Passive subs are still used in the pro audio sector which can have overlap with consumer stuff.

But many plate amps do have L-R speaker wire input and outputs including the Dayton SU series that is the budget recommendation here.

Sorry, I'm thinking mostly mainstream stuff.

 

[skers_54]

But you said

no x-over in the amp

So I'm confused. Since both your sub and receiver have amps, you really need to be more specific when you describe your connections. Many subs don't actually have a high pass crossover on the speaker outputs, even though it appears that they do. Assuming yours does, you'll need to run the speaker wire through it. The high pass crossover may not be accurate as you need to take the speaker impedance into account when designing a filter. This is obviously impossible in this case so the high pass will be off somewhat. It will also change the load your amp sees; a high impedance in the low frequency region will be present.