minisystem is too loud...

[Crappopotamus]

its a stupid electrical volume knob, so it doesnt get very quiet before it turns off entirely. however, the volume goes UP really high. so i was thinking i could throw some resistors or something onto the speaker wires and get it quieter.

but of course i dont know what the hell im doing. first off, do i use resistors? and second, how would i go about figuring out the correct value resistance to use? help would be much appreciated.

 

[Crappopotamus]

bump

 

[MPankau]

I would be very careful just ;throwing; in resistors - you can change the impedance of the speakers and very easily fry your -minisystem. I'm no electronics major - just a sound pro. Someone else would have to tell you the proper wiring to do it right.

MP

 

[Howard]

Originally posted by: MPankau
I would be very careful just ;throwing; in resistors - you can change the impedance of the speakers and very easily fry your -minisystem. I'm no electronics major - just a sound pro. Someone else would have to tell you the proper wiring to do it right.

MP

How would increasing the impedance fry the "system"?

 

[f95toli]

You can use what is known as a L-Pad.
It consists of two resistors, just make sure they are rated at least 10W each.

Try this link:
http://www.lalena.com/audio/calculator/lpad/help.shtml

In your case the "driver" is the speaker. All you need to know is the impedance of your speakers (probably 8 or 4 ohm) and how many dB you want to attenuate.

Another, perhaps simpler, solution is to buy a L-Pad. You can buy one where they sell car audio equipment.

 

[IamElectro]

Originally posted by: Howard

Originally posted by: MPankau
I would be very careful just ;throwing; in resistors - you can change the impedance of the speakers and very easily fry your -minisystem. I'm no electronics major - just a sound pro. Someone else would have to tell you the proper wiring to do it right.

MP

How would increasing the impedance fry the "system"?

Changing the speakers impedence ie. adding a resistor can change the voltage drop across the speakers. If the system is designed specifically for those particular speakers impedence it could cause the amp to play hotter than normal and possibly fry the system.

As amplifier output impedance rises, these differences in frequency response are exaggerated. The changing speaker impedance actually pushes the output voltage of the amplifier around thereby changing the acoustic output of the speaker. The amplifier cannot control its own output voltage. and could also cause problems.

just my 2 cents.

 

[uart]

Originally posted by: IamElectro

Originally posted by: Howard

Originally posted by: MPankau
I would be very careful just ;throwing; in resistors - you can change the impedance of the speakers and very easily fry your -minisystem. I'm no electronics major - just a sound pro. Someone else would have to tell you the proper wiring to do it right.

MP

How would increasing the impedance fry the "system"?

Changing the speakers impedence ie. adding a resistor can change the voltage drop across the speakers. If the system is designed specifically for those particular speakers impedence it could cause the amp to play hotter than normal and possibly fry the system.

As amplifier output impedance rises, these differences in frequency response are exaggerated. The changing speaker impedance actually pushes the output voltage of the amplifier around thereby changing the acoustic output of the speaker. The amplifier cannot control its own output voltage. and could also cause problems.

just my 2 cents.

1. Increasing the speaker impedance will not harm the amplifier.

2. Increasing the speaker impedance could very slightly change the stabilty margin and frequency response of the amplilier, however the amount of added resistance needed for your purposes is very unlikely to have any significant impact here.

3. Adding series resistance to the speakers does slightly alter the frequency response of the speakers themselves. In particular it makes them less damped (by reducing the electrical damping component) which may actually slightly increase the base response. If this was a super expensive set of speakers of exceptional quality with a perfectly flat frequency response then this might be an issue. If on the other hand this is only a fairly cheap system then I doublt that this will be a serious concern. It's personal tastse so try it and see, but you may even find that the new frequency response is somewhat preferable (if indeed you can notice any difference at all that is).

4. If you use a "constant resistance attenuator", which is really just an appropriately designed voltage divider (see F95's link to what he calls "L-Pads") then you overcome any concerns that you may about changing the speaker impedance from the amplifier's perspective. Note however that even doing this does not totally overcome the issues I mention in point 3 above, as the impedance looking back from the speaker to the amp is still increased by the presence of the voltage divider. (That is, these "L-Pad" networks are only "one way" constant resistance). Note however that they still do improve the damping situation considerably over the simple series resistance approach.


My recommendation for a first attempt would by to just add a series resistance of similar ohms to the speaker and about half the RMS rated wattage per channel. This will give you about 6db attenuation and is unlikely to make too noticable differnce to any frequency response.

 

[Crappopotamus]

bump. i will have to reread those posts. seems pretty complicated and involved. :| damnit all.

 

[Peter]

That's what you get from asking in Highly Technical ...

 

[f95toli]

You can actually buy L-Pads so you do not even have to build it, just go to a shop that sells car audio, they can help you.

 

[NeoPTLD]

Originally posted by: f95toli
You can actually buy L-Pads so you do not even have to build it, just go to a shop that sells car audio, they can help you.

Buy two 2 to 5 W 20ohm resistors and connect one in series with either speakers. Since "minimum volume" is too loud, which would be like 1/25 of a watt, resistor wattage isn't even a concern here.

 

[drag]

You have to be a bit carefull.

Different speaker have different omh ratings. Like 8 ohms or 4 ohms or whatever. So if you have a 4 ohm speaker and stick a 4 ohm resister inline with the speaker the resister will be obsorbing the same amount of energy as the speaker and can get hot. Also make sure you get a nice enough one to handle the wattage.

Also you WILL get some degragation to the sound quality. Resisters do have uncontrolable effects on frequencies and stuff, but the effect is very small. You probably won't notice the difference.