car speaker question

[grsmith021]

I got some car subs from someone who said that they had them wired up inside their house. Supposedly they wired the amplifier to the stereo receiver and the speakers to the amplifier and thats all that had to be done. Seems to me that there needs to be 12v power supply? Just hoping for some help and if this is actually plausible.

Thanks

 

[KeepItSimpleStupid]

There are powered subs, subs and dual voice coil subs.

So, the answer is maybe it requires 12V. In general, you need to limit the high freuency content to the subs.

 

[4pyros]

Only if you are using a 12v amp. Most home equipment runs off AC mains voltage IE 110 volts AC.

 

[audioguru]

Hi power car amplifiers have a DC to DC converter that converts 13V from the car battery to plus and minus 35V or more.

Car speakers are usually 2 ohms or 4 ohms so the high current in them will produce high output power.
Home speakers are usually 8 ohms and use an amplifier that has a high output DC voltage to produce high power.

 

[grsmith021]

so does that mean that the amplifier will need 35v to function? If I wire it to my stereo receiver will that be enough to power it. My stereo receiver is rated at 200W and has two channels. Don't know if the power is divided by the number of channels but wondering if it would have a high enough voltage/not too high to power a sub looking for around 35V.

 

[audioguru]

An amplifier needs a power supply voltage that it was designed to use.
We don't know if you want your receiver to drive the sub-woofer or if you want the car amplifier to drive it.
We don't know the impedance of the sub-woofer. If its impedance is lower than your receiver can drive then your receiver might blow up.

 

[4pyros]

are thay powered subs or just speakers?

 

[grsmith021]

Ok so I found out a little more. I am not sure about the impedance, I bought the speakers from a friend a don't have any documentation. I figured out the amplifier is broken so I just wired the car subs to the my receiver and while they do play at a decent volume I was wondering what the most practical way to get them to their full power. Being that my receiver is 200W and the subs are 1000W and don't have a functional amplifier.

 

[audioguru]

The sub speakers must have had a manufacturer and probably have a datasheet. Your stereo the same. Impedance is very important.
Car speakers usually have a low impedance of 2 ohms to 4 ohms that will destroy a home amplifier designed for 8 ohm speakers.
Usually a sub has its own amplifier and a filter that feeds it only very low frequencies.

 

[grsmith021]

Cool, thanks. So I looked into it and the speakers have an impedance of 4 ohms, and my receiver is set up for 8 ohms. How much do you think I should worry about this?

 

[audioguru]

Cool, thanks. So I looked into it and the speakers have an impedance of 4 ohms, and my receiver is set up for 8 ohms. How much do you think I should worry about this?

Since the amplifier is designed for an 8 ohm speaker and your 4 ohm sub is halfway between 8 ohms and a dead short then the current in the amplifier is doubled which might cause it to blow up.

 

[KeepItSimpleStupid]

You can place the speakers in series to get 8 ohms and only use one channel of the AMP without any problems.

You can mount a couple of 4 ohm 200 W resistors in series with your speaker and be OK.

Two of these https://www.parts-express.com/pe/showdetl.cfm?Partnumber=019-020 in parallel will be 4 ohms, 200 W.

Place a set in series with each speaker and you will be fine. You will need 4 resistors, total.

They will get warm.

Good amps will have ratings at different speaker impeadances (Z) (4, 8 and 2 are common). The lower the Z, the more current it draws. If the amp can't supply it then you RISK letting out the "Magic smoke".

 

[audioguru]

A modern woofer or sub-woofer has its resonance damped by the extremely low output impedance of a modern amplifier. The amplifiers have a rating called "damping factor" and their output impedance is 0.04 ohms or less.
Adding speakers in series or adding a series resistor ruins the damping and causes a modern speaker to sound "boomy".
Old vacuum tube amplifiers frequently had a very poor damping factor so old woofers had built-in damping and could be connected in series.

 

[KeepItSimpleStupid]

Interesting. But you mean modern amplifiers. The speaker design has't changed much except for magnetics and the lack of an electromagnet.

What's worse?

My amp has 30 amp drivers, but the PS is only rated for 3 with 9600 uf/rail (2 rails per channel). I'd have to look up the SOA. Safe Operating Area.

 

[audioguru]

Look at the "damping factor" spec for any half-decent modern amplifier (not a cheap C****** one). It has a very high damping factor of 200 to thousands. When the amplifier tells the speaker to move then it moves immediately with no delay. When the amplifier tells the speaker to stop moving then it stops immediately.

If there is a resistance in series with a modern speaker then it takes time to begin moving and rings back and forth until it stops. It sounds like "one-note-bass" at the undamped resonant frequency. Boom-boom like a bongo drum.