To bridge or not to bridge?

[CheapAss]

First time installing a bigger system in my car, need a few tips.

What I'll be using is a 4 channel amp to power 2x 10" drivers and probably a few smaller mids/tweeters.

The 2 channels I intend to run the drivers through are 'bridgeable', but here's the thing .. the drivers came from a home stereo system and are therefore rated at 8 ohms. The way I see it, I have 2 choices here.

A) hook up one driver to each channel, 8 ohms, stereo

or

B) bridge the channels, run the drivers in parallel, 4 ohms, mono


I was planning to try it both ways and just see which sounded better and what setup would deliver the most power.

Any thoughts?

 

[lsiberian]

First time installing a bigger system in my car, need a few tips.

What I'll be using is a 4 channel amp to power 2x 10" drivers and probably a few smaller mids/tweeters.

The 2 channels I intend to run the drivers through are 'bridgeable', but here's the thing .. the drivers came from a home stereo system and are therefore rated at 8 ohms. The way I see it, I have 2 choices here.

A) hook up one driver to each channel, 8 ohms, stereo

or

B) bridge the channels, run the drivers in parallel, 4 ohms, mono


I was planning to try it both ways and just see which sounded better and what setup would deliver the most power.

Any thoughts?

All you get is a 3db gain in max volume by doubling your power. This is not worth the effort bridging requires. Don't chase power. Instead chase sound quality which is all about the drivers.

 

[j_garcia]

All you get is a 3db gain in max volume by doubling your power. This is not worth the effort bridging requires. Don't chase power. Instead chase sound quality which is all about the drivers.

Bridging doesn't require any effort with a bridgable amp, however this also typically halves the impedance that the amp can handle in bridged mode. You are still driving two drivers as well, regardless of the impedance, so that will still draw more current than one 4 ohm driver. If the amp can handle it, it should work, but you'll need to be careful if it starts to distort because you could quickly damage the drivers if the amp can't take it.

 

[lsiberian]

Bridging doesn't require any effort with a bridgable amp, however this also typically halves the impedance that the amp can handle in bridged mode. You are still driving two drivers as well, regardless of the impedance, so that will still draw more current than one 4 ohm driver. If the amp can handle it, it should work, but you'll need to be careful if it starts to distort because you could quickly damage the drivers if the amp can't take it.

What he's talking about is bridging the amp to run the speakers in parallel though. That's crazy and I don't see the benefit.

If it were a single driver then of course you'd bridge it, but with 2 drivers I'd just run 1 one on each side.

 

[TLS Guy]

First time installing a bigger system in my car, need a few tips.

What I'll be using is a 4 channel amp to power 2x 10" drivers and probably a few smaller mids/tweeters.

The 2 channels I intend to run the drivers through are 'bridgeable', but here's the thing .. the drivers came from a home stereo system and are therefore rated at 8 ohms. The way I see it, I have 2 choices here.

A) hook up one driver to each channel, 8 ohms, stereo

or

B) bridge the channels, run the drivers in parallel, 4 ohms, mono


I was planning to try it both ways and just see which sounded better and what setup would deliver the most power.

Any thoughts?

Unless your amp can handle a two ohm load stereo, you will fry it. If it only handles four ohms stereo, then it must see 8 ohms bridged. There are many amps and speakers blown up by bridging.

 

[highfigh]

All you get is a 3db gain in max volume by doubling your power. This is not worth the effort bridging requires. Don't chase power. Instead chase sound quality which is all about the drivers.

But running the woofers in parallel alone will yield a 3dB increase without doubling the power if the impedance were to remain the same. Add 3dB for doubling the power and it's definitely worth it to bridge the amp. Also, car audio is made to see 4 Ohms or less (not necessarily when bridged, though), so the load is what makes the amp happy and using an 8 Ohm load in a car stereo is a waste of power. If it's a decent amp, 4 Ohms when bridged will be fine as long as the power cabling and ground are installed correctly.

 

[highfigh]

First time installing a bigger system in my car, need a few tips.

What I'll be using is a 4 channel amp to power 2x 10" drivers and probably a few smaller mids/tweeters.

The 2 channels I intend to run the drivers through are 'bridgeable', but here's the thing .. the drivers came from a home stereo system and are therefore rated at 8 ohms. The way I see it, I have 2 choices here.

A) hook up one driver to each channel, 8 ohms, stereo

or

B) bridge the channels, run the drivers in parallel, 4 ohms, mono


I was planning to try it both ways and just see which sounded better and what setup would deliver the most power.

Any thoughts?

What amp and woofers are being used?

Some tips for trouble-free operation:

-Use the proper size of power and ground cable. I'll post a link for a site that has a power cable chart and other info that should help.
-DO NOT ground the amp to the package shelf- only ground it to the floor pan of the car. Sand the paint away and use a star washer for the ground screw. Go under the car after everything is in and undercoat the screw and sheet metal where the ground screw is exposed.
-Add a heavier ground wire from the car body to the battery negative post. By adding the amp, your car body ground wire has instantly become too small. That's only there for the lights, wiper and blower motors and accessories.
-Install a fuse or circuit breaker within 12" of the positive battery post. This is for your safety. Closer is better but be reasonable. I like breakers that can be opened manually because it makes working on the system easier after it has been installed.
-NEVER run your audio cables parallel to any other wiring harnesses unless they're more than 12" away and if you must cross another harness, do it at a right angle. This will minimize noise pickup.
-If you hear whining when the motor runs and the pitch goes up and down with the RPM, you have a ground loop. How hard this will be to correct depends on the car and tereo equipment but it can be eliminated

http://www.the12volt.com/

Look around the link before you run cables and make your connections.

 

[CheapAss]

Bridging doesn't require any effort with a bridgable amp, however this also typically halves the impedance that the amp can handle in bridged mode. You are still driving two drivers as well, regardless of the impedance, so that will still draw more current than one 4 ohm driver. If the amp can handle it, it should work, but you'll need to be careful if it starts to distort because you could quickly damage the drivers if the amp can't take it.

What he's talking about is bridging the amp to run the speakers in parallel though. That's crazy and I don't see the benefit.

If it were a single driver then of course you'd bridge it, but with 2 drivers I'd just run 1 one on each side.

Exactly. Seems like the best bet, and simplest, will be to just hook up one driver per channel.

What amp and woofers are being used?

Some tips for trouble-free operation:

-Use the proper size of power and ground cable. I'll post a link for a site that has a power cable chart and other info that should help.
-DO NOT ground the amp to the package shelf- only ground it to the floor pan of the car. Sand the paint away and use a star washer for the ground screw. Go under the car after everything is in and undercoat the screw and sheet metal where the ground screw is exposed.
-Add a heavier ground wire from the car body to the battery negative post. By adding the amp, your car body ground wire has instantly become too small. That's only there for the lights, wiper and blower motors and accessories.
-Install a fuse or circuit breaker within 12" of the positive battery post. This is for your safety. Closer is better but be reasonable. I like breakers that can be opened manually because it makes working on the system easier after it has been installed.
-NEVER run your audio cables parallel to any other wiring harnesses unless they're more than 12" away and if you must cross another harness, do it at a right angle. This will minimize noise pickup.
-If you hear whining when the motor runs and the pitch goes up and down with the RPM, you have a ground loop. How hard this will be to correct depends on the car and tereo equipment but it can be eliminated

http://www.the12volt.com/

Look around the link before you run cables and make your connections.

Thanks highfigh, lot's of good tips in there.

DRIVER SPECS (10" High-power polycone woofer)
Nom imped 8ohms
Pow hand 160wrms
Freq rang 29hz-2500hz
Sens 91dB 1watt 1meter
Voice coil res 6.9ohms (Re)
Mech Q fact 7.632 (Qms)
Elec Q fact 0.364 (Qes)
Tot Q fact 0.347 (Qts)
Eq vol 98Lt (Vas)
Cone area 0.0346 (sq m)

most of the above detail mean nothing to me


AMP SPECS (link) - VERY SIMILAR TO, NOT THE SAME, mine is just an older model I believe
Power / channel @ 4ohm 14.4V: 130WRMS x 4
Power / channel @ 2ohm 14.4V: 190WRMS x 4
Power / bridged @ 4ohm 14.4V: 380WRMS x 2
Signal/Noise ratio: >90dB
Input sensitivity: 200mV to 5V
Low pass filter: 50 - 500Hz @ 12dB/octave
High pass filter: 50 - 500Hz @ 12dB/octave
Pass thru RCA: Yes
Dimensions: 400(L) x 258(W) x 50mm(D)

I hope that helps.

 

[highfigh]

Exactly. Seems like the best bet, and simplest, will be to just hook up one driver per channel.





Thanks highfigh, lot's of good tips in there.

DRIVER SPECS (10" High-power polycone woofer)
Nom imped 8ohms
Pow hand 160wrms
Freq rang 29hz-2500hz
Sens 91dB 1watt 1meter
Voice coil res 6.9ohms (Re)
Mech Q fact 7.632 (Qms)
Elec Q fact 0.364 (Qes)
Tot Q fact 0.347 (Qts)
Eq vol 98Lt (Vas)
Cone area 0.0346 (sq m)

most of the above detail mean nothing to me


AMP SPECS (link) - VERY SIMILAR TO, NOT THE SAME, mine is just an older model I believe
Power / channel @ 4ohm 14.4V: 130WRMS x 4
Power / channel @ 2ohm 14.4V: 190WRMS x 4
Power / bridged @ 4ohm 14.4V: 380WRMS x 2
Signal/Noise ratio: >90dB
Input sensitivity: 200mV to 5V
Low pass filter: 50 - 500Hz @ 12dB/octave
High pass filter: 50 - 500Hz @ 12dB/octave
Pass thru RCA: Yes
Dimensions: 400(L) x 258(W) x 50mm(D)

I hope that helps.

If you notice, car stereo amps aren't usually rated for 8 Ohms. The reason is that with a 12VDC system, it's harder to have the high voltage for the power supply and until relatively recently (the last 20 years), real high power wasn't possible or practical, so using Ohm's Law to show that decreasing the speaker's impedance develops higher Wattage at the amp's output, you'd be defeating this benefit by using one 8 Ohm speaker on each channel. If you want the most from the amp and speakers, connect them parallel and bridge the two channels into one. You already showed that it's rated for 380W into a 4 Ohm load when bridged. Since the other channel won't be capable of that output, you'll need to decrease the input signal to the sub's channel, but you also won't need to worry about overpowering the woofers.

 

[CheapAss]

If you notice, car stereo amps aren't usually rated for 8 Ohms. The reason is that with a 12VDC system, it's harder to have the high voltage for the power supply and until relatively recently (the last 20 years), real high power wasn't possible or practical, so using Ohm's Law to show that decreasing the speaker's impedance develops higher Wattage at the amp's output, you'd be defeating this benefit by using one 8 Ohm speaker on each channel. If you want the most from the amp and speakers, connect them parallel and bridge the two channels into one. You already showed that it's rated for 380W into a 4 Ohm load when bridged. Since the other channel won't be capable of that output, you'll need to decrease the input signal to the sub's channel, but you also won't need to worry about overpowering the woofers.

Good stuff

I intend to run tweeters/mids off the other two channels. The amp has built-in crossovers so I wanted to run an RCA cable from the head unit (rear output only), through Y-splitters to all four channels, bridge channels 1 and 2 for the drivers, hook up the tweeters/mids as per normal to ch 3 & 4 then adjust the crossover levels to suit the drivers and tweeters/mids.

What do mean by 'decreasing the input signal to the sub's channel'?


edit-
PS the drivers aren't subs. They were originally designed to use as woofers in a home theatre system.

This system is going in the back of my wagon. The front speakers I'll just run off the head unit for now, but I want 90% of the sound coming from the rear of the vehicle. Being an open back wagon the drivers will not be 'covered' as if they were running from inside the boot/trunk so it'll basically be a loud-box if you get what I mean.

 

[highfigh]

Good stuff

I intend to run tweeters/mids off the other two channels. The amp has built-in crossovers so I wanted to run an RCA cable from the head unit (rear output only), through Y-splitters to all four channels, bridge channels 1 and 2 for the drivers, hook up the tweeters/mids as per normal to ch 3 & 4 then adjust the crossover levels to suit the drivers and tweeters/mids.

What do mean by 'decreasing the input signal to the sub's channel'?


edit-
PS the drivers aren't subs. They were originally designed to use as woofers in a home theatre system.

This system is going in the back of my wagon. The front speakers I'll just run off the head unit for now, but I want 90% of the sound coming from the rear of the vehicle. Being an open back wagon the drivers will not be 'covered' as if they were running from inside the boot/trunk so it'll basically be a loud-box if you get what I mean.

The amp doesn't have crossovers for tweeters or mid-range, for that matter. They do have crossover points for sub/mid-bass but that's as far as it goes.

"The front speakers I'll just run off the head unit for now, but I want 90% of the sound coming from the rear of the vehicle."

If you have never been a car that was set up this way, try to find one, usually at a car audio contest. There's always someone who sets their system this way and it's really annoying to listen to. Having bass from the back and mid/treble from the front won't sound right, good or real because the crossover point is too high. If it was a matter of crossing the sub/mid-bass at 40Hz - 60Hz, it would be less of an issue but I have heard this kind of system and if you turn your head, it's hard to take.

I did car audio for a long, long time and know what a loud box is. I also built many systems that ended up in competitions and while these events weren't the goal in most of them, they still won some awards.

90% of the sound coming from the rear will never sound natural. Our ears are oriented so we can hear better from the front, not the rear. When someone goes to a musical event, backing in and facing away isn't how most people listen. We don't put the speakers behind us when we set up a stereo or home theater, either. If you want to hear great sounding car audio, go to a competition, like an IASCA event. They always have loud boxes and while they don't always win in the sound quality department (Iasca has well-defined guidelines for imaging and sound quality), you can see how people are building their systems.

This site may help:
http://www.mobileelectronics.com.au/forums/index.php?