Bridging 4 channel - quick help needed!

[JaeCole 10+ year member]

Currently I am using two 4ohm dvc subs (250 rms each) hooked up to a sony gtx1852, bridged

- Walmart.com: Sony 2/1-Channel Xplod XM-GTX1852 370-Watt Car Amplifier: Auto Electronics

- http://www.imountek.com/ebay/Sony_XM-GTX1852/image_02.jpg

I want to connect the subs to this infinity reference, bridged...

- Infinity Reference 7540a 111W x 4 car amplifier at Crutchfield.com

How would I do this? Do I need to buy a y cable?

I need to know which speaker inputs I need to connect to on th infinity and whether it should be set to mono or stereo on the infinity

I'm getting total of 400 rms. With the infinity, I would get 556 rms (278x2 @ 4ohm, yes?). Would there be a noticeable difference to the ear? I'm getting a very good deal on the infinity. What class do you suspect the sony amp is? I'm not sure if it's class d...looks like a class A/B, like the infinity

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[chillin 10+ year member]

There is not enough of a power difference to really notice much. Maybe a little, but very little

 

[JaeCole 10+ year member]

So it's not worth the trouble? The amp is only going to cost me $40...I feel like 156 rms is a lot.

 

[THATpurpleKUSH 5,000+ posts]

Your subs wont work on the infinity amp unless you wire them to 8 ohms each because the amp isnt stable below 4 ohms bridged so you couldnt run the sub as 2 ohms.

 

[JaeCole 10+ year member]

Your subs wont work on the infinity amp unless you wire them to 8 ohms each because the amp isnt stable below 4 ohms bridged so you couldnt run the sub as 2 ohms.

Wait a minute...please look at the sony amp specs. Aren't I getting 400 rms @ 4 ohms to the subs, bridged? Or am I getting 200 rms @ 2 ohms? Txdog said I'm getting 400

So why can't I hook up the infinity amp at @ 4ohm bridged? This blows

 

[JaeCole 10+ year member]

Bad news...looked at wiring diagrams at crutchfield, you are right kushy_dreams

Can someone tell me how much rms i'm currently getting?

 

[THATpurpleKUSH 5,000+ posts]

Dvc 4 ohm subs can be wired to 2 or 8 ohms and 4 if yo only use 1 coil but then you should only use half of the rms power.

To run a 4 ohm load to your amp you need to have the subs wired to 2 ohms each then those are wired in series to the amp or each sub at 8ohms and wire those parallel to the amp.When you bridge the 4ch, you can only go down to 4 ohms or the amp will go into protect mode. So you can only run each sub at 8 ohms when you bridge the 4ch.

Can someone tell me how much rms i'm currently getting?

The walmart link shows 370wrms bridged at 4 ohms.

 

[JaeCole 10+ year member]

Well can you look at the sony amp specs and tell me how much rms i'm getting? it's wired to be bridged.

and i want to switch my sealed box to ported, how do i connect the speakers within the stuff in the enclosure? do i need to solder or do simply connect?

 

[chillin 10+ year member]

I didn't look that close. Looks like Kushy dreams is right. Back to your other question. 156 watts would make a big difference if your amp was only 156 watts, but since it is 400, you are only adding about 35%. Basically doubling the power will give you a 3db increase in amplitude, which does not equate to twice as loud. You can't even notice a change of less than 1db, therefor by adding less than 50% more power your db gain will definitely be less than 2 which is not that noticeable.

read this

Decibel Levels and Perceived Volume Change « ConradAskland.com

 

[JaeCole 10+ year member]

I didn't look that close. Looks like Kushy dreams is right. Back to your other question. 156 watts would make a big difference if your amp was only 156 watts, but since it is 400, you are only adding about 35%. Basically doubling the power will give you a 3db increase in amplitude, which does not equate to twice as loud. You can't even notice a change of less than 1db, therefor by adding less than 50% more power your db gain will definitely be less than 2 which is not that noticeable.
read this

Decibel Levels and Perceived Volume Change « ConradAskland.com

yeah i've heard that before, i was just looking for a cheap way to give my subs more rms....

i have a 4 channel amp feeding 75 rms x 4, if i hook it up to the infinity i gain 36 rms....i guess that's not worth it either

Well can you look at the sony amp specs and tell me how much rms i'm getting? it's wired to be bridged.

and i want to switch my sealed box to ported, how do i connect the speakers within the stuff in the enclosure? do i need to solder or do i simply connect? if i need to solder, what's the rating need for the soldering gun? i have one but forgot what the rating is

 

[JaeCole 10+ year member]

The walmart link shows 370wrms bridged at 4 ohms.

Where did 370 come from? don't see that figure. so with the sony amp, it's running @ 4ohms, not 2ohms, yes?

 

[chillin 10+ year member]

If the amp does rated power it is 400 bridged at 4ohms. He was reading the max power per channel (not bridged), but that is not rms, so it doesn't really matter.

 

[JaeCole 10+ year member]

If the amp does rated power it is 400 bridged at 4ohms. He was reading the max power per channel (not bridged), but that is not rms, so it doesn't really matter.

ok cool...so basically my amp is acting as a mono, 1 chan amp since it's bridged?

 

[THATpurpleKUSH 5,000+ posts]

The owners manual on the Sony shows 185x2 at 4 ohms, this is the cea2006 rating. Because that amp is pretty cheap (no offense intended to owner) it will most likely do this while bridged too, thats whereI got 370wrms from. If you look closer at the owners manual, it shows a max of 45a of current drawn while running 4 ohms to each channel at 185rms per channel.

If we take this figure do some math, we can get an idea of the amp's efficiency and how much power it will put out. (using y as the variable for voltages)

watts = amps x volts

370wrms = 45a x (y volts)

y= 8.2v

now we take 8.2/14.4 and this gives a figure close to the amps efficiency, 58%, which is perfectly normal for an entry level AB class amp.

cea 2006 ratings show that the amp makes x amount of power throughout the full listening range 20hz-20khz at 4 ohms at no more than 1%thd, so the amp could maybe do a little more than 380, but it could fall higher in the frequency range, out of the range that the sub could see or distortion could be through the roof. +/-20w or so wont make a difference, so its best to just rely on the clean power that you know it will produce.

ok cool...so basically my amp is acting as a mono, 1 chan amp since it's bridged?

Yes it is acting like a mono because you have bridged 2 channels into 1. Bridging doesnt always make an amp a mono, for instance bridging channels on a 4 channel will make it a 2 or 3 channel. And when you bridge channels, you can only use half the ohm rating each channel is rated for. For example if you bridge a 2ch that is 2 ohm stable per channel, you can only run the bridged channel at 4 ohms or higher.