Help Strapping Amps

[Guest]

help with 2 orion d1200's, trying to strap them.

this is were im at so far

the amps come on but im not getting any sound out of the sub unless

i turn the radio up to max.then there is a faint sound like its barely on. i messed with the h/u already and made shur the sub was on and rca's were in.

what exactly is the ESP port? do i need to use that wire to connect the two. the manual is a little vauge on that?

also do i need to use a second rca in the slave amp,

book says no?

rewired the sub in a 4 ohm load and same thing.

power -green light on

ESP - yellow light on constant

Protect - red light not on

im shur im just making a noob mistake, trying to strap these.

this morning i rewired both amps sepratly to check them and both came on and ran fine @ one ohm.

[ChevyBoy]

correct me if im wrong, but thats not how you strap amps

[Guest]

found this on canadian car audio:

Strapping and bridging are generally electrically the same thing.

Seems like the term bridging is used when a 2 channel amp is bridged internally, while the word strapping is used when 2 separate amps are used. In theory any pair of normal amps can be bridged as long as they can handle the extra current. An exception is Head Unit amps as they are already Integrated Circuit amps in a bridged configuration to be able to supply the rated 20 or so watts RMS out of 12 volts.

Lets assume that an amp has a +45V and -45 Volt supply and that the output transistors dont have any loss. This is just to make the math easier. The output from that amp would be 50x sqrt2= 32 volts RMS, (rounding)

if we have a 2 ohm sub, that gives a power output of

(32x32)/2 = 500watts RMS. (Power= V^2*R)

The current will now be about 16 amps RMS

if we bridge or strap 2 of these amps, we first need to drive the "negative" amp 180 degrees out of phase. Then we connect the speaker to the positive of both amps.

Now when one amp is at +45v peak, the other is at -45v peak, providing 90 volts peak to peak to the sub, or 64 volts RMS. or 2000watts. However the current has now doubled to 32 amps RMS. So the amps must be well designed in order to handle the extra current thru the output stages and power supply. Sometimes the minimum speaker impedance is increased in order not to draw too much current.

So an amp may be 250W x2 into 4 ohms, 500 watts x2 into 2 ohms, or bridged 1000watts into 4 ohms, but NOT 2000 watts into 2 ohms because that would draw too much current.

On 2 channel amps you sometimes have a "bridge" switch to do the inverting of the second channel as well as feeding the same signal to both, sometimes you simply connect the speaker to the pos of one channel and the neg of the other channel.

When using 2 separate amps sometimes care must be taken to carefully adjust the gains of the 2 amps with a test tone, other times they can do that internally with some sort of master/slave connection.

The important thing is to read the manual.

ONE THING IS CLEAR: the amps are in series in order to double the voltage. NEVER IN PARALLEL. If you put amps in parallel, each amp's very low output impedance will act as the load to the other and will cause overload.

So If you have a 4+4 DVC sub, giving 2 ohms in parallel, you could carefully strap 2 amps according to the manufacturers directions making sure they can drive the current.

Many of the MTX amps can be "strapped" and the owners manual shows how to do that. Check their website to see if the ones you want to use can be strapped.

__________________

Zoomer

only thing i can think of is that my sub is 2ohm dvc

and mabee the amps did not like 1 ohm load

or even a series into a 4ohm strapped.

i know the rockfords have a cable that you need when you strap them, im just wondering if i need to connect these ESP connectors also?

gonna take a crack at it next weekend with another sub thats svc 4 ohm and see what happens.

if anyone see's anything else im missing, any help would be great thanks.