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I have an active tri-amped stereo pair. Each woofer channel consists of a 12"/8 ohm pair driven by a 400 wpc/8 ohms, 750 wpc/4 ohms stereo power amp. For both bass channels there are a number of possible configurations:
1. Drive each 12" with identical signals using a Y-splitter = 400 watts per 8 ohm woofer
2. Drive both 12" connected in parallel (4 ohm), power amp in bridged mode = 1200 watts/8 ohms, bridge mode output not specified into 4 ohms
3. Drive both 12" connected in series (16 ohm), power amp in bridged mode = 1200 watts/8 ohms, bridge mode output not specified into 16 ohms
4. Drive both 12" connected in parallel (4 ohm), power amp in parallel mode = 1200 watts/8 ohms, bridge mode output not specified into 4 ohms
My goal is bass driver control. What configuration do inmates suggest and why? I have never used the parallel configuration. What advantage/disadvantage does it have?
Follow Ups:
Just to "second" the motion, as I think has been established by earlier posters with knowledge of the topic, parallel those puppies and don't bridge the amp.
XO frequency seems reasonable for a 3-way stereo config.
Next... what about 150 Hz and beyond?
Stay away from the bridging of power amps
Instability because of load impedance, and very easy to toast loudspeakers in the bridged mode.
Sonics are affected and heat is an issue
Damping factor as stated in one of the posts is a BIG deal if you want a tight control of that woofer
You will NOT have good driver control bridging that amp
Heres what happens with the damping thing...
Lets say you run a kick drum /pulse at high output
The woofer pushes out with the pulse and comes back and bounces from
that pulse
If you have a high damping factor the woofer will snap out with the pulse
and recover quickly for the next pulse
With poor damping that woofer will snap out and bounce for a period
of time
Lets compare it to a car with shock absorbers that are good (good damping)
You hit a bump the car recovers quickly and you maintain tight
control of the road
When the shocks are shot (poor damping) then when you hit bumps
the car bounces wildly up and down. Then the car continues to hit
bumps and the car just keeps bouncing wildly up and down.
That is the best analogy I can think of
Run the amp in a stereo configuration
If you cant get what you want out of 400watts @8ohms for home stereo
then your doing something wrong
If you think you need more power then simply get an amp that will
give you more power into an 8ohm load
to 'pro sound guy'
So are you saying that in bridged the dampening factor is usually or always worse then in stereo?
is this dependent on the amp?
i have four dual 18" grund 3600 gt boxes running off 4 different amps, all in bridged mode. all a little over powered.
making a mistake?
It would be best if you gave us the model number and or ratings of the woofers to help best determine the power requirements.
If you have a STEREO setup-then you need to run a seperate amp to each woofer-so you can rule out any impedance combinations you are thinking of.
Also you will get the most control with a non bridged amp. When you bridge-you put the output stages in series-there for doubling the drive impedance-therefore cutting the damping factor in half.
The best way to get the most control is to use short-large cable with good solid connections on each end.
THe high damping factor numbers on the amps are quickly overshadowed by the connectivity numbers between the amp and the loudspeaker.
The drivers are Peerless XLS 830500. I believe power handling is 600 wrms. They are used 2 per channel with active crossover Linkwitz-Riley low pass at 150 Hz. Am I correct that you consider 1 stereo amp per channel non bridged the best configuration? How does a parallel switch on the amp compare to bridged? I assume it is a configuration which does not reduce the damping factor. Is this correct?
There are 2 meaning of "parallel" on amplifers. The old Crown MA/MT (and others) had ove version, and everybody else has a different meaning.
On everybody else the parallel switch simply puts the inputs in parallel (just like using a Y cable on the input) and a loudspeaker hooks to each channel as normal and the sound of the channel is unchanged.
On the particular Crowns, you take a large wire and physically tie the 2 HOT/RED terminals together and flip the parallel switch. This is done while in the OFF position.
WHat this does is use the front end of channel 1 to drive the output sections of both amps (which are tied together) and enables the amp to drive a 1 ohm load.
The "secrret" that is told, is that response above 5Khz goes downhill quickly when doing this.
When you go Bridge, the sound is basically unchanged, but the damping factor of the amp is half of a single channel-as the channels are run in series with each other and the output impedance is ADDED together. So if the output impedance is normally 0.01 ohms, in bridged it will be 0.2 ohms.
If you run a bridged amp into a 4Ohm load you will need an amp that is stable into a 2Ohm load as bridging halves the load the amp 'sees'. Not that many amps are stable into a 2 Ohm load.
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