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Bridging Question!

O

OOZMAN

Jun 16, 2010
909
12
Australia
www.facebook.com
#1
First up, the FAQ and search didn't come up with any results.

Secondly, here are the power specs for my amp:
8ohm: 450Wx2
4ohm: 750Wx2
2ohm: 1000Wx2
8ohm bridged: 1500W
4ohm bridged: 2000W

Now for my question. (+ is positive, - is negative)

Currently I am running my two 8ohm cabs in stereo, at 450Wx2. Can I change my amp to bridge mode, and wire my cabs like:

+ amp to + cab1,
-cab1 input to +cab2,
-cab2 to - amp,



Therefore bringing my watts up!? :D
Question 2: will this make my cabs run at 4ohms all up?

IMO this all sounds too simple/good to be true, so I'm doubtful, hence the thread.

Also, I drew a VERY basic diagram in MS Paint. :D Enjoy!

Thank you guys in advance and sorry about teh n00bn3ss.


peace
 

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#3
The way you wired the cabs in your diagram will result in 16 ohm load.
When bridged to a 16 ohm load, that amp will push the same power as two channels (dual mono) into two 8 ohm load, which is what you are doing currently.

To increase power, run your cabs parallel (4 ohm), and bridge that amp.
 
#4
Dr. Eagle said:
Running the two cabinets in parallel will result in 4 ohm load. Wiring them in series will increase the load and therefore decrease the volume.

http://www.termpro.com/articles/spkrz.html
Click to expand...

Thank you very much for the link, it helped a lot! :D

So basically, if I wire them like this, it'll be 16 ohms, and if I wire them in parallel; 4.

Me has an idea. :smug:

EDIT: What babebambi said.
 
#5
Okay! I did it! Wired in parallel, 4ohms, 2000W. I haven't been able to turn it up yet (family is here :crying: ), but the signal output lights on my amp come on at about twice the volume, soooo... I dunno, that must mean it's not working as hard to make the same amount of watts... probably. :hiding:

At 900W, my system literally shook the roof of the house quite audibly from outside, I can't wait to turn it up to the full 2000W. :D:D:D:D:bassist::bassist::bassist::bassist::hyper::hyper::hyper:
 
#6
OOZMAN said:
Therefore bringing my watts up!
Click to expand...
Bringing your watts up serves absolutely no purpose whatsoever. And doing so is not the reason for bridging. Bridging should be used when the voltage swing of one amp channel is insufficient to drive the speaker to full output. Bridging doubles voltage swing. If your amp will drive your speakers to full output without bridging then the only thing you'll gain in so doing is a far greater likelihood of blowing your drivers.
 
#10
Bridging an amp puts two channel in series, so the available output voltage is doubled.

Putting two identical loudspeakers in series halves the voltage to each one.

Doing both results in the same available voltage to each loudspeaker as having one on each channel, and with the added disadvantage that a fault anywhere--like a speaker failure, for example--will silence the entire rig.
 
#11
BassmanPaul said:
+1 to that Bill posted. Check how much power each of your cabinets is rated for. They will be getting up to 1KW each. Remember that the power rating of a cabinet is typically thermal. That means the power when the voice coil melts and fails.
Click to expand...

Yeah I was going to ask/bring up the topic on my speakers max watts. The speakers didn't come with an RMS rating, but they did come with a peak: 1600W each. They are cheap, yes, so I don't think the RMS rating would be too much over 1000. What do you guys think?

At the risk of losing internet popularity, I must say I find it a little funny when someone with a bigger rig for less money comes and makes a thread/post about it, and other guys get all jealous and say negative things about it and that I'm doing it wrong etc. C'mon guys! Chillax! You're turning the internet into a very anti-social place! Oh wait... :D:hiding:

No offence intended! *Grabs energy shield*

peace
 
#14
babebambi said:
thermal rating is typically half of peak rating
mechanical limit is again typically half of thermal limit
Click to expand...

Then my speakers should be dust already... :hmm:

I tried a "subwoofer test" which is just an mp3 I downloaded with a sine wave that gradually goes through all the frequencies and random combinations of frequencies, yadda yadda yadda...

Turned it up so my amp was barely clipping, and the speakers seemed to take the abuse quite easily i.e. I thought the travel (xmax or whatever) of the cones were not extremely far for 15s. Sooooo... I have a feeling that my speakers could handle more power than the 450W each the amp was giving them.

Don't get me wrong, it's loud as heck, but I thought... heck if I got more power... why not use it? I dunno... what was the question anyway? :D


peace
 
#15
OOZMAN said:
At the risk of losing internet popularity, I must say I find it a little funny when someone with a bigger rig for less money comes and makes a thread/post about it, and other guys get all jealous and say negative things about it and that I'm doing it wrong etc. C'mon guys! Chillax! You're turning the internet into a very anti-social place! Oh wait...

No offence intended! *Grabs energy shield*

peace
Click to expand...

well you did ask for feedback on your idea.
if billfitzmaurice and Bob Lee (QSC) both advise against it, I'd listen to them. they're trying to help you understand and are not being anti-social.
No offence intended!
 
#16
OOZMAN said:
I have a feeling that my speakers could handle more power than the 450W each the amp was giving them.
Click to expand...
The only way to know that is to measure the voltage applied. Chances are the power level you think they're getting is between four and ten times higher than the actual. I can say that with total certainty, as the likelihood of your drivers being able to take 450w each without releasing magic smoke is slim and none, and Slim just left town.
Don't get me wrong, it's loud as heck, but I thought... heck if I got more power... why not use it?
Click to expand...
Magic smoke.
 
#17
OOZMAN said:
Then my speakers should be dust already... :hmm:

I tried a "subwoofer test" which is just an mp3 I downloaded with a sine wave that gradually goes through all the frequencies and random combinations of frequencies, yadda yadda yadda...

Turned it up so my amp was barely clipping, and the speakers seemed to take the abuse quite easily i.e. I thought the travel (xmax or whatever) of the cones were not extremely far for 15s. Sooooo... I have a feeling that my speakers could handle more power than the 450W each the amp was giving them.

Don't get me wrong, it's loud as heck, but I thought... heck if I got more power... why not use it? I dunno... what was the question anyway? :D


peace
Click to expand...

Two choices - take the free advice from folk who make their living doing this - OR - keep pushing your stuff until it breaks. Your call. ;)
 
#18
billfitzmaurice said:
The only way to know that is to measure the voltage applied. Chances are the power level you think they're getting is between four and ten times higher than the actual. I can say that with total certainty, as the likelihood of your drivers being able to take 450w each without releasing magic smoke is slim and none, and Slim just left town.
Click to expand...

Little confused.. do you mean from the wall socket?

And just to clarify, each cab has two 15"s, not one if that's what you're thinking. :)
 
#19
Hi.

OOZMAN said:
Little confused.. do you mean from the wall socket?
Click to expand...

If I may step in a bit, no, not from the wall, from the amp output terminals.

If the amp circuitry is a familiar one, measuring the power draw from the supply side can be used to draw conclusions about the probable output power.

Like You may remember, guessing the output power doesn't work. You have to measure it, no way around it.

Regards
Sam
 
#20
OOZMAN said:
And just to clarify, each cab has two 15"s, not one if that's what you're thinking
Click to expand...

yeah, some 15"s can handle the 200+ watt you are pushing with the 8 ohm load (half of the 450w you quoted), but only barely

I don't think any 15"s can mechanically handle the 500w of bass you would be pushing when bridged.

which amp and which cabs are you using?
 

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