home stereo bridging help?
Apr 30, 2008 at 7:08 PM Thread Starter Post #1 of 11

jinx20001

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hi guys, im not sure who can help me on head fi or which part of the forum i should go to for this question, but im sure somebody in the DIY can help.

anyway my question is this, i have a very mid grade technics SCDV290 mini system in my bedroom, The amplifier isnt a load of rubbish by any means in my opinion, being grade D and all. now onto the question, i have a 12inch kenwood 1200watt subwoofer attatched as normal at the moment and it kicks along nicely, although the amp does create a lot of heat. EDIT: i should also point out ive had 2 (yes 2) 12inch car subwoofers running as normal through the subwoofer channels on this system for 2 years solid with no problems so far, now one of the subs belongs in my recent new car ofcourse. which is why im thinking about bridging this badboy up.

im happy with the performance so far but im wondering if the amplifier can be bridged, ofcourse this would quadruple the power output, giving me a nice 480watts of subwoofer power to play with but this would also make the amplifier see 2ohm i believe, and its rated at 8ohm for subwoofer output.

anyway im jabbering a bit and confusing myself a little, the main question is can i bridge the amplifier, and if i do will i have a barbecue in my bedroom??

and also, if i dont play music too long will the amplifier be ok if i dont let it burn up too long?

as i said im not sure if im in the right section, im very much a headphones fan so i spend my time in that section of head fi, any help and advice would be great guys, its nice to have the subwoofer as it is but we all want MORE POWERRRRRRRRRRRRR.

cheers, jay.
 
Apr 30, 2008 at 8:19 PM Post #3 of 11

FallenAngel

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You've had the post up for 40 minutes and you're bumping because of a "slow forum" come on buddy.

A few things I saw very wrong - you're powering a 1200watt sub (I'm guessing it's closer to 600 watts RMS with 10% THD, so effectively, nothing over 500watts should be used) with a system that has 65watts RMS! How you measure 480watts, I don't know. Are you using speaker outputs to drive it?
 
Apr 30, 2008 at 8:35 PM Post #4 of 11

jinx20001

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Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif
You've had the post up for 40 minutes and you're bumping because of a "slow forum" come on buddy.

A few things I saw very wrong - you're powering a 1200watt sub (I'm guessing it's closer to 600 watts RMS with 10% THD, so effectively, nothing over 500watts should be used) with a system that has 65watts RMS! How you measure 480watts, I don't know. Are you using speaker outputs to drive it?



cheers for replying, sorry for the early bump, i was just really eagre to try bridging this amp because its getting late on the night over here in UK so dont wanna be waking the neighbours.

the system has a 120watt RMS output for the lows and 60watt RMS for the mids and highs in stereo mode, which equals the 360watt RMS of the system, ofcourse this all changes if you use the dolby surround but i rarely watch dvd's on the system.

i figured that giving the system a 2ohm load which is effectively what im giving it if i bridge that would quadruple the wattage of the lows giving my sub a nice 480 watts to drive with, as you can imagine, driving 120 watts into a 1200watt max sub hardly makes the thing bounce. still produces a nice sound though so i imagine its fairly sensitive, not sure of specs, its not expensive being a car sub. i should point out the subwoofer connections are rated at 8ohm, by bridging the 2 sub channels i will half that twice, making my power go sky high, on any standard class A/B amp this would be an early death for sure but being a average class D amplifier im just wondering what you guys think this thing can do before it performs self combustion

you say i shouldnt use over 500watts for the sub which is a very accurate guess because it is around 400-500watts RMS, i would just love to give it that power in the home, ofcourse home stereo amps are rarely able to produce that power because realistically its not needed in the home, i was just wondering if this amp could do it and if it could,how long could i run it for flat out before its advised i switch off?? thanks again for the reply. more info would be great.

oh lets not forget it is technically a class D amplifier so it should be a little more complicated with resistors i imagine.

EDIT: oh by the way yes at the moment i am using the normal speaker outputs, the subwoofer outputs mind. the system is bi amped and bi wired.
 
Apr 30, 2008 at 9:12 PM Post #6 of 11

jinx20001

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Quote:

Originally Posted by Budgie /img/forum/go_quote.gif
Sounds risky to me.


and me
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thats why i want to try it
tongue.gif
, i just want to know if its worth trying or shall i make do with what ive got.

i should mention that im using a car subwoofer because both of my subs on the original bookshelf speakers have both been damaged somehow, both split around the rubber surround of the cones so they just fart away if i use them, theres no doubt the car sub gives me a deeper response aswell being a few inches bigger,deeper dished and ported, i just dont think im even letting it stretch with the current power which is just a shame.
 
Apr 30, 2008 at 9:13 PM Post #7 of 11

jinx20001

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Quote:

Originally Posted by Budgie /img/forum/go_quote.gif
Sounds risky to me. (If it's not mentioned in the owners manual)


so basically to bridge safely internal DIY would be needed?? thanks for the info
 
Apr 30, 2008 at 9:22 PM Post #8 of 11

jinx20001

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hey! i also have 2 high power mids and tweeters, but ofcourse dont benefit hugely from the 60watt RMS they are fed. i have not got a clue what OHM the speakers are, but they arent car speakers, more like little 8inch DJ speakers, so likely 8ohm or above, maybe 16.

so how do you guys think the amp will handle bridging those?? the mids and highs output on the amplifier is 6 ohm.

thanks for any further responses.
 
Apr 30, 2008 at 11:44 PM Post #9 of 11

nikongod

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some (many) powerful class "d" amps are already bridged. i would check before you blow up your junk.

regarding the mids and highs:
quality before quantity. if the first watt is no good, will the next 240 be any better?
 
May 1, 2008 at 3:09 AM Post #10 of 11

ericj

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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
some (many) powerful class "d" amps are already bridged. i would check before you blow up your junk.


A major consideration. I'd recommend that the OP find out what class-d chips the amp is based on and pull their datasheets. The best part of that is, if they can be bridged, the datasheet will probably say so, and how to do it.

Not all class-D amps are bridged from the getgo, though. A friend of mine drives his subwoofer off an Ashly SRA-120 bridged to mono.

Quote:

regarding the mids and highs:
quality before quantity. if the first watt is no good, will the next 240 be any better?


I concurr. class-D designs often only sound good on paper. Some of them sound OK on speakers but look terrible on the scope.
 
May 1, 2008 at 10:35 AM Post #11 of 11

jinx20001

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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
some (many) powerful class "d" amps are already bridged. i would check before you blow up your junk.

regarding the mids and highs:
quality before quantity. if the first watt is no good, will the next 240 be any better?



first off thanks to both of you for taking the time to reply. you make a good point here, i have no doubt the quality will become worse as the amplifier is simply not made to be bridged, i know this because theres no mention in the manuals and it is a fairly average everyday seperates mini system, no bells and whistles in the quality department.

when it comes to bass tho, its difficult to hear such sound as distortion, especially when the amp driving the bass is nothing special in the first place, if it was a high definition quality system such as the one in my sitting room i wouldnt even be contemplating doing some bridging as its just pointless. in this case tho the amp seems to do a fairly good job of driving two 4 ohm subwoofers off of the two 8ohm connections. technics seem to have made a decent unit, and although with these subs connected the amp gets piping hot after 30 minutes it keeps going. so im just wondering how far it can actually go, and if i bridge the connection would it cook immediately or take time?

Quote:

Originally Posted by ericj /img/forum/go_quote.gif
A major consideration. I'd recommend that the OP find out what class-d chips the amp is based on and pull their datasheets. The best part of that is, if they can be bridged, the datasheet will probably say so, and how to do it.

Not all class-D amps are bridged from the getgo, though. A friend of mine drives his subwoofer off an Ashly SRA-120 bridged to mono.



I concurr. class-D designs often only sound good on paper. Some of them sound OK on speakers but look terrible on the scope.



im pretty sure the system cannot be bridged (well i should say, its not in the manual, so not advised)

if i was going to do bridging it would most deffinately be one sub bridged to mono.

lets consider the speakers are 4ohm and connections are 8ohm now ive read somewhere that when bridging, the system sees this 4ohm speaker as half that again so it would see a 2ohm speaker, but ofcourse it really is only seeing a 4ohm speaker, if this is the case why would it damage the system by actually driving 4ohm? is it because the system is trying to pull voltage for a 2ohm load?

i will point out the amplifier is very much an entry level class D amplifier, but even so, i know for a fact it performs much better than most all in one system class A/B amps. ( well thats my opinion ofcourse ) it has driven 2 4ohm subs for 2 years easily. ok ok it was with the help of a stand up fan next to it but hey!
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