monoblock amps, impedance, and why i feel like i'm taking crazy pills while working.
 

i was always under the impression that whatever ohm load you presented a D Class amp with, that's what it was going to play at. for example, if you wire a DVC sub to 8 ohms, the amp is going to see 8 ohms.

i had a customer come in and, very loudly, proclaim that if you wire it to 8 ohms, you can "bridge" a mono amp to 4 ohms.

i figured i'd just see if this was even in the realm of possibility before i spit on the guy when he comes back into the store.

the guy must be retarded you can't bridge a mono amp

how do you bridge one channel? your also correct about the impedance, if the sub is wired to 8 ohms, the amp see's 8 ohms... that guy is an idiot

if the sub is wired to 8 ohms, the amp is gonna see 6 to ~ 100 ohms depending on the frequency its outputting.

Theres nothing to "Set" an amp to as far as resistance. the ohm rating is simply how close to an completely closed circuit the amp can withstand before the fet circuts that actually do the amplifying catch on fire.

An amp rated at .5 ohm can basicly handle a close to straight short circuit without overloading.


now if he was talking about taking two 8ohms subs and presenting a 4ohm load then thats a different story. Hes still an idiot tho.

i was just completely speechless when he told me he was going to bridge his mono amp for more power. i honestly had no idea what to say.

i think i've heard just about every possible ludicrous statement in just 5 months at best buy.

and no, he was just talking about wiring up one dual 4 ohm sub.

i agree, at CC in the 8ish months i have been there im still floored by the stupid stuff i hear.

ie. this guy was a computer engeneer who was running at bazooka 300 rms amp with an infinity reference 12 inch sub (300 rms also). he swore he needed 0awg wire, he sat there with a paper and calculated the amps/wtf ever else and determined he had to have 0awg... i may be the idiot here but every set up similar to that i sell 8awg wire and there is never a problem :lol: we even have charts set up for amps/feet to determine the proper wire size

computer engineers dont take courses in electrical resistance and current requirements :D maybe he just wanted the lowest line resistance possible because an 8ga wire can carry more than 100amps (~1500wRMS) at car voltages without getting hot.

I think this must be some internet legend, or something. Crossfire mono amps have two + and two - output blocks -+-+...its so you can have more than one pair of speaker leads, or can parallel at the amp, or whatever...still only one set of outputs. Anyway, I've had a couple people tell me that if you use the first neg, and the far end +, you can 'bridge' the amp, and get more power. A couple have even done it, and swear they can hear more bass.

what can you do...

Toby

that's kinda what i did to my with my kenwood mono block amp but it's not really bridging

you cant "bridge" a mono amp...its already done inside the amplifier....as far as the dual 4 ohm sub goes.....you can wire the sub by bringing it up to 8 ohms and bring it back to 4 ohms at the amp...say on a mtx thunder they have 2 + and 2 - output speaker lines....it doesnt make any sense though...the best scenario would be a dual 2 ohm sub and having the same thing done with the sub and presenting the amp with a 2 ohm load....you get almost double the power from 4 ohms to 2 ohms...just my .02