man...
maybe its just me. i do not know. but isin't this thread driftning away a bit?
Hi,
I am planning to make a 3 way active speaker (inspired by the PMC IB1S).
I have been looking around for cheap chip amps that would suit such a speaker and i am currently considering the following (in each speaker) :
- 1x stereo LM4780 (2x60 W RMS) : tweeter + mid
- 1x bridged mono LM4780 (120 W RMS) : bass
Questions :
- Is this a good choice?
- Would it be better to use a 3883 on the tweeter & mid ?
- I've read that the bridged LM4780 gets real hot & needs a massive radiator + a fan. Any way to avoid the fan ?
- Can i use one single power supply for both the bass + tweeter & mid ? (1 PSU per speaker)
Thanks a lot. "
-> go with 4 monoblocks, LM4780 set on voltgae safe for 4 ohm loads.
-> no need to bridge them.
-> You can use a single supply for all 4 amps, but it is advised to have the bass amps on theyr own psu.
Linkwitz-Riley Electronic Crossover
there You go.
allso in the same article:
[IMGDEAD]http://sound.westhost.com/p09_fig3.gif[/IMGDEAD]
that is how You can deal with the differences in the efficiency of the drivers.
Idealy, I would assume that going for 6 monoblocks and active 3 way crossover would not add considerable costs, and can potentialy provide better quality.
In that case You would need 6 monoblocks, but no need for any kind of passive crossover element. You can run the mid and tweeter amps o the same psu, and leave the bass amps on theyr own psu.
That would be my advice.
From economy view it can happen that the active 3 way and 6 amps will be quite close in price to an active 2 way with 4 amps + 2 passive xover setup.
There are allso a gazzilion of chips that can be used.
Tweaking a passive xover is never easy. Dealing with the impedance of the drivers, accounting the losses yielded by the passive components are a challange alone. Not to mention when You might need to change any component. The costs are higher, and sometimes changin one components will force to change others too. Not cheap when we talk about inductors.
On the otherhand, 3 way active has the advantage of easy(er) tweeking, one could in case use sockets to enable quick swapping of caps and resistors to setup a new filter. Once built and set for an xover point changing the drivers will have no effect on the crossover freqvency. Speaker efficiency can be matched via a simple pot. These are features that most passive xovers do not have. In my opinion for experimenting it is a well worth investment.
You should first do a simulation of the drivers to see what kindof power requirements would the speaker it self have, maybe paralelling amps would simply be an overkill.