Full range active speaker

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zebra100

Member
Joined 2008
Hi all,

I am thinking of having a go at a pair of full range active speakers based around an Audiosector LM3875 Gainclone kit. Any experience/thoughts would be much appreciated.

18mm MDF cabinets with a steel or aluminium sub chassis for the amp/psu section will be the chosen medium. I haven't settled on a driver yet, but I have a couple of ideas.

For the amps, I intend to use 18-0-18v, 120VA transformers (rail voltage around 25V).

I am just at the design/exploration stage of the project, so I won't be building anything just yet. I may even end up using the LM3875 modules and transformers from my power amp to save on cost (being a cheapskate;)).

Chris.
 
Z

zebra100

Member
Joined 2008
audio-kraut said:
What is a "active" fullrange speaker?
Active usually means a multi way speaker controlled by an active crossover.
Since a fullrange does not use crossovers - whats the point?
Click to expand...

By active I mean each speaker houses its own monobloc power amp (LM3875 GC, powering a full range driver). This negates the need for a separate power amp, although both speakers will need independent power cables and long interconnects. I also intend to use my passive attenuator for volume control utilising an Alps blue (50K dual log with 47K shunt resistors).

Chris.
 
Dr_EM

Dr_EM

Member
Joined 2006
Since you'll be using longer than usual "interconnect" leads and the signals carried by them will already be attenuated, I'd reccomend fitting the active speakers with XLR connectors and a balanced line reciever inside. You then need a balanced line transmitter at your pre-amp. Using a passive attenuator with high output impedance and long unbalanced cable runs is likely to introduce a lot of noise.
 
H

H3nry

Member
Joined 2009
Dr Em has a point. Long interconnects' capacitance driven from 10-25K impedance will roll off the top noticeably. You'd want to drive this from a low impedance preamp, or if passive, maybe a transformer-type attenuator. With a chip amp in the box you should get very good electrical damping of the driver. Downside is heat in the box from the power transformer & amp affecting the speaker's characteristics. Should be an interesting experiment.
 
Magura

Magura

Member
Joined 2003
class-a-labs.com
zebra100 said:
What would your first choice be?

I like the Gainclone sound. Detailed very detailed in the mid and treble, low distortion an not over blown in the bass department. An ideal candidate for a full range driver. I think it would be a worthwhile experiment.

Chris.
Click to expand...

Gainclones and FR drivers has IMHO never been a good combo. A current source amp like the FirstWatt amps would be a much better choice.
An F3 built as current source would offer pretty much the best of both worlds.


Magura :)
 
R

RAndyB

Member
Joined 2005
Dr.EM said:
Since you'll be using longer than usual "interconnect" leads and the signals carried by them will already be attenuated, I'd reccomend fitting the active speakers with XLR connectors and a balanced line reciever inside. You then need a balanced line transmitter at your pre-amp. Using a passive attenuator with high output impedance and long unbalanced cable runs is likely to introduce a lot of noise.
Click to expand...

I have JX92S and Hypex 180 as Chris is planning. The amps. have balanced input by default, and I have put in XLR connectors. Having not yet built balanced drivers, as a temporary measure I am using twin screen cable with the "cold" input earthed at the "driver" end. No hum and noise.

Andy
 
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