Wednesday, December 01, 2010

CAVX Speakers are now ACTIVE!

I have always wanted Active Speakers for my own system and I am finally in a position to be able to offer these to the home cinema market as a new and exciting DIY speaker kit. I have built myself a new set of 25mm MDF enclosures that are trapezoid to help reduce internal box resonances.

Passive Speakers:

Typically a passive speaker is defined as one being driven by a single external amplifier. The power from this amplifier is then divided into high pass and low pass bands by components [capacitors, induction coils and resisters] that make up the crossover network. For this reason, speaker building has been called an 'art' rather than a 'science' as once completed, there is little flexibility to the design or how the final speaker will sound so it is an 'art' getting the balance just right.

Active Speakers:

An active speaker is one that contains separate amplifiers for each driver(s). A key benefit is that an electronic or "active" crossover is used to divide the audio spectrum into 2 or more filtered bands before amplification. Each filtered band is then amplified by separate amplifiers to drive each speaker driver in the system. The end result is a system that delivers higher dynamic range than is possible from a passive system. It has been said that when comparing an active system [say 60 + 50 watts] to a 200 watt amp, the 200 watt amp clips first! This system features 70 [LP] + 30 [HP] watts powering the VIFA drivers I was using in my own CAVX Speaker system. The built in electronic crossover is 2K/4th order [Linkwitz-Riley], resulting in no phase errors between the drivers. Because the new crossover is slightly higher than the original 1.5KHz, I had to make a slight modification to the baffles in order to keep driver spacing correct.

The reason just 30 watts can be used for the HP section is because tweeters are generally more efficient [say 95dB/1w/1m] than woofers [89dB/1w/1m]. In my case, I have 3 tweeters wired in parallel, and even though each of these ring radiator tweeters is just 91dB/1w/1m, three in parallel gives some 8dB gain and where 6dB is perceived as being twice as loud. I get a small loss in SPL due to the fact that I've wired resisters in series [after the tweeters] to bring their load to the amplifier back up to 4 ohm.

New Vs Old
The speaker on the left is the new CAVX Active speaker with ABS baffle. The speaker on the right is the original design with a passive crossover and MDF baffle. Because the new active crossover is now 2K, the spacing between centre to centre of the three tweeters had to be reduced. I therefore had to recess the centre tweeter due to the tweeter's physical size.

I conducted my first listening tests today [23/11/2010] and I am very impressed. Whilst I've always been able to play back a film soundtrack at 00dB reference levels, I typically would listen at between -20dBFS ~ -10dBFS. These speakers are clean and I was wanting to run them at 00dB reference in several instances. The reason is simply because the new active configuration lowers the distortion and to our ears, it just seems we can tolerate higher levels.

To connect an active speaker, one simply needs pre-amplifier outputs [pre-outs] on the the back of their AVR. The CAVX Active Speakers are easy to connect given that they feature a single RCA input on the back of the amp module along with level controls which will allow the end user to balance or unbalance the system as required.



Back To The Top