Hows the AKSA 100N+ at driving 16ohm loads?

ShinOBIWAN · « **on:** 16 Jan 2006, 12:20 am »

As title really.

AKSA · « **Reply #1 on:** 16 Jan 2006, 03:01 am »

Brad,

No problem at all. An easy load, but power is down to around 55W max.

Cheers,

Hugh

ShinOBIWAN · « **Reply #2 on:** 16 Jan 2006, 12:38 pm »

Quote from: AKSA

Brad,

No problem at all. An easy load, but power is down to around 55W max.

Cheers,

Hugh

Thanks Hugh just what I wanted to hear but...

@ Brad

ShinOBIWAN · « **Reply #3 on:** 16 Jan 2006, 01:31 pm »

I'll go into a little more detail Hugh so as to be sure:

I've got an AKSA 55N+ already from yourself but I'm almost certainly going to be ordering two 100N+'s on top of this.

I'm using the 55N+ on the tweeter which is a 4ohm design. The midrange is rated at around 75w continuous and will use a 100N+ into 16ohm and finally the bass driver is rated at 75w but is an 8ohm design and again powered by a 100N+.

Can you see anything objectionable to this? I'm somewhat worried about the 55N+ dealing with a 4ohm tweeter, should I be? Is there any mods that I can perform to the 55N+ to help better drive nominal 4 ohm loads?

netaron · « **Reply #4 on:** 16 Jan 2006, 06:38 pm »

Well, I may not be an expert on this, but I can assure you the 55N+ is going to be a non-issue driving a tweeter. The 55N+ drives my 4ohm load speakers with no issues whatsoever. I think the impedance issue comes in when there's a big demand for current, since tweeters use very little power, even some SET with 3.5watts of power have been used for tweeter duties by my friends.

Haron

AKSA · « **Reply #5 on:** 16 Jan 2006, 09:26 pm »

Anthony,

Haron is absolutely right. Driving a 4R tweeter for a 55N+ is a veritable walk in the park, and you will have no shortage of voltage or current.

Anthony, I should mention that impedance correction of the drivers is a VERY good idea on active systems. Most systems do not address this problem at all, with attendant problems with spatial presentation. Find some literature on this if you can and drop a Zobel, a cap and resistor in series, typically 6.8uF and 10R for a woofer, across the driver connections. This corrects for the inductance in the voice coil, and pulls back phase angle to near zero across the pass band. In turn this does not distort voltage feedback to the amp, permitting the very best imaging performance. This is important!!

Cheers,

from Simon.......

ShinOBIWAN · « **Reply #6 on:** 16 Jan 2006, 09:32 pm »

Excellent thanks all.

ShinOBIWAN · « **Reply #7 on:** 16 Jan 2006, 09:48 pm »

Quote from: AKSA

Anthony, I should mention that impedance correction of the drivers is a VERY good idea on active systems. Most systems do not address this problem at all, with attendant problems with spatial presentation. Find some literature on this if you can and drop a Zobel, a cap and resistor in series, typically 6.8uF and 10R for a woofer, across the driver connections. This corrects for the inductance in the voice coil, and pulls back phase angle to near zero across the pass band. In turn this does not distort voltage feedback to the amp, permitting the very best imaging performance. This is important!!

Interesting Hugh, very interesting actually. It never even entered my head to try such an approach but now you've got me thinking about it...

Would the whole effect be some what negated by the fact that I'm using the drivers in the most conformant part of the impedance curve? For example the Scanspeak R2904-7000 has a resonance frequency of ~550hz and, of course, a corresponding impedance peak at the same point. I'm crossing at 3.1Khz which is well away from any ill effects. As well as this I'm also using rather steep digital filters of around 150dB-300dB per octave.

Its a similar story for the ATC midrange but what about the bass driver?

AKSA · « **Reply #8 on:** 16 Jan 2006, 10:48 pm »

Anthony,

Using the drivers in their most appropriate passband makes no difference to the simple fact that a voice coil is an inductor. You can generally poo poo this concept with tweeters, as their inductance is tiny and not likely to disturb the voltage feedback signal to the amp. But the midrange and woofer are another matter; particularly the midrange, where imaging information is largely processed.

I can't say much more than this, but I've done the ABs with a speaker expert and the results are quite conclusive. Imaging is greatly enhanced with proper impedance correction.

This is born out by some work I did recently on PP SS amps. If you take feedback from the voltage amp, not from the output stage, the imaging is enhanced because the feedback signal is not disturbed by the speaker. OTOH, the slam and impact is much less, more like a tube amp, because output impedance is not reduced by global feedback. You can't have it all!!

Incidentally, all reputable driver manufacturers publish the inductance figures for their drivers. My suggestion would be fiddle around a bit!

Cheers,

Hugh