[andyr]

..... If impedances drop to below 2R, then yes, I'd say the 55W AKSA is not suitable ...Hugh

Can I ask why the simple solution of adding a (suitably nice-sounding!) 1 ohm res in series with these 2 ohm drivers will not solve the problem?

This is a no-no in a passive setup because it reduces gain and mucks up the carefully calculated crossover -3dB point but, in an active setup with individual gain controls on each band ...??  This is what I have done with my 2 ohm Maggie ribbons, to "turn them into" 3 ohm ribbons, so my AKSA 25 would be able to cope (actually, I used 20 x 20 ohm, 1/2w Beyschlags in parallel).

Or am I missing some essential truth here?  

Regards,

Andy

[Davey]

Andy,

For Maggies or other resistive-load drivers this wouldn't be a problem.....you'd get the sensitivity reduction as expected, but it shouldn't cause any other effects.

However, with the conventional woofer drivers of the Orion system an added series resistance would cause not only a sensitivity reduction but it would add to the Qes specification of the drivers and change the roll-off characteristic of the system.  The active crossover/EQ of the Orion system is designed not only to compensate for dipole cancellation, but also a Q-correction of the rather low Q Peerless drivers that Siegfried has selected.  Thus, a change to the woofer EQ portion of the Orion crossover would be required if the Orion design was changed by adding these resistors.  You wouldn't get any design change help form Siegfried on this either.....if a person modifies one of his designs they better know what they're doing because he won't hold their hand.  

The paralleled woofers of the Orion system would indeed present a very low resistance, but only in a small area of the frequency range above their resonant peak.  This can be a problem for some amplifiers.

Cheers,

Davey.

[andyr]

Thanks, Davey.

Am I correct, with Siegfried's Orion you have 2 choices to power the woofers:
1.  An amp channel for each driver ... so you need 4 amp channels which have to be able to cope with 4 ohm loads (easy!) or
2.  An amp channel for a pair of parallelled drivers - which is how the load drops to 2 ohms?

If this is correct, I would've thought the answer is a no-brainer - if you're building Orions, you're trying to build an "ultimate" speaker ... so, as 4 amp channels is always better than 2, an amp channel for each driver is the way to go!

Regards,

Andy

[Builder Brad]

Filipe et all

I would not use the 55 AKSA kits to drive the woofers in the Orion. When I originally started to look Hughs kits I wanted to use the 100s to drive the tweeters, albeit with tweaks for Hf duty. I thought I could get away with 100s on the mids and planned to either stick with the 4 x 300w monos currently driving the woofers or look elsewhere. I know that the dipoles present an easy load to the amps but I tried a couple of other lower power amps on the woofers and nothing matched the 300w monoblocks currently in use.

I know that the amps driving the woofers are a little excesive but they really do work well with the Orions. I originally used 6 chanels of amplification until I found the time to add another pair of 300 watt monos, and really felt the difference. This made me wonder how much further I could take things so I added a pair of SL Thors - with another pair of 300 watt amps - I can really feel the bass.

If the AKSA`d tweeter and mids work well with the Orion I will certainly then build another pair of 100s for the woofers and probably use the four redundant 300w monos to create two slightly larger bridged amps to drive the Thors - what do you think?

I just cant wait for the kits to arrive in the post.....

Brad

[Davey]

Andy,

Yes, a separate amplifier channel for each of the woofer drivers is the preferred setup, and the one I think most Orion owners are using.

Looking at it from a purely objective point of view the AKSA 55 amplifier would appear to be marginal for this usage, but not by much.  I took the liberty of loading the relevent information into SL's spreadsheet to analyze the situation.  Those interested can download it here:  http://home.comcast.net/~dreite/Temp/830452.xls
 
The "Limited SPL" tab shows the items of interest.  The transition points are approximately 22Hz and 80Hz.  Below 22Hz the Xmax of the driver is the limiting factor, between 22Hz and 80Hz the voltage swing capability of the amplifier, and above 80Hz the current capability of the amplifer.  (I made an estimate for the peak current capability of the amplifier into this load based on its 8ohm power rating.)
However, SL's spreadsheets can be a bit deceiving because everything is "tilted" at a 12db/octave rate which represents the excursion increase requirement (from any driver) to maintain equal SPL as you go down in frequency.  In real usage the excursion requirements of the driver are weighted more so and amplifier capability less so than would appear in these graphs.  If you mentally tilt the graphs to the right you can get a better idea.  I hope that's clear to everyone.    Also, (as I mentioned in previous post) there is a considerable amount of equalization applied to the woofers in the Orion crossover which weights the excursion requirments/limitations even more.

Yes, more amplifier power will increase the SPL capability of the woofers at frequencies above 22Hz, but it's not really useable...in a sense...because most folks won't be listening that loud.  I use a 60W/channel amplifier to power each of the drivers in my Orion system and I've never found myself wanting for more power.  Occasionally, the woofers will bottom but this is usually the result of some hidden non-musical low frequency information that is contained on the CD and not an amplifier limitation..per se.  The THOR system (or similar) is required if a person wants to listen LOUD and LOW.

A 300W amplifier (as mentioned by Brad) is complete overkill from an objective standpoint, but I do realize there's a significant subjective aspect to most audiophiles systems.    However, high-powered amplifiers do represent a possible damage threat to the woofers so it's good to be careful.    There is quite a bit of information related to suitable amplifier choices for the Orion system on Siegfried's website.

An eight-channel amplifier system consisting of four AKSA 55 (for the mid and tweeter) and four AKSA 100 (for the woofers) would appear to be an excellent setup for the Orion system.

Cheers,

Davey.

[andyr]

Andy,

Yes, a separate amplifier channel for each of the woofer drivers is the preferred setup, and the one I think most Orion owners are using.

Looking at it from a purely objective point of view the AKSA 55 amplifier would appear to be marginal for this usage, but not by much.  I took the liberty of loading the relevent information into SL's spreadsheet to analyze the situation.  Those interested can download it here:  http://home.comcast.net/~dreite/Temp/830452.xls
 
The "Limited SPL" tab shows t ...

Thanks, Davey, for the confirmation about 8 amps.  I've played with that spreadsheet before and I thought it in fact refers to amp current/voltage requirements of sealed-box woofers (because you have to give a box volume in Box 2).

Or does it work for dipoles simply by putting Box Volume = 10,000 litres as I see you've done?

Regards,

Andy

[Davey]

Yes.  10,000 liters is a LARGE box.

Also, you can enter a front/back dipole path length in block 8 "D" and then click the "max SPL @ Vpeak" to analyze the SPL differences between box and dipole systems.  You can see why dipole systems require much more excursion and/or drivers to provide the same SPL levels.  

Davey.

Or does it work for dipoles simply by putting Box Volume = 10,000 litres as I see you've done?

Regards,

Andy

[aurelius]

Hi all,

Just thought I'd post my block diagram and artwork for my GK-1R + Orion board discussed on page 1 of this thread.

The crosover is designed to do 2 things:

1) Allow the bass speakers of the Orion to be driven from the GK-1R pre-tube "sub out" or from the standard post-tube output, selectable by a switch driving a relay.

2) Provide a subwoofer-orion (thor-orion circuit) crossover plus subwoofer equalisation.  Again, sub-woofer in/out is selectable by switch driven relay.



The board for this circuit also includes +ve and -ve jung super regulators and powersupply caps, as shown below (almost finished):



Can anyone see anything wrong with this approach?

[PT914]

Hi Aurelius,

Neat, lots of options.

Question, what is the function of a buffer?  Will the buffer eliminate the need of the output de-coupling cap on the GK-1?

Thanks,
Philip

[aurelius]

Hi Philip,

The buffer is there to:

1) Give the circuit a known and fixed input impedance, making it an easy load to drive.
2) Make the filter characteristics of the downstream filter blocks independent of the output impedance of the upstream circuit (in this case the GK-1).

The output cap (C21) of the GK-1 is still required.  The DC voltage across C21 is somewhere in the vecinity of 45V (much higher than the rail voltage of the op-amp circuit).

Your question did prompt me to thing about DC, however, and I realised that I have a DC path with gain between the input and subwoofer output.  I think I will duplicate the 2Hz HPF section from the woofer output to the subwoofer output, just to be safe.

Regards

Mark

[AKSA]

Hi Mark,

Beautiful work, elegant engineering.....

Cheers,

Hugh