Visit to Henk van der Hoeven -- Apogee Acoustics Re-builder/Restorer

Left field choice - i heard very good things about the symphonic line Kraft which Caesar uses on MBL and used could be around 6k if lucky. 400w * 8, then doubling down to 1 ohm, loads of class A
 
Henk, what SS amps have you found really work, esp biamping Divas?
My preference if SETs are impractical is at least to go for a SS amp that is a close analogue in sound character ie tone rich/dense, creamy, veering towards dark, or more a Gryphon type character than Krell
 
Caesar has recommended that one, I'm remiss in not mentioning that already
 
Henk, what SS amps have you found really work, esp biamping Divas?
My preference if SETs are impractical is at least to go for a SS amp that is a close analogue in sound character ie tone rich/dense, creamy, veering towards dark, or more a Gryphon type character than Krell

BAT 600SE or whatever latest version is might be your ticket.
 
How about $5k for an SS amp specifically designed to be stable into low impedance loads? How does 500 into 8 ohm and 900 wpc into 4 ohms sound? It's the Sanders Magtech...I've heard it into big ML's... Stable,clean, fast and punchy... I woildn't say it was the warm side of neuteal but the effortlessness was obvious.Could be a great ticket for Diva woofers if you pile the tubes up the chain, as discussed... May be neutral enough that a not- too- tubey mid/ tweeter tube amp like a big VTL could find a nice synergy...
 
The damping factor is simply the ratio between the resistance of the driver and the resistance of the rest of the circuit.

In practice, the resistance of an apogee driver, it being a bass, a midrange or a tweeter is somewhere between 0.1 ohm (the scintilla midrange) to about 3 ohms (diva bass, duetta bass etc)

The resistance of the rest of the circuit is made up of the sum of the amplifier resistance (usually < 0.05 ohm for an ss amp) and the filter resistance, because both of these are in series with the driver.

So the lower the resistance of the filter, the higher the damping factor will be. Simply because the speaker filter has a higher resistance than the amplifier. So the published damping factor of the amplifier is usually quite meaningless.....

It gets even worse: At the cross-over frequency between two drivers, for instance the bass and midrange, the filter resistance is equal to the resistance of the separate drivers, so here your damping factor is equal to 1.0

This alone is a good reason to go active bi-amping:)

Nevertheless as you may have seen I have an amp with switchable damping factor and you can just about hear a difference between its low and high settings.

The A21 assertion that the bass sounds somewhat over-controlled or choked due to high DF is just a guess that may well not be true. It is kind of based on the switchable DF amp and the effect thereof i.e. subjective stuff.

I did state earlier that the effect of amp DF on Apogees is very marginal indeed.
 
$12,000 Merrill Hypex NS1200 next to my 211s. I tried it with a Audio Note M8.

700 Watts into 4 Ohms.

Sounded awful.

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Marc - check this thread out: http://theartofsound.net/forum/showthread.php?40108-Recommend-Me-A-Very-High-Power-Amplifier
 
Purite uses those with his Liszts - mola mola actually, similar
 
Keith initially ran his Liszts on 15W/ch Class AB Bakoon SS, and room nodes/bass interaction aside, the sound was vibrant, textured, tonefull and fast
Then he dsp'd the sound with Illusonic and moved to megaWatts Class D MolaMola, and the sound took a massive nosedive
Less nodes issues, but the Molas were truly anaemic and ponderous
Amazing really that replacing 15W with 700W could lead to LESS energy
 
The Merrill is a gutless amp, with no sign of showing its power rating in its sonics. It will play loud, don't get me wrong. It just displays no get up and go. Undynamic in extremis, really.
 
So, are we saying ALL class d is not up to the task of powering Apogees AND showing tone and texture?
The Taiko Kodos class d at the SGM demo on Munich had a lot to commend them
 
I'm basically saying keep a constant flow of amps running past your speakers until you find ones you like. There's no other way.

The Crown is better than the Merrill and is an acceptable listen.
 
Nevertheless as you may have seen I have an amp with switchable damping factor and you can just about hear a difference between its low and high settings.

The A21 assertion that the bass sounds somewhat over-controlled or choked due to high DF is just a guess that may well not be true. It is kind of based on the switchable DF amp and the effect thereof i.e. subjective stuff.

I did state earlier that the effect of amp DF on Apogees is very marginal indeed.

Usually amplifiers change the damping factor modifying the feedback value - sometimes this change also causes changes in general sound quality, distortion and frequency response.

Damping factor relative to 8 ohms resistive load, as usually specified, is just a different way of specifying the output impedance of an amplifier. Audio Research, for example, used to specify the output regulation in dB from 16 ohm load to open circuit. Some calculus was needed to compute the output impedance at 8 ohms ...
 
Justin, other than the physical demands the Apogees, and esp their bass ribbons, put on amps (precluding the vast majority of tubes, if the Apogee Owners Forum Boards are anything to go by), are Apogees reasonably amp agnostic?
By that I mean Class D COULD work as well as Class A? Or is A/AB always likely to be superior as is often the case with other speakers?
These Taiko Kodos Class D Monod were pretty impressive in Munich driving the fussy G1s, the engineer is the guy who perfected the SGM server, and I believe he is seriously talented
And at c£5k per 700W/ch set of monos, £10k gets you your bi amped requirements
 
I'm basically saying keep a constant flow of amps running past your speakers until you find ones you like. There's no other way.

The numbers we get in the net do not indicate such a terrible load - the Divas are said to be 4 ohm and having a 87 dB/W. The ribbons are mainly resistive, nothing that could suggest a very difficult speaker. But I could not find any detailed measurements, showing impedance and phase versus frequency.

At that time the Soundlab's were much worst - capacitive load, with a variation between 40 and 1.5 ohm, less than 84 dB/watt. And I remember that they could be played loud with 250 watt tubes.
 
Another review claims use low resistance speaker cables or you can lose up to 15% of your amp's power. Not seen that one before but might be worthy of some consideration if using tube amps.

When I heard the Big Apogees the owner was using Ocos Speaker cabling

BruceD
 
Micro, the owners of Divas and FRs in the Apogee Forums are in some kind of arms race when it comes to powering their speakers esp the bass ribbons
One guy found push-pull 700W tubes just couldn't make his Divas bass ribbons "jam"
Others were dissatisfied with their 350W Krells, Michael/Thekong reported going to amps on steroids/Pass Labs tri amping equating to nearly 2.5kW!

I know what this is all telling me...
 
Just checked out a stellar, and tbh brilliantly humorously written review, of the Sanders Magtechs on vxm.com (link to review via Sanders website)
Stereo pair took Analysis Omegas in it's stride, and the pair of monos did not break sweat over the MBL101D's, both sets of speakers sounding superlative
At $5.5k stereo amp/$11k monos factory direct, and 30 day no quibble sale or return, may be the best Real World priced megaWatts amp out there
An idea would be the monos in the Divas bass panels and stereo amp on the mids/treble ribbons
 
Fas42, can you summarise what you think makes them special?
Can we assume a Maggie is as difficult, or even more difficult, a challenge to an amp as an Apogee is?
I believe the Magtech is Class AB
 

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