Apogee Scintilla - Information about the Efficiency wanted

[djQUAN]

Originally Posted by tiefbassuebertr

Unfortunately there are no price lists mentioned and in the tests there are also no price informtions.

in one of your links, I saw the amp priced at 52,500 euros. Not sure if that is for a mono set or stereo pair.

[a.wayne]

Originally Posted by tiefbassuebertr

In which respect you perceive the mentioned sound difference by your listening test and which amp model you have in use therefore?

In general it is for me completly clear, that each additional device in the signal pad have an influence regarded the sound. A good known example therefore is a scaly or burnt-off relay contact for DC protect in series to the loudspeaker. Even without relay and with a capacitor in the signal pad you will get an influence to the sonic character (this is my favorite approach to avoid mechanical contacts, despite the present and mostly unwanted high pass character). Basically a directly dc coupled connection between amp out and speaker input saves lowest signal loss (at best with only very short cable connection, directly solder, i. e. without terminal and plug) - this is clear.

One user of Apogee Scintilla uses four power stereo amps in "Mono-Bridged" mode and Bi-Amp mode since a short time.
The model is "SA-Reference" from Plinius Audio - go to
http://www.pliniusaudio.nzld.com/doc...efbrochure.pdf
and
http://www.pliniusaudio.nzld.com/doc...arefmanual.pdf
Output power at 8 ohm load impedance is 1000 watts (and thus theoretically 16000 watts at 0R5 load impedance but the 10 amp fuses prevents this in real live, of course).
The output stages (8 pairs power BjT devices in parallel mode/each amp) runs with a voltage of +/- 86 volts switchable for class A (2200mA, 275mA/each pair) and class AB (320mA, 40mA/each pair).
Sound quality is exceptionell good, the user says, the best amplifiers ever heard.
But I told him, that the reliability is very low and the likelihood that occur very expensive damage is very high, particularly in such cases, when high sound pressure levels are trying to achieve.

This is the reason to start this thread. Concerning the max SPL of this Apogee planar radiators unfortunately I have no comparison to good known loudspeakers with cone transducers (thus the various mentioned SPL values offer no evidence for me and therefore are no helpful). Also there are no information about the maximal input power rating of this model (for the most cone speakers usually published).

There are only two options for good reliability in the case of further use of this amplifier model:
1) the use of four impedance matching transformers
2) power amp modify in such way, that the supply voltage is halved or quartered (+/-43 volts or +/-21,5 volts) and the idle current accordingly doubled or quadrupled. Basically easy (only reducing the resistors for reference current through the CCS), but in real life much more efforts than matching transformers. From this view I would prefer the first possibility.

If the disadvantage by sonic quality (by use of the matching transformer) is only present at low level aera below 150 Hz, it does not matter, because for this frequency range an additional subwoofer will come later (include an additional high pass filter).

Lowering the voltage would be his best option , saves the amp and better sonics at that load. Now how to combat the increases in distortion by the amplifier due to the very low load , more class-a bias ? more feedback ?

[Groove-T]

a.wayne, just for my interest

Did you measure scintillas current and voltage under full power in 1ohm model, if yes, which values did you have and how did you measure?

[a.wayne]

Full power...!

No we tested at our listening avg , the scinnies was that of a friend who had custom build amplifiers , he listens loudly 90-93db avg din , his amps were rated @600 /1ohm the designer told me they would not require more Than that , the fact that he never tripped his 15 amp speaker fuses was a clue ..

On my ribbons I have measured voltage at an avg din of 86db impedance 1 ohm and agree with his assessment . Even when pushed at higher levels I very rarely ever blow the 10 amp speaker fuses and when measured I was using 7V rms into the midrange ribbon (1ohm) at normal listening levels ...

Of course if you want to exceed 100db consistenly then I would suggest double that ,(600) figure and those who do most times damage the bass ribbon ..

Regards ,

[bear]

not very experienced personally with them, but... putting a resistor in series with the bass ribbon will definitely increase the Q and decrease the DF... probably making for a warmer sounding bass?

Also, I was under the impression that amorphous cores were best at HF, and lacked inductance at LF, so were less than optimum for LF applications...

_-_-bear

[Groove-T]

Yes bear, thats why my trafos should work only for mid and high.

No res. in series with woofer, the scintilla has a full and rich bass, some people found it to much and you need a real huge resistor.

a.wayne, i had krell mda 300 driving scinnies, and twice my main fuse in the appartment rated at 50 Amperes at 230 Volt were blown when i gave full power with some mid bass impulse.

BTW, the MR itself is only 0,06- 0,07 Ohms, then there are some wires, connectors and a preresistor (foil type). So if you had real 7 V on the MR, how many amperes ???

On the other hand, since i am a certified apogee woofer installer, after installation of new woofers i do some tests with amps minimum 1200 Watt into 1 ohm and its for woofer test especially.

[a.wayne]

Yes if you drive the Krells to full power with test signals absolutely , you will not come close to doing such when playing music ...

Regards ,

[tiefbassuebertr]

Originally Posted by Groove-T

Yes bear, thats why my trafos should work only for mid and high.

No res. in series with woofer, the scintilla has a full and rich bass, some people found it to much and you need a real huge resistor.

a.wayne, i had krell mda 300 driving scinnies, and twice my main fuse in the appartment rated at 50 Amperes at 230 Volt were blown when i gave full power with some mid bass impulse.

BTW, the MR itself is only 0,06- 0,07 Ohms, then there are some wires, connectors and a preresistor (foil type). So if you had real 7 V on the MR, how many amperes ???

On the other hand, since i am a certified apogee woofer installer, after installation of new woofers i do some tests with amps minimum 1200 Watt into 1 ohm and its for woofer test especially.

After a closer look to the frequency response from second URL by post #1 (from German test magazine "AUDIOPHILE") I am very confused. This is a MK-IV version. What happens here (go to the attachment for higher resolution)?
Actually one need a special additional device for equalization (similar like a RIAA equalization for record players), independend of the fact, whether a impedance matching transformer is in use or not. I doubt, that it is possible with passive components in front of or behind the transformer (perhaps a foil capacitor of 47mF resp. 47.000uF and a low impedance 30 mH inductor is necessary only for remove the low frequency peak by 35 Hz).

[a.wayne]

Add .5ohm resistors and forget about it , the amplifer will handle the load then and no transformer to cloud the sound ...

[Groove-T]

tiefbassuebertrager

There exists no scintilla MK 4.

Like i wrote before, the german thing is a clone and has nothing to do with the real apogee! Actually lawyers are involved to clean up this mess!

The measurings shows a peak at apx 35 Hz, which is part of every apogee woofer, but: The real challenge with apogee is the woofer tuning, which is not done correctly with this clone, for sure! How to do it, is still our certified installer secret.

This peak( if done well) should not be equalised, since this kind of woofer is a dipole, is very depending from placement( distance to rear wall) and not a box and if executed well, the apogees have a kind of bass, which we apogee fans appreciate very much. No boxy sound, but full and rich bass and dipole mid/highs....

The rest of the frequency response is not very scintilla like, since its a clone! Not a real good one IMHO.
The impedance response is not visible here, but originally its demanding the most power in the transit area woofer/MR around 300 Hz and below.

Adding a resistor will change the woofer sound very much due the altered Q and need a lot more amp power just to produce heat. 600 Watt Resistors are a challenge to. Some folks believe resistors do no not change the sound, other ones are convinced they do.
Count me in the second ones.

This impedance thing with the scintilla seems to keep all folks in red alert mode, but it is a problem since more than 25 years and it will not go away. Its stupid to make a clone with the same problems, IMHO!

Thats why Apogee Acoustics in Australia comes with new models, impedance higher than 3 Ohms and efficiency apx. 95dB/ 1 W 1m. Use every amp you like, basta.