Chip amp for low efficiency speakers?

[Odzi]

I'm looking to build out four channels (can be two stereo) to drive a pair of Apogee Stages. They're not the most efficient at 86dB. They also can't be played real loud and have a max voltage of 40v.

What are my best options?

TIA

 

[Mark Tillotson]

Impedance? Is that 40V peak, peak-to-peak or rms?

 

[Odzi]

3 ohms. Not sure about the 40v. I just remember reading the manual and it stated something about 40v. I’ll see if I can find it.

 

[EdGr]

3 ohms is too low for chip amps. I suspect that Apogees rates efficiency like Magnepan - 86dB/2.83 volts which means the real number is 4dB lower.

They will need an EF3 with parallel output transistors and high current/low voltage rails.
Ed

 

[Odzi]

It’s probably 40v RMS.

I’ll look into that amp design.

 

[Odzi]

Are there any recommended kits?

 

[Odzi]

Actually, I’ll start this thread on the solid state forum.

Thanks all for answering!

 

[stv]

3 ohms is too low for chip amps.

It should be possible to use (several) paralleled amps. See tda7293 datasheet eventually neurochrome modulus 286 with reduced supply voltage.

 

[Odzi]

You know. It’s 3 ohm driving both the tweeter and woofer/mid-range. I might get lucky with both being 6 ohm each. Then I could use a chip amp.

 

[adason]

If both are 6 ohm, assuming correct crossover applied, resulting speaker is 6 ohm. Not 3!

 

[EdGr]

You know. It’s 3 ohm driving both the tweeter and woofer/mid-range. I might get lucky with both being 6 ohm each. Then I could use a chip amp.

That is not how crossovers work. The speaker is 3 ohms. The current goes to the woofer below 400Hz and the tweeter above 400Hz. See https://www.stereophile.com/content/apogee-stage-mini-grand-loudspeakers-1990-measurements

Two chip amps could be run in parallel to drive 3 ohms, but you also need high power. IMO, these requirements are best met with a fairly hefty discrete transistor amplifier.
Ed

 

[wchang]

How about Class D like TPA3221 bridged?

 

[Odzi]

So, max voltage is 20v per the current people who maintain the Apogee manuals. I don’t think this is could for chip amps.