Specify power requirements for JBL M2 HF

[Jonas_h]

Hi all,

Quick question for the hive mind. I'm trying to figure out how much amplifier power I need for the HF side of a JBL M2.

The usual approach — take system sensitivity, add distance loss, solve for watts — doesn't really work here. The M2 is actively bi-amped at 800 Hz, so the HF driver and the woofer each get their own amp. The published 92 dB system sensitivity is basically the LF number; the D2430K is way more efficient than that although JBL has added an analog pad.

So: if you were sizing only the HF amp on an M2, and the goal was 105 dB peaks at 5 m (~16.4 ft) at the listening position — what numbers would you actually plug in, and how many watts would you land on?

And then there is the extra dimension that you also expect less energy in 800-20.000hz compared to 80-800hz in music and movies, but that might be a later question how much the peak requirement from 800hz and up should be reduced.

Curious how people here approach it.

Thanks!

 

[Devnull]

Unless you want to redo a bunch of DSP settings just use what JBL recommends. IIRC even the DSP settings for the BLU option expects two identical amps per speaker.

 

[Jonas_h]

I know - still interested in the approach on how to spec amp power in this scenario.

 

[NTK]

Not sure if you are aware of this thread, which has plenty of good information on the M2. The cross-over document by @pos showed a ~9 dB attenuation for the L-pad for the compression tweeter. The M2 is rated at 92 dB/W @ 1 m. You do the math. Also note that the HF portion of the music signals usually have higher crestor, so you may want to budget in a fair amount of headroom.

JBL M2 Clone

I hope you pull this off... I also hope you go the hardwood route or at least veneer the boxes. I positively love this aesthetic! Thanks for the positive vibes! Prolly omit the midranges given what I am learning. If hardwood, it would be oak-ply with solid end-pieces. Appreciated!

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[Devnull]

I have to ask if you're buying or building a set of M2s why would you mess around with specing different amps for high and low frequencies? The cost difference is down in the noise for a project this size

 

[Jonas_h]

I already have three original M2's with a BSS Soundweb and three Crown MacroTech 5000i amplifiers.

I like what I hear, but wanted to hear if the lower distortion on the Purify amps is actually audible.

And a cheap and easy way to test is to try them on the HF part where the distortion on the Crowns would probably be more audible than on the LF (and should be easy to account for different gain in the BSS)