Highest SQ Crown amp for Bass

[Brandon B]

Input from all welcome, but curious about JonM/ThomasW's opinion on this.

Still working on my speakers sloooooooooowly, but I have accumulated an amp collection. My question is: I have a Crown macrotech 2402 to drive my L & R woofers (Stryke Lmabda SB10's in a sealed 3ft box, XOed with a Marchand XM9 at 250Hz with accuton/focal 2 ways)). Amp is about 900 wpc at the 4ohms of the drivers. Plenty of headroom. Or is it foot room for a woofer?

But it has a fan. This is not a huge issue as I have modified my room to have an innsulated AV equipment closet with forced air ventilation and a sealed door. But when listening to 2 channel music only, it would be nice not to have any noise. So I was wondering what the concensus was as to the sound quality of a Crown K1 compared to this amp, as I could sell it and get a new K1 pretty easily. I have seen some people saying the K series are crown's best, but that is not supported by the price. However, that price may reflect the extreme road durability and flexibility built into the MA series.

K1 does have superior damping (3000 vs. about 1400 in the passband of my woofer).

Or does someone have a better suggestion for about $1k, 700wpc into 4 ohms?

BB

[JonMarsh]

Hi Brandon,

I like the K series Crown Amps; Gerald Stanley's implementation of CLASS D with the opposed current half bridge is very innovative in the way it eliminates stress on the output devices from body diode conduction or overlap shoot through, while effectively doubling the output ripple frequency for a given power switch frequency. Furthermore, it is possible to interleave converter blocks and further reduce HF distortion without raising the actual switching frequency. (I work for a company that makes transistors suited for the K series amps, and have met with Gerald a few times)(I even own one of his first designs, the Crown IMA distortion analyzer).

The Macro reference series is Crown's take on a very high performance conventional amp. Building this way requires more output devices, larger heatsinks, etc. For a given output power, it is more expensive to build. Also, the power supply is probably a little better optimized in the Macro series. (i.e., beefier).

For LF duties, either amp will probably work well. I'm not really a big fan of pro "road" amps for bass systems in HiFi, because most don't have the power supply capacitance to really stabilize the rails under high current demands- in most cases, amps like QSC's, Mackies, etc., are built more to a price as much as a level of performance. Yes, they can have "slam" of sorts at high levels, but it's like comparing my old Phase 700 in the 70's with a modified Dyna Stereo 400 I built- the latter had 100,000uF of capacitance (4X the Phase Linear) and 100 uF of polypropylene bypass; (plus extra output devices and tweaked driver stage); it would shame our big Luxman and Stax Class A amps the Sound Gallery was selling. Power supply rail pumping on bass transients can create a more "dynamic" sound, in that things sound like they're working harder, but it doesn't create "ease". A really good system played loud should be deceptive; it shouldn't sound loud. Many of the "cues" we use for subjective volume are distortions of one kind or another.

Also, damping factors in amplifiers are a lot of specsmanship. Reall world application is another matter. Damping factor is ratio of load impedance to the output impedance of an amplifier at the terminals. It doesn't include speaker wire. Even with my homemade Kimber cables, 14 ft, equivalent to 9 AWG wire, about 35 milliohms, will "limit" the actual damping factor (at the speaker) to about 225. If you "only" use 12AWG wire, you'll be lucky to hit 100. But most speakers are designed with an amplifier source impedance of 0.1 ohm or so in mind anyway, and changing this by 50 milliohms or so one way or the other won't make a meaningful difference.

So, your Macro Reference amp should be fine. And it won't have the output HF ripple noise that the K2 will have. That could be a problem in some systems, re noise pickup. While I've always been fascinated with Class D amps, and built and wrote a few papers on them, I've never used one in my home audio system.

Bottom line, I can't see any benefit to your exchanging your Marcro Reference for a K2. I think the K series are a pretty cool Class D implementation, but I don't think I'd use one for a full range amp, and I can't see it offering you any advantages over your Macro Reference. If you needed another amp to drive a low efficiency sub like the Aerial Stryke 15, then maybe a K2 could be in your future.

Best regards,

Jon




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