Sopra 2 Bass

@james633 and @michaeldunleavy Apologies and please, please bear with me. I revisited testing the 4 and 2ohm taps and need to roll back my findings. First, I wrote 6 and 2 in my last post when I meant 4 and 2, ugh. Second, while the "volume" does seem to drop a tad, it may not be loudness that is dropping, but what I'm hearing may be a smoothing of the track. I am now finding I like 4ohm better than 8. I spent an hour listening to the first minute of Fade to Black on each tap...over and over. 8ohm seems a bit louder, but also a bit harsher... and I do think the bass response is better dipping below 8. Again, I am stunned and have learned I need to run these tests a bit longer than a quick listen / judgment. 4ohm now seems more true, if this statement makes sense, and easier on my ears. Wanted this test out to you asap and I will continue to play with it / give it more time. I love progress. 

A local dealer puts his speakers on the long wall with them nearly 1/2 way to the listening seat well away from the sidewalls and gets prodigious bass from any speaker, including focal’s. It goes against the idea that getting the rear facing port reflective wall support to increase bass, but they’re on to something because the can get that elusive ‘room lock’ bass from bookshelves without subs. If I can’t replicate their results in my room then once I’m done decorating I’m going to hire them for a day.

How much would you spend on a component to get the showroom sound you bought your speakers for? Hire some who knows what they’re doing(not me) to help you.

@steve59 I had a friend ask me about trying them on one of the long walls as well, almost the same time you posted. Doing so was not an option when I started this this post but is now that the room will only serve the purpose of listening. The problem is that the width is only 11'. Need seating for 4 people on the other side, but maybe it will sound good off center? Definitely going to try it once the room is cleared and I'm hearing this system with a fully carpeted (berber) floor that's been hidden for a long time.

@james633 Another update - After a few more hours swapping taps (almost wrote "playing taps", but some might have taken that literally). I am now liking the 8ohm better at low volumes (~25% or lower) and 4ohm above that. The 8 sounds more dynamic at lower volumes, but too dynamic / harsh at higher volumes ONLY when compared to 4ohm. The 4 is so smooth at higher volumes. I could live with the 4 full time and may try the 2ohm when I want to push things further.

This chase is fun. Thanks again to everyone! I am humbled by the number of you who have taken time to post. 

Response from Bluesound:

MQA has two different “levels” (they call it unfolds) HALF UNFOLD (Software only - 24/96), and FULL UNFOLD (Software and Hardware - 24/192)

MQA requires communication (ie two way) with the DAC for FULL UNFOLD

If it (MQA) doesn’t know what the DAC is you can only get HALF UNFOLD (software only)

Via digital (Optical or COAX) there is no two way communication so you can only get HALF UNFOLD as the BluOS software will unfold the first half, but doesn’t know what DAC is connected

You can turn off the BluOS (software) unfold via the app for zero unfolding, and pass the raw data to the DAC -  This the best option if you have an MQA certified DAC, this will let the DAC do all the work, otherwise you’ll only get the first half

If you do not have an MQA DAC, you should use the Analogue outputs…. at least for MQA, but since the  NODE outputs both digital and analogue at the same time you can use a non-MQA DAC for everything except MQA content (if you want and the DAC is good enough to keep it in the system)

SO…

Analogue out = FULL MQA

Digital Out

Non MQA DAC = HALF MQA via digital

MQA DAC = FULL MQA (if you turn of the BluOS first unfold)

Izjjzi,

Interesting information on the different taps. Looking at the impedance graph of the Sopra 2 it looks like the 4ohm tap would be the right one. You want to match the lowest point of the impedance to the tap and the Sopra dips to 3.7-ish around 100hz. 
Going to the 2ohm tap will probably not change the tonal balance (because it is lower than the speakers so it will not add gain to higher impedance sections of the speaker) but it will reduce your power. I would guess by about 1/3rd. This is because you already have enough current and the 2ohm tap will reduce the voltage.  

But really the amp is powerful and runs cool so using the”wrong” tap will not hurt anything if it sounds good to you. 

If you look at stereophile’s measurements of the MC462 (link below) you can get some in-site as to why you want to match the lowest impedance. It will reduce the distortion and still maintain the full 300 watt output. For most speakers the 4ohm tap is the right one. 
“Figs. 6–9 indicate that distortion is extremely low, lying below the noise floor at powers below 30W or so. I therefore plotted how the THD+N changed with frequency from the 8 ohm output at a level of 28.3V, equivalent to 100W into 8 ohms and 200W into 4 ohms, where I could be sure I was looking at distortion rather than noise. The result (fig.10) reveals that the THD into 8 ohms (blue and red traces) and 4 ohms (cyan, magenta) rises above 1kHz, but still remains below 0.007%. I haven't shown the THD+N trace into 2 ohms from this output, because it was >2% in the midrange and treble and >3% in the bass at 28.3V, which is equivalent to 400W into 2 ohms. The moral: Match the MC462's nominal output to the lowest impedance magnitude of the loudspeaker used.”

https://www.stereophile.com/content/mcintosh-laboratory-mc462-power-amplifier-measurements


As for the the popping sound it could have been a driver bottoming out if it was super loud with deep bass. It probably will not break a well designed driver but it will be uneasy for sure. 

 If it was power related the Mac’s power guard lights would have come on (lights up orange like startup) and cuts the power.