Passive sub for Magnepan 3.6r?


Intrigued by the fanatical praise for the Magnepan line, my buddies and I finally got the chance to audition same at length. The 1.6s were fairly engaging, though a bit bright to my ears, and wholly lacking in low end slam--overall there's a number of conventional dynamic speakers I'd choose for the same $$. The 3.6rs, however, truly are as awesome as their cult proclaims--they reproduce drums and vocals as well as anything I've heard and are incredibly transparent. We did an A/B comparison of the Maggies to comparably or higher-prices B&W Nautilus and Thiel floorstanders, and it was absolutely no contest--next to the Maggies, the others sounded veiled and boomy.
All that said, and with due respect to those that enjoy the 3.6rs w/o a sub, we all felt that the 3.6rs lacked bottom end impact and were, in effect, 80% of a great speaker. We then added a REL sub (as is often recommended), but still struggled with the integration--no matter how we adjusted the sub, the combo still sounded like two separate speakers, not an integrated whole.
So my question is, assuming I take the plunge, would the Maggies be better served by pairing with a passive sub? My concept, as yet untested, is that by using the same amp to power both the sub and the Maggies, I might get a less distorted, more seamless sound. While I'm sure this topic has been addressed somewhere, your informed opinions would be most appreciated.
loomisjohnson
The discrepancy you heard between what the Maggies are doing in the bass region, and what the subs is doing, is primarily an acoustic room-interaction issue.

A single monopole subwoofer will produce a peak-and-dip pattern at the listening position, and these peaks and dips will be far enough apart that they will be audible even if you don't consciously identify them. Now you can move the sub or move the listening position and that will shift and re-arrange the peak-and-dip pattern, but will not eliminate it. You can equalize it and improve the smoothness over a small listening area, but that will likely make it worse elsewhere because the inherent peak-and-dip pattern will be very different in other locations, so instead of cutting peaks and boosting dips you'll be boosting peaks and cutting dips.

Instead, suppose we have two monopole subs, preferably places fairly far apart, and non-symmetrically. Each will produce a unique peak-and-dip pattern at the listening position. The sum of these two dissimilar peak-and-dip patterns will be smoother than either one alone, and because of the time it takes for the ear to register low frequency waveforms the two will be heard as one even if the path lengths to the listening position are somewhat different.

Now the output of a dipole is smoother than that of a monopole because a single dipole can be thought of as two monopoles with one of them displaced 180 degrees in phase rather than physically displaced in space.

My suggestion for achieving similar in-room bass smoothness to a pair of dipoles is to use four small monopole subs, scattered asymmetrically around the room. The result is significantly smoother bass not only in the sweet spot, but throughout the room. This will have in-room smoothness comparable to the bass you get from the dipoles, but with the ability to pressurize the room ("slam") that dipoles inherently don't have. Credit to Earl Geddes for the asymmetrical multisub concept.

Duke
dealer/manufacturer
I wonder what amp you are using Loomis?

Throw a ton of current at the Maggies and then listen to the bass.

Also pull them out from the back wall about 7ft (no kidding) the bass integrate with the midrange so much better.
first of all welcome to the Maggie fan club.

If the 1.6's didn't compare to other speakers in their price range, I would like to know what amps where used? I have never heard any speaker under $2k that can touch the 1.6qr's, but you need a lot of power, such as Innersound (sorry now SandersSound) Bel Canto's or high current Parasound's.

Same for the 3.6r's which I have had forever. They have a tremendous amount of slam, if you have the right amps (and as above correctly mentions, the right room set up). I have learned after many different amps that that you need to start with a low of 600w (into 4ohms) and go up from there. I find about 1000w to be right.

I do have a sub again now (Rel B1) and it really does fill in the bottom well, but after much time and effort to place it correctly and dial in the crossover, I have it set at 39 to just take over the very low notes, and the SLAM is well, SLAMMIN.

Good luck, if you get them concentrate on the amp(s) first them think of a sub. I would start with:

Cary CAD 500 MB (my favorites)

Parasound JC-1's

Bryston 14b SST (or 7b sst's, same thing)

Sanders Sound ESL amps (all great, or the older Innersound)

there are more, but get crazy expensive, and I haven't tried many of those with the exceptions of the high powered Pass amps, which are great.
Duke,

At 30,000 feet, I'd agree with every word you said. However...

IME, dipole bass doesn't look just like 2 monopoles. True, the deep suckouts are dramatically reduced as they would be with a pair of monopole bass generators, but smaller suckouts occur more frequently with dipoles. It's a different (maybe more benign) problem, but a problem, noetheless.

As to EQ, your point re: "the sweet spot" is probably more relevant in theory than in practice. If EQ'd on-axis response is good, you needn't sit with your head in a vice. For most high end listening rooms, my guess is that EQ is extremely effective. It's certainly been the case for me.

OTOH, if a given system is in the "party" room, there may be more teeth in your argument.

Marty

Marty
thanks for the feedback. i auditioned the maggies in optimal conditions--acoustically treated room, speakers seemingly well placed at least five feet from the wall, driven by a big old boulder amp (certainly more than 500w + @4ohms)-- so i don't think the set up or associated gear was the issue. we also crossed over the REL at 40 (consistent with what macdadtexas does), but all of us still heard the disconnect. i'm sure audiokinesis's analysis of the room interaction is correct--he seems very knowledgeable--but i still wonder whether using one amp (rather than an amp to drive the maggies and the sub's amp)might be a more cost-effective solution; hence my initial question about using a passive sub.