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Magnepan 20.7 and Subs

I've been reading about supplementing my Magnepan 20.7s with a sub, the general preference being REL.  However in room I'm getting fairly deep bass with the 20.7's, so my sense is that I would put the crossover on the REL pretty low, probably at 30Hz, leaving only sub 30Hz material porting "also" to the sub to augment the natural deep bass of the Magnepans.  I'm just wondering since there's precious little info in the 15hz to 25hz range, do I really need a PAIR of RELs, or could I get by with just one?  And shouldn't that one be capable of going REALLY low, like the G1, or what's the point?  Any advice would be appreciated.  Thanks.
pwhinson
bdp24's avatar
bdp24
9,417 posts
 

Oh yeah? Well I own Tympani T-IVa’s ;-) . And have heard the 30.7, though in a bad sounding demo in a really poor room. Wendell Diller was not pleased. But to get back to the point of yours that I am contesting, it is your statement that below 150Hz Maggies are point source radiators. That is simply not true; they are absolutely dipoles at all frequencies, including below 150Hz. Q: What magically transforms Maggies into behaving as point source radiators at 150Hz and below? A: Nothing. Your post directly above seems to find you subtly backing off your earlier statement to that effect.

The matter of their interaction with the wall behind them is a completely different subject. By the way, @don_c55 uses four Rythmik F12 subs with his Magneplanar MGIII’s, and has chosen to employ absorption on the wall behind the panels, rather than diffusion.

don_c55
1,025 posts
 
@bdp24

I do not use any subs with my MG IIIa speakers.

The MG IIIas are in my home theater and MG 3.6s are in my main room.

They are both flat to 30Hz and I do not feel the need for lower bass.

I am more than satisfied.

Bass below 30 Hz has little musical info. Low bass peaks and dips are hard to deal with in my rooms.

I also like to keep peace with my neighbors below in my condo.

I rarely playback much over 90 dB except when neighbors are gone.
bdp24's avatar
bdp24
9,417 posts
 
OMG @don_c55, I've been conflating you with a regular on the Rythmik Forum. So sorry!
don_c55
1,025 posts
 
@bdp24

You are right that I am an EE and have owned and listened to 6 foot Magnepan’s every day since the 70’s.

I do show up on several forums under different screen names.

But never use subs or even modified Magnepan’s.

I like them natural and not abused!

I replace the fuses with brass tubes and steel jumpers with 12 gauge ofc wire although.

I also use Cardas golden cross “classic” speaker cables.
mcreyn
293 posts
 
My two cents about subs and Maggies.  I have had 5 pairs of maggies, currently 3.5s with Mye stands which were rebuilt by Magnepan last year.  I have always used my Maggies with various velodynes and now Rythmik.  I have run them full range with the subs rolling off in the high 30hz range, and crossed over.  

In my experience, Maggies work best high passed with the subwoofer picking up the bottom two octaves (20-80hz).  They are more open and it helps eliminate the large bass resonance that Maggies have in the 40-50hz range, depending on the model.  The key I found was a good a crossover, otherwise the Maggies just sound veiled.  In my case, an NHT active crossover (X2), that is fully balanced provided the necessary transparency to work well.  The First Watt crossover is supposed be excellent, but is single ended only and about $1500.   
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