What should I upgrade?


Hi everyone!

I have a Bel Canto s300 (300 watts @ 4ohms) driving my Magnepan 1.6qr's. I'd like to get more defined low end throughout the volume spectrum.

Which choice is best and why?

1. Upgrade to the s500 (500 watts)
2. Add a JL Audio f112? subwoofer to existing setup.
3. Add room acoustic treatments, etc. (walls are wood, floors are cork.) *If choosing this option what is recommended?

PS. I use a Bel Canto Dac3 and stream from Mac ibook G4 via Airport Express using glass Toslink or hardwired via USB.

Devon
"Audiophile in training"
develyn50
Hi Devon,

As we've seen, a case can be made for many different approaches. But here is my take, and I'll qualify it by saying that my experience with Maggies is fairly limited (several listening sessions at a friend's house, to one of the older, larger Maggies driven by Audio Research tube electronics, and integrated fairly successfully with a Sunfire subwoofer).

Your 8 to 12 foot listening distance leaves me much less inclined to recommend higher amplifier power than I was initially (based initially on the size of the room and the relative inefficiency of the speakers). And consider too that the upgrade you were initially asking about, from 300W to 500W, is only an increase of a little over 2db. I think that the clincher (in terms of not upgrading the amplifier power, at least for now) would be if you are satisfied with the volume you can achieve in the mid-range frequencies.

I think that a significant contributor to the bass shortcomings you are sensing is likely to be the 3 to 5 foot distance to the wall behind the speakers. That will result in a partial cancellation of bass frequencies centered in the area of roughly 70Hz. (The approximate formula is 86Hz divided by the distance to the wall in meters, and the effect is known as "1/4 wave cancellation"). That occurs because the reflection of the sounds at and around that frequency, that are radiated towards that wall by the speakers, will re-arrive at the speakers approximately 180 degrees out of phase (i.e., inverted) with respect to the original wavelaunch, and will therefore subtract from the original wavelaunch at and around that frequency.

Fixing problems in the deep bass region via room treatments is problematical at best, because the long wavelength of those frequencies makes them difficult to absorb. Moving the speakers further from that wall, if possible, would certainly help though, by lowering the frequencies which would be affected. So I would suggest trying that first, if it is practical to do so. Doubling the distance would get most of the affected frequencies below the speaker's 3db bandwidth point, which I feel pretty certain would produce a significant improvement.

If it is not practical to do so, or if doing so does not result in adequate improvement, considering that you undoubtedly have significant attenuation centered around 70Hz due to room effects, and considering that the speakers themselves are specified to be down as much as 3db at 40Hz, my strong instinct would be to add a subwoofer (or two). I would consider things like optimizing cable selection to fall within the realm of fine tuning the system, but I think that the issues I've mentioned are more fundamental and need to be dealt with first.

Regards,
-- Al
Al,

thank you for the detailed follow-up. I'll give your suggestions a try.

PS. Thank you to everyone else who contributed.
I have one more question.

What about bi-amping? Could I use the s300 for one speaker and purchase an additional s300 for the other speaker? Would this setup provide any significant benefits?
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Hey Al,

Wow, that's great stuff, I really enjoyed your post!

I forgot about the Dipole Effect.

Hi Devon,

Keep im mind that if you move your speakers out into the room more, than you may have to move your listening position backwards if that's possible. I don't believe side walls will effect dipoles that much because there is a null effect at the sides of the speakers.

I believe you said you have a short ceiling that slopes upward, so be aware that the further you get away from the front wall, your ceiling height will change also. Since these are tall speakers, ceilling reflections can also have an effect. I found another formula for magnepan speakers, regarding ceiling height.

I'm not sure if this formula takes into account your sloping ceiling, however it may help other people that have Magnepans. This is for a rectangular room.

0.618 x ceiling height in feet = The distance from the speaker to the front wall in feet.

This refernce formula is from George Cardas at Cardas Audio.

However, the "1/4 wave effect" will probably have a larger effect, since most of the sound is projected forward and backwards.

At least Al, gave you a really good starting point, and obviously you must go by your ears.

Good Luck,
Rich