[Duke]

The Planetarium Gamma satellites have one characteristic that presents a problem:  The center of gravity is quite far forward, and off to one side a bit.  This is because of where the woofer's magnet ends up.  As a result, conventional rectangular-top stands don't work very well; when the speaker's center of gravity is placed back over the middle of the stand, part of the rectangle top of the stand forms a large "lip" that is unattractive and potentially a sonic detriment. 

I debated re-designing the cabinet to be deeper, thus moving the center of gravity backwards somewhat and hopefully allowing use with conventional stands.  This would increase the internal volume too much though; I do not want these satellites to go down very deep, because I want the benefits of a good multi-sub system over as much of the spectrum as is feasible. 

Or, I could add several pounds of ballast to the rear of the enclosure, but that just seemed too inefficient and cumbersome. 

Finally I decided the solution was a dedicated stand.  So I recently built a couple of stands with irregular pentagonal tops, to match the shape of the Gammas:



The holes you see on the top line up with feet on the bottom of the Gamma, so that instead of just being perched atop the stand it's on there pretty solid.  The feet are a little bit taller than the holes are deep, so from most angles the speaker appears to hover slightly above the stand.  The edgewide vertical board of the stand runs underneath the Gamma's center of gravity, which as you can see is off to one side a bit. 

Here's how the combination looks:



With stands, the Gammas are $2900 plus shipping (in other words, the stands add $300 over the regular price).  So just a little bit more than the Rhythm Prisms.  In most applications the latter are the better deal because they are fullrange speakers, unless you want the benefit of a good multisub system, in which case the Gammas make more sense.   Right now the Gammas plus sealed Swarm constitute my living room system.

Duke

[jimlevitt]

Duke, could you provide some details on the Planetarium Gamma? Is this the speaker you recommend for use with any of your Swarm systems, or with Jim Romeyn's DSA system? What sort of amplification do they call for?

How do you handle the crossover from the Gamma (or other mains) to the Swarm? Do you run the Gamma full-range, while limiting the upper range of the Swarm system? Where do you prefer to do the cross?

Why are you using the sealed version of the Swarm with the Gamma's in your living room, as opposed to the vented Swarm?

Is the Gamma/Swarm combination likely to be easier to integrate into a room than a full-range speaker like the Rhythm Prism? Is there any reason to lean toward one or the other?

I've had nuthin' but trouble with speakers in my room, even with dipole bass. The Swarm or DSA is probably my next step.

thanks,

Jim

[Duke]

Duke, could you provide some details on the Planetarium Gamma?

Hi Jim, yes I would be glad to.   

Is this the speaker you recommend for use with any of your Swarm systems, or with Jim Romeyn's DSA system?

I would say the Planetarium Gammas are by far the highest bang-for-the-buck mains I offer for use with a Swarm.  The more expensive Alphas and Betas offer some advantages, but at very significantly higher cost.  Jim Romeyn manufactures his own main speakers, which are unorthodox and fantastic.  "Oh but they're weird and they're wonderful", as Elton John might say.     

What sort of amplification do they call for? 

Because of their smaller box and therefore higher system Q, the Gammas are less suited for low damping factor amplifiers than most of my other speakers.  I would want to consider low damping factor amps on a case-by-case basis.  For example, the Atma-Sphere M-60 would be a bit on the warmish side even if we lengthened the port a bit, but the S-30 would probably result in over-emphasis of the upper bass region regardless of tuning.  Beyond that, their impedance is quite smooth above the bass impedance peaks, and their efficiency is relatively high at 93 dB.  In a small room a 5-watt amp would probably work well, and in a big room you could drive 'em with several hundred watts.

How do you handle the crossover from the Gamma (or other mains) to the Swarm? Do you run the Gamma full-range, while limiting the upper range of the Swarm system? Where do you prefer to do the cross?

I normally run the Gammas full range; that woofer is very unlikely to bottom out.  The frequency control on the Swarm's amp is normally at about 11:00, but I'm not sure what the exact frequency is.  Probably ballpark 80 Hz.  My intention was for the Swarm to handle the bottom two octaves, which it can do better than the Gammas.

Why are you using the sealed version of the Swarm with the Gamma's in your living room, as opposed to the vented Swarm?

Well at the time I wrote that, the sealed Swarm was all I had on hand!  For the next week or so I'll have the Super Swarm, which will then be shipped to its new owner.  The sealed Swarm is still a good match, just doesn't go as deep without calling on the parametric EQ. 

Is the Gamma/Swarm combination likely to be easier to integrate into a room than a full-range speaker like the Rhythm Prism? Is there any reason to lean toward one or the other?

Yes, the added flexibility and room-friendliness of the multisub Swarm will work better in the bass region in most rooms than the Rhythm Prism approach.  On the other hand, the Rhythm Prisms are more compatible with low-damping-factor tube amps.  Not that the low end of the Rhythm Prisms sucks, but what four tight little subs can do is on another level.

I've had nuthin' but trouble with speakers in my room, even with dipole bass. The Swarm or DSA is probably my next step.

What kind of trouble? 

Thanks,

Duke

[jimlevitt]

What kind of trouble?

Over the past ten years I've had two of the larger active ATC models in the room (50 and 100). Both needed to be out from the wall four feet or so to let the midrange and treble open up, but the bass was best when the speakers were closer to the wall. Out in the room, bass got very uneven. Worse, in my preferred setup on the short wall, certain bass frequencies just went MIA. There's a deep bass note, repeated on every chorus, on a favorite Lyle Lovett track (She's Already Made Up Her Mind) that illustrated the trouble perfectly. On the short wall setup, it felt as if the bass notes were having a fistfight in the middle of the room somehow, and getting canceled out in the process. The was sort of a fuzzy vibration in the air, but no real note.

 I had similar problems with the Linkwitz Orions, which in my room also sounded (and measured) very shelved down from the upper midrange on up. I never could get involving sound out of those speakers, which knocked me out whenever I heard them in other rooms. Drums in particular never sounded close to right; the ATC's had done better.

Speakers I've had before this past decade included Meadowlarks (the Kestrel did pretty well) and many other box speakers that all exhibited bass boom and uneven room response. I sometimes think my living room is where speakers come to die...

The room is 14'3" x 21', with an 8' ceiling. There's a front door entrance, and two hallway entrances, plus a direct-vent gas fireplace on the short wall. I think I could place four subs against the walls in this room according to your and Jim's suggested plan. I'm not into tube amps - the closest I get is a hybrid Van Alstine preamp - so no worries about impedance matching, etc.

I photograph a lot of jazz performance. I'm looking for a system that gives a reasonable facsimile of the "jump" one hears from real instruments in small to medium spaces, along with honest timbre. This is my living room, so I'd prefer to avoid a bunch of acoustic treatments if possible. The main speakers can be three to four feet away from all walls if need be. The less they have to be located out into the room, the better.

Any chance you'll be up in Seattle again anytime soon?

[Duke]

Thanks for the information, Jim.

I think my Gamma/Swarm system would have a better chance of working in your room than what you've tried thus far, and if there's a reasonable chance of making a sale, I'm up for a road trip to Seattle. 

Let's move to e-mail if you don't mind; audiokinesis at yahoo dot com.

Duke