[fletch999]

I have a customer that has a two channel setup that he LOVES. Acoustat electrostatics, 600W monoblcks etc. Listens to mostly vinyl, but wants to expand into digital and multi-channel. He is looking to add a high quality sub that will give him the ultra low bass frequencies at a high SPL without hurting his panels output.


Any recommendations on crossovers, subs and any other pieces needed? And is it worth the time and expense?


Secondly, can these exisitng speakers be used as the basis for a 5.1 channel system for theater? Any recommendations here?


Thanks in advance.

 

[John Kotches]

Fletch,


My first surround setup had Acoustats (Spectra 22s) for Front L+R.


You can definitely use the Acoustats as the base for a surround system. Your biggest challenge will be in finding a center channel that really matches up well with them. Potential options would include Martin Logan CC, Final Technologies, Soundlab CC, Eminent Technology's CC, Magnepans CC and a few others. I would select the Final, ET or Maggie over the ML, as you ideally want a "full range" panel speaker to go with the Acoustats. I use the term "full range" carefully, as I am referring to an all planar configuration.


If your client isn't averse to the used market, he could even pick up some matching Acoustats for surrounds and have quite an amazing system. Alternatively for surrounds, I would look at smaller Finals, Maggies, ML Scripts or their new ATF.


For crossovers I would consider an Outlaw ICBM or using the crossover in the HT preamp/processor/receiver.


For subwoofers, there is no right answer. I found SVS matched well with them, as did an older Von Schweikert Tower of Power sub. Maybe a REL (bigger $$) or Adire (smaller $$) as alternatives depending on the budget.


There's lots more to discuss, this is just a starting point.


Best Regards,

 

[Greg_R]

Look for a dipole sub to match the dipole nature of the mains. The best that I've seen has been Adire's new Parthenon motor (you won't need an enclosure). Get a cabinet maker to build a mount and power the whole thing with a commercial amp (Crown or QSC) and include a quality Parametric EQ (Rane, QSC, etc.). QSC's EQ integrates nicely with most of their amps (plugs directly into the back of the amp). This dipole sub will give you clean reference levels down below 20Hz (very rare with dipoles). I would look at line-level crossovers instead of speaker level crossovers (active biamping sounds better to my ears).

 

[Bigus]

In an ideal world, you would want to match your sub's characteristic to that of the main speakers. In this case, it isn't that they are planar that is so important but rather that they are dipolar. Unfortunately, there are few if any commercially available subs today (Audio Artistry used some in their systems, but I don't think these are available now). A custom builder might be willing to tackle such a challenge, but be forewarned that dipolar subs are quite large for their output capability... which might not matter to someone talking about using planars for a multichannel system.


Barring the dipolar route, which admittedly isn't going to be palatable for many people given the size, cost, and availability constraints, my next suggestion is to attempt to use a sub crossed below the room's fundamental mode, which is often in the 40-60 Hz range. If the Acoustats have acceptable output down to that frequency, a mismatch in radiation patterns from there down won't have detrimental effects on the sound (in fact, some view that as better than a full dipolar system) due to the room changing to pressure mode excitation.


If the Acoustats are not up to the task of providing acceptable bass down to that first mode, then you are left with a wide variety of subs on the market to attempt to match to the dipolar panels. I've personally had better luck with sealed designs when doing just that, but there is no technical reason why a ported design cannot also work well. What I found as the biggest problem is that, due to the power compression of typical panel speakers, the sub became proportionately unbalanced as the volume is raised higher and higher. I'd hate to suggest a power compressed sub to match though.


In the end, your ears (and his ears) will be the best guide if you can't go for the technically preferred solution. However, I will also strongly suggest examining room treatments and sub positioning, as this will play a vital role in how a box sub integrates with dipolar speakers. Due to their radiation pattern, his Acoustats excite room modes far less than conventional speakers. A boxed sub lighting up those modes will make for terrible integration issues. Minimizing modal excitation in the lower frequencies will smooth the transition from one source type to another. Your job will be much easier if you properly address room acoustics, or very carefully place the sub at the least.

 

[Bigus]




Looks like Greg_R and I are on the same wavelength here.

 

[FrantzM]

Greg_R


Have you heard the Adire Parthenon? This thing was displayed at the CES 2--4, it seems like. I have not heard much from it since. On paper it looked like the absolute Mother of all subs, yet not much else except what is available on the Adire web site...


If that hings is really half of what they put on paper, that could be THE sub. Period!

 

[John Kotches]

Greg,


Is Parthenon shipping yet? It certainly is a beast, assuming the specs are accurate.



Frantz,


Most of the Acoustats would have been good down to 60Hz, in all honesty they couldn't keep up with the Parthenon if the specs are accurate.


Cheers,

 

[KeithR]

Why not Martin Logan Descent/Depth Subs?

 

[Anthony A.]

velodyne dd series are killers also. i have a set of ML ascent i's that i will most definately go with the velodyne. the ML descent and depth have three woofers built into one enclosure that might be what you are looking for. then again, they're not dipolar in any way, but the sound will probably match up better than a single front firing sub.

 

[Bigus]

At sub frequencies, there really are only two radiation patterns to choose from - dipolar or omnipolar. If it isn't dipolar, then it will have an omnipolar radiation pattern, regardless of whether the enclosure has one, two, three, or thirty drivers.





But, if my first two suggestions don't pan out, the ML and Velodyne DD subs all look like quality candidates to consider.

 

[Richie Duroseau]

Quote:

Originally posted by Bigus At sub frequencies, there really are only two radiation patterns to choose from - dipolar or omnipolar...

Genesis are dipoles in upper bass, midrange and treeble, and bipoles in the bass...


I apologize beforehand.

 

[Bigus]

Sub frequencies are omnidirectional if produced from a monopolar source, which is any bass transducer in an enclosure. If you add a second, rear firing sub transducer to make a "bipolar" driver layout configuration, you are merely adding two omnipolar radiators together. It matters not which direction they are facing. It is simply a matter of physics.


The only exception, aside from the obvious use of dipolar cancellation, is a waveguide of sufficient length to affect the dispersion of sub bass frequencies - i.e., an architectural sub horn. These are impractical in most anyone's home... while capable dipolar bass systems are inconvenient, architectural sub horns dictate the design of the home.


Thus, while Genesis systems may use a bipolar driver layout for the bass, the dispersion pattern is accurately described as omnipolar.

 

[GoodMudge]

Why do people get so hung up on the radiation pattern of a sub (which is in a reverberant field, even with a dipole) in-room, and ignore the completely different coupling/wave-launch of the drivers in a box sub and an electrostat?


A fair number of people suspect that the perception of driver speed (for which stats are famous) has to do with the way the driver couples to the air.

 

[Bigus]

Dipole subs still cover that possibility, as they are velocity transducers just the same as stats and other panel speakers, instead of the pressure transducers found in enclosed sub designs. This goes hand in hand with the dipolar radiation pattern.

 

[GoodMudge]

Quote:

Originally posted by Bigus Dipole subs still cover that possibility, as they are velocity transducers just the same as stats and other panel speakers, instead of the pressure transducers found in enclosed sub designs. This goes hand in hand with the dipolar radiation pattern.

Got a reference for this?

Aren't sealed box subs normally acceleration-coupled transducers, at least until the room's dimensions are smaller than 1/2 the reproduced wavelength?

 

[Morbius]

Quote:

Originally posted by GoodMudge Why do people get so hung up on the radiation pattern of a sub (which is in a reverberant field, even with a dipole) in-room, and ignore the completely different coupling/wave-launch of the drivers in a box sub and an electrostat?

GoodMudge,


Exactly.


One can show mathematically that if the wavelength is long relative to the dimensions

of the room - and one has reflective boundary conditions [ bass tends to reflect off walls ],

that these reflections will make the soundfield isotropic; irrespective of the anisotropy

of the driver.

 

[Dizzman]

I am not entirely sure what the good doctor just said... But DAMM it was impressive!

 

[Morbius]

Quote:

Originally posted by Dizzman I am not entirely sure what the good doctor just said... But DAMM it was impressive!

Dizzman,


"Isotropy" means "independent of direction"


"Anisotropy" means the opposite - a dipole driver is anisotropic since the phase of

the signal is dependent on direction.


Basically - what I said was that if you have bass reflecting off the walls all over the

place - it tends to randomize - and the bass waves tend to "forget" that they were

emitted by a driver that had a directional dependence.


Hope that helps make things more clear.

 

[Dizzman]

I was reasonably aware of what you said. I was just more enjoying the statement as a whole. My comment was made to imply not as much that i had no idea what you were saying (which i realize i said) but that that was a really impressive sentence. And it indeed is.

 

[GoodMudge]

I'm still wondering how a dipole using a high density driver becomes velocity coupled. AFAIK velocity coupling only happens when the density of the driving diaphragm is similar to that of the air surrounding it. Hence electrostats (and some ribbons) will couple in this manner naturally. Horns (as acoustic impedance transformers) can do the same trick with a conventional heavy diaphragm. I can't think how a dipole would acheive the same effect.