[Aether Audio]

Guys,

Check this out:

Whaddaya think?  If anybody can think of another speaker that has a BETTER chance of giving him decent sound *OTHER* than a pair of Revelations, I think we all should chime in and share that info.  I figure you guys are a better source of info than me, as I would inevitably come off sounding like a salesman.

Personally, I don't think I've ever seen a case where a guy needs a speaker that offers some form of directivity control more than Springboks. Other than the Revs, about the only other recommendation I can think of would be a pair of JBL or Electrovoice "PA" speakers.  There are quite a few PA models that offer some type of horn that will provide good directivity control.  Of course... they would sound like PA speakers, but in his case that would probably sound a lot better than those little Kharmas or most any other typical high-end speaker - in your room.

Springbok... First of all you need either a taller speaker or some kind of pretty tall stand for a smaller speaker.  In your case, the Revs would be about perfect.  Even then though, if the speaker you choose doesn't offer some serious directivity control, you're not likely to get what I would call truly "high-end" performance.  Again, the Revs to the rescue.  In fact, I have never seen a room that cries out for them or something very similar more than your room.  But... that's just my opinion so don't take my word for it.  Let's see what the rest of the guys have to say.

So... what about it guys?  Am I off my nut or does this guy need a pair of Revs? aa

-Bob

PS... At this point I wouldn't even worry about the amp choice.  You have a much bigger problem to contend with.   Oh... and please don't take offense.  I'm just trying to point out the severity of the problem you're facing.  In the end, most of us have some form of limitation or another that we have to deal with.  I've seen worse situations too.  Many years ago a friend of mine's father had a MacIntosh rig driving a big pair of Electrovoice home speakers and they were firing right into the side of his bed!!! 

[Geardaddy]

Holy crap Springbok.  You were not kidding about your room.  I think the fundamental issue here is not the speaker or the amps.... ...but I agree with Bob....the Revs would do very nicely...

[mcullinan]

The first problem is your room is leaning to the right badly. Have that looked at...

Im of the opinion that everyone needs a pair of Revs ....
You could also use a very strong vacuum to suck up some unneeded furniture.
Mike
Mr. Not so helpful in reality guy.
 aa

[Springbok10]

Bob, Very gracious of you to publish the photo. I'm glad you see my problem. I have 40 year old vintage Allison 3s in the corners - sound good,too, filkl the room better than Kharmas. Tell me how the Revs will survive and sound good - I'm all ears!! I sent you pictures of the Allisons in those corners......

[Double Ugly]

Tell me how the Revs will survive and sound good - I'm all ears!!

I think Bob pretty much covered it, and based on my experience with 'em, I agree.

The combination of controlled dispersion and elevated drivers is tailor made for your listening room.  I don't think I've ever seen or heard of a room more ideal for the Revelations.

Seriously.  Considering their world-class performance and ability to mitigate some of significant challenges your room presents, you'll think you've died and gone to audio heaven.

[Duke]

I think Bob is right in that a tallish, controlled-pattern speaker would work well in that room.

Note that Roy Allison's designs are MUCH closer to a controlled-pattern speaker than most direct-radiator designs are.  He pays a lot more attention to getting the "power response" (summed omnidirectional response) right than most designers do.  Since that particular model is designed for corner placement, in effect you have the walls of the room acting as a big, low-tech waveguide.  So in my opinion if the Allisons are working well, that's an indication right there that the design philosophy and execution embraced by SP Tech is likely to also work well.

I can understand Springbok10's attachment to his Atma-Sphere amps; they really are something special in my highly biased opinion.  Perhaps there might yet be some way to bring amplifiers and speakers together for a blind date?? 

Duke

[Springbok10]

Duke, I understand what you say - it seems that whatever, short of non-existent, modern Allison-equivalents with better crossovers and drivers, will be a compromise, given the placement. Since the speakers will not be far enough out in the room, clearly soundstaging will be affected and we come back to the impedance - not ideal, albeit easier than the M-Ds, to drive. But I would feel more confident if they were 8 ohm speakers. The bitter pill is that it is a very expensive compromise and as you all rightly say, I wont know until I try it. It would also be helpful if there were a pair instantly available, which will eliminate my 8 weeks of "what ifs" - so you wanna whip me up a pair this weekend, Bob?

[ted_b]

Being that this is in the SP TEch forum I won't comment on other speakers' capabilities, but simply to say:
The SP TEch Revelations are perfectly suited here due to their dispersion AND their height.....let alone their sound.   

[Springbok10]

Even though it's the SP Tech forum, it's perfectly appropriate to compare them with other speakers, Ted_b, especially if it is enlightening! Go ahead!

[Springbok10]

By the way, you all mention height - line arrays have height, too. In fact 7 ft is not unusual. What would be their down-sode in my setting, compared with the Revs?

[ted_b]

Just my opinion, but I think if this is going to naturally morph from :  "how would Revs do in this room?"  to "what speakers would work in this room" then the Audio Circle or something other than the SP Tech forum would be the legit place for it.  My $.02

[Springbok10]

Ted_b, thsi is the evolution of the saga:
1. I approached Bob about Revs
2. I told him I had a terrible room
3. He said that the Revs are, other than PA spaekers, the only way to go
4. If somebody disagrees, and gives reasons, it is not necessary to mention another brand of speaker, but it would not be inappropriate in this context to do so
5. In the spirit of honest debate, I am not sure what your objection is; if I had decided not to buy the Revs and was just touting for free advice about my room, that would be different. Currently the Revs are my number one choice, but I am sure, looking at my room, you can tell why I am cautious in proceeding without hearing any, including, dissenting opinions. Bob's character is such, that, even if a SP Tech devotee would disagree with him, I doubt that Bob would hold it against him!

[ted_b]

I have no objection; it isn't my forum.     Just mentioning rules just in case.  Carry on.

[zybar]

Just my opinion, but I think if this is going to naturally morph from :  "how would Revs do in this room?"  to "what speakers would work in this room" then the Audio Circle or something other than the SP Tech forum would be the legit place for it.  My $.02

Agreed.

Bob is a great guy and I know he wouldn't get upset over discussing other speaker choices in his Circle, I can't say that all the people who frequent this Circle would act in the same manner as Bob.

If you want to truly get a larger and more varied viewpoint, bring it over to Audio Central.

George

[Duke]

One advantage that the Revelations would have over a line arrray is less sidewall interaction.  You could aim the Revelations (toe them in) so that they'd have very little early reflection energy off of the sidewalls, if you wanted to.   

A second advantage is the Revelations would have a smoother power response.  Their net output is more consistent up and down the spectrum compared with a line array.  The result is more natural timbre throughout the room.

A third advantage is the high frequencies from the Revelation would be firing over your furniture, whereas most of the tweeters in your line array would be firing into the furniture.  This will soak up the high frequency energy from those tweeters before it has a chance to reach you, but longer wavelengths will be less effected by the furniture.  The result will be a skewed (dulled) tonal balance.

I have experimented with line arrays and with waveguide speakers that are conceptually similar to Bob's speakers, and in my experience the waveguide approach is more adaptable to less-than-ideal room conditions. 

Duke

[Aether Audio]

Springbok10,

I don’t want to come across as trying to “sell” you on our speakers.  This is a difficult fence to straddle though.  What I will do is explain the physics involved in simplest terms and what our Revelations can accomplish in your situation.  Other than that, there’s not much more that I can say.  I’m not about to try and convince you or make you “feel good” about purchasing SP Tech product as I believe that to be unethical.  First and foremost I’m an engineer – not a salesman.  Besides, once a customer understands the principles involved, our products tend to sell themselves.

To begin, I have the greatest respect for Roy Allison.  He was one of the pioneers that helped identify the issue and importance of room power response.  Much of his philosophy has been a guiding principle behind our product design.  In that, he developed speakers with the consideration of how speaker placement affected the final sound – hence, his corner placement concept.  The physics behind his designs are as valid today as they were then.

The idea is that as you place a sound source (speaker) within the “pressure zone” (a function of wavelength) of a nearby boundary, that boundary effectively “disappears.”  This means that the path length difference between the direct sound emanating from the driver and that reflected from the boundary is so short that no phase cancellations occur at any point distant from the source.  Essentially, this means that there appears to be no reflection or “echo” whatsoever, even though the sound is reflecting off of the nearby boundary.  The principles involved “pressure zone” theory are a bit involved, so I’ll only provide a cursory overview.

Besides the “apparent” elimination of reflection effects, what also happens is that the effective sound pressure doubles.  This will cause a 6dB increase in SPL with respect to the sound pressure that would be measured if there were no nearby boundary.  Now… not to confuse you, but that also means the total acoustic power radiated appears to double – an increase of 3dB.  This is not really the case though – no new energy is being created.  What is actually happening is that the field of radiation that the driver “sees” is being cut in half.  This assumes that the boundary extends infinitely in all directions.  To clarify, a speaker held up high in the air would radiate into a full spherical space – we call this 4pi space.  When the source is placed against an infinite baffle, that space is cut in half or becomes a hemispherical space.  We call this 2pi space.

This process is repeated for a second and then third boundary, which is what we encounter when placing the speaker in a corner.  If the speaker is placed far enough into the corner, then the corner seems to “disappear” and the bass output greatly increases.  This is also why the Klipshorns were designed to be placed in a corner and also why we designed our “Infra-Wave” subwoofer for corner placement.  Essentially, by doing so one gets what appears to be a lot of “free energy” or extra bass output for no added electrical power input.  If the speaker is designed to take advantage of this free “acoustic gain” then the demands on the woofers (and the driving amplifier) can be greatly reduced.  You must remember, a reduction in drive power from the amplifier of only 3dB means that the amp only has to deliver ½ of the power that it otherwise would.  When you consider the acoustic gain provided by corner placement, a 200-watt amp seems more like an 800-watt unit when driving a speaker designed for corner placement.

So…how would the Revelations work in a corner placement scenario?  Well, if the system were left “untreated” you’d end up with enormous amounts of bass output.  Also, the closer you get them into the corner, the SMOOTHER the frequency response would be.  Yes, it would be greatly boosted in output compared to that at mid and higher frequencies, but over the region that is “acoustically amplified” by the corner, the actual frequency response would be smoother than if the speakers were placed out further into the room.  This is one of the great advantages of “pressure zone” placement, beyond that of the extra bass output.  In fact, this effect is often taken advantage of by recording studios to eliminate early room reflections.  Often studio designers will mount the speakers into the control room wall, such that their front baffle is flush with the wall.

Now, with the Revs you obviously can’t get their front baffle into the corner like the Allisons, so there would be a “transition zone” where the radiated field that the speaker sees changes from approximately 1/2pi space (the corner effect) to 4pi space (a spherical “no wall” condition).  This will cause some “ripple” in the frequency response through the transition region and consequently affect the soundstage and imaging abilities a bit.  FORTUNATELY though, due to the waveguide technology employed in the Revelations, this “ripple” (and any consequential impact on imaging) will be greatly minimized as compared to virtually any other high-end speaker design.

This is for two reasons.  First, the waveguide controls and narrows dispersion from about 1KHz on up to 10KHz such that the horizontal field is limited to about 120 degrees (+/- 60 degrees from the main forward axis).  This is not a trivial advantage.  Second, the waveguide allows us to crossover at 700Hz.  This helps to “slow down” or make the transition a more gradual process as the front baffle limits the radiated field from the tweeter to a 2pi (hemispherical) field down to about 650Hz.  Seeing that the front baffle can be no closer to the wall than 15.75 inches (the depth of the enclosure), this places the waveguide/baffle out into the room a fair distance such that the wave front will have expanded out into the room considerably before reaching the walls and reflecting. 

The upshot is that yes… imaging will be affected slightly, but far less than virtually any other speaker design.  In fact, in the critical upper mid and high frequencies where the ear is most sensitive, the side walls will have essentially no negative impact on the sound field.  Actually, in that respect the Revelations would even be superior to the Allsions.  If you notice, their tweeter and midrange will suffer far more from sidewall effects as they have no form of “wave directing” device.  As they are essentially mounted on a flat baffle, they will exhibit an immediate 2pi (180 degree) radiation pattern.  Since they are not close enough to the side walls to be in the pressure zone over most of their operating frequencies, the sound wave emanating from them WILL reflect off of the sidewalls in such a way as to cause significant frequency response ripple.  Again, this would most likely result in a fairly significant degradation of soundstage and imaging – especially seeing that the effect would occur throughout the highly important upper midrange and high frequency regions.  I can virtually guarantee that over that frequency region, the Revelations would easily outperform the Allisons.

[Aether Audio]

Now we are left with one final “problem” – the extra bass boost resulting from corner placement of the Revs.  HA!  This is a blessing in disguise…especially when it comes to using the Atmo-sphere amps to drive them.  It is a simple matter to build a little passive equalizing network to flatten the frequency response.  This network would be composed of nothing more than a couple of resistors, an adjustable potentiometer (like a volume knob), maybe a switch, and a couple of capacitors.  With the knob and switches you could then fine-tune its effect to optimize the performance of the Revs in your room.  Seeing that it would be totally “passive,” that means it wouldn’t require any external power or batteries.  That also means then that it wouldn’t use any transistors, integrated circuits, or other “active” components that could degrade sound quality.  The whole thing would be nothing more than a little box with connectors for inputs and outputs and would be placed between your preamp and power amp in the signal chain.

Oh… as simple as it may seem, don’t underestimate its effect!  Remember what I wrote above about the effect of reducing the demand on the woofers and power amp?  After this little puppy is inserted and adjusted for best sound, your amp won’t have a care in the world concerning the impedance of the Revs.  At bass frequencies the amp will have to supply very little power to get PLENTY of volume.  A reduction of 6dB in power requirement in the bass means that your amp would only have to supply ¼ the power it otherwise would if the speakers weren’t loaded into the corner.  Conversely, your amp would “seem” to have (at least) 800-watts of output instead of 200 watts in the bass range. With that much headroom, your amp wouldn’t have the slightest problem driving the Revs… or virtually any other 4-Ohm speaker for that matter.

So… the way I see it, considering your amp and your concern for its ability to drive the Revs… your “problem” of corner placement becomes instead the ideal solution!!! -- ESPECIALLY if you were to use the Revelations.  How’s that for an analysis?

Hope this all makes sense.  To be honest, at this point there’s not much more that I can tell you.  Oh…as far as “so you wanna whip me up a pair this weekend, Bob?” goes… believe me, I sure wish I could.  But… it’s an unfortunate fact of life that “perfection” takes a little longer.

While I’m at it, (thanks Duke ) you are correct about the line-source height issue.  That most certainly would help.  The only problem is that they would do nothing to help reduce sidewall reflections and therefore your soundstage and imaging problems would remain.  All of this is summed up in Duke’s posting above.

TedB & Marbles,

No worries my friends.  If there’s another speaker out there than can even EQUAL the Revs in regards to Springbok10’s situation, I’d like to know about it.  I ain’t scared…I’ll be glad to go head-to-head with any other design and compare notes.  I know what we’ve accomplished and I also know what other’s are doing – have known for a long time.  That’s WHY our stuff was designed as it has been.  Considering the long history of audio and the maturity of the market, you don’t push the state-of-the-art like we have unless you really do your research.

-Bob

[ted_b]

Wow, corner-loaded Revelations, smoothed out with a nice passive EQ knob!!  Very kewl indeed.  Hmmmmmmmmm..............

Serious question:  would front wall placement hurt front-back (depth of image) soundstage?

[Springbok10]

That is a pretty awesome, reassuring response, Bob. Only one question: The passive equaliser box will go between the amp and preamp. Ralph's amps and preamps are fully balanced. So I need XLR inputs and outputs. Is this a problem?  Will the circuit be fully balanced? Ralph does not have RCA outputs on the MP-1. I hope TedB and Marbles are reassured, since Marbles made me feel a little guilty of Bob abuse:)

[Aether Audio]

Ted,

Actually, without any wall treatment to the sides of the Revs (when corner loaded) you're likely to suffer a little loss of stage depth.  This is one area that Springbok10 is likely to struggle with.  But... and this wouldn't be too hard to do... IF you were to fill each side of the speaker over to each corresponding sidewall and back into the corner with fiberglass or other damping material, you might just get around the problem.  Of course, then you'd want to cover the damping material with a nice cloth so it looks decent.

But... if you were to do this I think the end result could actually be pretty awesome.  The damping material would pretty much attenuate most of the upper bass/lower midrange energy and thereby eliminate any early reflections in that region.  At that point you'd have more or less the equivalent of a reflection free zone to the sides of the speakers.  That would be virtually identical to what most recording studios try to accomplish.  The longer wavelength bass frequencies wouldn't be attenuated by the damping as they need way more than you could stuff to the sides of the speakers to damp them.  Therefore the bass would just go right on through the damping material and reflect back.  Due to their long wavelengths and the closeness of the corner, they would remain in the "pressure zone" and hence, reflection free (as outlined in my previous posting). 

So... you'd end up with tons of bass gain that would greatly reduce woofer excursion (and hence distortion) as well as greatly reduce the load on the amp.  After everything was equalized back to a flat response - get outa town!  Talk about headroom... y-e-a-h baby! aa I think Mr. Springbok just opened up a whole new world of possibilities!

Springbok10,

You need balanced connections?  Darn!  That's just too bad.  Psych!!!   Heck yeah... piece of cake.  Balanced or unbalanced - no big deal.  Shoot, back in my old pro sound days I used to wire up all kinds of balanced stuff.  In the audiophile community it seems balanced gear is almost some sort complicated and "mysterious" thing.  If I was designing electronics, every piece of gear would have balanced connections.  Why do you think the pros invented it in the first place?  In fact, I'm glad to hear that's what you have.  Any time you make some sort of passive filter you tend to run the risk of extra noise pick-up when going unbalanced.  Going balanced we'll be sure to avoid that little gremlin.

Take care,
-Bob