[reefrus]

Just got back from a great weekend in Las Vegas at T.H.E. Show and CES.  Got to see Bob and Karsten and the Revelation pair being shown.  I don't want to steal Bob's thunder, so I won't reveal too much.  I know Bob is on his way back to Indiana and Karsten is continuing his vacation in the US till the end of the month.  Suffice it to say, from what I heard during the short time I was there, the critics LOVED the speakers.  I'll be very interested to read the reviews. Stay tuned!  

[Aether Audio]

Steve,

Thanks man, glad you could make it.  It was good seeing you.  Too bad we live so far apart.  T.H.E. Show went very well for us.  I suppose at some point we will be making some announcements here on AC with regards to several issues.  Upcoming reviews are amongst those issues but there are other very significant developments in the works as well.  I'd like to be more enthusiastic but I've had the flu from at least Dec. 1st until now and I just don't have the energy.  Besides, I doubt many here at AC would take much note in them anyway.

I'll update everyone when I find the time.

Better yet Steve...give me a call.

-Bob

[ooheadsoo]

Sorry to hear you were feeling under the weather and hope you get better soon.  Bummer to be sick through the holidays.  I'm sure many of us are looking forward to hearing about developments in the works.  I know I am.

[reefrus]

I didn't know you were sick!!     So sorry...I talked to Jason a couple of times and he didn't mention it.  

I will call you tomorrow sometime when I have the chance.

[Aether Audio]

Folks,

Here's a couple of pics of our room taken by PFO.  You'll have to scroll about half way down the page to get to them.

http://www.positive-feedback.com/Issue23/ces06dc6.htm

-Bob

[Russell Dawkins]

In their comments under the image, they mention a review by Victor. Could you shed any light on that?

[Aether Audio]

Russell,

The review David Clark was refering to was the one Victor Chavira wrote and PFO posted here:
http://www.positive-feedback.com/Issue22/sptech.htm

It's posted elswhere here on our circle as well.
Oh, as far as the bass goes and the Timepiece vs. the Revelations, it's only partially a matter of extension.  The TP 2.1" are -3dB @ 29Hz vs. the Continuum 2.5's and Revelation MR-1's which are both -3dB @ 25Hz.  If you need extension below 30Hz then those larger two models are the way to go.

But there's more to it than that.  The Revelations are a special case wherein, due to their transmission-line loading, their rolloff below 25Hz is only 12dB/oct. as opposed to the 24dB/oct. rolloff due to the bass-reflex loading of the other models.

Besides providing significant infrasonic output below 20Hz, the lower slope of the Revelations is essentially the same as that of a sealed box design.  This means that they introduce only 1/2 the amount of group-delay/phase shift at the lowest frequencies that the other models do - or that of any other ported speaker with the same -3dB corner frequency(25Hz).

Many years ago Lorri Fincham (sp?) of KEF fame showed that large amounts of low frequency group-delay/phase shift causes the ear/brain mechanism to interpret such as "more bass."  This is true irrespective of the actual frequency extension.  To the experienced listener, the effect also imparts a certain "overhang" or even "boominess" to the sound.  That's why many audiophiles don't like bass-reflex designs.

The effect can be mitigated to a large degree by simply extending the frequency response/tunning frequency of a bass-reflex design to as low of a frequency as possible.  That's why all of the products in our Millennial Reference Series are tunned to below 35Hz.  If a bass-reflex design is tunned much higher than that, the "boomy" effect really starts rearing its ugly head.

All bass-reflex systems are a compromise to some degree, but those darn laws of physics just won't budge and mandate compromise in the real world.  If you're willing to let size not be a factor, well...then you can get much closer to "perfection."  But in many applications size is an issue and we're left with little more than the good ol' bass-reflex solution.  Our goal has always been to accept that compromise in our smaller models, but then do all we can to minimize the negative consequences.  

Any engineer that has a clue will tell you that good engineering virtually always dictates some compromise.  What separates the "men from the boys" is that good engineers find creative ways to juggle the parameters and use the laws of physics to their benefit in order to produce truly optimized designs.  The rest just stand around scratching their heads and wishing they could change the laws.

Well...that's my $0.02 worth on the subject.  Hope this helps.

-Bob

[Bill Baker]

The rest just stand around scratching their heads and wishing they could change the laws.

 Maybe they need contact our government, they seem to be able to change laws as will. As cocky as they are lately, who knows, maybe they can change the laws of physics

Any engineer that has a clue will tell you that good engineering virtually always dictates some compromise. What separates the "men from the boys" is that good engineers find creative ways to juggle the parameters and use the laws of physics to their benefit in order to produce truly optimized designs.

 Agreed, everything in audio design is a compromise in one way or another but finding only the happy medium is not good enough, as you mention, it is more important to "produce truly optimized designs". Too many will navigate towards the negative side of these compromises and not getting the most potential possible from any given design.

 Truly ground breaking design is not always possible on "the cheap". To quote another Circle member " There's more to a great deal than a good price".

[bhobba]

The Revelations are a special case wherein, due to their transmission-line loading, their rolloff below 25Hz is only 12dB/oct. as opposed to the 24dB/oct. rolloff due to the bass-reflex loading of the other models.

I wonder if Bob can clarify something for me.  I thought the bass of the Timepieces was not strictly ported bass - it was a hybrid - something different.  In the days when I listened to a lot of speakers I generally developed a dislike for the boomy bass of 6.5 ported designs.  All the reviews of your design and what you say on your site tell me the Timepieces are not like that.

Of all the bass loading techniques the one I like the best is a transmission line (of the few I have heard - it is not used much).  I always figured one reason was the 12db roll off matches the 12db room gain.

Thanks
Bill

[Aether Audio]

Bill,

Technically, you are correct - to a degree - regarding the Timepieces (or either of the Continuum models).  The devil is in the details.  Below their tunning frequency they do roll off like a standard bass-reflex design.  It's in the range above port tunning that they differ from a traditional bass-reflex design.

I have to be careful - don't want to give away the farm here.  Let's just say that the internal chambering eliminates a lot of the unwanted resonances at higher frequencies that result as a side effect from traditional reflex tunning.

If you think of the insides of a speaker box as nothing more than a scaled down version of a room, then you can imagine what must be going on with regards to resonant modes and standing waves.  Traditional methods of using large amounts of damping material to squelch those resonant modes work quite well in sealed boxes.  The problem is, if one uses the same amounts inside a bass-reflex design, they over dampen the reflex action and kill the bass output from the port.  If you use less, then you get the bass back but you also get resonant pressure nodes in the box that end up pushing on the woofer cone.  The cone then moves in response to these resonant modes and... out comes a lot of mid-bass and/or midrange crap.  

The fact that these resonances alter the resulting frequency response are bad enough in their own right, but worse, the arrive later in time than the drive signal that excited them.  In the end you have mushy, bloated bass and a time-smeared midrange response.  If you look at the impulse response, it gets stretched out in time and is full of little "squiggles" that sure don't belong there.

The upshot is that there's a lot more wrong with most bass-reflex systems than just the excess group-delay/phase shift I outlined in the previous post.  Our hybrid t-line/reflex systems address the problems I've just outlined here but unfortunately they do nothing to address the total group-delay issue that is the result of reflex tunning.  For that, the only solution is a full transmission-line loading technique such as we employ in our Revelation MR-1 MKII's.

In the end, there's no free lunch.  We've addressed the major problems in reflex design such that we have made them sound as little as possible like the traditional reflex designs most are accustomed to.  Nevertheless, they're not perfect.  That... will cost you a little more.

-Bob

[reefrus]

Ok Folks,

Here is the lastest news about SP Tech from Positive Feedback on line by Greg Weaver about the CES/SHOW.
http://www.positive-feedback.com/Issue24/ces06gw.htm

It was great fun and an honor chating with Steve McCormack, Jim Merod and Greg Weaver in the same room.