[Danny Richie]

http://www.axiomaudio.com/archives/may2009.html

Read this from Alan Lofft.  It's about comb flltering.

I have read that before. It is completely false and misleading. This part that was so funny that it has been my favorite part of the whole thing:

"The research shows that comb filtering is not detrimental to accurate loudspeaker sound reproduction; at worst, it’s irrelevant, at best it actually adds a pleasurable element of spaciousness to stereo and surround sound."

 

[Danny Richie]

FYI, what he posted under the heading What Is Comb Filtering? is correct and the measurements accurately show what is going on. However at the bottom of that section he asks:

These are pronounced cancellations, yet when we play music or speech over a pair of M2 speakers, we don’t hear these comb filtering effects. Why is that?

And from there on he does not understand what is happening.

[S Clark]

Interesting response from Brent of Axiom audio reguarding duel tweeders on the VP 150 center.
If duel tweeders cancel them selfs out than duel woofers should do the same. My point here is that duel tweeders are just fine.
 
Robert, you have astutely noted that dual woofers would do exactly the same thing and they do, unless the x-over point is below the frequency where the distance between the two woofers can create a comb.  So any 2-way design loudspeaker that has the tweeter between the woofers or mids (like the quite popular Dapolito design) exhibits comb filtering in the midrange.  And of course, any listening done outside of mono is full of comb filtering because a "pair" of speakers creates comb filter cancellation across pretty much the entire frequency band.

I see that you own a pair of Axiom, and they look like a typical TMM setup. I see no issue with them. But those centers... Sorry, but it is fairly basic that you don't split multiple tweeters.  If you look at the hundreds/thousands of center speaker speakers, you will see an overwhelming lack of designs like this Axiom.  It is for a reason. One of the first thing you tell a physics class when building projects is don't try to re-invent the wheel.  Find what other successful designs have done, and go from there.  I suspect that in the urge to look different, Axiom made a marketing decision that trumped their engineers.
Phase issues are one of those that separate the good from the amateur. These are destined have phase problems.

Regardless, back to the main post.  The Carnegies are on sale, and appear to be a well received speaker at a reasonable cost. 

[saisunil]

"Carnegie Acoustics represents that rare tenth maker: a company that makes a speaker that sounds so beautiful you wonder why everyone doesn’t own a pair. If you want deep, natural bass, silky highs, a natural midrange, detail enough to satisfy pickers of the tiniest nits, and a soundstage so natural that a photo of this speaker should appear beside the dictionary definition of the word, the CST-1 is the speaker for you. "

wow - what a review!

[SlushPuppy]

I don't guess one could ask for a better review.

A nicely done review of the CST-1's by Colin Smith of Sound Stage.

http://www.soundstagehifi.com/index.php?option=com_content&view=article&id=337

Wow, that's a great review! Congrats!

[Nick V]

I checked out the website and am curious about the speakers shown in this ad:





Is this another design that you put together for Carnegie?

If so, are there any specs on this? I would be very interested to hear some info... price??

[Danny Richie]

Is this another design that you put together for Carnegie?

If so, are there any specs on this? I would be very interested to hear some info... price??

Yes, that is the CST-2's. Two pairs were made. Higher quality crossover parts were used as well. They were to be the flagship of that product line and be part of the next production run of product.

However, that model was put on hold due to the struggling US retail market. Some of the high end audio stores that make up their dealer base are not moving a lot of product right now. And when I say not moving a lot of product I mean that they are not moving a lot of any product from any company right now.

[HAL]

The CST-2's were in the Carnegie Acoustics room at Axpona in Atlanta this year.  The setup sounded really good!

If Ron listed where the CST-2 and other speakers are located on AC, that might give some opportunities of where people could audition the setups.   

Just a thought.

[freerider]

Looks like an LS center channel sitting upright.

[Danny Richie]

Still really good deals to be had on these right now...

[pureiso]

I have read that before. It is completely false and misleading. This part that was so funny that it has been my favorite part of the whole thing:

"The research shows that comb filtering is not detrimental to accurate loudspeaker sound reproduction; at worst, it’s irrelevant, at best it actually adds a pleasurable element of spaciousness to stereo and surround sound."

 

I have a question for you along these lines as well.  After looking at the many center channels you have designed, I notice that you have not tried placing the tweeter above the midranges (or single midrange) to reduce comb filtering due to the horizontal placement.  Is this just for simplicity sake (easy to make box), or just something you have not tried before?

http://www.audioholics.com/education/loudspeaker-basics/center-channel-designs

Just what I am basing my assumptions on.  I also know you are much more focused on 2 channel setups, but this seems to be a way to get an even better sound with the center designs.

[JohnR]

it's probably worth pointing out that there is more than one cause of "comb filtering." Danny appears to use it to refer to the lobing/interference from multiple drivers in their anechoic response. In the referenced article, it refers to the observable effect from moving a microphone with respect to a pair of loudspeakers. In Toole's book, a good chunk of a chapter is devoted to the effect as caused by room reflections (Chapter 9).

The distinguishing element of the last is that the reflections occur with a significant delay - many multiples of a wavelength.

[Danny Richie]

I have a question for you along these lines as well.  After looking at the many center channels you have designed, I notice that you have not tried placing the tweeter above the midranges (or single midrange) to reduce comb filtering due to the horizontal placement.  Is this just for simplicity sake (easy to make box), or just something you have not tried before?

http://www.audioholics.com/education/loudspeaker-basics/center-channel-designs

Just what I am basing my assumptions on.  I also know you are much more focused on 2 channel setups, but this seems to be a way to get an even better sound with the center designs.

Been there done that. I even offer my A/V-1 as a fully shielded single unit to be used as a center channel. http://gr-research.com/av-1c.aspx

And yes, it does have a wider and more even horizontal dispersion in that configuration.

I have also found that a design with close center to center spacing, like I get with my small woofers and overlapping the frames onto the tweeter, minimizes the horizontal comb filtering effects and gives good coverage out to about 20 degrees off axis. Not too many people watch movies sitting that far off axis.

Plus, in most applications where the rooms are completely untreated this minimizes the side wall reflections in a range that is typically fairly bright in most rooms. So it is often not a bad thing.

The side laying MTM design also fits the look that most people prefer. Yes, people go for the look.

The biggest problem I see with a tweeter over a mid and a woofer on each side is a huge increase in surface reflections around the tweeter. This can cause a lot of problems as well. So it trades one set of problems for another.

[pureiso]

Been there done that. I even offer my A/V-1 as a fully shielded single unit to be used as a center channel. http://gr-research.com/av-1c.aspx

And yes, it does have a wider and more even horizontal dispersion in that configuration.

I have also found that a design with close center to center spacing, like I get with my small woofers and overlapping the frames onto the tweeter, minimizes the horizontal comb filtering effects and gives good coverage out to about 20 degrees off axis. Not too many people watch movies sitting that far off axis.

Plus, in most applications where the rooms are completely untreated this minimizes the side wall reflections in a range that is typically fairly bright in most rooms. So it is often not a bad thing.

The side laying MTM design also fits the look that most people prefer. Yes, people go for the look.

The biggest problem I see with a tweeter over a mid and a woofer on each side is a huge increase in surface reflections around the tweeter. This can cause a lot of problems as well. So it trades one set of problems for another.

Ok, I thought the surface reflections was the one issue you were going to bring up.  Also, I think you would only gain an inch by moving the tweeter up to the top.

Just was something I was wondering, thanks for answering.

[Danny Richie]

Ok, I thought the surface reflections was the one issue you were going to bring up.  Also, I think you would only gain an inch by moving the tweeter up to the top.

Just was something I was wondering, thanks for answering.

If you took something like this:



With the tweeter half off the cabinet (minimum surface reflections), and then moved the two woofers in so that they nearly touched each other (minimum comb filtering effects), and moved the port to the rear or to each end of the box then you'd have the best of all combos.

[pureiso]

And that would not be the easiest thing for a DIY person to do with MDF...

But that is exactly what I had in mind.

[Danny Richie]

And that would not be the easiest thing for a DIY person to do with MDF...

And that is the only reason I have not offered a kit like that.

[pureiso]

And that is the only reason I have not offered a kit like that.

And what you would gain is just a few more degree of accurate off axis response correct?  Yeah, not really worth it now that I think about it.

[skeeter99]

If you took something like this:



With the tweeter half off the cabinet (minimum surface reflections), and then moved the two woofers in so that they nearly touched each other (minimum comb filtering effects), and moved the port to the rear or to each end of the box then you'd have the best of all combos.

If we're talking about looks, I love the look of the Usher center. Stunning. They build amazing looking cabinets. I've heard the guy who does a lot of their crossovers state side is quite a wiz too ... 

Scott

[wshuff]

Danny, how well would that Carnegie center with the Neo3 match up with an LS6?