Dipole vs. Controlled/Constant directivy - AVS Forum
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post #1 of 27 Old 08-16-2013, 11:47 AM - Thread Starter
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I have always found this topic to be interesting and I have read some past threads here on AVS comparing the Linkwitz Orion to Earl Geddes speakers.

However, I wanted to open up a discussion that focused on the theory of both and discuss their merits.

If you look at measurements of many dipole designs it is clear to me that they do have some for of controlled directivity regardless of what peoples view are of the speaker having a rear wave firing against a back wall.

Something that I find interesting when comparing the controlled speakers like the econowaves/Geddes designs is that Floyd Toole, Dr. Geddes, etc. do state that having room reflections contributes to enhancing the sense of space in a recording. We just need to try and control how much of it is there.

I dont recall the guys name but the guest on HTG: Science of the Room from Professional Home Cinema was stating the same thing. That reflections due enhance sound but you cant have too many of those reflections.

This makes me very curious about that rear wave on the dipoles as does illuminating that rear wall really cause anything truely detrimental? Or does it just simply contribute to this sense of space that many of us want?

Please note: I have never heard either of these designs but i have been reading a lot about the two different approaches. Both of which I find very interesting.

going to to this website:

http://gainphile.blogspot.com/

the home page shows an econowave compared to a dipole of his own design. The dipole certainly looks very good but the question that I raise is how low does it matter to go with such even dispersion?

Dr. Geddes argues that there is not much need below 500hz if memory serves correctly....

Some argue that dipoles "smear" the soundstage with that rear sound wave coming back from the rear wall and therefore there is less focus. At the same time I have read that it sounds very focused on some material and others it doesnt. Which may mean that it is simply very sensitive to how the room is treated and how far into the room the speaker is placed....

I know that horns are something that are very popular here on AVS and I really understand why. I have a very High interest in them as well, particularly those of the Unity/Synergy design.

But I am also very interested in many of the dipole designs out there.

What are your guys' opinions? Anyone have experience with both? What were your impressions coming away from it? Did you listen to it for just music or also Home theater applications?

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post #2 of 27 Old 08-16-2013, 12:09 PM - Thread Starter
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P.s. I would like to point out this thread that is talking specifically about using multiple subs versus dipole subs.

http://www.diyaudio.com/forums/multi-way/145876-measured-monopole-dipole-room-responses-3.html

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post #3 of 27 Old 08-16-2013, 12:29 PM
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Planer speakers tend to be dipoles and somewhat directive as they approach a line source as frequency goes up. Some conventional designs include a rear-firing driver or two to emulate the "space". Personally I have found it easy to hear (and measure) the frequency aberrations caused by reflections from the back wall and so normally suppress it.

edit: Oops, now read the sub comment, never mind, sorry...

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post #4 of 27 Old 08-16-2013, 12:43 PM - Thread Starter
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Quote:
Originally Posted by DonH50 View Post

Planer speakers tend to be dipoles and somewhat directive as they approach a line source as frequency goes up. Some conventional designs include a rear-firing driver or two to emulate the "space". Personally I have found it easy to hear (and measure) the frequency aberrations caused by reflections from the back wall and so normally suppress it.

edit: Oops, now read the sub comment, never mind, sorry...

I am not interested in just the use dipoles in subs but the entire frequencie spectrum.

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post #5 of 27 Old 08-20-2013, 11:36 AM - Thread Starter
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I guess no one wants to touch this topic with a 10 foot pole...haha.

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post #6 of 27 Old 08-20-2013, 12:45 PM
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Originally Posted by Kimeran View Post


If you look at measurements of many dipole designs it is clear to me that they do have some for of controlled directivity regardless of what peoples view are of the speaker having a rear wave firing against a back wall.

...

Dr. Geddes argues that there is not much need below 500hz if memory serves correctly....

Some argue that dipoles "smear" the soundstage with that rear sound wave coming back from the rear wall and therefore there is less focus. At the same time I have read that it sounds very focused on some material and others it doesnt. Which may mean that it is simply very sensitive to how the room is treated and how far into the room the speaker is placed....

I know that horns are something that are very popular here on AVS and I really understand why. I have a very High interest in them as well, particularly those of the Unity/Synergy design.

But I am also very interested in many of the dipole designs out there.

What are your guys' opinions? Anyone have experience with both? What were your impressions coming away from it? Did you listen to it for just music or also Home theater applications?

One question. When audiophiles add room treatments, do they add reflectors that add reflections to the room or absorbers?

The answer is of course that when audiophiles add room treatments, they either add broken up reflectors that break up reflections not add them over an above what the bare wall does, or they add absorbers.

The general rule is that rooms have too many solid reflections that are too strong. So why would someone who is serious about sound quality want a speaker that adds solid reflections?

That''s why dipole speakers are such a minority thing. And FWIW I was involved in a blind listening test that compared dipole speakers with unipole controlled directivity speakers and to say the least, the listening panel found nothing special about the dipoles.

http://www.scribd.com/doc/103681479/SLReport10-05
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post #7 of 27 Old 08-20-2013, 02:46 PM - Thread Starter
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Darn, my job's internet blocks that link.

As I have stated before in threads that you were in Arny, I am not the most experienced person in audio compared to many on these forums. However, I enjoy reading different theories and applications.

The dipoles to me are very limited designs and I dont like how most of the designs I see require active crossovers because this adds up quickly in electrical and equipment costs.

That said, I think that with some sound dampening behinde the speakers it could possibly lower the reflected sound enough to have very little impact on the sound quality.

Like I said earlier, many have said that the sound reflections in the room contribute to the "they are here" effect.

What was the environment like where you listened to them in the blind testing?

Were they Linkwitz designs or those of a DIY attempt?

I am playing a bit of a devils advocate here as I will fully admit that my biggest interest is in horns as they are more capable in areas that I find important such as dynamics and efficiency. However, I am also very curious of what losing the box sound is like.

I also know that no matter how much I talk about it I will have to hear both designs myself, hopefully side by side.

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post #8 of 27 Old 08-20-2013, 02:56 PM
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Perhaps they just are not the correct Dipoles for the challenge....wink.gif

How about this......dipoles with a 12" co-ax for above 150hz.
The back of the Coax compression driver is open to make it a true dipole.

Question......Does that make it a dipole with a waveguide?
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post #9 of 27 Old 08-20-2013, 03:32 PM - Thread Starter
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Quote:
Originally Posted by Perry R View Post

Perhaps they just are not the correct Dipoles for the challenge....wink.gif

How about this......dipoles with a 12" co-ax for above 150hz.
The back of the Coax compression driver is open to make it a true dipole.

Question......Does that make it a dipole with a waveguide?

Never though about a coax but I wonder how well it would work. I say that because drivers have to move more in a dipole arrangement for the same amount of output compared to a sealed/ported box.

In a box a coax used to too low a frequency can supposedly make those high frequencies muddy....I wonder if this effect would be more extreme in a dipole where the drivers would be working harder.

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post #10 of 27 Old 08-20-2013, 04:19 PM
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It works, extremely well, if designed competently.

I've been using this type of set up, with 2 different Co-ax for over 4 yrs.
No active x-overs, high sensitivity- 97db

For low end, 2 x12" Rythmik servo subs in open "H" baffle.
driven effortlessly with SS Rythmik PEQ amplifiers.
Flat to 20hz ?? thats what advertised, if its not its close.

In a properly treated room, these are hard to beat at almost any price point.

Smarter man than me designed these.
Dont know how many were made, but in my
Canadian province alone there are 5 pairs. That should
give an indication, I would guess at least a couple hundred pairs.
I've yet to see a pair for sale.
They've been discontinued due to co-ax availability.
Google: GR Research Super V by Danny Richie.

My build: http://www.avsforum.com/t/1446691/diy-super-v
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post #11 of 27 Old 08-21-2013, 06:29 AM
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Quote:
Originally Posted by Kimeran View Post

Darn, my job's internet blocks that link.

As I have stated before in threads that you were in Arny, I am not the most experienced person in audio compared to many on these forums. However, I enjoy reading different theories and applications.

The dipoles to me are very limited designs and I dont like how most of the designs I see require active crossovers because this adds up quickly in electrical and equipment costs.

That said, I think that with some sound dampening behind the speakers it could possibly lower the reflected sound enough to have very little impact on the sound quality.

Like I said earlier, many have said that the sound reflections in the room contribute to the "they are here" effect.

What was the environment like where you listened to them in the blind testing?

A listening room that was designed by a well-known audio expert - a person who is in the same league as Linkwitz and is also an AES Fellow.
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Were they Linkwitz designs or those of a DIY attempt?

The Linkwitz speakers were shipped in by Linkwitz himself as a system. He provided the speakers, the amps, the crossovers, the whole enchelada. There was also a DIY effort ithat was part of the evaluation, but the speakers were evaluated independently.
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I am playing a bit of a devils advocate here as I will fully admit that my biggest interest is in horns as they are more capable in areas that I find important such as dynamics and efficiency. However, I am also very curious of what losing the box sound is like.

The dominant source of coloration in the listening room is usually the listening room. I know what boxy sound is, and what most people call box sound with good modern speakers is actually room sound.

I don't think that people can reliably pick out well-designed waveguide speakers (e.g. Geddes) by their sound in a blind test.
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post #12 of 27 Old 08-21-2013, 06:34 AM
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Quote:
Originally Posted by Perry R View Post

Perhaps they just are not the correct Dipoles for the challenge....wink.gif

How about this......dipoles with a 12" co-ax for above 150hz.
The back of the Coax compression driver is open to make it a true dipole.

The waveguide speaker would have to have two waveguides, one pointing front and one pointing back, to be a true dipole. The compression driver would have to be specially made.

This might be attempted in a lab environment, but its so self-contradictory and overly expensive that it is unlikely to ever be a serious mainstream effort.

It all begs the question, why invest a lot of time and money in making a back wave that is going to be absorbed or degraded by the room?
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post #13 of 27 Old 08-21-2013, 08:38 AM - Thread Starter
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Arny,

Isnt it the rear sound wave that makes a dipole sound as "big" as so many claim it to sound? I have also heard it described as "smeared" with no "focus" in the sound stage.

By Contrast, I have read that some econowave designs sound overly focused and like you are listening more to headphones than to a speaker filling a room with sound. Note, after I read this I read how Geddes recommends a heavy toe-in so that you have some reflection from the side walls. I am assuming this pretty much eliminates this issue as from what I understand the reflections is what really creates the sense of space....you just only want the reflections at a certain point in your room and pretty much no where else.

I would really like to experience this boxy sound. I always assumed it was mainly due to the box coloration from not being braced/dampened enough which is why I think it would be very interesting to hear something like a Magico S5 next to a speaker of similar driver arrangement built of more conventional methods.

When you say "Pick out" a well designed waveguide speaker, do you mean that they cannot locate it's location in the room just be sound alone?

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post #14 of 27 Old 08-21-2013, 09:03 AM
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Quote:
Originally Posted by Kimeran View Post


Isnt it the rear sound wave that makes a dipole sound as "big" as so many claim it to sound? I have also heard it described as "smeared" with no "focus" in the sound stage.

I've heard a number of dipoles, both planar dipoles like Magnepans, and also direct radiators like Linkwitz'. I don't know what "big" means, probably because it means different things to different people. I think that the comments about smearing and lack of focus relate to room reflections.
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By Contrast, I have read that some econowave designs sound overly focused and like you are listening more to headphones than to a speaker filling a room with sound.

I do a lot of listening with headphones and I hear the most detail that way. I don't consider speaker/room combinations that come close to that to be a problem. Not even live concerts in a venue with good acoustics has a "room filling sound".
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Note, after I read this I read how Geddes recommends a heavy toe-in so that you have some reflection from the side walls. I am assuming this pretty much eliminates this issue as from what I understand the reflections is what really creates the sense of space....you just only want the reflections at a certain point in your room and pretty much no where else.

Frankly, I think you should listen more and read less. ;-)
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I would really like to experience this boxy sound. I always assumed it was mainly due to the box coloration from not being braced/dampened enough which is why I think it would be very interesting to hear something like a Magico S5 next to a speaker of similar driver arrangement built of more conventional methods.

If this picture is not a complete lie:

http://magico.net/Technology/Enclosures/Enclosures_03.php



There won't be a heck of a lot to hear. They seem to be claiming that their product is less resonant than MDF, and MDF is fairly low on the resonance scale.
Quote:
When you say "Pick out" a well designed waveguide speaker, do you mean that they cannot locate it's location in the room just be sound alone?

I'm saying that they probably won't be able to pick the speaker out by a characteristic coloration that afflicts only wavegude speakers. Many people think they can or could, but this is yet another example of how controlling bias changes the outcome of the evaluation into other than what is expected.
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post #15 of 27 Old 08-21-2013, 10:49 AM - Thread Starter
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That graph that you got from Magico's webiste is the reason I would like to hear them next to a conventional speaker made out of MDF. It is a pretty steep claim.

And I 100% agree with you. I do need to listen to more speakers to make better judgements. However, there are very few speaker stores here in my home town and the only audio shows that I know about are atleast 3 hours drive away.

I have contemplated driving to a big city one day in the future to just go have a listening day for fun. But that is something that still wont happen for a while.

I do have some pretty good headphones though. AKG 240 Mk II but no headphone amp....I will be converting my Bottlehead quickie to work as a headphone amp in the not too distant future though.

Loving audio but having no money is an issue at times haha!

Edit: Oh well, I'm young and have a lot of time ahead of me.

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post #16 of 27 Old 08-21-2013, 01:29 PM
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Babbling: Dipoles are primarily associated with planer speakers such as Apogee (ribbon), Magnepans (planer dynamic/ribbon), and electrostatics (Martin Logan, Soundlabs, Sanders). These tend to be physically large and so project a large sound field as well as provide a visually large image. There have been some dipoles using conventional drivers with rear-mounted speakers; I have heard some but do not recall the brands. I think a lot of their sound signature relates to their physical size, perhaps even more so than the rear wave. Frankly, and I love my Maggies, I have always found the rear wave a pain and usually damp the wall behind so I don't have to deal with it. As far as other reflections, IME/"as has been told to me" these large dipoles act like line sources over most of their frequency range and thus there are fewer reflections to contend with from the sides, top (ceiling), and bottom (floor). When you dial them in, they project a stable image with fewer comb filter effects than conventional speakers -- depending on the room and its treatment! I agree with Arny that the room dictates the sound for the vast majority of listeners. I suspect most of the "largeness" is just from their physical size and large radiating area compared to conventional speakers.

Historically planer speakers have had much lower distortion, within their dynamic range, and better pulse response than conventional designs. It was true 30 years ago, but I am not sure that is true today; I have seen very impressive test results from some speakers out there today.

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post #17 of 27 Old 08-21-2013, 01:30 PM
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Quote:
Originally Posted by arnyk View Post

The waveguide speaker would have to have two waveguides, one pointing front and one pointing back, to be a true dipole. The compression driver would have to be specially made.

This might be attempted in a lab environment, but its so self-contradictory and overly expensive that it is unlikely to ever be a serious mainstream effort.

It all begs the question, why invest a lot of time and money in making a back wave that is going to be absorbed or degraded by the room?

So, lets not call it a wave guide then, just a co-ax dipole
.
The compression driver wouldnt have to be specially made, just milled out, to open the back.
There are open baffle co-ax designs like this.

Have you ever listened to a dipole with diffusion, say a large QRD, on the front wall behind?
Have you listen to many?, or do you dismiss them due to one experience? Just curious.

The Orions are not what I consider "bang for the buck".....there are much better
for a fraction of the price that came with amplification supplied for the bottom end.
You dont need to supply 8 amps. You just supply a single competent amp....I use a inexpensive AVR now.....to handle the 97db top end.

Like most that buy pre designed speaker systems, I let someone else spend time and money on the development.

I know these are not for everyone, but there is not a one size fits all for any loudspeaker.
Its the only subjective item in the chain....correct?
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post #18 of 27 Old 08-21-2013, 03:27 PM
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Quote:
Originally Posted by DonH50 View Post

As far as other reflections, IME/"as has been told to me" these large dipoles act like line sources over most of their frequency range and thus there are fewer reflections to contend with from the sides, top (ceiling), and bottom (floor).
Yup, dipoles have a null along the sides (where the front and back waves cancel).

Sanjay
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post #19 of 27 Old 08-28-2013, 09:08 PM - Thread Starter
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I have been doing some more reading on different speaker designs this week at work as I have not had much to do.

As it turns out, Vandersteen's factory is only about 1.5 hours away from where I live. I have never heard any of their speakers but I am very curious about them as they are built to be time and phase aligned.

How do you guys think a design like the Vandersteens with minimum baffle compare to something like a waveguide/dipole?

I ask because a waveguide could be argued to be a type of baffle and the dipole can be considered something similar to the minimum baffle but allowing the cancelation of the sound on the sides of the speaker....

It's obvious to me that the biggest different would be that the Vandersteen would most likely require much more room treatments due to the directivity of the other two designs.

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post #20 of 27 Old 08-29-2013, 05:51 AM
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Quote:
Originally Posted by Perry R View Post

[
.
The compression driver wouldn't have to be specially made, just milled out, to open the back.

In conventional language, that would be an example of "specially made" It also isn't that easy. To build a symmetrical compression driver you would have to use a flat diaphragm, and you would need two phasing plugs. Most compression drivers have a curved diaphragm and a phasing plug between the diaphragm and the exit to the driver.

Perhaps a picture of a conventional compression driver will help:


Quote:
There are open baffle co-ax designs like this.

Name or web page, please?
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Have you ever listened to a dipole with diffusion, say a large QRD, on the front wall behind?

I think so,.
Quote:
Have you listen to many?, or do you dismiss them due to one experience? Just curious.

I've been an audiophile for over 55 years and have been in 100s of homes, audio shops and more than a few audio shows. I feel like I've heard just about everything several times.

I used to own Ohm F's which are nominally omnidirectional, so I'm very familiar with speakers that shoot sound out their backsides.


Quote:
The Orions are not what I consider "bang for the buck".....there are much better
for a fraction of the price that came with amplification supplied for the bottom end.

Real world examples, please.
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You don't need to supply 8 amps. You just supply a single competent amp....I use a inexpensive AVR now.....to handle the 97db top end.

Like most that buy pre designed speaker systems, I let someone else spend time and money on the development.

I know these are not for everyone, but there is not a one size fits all for any loudspeaker.
Its the only subjective item in the chain....correct?

Science doesn't matter?
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post #21 of 27 Old 08-29-2013, 08:42 AM - Thread Starter
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I think he means that science matters but he does not personally care to understand it, research it, and design speakers around it. He would much rather allow someone like Linkwitz do all the work and then just simply buy the designs and build his system from there.

I personally find the science to be very interesting in loudspeaker design and even though I am not the most knowledgeable person on these forums at all, I can atleast tell you what looks like a good design based on what I do know.

Hence the reason I ask about the Vandersteen speakers above as all the drivers are time aligned. However, I am a little confused about the phase accuracy of RV's designs because of the fact that the only measurement of phase looks drastically different from Tom Danleys measurements of his speakers which also claim to be phase-accurate....which looks more like the proper downward sloping curve that it should be.

On the COAX dipole front, I have seen something in regards to those designs on the web now. I cant seem to find it at the moment however.

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post #22 of 27 Old 08-29-2013, 08:51 AM
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Quote:
Originally Posted by Kimeran View Post


Hence the reason I ask about the Vandersteen speakers above as all the drivers are time aligned. However, I am a little confused about the phase accuracy of RV's designs because of the fact that the only measurement of phase looks drastically different from Tom Danleys measurements of his speakers which also claim to be phase-accurate....which looks more like the proper downward sloping curve that it should be.

The ear is relatively insensitive to phase alignment as long as both channels/ears get the same treatment.

The big payoff from phase alignment within a speaker system is smooth frequency response.

Bottom line is forget about phase accuracy as being the most important goal, and look hard at the smoothness of on-axis response first, and then the smoothness of off-axis response next.

I know this is the current Harman dogma, but it has been known to be true much longer than since Harman has been pushing it.

For example, knowledgeable people knew this when Harman (JBL) was pushing out L100s, which are a nghtmare from a phase alignment and therefore frequency response viewpoint.
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post #23 of 27 Old 08-29-2013, 09:29 AM - Thread Starter
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Ah, see that's something I also read, that phase has little to do with the overall sound but, if I remember correctly, having speakers in proper phase "integrate" better.

That raises another question though. is it better to have a speaker with constant directivity where the decibles decrease uniformly as you move off axis or is it better to have a speaker that can illuminate the entire room with the same amount of sound?

So Omni-directional speaker vs. Constant directivity speaker?

Arny, you seem to have experience with both so I am very interested in your opinion on this.

It would almost seem like the Omni-directional speaker would have a much bigger sweet spot but I have also read that with CD speakers you should cross infront of the listening position or aim it to the opposite corner of the room to fill the entire room with sound. This supposedly yields a bigger sound stage because as you move around the room the sound intensity changes from which speaker you are closest to to keep the soundstage centered....

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post #24 of 27 Old 08-29-2013, 12:51 PM
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Not Arny, but my 0.000001 cent (microcent) since I've had all sorts roll through my system over the years: Boundary and filter effects are a much bigger problem with omnis than with directional speakers. My experience has been, without room treatment, omnis tend to produce a big but smeared image and lots of FR ripples.

Phase matters most at the crossover points. Move away from the crossover frequency, and the off speaker contributes less and less so has little influence over the sound. At the crossover, having for instance the two drivers be 180 degrees out of phase will cause undesirable effects. smile.gif

I spent many years on the time/impulse-response treadmill, and while I still think it a very worthwhile goal, in (my) actual practice (movies and music) having a good impulse response is but one of many parameters leading to good sound, and probably not the most important.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #25 of 27 Old 08-30-2013, 11:34 AM - Thread Starter
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I have always heard that DonH50 that phase mainly matters if you are doing a simpler crossover...that must be why.

One thing that I am looking more at is the posibility of using Coax drivers more in lines with whta JTR and Seaton Sound make.

I can't afford either of their speakers so I may just build some of my own.

The main attraction to them though is the fact that I will be able to have all three channels matching with the center being horizontal without the lobbing or size issues that you get with more traditional speakers and horns.

Sure they will still be bigger speakers but seeing as how I can lay the center on its side makes it easier to live with.

I will still need some room treatment going this route but that is something that I am willing to do.

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post #26 of 27 Old 08-30-2013, 03:15 PM
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Yes Arny science matters, but what is personally preferred is just that.


And what I meant Kimeran,was exactly as you stated.
Others....on the genius level... do all the work, then I buy their designs.
I do this a lot.......actually I do this with almost everything, household appliances, furniture, clothing
vehicles, the list goes on and on, even my purebred dogs.....its a leave it to the professionals thing I have.
Dabbling is cool, expecting the same results are foolish.

The examples of open back co-ax are on the net.
Heres the one I own. As I said, bang for the buck,
$2500 and that comes with the amplifiers for the servo subs.
The servos play flat to 20hz....

http://gr-research.com/super-v.aspx

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post #27 of 27 Old 08-31-2013, 12:26 PM
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Well I've got both Linkwitz Orions and some very high quality constant directivity type speakers (10" woofer to waveguide with compression horn) that are DEQX corrected. They both sound great. The presentation is quite different between the two and I'm sure more to do with the difference in drive units and electronics than speaker directivity.

At a general level the soundstage with the Orions is deeper (I think soundstage depth is generally an artificial construct) but not as precise as the CD horn where images are more focused.

The bigger difference I hear though in the overall presentation is I think from the dipole vs sealed box bass and the compression driver vs dome tweeter.

FWIW the best speaker I ever heard was a dipole - the Lotus Granada.

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