Midgard Audio Gaia [NEW PHOTOS! Nov 09.] fullrange controlled dispersion system

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Snickers-is

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Hi!

First of all, I am new here, so please let me know if this is posted in the wrong circle.

Midgard Audio is a company dedicated to developing and manufacturing of audio equipment. We have a really outdated website, but a new one is right around the corner.

Last year an enthusiast in search for the ultimate high end system contacted me and started asking a series of questions about how to select the right gear, what to look for and so on. I gave him a lot of answers and tried to explain the theories behind all the acoustics and electronics involved. The main problem he ran into was which speakers could integrate in his room without causing problems like room resonances, standing waves in the bass region, non linear ambiance, early reflections and so on. I showed him some crazy sketches to a system with total dispersion control at all frequencies, and he caught immediate interest.

The Gaia project was born, or more accurately, reborn almost a year ago. At this moment it was a dipole/horn system with four 15inch woofers, and a 10" midbass in horn, a 4 inch midrange in horn and a small dome tweeter, also in a horn. Through the making of dozens of horns I discovered that they only narrowed the dispersion, but it was still as tilted as before. Different types of waveguides were tested, and this revealed that the dispersion pattern was much wider at high frequencies with a typical waveguide. However, it was not easy to find a waveguide shape that offered no reflections, no energy build up and no diffractions and still worked as more than just a baffle. The solution were to experiment with different angles at every step away from the driver (since each distance is responsible for emitting each frequency), make different alignments for domes and cones, and to narrow the frequency band in which they were to operate.

The result was a set of waveguides with a new shape, and the midrange was split to a upper and lower midrange.

Dipole bass also seemed to cause some challenges, both because this only allows for effective in room performance with a very limited extension of the bass region, and because it does give any considerable output power at the lowest frequencies. The solution to this was simply to combine closed cabinet and dipole. This is done by putting two woofers at the back of the enclosure and two woofers at the front of the enclosure. The two groups (rear and front) are then measured in room both in phase, out of phase and at a variety of different phase angles between 0 and 180 degrees in order to get a picture of the phase relations that gives the best 3D dispersion effect in the bass region at each different tiny frequency point. By adjusting the phase response relation between the two groups one can pull out the best compromise between closed cabinet, dipole, desired SPL and so on. The concept gets even more complicated as the adjustment can be done both in phase and delay, and it can be done to both the front and rear pair of woofers. The sum of the four woofers in the end is then corrected to get the best possible impulse and frequency response in room.

These two systems seemed to work really fine by them self, but combined there must be some kind of cross over point. This is the point where the system crosses over from limited dispersion monopole, to either dipole, bipolar or something in between. To solve this, the front firing subwoofers are placed inside the midbass dispersion lenses, and the rear woofers are added smoothly in where the room dimension allows them to without giving an unwanted contribution to the sound image.

The sketch below shows the final design. It is currently about to be built as a finished speaker. There is a lot more to say about this, but my wife and my daughter wants me to join them for dinner right now.

« Last Edit: 9 Nov 2007, 12:23 am by Snickers-is »

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #1 on: 19 May 2007, 05:51 pm »
Hi again!

Selecting the drivers for this project was a project of its own. The criteria of each driver had to be set extremely high off course, but each driver has a different task than in most traditional speakers. For example the lower midranges work in a narrow band, and stops at around 1500 Hz. They also tend to get a boost at lower frequencies as they get help from the dispersion lens. This not only calls for a falling response, but also very low distortion due to the amplification in the lens. Some hard cones, metal or ceramic, seemed to be an obvious choice, but the break up point had to be far out of the working range. Ideally it should be one octave above 3 times the cross over frequency.

For lower midrange, midwoofer and subwoofer the drivers are all cone drivers. The magnet systems of all the drivers are among the most linear and symmetric ones made to date. The upper midrange drivers are 4,5 inch magnesium cone drivers with full copper ring treatment and good ventilation to improve both the dynamic and thermal compression figures. They have their break up point at almost 7 times higher than the cross over frequency, and the 8,5 inch midwoofers with a construction similar to the lower midrange drivers are crossed over even further from the break up point.

Similar to the lower midrange and midwoofer drivers the domes also have a different task than in many traditional speakers using similar domes. The upper midrange domes are 2”, and they are crossed over to the lower midrange drivers at around 1500Hz. That is as low as some tweeters, and they extend to well above 5kHz. The working range of both the upper midrange and tweeter no domes would be suitable. The most important property of the midrange and tweeter domes is they sound in their respective working area. When a few alternative domes were picked out they were tested with different dispersion lenses. The chosen midrange domes stood out from the rest because they performed both flat on and off axis. Several tweeter domes however did that too, but only one had a response curve as flat as the chosen one in addition to having an off axis response in the dispersion lens that extended flat above 20kHz.

The search for woofers was probably the biggest challenge in the driver selection process. We needed someone that could make a subwoofer with high excursion, almost like a car subwoofer, but we needed a well working cone, in combination with the right parameters and a linear motor structure. We ended up with 5 alternatives. Two was removed due to noise from the moving parts, one due to poor build quality and one that did come very close was removed because it could not give the same level of linearity and symmetry as the one we chose. The drivers have a total linear displacement capacity of 31 litres, and 46 litres mechanical. That is more than one cubic foot of linear displacement! Only a very few extremely expensive speakers on the market today are capable of as much as 1/5 of that.

 :drool:

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #2 on: 19 May 2007, 08:15 pm »
So what makes Gaia a milestone in audio loudspeaker technology?

The secret lies partially in technology, and partially in how the ear works.

Several independent scientific tests have been done in order to determine what kind of parameters who are very audible and what type of parameters are less audible. These tests conclusively end up with frequency response as the most audible parameter of them all. Peaks are the worst of all errors in a response curve. Second to them comes tilted response. After this comes dips, and on the last place of the frequency response issues comes the frequency extension. All of these conclusions are off course based on a “not too terrible version”. What is commonly available today is the base for what type of errors that were put into the test.

They also conclusively end up with one other parameter that totally knocks out harmonic distortion, phase response, group delay, timing issues, impulse response and so on. This is the dispersion pattern, or energy response as I like to name it. This is about having perfect audio performance in the direction of the listener, and then filling up the room with some 20-30dB peaks and dips.

This entire thing is not about forgetting about phase, distortion, and so on, but it is about not forgetting parameters that are even more important. The trend is to use a dome tweeter, crossed over in the 2k-4k range, using a 4-7inch midrange, and not additional treatment of the drivers dispersion characteristics. The tweeters dispersion at 3kHz is often some decibels above a similar 7 inch woofer at 3kHz at 30 degrees. At 60 degrees this difference is even larger. Take a look at these two drivers that represents high quality standard drivers in the market:

The Seas 27TFFC textile dome with rear chamber:
http://www.seas.no/Prestige%20Diskanter%20PDF/27TFFC_881ny06.pdf

The Seas CA18RNX 7” coated paper cone driver:
http://www.seas.no/Prestige%20Basser%20PDF/CA18RNX-H1215-08.pdf

From 0-30 and from 30-60 degrees off axis the tweeter drops almost nothing at all. The woofer drops only 3dB at 30 degrees, but at 60 degrees it drops 12 dB! This means that when we have checked out just 1/3 of the total dispersion of the drivers the difference in energy emitted from the two drivers are 1/16. And the difference only gets bigger in the 90-180-270 degree range.

So here is an example:
Imagine that you are sitting in your listening chair. In front of you there are two perfect speakers aligned in a typical setup like this:



They have perfect dispersion and integrates perfectly in the room. The dispersion is showed as the disc on the floor below the speakers:



This should sound perfect in any aspect, however, if the speaker is not perfect, and the rear firing sound is not as good as the front firing sound, but almost equally loud. Then we could imagine the system as four speakers like this:



The red speakers are now facing away from the listener, directly towards the wall representing the rear firing sound from the speakers, while the blue speakers are facing towards the listener representing the directly radiated energy of the speaker system.

Let us also imagine that the situation is, as with most available loudspeakers, that the red speakers have peaks and dips in the 30dB range while the blue speakers are within 2dB at the significant parts of the audio band. The integration between the two should be something like this:



Then the big question is: Could you hear if the rear firing bad sounding speakers were turned off?

The answer is obviously yes. Not because we believe so, but because we, and many others have tested this many times. The audibility of this is also pretty high because the errors are extremely large. Just imagine what a small tweeter, a large midrange, low cross over frequency (within the ears most sensitive range) and a steep filter does to the difference in midrange and tweeter in room energy. Depending on the off axis energy and the amount of reflections from the room surfaces the reflected sound can in many cases be more than 70% of the total energy that enters our ears, while the directly radiated sound is less than 30%.

By levelling out the energy response in all of the frequency bands with dispersion control lenses, or sound projection lenses as we call them, from the tiny tweeter SP-lens of just 20sqcm to the midbass SP-lens of almost 17000 sqcm the dispersion is as well as entirely flat from 20kHz down below 100Hz.

Watson

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #3 on: 19 May 2007, 08:47 pm »
So what makes Gaia a milestone in audio loudspeaker technology?

I don't mean to sound negative, but generally it's poor form to start making these kind of claims before you've actually built the speaker and listened to it.

Your ideas are interesting though. 

Why did you choose to use an WMTMW configuration with the waveguides?  The waveguides push the acoustic centers so far apart that you're going to get severe vertical combing.  It seems you've prioritized smooth horizontal dispersion at the expense of extremely poor vertical dispersion.  Wouldn't a regular WMT configuration with the waveguides better meet your goals?  Do you have any simulations of the vertical dispersion that you can post?

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #4 on: 19 May 2007, 09:10 pm »
So what makes Gaia a milestone in audio loudspeaker technology?

I don't mean to sound negative, but generally it's poor form to start making these kind of claims before you've actually built the speaker and listened to it.

Your ideas are interesting though.
 

You are free to listen and jugde for yourself. They will be showed at several Norwegian shows this autumn. I am not sure if we will make it to Las Vegas next year, but I hope so. But this is not as "untested" as it may seem.

Why did you choose to use an WMTMW configuration with the waveguides?  The waveguides push the acoustic centers so far apart that you're going to get severe vertical combing.  It seems you've prioritized smooth horizontal dispersion at the expense of extremely poor vertical dispersion.  Wouldn't a regular WMT configuration with the waveguides better meet your goals?  Do you have any simulations of the vertical dispersion that you can post?

The reason is simple. The summed energy response (if you take a vertical array for example 10-30 degrees off axis above or below the listening axis) will turn out flat. This would not be possible with a WMT-configuration. You do not listen to many specific angles off axis,  but simply the sum of a lot of angles. Another way to put it is that the WMTMW configuration will be more diffused than a WMT.

I do not have any graphic stuff to show you about the lagging, but in simple numbers you can change listening height within about 2 feet without having to worry about the response.

If you look at a single graph at 45 degrees off axis it will have a lot of peaks and dips. But this is not repeating at the next and previous angle. So the sum of all off axis energy is pretty much flat. The off axis energy is also very limited so the proble with early reflections will be more or less insignificant (depending on the size of the room).

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #5 on: 19 May 2007, 10:36 pm »
I must also add that the calculations of the vertical dispersion is made at a 3 meter listening distance. These speakers will probably be used pretty often at even longer distances, and probably never at shorter distances thn 3 metres.

MaxCast

Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #6 on: 20 May 2007, 01:04 am »
as snickers-does   :P
welcome to AC.  Good luck with your speaker.

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #7 on: 20 May 2007, 02:19 am »
Thanks MaxCast!

By the way, in Norwegian "is" is the same as "ice" in English, so Snickers-is is actually Snickers ice cream.

Hogg

Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #8 on: 21 May 2007, 03:07 pm »
Interesting product.  Tell us a little about the amps on the web site.  Thank you.

                                                     Jim

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #9 on: 21 May 2007, 04:31 pm »
Sure,

they are class D, pre and post filter NFB, H-bridge output, SMPS power supply amplifiers with passive (and silent) temperature control.

They have an extremely precise and dynamic soundstage with extreme bass control. A few weeks ago I rebuilt a couple of 801 Nautilus with active cross over. It sounded like some cross over between extremely refined horn speakers with SET amps but with the upper end of a well integrated high end dome tweeter. The bass in this system is simply of another world.

That system has been auditioned by, among oghers, B&W 800D series, Avantgarde acoustics and Klipsch owners and their conclusion is that this was way beyind their wildest expectations.

I am not sure what more to tell you, please ask for the details you want to know.

The retail prices are (approximately):
Oberon 2.1: 800€ each
Oberon 4.1: 1000€ each
Oberon 6.1: 1200€ each
...including VAT and shipping in EU. Outside EU the prices are pretty much the same in most countries.

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #10 on: 22 May 2007, 02:36 am »
There is one driver I have not yet mentioned. It is the ambience tweeter. This is a tiny tweeter with matched sensitivity located on the back of the speaker.

The main tweeter has, like any other tweeter, limited dispersion at higher frequencies. This is basically compensated for trough the SP-lens of the dome, but the dome naturally reduces the dispersion even more than the SP-lens can compensate for. This effect grows stronger when approaching and passing 90 degrees off axis. This means that in the 15kHz region there are almost no energy at all, but at lower frequencies there is a significant bit of energy.

To compensate for that, the SP-lens helps out a bit. It gives the tweeter a smoother off axis high frequency roll off than the driver just baffle mounted.

However, the rear tweeter will not have the same roll off and dispersion pattern just out of the box as the front tweeter. But that is not the intention for the rear tweeter, because it is not intended to produce a pin point stereo image in the back of the speaker. Its main task is to fill out the missing energy behind the speakers, and to do so it is not pointing directly to the wall. Further it is adjustable through several steps in order to integrate to a specific room width, rear wall distance and ceiling height.

The location and angle of the rear firing tweeters is selected so that they should transfer a minimum of energy directly to the listener. The direct sound will interact with the main tweeters and we do not want that to happen.

In an anechoic chamber the rear tweeters are almost impossible to track in an on axis system measurement, while the summed energy response (the sum of all on and off axis energy from the speakers) can be adjusted flat. However, the speakers are always used in an environment that is not anechoic. Since the dispersion pattern above 20kHz is not identical to the pattern at 1kHz local walls and surfaces will affect the subjective energy response from the rear tweeters. Therefore, they have to be room customized in every listening room.

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #11 on: 23 May 2007, 07:53 am »
Some might find it pretty boring to read so much about dispersion, so this chapter is about vibrations and damping.

The cabinets of Gaia are constructed of a large number of parts. Not only are the enclosures and internal “horn shapes” consisting of a large number of parts, but there are several enclosures and smaller units stacked together to form the entire cabinet which at first glance looks pretty simple. All of these units are acoustically isolated from each other.

The bottom and top are separate panels isolated from the speaker with a soft rubber gasket. The bottom panel is also isolated from the floor using another soft rubber gasket. In the middle of the speaker there is another panel like the bottom and top panel. This is where the midrange and tweeter section is assembled to the enclosure. This piece is isolated both from the upper and the lower cabinet the same way as the top and bottom panels. The bottom panel is also isolated from the floor in order to prevent vibrations from being transferred to the floor.

On the sides of the Gaia four pieces of glass are attached to the speakers. Between them and the enclosures there are more soft rubber gaskets. The glass is then put into the water jet cut aluminium fixing points using even more soft rubber gaskets. The fixing points are attached and tensioned to the bottom, mid and top panel, and they, as mentioned above, are acoustically isolated from the rest of the cabinet.

The two upper and lower woofer/midbass cabinets are one piece inner enclosures. They are acoustically isolated from the outer enclosures using soft rubber gaskets between the walls, so the visible parts of the cabinets are just the outer frames. The inner cabinets slide into the frames from behind, but before that the fabric frames, which are also a part of the midwoofer SP-lens, is dropped into the outer frame through a hole in the top of the outer frame. They are then squeezed into place by the inner enclosures. The fabric frames are also acoustically isolated both from the inner enclosures and from the outer frames by soft rubber gaskets.

The way the speakers are put together the inner enclosures can then both move forwards and backwards, but also extract and retract them selves without transferring a significant amount of vibrating energy to the room, the floor or to other parts on the speakers.

Since the fixing point for the midrange/tweeter SP-assembly is acoustically isolated from the outer cabinets, which are also acoustically isolated from the inner enclosures, there is no additional acoustic isolation between the midrange/tweeter SP-assembly and the main cabinet fixing point. This would only cause the midrange/tweeter assembly to sag over time. However, the entire cavity of the SP-assembly is filled with a compound acting as a vibration damping.

This compound is different from other acoustic damping compounds. Traditional materials like bitumen and similar deform when exposed to mechanical energy. This means that they pick up energy and transfer it to heat. The energy transfer is time based. The acoustic material allows the panel to vibrate and store energy and the density and amount of acoustic material dictates the reverb time for these resonances.

The compound used in Gaia acts like a soft hardening fluid cancelling system. The difference from the energy transforming materials is that the compound bounds with the material and cancels out any vibration in the surface of the material before it can be stored, and therefore it has a much shorter reverb time. It can be tuned to work effectively at all frequencies in the audio band and the properties can easily be custom tuned to the application.

In Gaia this means that the relatively thin outer glass fibre and acrylic shell is more effectively damped than a massive construction would be. It does not only reduce vibration from the midrange and tweeters, but also the acoustic vibrations from the woofers and midwoofers. In addition to that it also helps removing the back energy from the lower midrange cone drivers.

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #12 on: 22 Jul 2007, 11:26 pm »
Hi folks!

Things are about to be ready now. I left the workshop 2 weeks ago now, and I am waiting for the cabinets and parts to arrive.

I got some images from the cabinet building process. I will post more soon:

By using a vacuum bag the side panels get their right shape:



Side panels and inner enclosures before laquer, veneer, cutting and some other parts:



The plug for the front horn die at the CNC table:


Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #13 on: 7 Sep 2007, 08:47 pm »
After a long time of waiting for some basic parts, we are finally back on track.

The mould plug arrived, in MDF and a few big faults:

Here one of the medium holes are fixed (if you could call that fixed) with a piece of MDF:


Right beside the centre hole there is a pretty large dip, and the flat area in the background is not very flat at all.


But after hours of fixing and sanding the result turned out like this:


Tomorrow the plug takes off to the moulder. In a week I hope to have the finished parts ready for testing and lacquer.

The cabinets and glass parts will show up in about a week too.



I'll post some more building process images if anyone likes to see that kind of stuff...

Duke

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #14 on: 11 Sep 2007, 11:33 pm »
Hello Snickers-ice,

I just now found this thread, and your loudspeaker concept is quite interesting.  I'm also a believer in putting a lens on the projector, so to speak...

You wrote:  "They also conclusively end up with one other parameter that totally knocks out harmonic distortion, phase response, group delay, timing issues, impulse response and so on. This is the dispersion pattern, or energy response as I like to name it."

I agree very much with that statement.  Again and again, differences I hear between loudspeakers can be traced to their radiation pattern characteristics.  You Norsemen seem to have a better grasp of this than the rest of us - Gradient, Amphion, Genelec, and now Midgard are all companies that pay a great deal of attention to radiation patterns (some more than others).  Any theories as to why that is?  Maybe you have to spend more time indoors due to the cold, and so you spend more time listening to music and making observations about what sounds right and what doesn't?  Or, could it be a Viking thing - an affinity for the role reverberant energy plays in a large hall? 

By the way, your English is excellent - you don't even write with an accent!

Your shallow waveguides look to me like they would give an unusually wide radiation pattern.  Can you tell me what the pattern is?  Are they constant-directivity devices? 

I like your idea of a rear-firing tweeter to fill in the power response in the top octave, as that makes sense if your radiation pattern is very wide and uniform across the rest of the spectrum and your goal is good "energy response".

You mentioned adjusting the phase and even delay of your multiple woofers.  What sort or pattern do you end up with in the bass region - a dipole, a cardioid, or something else? 

Overall, it looks to me like you thought about how an ideal loudspeaker would interact with its environment, and then set out to create a speaker that would embody that vision.  My hat is off to you on your innovative approach.

Very best of luck to you and your company.

Duke
« Last Edit: 12 Sep 2007, 04:13 am by Duke »

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #15 on: 15 Sep 2007, 10:44 am »
Hello Duke!

Thank you very much for your kind words.

You wrote:  "They also conclusively end up with one other parameter that totally knocks out harmonic distortion, phase response, group delay, timing issues, impulse response and so on. This is the dispersion pattern, or energy response as I like to name it."

I agree very much with that statement.  Again and again, differences I hear between loudspeakers can be traced to their radiation pattern characteristics.  You Norsemen seem to have a better grasp of this than the rest of us - Gradient, Amphion, Genelec, and now Midgard are all companies that pay a great deal of attention to radiation patterns (some more than others).  Any theories as to why that is?  Maybe you have to spend more time indoors due to the cold, and so you spend more time listening to music and making observations about what sounds right and what doesn't?  Or, could it be a Viking thing - an affinity for the role reverberant energy plays in a large hall? 


Hehe, I do not think it is a Viking thing  :lol: However, I believe that running a pretty small company gives two large advantages that a big company does not have.

If you take B&W as an example, I think they are the biggest in their segment in the world. I think they have an annual turnover of around 160 000 000$. This turnover is necessary for them in order to stay in business and to keep all the employees occupied. If, at the moment, a couple of people plan to purchase a pair of B&W's within the next year, and this planning together stands for let's say 75% of their total turnover the next year, they will depend very much on those people. Since their plans are made more or less based on exixting models from B&W, it is also necessary for them to release new models that do not diverse to much from the existing models.

If they totallt changed their model line they would get a very unpredictable future.

For us the ideology is almost the perfect oposite. Not because we are necessarily smarter, but because we only need a fragment of B&W's or someone elses customers in order to grow to what we consider as big. By thinking in new ways and showing that we are different we can get the attention from people and that is what leads to sales. That is what I think is the small companys second advantage. We are forced to make innovations while the large ones are in some ways forced to avoid them.

When it comes to the energy response thinking you must not forget that this is not new, neither it is limited to Norway, Finland and a few more. Legacy, VS, Mirage, KEF, Avantgarde (and every other horn speaker manufacturer), Martin Logan, and off course Sound Lab... The list goes on and on. In the 80's the Canadian official audio organisation run some tests that among other things concluded that dispersion is the second most important parameter of audibility (off course with some approximation to "how much harmonic distortion is the same as how much dispersion error" and so on.)

When you started building speakers (according to your website) the invention of CD was made by Philips. But at the same time the dome tweeter entered the arena in far more commercial products than before. This lead to the many statements of digital sound (which in many situations were correct, but in even more situations were caused by over tuned tweeters). The adjustable RIAA stages enabeled people to make ear friendly sound, which was not easy to correctly measure because of the lack of availability of reference signal on vinyl records.

Then another thing happened. The larger loudspeaker manufacturers had now lead the "accepted state of the art loudspeaker developement" for a few years when the CD and the dome tweeters were fully entering the high end segment. No real correction for the tweeter dispersion matter was implemented, and many simply very good amplifiers did not match in a system like that at all. Some older constructions, both solid state and tube gear, matched far better because they were more "forgiving" in the tweeter range (low order harmonic distortion, often acellerating at higher frequencies). This again lead to the general acceptance of big amplifiers with clearly coloured sound. These amps now leading the high end amplifier market in many ways made the loudspeaker industry avoiding the dispersion pattern problem, because the speakers were measuring quite ok on axis, and with a state of the art expensive amp they also sounded quite ok.

Then take into account that technical steps in this industry are often small and they can take ceturies to be accepted. This is also the time when many of the large companies today were established.

By the way, your English is excellent - you don't even write with an accent!

Thanks! I try to avoid accidents  :thumb:

Your shallow waveguides look to me like they would give an unusually wide radiation pattern.  Can you tell me what the pattern is?  Are they constant-directivity devices?

Many people talk about a frequency where the drivers start beaming. This is, off course, very theoretical. When you measure the off axis response in the 10-30 degrees range the shallow WG's measure flat, or more correctly, they measure the same at 10 and 30 degrees, just with a few dB drop off at 30 compared to 10. At the upper frequency point of this linear range the dispersion pattern is almost exactly the same as when the drivers natural dispersion pattern without waveguide. This means that you also have to take into account the drivers natural dispersion pattern.

You mentioned adjusting the phase and even delay of your multiple woofers.  What sort or pattern do you end up with in the bass region - a dipole, a cardioid, or something else? 

This depends on the room. you can set a dipole pattern at 60Hz, a cardioid at 40, something in between at 30 and so on. By measuring the room at different phase relations between the two driver groups you can determine the ideal type of dispersion for each frequency. Then you can set a complex phase, delay and SPL curve for the front and the rear groups separately so that they combined has a minimum group delay, they activate as little problems with room modes as possible and the response curve ends up completely flat. You can not achieve this by using dipoles or closed cabinets with electronic correction, because we can not just control the energy in sweetspot, we can also control the energy ammount other places in the room, and this way you will not get the typical fealing that "something has been corrected"

Overall, it looks to me like you thought about how an ideal loudspeaker would interact with its environment, and then set out to create a speaker that would embody that vision.  My hat is off to you on your innovative approach.

Very best of luck to you and your company.

Duke

Thank you!  :D

Snickers-is

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Re: Midgard Audio Gaia fullrange controlled dispersion system
« Reply #16 on: 1 Oct 2007, 10:46 pm »
The first audition of the finished speakers:


Snickers-is

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The speakers were showed in a 700 Sqft room. It appeared to be ok, but not to big.



It was a very difficult room. Glass, concrete, metal and other hard materials were dominating the room. No furniture except from a few simple chairs, and a very thin floor charpet made an annoying flutter echo. But the speakers performed actually very good. When passing the side from the front to the rear of the speakers the entire midrange and tweeter range appears to not be coming from the speakers any more but from the room itself. Despite that the dispersion in the listening area appears much more like a wide dispersion system than a horn or dipole system.

Double Ugly

Obviously I don't know how they sound, but you have yourself one unique speaker there, Mr. Snickers.

Very cool.  :thumb:

arthurs

What's the price tag on those bad boys?