# Sealed vs Dipole vs Cardioid



## Patrick Bateman (Sep 11, 2006)

At CES I had the opportunity to hear the Beolab 90, and it was quite an experience. Probably the best speaker I've ever heard. The 90 works it's magic by making the room disappear; it basically sounds like you're listening to headphones.

The way that it does this is by controlling directivity via a horizontal array. Basically the speaker that faces you plays the music, and the speakers on the side and the back of the enclosure play the same signal delayed and out of phase. The net effect is a beam like a waveguide, but without a waveguide.

An early version of the speaker was a dipole, so I wanted to evaluate the performance of dipole vs a cardioid vs sealed in a car.


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## Patrick Bateman (Sep 11, 2006)

Here's the dipole speaker. This is a Tymphany TC9. I made a pyramid shaped frame to elevate the TC9 and angle it backwards by 30 degrees. The idea is to aim the nulls from the dipole into the windshield, dash, and side window. (Dipoles radiate like a figure eight, and there's virtually no output off-axis.)









Here's the impulse response. It's amazing to see how long the "tail" is in a car; the sound is still bouncing around for about 20 milliseconds. Sound travels 13.5" in a millisecond, so that means that there's at least one round trip from the front to the back of the car mucking up the response here.









Here's the frequency response. Not too bad really.

Here's what the colors mean:
1) yellow is at the passenger's right ear
2) orange is at the passenger's left ear
3) red is between the driver and passenger
4) violet is at the driver's right ear
5) purple is at the driver's left ear

The thing I like about the response is that it's close to constant directivity in the top two octaves. The same cannot be said of the two octaves from 1000hz to 4000hz.


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## Patrick Bateman (Sep 11, 2006)

Here's the dipole speaker. This is a Tymphany TC9. I made a pyramid shaped frame to elevate the TC9 and angle it backwards by 30 degrees. The idea is to aim the nulls from the dipole into the windshield, dash, and side window. (Dipoles radiate like a figure eight, and there's virtually no output off-axis.)

In my second set of dipole measurements, I pulled the TC9 about five inches away from the windshield. The idea was that dipoles need some room to do their thing; if they're pushed right against the windshield their behavior isn't easy to predict. (I didn't take a picture of where it was.)









Here's the impulse response. If you compare it to the last post, you can see that moving it away from the windshield has cleaned up the impulse significantly.









Here's the frequency response. It's significantly worse than the first case with the dipole. In the on-axis response, there's big dips at 8000hz and 1200hz.

I think it's interesting how the impulse improves as you move it away from the wall, but you'd have to use the speaker at a very narrow bandwidth because the response is so awful.

Here's what the colors mean:
1) yellow is at the passenger's right ear
2) orange is at the passenger's left ear
3) red is between the driver and passenger
4) violet is at the driver's right ear
5) purple is at the driver's left ear









The Gradient Helsinki (pictured above) points the nulls at the listener. The idea is that Europeans don't have large homes, so putting the null towards the listener ALSO puts a null at the back wall. I tried doing this in the car, but abandoned the measurement when I realized that you're listening so far off axis, the TC9 rolls off around 10,000hz. So it DOES work - but it would only be a practical option if you were using the TC9 as a midrange, not a tweeter.


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## Patrick Bateman (Sep 11, 2006)

Here's the cardioid speaker. This is a Tymphany TC9. I made a pyramid shaped frame to elevate the TC9 and angle it backwards by 30 degrees. The idea is to aim the nulls from the dipole into the windshield, dash, and side window. (Dipoles radiate like a figure eight, and there's virtually no output off-axis.) The fiberglass absorbs a fraction of the rear radiation and converts the dipole into a cardoid.









Here's the impulse response. To me, it looks very similar to the dipole from post #2. I think what's happening here is that you need a LOT of fiberglass to attenuate the rear radiation. Just throwing it into the corner of the dash isn't making a HUGE difference (though it IS making some difference.)









Here's the frequency response. I had high hopes for a cardioid, but I think this response is inferior to the sealed response AND the dipole response.

Here's what the colors mean:
1) yellow is at the passenger's right ear
2) orange is at the passenger's left ear
3) red is between the driver and passenger
4) violet is at the driver's right ear
5) purple is at the driver's left ear









The Linkwitz mini uses a midrange as a tweeter, mounted in a PVC pipe to create a cardioid.

Something similar might work in the car; the trick would be where to put the pipe. As shown in the second set of dipole measurements, if you move the speaker too far from the windshield, you get dips in the response from reflections off the windshield.


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## oabeieo (Feb 22, 2015)

If you had some serious padding behind that dash speaker to absorb that rear wave , Dood I think this could really be something.


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## oabeieo (Feb 22, 2015)

Oh you beat me to it


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## Patrick Bateman (Sep 11, 2006)

Here's the sealed speaker. This is a Tymphany TC9. I made a semi-spherical enclosure that's small enough to put the TC9 in the stock location for the tweeters in my car. It's a good location - by pushing the speaker right up against the windshield you minimize the null you get when the speaker is a few inches from the windshield.









Here's the impulse response. It's amazing to see how long the "tail" is in a car; the sound is still bouncing around for about 20 milliseconds. Sound travels 13.5" in a millisecond, so that means that there's at least one round trip from the front to the back of the car mucking up the response here. _I'd say that this impulse response is the second best here, only bested by the dipole when it's moved away from the windshield._









Here's the frequency response. Arguably the best here. Except for an off-axis dip at 2000hz, there's no real problem here. I was surprised to see that the response goes all the way to 16000hz, even though we're listening off axis AND the speaker is jammed into a very reflective corner.

The biggest problem with the sealed enclosure is that there's no direcitivity control; above 3000hz there's as much energy going towards the driver as the passenger. The 'giant headphone' effect of the beolab 90 is because of it's directivity control.

Here's what the colors mean:
1) yellow is at the passenger's right ear
2) orange is at the passenger's left ear
3) red is between the driver and passenger
4) violet is at the driver's right ear
5) purple is at the driver's left ear


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## Patrick Bateman (Sep 11, 2006)

I love tinkering, but the more I tinker, I keep coming back to the 2009 project and thinking it worked pretty well.









Here's the response of my BMS 4540ND compression driver on a seventy-five degree waveguide on the dash of my old Accord. It's response is superior to the sealed, to the dipole, and the cardioid. 

Then again, I really need to do some measurements in my Mazda. That measurement above, from a few years ago, clearly has a ton of smoothing on it, and that makes it difficult to compare to this week's results. It's possible that the sealed is the best solution (but the sealed won't give you directivity control.)


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## Patrick Bateman (Sep 11, 2006)

I managed to dig up a measurement from 2009 with 1/6th octave smoothing.

This measurement doesn't make much sense to me. We *should* be seeing some type of directivity control here, at the very least above 2000hz. The fact that the response is so random likely indicates that I had the gate set too long.









Here's an example of what a waveguide measurement should look like. This is the JBL progressive transition waveguide, as measured by Earl Geddes.

Andy Wehmeyer has brought this phenomenon up a few times, basically that there's so many reflections in the car, you're best off treating them as part of the response.

I'm not sure that I agree with this; I think directivity control is important.

Though the waveguide approach appears to deliver the best results, it's possible that the dipole holds promise. I think the jury will be out until I repeat these measurements with a waveguide too, using the exact same mic position, gate length, etc.


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## Orion525iT (Mar 6, 2011)

Thanks for doing this. It confirms my suspicions regarding the use of dipole or cardioid in the confines of a vehicle interior. It also supports my somewhat anecdotal experience trying to get cardioid to work on my dash.

Very loose concept; and ignore practicality for now. But, I wonder if it would be feasible to use multiple smaller drivers to get directivity control out of a sealed. You would need to take multiple measurements at multiple locations, match the frequency response of the main driver, and then reverse the phase. Or something like that. Basically, use one larger main driver for output and multiple _control_ drivers to produce a cardioid pattern. Or multiple smaller drivers to help control the radiation pattern of the dipole.


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## Patrick Bateman (Sep 11, 2006)

I did some subjective listening of the sealed and the dipole setup. To make things fair, I equalized them so that both were flat and played down to about 500hz.

The first thing I noticed is that it's really difficult to make subjective comparisons when the bandwidth is so little; the lack of output below 500hz was really noticeable.

So, take these comments with a grain of salt.

The sealed option basically sounded like a car radio. With a bit of DSP added to center the image, it was easy to get the vocals up on the dash. The width of the soundstage was the width of the car. Tonality was exactly what you'd expect - it sounded like a car radio. The TC9 isn't all that different than the midranges you'd find in a stock system. It's a great driver for the money, not sure if I'd want to use it to 20khz though. Maybe.

The dipole sounded better to me. The location of the speakers was less apparent in the dipole config. It was a real interesting effect; I found that I could move the drivers significantly closer to the center of the car without narrowing the soundstage. The width of the soundstage was wider with the dipole than the sealed, no matter how narrow I set the speakers.

I think what's happening here, psychoacoustically, is that the dipole generates a lot of reflections on the windshield, and these reflections confuse the imaging cues. At CES I heard the super-expensive MBL omnipolar speakers, and they behave similarly.
















If you compare the impulse response of the sealed and the dipole, you can see the reflections in the tail of the impulse.









All is not well with the dipole however. There was a 'glare' to the sound that was really irritating. I'm not sure if the glare is due to the frequency response, or if the 'glare' is simply because the frequency response is limited to 500hz and up. It could also be distortion; while the sealed driver has no problem going down to 500hz, getting a 3" driver in a dipole to go down to 500hz is pushing it; Linkwitz crosses his 3" midrange at 700hz, and John Kreskovsky crosses his 3" midrange at 1000hz.


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## Patrick Bateman (Sep 11, 2006)

Orion525iT said:


> Thanks for doing this. It confirms my suspicions regarding the use of dipole or cardioid in the confines of a vehicle interior. It also supports my somewhat anecdotal experience trying to get cardioid to work on my dash.
> 
> Very loose concept; and ignore practicality for now. But, I wonder if it would be feasible to use multiple smaller drivers to get directivity control out of a sealed. You would need to take multiple measurements at multiple locations, match the frequency response of the main driver, and then reverse the phase. Or something like that. Basically, use one larger main driver for output and multiple _control_ drivers to produce a cardioid pattern. Or multiple smaller drivers to help control the radiation pattern of the dipole.


Much of the research on directivity control comes from prosound. And in prosound, SPL sells. Due to this, you very rarely see anyone selling anything that uses technology that lowers SPL.

I was thinking about this last night, I went to the Madeon show in Pomona, and I found it amusing that I've only heard two cardioid sub setups in the last five years. (And I go to shows 3-4 times a year.)

I think the people that rent this equipment don't want to bother with directivity control if it reduces the SPL by even one decibel.

If you use that criteria, you're going to need a REALLY big device to control directivity; to control directivity down to 100hz with an array you're going to need an array that's eleven feet long.

Beolab 90 obviously isn't afraid of wasting power to get the intended beamwidth; it uses over eight thousand watts to achieve it's results.









If you look at the frequency response of the dipole when you move it away from the windshield, you'll notice some dips in the response. This is caused by reflections off the windshield bouncing back and mixing in with the on-axis response. Because the reflections are delayed, they're out of phase at certain frequencies, and that's how we get these dips.

The obvious solution to these reflections is to use some fiberglass insulation to absorb that sound, like Linkwitz does. I made a half-hearted attempt to do that, but you could see with my results that it wasn't particularly effective.

Probably MORE insulation is the easiest way to fix that.

But another possibility would be to create a pseudo-dipole with two drivers. One on the front of the box, and one on the back. The back would be out of phase. The secret sauce here is that you can filter the back driver so that it's not playing ALL the frequencies, just SOME of the frequencies.

For instance, you could have one driver on the front of the box playing 500hz to 20khz. The woofer at the back of the box could play 500hz to 5khz. By eliminating output above 5khz, you also eliminate that null at 7khz that you see in the measurement above.
So basically the speaker is a dipole from 500hz to 5khz, because the front driver and the back driver are playing, and they're out of phase. Above 5khz it's a plain ol' monopole; only the front driver is playing. We want that monopole radiation above 5khz because you can see in my dipole measurements that the dipole has dips in the response at high frequency when you pull it away from the windshield.

Does that make sense?









If you really wanted to go nuts with this, you could use FIR filters to vary the phase with frequency to get the optimal response and directivity. And once you do that it will start to look a lot like a KII Audio 3 or a Beolab 90.


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## Patrick Bateman (Sep 11, 2006)

As illustrated here, the pyramid shape works pretty good on the dash. The sloping walls of a pyramid allow you to push the speaker into the corners, while clearing the windshield.









The Kii audio 3 is an active cardioid with the drivers on the side and back, as explained in the previous post

















It occurred to me that you could do something similar with a pyramid shape, so that it fits on the dash better. The reason that this works is because the back driver isn't playing full-range; in the example I described in the previous post I only want to run the rear driver up to 5000hz. So due to that, it doesn't matter if the driver is tilted; we're running it in a range that the radiator is omnipolar, so the tilt won't matter.

So the front driver would play about 500hz to 20000hz, the rear driver is out-of-phase and it's playing 500hz to 5000hz. The combination behaves like a sealed box from 5000hz to 20,000hz, and like a dipole from 500hz to 5000hz. You could probably even throw in a third or fourth driver to increase the output. I think the reason that this would work is that you don't need a lot of output to create a null. Here's why:

If you have two drivers and they're in phase, you're going to get 6dB more output
If you have two drivers and they're out of phase, you get zero dB.
So if you combine *three* drivers in phase, one one out of phase, you'll have more output on axis, and something less than a perfect null to the rear. It won't be a sealed box, it won't be a dipole, it will be something in between. I imagine the radiation would look something like cardioid.

The next question here would be how far apart they should be. In a dipole, they're at the exact same location, they're the same driver. In this type of active setup, with 2-4 drivers playing in a single box, we'll want to keep them tightly spaced. (If they're too far apart it won't work as a dipole at higher frequencies.)

I *think* keeping them within one-quarter wavelength is probably a good goal. That means that if they're within three inches of each other, it will work as a dipole from 1125hz and down. (13,500 inches per second / 3" / 4 )

The good new is that we can improve on that with delay; we know which direction we want the sound to go so we can use digital delay to line up the wavefronts. That means we can likely get it to work as an active dipole above 1125hz, maybe all the way up to 5000hz.


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## Orion525iT (Mar 6, 2011)

Patrick Bateman said:


> But another possibility would be to create a pseudo-dipole with two drivers. One on the front of the box, and one on the back. The back would be out of phase. *The secret sauce here is that you can filter the back driver so that it's not playing ALL the frequencies, just SOME of the frequencies.
> *
> For instance, you could have one driver on the front of the box playing 500hz to 20khz. The woofer at the back of the box could play 500hz to 5khz. By eliminating output above 5khz, you also eliminate that null at 7khz that you see in the measurement above.
> 
> ...


Yes, that is what I was getting at. I don't think this would need to be perfect either to get beneficial results. You might be able to make major improvements by simply mitigating or attenuating the gross anomalies. 

In todays world of inexpensive dsp and inexpensive amp channels, you can really start to look at things completely differently than in the past. Since I have a car PC with pretty damn good analog output simultaneous to digital into minidsp 4x10 HD, I might try this in future just to see. Of course there will still be the visual aspect of psychoacoustics to deal with as I suspect something like this will be invasive.


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## Orion525iT (Mar 6, 2011)

Do we care if we get directivity control at all frequencies? It seems to me that we only need to destroy the frequencies that have nulls due to interference. If we get summation, we don't care. We just need to eq down the peak. In the case of a null, we need to generate a signal to destroy the interference before it causes issues with frequency response.


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## jwsewell01 (May 28, 2015)

Bear with me for a moment. 

Looking back at your cardioid setup, .... Would heavily stuffing the "chamber" and using resistive membranes to further dampen the rear waves work? 
Attenuating the reflections before it exists the device?

What little I have learned suggests that attenuating the rear signal 12dB is the goal.

My next audio purchase SHOULD be a UMIK-1 and learning REW.


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## Patrick Bateman (Sep 11, 2006)

I'm a big fan of copying **** that works. For instance, my favorite sub of all time is my copy of a Danley TH-Mini that I made.









For my dipole experiments, I'm using a 3.5" woofer. (http://www.parts-express.com/pedocs/specs/264-1062--tymphany-tc9fd18-08-spec-sheet.pdf)









John Kreskovsky uses a Scanspeak 10F/4424G for his reference speaker, which measures about 4" in diameter. https://www.madisoundspeakerstore.c...anspeak-discovery-10f/4424g-4-midrange-4-ohm/









John appears to be using a 3rd order low pass at 6000hz and a 4th order highpass at 1000hz. Due to the high excursion caused by not having an enclosure, the 4" woofer is highpassed at 1000hz. In a conventional sealed box it would probably play three octaves lower.









Siegfried Linkwitz uses a SEAS H1658-04 for his reference speaker, which measures (you guessed it) 4" in diameter. http://www.madisound.com/loudspeaker_specifications/H1658-04_MU10RB-SL_Datasheet.pdf









The crossover points for the reference Linkwitz speaker are nearly identical; only the slopes are slightly different.

This tells me that the xover points, the driver diameters, and the xover slopes are mostly dictated by geometry. IE, no need to get experimental here, just copy John and Siegfried.


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## Patrick Bateman (Sep 11, 2006)

Yesterday I'd mentioned that the Tymphany TC9s had some "glare" when run as a dipole.

And I'd also uploaded data from Linkwitz and Kreskovsky that indicated a couple things:

1) they're using a crossover point of about 1000hz
2) they're using larger drivers; I'm using a 3.5" and they're using a 4"

Based on that, I decided to try a driver with more displacement, the SB Acoustics 5", that sells for a whopping $23 : https://www.madisoundspeakerstore.c...stics-sb13pfc25-04-5-4-ohm-paper-cone-woofer/

OMG, what a difference. *I think this might be the best staging I've ever pulled off in a car.* My Unity horns from 2009 were pretty nice, but this is definitely some next-level ****.

Some things I noticed:

1) The soundstage was wider than the car
2) After tinkering with the delay on my MiniDSP, I was able to get the soundstage centered on the dash
3) Most importantly, the "glare" of the Tymphany TC9s was gone. So I think it's safe to say that the "glare" I was hearing was caused by distortion; the TC9s don't have enough displacement to play below 1000hz in a dipole in a car. In a home it would probably be even higher.



I took some pics of my setup, but it was super ghetto, I basically had the SB13s sitting on the dash in the corners. Worked great.

Here's some random subjective observations about various positions:

1) I think the best sounding position was under the dash, where you'd put HLCDs. I think the carpet on the floor is absorbing a lot of the backwave. So basically you get that 'giant headphone' effect that's a result of the high directivity of a dipole, without the 'glare' of the reflections off the windshield
2) My second favorite location was up on the dash, basically cross fired in the corners of the dash
3) I tried some weird orientations, like firing straight up, but all the treble went away. These locations might work well with dedicated tweeters and dipole midranges
4) I tried putting the speakers in the kick panels, but that didn't work well. The width of the stage disappeared, and the treble did too. *I think that dipoles work best when they're far away from walls.* I think that's why they worked well where HLCDs go; in that location they're about a foot from the floor, about 18" from the firewall, and the only nearby reflections are the dash and the door. And both of those locations are in the 'null' of the dipole, so the reflections off the dash and the door aren't noticeable. Basically the car seems to disappear and you have a giant soundstage. Neat.


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## danssoslow (Nov 28, 2006)

Are you kidding me?!? I think I speak for everyone when I say that there is no judging going on with the pics. Super ghetto or not, I'd like to see them.


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## jwsewell01 (May 28, 2015)

danssoslow said:


> Are you kidding me?!? I think I speak for everyone when I say that there is no judging going on with the pics. Super ghetto or not, I'd like to see them.


 Yeah, what he said..... 

I'm picturing a 5 inch woofer dangling under the dash.


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## oabeieo (Feb 22, 2015)

danssoslow said:


> Are you kidding me?!? I think I speak for everyone when I say that there is no judging going on with the pics. Super ghetto or not, I'd like to see them.


I thought the same thing . I wanna see that

My car is a full blown experiment and some next level **** too I'll even post a video of mine , So I def won't judge
I see the dash speaker but no wire going to it  

If this is for reals I WANT to try it .


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## Kevmoso (Jun 4, 2013)

Why am I thinking an under dash dipole array of Whispers is the next logical step?

Edit to suggest ND91's?


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## Focused4door (Aug 15, 2015)

Patrick Bateman said:


> Yesterday I'd mentioned that the Tymphany TC9s had some "glare" when run as a dipole.
> 
> And I'd also uploaded data from Linkwitz and Kreskovsky that indicated a couple things:
> 
> ...


Firing straight up on the dash? That seems counter-intuitive since further away worked better in other locations


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## oabeieo (Feb 22, 2015)

Kevmoso said:


> Why am I thinking an under dash dipole array of Whispers is the next logical step?
> 
> Edit to suggest ND91's?


I heard a spl car that had a array of 3" speakers under dash and I about crap my pants how good it sounded . . IIRC it was 4 speaker in a row and a tweet at the ends . And it was some hifonics amps and some flea market deck .


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## piyush7243 (Sep 9, 2009)

I was thinking of doing a dipole in car but never thought about the pyramid kind of shape for mounting. How is the effect when you start bringing the pair near the center of the dash. How is the width. I'm planning to try these with 3 inch full range drivers running 500hz up. Let's see how it pans out. Thanks for some great info

Sent from my Nexus 6P using Tapatalk


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## danssoslow (Nov 28, 2006)

oabeieo said:


> I thought the same thing . I wanna see that
> 
> My car is a full blown experiment and some next level **** too I'll even post a video of mine , So I def won't judge
> I see the dash speaker but no wire going to it
> ...


Do you still have those Audax mids? How about hanging the off the bottom of the horns and check it out!

Tbh, that scenario would be exactly what I'd be interested in. Is the efficiency greatly reduced? Is that wide stage there? 

My man! Dooooo iiiit!!!!!


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## Patrick Bateman (Sep 11, 2006)

oabeieo said:


> I thought the same thing . I wanna see that
> 
> My car is a full blown experiment and some next level **** too I'll even post a video of mine , So I def won't judge
> I see the dash speaker but no wire going to it
> ...


The setup was super simple.










Picture a dash, but with 5" woofers in each corner. They're firing straight up.

The reason that this works is that the nulls are pointed right at your head. (A dipole speaker has nulls off axis; if you're listening on the edge of the speaker, you're in a null.)

So when it's firing straight up, you're hearing the reflection off of the windshield, not the speaker itself.

Worked really nice, give it a try.

I found that the setup worked better under the dash, with the speakers located in the same spot as where you'd put an HLCD. I mounted them in that spot by placing the woofers on a couple of paint cans to move them away from the floor.

*Note that none of this works unless you equalize the speakers; if you don't equalize them they're going to sound really thin and awful.* All this dipole stuff depends on equalization to flatten the response. (See Linkwitz Lab - Loudspeaker Design)


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## piyush7243 (Sep 9, 2009)

So a pair on right n a pair on left. 90 degrees to the dash. Above dash or below dash

Sent from my Nexus 6P using Tapatalk


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## Patrick Bateman (Sep 11, 2006)

piyush7243 said:


> So a pair on right n a pair on left. 90 degrees to the dash. Above dash or below dash
> 
> Sent from my Nexus 6P using Tapatalk


Nope, just one on each side.

Dipole speakers aren't all that different than regular speakers, except they radiate in a figure eight.

The key is that the nulls are off axis.

If you play music through a speaker without an enclosure and listen on the edge you can hear what I mean; the low frequencies are inaudible.

This is the key; with no radiation to the edges you can eliminate the early reflections by pointing the nulls at the side of the cars and the windshield.


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## piyush7243 (Sep 9, 2009)

Patrick Bateman said:


> Nope, just one on each side.
> 
> Dipole speakers aren't all that different than regular speakers, except they radiate in a figure eight.
> 
> ...


Got it. I tried that in 1 full range I tried a couple of days but the highs are not as pronounced . it was kind of a open baffle. I will give it a try. I assume that both speakers are pointed towards listener n back towards the corner or windshield

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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> The setup was super simple.
> 
> 
> 
> ...


Where's the minidsp and the speakers in the pic. 
You have the factory head? Or have a BT aux somewhere ? 

So the speakers you posted had 4"s on blue stands , do it like that?


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## Patrick Bateman (Sep 11, 2006)

piyush7243 said:


> Got it. I tried that in 1 full range I tried a couple of days but the highs are not as pronounced . it was kind of a open baffle. I will give it a try. I assume that both speakers are pointed towards listener n back towards the corner or windshield
> 
> Sent from my Nexus 6P using Tapatalk


If you try it, be sure to do it in stereo.

The dipole radiation reduces reflections off axis, and does a really nice job of making the car "disappear"


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## Patrick Bateman (Sep 11, 2006)

oabeieo said:


> Where's the minidsp and the speakers in the pic.
> You have the factory head? Or have a BT aux somewhere ?
> 
> So the speakers you posted had 4"s on blue stands , do it like that?


That's not my car, I just used the pic as an example

When I did it, I used the PC in my garage as a source and just ran the wires from the pc in the garage into the car. The setup was:

PC -> minidsp -> four channel amp -> SB acoustics 5" speakers, one per side


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## piyush7243 (Sep 9, 2009)

Patrick Bateman said:


> That's not my car, I just used the pic as an example
> 
> When I did it, I used the PC in my garage as a source and just ran the wires from the pc in the garage into the car. The setup was:
> 
> PC -> minidsp -> four channel amp -> SB acoustics 5" speakers, one per side


So do you aim them so that the magnet rests on dash or cone is towards rear view mirror?

Also as I understand both should be out of phase with each other. Right?

Sent from my Nexus 6P using Tapatalk


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## piyush7243 (Sep 9, 2009)

Please put some pictures of setup on the dash. Would love to see

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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> That's not my car, I just used the pic as an example
> 
> When I did it, I used the PC in my garage as a source and just ran the wires from the pc in the garage into the car. The setup was:
> 
> PC -> minidsp -> four channel amp -> SB acoustics 5" speakers, one per side


Oh okay .... I definitely don't want you to think I was questioning you down, I was just curious about the settings that you had on the screen for the miniDSP, 
I definitely am going to try to gently experiment with it


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## oabeieo (Feb 22, 2015)

As promised sometime today I'll post a vid of my hoop tie


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## Orion525iT (Mar 6, 2011)

Patrick Bateman said:


> Picture a dash, but with 5" woofers in each corner. They're firing straight up.
> 
> The reason that this works is that the nulls are pointed right at your head. (A dipole speaker has nulls off axis; if you're listening on the edge of the speaker, you're in a null.)
> 
> ...


Got any measurements on the way? Where do you think the low end cut off is with the 5"? 

Can you qualify "better" in regards to the lower placement? How were the 5" oriented in that location?


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## Patrick Bateman (Sep 11, 2006)

Orion525iT said:


> Got any measurements on the way? Where do you think the low end cut off is with the 5"?
> 
> Can you qualify "better" in regards to the lower placement? How were the 5" oriented in that location?


Normally I'm big on measurements, but in this case, I just hooked them up, ran three measurements, EQ'd the setup with miniDSP, re-measured, then listened.

The whole thing took less than an hour and most of the time was spent listening.

The reason I didn't do a ton of measurements was that there didn't seem to be a lot of correlation between what I was hearing and what I was measuring. The soundstage was clearly better with the dipole, but the maddening thing was that every little thing I tried sounded different. This isn't the case so much with sealed boxes; if I turn a sealed box a few degrees I don't hear a difference, but with the dipole setup the angle was very noticeable.

I'll post some sims in a sec, that I did in an attempt to figure WTF is going on.


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## Patrick Bateman (Sep 11, 2006)

OK, so I ran a bunch of sims using hornresp to try and figure what's going on with the dipole speakers.

I think the easiest way to visualize this is with hornresp, basically you can recreate your room (or car), put the speakers where they're located in the real world, and then simulate various wavelengths.

























Here's the directivity and wavefront shape if you put a sealed box in the corner. This is basically equivalent to the corner of my dash, which looks like this:










The white dot in the lower left hand corner is the sealed speaker. The sims are done at 500hz, 1000hz, and 2000hz. Above 2000hz, the wavelengths are so short the sims kinda fall apart. But they're really handy for anything below 2khz. Kudos to David McBean for enhancing Hornresp per my request to do this. (http://www.diyaudio.com/forums/subwoofers/119854-hornresp-593.html#post4582505)

The wavefront and directivity are basically what you'd expect; there's no directivity and it doesn't matter if you're in the drivers seat or in the passenger seat, the output level is basically the same.










Here's an actual measurement of a sealed speaker in this location in my car, the measured results seem consistent with the sim.


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## Patrick Bateman (Sep 11, 2006)

OK, so I ran a bunch of sims using hornresp to try and figure what's going on with the dipole speakers.

I think the easiest way to visualize this is with hornresp, basically you can recreate your room (or car), put the speakers where they're located in the real world, and then simulate various wavelengths.

























Here's the directivity and wavefront shape if you put a dipole in the corner and you crossfire it. This is basically equivalent to when I did this:








So the driver's side dipole is pointed at the passenger, and the passenger side dipole is pointed at the driver.

The white dot in the lower left hand corner is the dipole speaker. The sims are done at 500hz, 1000hz, and 2000hz. Above 2000hz, the wavelengths are so short the sims kinda fall apart. But they're really handy for anything below 2khz. Kudos to David McBean for enhancing Hornresp per my request to do this. (Hornresp - Page 593 - diyAudio)

There's some interesting things going on here. At 2000hz, there's significant directivity; see how the passenger side is "hotter" than the driver's side?
At lower frequency, the response shape starts to look like a sealed box, but at a lower level. Perhaps this is why Linkwitz and Kreskovsky use so many drivers in their speakers; it looks like you only get that narrow directivity when the wavelengths are smaller than the speaker. IE, Linkwitz and Kreskovsky only run their midranges down to 1000hz. They use a 4" midrange. 1000hz is 13.5" long. So it looks like they're trying to keep the speaker operating in a range where it's beaming. This is probably also the reason that the LX Mini uses a four inch midrange as a "tweeter" instead of a conventional tweeter.










Here's an actual measurement of a dipole speaker in this location in my car, the measured results seem consistent with the sim. Note how it starts to get directional at high frequency.


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## Patrick Bateman (Sep 11, 2006)

OK, so I ran a bunch of sims using hornresp to try and figure what's going on with the dipole speakers.

I think the easiest way to visualize this is with hornresp, basically you can recreate your room (or car), put the speakers where they're located in the real world, and then simulate various wavelengths.

























Here's the directivity and wavefront shape if you put a dipole in the corner and you point the edge of the driver at the passenger. This is basically equivalent to what Gradient does here:








So the driver's side dipole is pointed at the driver's side window, and the passenger side dipole is pointed at the passenger side window. And if you look at the speaker on the passenger side, you're looking at the edge of the frame. (Again, look at the woofer on the Gradient Helsinki and you'll see what I mean.)

The white dot in the lower left hand corner is the dipole speaker. The sims are done at 500hz, 1000hz, and 2000hz. Above 2000hz, the wavelengths are so short the sims kinda fall apart. But they're really handy for anything below 2khz. Kudos to David McBean for enhancing Hornresp per my request to do this. (Hornresp - Page 593 - diyAudio)

This is probably one of the most interesting ways to mount the dipole. In this config, you can clearly see it's possible to 'aim' the null. In this sim, the null is aimed at the passenger. But you could point it anywhere really.


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## Patrick Bateman (Sep 11, 2006)

In the last post, I showed how you can 'aim' the null anywhere in the car. Similar to what Gradient does.




























I had a 'Eureka' moment when I realized you could combine the dipole with the sealed. So you get the ability to AIM the sound, like a dipole gives you, but you can also make one side of the speaker louder than the other.









This is fairly similar to what the LX Mini does









And what Kimmo Saunisto did here : Cardioid bass









Here's Kimmo's measurement

Kimmo is getting about six dB of rejection to the rear. That probably doesn't sound like a lot; why go to all this trouble for six dB?

Here's why:

Something I found out today, when simming with Hornresp, is that the corner basically amplifies the sound. IE, the sound radiates in all directions, some of it goes towards you and some of it goes backwards. (Sound radiates spherically.) The problem is that *the sound that goes into that corner gets amplified because it's radiating into such a small space, similar to how horns work. So the first wave is basically swamped by the reflection.

It's real interesting, because I didn't figure this out until I added some walls in the Hornresp sims. Without the walls, the speaker behaves quite predictably, but stick it in the corner and all hell breaks loose.

So... reducing that back wave by six dB is a big deal. It would be great to reduce it by ten or twenty dB, but a cardioid won't do that.

The sealed + dipole combo is probably the most compelling one here, because it gives you positive aspects of both:
1) you get the directivity of a dipole, but without the pesky radiation to the rear. In a car, I'd really like all the sound to go ONE way, not ALL directions.
2) you get a lower cutoff than a dipole; John K and Linkwitz are high passing their midranges at 1000hz, that's a really difficult high pass in a car, where we don't have a lot of space

*


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## Patrick Bateman (Sep 11, 2006)

OK, so I ran a bunch of sims using hornresp to try and figure what's going on with the dipole speakers.

I think the easiest way to visualize this is with hornresp, basically you can recreate your room (or car), put the speakers where they're located in the real world, and then simulate various wavelengths.

























Here's the directivity and wavefront shape if you put a five driver array in the corner. This is fairly similar to when I did this:










The white dots in the lower left hand corner are the array of sealed speakers. The sims are done at 500hz, 1000hz, and 2000hz. Above 2000hz, the wavelengths are so short the sims kinda fall apart. But they're really handy for anything below 2khz. Kudos to David McBean for enhancing Hornresp per my request to do this. (Hornresp - Page 593 - diyAudio)

I can kinda see why midrange arrays never work for me. The sound is too hot on the driver's side; it's literally the opposite of what we want. (Ideally I'd like the driver's side speaker to project towards the passenger, and vice versa.)

The obvious solution to that is to curve the array, but yowza was that a **** show. I tried all kinds of curved and delayed combinations, and all of them sucked. (AFAIK, there was no way to simulate these type of arrays with readily available software until David added the feature last month. The big boys like JBL and Meyer use software that costs thousands of dollars.)

The array performance is remarkably bad. Besides being too hot on the driver's side, it also shifts at high frequency, and then becomes too hot on the PASSENGER side.


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## Patrick Bateman (Sep 11, 2006)

If anyone's made it this far in the thread, the "sealed + dipole" seems to be the winner.

Here's some losers:


























Here's a variation on the last post.

This is an array, like this:










*But I made one small change, which improved performance quite a bit.*

I put ONE of the six drivers out of phase.

Here's my reasoning:

We can see that the dipole works well.
But you can make a dipole using TWO speakers instead of one; just use two sealed boxes and flip the polarity on one. Boom! Instant dipole.

So my 'hunch' was that you could stick one driver out of phase, in the corner of the dash, so that it would 'soak up' some of those nasty reflections that color the soundstage so much.

And it seems to work; if you looks at the directivity of this array, versus the last array, this one is better. And everything else is identical; it's the same location, all I did was flip the polarity on ONE speaker.


























Here's an odd one. This is the same array as post 44, but I used digital delay to create an 'end fire' array. I'd expected some real directivity, but oddly enough, it did the opposite, it's basically behaving like a single sealed speaker. I think the problem here is that I only used one delay, whereas a "true" end fire array will have five delays, one for each of the six speakers in the array (except for the one that's not delayed, the one in the back.)

If anyone wants to mess with end fire, they look promising. I ran some sims and got better results than this when combining end-fire PLUS a conventional array. Basically you have a set of boxes that look like a tic tac toe board. The end-fire combines with the array spacing and they reinforce each other. I can now see why this is a fairly common set up at stadiums these days.

I also ran some sims that combined end-fire with that 'trick' I mentioned earlier, where one driver is out-of-phase. I won't bother to post it, as this combo worked no better than simply putting one driver out of phase in the array.


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## Patrick Bateman (Sep 11, 2006)

Whoah, that was a mega post. In summary, the sims seem to show that:

1) if you want directivity, the sealed + dipole seems to offer the most promise. I've only tried dipole so I can't tell you if it works or not.

2) if you want directivity, a horizontal array looks promising, but with some caveats:
a) Flip the polarity on the woofer that's closest to the corner. This will soak up some of the reflections that occur in the corner and clean up the directivity. And this improves soundstaging.
b) While it might be tempting to curve the array or aim the array, I found that if you move the drivers even a few inches away from the corner, everything goes to hell. This is because there's a very strong reflection off of the corner, so the delayed waves screw up your directivity and you wind up hearing the REFLECTION more prominently than the incident wave. (yuk!)

3) Sealed is without a doubt the simplest, but it offers little to no directivity. This is likely the reason why it's so difficult to make a car stereo NOT sound like a car stereo, unless you go to Herculean lengths like what Jon Whitledge did when he put the Magic Bus together. (Basically using extensive room treatments that would be impossible/impractical in a regular sized vehicle.)


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## Patrick Bateman (Sep 11, 2006)

Siegfriend Linkwitz gets down to 1000hz with a 4" midrange on a dipole









John Kreskovsky gets down to 1000hz with a 4" midrange on a dipole









Gradient gets down to 250hz with a 5" midrange on a cardioid

I think I'm going to try for something like Gradient. I really love the sound of those dipoles, and I highly recommend that anyone tries it. But I just can't figure out where I'm going to put an 8" midbass, a 4" midrange and a pair of 1" tweeters. I came up with a bunch of zany designs, but none of them simmed too well.

The Gradient is compelling because it doesn't require as much space or as many drivers.


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## lurch (Jan 20, 2014)

another wonderful and amazing post from Patrick, THANK YOU FOR ALL THE TIME AND EFFORT, Sir !!!

now that each and every one of my synapses are fried it's time to veg out with some
mindless television.


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## oabeieo (Feb 22, 2015)

http://youtu.be/y5LacVUMqSg


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## piyush7243 (Sep 9, 2009)

Crazy stuff Patrick, going to try with a 3 inch n 4 inch midrange now. Will update the thread soon

Sent from my Nexus 6P using Tapatalk


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## Patrick Bateman (Sep 11, 2006)

lurch said:


> another wonderful and amazing post from Patrick, THANK YOU FOR ALL THE TIME AND EFFORT, Sir !!!
> 
> now that each and every one of my synapses are fried it's time to veg out with some
> mindless television.


Thanks! I haven't had a project actually work out in months, so this is kinda exciting 

I was listening to a set I'd heard about a hundred times on the SB Acoustics dipoles on Sunday, and I've never heard it sound that good. Amazing.


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## Patrick Bateman (Sep 11, 2006)

piyush7243 said:


> Crazy stuff Patrick, going to try with a 3 inch n 4 inch midrange now. Will update the thread soon
> 
> Sent from my Nexus 6P using Tapatalk


Cool!

Be sure to equalize so it's flat, and play around with aiming it. The edge of the woofer will have a null.


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## piyush7243 (Sep 9, 2009)

Patrick Bateman said:


> Cool!
> 
> Be sure to equalize so it's flat, and play around with aiming it. The edge of the woofer will have a null.


Yep equalization will be done by Helix DSP pro and I will make sure that its a little bit up from the dash to take care of null part. Have done this with Hiqphons earlier n really loved them. Also in this kind of dipole setup I presume we don't have to invert the phase on other speaker.

Sent from my Nexus 6P using Tapatalk


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## oabeieo (Feb 22, 2015)

Yeah. That's dope ! I gave it a try today. Sorry my video is gay I had no light so I skipped it


I tried doing it with a 3rd set of midbasses . 
It just sounded like a speaker with no baffle ****n the bed . 

I need try it with midrange so I can get its benefit .


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## Patrick Bateman (Sep 11, 2006)

oabeieo said:


> Yeah. That's dope ! I gave it a try today. Sorry my video is gay I had no light so I skipped it
> 
> 
> I tried doing it with a 3rd set of midbasses .
> ...


Yeah one of the reasons that I decided to go with a resistive cardioid, like Gradient uses, is because trying to mix sealed and dipole together is tricky. From the sims I ran, it looks like sealed and dipole will work well IF they're lined up exactly. (And I assume this is one of the reasons that Linkwitz puts the dipole right on top of the sealed speaker in the LX mini.)

If the wavefronts aren't aligned, it looks to be a bit of a mess, because you get off axis nulls in unpredictable places.

Not saying that mixing sealed and dipole WON'T work, just saying I'm not up to the challenge at the moment.

I drew up a resistive enclosure for a Tymphany TC9 last night, just need to print it.


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## jwsewell01 (May 28, 2015)

I have the " luxury" to do whatever I feel like in the cab of my truck and have often wondered why I really even need a dashboard other than a place to mount gauges and a Headnit.

Here is an old drawing I made awhile back.



The idea I have banging around in my head now is to build the dash very similar but remove the lower section of the dash on each side as well with LX521 inspired tops on each side. 

Am I crazy to even try this? Lol


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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> Yeah one of the reasons that I decided to go with a resistive cardioid, like Gradient uses, is because trying to mix sealed and dipole together is tricky. From the sims I ran, it looks like sealed and dipole will work well IF they're lined up exactly. (And I assume this is one of the reasons that Linkwitz puts the dipole right on top of the sealed speaker in the LX mini.)
> 
> If the wavefronts aren't aligned, it looks to be a bit of a mess, because you get off axis nulls in unpredictable places.
> 
> ...



Let us know how it pans out. 

I had some time this morning so I can unhook my midranges and ran them as a dipole in what I noticed I really couldn't hear any reflections but I could localize the speaker very easily , so , if I had a 2" driver sealed and out of phase and carefully aimed at windshield next to my dash pods o bet I could tame some of the 800hz muck that bounces around. 

I need a set of whispers.

So Patrick, here's the actual vid I made. In the video I have a waveguide I want to cut down on left side , if I shave the top off it and Make the windshield the horn flare on the top could I expect good results. ??????

I did that before on the big waveguides and I cut them down too much so I had to order another set but I also got the smaller ones I'm thinking these will work a lot better than when I have on the right side sounds freaking awesome, I just need the left side to fit where gauge hump is.

Here's the vid 
http://youtu.be/Ex3JAgPNuho


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## Patrick Bateman (Sep 11, 2006)

The weird thing with dipoles is that you can aim the nulls.









Here's what the wavefronts look like with a dipole, when you listen off axis. (See how Gradient does it? The edge of the woofer is aimed right at you.) And you can 'steer' that null, so you can reduce the output to a specific part of the car. For instance, if you want the drivers side driver to be quieter than the passenger side, you could use a dipole on the drivers side and point the edge at the driver. (Keep in mind, there's no real reason you have to listen to a speaker on-axis if you don't need to play it full range.)









Here's the wavefront of a sealed speaker; see how the response is the same, no matter where you are?


The reason I bring all of this up is that a setup like the LX521 might no be ideal in a car, because a lot of sound is going to radiate *backwards* right into the windshield. In my experiments, I found that a setup like Gradient is superior.


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## Patrick Bateman (Sep 11, 2006)

In another thread I posted recently, I was all but ready to give up on directivity control. But in order to progress on THAT project, I need to wait for some parts for my 3D printer.

So, in the meantime, I thought I'd take another look at cardioids, to examine some of the theories I espoused over here:

http://www.diymobileaudio.com/forum...scussion/316602-end-fire-arrays-new-post.html

For the next experiment in this thread, I'd like to evaluate a 'mixed cardoid.' A 'mixed cardioid' is a cardioid that's created from a sealed combined with a dipole. (You can also make a cardioid electronically, a la Beolab, or resistively.)









For the 'sealed' part of my 'mixed cardioid', I am going to use a Cambridge Soundworks satellite. Cambridge made some nice computer speakers about 10-20 years ago, and these satellites are readily available on Craigslist for around $40 for a complete set.









Here's the frequency response and distortion of the Cambridge satellite. Not too bad for five bucks. I've seen higher distortion from woofers that cost 10-20x as much.









Here's the polar response. You can see why these sound so good for the money; the midrange fits into a window of +/- 3dB, at virtually any angle. (These measurements go all the way to the back of the loudspeaker.) The upper treble is fairly "hot" but this can be ameliorated by listening off-axis.


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## Patrick Bateman (Sep 11, 2006)

I've been raving about these satellites that I made for another project. They sound great. Although I measured them once, I lost the data.

So today's a good day to measure them again.

I'm using the exact same criteria that I used for the Cambridge Satellite, so you can compare them "apples to apples."









Here's the frequency response and distortion of the speaker. Amazing huh? Try beating that for ten bucks. Heck, I can't think of anything under $100 that measures this well. There's a gently rising response, but like the Cambridge Satellite, this can be ameliorated by listening off-axis.

I could listen to this speaker all day long.









Here's the polar response. These are really good; if you look at the polar response of waveguides from the 'great waveguide list'(1) there are few waveguides that have directivity this good. (And note - there's no waveguide here, at all!)

I think what's going on is that the spherical shape is eliminating diffraction. And if you understand how diffraction works, it basically behaves like a second set of speakers, but delayed ever-so-slightly in time. So if you can eliminate diffraction, you clean up the polar response. And I think that's what we're seeing here.

It's also interesting that even the distortion is smoother. (Compare the harmonic distortion of the Cambridge in post 59 to the Tymphany in this post.)

To appreciate how important the enclosure shape is, consider this:
_At 45 degrees off axis, the high frequency response of the Cambridge Satellite extends to 5000Hz.
At 45 degrees off axis, the high frequency response of the Tymphany 'egg' extends to 14,000Hz - more than an octave higher, and nearly the limit of human hearing._

(1) http://www.diyaudio.com/forums/multi-way/178187-great-waveguide-list.html


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## Patrick Bateman (Sep 11, 2006)

As noted a couple of posts ago, it is possible to make a cardioid by combining a sealed box with a dipole. In the pic above, that's exactly what I am doing.

I am combining the sealed box from post #60, with an SB Acoustics SB65 full-range.









It's the same idea as Kimmo Saunisto's subwoofer from here : Cardioid bass
The only difference is that I'm doing it with a midrange, not a subwoofer. You just have to scale all of the dimensions down.









Here's the frequency response and distortion of the 'mixed cardioid' pictured above.

Some observations:
1) Note that this measurement has EQ; cardioids require it. The other measurements I posted today do not.
2) Efficiency went up quite a bit; about 4-6dB









Here's the polar response of the mixed cardioid. Some obserations:

1) The polars of the 'egg' shaped enclosure from post #60
2) In a 'true' cardioid, there's more energy going to the front than the back. There's a modest amount of cardioid behavior going on in the two octaves from 600Hz to 2400Hz. But it's not consistent; at some frequencies the speaker is directional, at other's it's not.

I think the issue here is that the sealed box needs to have a small driver, and the dipole needs to be large. This is because the dipole will roll off much higher than the sealed box. For instance, a 3" woofer in a dipole will start rolling off around 1000Hz, but in a sealed box, it can play three octaves lower, about 125Hz.

So this 'mixed cardioid' of sealed and dipole can work, but the dipole part of this equation needs to be larger.


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## Orion525iT (Mar 6, 2011)

I argued in a thread a good bit ago (can't remember which thread) that cardioids don't work when you have near reflections because the wave fronts don't develop properly. As Andy pointed out, everything in a car is a near reflection.

However, I did borrow from the LXmini and made it so the dominate first reflection was _very, very_ near. It was a bounce. I set it up so that outside of the very near reflection, the cardioid pattern was relatively free to develop. You are limited in the upper frequencies because of the bounce, but this setup was the most directional thing I ever had in my car. It was kind of shocking. The setup was so directional that it actually created a large hole in the center of the stage. 

I hope to experiment with this more, but right now the crazy midbass bandpass boxes I am building are devouring my soul (very promising however). The biggest draw back is that the Lxmini like design is visually obtrusive. There was no illusion about speaker location. I can't think of a good solution for the visual cues, but there might be some flexibility in the shape that will still function like the Lxmini.


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