Improve Your Soundstage for $2

[TAMUmpower]

Originally Posted by derickveliz

Done!





.

Who did you order your dash mat from. Is that suede or velour? I getting one soon but I'm not sure if suede kills reflections as good as carpet...but I'd hate to put carpet on the dash of a BMW. Input?

[ReticulatingPigeonElf]

Originally Posted by TAMUmpower

Who did you order your dash mat from. Is that suede or velour? I getting one soon but I'm not sure if suede kills reflections as good as carpet...but I'd hate to put carpet on the dash of a BMW. Input?

I'd consider fiberglassing some thin dash panels and gluing closed-cell foam on them... dumb idea?

[derickveliz]

Originally Posted by TAMUmpower

Who did you order your dash mat from. Is that suede or velour? I getting one soon but I'm not sure if suede kills reflections as good as carpet...but I'd hate to put carpet on the dash of a BMW. Input?

I got the Ltd edition! looks ok, and takes good care of the reflections.

The black one I have is really black but the camera changes the color a little bit, I went with black because it has no sun reflexions like the gray & smoke.

I got a bunch of samples and did a lot of testing. I believe Carpet has a better fit, but I don't like the way carpet looks like.

Dash Mat










D.

[Jprice2708]

Would there be much difference between choosing a sphere the same diameter as the speaker (say 4" for a 4" speaker) and having just a dome rear, vs choosing a larger sphere than the speaker (say 6" sphere for a 4" speaker) and having the speaker mounted on a more curved front surface? I'm assuming the extra volume in the enclosure would probably be good, but would there be much in the way of other benefits? Also for a Focal 4w2 would it be better to port the ball or have it sealed (if anyone knows - I can't find any technical specs on the 165w2 set online at all)

[Patrick Bateman]

Originally Posted by Jprice2708

Would there be much difference between choosing a sphere the same diameter as the speaker (say 4" for a 4" speaker) and having just a dome rear, vs choosing a larger sphere than the speaker (say 6" sphere for a 4" speaker) and having the speaker mounted on a more curved front surface? I'm assuming the extra volume in the enclosure would probably be good, but would there be much in the way of other benefits? Also for a Focal 4w2 would it be better to port the ball or have it sealed (if anyone knows - I can't find any technical specs on the 165w2 set online at all)

Yes, size matters. [insert joke here]

A roundover reduces diffraction down to a certain frequency, and then it's ceases working. So the bigger your woofer is, the bigger roundover you need. That's why I started this thread with a tweeter - you get the most "bang for the buck" with a tweeter roundover, since it doesn't have to extraordinarily large to make an audible difference.

The math on the how big the roundover should be is in the first couple pages.

[94VG30DE]

Earlier explanation on how to calculate your size: Post #17 Page 1

Originally Posted by Patrick Bateman

The problem with felt is it doesn't operate very low; below 15khz it doesn't make much of a difference.

A roundover operates down to 1/4 wavelength of the roundover's radius.

That's another thing too; it doesn't *have* to be a sphere. Anything that's done to reduce diffraction will yield an audible and measurable improvement.

You could look at this as a series of stages, and each stage is cumulative. IE, do some of them, or all of them for full effect.

• Use a roundover with a radius that's equivalent to one quarter of the frequency you need to cover. For instance, to go down to 2000hz you'd use a roundover with a radius of 1.6875".
• Go all the way and use a sphere. A sphere is basically a roundover on all sides.
• Add a waveguide to the face, and round THAT over.

If you look at the profile of the B&W, you can see the woofer's cone itself forms a waveguide. For a tweeter you'd need to build one. Even *without* a waveguide on the tweeter, the enclosures shape reduces diffraction.

And reducing diffraction makes the speakers disappear.

[Jprice2708]

Originally Posted by Patrick Bateman

If you're using a sphere, the radius of the sphere is calculated like this:
required sphere radius = 13500 / lowest frequency / 2 / pi
If you're using a simple roundover, the radius of the roundover is calculated the exact same way. That's because we're basically taking a sphere and "quartering it."
required roundover perimeter = 13500 / lowest frequency / 2 / pi
You can work from the other direction too. For instance, if you're at Home Depot, looking at PVC, and trying to figure out what size is adequate, here's the calculation.

Lowest frequency = 13500 / 2 / pi / radius of roundover
For instance, you're standing at Home Depot, and trying to figure out if 2" PVC pipe will do the job. First, you have to take that pipe and quarter it, so that it give you a roundover with a radius of 1". A PVC pipe with a diameter of 2", chopped into four pieces, will give you a roundover with a radius of 1" and a perimeter of 1.57. ( pi / radius / 2)
Plugging those numbers into our equation, we find that a 2" PVC pipe, quartered, will reduce diffraction down to 1368hz. (13500 inches per second / 2 / 3.14159 / 1.57"[/font][/size]

I'm assuming this is the equation you mentioned Patrick, but it has me confused, as it looks in the explanation like you are using perimeter and radius interchangably and they are very different measurements if I remember my maths properly It has been many loooong years since high school lol, but any clarification would be great.

[Scooter-Man]

I went from dash mounted PG RSD tweeters (that were probably producing some disfraction due to install) to this set up. This really smoothed out the harsh upper freqs, especially at louder volumes. Overall, I'm very pleased with the results.





Old Tweeter Set-up

[rexxxlo]

these have to be some of the coolest pictures i have seen

i like how the focus is really sharp where it counts and kinda fuzzy around the edges

i bet it sounds as good as it looks

Originally Posted by TAMUmpower

Who did you order your dash mat from. Is that suede or velour? I getting one soon but I'm not sure if suede kills reflections as good as carpet...but I'd hate to put carpet on the dash of a BMW. Input?

[derickveliz]

Originally Posted by rexxxlo

these have to be some of the coolest pictures i have seen

i like how the focus is really sharp where it counts and kinda fuzzy around the edges

i bet it sounds as good as it looks

Thank you, yes they sound pretty good, I'm about to move the Mids, my stage is not where I want it, also I'm experimenting with the woofer up front!

Here is my BUILD,

Thanks again.

.

[douggiestyle]

Hi Patrick,

I've gone over this whole thread a few times and still have some questions. I'll post them here as I think they will help others down the line.

1. Your big point is to eliminate sharp edges to reduce diffraction. The orb shape helps the sound "curve" around which essentially aids longer sound waves. Based on this, is there a scenario where speheres DON'T make sense?

For example, with Derick's (great) pods


or katodevin's here


wouldn't diffraction still occur where the orbs meet the pillars/dash? Would moulding these into the a-pillars while eliminating sharp curves be a better way to eliminate diffraction? Examples such as:

Mikamouse (tweets)


dvflyer


gutz


In other words, is the key word to this really two parts:
1. eliminate sharp edges, and
2. spheres are a CHEAP and EASY and EFFECTIVE way to accomplish this

[douggiestyle]

Also (sorry I have a bunch of Q's)

1. for katodevin's mid pods, does the implementation cause diffraction at the edge since it is more of a half-circle w/ sharp edges all the way around. It's been raised a few tims but never directly addressed by you.

2. Along the same lines, using your formula to find the needed radius, doesn't that depend on the speaker size? For example, if running a tweeter down to 2000hz, a radius of 1.07inches is needed. But using a .75" tweeter vs. a 1.25" tweeter will change the spot at which to cut the orb... so that should change certain parameters, right?

3. When using a super tweeter like I intend to, say 6000hz, only a .36 radius sphere is needed (.716 diameter). The tweeter I'm using, LG26nfa, has a flange making it 2" wide. Is there any benefits of an orb in this case?



4. Finally, for the mid, if diffracting down to 1000hz, a 4" diameter sphere is needed. However (if sealed) internal volume before displacement is only .55 liters while the recomended is .75l enclosure for F3 of 150hz. I plan to cross these down to 200hz, would the diffraction benefits outweigh the compromise of an optimum enclosure?

Sorry for the list of questions, and thanks again for sharing your insight!

[9mmmac]

Originally Posted by Patrick Bateman

Thanks! I've been doing horns and waveguides for almost two decades now, and the improvement that I've seen from adressing diffraction (almost) has me considering "conventional" components again. The improvement in soundstaging is just ridiculous.

I first noticed it with the Anthony Gallo speakers a few years back at CES. They use ridiculously cheap drivers, and they're basically a glorifed Bose system, yet they sound a million times better than they should. Considering the junky components you'd think they'd sound like crap, but they sounded better than speakers that cost ten times as much.

Really made me think about how they sound so good.

This is cool, but it also really freaks me out. I keep thinking of War of The Worlds. Is it going to melt my face with a plasma death ray? OTH, I see floor and desk lamps here. Can I get some at my fave thrift shop, run the cables up like the power wire and put some nice pods in the lamp housing? Hmmmm.

[MDubYa]

So hypothetically I could put my tweeters in a tennis ball and they would image better?

Edit: Nevermind... I just read tge whole article... Well I feel like a horses pa-toot!

[MDubYa]

Patrick,
I've been reading and now I have a question, most people in this section are putting their tweeters in the A pillars or near the dash... Would the sphere idea still work if I mounted my tweeters in a sphere and mounted the sphere in my door panel????

[Patrick Bateman]

Originally Posted by douggiestyle

Hi Patrick,

I've gone over this whole thread a few times and still have some questions. I'll post them here as I think they will help others down the line.

1. Your big point is to eliminate sharp edges to reduce diffraction. The orb shape helps the sound "curve" around which essentially aids longer sound waves. Based on this, is there a scenario where speheres DON'T make sense?

For example, with Derick's (great) pods


or katodevin's here


wouldn't diffraction still occur where the orbs meet the pillars/dash? Would moulding these into the a-pillars while eliminating sharp curves be a better way to eliminate diffraction? Examples such as:

Mikamouse (tweets)


dvflyer


gutz


In other words, is the key word to this really two parts:
1. eliminate sharp edges, and
2. spheres are a CHEAP and EASY and EFFECTIVE way to accomplish this

Here's my take on your questions. I've been interested in audio for a couple of decades. For the majority of that time, I had "upgradeitis." I was constantly replacing amplifiers, re-arranging my room, and swapping loudspeakers. It wasn't uncommon to purchase two sets of loudspeakers in one year.

About three years ago I splurged and bought me a set of Summas, and I now listen to them for about 10 hours a day. (I work at home.)

So a lot of the threads that I start are experiments based on using some of the design principles in the car.

So, back to your question. Is there a scenario where spheres don't make sense?

I'll throw out a quote from Geddes to answer that one. "Only agregious amounts of distortion in a loudspeaker are an issue. Once these are brought down to reasonable levels then its other things, like polar response, diffraction and dynamics that are the significant issues."*

I think that statement sums up loudspeaker design fairly well. If you want a loudspeaker that you can live with, focus on polar response, diffraction, and dynamics.

It takes a helluva large enclosure to get world-class directivity - here's a picture of Geddes with his speakers to give you an idea of how big they are. They're hyoooooge:



So, admittedly, directivity control in the car is a challenge.

That leaves diffraction and dynamics. And the great thing about battling the diffraction problem is that it's fairly easy to do. Especially at high frequencies, it really doesn't take much of a roundover to make an audible effect.

As for whether mounting them in the A Pillar, versus putting them into spheres is superior? I'd say put 'em in spheres and try various locations in the car. The thing that I've noticed with spherical tweeters is that you can frequently get a *wider* and *deeper* stage by pulling them away from the windshield. Experimentation is key. (And it's fun too!)

As for the third pillar of loudspeaker design, I'd say dynamics is worthy of a whole 'nother thread.

It would also be interesting to discuss which pillars are the most audible. Diffraction? Dynamics? Polar response?

* New White Paper posting - Page 19 - diyAudio

[keep_hope_alive]

thanks for the idea. i read this thread yesterday and made this today. Hobby Lobby had solid wood spheres (with one flat side with a predrilled hole) for $1.69. i didn't want to use styrofoam or plastic.

I used a hole saw to make the initial opening
then used a paddle bit to clean out the inside
my paddle bit was too small so i used a dremel to finish it out
i used the dremel to perfect the opening size
i drilled a hole for the speaker wire
...all in about 15 minutes

had some older 3/4" Alpine tweeters laying around

i like my first attempt.

will be doing this with Hertz Mille tweeters tomorrow














two sizes


i have a stand-off idea using a machine screw and hollow brass tubing.

then paint and cover with grill cloth or not, or whatever.

[rugdnit]

Originally Posted by keep_hope_alive

thanks for the idea. i read this thread yesterday and made this today. Hobby Lobby had solid wood spheres (with one flat side with a predrilled hole) for $1.69. i didn't want to use styrofoam or plastic.

I used a hole saw to make the initial opening
then used a paddle bit to clean out the inside
my paddle bit was too small so i used a dremel to finish it out
i used the dremel to perfect the opening size
i drilled a hole for the speaker wire
...all in about 15 minutes

had some older 3/4" Alpine tweeters laying around

i like my first attempt.

will be doing this with Hertz Mille tweeters tomorrow














two sizes


i have a stand-off idea using a machine screw and hollow brass tubing.

then paint and cover with grill cloth or not, or whatever.

That looks really cool, but isn't the real benefit of the sphere the internal enclosure?

[keep_hope_alive]

not the internal enclosure. the tweeter isn't vented into the cavity, the tweeter cavity is closed off. only a few tweeters on the market (Hertz Mille) allow you to remove the cavity to leave it open.

for an open back cone midrange, you need the cavity. you could do this with a dome midrange if you wanted (if it was large enough)

if you read the first page of this thread, you will understand why. it's all about eliminating the diffraction off of the tweeter baffle.

the B&W example is one where the shape is diffraction and cavity. but automotive tweeters aren't open. they have a cavity and a magnet on the back.

[keep_hope_alive]

and i have an awesome idea for mounting it to the apillar. i'll share the Hertz Mille tweeter sphere install for a 2005 Scion tC build. Slated for tomorrow morning.

[rugdnit]

I understand the diffraction part and have read the first page ( as well as the following pages ). I have also read that a sphere enclosure is ideal as well due to back wave reflections ( it was some time ago, so I don't have a link etc etc ).

[keep_hope_alive]

Originally Posted by rugdnit

I understand the diffraction part and have read the first page ( as well as the following pages ). I have also read that a sphere enclosure is ideal as well due to back wave reflections ( it was some time ago, so I don't have a link etc etc ).

Valid for a open back midrange or tweeter. These aren't open back.

These will benefit from more mass and no resonance. Thin walls resonate and you want that frequency to be well below your intended response.

[Eastman474]

So explain to me how you go about placement of the diffraction? Same theory as Gary Biggs regal right? With the flower looking diffraction ring?

[keep_hope_alive]

the sphere is merely reducing the baffle edge diffraction. you still have reflections and diffraction from the mount, the apillar edges, etc. you still have reflections that arrive delayed and cause phase interference (or comb filtering). you want to minimize all of that. recognize that anything 10dB below a signal is not adding to the signal - so if you could get all of your reflections 10dB below the original (direct) signal - you would essentially just have the original signal (ideally). aiming the tweeters so the window and windshield are off axis enough to attenuate those reflections is one method and how i plan on approaching this. absorbing those reflections is another method, but we can't make the glass absorptive. i am still concerned about reflections off the opposite window - giving the opposite ear too much information (left ear getting right channel information). that's natural in everyday life and our brain can handle it - but it uses those IID and ITD cues to determine source localization. essentially, that is what our goal is for imaging - using psychoacoustics to our advantage with non-ideal speaker placement.

this is what i love about car audio - it is so difficult and a great challenge. i mean, in a home you just buy Wilson Audio speakers and let the installer do the work... and acoustically treat the room.

[keep_hope_alive]

not totally familiar with Bigg's flower - if anything, he was trying to make the diffraction diffuse - break it up so many times that nothing was dominant. that would also distribute energy and possibly reduce the effect. a flower shape would do just that.

the sphere is trying to eliminate the phenomenon altogether. the thread references home audio and the Loudspeaker Design Cookbook. I saw that sphere diffraction study in there, but never thought about applying it to tweeters (where you don't rely on the sphere as a cavity). i am very appreciative to Patrick for bringing this to our attention. the length of this thread, the all positive and constructive responses, and the images make this one of the better threads on DIYMA (IMO).