Tweeter Diffraction

Noting posts made on the Trade section of the forum, I was intrigued by the idea of tweeter/baffle interaction (tweeter diffraction).

Today I spotted self adhesive felt on sale at Tesco - I bought a couple of packs (@ £2.00 a pack - the stuff is sold as furniture feet).

Having cut the larger pieces of felt to size and fitted them around my HF drivers, and noting a major difference (note difference, not improvement), I decided to remove the large felt pieces from my speaker baffles and apply some of the multitude of dots in the felt packs.

I like what I'm hearing so far - longer term listening will prove whether or not I persist with this line of experimentation.

I'll do photos if there is a demand.

All I suggest is give it a go.

Chris:)

Definitely try Jim's product out, I did and it transformed my system (note: improvement not just difference ;)) so I can thoroughly recommend it. It costs pennies too.

Ditto Rob, improvement not difference. Other people have had varying degrees of success with this line of tweakery, it is speaker dependant. I would recommend Jim's surrounds as he has put in a large degree of R&D & has received tons of feedback. It is cheap, and there is a money back trial period. Try them compared to your efforts - it would be interesting to see how they match up and I for one would be interested in your thoughts.

From the Grave

I thought some folks might be interested to hear how Chris got on with these pads - did he keep them on?
Has anyone else tried something similar?

I have a felt-type ring around my tweeters. I like the sound with it on.
Also have another set of speaker with the baffle covered with leather - slight differences before and after the leather.

In speaker building the baffle design is one of the most important aspects. This includes driver placement, depth of each unit and even the material the baffle is covered with. All this impact on the final sound and can give measurable results.
Also, you can try with something less dense similar to velvet with double sided tape - choose one that comes off easy :D

Many years ago I tried foam around my tweeters and preferred it. A few years later I changed it to a slightly thinner, grey, version (about 8mm) that also goes around the mid/bass driver (it's held on with double sided tape) - this definitely makes a worthwhile improvement.

I didn't buy these solutions though - I made them myself.

I used this in past with standard speakers and made a difference to long term but not look great Do not need them with speaker design I have now

I used these Focus Rings on my previous JM Lab Mezzo Utopia speakers and it made a useful improvement to treble quality, purity and soundstage.

http://www.russandrews.com/product.a...CVCKNYNWOQNYJF

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Originally Posted by Stratmangler

Noting posts made on the Trade section of the forum, I was intrigued by the idea of tweeter/baffle interaction (tweeter diffraction).

Today I spotted self adhesive felt on sale at Tesco - I bought a couple of packs (@ £2.00 a pack - the stuff is sold as furniture feet).

Having cut the larger pieces of felt to size and fitted them around my HF drivers, and noting a major difference (note difference, not improvement), I decided to remove the large felt pieces from my speaker baffles and apply some of the multitude of dots in the felt packs.

I like what I'm hearing so far - longer term listening will prove whether or not I persist with this line of experimentation.

I'll do photos if there is a demand.

All I suggest is give it a go.

Chris:)

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Have you got a link to the article in Trade.

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Originally Posted by The Grand Wazoo

From the Grave

I thought some folks might be interested to hear how Chris got on with these pads - did he keep them on?
Has anyone else tried something similar?

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No, eventually the pads were removed.
The pads had a definite effect on sound dispersal, but after a couple of weeks I decided to remove them.
And I didn't miss their effect, so they stayed off.

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Originally Posted by Puffin

Have you got a link to the article in Trade.

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I can't remember which article it was, but it must have been from one of these threads http://theartofsound.net/forum/searc...earchid=795249

Thanks Strat. I can't get the link to work. Do you know the name of the commercial product? Someone called Jim?

rob.

They certainly do what they are designed for but i didnt like them.

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Originally Posted by Puffin

Thanks Strat. I can't get the link to work. Do you know the name of the commercial product? Someone called Jim?

rob.

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http://www.diffractionbegone.com/

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Originally Posted by Stratmangler

http://www.diffractionbegone.com/

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Cheers.

I don't think they need to be as thick, or as dense, as the commercially available ones.

http://i62.photobucket.com/albums/h9...groupedpic.jpg

You can make your own very neatly.

(sorry about the rather low-res pic)

Whats those on the side of your Epos cabs Mark?

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Originally Posted by YNWaN

http://i62.photobucket.com/albums/h9...groupedpic.jpg

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Kind of reminds me of the Acoustic Blanket used on the early Acoustic Research loudspeakers, though as you point out - not as thick ;)

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Originally Posted by Puffin

Have you got a link to the article in Trade.

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Jim made quite a few posts but this was the first one that talked about his products, I think.

http://theartofsound.net/forum/showthread.php?t=38

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Originally Posted by Andre

Whats those on the side of your Epos cabs Mark?

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They are clad with a particularly high fired porcelain tile. In this case the tile is not glazed at all (it is post production polished - like stone). The whole thing is the same colour, and material, all the way through. It is fired to a very high temperature that essentially vitrifies the material and results in an extremely stiff ceramic panel. It has been glued to the sides with a particular flexible adhesive intended for use where wooden flexible floors must be tiled. Essentially, their application creates a constrained layer structure. The flash makes them look quite a bit paler than they really are (they look nearly black in real life). They had to be cut with a diamond saw and the edges were polished by a local company that makes mirrors.

I like treble diffraction myself. I have no idea why you would want to reduce it.

Having the treble beam cleanly at your head is fantastic for imaging but sod all use for anything else. And as imaging is a largely artificial effect rarely found in real life, why would you want to improve it?

Have you ever hit a cymbal in real life? It's not a very directional sound. Real instruments send sound cascading in all directions, reflecting off every surrounding surface to fill the room with vibrant noise. The more directional a speaker is, the less it sounds like real life.

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Originally Posted by Mr Pig

And as imaging is a largely artificial effect rarely found in real life, why would you want to improve it?

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You must be listening to Linn speakers, then ;)

The purpose isn't to cause the treble to 'beam directly at your head'; the treble drivers natural dispersion pattern isn't effected. The purpose is to stop the edges of the cabinet (and things like bolt heads) acting like secondary radiation points.

Imagery isn't 'largely artificial', it is entirely artificial and carefully constructed in the recording studio or/and when the microphones are placed.

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Originally Posted by YNWaN

The purpose is to stop the edges of the cabinet (and things like bolt heads) acting like secondary radiation points.

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I know. Unless you modify the actual tweeter you're obviously not going to alter the dispersal characteristics of the unit itself. But you are altering the treble dispersal characteristics of the loudspeaker? Which is effectively the same thing. And by reducing secondary reflections you are making the treble more directional.

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Imagery isn't 'largely artificial', it is entirely artificial and carefully constructed in the recording studio or/and when the microphones are placed.

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I wouldn't say it's 100% artificial, mostly though. Certainly massively exaggerated.

If you listen to live music, whether it is a band in a pub, stadium rock concert, orchestra or solo artist playing unplugged, you will find that the tight 'holographic' imaging effect that a Hi-Fi system can create relatively easily does not exist in real life. At the most you get a vague idea of where something is but that that's it.

The best imaging speakers are the most directional ones. Turning them to point straight at your head will improve the effect dramatically. Cutting down on secondary reflections will help too but don't think you're creating a more lifelike sound.

Real life is awash with secondary reflections! Think about how many bits of the drum kit the sound from your cymbal is going to reflect off. Not to mention the other things around the kit. It's a vibrant, room-filling cacophony. And you're worried about a couple of screws on the tweeters? ;0)

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Originally Posted by Mr Pig

If you listen to live music, whether it is a band in a pub, stadium rock concert, orchestra or solo artist playing unplugged, you will find that the tight 'holographic' imaging effect that a Hi-Fi system can create relatively easily does not exist in real life. At the most you get a vague idea of where something is but that that's it.

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I listen to lots of live music, but only classical counts for this exercise (rock music is usually way too loud, in a poor acoustic venue and fired from all sorts of speaker stacks). I have closed my eyes in a centre stalls location in the Festival Hall and could pinpoint with pretty good accuracy where an instrument is located within the orchestra. It is this which I seek to reproduce although I do agree with you that modern music imaging is very hit and miss.

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Originally Posted by MartinT

I have closed my eyes in a centre stalls location in the Festival Hall and could pinpoint with pretty good accuracy where an instrument is located within the orchestra.

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Is it mostly classical music that you listen to? I very rarely listen to it myself, I find the odd piece spellbinding but mostly too drawn out.

Even in the situation you describe though the imaging information present is not as good as a Hi-Fi can manage, I've been in similar situations.

I'm not saying that imaging is evil! Not at all. My system happens to image quite well, the key word being happens. From my experience, when you try to do things to deliberately enhance imaging the coherence and life of the music suffers.

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Originally Posted by Mr Pig

I'm not saying that imaging is evil! Not at all. My system happens to image quite well, the key word being happens. From my experience, when you try to do things to deliberately enhance imaging the coherence and life of the music suffers.

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Ah, now we're on the same page. I certainly wouldn't want to sacrifice coherence for imaging. For me it's a matter of getting the speaker spacing and toe-in right and reducing reflections. I like a fairly dead room and have my TubeTraps set for maximum absorption. This seems naturally to enhance coherence and imaging, so twice the bang for buck.

P.S. I listen to a fairly eclectic mix of music, with about the same proportion of rock and classical.

It can do but is not always the case.

The foam grills fitted to Linn and Naim speakers effectively do the same job (except on them a small amount of foam still exists in front of the drivers) - hence both of these manufacturers recommend that the grills are left in place.

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Originally Posted by YNWaN

The foam grills fitted to Linn and Naim speakers effectively do the same job

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Interesting. I've always thought the opposite.

I've always thought that speaker grilles reduce treble output and increase dispersal. That's just based on my general experience with grilles on speakers.

How can the foam grilles on Linn speakers be dense enough to stop reflection when they are transparent enough to allow most of the energy through? The materials used to stop reflection are typically much thicker. I can see how that might be part of the story though as the foam would be effectively denser at a more oblique angle.

With the grilles on, speakers are less directional. There is less of a 'sweet spot' suggesting to me that the grilles spread and break up the treble. I have always preferred speakers with the grilles on and not toed in. My experience equates both of these traits with better treble dispersal, better coherence and poorer imaging.

Don't those tube traps work primarily at low frequencies?

I like a sort of 'medium' room, I like to keep a bit of reflection to add to the 'live' feel. A lot of that sort of thing is equipment dependant though, how bright your kit is.

I'm not sure you understand what secondary radiation of high frequencies consists of. Any sharp edge (usually the cabinet edge) will act as a point of secondary radiation - this is not a good feature and can only serve to colour the natural output of the drive unit - it does not improve the treble drivers dispersion (except in a delayed and chaotic manner). You can't increase a drivers dispersion by putting foam in front of it - you can alter the dispersion significantly by adding a horn loading element, but that is another issue entirely.

The Linn speakers have a few millimetres of open cell foam in front of them but there are quite a few inches before the edge of the cabinet is reached.

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Originally Posted by YNWaN

The Linn speakers have a few millimetres of open cell foam in front of them but there are quite a few inches before the edge of the cabinet is reached.

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Yes, I get what you're saying now and it makes sense.

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Any sharp edge will act as a point of secondary radiation - this is not good and can only serve to colour the drive unit - it does not improve dispersion (except in a delayed and chaotic manner).

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I think a bit of chaos might be a good thing!

If you go back to live sound. The secondary radiation you are talking about applies in spades to the sound coming from life instruments. As I said about the drum kit but it applies to pretty much all music. You wouldn't sit metal poles and bars in front of your speakers but an orchestra is full of music stands, apparently without the sound of the orchestra falling apart!

The 'secondary radiation' that you're talking about coming off the edge of a speaker cabinet is nothing relative to the reflected sound found in live music situations. But that's not even the point. The point is whether it is a good thing or a bad thing, and I don't think that's as dried as you suggest.