speaker grills?

[fmw]

Thanks for a sensible post. It brings up two questions. Since anything put in front of a speaker will reflect some of the sound backwards into the speaker, one could make a case that any grille would suffer from some sonic anomalies. Whether it could be made audible or not is the issue. I've never been able to detect any difference from a grille in an objective listening test. I've never even had to change volume to match levels. I would bet that if you put enough material in front of the speaker you could change either the sound pressure level or the frequency response enough to be audible. I'm nopt sure why someone would do that but I see no reason that it wouldn't be possible. The question is how much reflection of sound back toward the speaker is necessary to change SPL or frequency response audibly?

The grilles have angled features designed, apparently, to reflect the sound in varying directions. Your image shows that. The question I would have is how much, if any, additional dispersion does it produce and is it objectively audible? I understand the marketability of it. I wonder what the manufacturer will say about the audibility of it. I also can't help wonder if the dispersion itself might be better without the grilles due the significant amount of material in these "wave guides." If you have an SPL meter, perhaps you could measure it.

 

[fmw]

I apologize. I didn't ask him if I could post his response so, if you don't mind, I won't share his name. I emailed a well known speaker designer not connected with Paradigm. This individual developed the speaker line for a well known high quality CE manufacturer. He is an EE and a 25 year member of AES. My question was:

A speaker company called Paradigm markets speaker systems that incorporate
> grille covers with "wave guides." They are angled features molded to
> create the frame for the grille and presumably improve dispersion of the
> sound.
>
> Since most speakers feature drivers that should provide good dispersion
> just from the shape of the cones or domes, it seems counterintuitive to me
> that adding an angled feature in front of the driver should have any
> effect on dispersion.
>
> My question is do you think there is any merit to this type of design
> feature? Also do you think it would produce an objectively audible
> difference from a traditional grille? Thanks for any comment you may wish
> to make.

Here is his response:

"The effectiveness of such a grille depends on size, shape etc. If the grille
is deep enough, it might accomplish a similar behavior to the old JBL horn
lens assembly. However, this was several inches deep to be effective and was
needed because the horns were very directional.

Normal dome tweeters, as you expect, are inherently very wide dispersion.

You should also consider marketing strategy as one of the reasons for the
grille.

I would ask for proof of improvement by measurement by an independent
testing company before buying such a system--ordinary grille VS wave guides.

Normally, grilles are in the way and should be as open as possible. In that
case, it could do more harm than good."

Hope it helps.

 

[Thaedium]

Still waiting on a response of any kind from Paradigm regarding the grills. In the mean time, I'm going to run by the local rat-shack and pick up an SPL meter tomorrow. I'll be away tomorrow and the weekend straight through to monday as I'm going down to Ft. Erie and doing some rememberance day parade things there with a friend and the local legion. When I get back, I'll send you some PM's FMW and I'll start a new thread with regards to generating actual data on this claim of paradigm's. Also, it'd be interesting to see if by next week they will provide some real data to prove the claim as well.

I suspect that due to the size of my room and the distance from the speakers themselves that there wont in fact be any measurable differences. Like I've said before, I've played the system with and without the grills and have been unable to notice any difference. Mind you, I've never taken it seriously enough to control all the variables that would go into the process of actually discerning a difference.

I'm curious, when I get the SPL meter back to my place next week, what are some suggestions you might have for establishing reliable data on this? I could also set up the system in an alternate location as well (My basement) to increase the listening area and duplicate all the tests to see if again there may be any difference.

I realize that for Paradigm, or any other speaker manufacturer they are probably testing all of these things in an anechoic chamber so they're data could very well be different. However, the real world consumer wont be listening to an A/V system in a perfect anechoic chamber, and thus will have to deal with the realities of a home environment. That said, I believe it would be interesting information to prove what kind of affect these grills have in an environment that is not anechoic. Or if they perhaps even hinder the drivers in a realistic listening environment.

Again, any comments or suggestions are welcome.

 

[highfihoney]

I suspect that due to the size of my room and the distance from the speakers themselves that there wont in fact be any measurable differences. Like I've said before, I've played the system with and without the grills and have been unable to notice any difference. Mind you, I've never taken it seriously enough to control all the variables that would go into the process of actually discerning a difference.

Again, any comments or suggestions are welcome.

I dont think the manufacturer is claiming there will be a difference in spl's from their statement,im pretty sure any change would be subtle & only picked up with a spectrum analyzer,i dont think an spl meter will show up anything where an analyzer will show subtle differences in response.

 

[fmw]

The purpose of the test would be to measure dispersion. You will need a CD with test tones. If you don't have one, I'll send you one. Pick a frequency that is right in the tweeter's range and sounds loud. Play the test tone and take SPL readings at different angles from the tweeter and measure the SPL at each point. Be sure the distance between the meter and the tweeter is the same for each measurement. You could tape a string to the top of the speaker cabinet, stretch it out and put the meter at the end of the string for each reading as you move across the test area.

Do the same test with and without the grilles. If the grille is effective it should have larger SPL readings at the corners of the test area or at the greatest angles from straight on when compared to the readings without the grille. If they don't, then the grille doesn't have a meaningful effect on dispersion and is nothing more than a marketing tool. If it does, then I will take back everything I said about lies. While a more sophisticated instrument might detect differences that the SPL meter can't detect, the meter is good enough to measure anything that is audible.

I'm assuming that you would get the same reading straight on with or without the grille to start the test but you better check that too to be sure you have a meaningful test. If there is a difference you will need to level-match the two legs (with and without) of the test.

You may want to do the same thing with any midrange drivers although dispersion normally isn't much of a problem with them. You can ignore the woofers because they have very little directionality. The tweeters are the main issue here.

And don't worry about moving your speakers. Take the measurements near field. - say 6 or 8 feet away from the enclosure. The measurements in your own listening room will be more meaningful to you than measurements made in an anechoic chamber.

 

[Thaedium]

Just got back from Ft. Erie. Also just recieved an E-mail from Paradigm regarding this issue. It was, as probably expected, not as useful as I had hoped.

Here goes:

Hello there, and thanks for taking the time to review this message. It seems to me that Paradigm takes a unique stance on grill covers, in that they affect the performance of the speakers. I've listened to my Studio 100 v.4's with them both on and off, and have been unable to note any differences. I was hoping that if possible someone could forward me some data that Paradigm has collected on their unique grills that can show an audible difference between the use or lack thereof?

That was my E-mail to Paradigm. And this was there response:

Hi

Since a good speaker disperse sound widely, its sound will also reflect and break up or diffract from the inside edge of a grille or the outer edges ofthe enclosure's front panel. This diffraction creates sonic interference which reduces accuracy. To achieve superior resolution, Paradigm Reference speakers are designed to eliminate diffraction. Grille frames fit flush to the drivers and have soft outer edges to ensure that the driver's output will not encounter reflective edges - diffraction is thus avoided.
Thanks for choosing Paradigm speakers.

Sincerely,

Gary Takeda
Paradigm Technical Support

So no data supporting this supposition really, just another claim stated a little bit more elaborately then the one made on Paradigm's webpage. He says they have "soft outer edges" - and I'm going to assume that hes refering to the fact that they are tapered to fit extremely close at the edges of the cabinet.

I'm going to make a trip Tuesday over to the local rat shack and pick up an SPL meter, and if you could send me that testing disc FMW that would be great. I'll mimic the procedure you've laid out, and provide pictures/data for each step in a new thread in the loudspeaker forum.

Thanks again.

 

[fmw]

OK, just PM me your address and I'll send you some test tones.

 

[Joe Schmoe]

My dilemma is that I like how my current speakers (Polk Monitor 50s) look without grills when they are turned off. When listening to them, however, all that silver is distracting. Putting the grills on/off repeatedly is too much trouble. For now, I am just leaving them on.

 

[Thaedium]

One little hang-up thus far, heh. I've searched from top to bottom in this small town and the one nearest to me, and I've been unable to find an SPL meter anywhere. Kinda silly really. The guy in The Source had no idea of what it even was. I went on to a car audio shop near to mall where The Source was and he had no clue as to what it was... kinda funny that. Came back to my small neck of the woods and talked to a guy who does primarily car audio, and is looking to expand into home audio/video. Had a good conversation with him, but he just didn't sell it. He said that for most of the competitions they host there they have the guys bring their own equipment. Funny since most of them are probably buying from him?

So I'm just going to have to take a look online and order one in. Any recommendations?

 

[fmw]

http://www.action-electronics.com/dbmeter.htm#Economical

has a couple. Just put sound pressure meter or db meter into your search engine.