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Author Topic: Grill on N802 tweeter......on or off?  (Read 5586 times)

jazzius

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Grill on N802 tweeter......on or off?
« on: June 10, 2004, 04:56:31 pm »

I realized today that it's easy to remove the tweeter grill off my N802's......it seemed to sound better to me.....but according to the 802 manual, it should sound better with the grill on.....are they just saying this to protect our speakers from greasy little fingers?.....otherwise, why would they make the grill so easy to remove?

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Re: Grill on N802 tweeter......on or off?
« Reply #1 on: June 10, 2004, 08:50:25 pm »

I beleve the loudspeakers were "voiced" with the grills on. If removing the screen over the tweeter helps you achieve a better overall translation of your work, by all means, do what you are comfortable with. On the other hand, the distance of the screen material to the dome surface will cause a very slight reflection amongst the lowest frequencies near the crossover point. This reflection gives a slight rise to the output close to said crossover frequency and also provides some acoustic dampning. you may find the transistion from the mid to the tweeter to be lightly 'tainted' with the screens off.

I have done much experimentation with tweeter screens of various types and perforations over the years. In most cases, the output near the crossover frequency and slightly below is accentuated at the level of close to 1dB. At the crossover frequencies is where most of the critical measurements are done with precision loudspeaker systems in phase and amplitude. This is where the loudspeaker manufacture does the most critical voicing of the loudspeakers both acoustically and in the crossover.
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jazzius

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Re: Grill on N802 tweeter......on or off?
« Reply #2 on: June 10, 2004, 09:32:18 pm »

Thanks Bill.....actually the difference was very subtle, and could have been in the realms of confirmation bias.......but it seemed to me that with grills off it was a bit less veiled with a slight top end lift.....maybe also slightly less distortion....i'll try again tomorrow.

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Re: Grill on N802 tweeter......on or off?
« Reply #3 on: June 10, 2004, 09:41:41 pm »

A difference will be there...however, you must judge if overall you like it better. I have found that by adding transparency...you may end up making your mixes less transparent. Be careful and see what works best for you. Modding loudspeakers is a tricky business...especially acoustic modifications.


The slight reduction of the lower frequency content is allowing the top to come through more as well and the absence  of the blocking tendencies. Higher dampning also reduces the extreme top which the screen does do.


One thing to realize is that the frequencies above 9K typically only emulate from the very center and tip of the dome where as lower frequencies move it as a piston. Above 20k, they are less than a few degrees , like laser beams, the dispersion.


If you can purchase a few of these screens, you would find that a 3/8 hole in the center of it may give you the best of both worlds. Some manufactures actually put a piece of felt where that hole would be(!) to make domes behave better with the phase changes as frequencies increase.

Smile  
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jazzius

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Re: Grill on N802 tweeter......on or off?
« Reply #4 on: June 10, 2004, 10:07:20 pm »

I'm sure there are differences....they're just hard to pin-point....it's easy to convince yourself that the sound is less velied when you have the visual clue of an unveiled tweeter....i'm sure B&W know best.....but i'm also sure the grill wasn't put there primarily for the sound....ho-hum

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Re: Grill on N802 tweeter......on or off?
« Reply #5 on: June 10, 2004, 10:10:40 pm »

I feel certain that the grill is a protector..but I also feel certain that critical decisions in the voicing of the crossover network were made to compensate for the grill.
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jazzius

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Re: Grill on N802 tweeter......on or off?
« Reply #6 on: June 10, 2004, 10:17:42 pm »

thanks, Bill. Very useful info!

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Re: Grill on N802 tweeter......on or off?
« Reply #7 on: June 10, 2004, 10:36:23 pm »

You are certainly welcomed. I know it is late there in the big Amsterdam...do you have any good pics you want to share of your set-up?

Loudspeaker design and consulting is my first love. Since 1972 actually as a teen. I had some ideas and a few manufactures then would "try anything", namely JBL. We had access to so many raw drivers and a nice cabinet shop, building and evaluating dividing networks was always fun. To stay on top of that game, one must practice quite a bit. I lost my calling for it around 1998 and since this studio living is past 20 years,(getting closer to 30) their is simply little time to indulge like I used to.

I was also very fond of KEF loudspeakers. the 104.2's were very articulate but needed gobs of power.



I have used the 802's many times when I travel to other facilities to lend a hand. They do a real nice job of letting you evaluate the overall presentation.
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grock5

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Re: Grill on N802 tweeter......on or off?
« Reply #8 on: June 11, 2004, 01:43:20 am »

The grill is there to protect the tweeter. The tweeter is probably fairly sensitive. The last thing you want is debris on the tweeter. Then the sound will be "veiled".

If you really feel like taking apart your speakers, try taking one of the bass woofers out. The inside of the N802 cabinet is a beautiful thing...

- Gary


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bblackwood

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Re: Grill on N802 tweeter......on or off?
« Reply #9 on: June 11, 2004, 03:45:29 pm »

jazzius wrote on Thu, 10 June 2004 20:32

it seemed to me that with grills off it was a bit less veiled with a slight top end lift.....maybe also slightly less distortion....i'll try again tomorrow.

What did you find out?

I would venture that if it sounds like there's more top end ('top end lift') that you're probably hearing an increase in distortion. These guys (B&W) certainly know how to make things work to their benefit...
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barefoot

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Re: Grill on N802 tweeter......on or off?
« Reply #10 on: June 11, 2004, 05:56:31 pm »

A grill is always going to degrade the driver performance somewhat.  It will slightly flex and resonate.  It will also decrease the efficiency a little, resulting in higher distortion for a given output level.  It's slight, but definitely a compromise for the sake of protecting the dome.  

This being said, however, it's a very good bet that B&W designed the 802 with the grill in place.  Besides reducing the efficiency, that grill probably also increases the tweeter damping since it's so close to the dome.   So, if you remove the grill, you're likely to have a tweeter that is slightly too loud and slightly under damped.  I've never removed one, but it looks like you might also change the shape of the tweeter rim.  This will most definitely alter the response.   Best to leave it on.

Thomas
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jazzius

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Re: Grill on N802 tweeter......on or off?
« Reply #11 on: June 12, 2004, 03:53:58 am »

Thomas, thanks.
Brad, I didn't get much further then before.....too subtle to say anything concrete.....as people occasionally wander behind my console Shocked when i'm out of the room, i think i'll leave the grill on.  

davidc

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Re: Grill on N802 tweeter......on or off?
« Reply #12 on: June 12, 2004, 05:14:52 am »

jazzius wrote on Sat, 12 June 2004 08:53

Thomas, thanks.
Brad, I didn't get much further then before.....too subtle to say anything concrete


I doubt very much if taking the grills of will adversely effect the sound, and in my experience any metal grill in front of a loudspeaker is going to have a negative effect, due to reflections and vibration. On every speaker I have heard with a metal dome tweeter, they have always sounded better without the grill.

The effect of taking the grill off should not effect the freq response, it has more to do with dispersion and distortion.

If you do take the grills off, and you touch the domes you will likely need a new tweeter. they are as fragile as tin foil.

Quote:


as people occasionally wander behind my console Shocked when i'm out of the room, i think i'll leave the grill on.



I hate it when people do that, and it is often the first place that people go when they walk in the studio.

Best Regards

David C
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barefoot

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Re: Grill on N802 tweeter......on or off?
« Reply #13 on: June 12, 2004, 03:13:04 pm »

davidc wrote on Sat, 12 June 2004 02:14

The effect of taking the grill off should not effect the freq response, it has more to do with dispersion and distortion.

And dispersion doesn't affect the response?  Of course it does.  If you make the tweeter more or less directional in a given bandwidth it will alter the on-axis response in that bandwidth.  And the shape of the bezel surrounding the dome has a very significant impact in the dispersion characteristics.  Furthermore, even the most open perforated mesh materials are only about 80% open area.   This alone translates into potential 2dB frequency dependent response variations.  

Thomas
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Thomas Barefoot
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barefoot

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Re: Grill on N802 tweeter......on or off?
« Reply #14 on: June 12, 2004, 03:36:00 pm »

Quote from page 2 of the 802 users manual:

"... the grille retaining ring is designed to provide the optimum acoustic environment for the unit and the response is less smooth with the grille removed."  


Seems clear enough. The only concession it appears they made to the layman was the substitution of the word "environment" in place of "loading".

Thomas
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davidc

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Re: Grill on N802 tweeter......on or off?
« Reply #15 on: June 12, 2004, 06:18:30 pm »

So What your saying Thomas is that Jazzius is deaf? I mean he should be able to hear a 2db change in the response.

I have not done it with an N802, but every metal dome I have heard, the difference with the metal dome off is subtle.

Best Regards

David
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jazzius

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Re: Grill on N802 tweeter......on or off?
« Reply #16 on: June 13, 2004, 05:18:07 pm »

deaf, no, but hard of hearing, perhaps.... Very Happy

barefoot

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Re: Grill on N802 tweeter......on or off?
« Reply #17 on: June 14, 2004, 02:53:28 pm »

davidc wrote on Sat, 12 June 2004 15:18

So What your saying Thomas is that Jazzius is deaf? I mean he should be able to hear a 2db change in the response.

I have not done it with an N802, but every metal dome I have heard, the difference with the metal dome off is subtle.

You are free to do and hear what you want, but please don't put words in my mouth.  I didn't call anyone's abilities into question.

I'm just a speaker designer trying to shed some light on the subject.  The very talented designers at B&W, the ones who actually designed the 802, back up my statements in the manual.  

Thomas

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