Post by: jazzius on June 10, 2004, 04:56:31 PM
Post by: Level on June 10, 2004, 08:50:25 PM
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.
Post by: jazzius on June 10, 2004, 09:32:18 PM
Post by: Level on June 10, 2004, 09:41:41 PM
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.
Post by: jazzius on June 10, 2004, 10:07:20 PM
Post by: Level on June 10, 2004, 10:10:40 PM
Post by: jazzius on June 10, 2004, 10:17:42 PM
Post by: Level on June 10, 2004, 10:36:23 PM
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.
Post by: grock5 on June 11, 2004, 01:43:20 AM
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
Post by: bblackwood 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...
Post by: barefoot on June 11, 2004, 05:56:31 PM
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
Post by: jazzius on June 12, 2004, 03:53:58 AM
Brad, I didn't get much further then before.....too subtle to say anything concrete.....as people occasionally wander behind my console
when i'm out of the room, i think i'll leave the grill on.
Post by: davidc 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 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
Post by: barefoot 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
Post by: barefoot on June 12, 2004, 03:36:00 PM
"... 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
Post by: davidc on June 12, 2004, 06:18:30 PM
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
Post by: jazzius on June 13, 2004, 05:18:07 PM
Post by: barefoot 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