I think that with my Thiel CS2.3s, the grills have some very small effect on the low-level detail in the music.
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In regards to Garfish's comment: yes, check the manual for the specific speakers. Someone with a pair of B&W Nautilus series; comfirm that B&W actually recommends removing the grills for serious listening. I can swear I read that when I was reviewing the manual at a dealer. I use to own a pair of the Matrix series, and those grills were designed to disperse the sound a certain way, so for the Matrix, they should be left on.
I've had the Forests for almost two years now. Couldn't imagine leaving them alone with the kids without the grills on. Nice that Totem puts the rigid mesh guard on the tweeters, huh? I also remove the grills for most critical listening, and have noticed a larger change in dispersion than anything else. The way Totem closely matched the opening and drivers (one opening, but really kinda teardrop-shaped once the tweeter and woofer circular cut-outs are joined),sound seems to beam a bit more with the grills in place. Effect is that of the drivers being recessed 3/4" into the baffle face. "Problem" is with the grill frame only. I have no doubt the fabric is fully transparent. Love the speaks though.Drive em with Stratos monos. Gotta get a real pre though.
The frame of the grill is probably the most offensive to the energy flow from speaker into room. Have you noticed that the high end speakers are getting more and more into rounded off edges, narrower cabinets, while some even slope from front to back.
Notice the tweeters of say the B&W Nautilus 801. It mounts on top of the cabinet and is tear drop shaped. It ain't just for looks, folks.
It is a continuation of the mounting the speakers as flush with the surface of the cabinet as possible.
I believe the manufacturers have to supply grill cloths strictly for marketing pruposes.
Someone mentioned that Vandersteen recommends leaving them on. Have you ever seen a Vandersteen naked? They are really ugly. And for all their good qualities at a reasonable price, a faily major criticism is the frame around the speakers supporting the grill causing diffraction of the small speakers.
According to Joseph D'Appolito ( and i quote ): "The grille is there only for cosmetic effect and to protect the drivers from prying fingers. The perfect grille is still the Holy Grail of speaker design". The article that he stated this in shows the performance of a speaker with and without the grille on. With the grille off, the response is very flat overall and almost resembles a perfectly straight line across the band. Simply adding the grille caused an increased variation of +1 and -3 dB's. That's a variance of 4 dB's total and a graph that looks choppy as can be above 1.5 Khz.
With that in mind, I have yet to see a grille that didn't:
1) create upper midrange / high frequency irregularities. This is due to what is known as "diffraction" and "nearfield reflections".
2) soften and slow high frequency transients. This is due to non-linear absorption characteristics, with higher absorption taking place as frequency rises.
Some grille's are obviously worse than others, depending on the materials used and their support structures. Since there is no such thing as "acoustically transparent" material, all grille's will alter the sound to some ( usually quite measurable ) extent. It is up to the end user to decide whether or not the grille's are beneficial or detrimental to performance within the confines of their system and personal preferences.
Since we are on the subject, metal "cages", "screens" or "lenses" over tweeters or mids can also create massive ringing and glare. I have yet to hear a speaker that didn't sound smoother after the "cage" was removed. Obviously, this WILL affect their radiation patterns also. Whether or not you want to do this with "little ones" around may be a different story though.
As far as i know, the folks that have done the most research in terms of grille effects were Acoustic Research ( AR ) and John Dunlavy. They both came out with very similar findings and designs at about the same time ( late 70's ).
Personally, i typically like to leave the grille's off when listening. If a recording is very bright, glaring or forward, putting the grille's back on can help tame this, but typically with other noticeable side effects. As such, i typically just deal with it. Sean
I like the way JM Lab Utopia series does it. the "speaker grilles" are actually solid wood "speaker protectors." They are to be put in place so that the maid can come through the room and clean things up without damaging the speakers. Of course, this would work well for women and children also. So, obviously, with these speakers you would remove the grilles for listening.
From the Thiel 1.5 manual:
"The grille on the CS1.5 is designed as an integral part of the system to reduce unwanted diffraction effects. Therefore, it must remain in place for proper operation. If you do need to remove the grille, pull the bottom of the grille frame away from the speaker an inch or so and then pull the top of the grille forward to remove it."
I have no speaker design knowledge but clearly Jim Thiel sees reason for the grilles. Not sure what that means though.
The Thiel CS1.5 grille is unique in that it actually has a sizeable rounded wood frame which gives the front of the speaker ALL of its anti-diffraction properties. In other words, without the grilles in place, the front of the speaker has no rounded corners at all. The Thiel CS2.3s are not like this and I'm sure that very few speaker grilles are designed this way. I never thought about it but the CS1.5 would be a good speaker to experiment with to see if the rounded shape actually makes an audible difference. I have my CS1.5s set up as my main speakers right now so I will try to do this experiment and post some results in the next day or two.
Well, this post got me into playing around with the grills on my speakers again. I still like what I hear better with them on. I suppose like everything, it depends on many factors, not just the speakers. I am now playing around with the grills on my speakers in my home office room while I'm here at the computer.
Many speaker designers will make accomodations for the effects of the grill cloth and will make the tweeter a bit "hotter" to compensate.
I don't think that there are any hard and fast rules. I've always found it best to just try it both ways and see what works best. Most sound better with the grills removed, but not always.
In a more direct answer to the original question regarding grills on the Totem Forest, I would recommend that you contact Totem. They are, however, obviously designed to be used sans the grills, so you'll have to guage how adverse the effect of leaving them on will be to your listening enjoyment. I had a pair of Aerial Model 5s which included grills but they are clearly an afterthought and are designed soley for the purpose of protecting the speakers when not listening (and perhaps appeasing significant others).
So Craig, you mean that Richard's grille material ISN'T acoustically transparent ? : )
Removing grille's will almost always increase apparent brightness along with the potential for added sibilance. In most cases though, the speakers actually measure flatter / more linear with the grille's off. Luckily, grille's are easy to take off and on ( with most speakers ) so that you can judge for yourself which way you want to listen to them. Sean
Back again. I did a late night listening comparison with my Thiel CS1.5s. Since I had to keep the volume down, I can't say much about the anti-diffraction properties of the grilles. (I'm really not sure I could ever evaluate those properties.) However, the speakers did sound better to me with the grilles off, more detail and spatial cues. I took a close look at the 1.5 and 2.3 grilles. I put them against a light and also did the "breath test." They look like they could have been designed better. It seems there could have been less grille material and more space for airflow. When blowing into the grilles, there is a good bit of resistance to airflow. I can't imagine that these grilles could possibly be "acoustically transparent." I suppose that more acoustically transparent grilles become less effective as dust covers and visual blocks.