[John Casler]

I plan to build two long piece of black marble tile with dimension of 22" x 12".  ...

I might offer a few suggestions and ideas.

1) while marble and metals can resonate or ring, the frequencies that will be "directed" by this tweak are higher than the resonate frequency of marble. so it can be effective

2) While it is more attractive to make the "director"  the same width as the RM40, I have found that a "wider director" is even more effective at both harvesting and directing the upper bass energy and blocking ceiling reflection of the upper woofer.  It can be up to 4-6 inches wider on "each side" than the speaker.

3) I have located a premade "shelf" from PolyCrystal which is rather attractive and is 24" x 15" x 1.5" (weighs 24#) and is very good for the purpose (I also use it for a "beard" for the 626Rs sometimes by simply propping it up to the bottom of the 626.

4) My next experiment (but first I have to "get" another pair of RM40s is to use a director that not only has a 4-8" lip on top, but also has the same thing on the sides, down to about the phase plug level of the woofer.  Kind of a "bonnet" (as much as I dislike that word)

This would harvest even more of that midbass impact and direct it to you without having any downside since it is so close to the drive.  It is almost like a "horn enclosure" for the woofer, without the bottom section.

A mock up could be easily made by taping 3 old record albums or laser discs together.  Maybe even heavy stiff cardboard would work, but I think MDF or something solid would be better.

I won't be able to report results for some time, but if anyone wants to try it, I hope my explanation was sufficient.

You may have to experiment with the side director section since making it too long might add a 'honkiness".  I would think that 4-5 inches might be maximum, but won't know until I play with it.

As always it may "not" have an aesthetic appeal visually, but the sonic result "should be" more than interesting.

[tkp]

I am thinking of getting the chopping board from Ikea and paint them black.  It would be great if my pair of RM40s are in maple because I don't have to do any painting at all.

http://www.ikea-usa.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10101&storeId=12&productId=10269&langId=-1&parentCats=10108*10216


http://www.ikea-usa.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10101&storeId=12&productId=15241&langId=-1&parentCats=10108*10216

[Marbles]

I'm having a cabinet maker friend make some directors with sides from .75" oak veneered MDF.

These will be 12 5/8 " wide for the top, 22" long for top and sides, and the sides will come down 10.5" from the top.  This will bring the sides to the bottom of the midwoofer.

I should have them in about a week.  Cost is $100.  It would be easy to make yourself with a sheet of .75 MDF for around $50.

I'll let you know how it works when I get them.

[zybar]

Marbles,

Please take pics and post.

Thanks,

George

[Marbles]

Will do:

When I first get them, they will be in natural unfinished oak and should stand out against the black speakers.  Once I'm sure that the size is right, I will finish them in gloss black to match the speakers.

Pictures will happen in about a week when I get the directors.

[tkp]

Marbles,

Do you plan to cover both sides of the speaker cabinet or just the outside side?  or will you play with both before making the final piece?

[JoshK]

I have some @25lb/ea near 2" thick acrylic pieces that I use for 'sonic directors' from time to time.  The pieces are large and heavy and acrylic has a good resonance property.  I have played around a bit and certainly the mid bass is helped some by this tweak.

Granted, I listen in near field primarily so maybe the effect is not quite the same as that with which John Casler had in mind.  However, I have noticed what seems to be some effects on the overall frequency spectrum, not all of which were good.  I am not solely alone in my dicernment, as I let the NY Audio Rave test it out and give me feedback at the meet at my place last Oct.   Some noticed some not so great effects as well. I won't bias you all with what I have found, and I haven't yet tested whether some/all of this can be overcome by playing with the pots, but as is I am not solely a fan of this tweak, I would have mixed feelings.  

Let me know if any of you find any ill, or maybe just differing, effects in your listenings.  I certainly didn't find it right away, although a couple of the audio fellows did at my meet.

[Marbles]

TKP,

I planned to do both sides.

Right now I'm playing with a mock up..it is the doors I took off an old RPTV.  Each door is hinged.  They are about 33" long x 10" for each top, and 10" for one side for each speaker.  Currently I have them set up for the outsides.

I am on my first CD, Jack Johnson - On and On.  Every once in a while it seems I can localize the midbass to the drivers and not the soundstage, but the directors are out 6" from the baffle.

I figure if it begins to localize I can move them back to where I still get some midbass reinforcement, but not the localization..that's the plan anyway.

[tkp]

JoshK,

You are not alone on this one.  I have been playing with the length of the extended piece and it is depending on recording.  This was one of the reason why I put several lines on the tile so I can go back and forth to check on the effect.  I will continue to play with the tile for a few more weeks before I decide to build some thing nice.  Another factor to consider is the room size and type of flooring.  The first floor in my house is appoximately 1400 squared feet with 9ft ceiling.  My listening position is roughly 9ft from the center point of the two speakers and the speakers are placed roughly 6ft apart.

Where did you get the 2" thick arcrylic boards?

[Marbles]

OK, I'm playing a much more familiar recording, Supertramp - Classic Hits.

I don't like the way the side directors muck with the soundstage.  They make it sound closed in and not "open".

Therefore I won't be getting any side blinders on my directors.  They will just be 12.5" X 21" x .75" solid oak with radiused corners.  Cost will be $40 unfinished for the pair.

For those keeping track at home, I'm about 11' from the center of the speakers and they are about 7' apart

[John Casler]

I have some @25lb/ea near 2" thick acrylic pieces that I use for 'sonic directors' from time to time.  The pieces are large and heavy and acrylic has a good resonance property.  I have played around a bit and certainly the mid bass is helped some by this tweak.

Granted, I listen in near field primarily so maybe the effect is not quite the same as that with which John Casler had in mind.  However, I have noticed what seems to be some effects on the overall frequency spectrum, not all of which were good.   ...

Hi Josh,

Actually when I developed the tweak it was "for" nearfeild, since the closer you sit the steeper the angle of integration for the upper woofer.

The great thing about it is that it can be "tried" quite simply by placing a MDF shelf or any board that offers the right size.

Most of my listening was done with MDF boards of various sizes and thicknesses.

The primary concept is two fold:

1) to reduce the ceiling bounce of mid and upper bass frequencies

2) to channel or direct (like a horn) the energy more toward the listener

I never had to "retune" anything in the speaker and only noticed that the upper outer edges of the soundstage "filled in", the upper bass became more energetic and impactful, and the sound was cleaner (no doubt from reduced ceiling reflection)

These impressions were from using anywhere from 4" - 6" overhang.  More overhang seemed to offer too much of something. (maybe it was begining to reflect the upper neopanel)

I have thought too, that actually a curved "brim" type device might be more effective to more evenly direct the sound waves as they are produced and delivered that way (actually they are more like a series of huge bubbles of ever expanding sonic energy, as they move away from the driver)

Smoothly directing that energy (to you) is the goal with as little disturbance as possible.  Disturbing or distorting the wave is to be avoided.  That may be why much more than 6" might sound "off".

The whole "tweak" actually grew out of my placing a large piece of acoutstic foam on top of the RM40 to "reduce ceiling reflections".

From there I placed a board on to of the foam to kind of hold it in place.

Immediatly I noticed an upper bass improvement, and then removed the foam and just used the board.

Some may want to experiment with the foam too and see what the two sounded like.

I have an idea for another version of this tweak, along the lines of what I said above, but since I probably wont have any RM40s for at least 45-60 days, it will have to wait, but I think it will be "much" better, and Kinder to the soundwave.

[JoshK]

I have tried various lengths.  A couple inches (@2") didn't have much effect overall, either good or bad.  >6" was best in the impact and fullness of lower mids, 4-6" was best overall but there was a distinct disadvantage as well.   I have another tweak to try that is a little more theoretically justified, so I think, and may have the same benefit but a different set of disadvantages (or none, we'll see).  

I haven't had time yet with studying, but when I move into my new place I'll try it out and report back.   I was just wondering if others heard any ill effects to this tweak or if it was just me.

[Corbin Johnson]

I applied the Elmers glue to both sides of the PR's of my RM40's and Larger sub.  I noticed a small improvement on the 40's but a significant improvement on the sub.  The bass is much tighter and cleaner.  I like it so much, I think I'll add another coat this weekend.

[ScottMayo]

Elmer's glue is water soluable, and it can soften in humid conditions. That doesn't matter much in carpentry, where most of the glue isn't exposed to air, and where a little flexibility and softness can be a good thing. But I wonder if it could matter here? Anyone doing this tweak, please remember to post long term results, too! If the thin layer of glue slowly shifts over time - and if it's damp and kept vibrating, it could in theory - you could end up with an uneven coating, and uneven flexing, which would probably cause some subtle but bizarre sonic artifacts - and with no way to fix them. And even if the glue can't "slide", it raises the question of bass that sounds different on damp days...

Brian, have you experimented with spray-on acrylic clear-coat? (I'm *not* recommending people try this on their home systems. I've never done it myself.)

The low-midrange driver on my old Infinities is coated with some sort of damping/stiffening agent. I don't know what they used, but I wish I did. It's held up and stayed uniform for 20+ years.

Speaking of which... what is VMPS's position on tweaks? Let's say Brian blesses wood glue, and I carefully paint woofers on my (maybe soon to be ordered) Elixirs. And I listen to the results and I conclude I've just ruined the sound. Do I get to pay for 6 new woofers? Will I have to lock myself in a closet and chant "don't believe everything you read on the internet" for six hours as penance? (If I drop thousands on speakers and then ruin them with glue, I'm going to have WAF issues like you cannot imagine...)

[JoshK]

Scott...just for clarity, that would be two passives, not 6 woofers.  You don't add glue to the active woofers, just the passives.

Maybe I should try AquaNet hairspray.    Or how about gelatin? That is what glen plake use to use to keep his hair up while jumping off cliffs.

[Marbles]

Scott, the glue will now be standard on the passives, so you won't have to do that one

For other tweaks, I try to not do irreversable tweaks until there is overwheming evidence it only has positive effects or I can easily live with a minor subtle negative.

If I had the RM/X's, I would check with Big B before I did any tweak to get his opinion.

[ScottMayo]

Scott, the glue will now be standard on the passives

Passives. *sigh* I don't know how I missed that before. Never mind. This isn't as scary as smearing glue on the actives.

[Tim S]

I put a coat of glue on my RM 1's last night (will check the sound tonight). One question about it. People are saying they are putting coats on both sides. I couldn't get the PR's out of the box. I unscrewed them and tried to pull them out but they were pretty solidly in. I then took one of the woofers out and tried to push, but that didn't help. I was a bit scared to put real force behind it to really push them out. So two questions:

1. Should I really worry about coating both sides?

2. Is it ok to push strongly enough to pop them out or is there another way to do it?

Tim

[Brian Cheney]

PR's can be pryed out with a flatblade screwdriver.  The gasket tape holds them in place.  Once you break that seal they come out easily.

[Tim S]

Ok. When I put them back in do I need to do anything special to re-seal them or just make sure to screw them down tight?

Thanks.
Tim