Soffit mount, don't know which design to choose

Pasz · **Posted:** Tue Nov 15, 2005 6:37 pm

The first design has a front completely made out of MDF. the second has a bass trap in the middle. If the second design is better, should I make it a helmholtz resonator or a simple deep bass trap?

I should mention there's a lot of trapping in the back of the room.

Furthermore I will probably soffit Dynaudio BM6A's. These are rear ported and have amps. Must I add ports at the top and and bottom of the soffit?

giles117 · **Posted:** Tue Nov 15, 2005 8:36 pm

Based on your room Depth I'd Go with Design #2 and make it a Bass Trap.

I would add resonators to the side... If feasible. based on the location of your window and door it might not be feasibe. I am of course assuming this is an accurate representation of your room.

Pasz · **Posted:** Wed Nov 16, 2005 1:30 am

Yes, it's a very accurate drawing.

My intuition says the second one is better, too!

About the rest (a bit off topic on this speakers forum):

I rather not cover up my window permanently

.

It's an outside window. Doesn't bass travel through the window anyway (making it a perfect bass trap) and shouldn't I be worried about mid/high freq's reflected of that window?

Maybe I can make a simple removable panel for it which I can put there when doing serious mixing.

There's a hall behind that door. It's a wooden paneled door. I think the panels are pretty thin, maybe 1 cm or even less. Same as with the windows: Maybe the low freqs pass through it and get "lost" in the hall. Maybe just mid/high absorption is enough for that door? Can't make it too thick anyway. I have to be able to open the door

.

Byan, I know you soffit mounted your Mackies, which like BM6A's are rear ported and have amps (which heats up). I read you installed a big fan to cool it. I'm wondering if you have ports at the bottom and/or top of the wall.

About the bezel: Is it better to make as high as the room, or should I make (for instance) the top of the soffit wall of MDF and the bottom with cloth covered rigid fibreglass?

giles117 · **Posted:** Wed Nov 16, 2005 2:53 am

120MM Computer fan at a slow speed just to move air for one.

www.silenx.com

Have you seen John's design for a soffit. It is in this forum. The upper half is MDF the lower half is a recessed cavity with insulation to absorb reflections off the console, etc....

My Monitors as you see are side mounted at EAR level (center point of the monitor)

I have acces at the bottom about 12" from the floor is open space covered by cloth to allow air in the soffit. a hole in the shelf to allow that air to circulate past the amplifier and the top is open to allow air to vent. (just 2" however)

Pasz · **Posted:** Wed Nov 16, 2005 5:36 pm

giles117 wrote:

120MM Computer fan at a slow speed just to move air for one.

www.silenx.com

Have you seen John's design for a soffit. It is in this forum. The upper half is MDF the lower half is a recessed cavity with insulation to absorb reflections off the console, etc....

My Monitors as you see are side mounted at EAR level (center point of the monitor)

I have acces at the bottom about 12" from the floor is open space covered by cloth to allow air in the soffit. a hole in the shelf to allow that air to circulate past the amplifier and the top is open to allow air to vent. (just 2" however)

Hi Bryan,

Where did you exactely put the fans? And how do you power them?

giles117 · **Posted:** Thu Nov 17, 2005 8:34 am

12VDC Power supply and under the monitors heat sink (amplifier), you could even mout it to a pc of rubber on the ends and mount it to the shelf the monitor will rest on.

Pasz · **Posted:** Thu Nov 17, 2005 7:06 pm

Thanx Bryan.

I'm still not sure what to do though.

As far as I can see no-one ever soffit mounted the Dynaudio BM6A's. There's no telling if the rear port will be a problem, or if the cooling will work ok. Heck, even Dynaudio say you can't soffit mount them. That should be a warning!

I asked if there were people at Harmony Central that soffit mounted these speakers but so far no one that did replied. Phil O'Keefe replied with yet another warning:

Quote:

You know, the more I think about this, the more I have to wonder... why do you wish to soffit mount your speakers? I'm going to assume (Bruce Swedien will take me to task if he sees that ) that it's due to space issues / concerns... but soffit mounting brings its own set of significant considerations and challenges.

First of all, any powered speaker (and that includes the Beringers, Dynaudios and ADAM's) that are not specifically designed for soffit mounts may have amplifier / cooling issues - not to mention safety (heat / fire) issues. That alone is reason for concern, and I would strongly advise proceeding with extreme caution...

Secondly, there are acoustical issues to consider. Soffit mounting any speaker will significantly change the sound of that speaker. Technically, a "box" speaker, when soffit mounted, isn't a true "infinite baffle" arrangement (the bass frequencies will still have compliance issues, since there isn't an "infinite" amount of space behind the LF drivers - they're still within their own enclosures), but you will have some differences in the bass response of the speaker once you stick it into the wall... IOW, unless you really know what you're doing, and you have a full understanding of the acoustical and physics principles involved and are willing to crunch some numbers, it's going to be very difficult for you to predict what the speakers are going to sound like once you get them into those soffits. IOW, it's a crapshoot - you may dig the resulting sound, but you might hate it too. Either way, it's going to be different than what they sound like when sittng out in the open - just as they would sound different if they are placed a few feet away from the nearest wall, or close to the wall behind them or when sitting in a corner...

Yes, I did soffit mount my 4412's, which is something they were never designed for, but I did considerable work to them too... I crunched some numbers, changed the LF driver, and I modified the crossovers.... and I was still surprised by the increase in bass response once I got them into the soffits.

One advantage the JBL's have is that they're passive monitors... which means I didn't have to worry about cooling and safety issues for built-in amps. As I mentioned, the ADAM's have heat sinks on the back for cooling, and many powered nearfields (there's a clue for you - they're designed as nearfields! ) have controls as well as heatsinks for the amps on the rear panels - IIRC, the Dynaudios have all of that on the rear too... which means that, IMO, soffit mounting them is a very BAD idea for several reasons. IMO, you're better off using passive speakers and external amps if you're dead set on soffit mounting. Just be aware of what you're getting into, and do some studying on the acoustic principles involved before you make a rather labor intensive and costly mistake!

I'm really not sure what to do.

Now I'm leaning towards just using them freestanding, building a lot of traps behind them. It seems to be the safest thing to do

.

giles117 · **Posted:** Fri Nov 18, 2005 12:48 am

I love tech stuff, started desiging and building stuff when I was a kid, won awards for what I built and at age 19 after 2 years in enineering school walked away. I did go back to college for accounting - still loved the numbers, but walked away again. Honestly I had more fun Mixing concerts than I did sitting in a classrom to learn to sit in another room. I was paying my way through school being a FOH engineer. Toured with a bunch of major groups and woke up one day asking myself why I am in college??? I am in my career albeit by accident. LOL. I realized, I may have designed and built, but I am a User.....

So, Let the designers design and the users use. They dont build Honda Civics to Race, but guys mod them add Superchargers, turbochargers modded manifolds, etc... and race them......

My Mackies weren't designed for soffits but they are in soffits and the LF is FLAT!!!!!

Heat issues. USE Fans.

Build the area and place no insulation on top of the heat sink (keep a nice clear path for air circulation......

affix the soffit insulation to the interior walls of the soffit. so they can do their job of obsorbing sound bouncing around in the soffit not sitting on top of your heatsink making your speakers go bad.

relaize, the mackies have a passive radiotor in them for INCREASED low end response. I dont know the dynaudios design. (I designed and built speakers from age 14-18) I have no desire to be as good as barefoot is with it, but when I was a teenager with nothing but FREE time that was my hobby. Earned a decent living. My Grandfather was an old Engineer who sat me down at six and taught me electronics and physics.....and had me helping build his speaker designs when I was 9 and 10. People tought 360 degree speaker design, Grandad designed and bult a set back when in 1974...... Those puppies sounded great for as long as I could remember.

Have fun.....There will always be the perfectionist speaking and he should be listened to, but in the end it is your application and your results that "satisfy your needs" that matter.

If you read back people said the same thing about me soffiting my 824's. Barefoot and I got into a practical verse Theory discussion about it. Eric Desart and I debated. and I have mad respect for these guys becasue I was involved in their end of the biz. But one thing I learned at age 15 FOR MY LIFE... was be more practical. Get the Job done. Yes dont build a building and skirt SAFETY, but get the job done.

so in summary. LOL (like this is an essay or soemthing. LOL)

It has been 2.5 years since I soffited my mackies. I leave them on 24/7 and life has been good to me. Now I want some Klein + Hummel O300D's

giles117 · **Posted:** Fri Nov 18, 2005 1:02 am

Now that I was FINALLY ABLE to get into Dynaudios site and read the manual....

The continuously variable LF trim is your tool of choice.

It can help you adjust the LF output to counteract the bass boosting that will come from soffit mounting a speaker.

Personally I;d prefer a swithc that just turns down the output of the LF drive altogether verses adjusting a set of frequencies.

I am iffy about soffiting your Dyns due to that one issue. If they had circuitry that allowed you to turn down the output of the Driver altogether instead of just a narrow band of frequencies then I;d completely so GO FOR IT.....

Quote:

LF Trim. This control allows the low frequency level to be adjusted. The control works
from 100Hz downwards and has a range of 5dB (see figure 1). This section
uses a special equaliser design which effectively swaps bandwidth for power.
As you turn the LF trim level down the low frequency extension is improved.

From their manual.....

giles117 · **Posted:** Fri Nov 18, 2005 1:17 am

Just wanted you to see the Mackie implementation of what i am talking about versus the Dyn's version.....

Mackies is as follows:

Acoustic Space Equalization......
A Position: -4db @ 500Hz Shelving
B Position: -2db @ 500Hz Shelving
C Position: Flat

Pasz · **Posted:** Fri Nov 18, 2005 8:38 am

Wow, thanx for the big reply, Bryan. I appreciate the research you did for me! Though before I read your post I was really beginning to doubt if going ahead with the soffits is a good idea, so I made some alternative plans (=no soffits!).

I have to admit right now I'm leaning towards NOT soffiting. Soffiting just seems to be too tricky and too much hassle.

I do respect your opinion, don't get me wrong. But right there's too many people saying "don't" and too little saying "do!" (you're actually the only one

)

Anyway, my post with the alternative designs is over here:

http://www.johnlsayers.com/phpBB2/viewt ... 4211#34211

giles117 · **Posted:** Fri Nov 18, 2005 9:23 am

Actually soffit mounitn is quite...quite simple....

The tricky part (or work part IMO) is setting the switches on the speakers correctly.....

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Soffit mount, don't know which design to choose

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