[Bob in St. Louis]

i wonder if the metal brackets close to the magnets is affecting things?  just kidding!!!

Actually, it's a very real concern. The question was brought to my attention by a few members, but when I told them the gauge of material they said it wasn't a problem.

you really aren't that happy with them??

Visually, no. Sonically, So far, so good.

Are they grounded, felted & de-screen'd?

De-screened only. The other tweaks I want to wait on. I want to get a good feel for how they sound in their new clothes before I tweak anymore. I only did the screen removeale because I had them apart during the build.

Mine work best pointed towards the sky - up, up & away...about a 40 degree angle in their baffles is good.

I've heard that (on the magic shipping boxes).  It was amazing how good they sounded propped up like that. I've seen your pics Matt. I like your rig!  aa

Bob

[gooberdude]

Bob,

If you are hearing ANYTHING about the SI's that's thin, there's a problem.  These guys pump out the jams with a timbral accuracy that seems so right on to my ears...

balanced is an odd way to describe a 15" co-ax, but that's what i'm hearing. No harshness, shrill or thinness should be present in ANY form...  the midrange, deep bass & compression driver performance is astounding. 

Bob, the speckly finish should serve to reduce reflections to a degree but spend $5 on a yard of felt and see what happens.  Also, grounding the baskets will go far to remove any thinness. Just wrap the felt loosely around & hold with safety pins or use a bit of adhesive spray temporarily....  too many reflections can cause the high frequencies to 'get noticed' - in my DIRECT experience as noted on the Hawthorne Forum.

You really shouldn't torture yourself or your designs if the drivers aren't at their best.   I'm a tweaker, but one with an ear for what is right (and no techy background).    Ground & felt immediately.   You can listen for 10 years to these drivers and not hear them the way they should be without the free, simple & reversible tweaks avail.

One thing i'm getting quite hip on is having NOTHING interfere with the back wave.  what if your magnet mount is introducing turbulence? I'm not talking hysteresis of the magnet again, just physcial blocking of the sound wave by the vertical post holding up the magnet mount.   this might sound silly & a mockery to your current design (which i really like!) but i wonder if having the woofer mounted directly to the baffle, but still retaining the exact same shape, might alleviate your issues?   Using Dynamat Xtreme as a gasket material has reduced baffle vibrations by a large amount on mine...

i only say this due to what i have going on at home: the SI's are SO cool & rich & accurate & fast & easy to implement.   

Now that i type this with a pic of your baffles opened in a 2nd window a idea just popped in:  What if the ring around the driver needs to be mounted so IT won't vibrate?    Follow me:  vibes in these speakers start at the voicecoil and shoot forward through the drivers....ultimately reaching our ears.  What if the ring (where the screws mount to for baffle mounting) is allowed to vibrate in your design & this is causing weird stuff to happen??   The stamped baskets might be best suited for baffle mounts & your baffles killer for the Sterlings.

there are so many aspects to deal with, but if we had Fostex or Lowthers we'd be dealing with a much more elaborate set of 'what ifs'...ya know???

problems w/the SI's should be simple to remedy.  The only Beaming with the SI's is when my buddy's bring that crap over.  I'm a Maker's Mark kinda guy.   


other than baffle issues...there's always gear & room acoustics.   

[Bob in St. Louis]

Hey Matt,
Regarding the 'thinness', that was only on my "stop sign" mounts. Zero baffle, just the driver mounted on a post. Those had stupendous EVERYTHING, but lacked bass (obviously). These lack that thinness of the previous design.

Regarding the padding/felting on the back, The thickness on the rear varies from 2" to 6" thick. Most EXPANDING FOAM. The foam, which normally hardens with a thick skin was sanded down exposing a softer foam inside. When poked with a finger it feels squishy. Originally my intention was the entire lower structure was going to be fiberglass and resin. Then I was thinking about a soft foamy padding back there but since the expanding foam was used, it provided a nice soft absorber.

About the blocking of the rear wave, I thought about too and agree to a certain extent. The Solo/Duet's have a 5-6" wide 'one-by' running vertically on the rear. I wouldn't have thought it be a good idea, but hey, much smarter folks than I are doin' it.

The ring around the driver is very steady. No vibes!! The next baffle I build will be "separates". meaning no contact between baffle and driver. At all.

Bob

[gooberdude]

That's a great idea of using the expanding foam and then sanding it down a bit.   you created a huge absorption area probably.   I need to go back over your construction photos....

sounds like you do enjoy the performane of your super baffles after all!


at some point i'd like to hear how these do with no baffles at all, and up on stands like your originals.  I wonder if the Allison effect wasn't in play too, i've experienced bass loss when having woofers up too high.

All i meant by doing some 'other tweaks' sooner rather than later is that they might get you where you want to be FAST.  You can remove the baket ground wires in 2 seconds if you don't like the effect....        A good friend of mine bought a nice Belles amp goin on my suggestion.  After he got it he hated it...when i went over to see what was up he still had the stock power cord in.  Once i inserted one i made he went 'oh!' and about his merry way, happy with the amp purchase.    thinking outside the box often leads to happiness with the box!


matt

[JohninCR]

John,
Is there a "rule of thumb" that you used to get the dims for your cddwg/rlh or was it just intuition? I ask because I wonder if anyone would be willing to do what you have done but with a different driver. I was thinking of the SI's. Huge, I know. I understand that you had abandoned using styrofoam since the fiberglass resonated too much, but what if someone were not averse to it being unfinished? If I were to laminate that stuff together and carve it into a solid sphere then cut out the wg apertures front and rear... What do you think? how big of a sphere would it need to be? 90deg opening front and rear or is it not constant? Perhaps a silly idea, but then why not?

I am creeping into this OB thing very slowly. I just won and am soon to receive a pair of 12" Corals(not FR, alas) from eBay. Hooray. BTW, do you know if there exists the sort of software you are using as xover for Mac? Otherwise I will have to go with a Pro Xover like MJ's DBX or something to pair with my DEQ2496.

This has been fun reading and seeing what you guys have been doing. Thanks for sharing with us lurkers.

Erik

Erik,

Here's some stuff on waveguides  http://sound.westhost.com/articles/waveguides1.htm

Believe me when I say you don't want to use styrofoam in a speaker.  It transmits sound too well.  Think how clearly you can hear ice sloshing around inside a styrofoam icechest.  The stuff I made was with stuff just like a cheap icechest, polystyrene beads bonded into a sheet.  The sheets like the blue stuff used in construction is probably much better, but it's not available down here.  The problem I had was that sound hit the foam and travelled right through it, and pressing my ear to it was louder than the speaker.  Fun but a complete waste of time.  There's an audio reviewer who built a U-baffle type OB out of styrofoam and posted the details on the web a couple of years ago.  Needless to say that he has lost all credibility with me.

After some recent stuff I've done, I'm losing my faith in real wood too.  For me it's about the same price as plywood, and finishing is so much easier (rub some oil on and you're done, except for rubbing more oil).  The problem I'm finding is that wood transmits sound too well, so I'll end up having to laminate layers of other material to it for damping, and/or make driver mounting rings out of a dead material like MDF and decouple that from the baffle.  That gives me the added benefit of quick easy changes in drivers, making my baffles more versatile even with flush mounting.  Damping the driver frame will help some, but think about the sound directly hitting the driver cutout.  That's only an inch or less away from the sound source.  Think about how loud that is.... say 90db at 1m...+6db each halving of distance or about 120db !   Whatever portion that gets into the wood at the driver cutout travels throughout the baffle.

Don't worry Bob, those Augies are playing frequencies way below the resonant frequency of your maple, plus it's butcher block.

Not only do we have to listen to our OB's, but we need to feel them too for vibrations.  Someone mentioned a good trick to me the other day.  Put a screwdriver handle to your ear, and touch the other end to your baffle.

[gooberdude]

JohinCR wrote
'Not only do we have to listen to our OB's, but we need to feel them to for vibrations.  Someone mentioned a good trick to me the other day.  Put a screwdriver handle to your ear, and touch the other end to your baffle'

I've found this to be crucial & made much easier with OB drivers compared to my boxed speakers...those i couldn't get within a foot of w/o earplugs.    I can sit down next my new OB drivers for a full album, touching and groping for them vibes, without hurting my ears.   the cancellation to the side is a real benefit too.

If you guys recall, the screwdriver technique is how the deaf son in 'Mr. Hollands Opus' tuned his car's motor.


thanks for that waveguide link John, been lookin for something like that.


matt

[mcgsxr]

I can sit down next my new OB drivers for a full album, touching and groping for them vibes

Yikes, getting personal! 

Glad you are loving them!   

[gooberdude]

Occasionally i start thinking like Tobias Fuenke from Arrested Development...it just comes out!


see, there i go again...


It's nice to snuggle up next to the SI's though.  my thiels' silk tweet would cut like a razor blade if I got within a foot, necesary to turn the volume way down when moving them or playing with toe-in in fear of damaging my ear.


Now if i said something like "grab it real hard with one hand & stroke it with the other" you guys would be free to take direct aim.   




matt

[Bob in St. Louis]

Sometime I lay in front of the speakers with all my clothes off and then...... 



..............Never mind   

[gooberdude]

Bob,

If i had a HT like yours i'd make it a requirement that all ladies entering the room must disrobe.

It'd be easy to convince them that all the 15" woofers are goona rip their clothes off otherwise!

[Bob in St. Louis]

 aa

[JohninCR]

Bob,

Thanks for saving use the gory details.  What was left to the imagination was bad enough to start the week.

I think goober is ok.  We'd have to worry if he had a set of these vintage RCA's though, some strange cones:
http://homepage.mac.com/ikecarumba/PhotoAlbum21.html

[Bob in St. Louis]

 
Those are cool looking drivers. Not that I'm getting excited or anything. 

Bob

[Viridian]

Erik,

Here's some stuff on waveguides  http://sound.westhost.com/articles/waveguides1.htm

Believe me when I say you don't want to use styrofoam in a speaker.  It transmits sound too well.  Think how clearly you can hear ice sloshing around inside a styrofoam icechest.  The stuff I made was with stuff just like a cheap icechest, polystyrene beads bonded into a sheet.  The sheets like the blue stuff used in construction is probably much better, but it's not available down here.  The problem I had was that sound hit the foam and travelled right through it, and pressing my ear to it was louder than the speaker.  Fun but a complete waste of time.  There's an audio reviewer who built a U-baffle type OB out of styrofoam and posted the details on the web a couple of years ago.  Needless to say that he has lost all credibility with me.

After some recent stuff I've done, I'm losing my faith in real wood too.  For me it's about the same price as plywood, and finishing is so much easier (rub some oil on and you're done, except for rubbing more oil).  The problem I'm finding is that wood transmits sound too well, so I'll end up having to laminate layers of other material to it for damping, and/or make driver mounting rings out of a dead material like MDF and decouple that from the baffle.  That gives me the added benefit of quick easy changes in drivers, making my baffles more versatile even with flush mounting.  Damping the driver frame will help some, but think about the sound directly hitting the driver cutout.  That's only an inch or less away from the sound source.  Think about how loud that is.... say 90db at 1m...+6db each halving of distance or about 120db !   Whatever portion that gets into the wood at the driver cutout travels throughout the baffle.

Don't worry Bob, those Augies are playing frequencies way below the resonant frequency of your maple, plus it's butcher block.

Not only do we have to listen to our OB's, but we need to feel them too for vibrations.  Someone mentioned a good trick to me the other day.  Put a screwdriver handle to your ear, and touch the other end to your baffle.

John, thanks. I will try to digest that article. I'll have to try the blue styrofoam out and see how it works. I can't stop wanting it to work. So easy.

[Viridian]

Dang, there is all kinds of good stuff on that site. Thanks John!