[JohninCR]

Once you start trying to minimize your baffle you run into a structural issue of vibration.  Based on the great reports by Nigel down in Australia using the B200s decoupled from his baffles and mounted by their magnets, I decided to give it a go.  I felt it was necessary due to the amount of vibration in my latest baffles with the B200 mounted on the baffle despite my woofer being physically isolated.  Linkwitz talks about magnet mounting being better, but I never fully understood the rationale, so maybe I'll get some extra hidden benefit.

Here's the wooden version I came up with, since I don't have Nigel's tools or expertise to do something in metal.  I made it adjustable enough to work with other drivers by just changing out the half circle magnet clamp.  The 2 pieces at the bottom are the woofer mount, giving me drivers isolated from each other as well as the baffle.  I used a very dense and heavy wood called Almendro.  Quick testing shows it to be structurally rigid and heavy enough to virtually eliminate vibrations from the B200's mechanical operation.  Some sanding and minor adjustments, then massage some oil into the wood and I'm in business.

[Folsom]

How does it sound though....?

[JohninCR]

It sounded good rigidly mounted to the baffle as shown below, but
there was alot of vibration, so it should sound even better isolated
from the baffle.  This rig will also give me a chance this week to try
diffraction rings on the B200 and see if I can make the NoBaffle work
with an 8" driver.

[Folsom]

Do you think the driver will hold out well? Not bottom out and hold volumes it did as OB?

Has anyone ever dampened no baffle speakers with polyfil around the back in a net or something?

[scorpion]

JohninCR,

In the Darkstar thread I think I at sometime talked about fishinglines for mouting drivers to the baffle when you refered to Nigel's magnet mount.
That was not meant as having fishinglines from the ceiling but rather taking them from the speaker basket over some kind of spindle and having weights in their ends (that's why fishinglines) to press the speaker towards the baffle. I still think this might be a worthwile way to go and I intend to test it. 

Now, I have heard the Silver Iris, you could go fullrange with those NB if crossed over to a potent bassdriver I think and like Rudolf indicated. The Augie NB would be capable of 85 dB at 32 Hz ( plus bonus of near floor mounting) according to Linkwitz. To crossover to the B200 NB I think will be more troublesome as I stated before.

/Erling

[hum4god]

hi john
your magnet mount looks great .
could you provide more insight in how the parts for itcome together , what they measure.
btw there is anothe magnet mount at hawthorne
see link
http://www.hawthorneaudio.com/forum/viewtopic.php?t=419
seems to be the latest fashion
malcolm

[JohninCR]

Destroyer,

I've only seen one other person use drivers with no baffle.  The gentleman had a number of
drivers hanging in fish nets under chairs, etc.  This was over a year ago on a another forum,
and I just dismissed it as nonsense.  Recently when I was ready to implement these 15's, I
was loosening them up with some LF tones and decided to prop them up in front of my
Frugelhorns and try them with some music.  My intention was to evaluate how high I could
run them, but the result was rich full bass.  I was dumbfounded because it went contrary to
everything I thought I knew about open baffles.  I need to learn how to do measurements
now that I have the equipment for it before I can talk about SPL and extension, but I listen to
some types of music at just below painful levels and I've never had better full sounding bass.
I've watched the drivers on bass heavy segments and they're running nowhere near full excursion.

Some type of absorbant behind the driver isn't going to have an impact on bass frequencies
because they go right through it.


Scorpion,

Now I have a better idea of the strings you mentioned, although I'm still not totally clear.  There
are valid arguments to be made that drivers playing HF shouldn't move, and with low frequencies
movement reduces efficiency.

I come up with and 82db at 35hz limit according to Linkwitz's DipoleSPLmax spreadsheet.  Even with
a perfect +6db from the floor, something doesn't make sense because I regularly listen to music in
the 90+db range.  I'm not talking about chamber music either.  I find myself turning the bass down
with some of the pop/club type music my wife likes, but my Pink Floyd collection sounds perfectly
balanced with nothing missing.

I believe part of the difference has to do with the directive nature of dipole bass.  Linkwitz discusses
this at length, and boils it down to a 4.8db advantage for dipole bass over boxed bass, because you're
listening to far less reflections.  I think it's more than that too.  Maybe it's the room and placement
resulting in the rear wave reflections helping rather than hindering.  Maybe it's that we perceive
dipole bass differently in some way, but I doubt this aspect because I also tried a 2nd B200 as a bass
augmenter (on a 44cm wide baffle near the floor) because of reported good results by some, and those
results were quite disappointing even running the B200 past xmax.  It was nowhere close to how the
15" driver sounds with no baffle at all at far less excursion. 

This makes me suspect that somehow the large wave launched by the big driver somehow behaves
differently when it first clears the driver.  I'm sure the tech types are cringing once again, but at the
same SPL the sound coming from a large driver is definitely different, and sounds "larger" than the same
sound originating from a smaller driver.  Once I get measuring down pat, I intend to figure this out even
if I can't determine the cause, because "larger driver with a smaller baffle = more bass", if true, is
something radical and new.

[JohninCR]

hi john
your magnet mount looks great .
could you provide more insight in how the parts for itcome together , what they measure.
btw there is anothe magnet mount at hawthorne
see link
http://www.hawthorneaudio.com/forum/viewtopic.php?t=419
seems to be the latest fashion
malcolm

I saw Darrel's wooden clamp the other night, and that's what gave me the idea for constructing
mine the way I did.  I cut a circle and cut it in half.  Then I cut a piece the size of the magnet
diameter out of each.  Then I cut those in half to make the right size clamp with an adjustment
range of the width of the cut.  Having the grain in the proper direction is probably important for
strength.  I didn't measure anything except the diameter of the magnet. 

The bolt hole in the angled piece coming up from the base is about 2" in diameter despite the 3/8" bolt
running through it to give me real adjustability in the vertical and horizontal location of the horizontal
brackets.  The bolt holes in the 1/4 circle pieces of the wooden clamp are larger than necessary for
the same reason.

I also rounded the jaws of the clamp.  If you view them from the front they are not flat.  This is so
the wood touches the driver evenly instead of squeezing at just 2 points on the magnet, which wouldn't
be very secure in the horizontal plane.

[opnly bafld]

I believe part of the difference has to do with the directive nature of dipole bass.  Linkwitz discusses
this at length, and boils it down to a 4.8db advantage for dipole bass over boxed bass, because you're
listening to far less reflections.  I think it's more than that too.  Maybe it's the room and placement
resulting in the rear wave reflections helping rather than hindering.  Maybe it's that we perceive
dipole bass differently in some way, but I doubt this aspect because I also tried a 2nd B200 as a bass
augmenter (on a 44cm wide baffle near the floor) because of reported good results by some, and those
results were quite disappointing even running the B200 past xmax.  It was nowhere close to how the
15" driver sounds with no baffle at all at far less excursion. 

I think the room plays a large part also.
My first stereo was in a concrete basement and I had to have a lot more output in the bass frequencies than friends with stereos on the main floor with wood walls.
My first pair of speakers had bass at the dealer showroom, but when I brought them home I kept checking the polarity of the wires because I had no bass. Then after a couple of years I sold them to a friend and could not believe the bass they were putting out in his livingroom.

In my (on going) experience with the B200 vs. Augie, I would say the B is like a 4 cylinder w/200 bhp and the Augie like an V-8 w/a little over 200 bhp. The B is working harder, but integrates better with the top B. Where as the Augie is just loafing along but to me just does not have the same quality to the bass to match the B200 as well as another B does. Most of the time with most music the second B200 just sounds better to me. Much like a lighter 4 cylinder often works better in a small light car than does a bigger heavier V-8.

Another thing about rooms and houses, my OB bass does not stay in the listening room like you keep saying.
I have a hallway opposite where the speakers are that goes to the back of the house to the bedrooms and I have just as much bass coming back to my bedroom as I do with sealed or BR speakers in the same location as my OBs.
These are all just my OBservations, others OBs may be different.

Lin

[JohninCR]

Lin,

I didn't say integrating a large driver is necessarily easy.  Of course, using
an identical one should be easier.  I'm sure a B200 augmenting the bass of
another B200 is quite satisfying for some, especially since some like the
B200 all by itself, just not for me and I'm no basshead by any stretch of
the imagination.  Now that I've had rich full OB bass there's no going back.
I wish 2 B200's did work for me.  Then I could come up with an easy one
amp solution without without biamping and an active XO, for use in a system
elsewhere in the house.  I tried it primarily based on your recommendation,
but it didn't work for me and it wasn't any trouble to try.  If it works for you,
then great.  My previous post in this regard was only to point out that the
performance difference of a large driver is far from subtle.

While room and placement will always impact the bass response of any
speaker, for comparison of 2 ob systems, using the same room and placement
results in a valid comparison.  If anything, the mostly concrete structure of
my room increased the bass response for both compared to a typical sheetrock
with studs construction.

Regarding OB bass staying in room better, it goes without saying that on
axis it will travel right down the hall.  Just turn your speakers 90 degrees
and then you'll understand.  That same reduced level applies 4 of the six
directions relative to the speaker (up, down, left and right), not to mention
that, as Linkwitz explains, you inherently listen to your OB's at 4.8db lower
volume for the same perceived loudness due to increased directivity.  In
addition, OB doesn't have pressure vessel gain that I think increases
structural born transmission of sound (like the bassheads in cars and their
boom, boom, boom.  Give them OBs for bass inside their car and they can
listen to the same SPLs without us complaining so much.).

[Rudolf]

... I've only seen one other person use drivers with no baffle.

JohninCR,
you are not that alone. Look at this example from the US:

http://www.claudionegro.com/projects/speaker/dipole/dipole.html

And at this example of some Eminence Kilomax 18" hanging on strings from the ceiling:
http://img91.imageshack.us/my.php?image=schwebendereminence8vl.jpg

with the equalized in room response:
http://img400.imageshack.us/my.php?image=dipolefrequencyresponse3gk.jpg

The owner assured me that the driver does NOT move significantly - discoteque levels included.

[JohninCR]

Thanks Rudolf,

After visiting the first link, I realize that I did see Jose's projects before.
I dismissed it because I thought I knew better, since it couldn't have
bass.  Little did I know.

Thanks also for the suspended in air link.  I'm up in the air about
whether I like the look or not.  Pardon the pun, I couldn't resist.  I have
small kids anyway, and the last thing I need is them realizing they could
use one of my 15's as a swing.

[Bob in St. Louis]

the last thing I need is them realizing they coulduse one of my 15's as a swing.

 

[scorpion]

I ran across this in the Audiotreff forum. Nothing is new under the sun ! Portable, Magnet Mount, No Baffle what to be done ?



/Erling

[Bob in St. Louis]

Didn't work Erling, could you try that again please?

Bob

[mcgsxr]

I can see it, a scan of an old brochure I think?

[mcgsxr]

Actually, I DID see it, but it is gone now... odd.

[JohninCR]

I saw the ingenius magnet mount at the Decware forum.  I've got some 4" 90deg pvc elbows that could also work easily, but the exterior of PVC unions aren't very elegant, however, I also have some 4" PVC pipe which the B200 magnet almost fits into.  With just a small cut in the pipe it will slide in snugly.  I read up about bending PVC here (be careful of fumes released when heating it) http://billpentz.com/woodworking/PVC.html .

Below is a pic of a quick test I did.  I had tapered the inside edge of the PVC to help slide the magnet in for a snug fit.  For the real thing, I'd make the cut about an inch longer and make the hole large enough to run my speaker wire inside the PVC.  The drill hole is important to help prevent the cut from expanding into a long crack.  Though it is snug I'd add a clamp for security, and position the tightening head for the hose clamp and the cut in the PVC.  You could either bend the PVC, or make a joint using an angled cut.  Then you just need to figure out a base and paint it for an elegant, simple and cheap magnet mount structure.  I'll fill mine with concrete for good mass and rigidity.

I may not get around to mine for a while to post more complete pics, but 9anda1f's idea is such a good one that I thought anyone about to start construction would want to know now.

[mcgsxr]

I was at Home Depot this morning, and reviewed some interesting "plumbing" options.

Of particular interest was a rubber flange with pipe clamps on it, designed to be a mating device (ie 4 inch to 4 inch but straight, and lightly flexible) that would be dead simple to use.

I also noticed that they carry 12.5 inch sonotube now, before I was always hamstrung, as the largest they carried was 8 inch, and I use 12 inch subs!

My mind is racing with fun ideas around K slot U shaped bass baffles!

[JohninCR]

Mark,

The rubber flange was something the other guy was using, but the problem is that it sags.  I picked up a length of 3" PVC today with the intention of heat stretching the driver end to make the magnet fit snug and add a slice to make it clampable.  I think the tapered look will be cool and a one piece unit down to the base using 3" reinforced on the inside with concrete should turn out slick and clean.  I plan to try the car exhaust heating method for bending and stretching, so anyone could do it.  I'll report back regarding success or problems, but I think the hardest part will be creating 2 identical poles.  I think some kind of bending guide may be necessary.