Svante said:
I guess that depends on how much damping is required. Subjectively, I like the way my speakers sound with the carpet damping layer. They sound different with stuffing, muffled almost, like the stuffing was touching the cone (which of course it was not).
Bracing, both panel and driver, is a long established method, I use it extensively (no, not dowels and shelf).
planet10 said:
And orange shag on the inside?
I admit that I've never heard a good fullrange, how does this little speaker sound? Whats inside? Is that a perforated brace down the middleish? Remember, I'm new here.
Originally posted by rick57
Wouldn’t BR be close to TL, and aperiodic be a little lower than sealed?
Originally posted by dave:
As soon as you put a hole in the box the pressure is reduced at some frequencies...
if you were to want to do a vented box, that would also be low pressure inside;
and over what frequencies would that or an aperiodic ‘hole’ reduce pressure?
Originally posted by dave:
No air space dampig (felt/wool/poly fluff/fiberglass is very effective at low frequencies.
Take a look at the attenuation data near the bottom of this page (some of the other information on the page is out to lunch and i really should add an editors note or 2)
www.t-linespeakers.org/proje...bury/index.html
the graphs on the link say that wool/fibreglass is (as expected) progressively less effective at low frequencies, but your words suggest to me otherwise . . forgive me if I’ve missed it, but in summary:
- mechanical vibration is much more of a problem than sound pressure
- even in sealed boxes?
- though of the sealed/ BR broad “range” (TLs aside), aperiodic is best
- aperiodic internal pressure is lower at frequencies ? Hz
felt/wool/poly fluff/fiberglass is better than rubber or bitumen pads
- but they are effective at low frequencies, hence use bracing to push the resonances up into the felt/wool/poly fluff/fibreglass effective range, where the energy required to excite is also lower
. . have I got it all?
Wouldn’t BR be close to TL, and aperiodic be a little lower than sealed?
Originally posted by dave:
As soon as you put a hole in the box the pressure is reduced at some frequencies...
if you were to want to do a vented box, that would also be low pressure inside;
and over what frequencies would that or an aperiodic ‘hole’ reduce pressure?
Originally posted by dave:
No air space dampig (felt/wool/poly fluff/fiberglass is very effective at low frequencies.
Take a look at the attenuation data near the bottom of this page (some of the other information on the page is out to lunch and i really should add an editors note or 2)
www.t-linespeakers.org/proje...bury/index.html
the graphs on the link say that wool/fibreglass is (as expected) progressively less effective at low frequencies, but your words suggest to me otherwise . . forgive me if I’ve missed it, but in summary:
- mechanical vibration is much more of a problem than sound pressure
- even in sealed boxes?
- though of the sealed/ BR broad “range” (TLs aside), aperiodic is best
- aperiodic internal pressure is lower at frequencies ? Hz
felt/wool/poly fluff/fiberglass is better than rubber or bitumen pads
- but they are effective at low frequencies, hence use bracing to push the resonances up into the felt/wool/poly fluff/fibreglass effective range, where the energy required to excite is also lower
. . have I got it all?
MJL21193 said:nd orange shag on the inside?
I admit that I've never heard a good fullrange, how does this little speaker sound? Whats inside? Is that a perforated brace down the middleish? Remember, I'm new here.
No orange shag... 1/2" thick cotton felf on all interior surfaces, including the driver brace (so far we have managed to source it from vintage 60s/70s Norescos & the like, but that supply is running out). The holey brace also does a job of breaking up side-to-side standing waves with the layer of felt right at the max pressure of any full side-to-side standing way (the not-holes part of that brace also creates a situation where there are 3 different distances side-to-side)
Plans are here (1st entry)
http://www.planet10-hifi.com/boxes-fostex.html
There is also a version for the CSS FR125 (on the creative sound page)... there is almost no application overlap between these 2 because they each like different kinds of amp.
dave
rick57 said:
A BR port is a fairly high Q 2 pole device... pressure is lowered over the bandwidth of the port. An aperiodic port (ie a port with resistance in series is a lower Q 1st order device -- it has a broader bandwidth.
Then i either spaced out and did a typo somewhere or you aren't grooking them yet.
Not completely ... in a sealed box internal sound pressure is more of a problem than in "leaky boxes" (note that leaky boxes are most leaky at low frequencies where ther is more energy.
These 2 kinds of things serve completely different purposes and shouldn't be in the same sentence... It is like saying, this hammer is way better at pounding nails than this soccer ball...
dave
rick57 said:
They are 2 different issues and will depend on both how the box is built & what kind of box it is.
Now if you mean, is energt transmitted mechanically more of a problem than that transmitted thru the air cavity, that is a different question, but still is dependent on the box.
If you look at the way a speaker works, when the cone moves back & forth it generates energy,,, half goes into the box (and in some cases this energy is harnessed and sent out of the box too) & half goes to the outside world. Every motion of the cone has exactly the same energy, of opposite magnitude being subjected to the driver frame.
So ignoring parasitic losses, we have 25% (or less) of the energy going into the box air space, 25% (or more) headed out into the world (where we will say it effectively is lost), and 50% going into the frame.
The energy going into the airspace of the box is coupled by a compressible medium to the box walls (and dissipated somewhat by the airspace damping), but almost the entire amount of energy in the frame is transmitted to the box (the discussion of lossy coupling of the driver to the box is a whole nuther discussion)
Ignoring the squishiness of air coupled energy, the mechanical energy coupled to the box walls is already 2 x the airspace energy coupled to the walls. Add leaks and the squishyness of the air and it is pretty easy to say that the mechanical energy coupled to the box walls is very much larger than the energy transmitted thru the airspace.
dave
With my cautious devil’s advocate hat on yet again
If I hadn’t read you numbers, I would have thought ignoring losses, depending on driver mounting, more like at most eg:
40% of the energy going into the box air space, 40% (or more) out into the world (where we want it), and 20% going into the frame . .
Why do you think so much of the energy going is into the frame?
thanks
If I hadn’t read you numbers, I would have thought ignoring losses, depending on driver mounting, more like at most eg:
40% of the energy going into the box air space, 40% (or more) out into the world (where we want it), and 20% going into the frame . .
Why do you think so much of the energy going is into the frame?
thanks
been > 30 years since I looked at Newton's laws . .
thanks again
I might add that I'm most interested in open baffles, but they’re not suited to every situation or room.
On an open baffle note, I wonder if best is:
~ ¾ inch ply – SL uses it
~ corian –higher mass – probably not
~ CLD, maybe with liquid nails or more highly damping Green Glue
www.greengluecompany.com/greenGlue-vs-engineeredDampedGlue.php
I think CLD will not be a benefit, so that’s probably a red herring.
JohninCR, dave, anyone?
Cheers
thanks again
I might add that I'm most interested in open baffles, but they’re not suited to every situation or room.
On an open baffle note, I wonder if best is:
~ ¾ inch ply – SL uses it
~ corian –higher mass – probably not
~ CLD, maybe with liquid nails or more highly damping Green Glue
www.greengluecompany.com/greenGlue-vs-engineeredDampedGlue.php
I think CLD will not be a benefit, so that’s probably a red herring.
JohninCR, dave, anyone?
Cheers
rick57 said:
They are two different issues. You could build a box that has little problems with the structure and terrible problems with acoustic resonances and vice versa.
It all depends on the geometry of the box (size and wall thickness), the amount of bracing, the amount of stuffing etc, and also the frequency range that the speaker is to be used for.
Liquid nails - if, but
There are many forms of liquid nails.
www.liquidnails.com/ViewProductListing.do
This one remains is noted by the comany to be flexible (less inflexible?)
www.liquidnails.com/ViewProductDetails.do?productId=60
though is it worth the saving if something else (?) is better?
Though if the liquid nails or alternative are sealed on all sides, I believe they do stay flexible . .
There are many forms of liquid nails.
www.liquidnails.com/ViewProductListing.do
This one remains is noted by the comany to be flexible (less inflexible?)
www.liquidnails.com/ViewProductDetails.do?productId=60
though is it worth the saving if something else (?) is better?
Though if the liquid nails or alternative are sealed on all sides, I believe they do stay flexible . .
coupling the baffle
I think it's Davey here http://orion.quicksytes.com/viewforum.php?f=1 a friend of SL, who suspends his Orion or Phoenix from the ceiling. SL did it himslf about 20 years ago
IIRC the swing frequency of the ropes & hanging is ? 0.1 Hz, just below the passband
I think it's Davey here http://orion.quicksytes.com/viewforum.php?f=1 a friend of SL, who suspends his Orion or Phoenix from the ceiling. SL did it himslf about 20 years ago
IIRC the swing frequency of the ropes & hanging is ? 0.1 Hz, just below the passband
planet10 said:
Hate to break it to you Dave, but that 1/2" felt is panel damping, serving the same purpose as my carpet(although my carpet is more effective).
Very nice though. You still didn't comment on the sound quality. Port area and length as for that driver in a bass reflex that size? Or did to you tune by ear?
The second one on that page has panel sizes large enough for serious resonances, luckily, you advocate panel damping for these also.
MJL21193 said:
I think not... far too floppy for that and only spot attached to the panels (just so it doesn't move around when you move the box -- if we can get an airgap between the damping and the box wall we are happy. It serves the same purpose as an 1 1/2 of fiberglass insulation
dave
John,
I don't have any experience with OB's, though they are in my future. I'm currently working on a set of mtm's which will probably be my last of those for awhile...so many other interesting options to explore. I won't pose as an expert. I do have construction experience that I draw from.
I caution against the use of Liquid nails because they are formulated as "adhesives" and meant to bond materials together. I favor the use of caulks which are designed to allow movement between the adjoining surfaces. Caulks have adhesive properties that lend themselves to bonding materials together. Enough to hold "floating" panels in place. You would only have to use a little as glue to see how strong it is.
CLD is a non-structural application. To retain the damping qualities one should not clamp pieces together...less thickness of the damping medium means more strength across the joint, which transfers more vibration and means less damping.
My review of the MSDS for Green Glue tells me it is made of "acylic polymer". That serves as a clue in the search for a cost-effective alternate. In my current project I'm going to use a sealant (caulk), NP-1 by Degussa, because I have some on hand.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.