Loudspeakers: do yours have acoustic insulation in them?

[3rd_shift]

One can usually find out by looking inside a bass reflex port, or dismounting a woofer, or the full range unit with a screwdriver.

If there is no insulation, or a poor amount, adding some from an old, clean dacron, or polyester filled pillow, loosely stuffed in there can improve the sound quality quite a bit at little to no cost.

Hope this helped.

Loudspeaker design and building was an old hobby of mine in the 1990's.

 

[65535]

I have some Teac SPeakers which have heavy duty high density insulation.

 

[TedTheLed]

..possibly, unless the amount of insulation you add affects the internal volume so as to change the sound for the worse..but if the speaker sound suffers from internal reflections, which turn into external vibrations, adding insulation won't necessarily help, though it well may.. what you want are speaker walls that don't vibrate to begin with which means the heavier, and/or the stiffer, the better.
that's why my JR's are so great; they are aluminum cylinders with an internal tensioning rod pullingthe top and bottom together, and yes, there is a layer of dense foam insulation against the internal wall..

 

[WNG]

..
that's why my JR's are so great;

Pics!

Yes, any speaker I own that will play mid-bass-bass frequencies.
I like acoustic suspension designs, therefore they get a fill of polyester. Some few ported and bandpass subwoofers will get lined with fiberglass or anechoic foam sheets.

This will reduce standing waves and internal reflections, usually yielding cleaning tighter sound, if the speaker is a decent one to start with.

 

[DUQ]

I always peak inside speakers when I visit audio shops. Most of them do not have any acoustic insulation inside. I remember reading an article in an audio magazine about building speakers out of cinder blocks. Im searching for it.

 

[SoundMix]

In my 40 years of experience with high-end, professional speakers, I've replaced a few drivers and crossovers. I have never seen a speaker cabinet housing mid-range/woofers without some sound absorbing material.

I have also opened up quite a few home speakers: AR, Pinnacle, Vandersteen, JBL, Yamaha, Altec, and sealed back guitar/bass speakers, all with some sort of treatment.

 

[rdh226]

A little over-generalized...limit to "cone box" speakers. Consider, for example,
dipole radiators like Magnapan, Apogee, Genesis. I would imagine Klipsch's folded
corner horns likewise eschew any sound-dampening material (but have never
looked inside them).

-RDH

Edit: to answer the actual question posed by the thread title...while I strongly
syspect my Genesis 200's woofer towers do indeed have acoustic dampening
material in their "cone box"es, the midrange/treble towers (100Hz on up) do not,
but the midrange is a dipole radiator panel...and the whole tower is angled planar
construction to control diffraction/reflection patterns.

 

[beautifully-stupid]

We used to add cotton or poly fill into speaker boxes to create more "airspace", It worked but as suggested above, if you add too much you will alter the performance of your speakers.

I don't know the physics behind it, I just know that it worked ... for the most part.

 

[rdh226]

I don't know the physics behind it, I just know that it worked ... for the most part.

The principle idea to absorb/dissipate the acoustic energy that would otherwise be
trying to turn the speaker enclosure into a passive secondary radiator.

For the "typical" (if such ever actually exists) "cone in a box" speaker, when the cone
travels inward, it compresses the air inside the box, causing the box to flex (expand)
180 degrees out of phase with the acoustic signal the cone is trying to reproduce
out the front, resulting in some (minor) degree of cancellation of the signal. The
effect varies by frequency (the box responds -- resonates -- differently), resulting
in potentially-audible coloration (distortion) of the reproduced signal. In really bad
cases, you can hear the box itself buzzing & rattling (really cheap/crappy speaker!).

Another effect is reflecting the acoustic energy (waveform) being generated inside
the box back against the cone trying to generate the signal in the first place,
another form of coloration/distortion.

Yet another effect would be acoustic coupling between adjacent element enclosures
(bass cone woofs inwards, flexing bass enclosure, one wall of which is shared with the
midrange cone; when the shared bass/midrange wall woofs (so to speak), it will
compress the air and act as a driving force coupling to the midrange cone, pushing it
outwards -- you've now acoustically coupled the woofer cone to the midrange cone,
turning it into a passive radiator, and 180 degrees out of phase with the woofer cone.

By putting acoustic dampening material in the box, the acoustic energy that would
have gone to flexing the box instead goes into the dampening material (dissipates
as heat). The dampening material can also serve to isolate and pack down stuff
(wires, etc.) that otherwise might have their own tendency to rattle around.

Another approach to minimizing this effect is to internally baffle the enclosure such
that it's not "regular" -- walls are at odd angles and such -- to disperse internal
resonance. A cube is the worst "enclosure" -- it's one big resonant cavity with
all walls resonating together. Actually, a sphere would be the worst...unless
of course you can master the sphere such that the sphere itself is the radiating
element, kind of a Holy Grail of speaker design. The Heil plasma speaker tried
this -- using an ionized plasma sphere as the radiating element. Supposedly (I
never heard them) worked extremely well, but neighbors wondered why you kept
having tanks of helium delivered to your home! He he!

Years ago, I recall reading about some guy who was trying to cast speaker enclosures
into the foundation of his house...on the theory that a few tons of cast concrete
would make a very inert enclosure. Don't remember the results, but it seemed to
make sense, at least to the lunatic fringe element. Not very practical for the
mainstream populace.

-RDH

 

[Mike V]

I thought the insulation was just a cheat to make the enclosure sound bigger?

For example I doubt B&W Nautalises have insulation in them?

They are supposed to have enclosures the correct size for the cones.

 

[MikeSalt]

Mike V, excellent choice of speaker, the best in the world. I cannot remember if the Nautilus Prestige has acoustic wadding or not, but it is mainly the shape of the cabinet that spirits away internal resonance.

The sphere-tube midrange unit they use on the N800 series is an absolute triumph. Check it out at www.bwspeakers.com

 

[SoundMix]

While B&W makes some super speakers, and has one on my list of all-time favorites, the B&W Nautilus in the picture above does not work for me. The B&W I like is the Nautilus 801, a more conventiional and IMO, better sounding speaker

It is quite obvious that electrostatic speakers do not have sound absortion. However, Definitive Technology and MK dipoles do have sound absorbtion. Did I mention that I hate diopoles used for front channel speakers? They are great for surrounds but not for front speakers. I'm using MK THX for surrounds.

 

[Mike V]

I haven't got Nautalises (I wish).

I've got B&W 600 series. Pretty good sound for the money.

I have seen a pair of Nautalises in a shop.
They look a lot better in real life than they do in the pictures.
I was surprised how good they looked actually, because they look pretty awful in the pictures.

 

[GarageBoy]

I use sound stop board in my enclosures for my TAD 1602s

 

[TedTheLed]

does BW cut the snail into steaks after they do that to his shell?

there was a brand called GNP that actually filled it's cabinets with sand...

Jim Rogers JR 149:

 

[Bright Scouter]

I agree with RDH. Klipsch does not use acoustic material in the folded horn part of it's "classic" enclosures. And obviously doesn't in the mid or high horns.

 

[knot]

It depends on the design and the "Q"

Acoustical dampening material is often used to simulate the effect of a larger enclosure - such as a woofer's specification that would call for a larger enclosure than it's placed in.

 

[GarageBoy]

I have an old Tannoy HPD/Arden Speaker system. The enclosure vibrates and resonates. Stuck in some dampening foam and it's all better

 

[greenlight]

very interesting thread.

 

[Monolith]

I always peak inside speakers when I visit audio shops. Most of them do not have any acoustic insulation inside. I remember reading an article in an audio magazine about building speakers out of cinder blocks. Im searching for it.

I don't think actual building blocks would make good speakers. Were you referring to using cement to make speakers? If so, here's the link:

Concrete Speakers

The best imaging speakers I've ever heard are actually made from granite resin.

Caravelle