Wharfedale Evo2-8 cabinet lining

[nogaro]

Just for a lark, I opened up my Evo2-8 bookshelves (ported) and was surprised to find here was no lining on the inside walls of the cabinet whatsoever - they do have, what appears to be a coarse wool-like material, around the woofer itself. I've done some reading on this, but still have the following questions and would greatly appreciate more edification on this subject.

-What is the impact to the sound of the walls not being lined? Some people seem to think it's sacrilege to not have them lined.
-Should I decide to line them, what lining should be used and why? As in what are the acoustic advantages/disadvantages of a particular material. There are times when I find them sounding a little harsh (especially when compared to the pioneer sp-bs41-lr running on the same receiver).

Thanks in advance for your responses.

 

[zieglj01]

It comes down to the decision that the engineer/designer did make
in the completion of the speaker. I tend to see less lining/stuffing
inside curved cabinets. You may do more harm than good, if you add
more stuffing - it effects the volume and loading of the woofer. Also,
it can play against your warranty.
You would be surprised to know, that the Pioneer SP-21, is lined with
only 1/4 inch of pollybatten, and no middle stuffing.

 

[nogaro]

Thanks for your response, Jim. Is "stuffing" the same as "lining" as far acoustic impact is concerned? Based on information I've read, people tend to talk about lining cabinet walls (minimal volume impact), but stuffing subwoofers (larger impact on volume). I haven't looked inside the pioneers yet, but it would certainly be interesting to see the differences. Thanks again!

 

[TLS Guy]

Just for a lark, I opened up my Evo2-8 bookshelves (ported) and was surprised to find here was no lining on the inside walls of the cabinet whatsoever - they do have, what appears to be a coarse wool-like material, around the woofer itself. I've done some reading on this, but still have the following questions and would greatly appreciate more edification on this subject.

-What is the impact to the sound of the walls not being lined? Some people seem to think it's sacrilege to not have them lined.
-Should I decide to line them, what lining should be used and why? As in what are the acoustic advantages/disadvantages of a particular material. There are times when I find them sounding a little harsh (especially when compared to the pioneer sp-bs41-lr running on the same receiver).

Thanks in advance for your responses.

I think those are ported speakers.

In a sealed speaker, the interior has to be heavily stuffed with Poly Fill.

On a ported enclosure, filling is usually no more than 50% of the surface to none.

As you add stuffing you progressively damp the box resonance Fb. At some point Fb is killed entirely and you have no port output to reinforce the woofer. At tuning most of the output is from the port and not the woofer cone.

 

[zieglj01]

Thanks for your response, Jim. Is "stuffing" the same as "lining" as far acoustic impact is concerned? Based on information I've read, people tend to talk about lining cabinet walls (minimal volume impact), but stuffing subwoofers (larger impact on volume). I haven't looked inside the pioneers yet, but it would certainly be interesting to see the differences. Thanks again!

It still goes back to the design as a whole - and some of this goes
back to diy vs retail design speakers. A good engineer should know
what they are doing, and they use measurements.
In ported designs, some line the walls to tame reflections off the
walls. Some use polyfill to tame standing waves - some use both.
I really look for the sealing of the inside walls, and cabinet bracing.
Cheaper designed speakers for the most part, do not use the cross
cabinet bracing.
You can find lots of interesting things inside speakers. The origional
ported Alpha speaker 6 1/2 two way speaker - only had a 1 inch sq
block of fiberglass on the bottom of the speaker. The early Titan by
Paradigm had a 4 inch block of fiberglass behind the woofer. Some
JBL speakers, lined the top, bottom, back and sides with fiberglass
on some - while on the HLS speakers, just the top, bottom and back.
Definitive Tech used foam on the Celsius, for the whole inside of the
cabinets, one inch from the top baffle. Boston tends to put polybatten
behind the woofer on many of their designs, and on the top back wall.
You see differnt things in differnt designs - Focal used thick felt-batten
on the top, bottom and sides of the 705V. Also, I have seen Acoustic
suspension speakers, that were less than half full of polyfill - some of
the early designed, Atlantic Tech speakers.
If you want to play - then buy some cheaper speakers and have fun.
Look at the Polk Monitor speakers from NewEgg

 

[nogaro]

Thanks TLS Guy and Jim. Your responses are very helpful and certainly provide food for thought (and play). I'm trying to educate myself on what parameters impact the "voicing" of a speaker and what, if anything, one can do to alter voicing in after-market situations. If either of you know of any resources online that I might find useful, please do let me know.