the speaker quest/dream

[Pharos]

And ported.

[smithie]

this sealed design uses ...

"Each cabinet uses 3.5 pounds of Acousta-Stuf internal fill. Use 3 pounds in the main woofer chamber and ½ pound in the midrange chamber. You should also line the rear wall and side walls of the cabinet with acoustic foam sheets"

so should have afew options regarding fine tuning the final sound,of course having to many options can drive a man to drink and sleepless nights too,but im already there on that

[smithie]

one thing i have noticed is that you cant get 19.1mm mdf over this side of the pond...18mm seems to be the thing here.
dont really understand the use of acoustic foam sheets being used...surely when there stuck on to the walls of the cabinet that will eat up some of the internal volume..more reading i guess

[RothwellAudio]

dont really understand the use of acoustic foam sheets being used...surely when there stuck on to the walls of the cabinet that will eat up some of the internal volume..more reading i guess

The air inside the cabinet acts like a spring. Imagine putting your finger over the end of a bike pump to block it and pushing down on the handle - it feels springy. A larger volume of air acts like a softer spring. Replacing some of the air in the cabinet with suitable materials will soften the spring even more, as if it was a bigger air-only cabinet.

[smithie]

hi andrew
thanks for the explanation,i pretty much understand that from past build and experiments,but you explain it really nicely.
i was thinking this acoustic foam sheets they were talking about for this speaker build was like a solid thick affair(like deflex panels...if anyone can remember them...are they still about i wonder?)thats why i thought it would "eat" into the cabinet volume,but seems that's not the case,i still think i will go with some sort of bitumen type panels to help quieten things down...lots of ideas and thoughts swirling around in my head at the moment,along with a fair percentage of wine

[Macca]

I used Deflex panels on some ported speakers instead of wadding them. They are very good. Also irresistible to touch. A really weird material. I don't like wadding at all, having tried my original design with and without, I preferred without. So I was determined not to use any in the second build.

Last time I looked Deflex don't seem to be going anymore but you could get something the same somewhere I suspect.

[smithie]

I used Deflex panels on some ported speakers instead of wadding them. They are very good. Also irresistible to touch. A really weird material. I don't like wadding at all, having tried my original design with and without, I preferred without. So I was determined not to use any in the second build.

Last time I looked Deflex don't seem to be going anymore but you could get something the same somewhere I suspect.

yes,i certainly remember them having a weird feel about them that was quite addictive
its funny how things seem to come and go,i remember having some good results with them in afew speakers....so remember cutting some up to glue to the back of speaker drivers in my quest to leave no stone unturned,or to cover every square inch of said speaker internally with deflex panels...probably why im skint now...bloody expensive from what i remember
think im gonna make the back panel in my design removable,just in case i want to get serious and play again with the tweaking side of things.

[fatmarley]

If you use BAF stuffing you can increase the effective volume by up to 40% as well, or use this effect to reduce the box size.

Sorry to be pedantic but this Isn't true (I bet people are thinking "Oh no, not that know It all ba***ard again). Adding stuffing lowers Qtc and Is good for reducing the bass hump you get with a box that's too small for the driver. A bigger box will have a lower Qtc and also more low frequency extension, but with reduced SPL potential at the lowest frequencies.

[Pharos]

From the many reference books on the subject of speaker design, it is true Matt, and I'm sorry but I rather accept the opinions of professionals and academics in the field.

There are two major aspects of taming cabinets, absorbing energy from the panels, often done with bitumen which dissipates it as heat, and lead sheet has been used, and damping the energy flying around in the cabinet.

A lining of BAF or foam will help to absorb M. Freqencies, and stop them re-exiting through the port or speaker cones. In a well designed system there should be no need to dampen the fundamental resonance at bass F's, but absorbing internal MF's is desirable.

What you state is mostly right, but there is effective increase in volume due to the inclusion of internal absorbtion material.
Martin Colloms is one reference stating this.

[fatmarley]

What I said was a fact, not an opinion. It can easily be modelled in software.