Sound dampening foam, is it needed?

[MissileCrisis]

Hey so this is in reference to my other post about designing a 2-way bookshelf speaker. I've looked at what bassbox says would happen if I line the inside with foam and it doesn't seem to make much difference (positive or negative) However, since I'm not modeling the tweeter at the moment I was wondering if this foam stuff would have a significant impact (good or bad) on the >2.5k range. Here is an example of the material I'm talking about: https://education.parts-express.com/aco ... 4--260-515

I am porting the box and I'm ok with the tuning frequency I've selected so I'm really just looking at how it affects higher frequencies, if at all.

Thanks.

[Bill Fitzmaurice]

Hey so this is in reference to my other post about designing a 2-way bookshelf speaker. I've looked at what bassbox says would happen if I line the inside with foam and it doesn't seem to make much difference.

That's because bassbox, and all programs, don't show what happens in the midrange. Cabinet damping is absolutely mandatory. Failure to do so will result in reflected waves going out the port and also going back to the cone, causing major peaks and dips in response.

[MissileCrisis]

What kind of dampening would you suggest? eggcrate foam or pillow stuffing like in the TLAH? Or polyfill?
Also, how does varying amounts of the stuff affect the midrange?

By the way, thanks for the quick and concise response, I plan on ordering some polyfill because it is a known quantity.

[Charles Jenkinson]

This is all the realm of speaker design know how, and how one ought to progress from less to more know how, which I am not really sure of because i havent done it. One of my initial thoughts is have you considered joining the AES?

[MissileCrisis]

This is for said AES, and no one that I've met in the club knows how to design speakers. I acknowledge the fact that sometimes a lot of sound design is trial and error but I'm trying to limit the waste as I'm on a bit of a budget.

[Charles Jenkinson]

That's a bit of a surprise - the club can't design a speaker. Is it full of wannabe's, with some gracious degree of access to a load of technical papers they have neither read nor understand?

Learning how to model the skills and attitudes of people who are great is the key. ...this is what i mean: http://nlp-mentor.com/nlp-modeling/

I'm waiting for Bill to bring out his autobiography. I can only imagine what may be in it.

[Charles Jenkinson]

FWIW Will, I want you to do excellently.

I tried designing the only bass guitar cab I ever made 20 years ago, using Vance Dickason's Loudspeaker design cookbook. A simple ported cab, and his method suggested a port about 8 foot long at 4" diameter. A friend had a look in the book and also got the same answer. I figured what the hell (...no, it was probably worse than that) and built a design someone else gave me.

[Bill Fitzmaurice]

I acknowledge the fact that sometimes a lot of sound design is trial and error

It shouldn't be, considering the knowledge base extends back 80 odd years. If you haven't found the answers you haven't been looking in the right places. Like here:
http://billfitzmaurice.info/forum/viewforum.php?f=18

and here:
http://techtalk.parts-express.com/showt ... ding-Bible

One of my initial thoughts is have you considered joining the AES?

I did, in 1998.

[MissileCrisis]

When I said AES, I wasn't referring to the Nationwide organization, I'm sure they would be a good resource, I was more referencing the club at my school, of which is more focused on audio electronics than cabinet design. Thanks for the links, I'll look into them.

Has anyone here had a PCB fabricated for a custom crossover? and if so what would be the cheapest one if I'm only interested in large through-hole components.

[Michael Ewald Hansen]

When I said AES, I wasn't referring to the Nationwide organization, I'm sure they would be a good resource, I was more referencing the club at my school, of which is more focused on audio electronics than cabinet design. Thanks for the links, I'll look into them.

Has anyone here had a PCB fabricated for a custom crossover? and if so what would be the cheapest one if I'm only interested in large through-hole components.

If you just need a simple 2 way crossover - why not just order one premade?

[MissileCrisis]

The drivers I'm using (after the fact) need a custom crossover point to mesh the best and avoiding destroying the tweeter/nasty woofer off axis response. Looking at the charts I've chosen 2300 Hz 3rd order butterworth. Does parts express have blank boards predrilled for specific types of crossovers? I don't believe they do...

Also, I was hoping to sign the pcb since it is hopefully going to be a kit.

[Michael Ewald Hansen]

The drivers I'm using (after the fact) need a custom crossover point to mesh the best and avoiding destroying the tweeter/nasty woofer off axis response. Looking at the charts I've chosen 2300 Hz 3rd order butterworth. Does parts express have blank boards predrilled for specific types of crossovers? I don't believe they do...

Also, I was hoping to sign the pcb since it is hopefully going to be a kit.

I didnt mean the whole crossover - just buy a premade pcb if you just need a simple 2 way crossover

Something like these:

http://www.erseaudio.com/Products/PCBoards

[MissileCrisis]

Thanks for that link, I'll probably go with something of the sort.

[Hackomatic]

If you are really feeling ambitious and want to custom tailor it, and depending on how many you order, here is a place I've used several times for designing, prototyping and mass producing various projects . .

http://pad2pad.com/

Superb quality with quick turnaround . . . NAYYY

[Ian Westwood]

Eminence Has a speaker design software program.

The software itself is an abomination and even needs the CD rom to function... and only worked on 1 of my 4 PC's... and the support people suck giant donkey balls. Hopefully they wind up reading this...

YOU SUCK!!! ...... BIG HAIRY DONKEY BALLS!!!

But once you get past that and start to dig a little I found it really useful in terms of understanding some of the intricacies of speaker design.

You can add and take away dampening foam and see what effect it might have on response.