Building speakers

[jtbo]

I have some old speakers with Philips logos, frame is wood and elements are pretty much failed as those are from beginning of 80's, for example rubber at edge of cone transforms to dust when touched.

I understand next to none about speakers, well only that current speakers are 3 way with 8 inch bass element.

What I plan to do is to get new 8" element and new high frequency element, then install reflex tube to speaker frame. Oh yes some splitting filter is going in too.

I came to think about that speaker frame (or is it box, chassis?) is quite light and thin wood so probably I slap some sound absorbion sheets in, maybe even some rock sheet to outside + nice painting, but let's see now.

But as I don't know much about speakers, I'm now in doubt that would it be good to put that sound absorbion material into speakers or should inside surface have some reflective features?

Reflex tube I'm going to use is around 2" in diameter, can't really say anything about what would be correct sizing, or any audio specific stuff in that matter, dimensions of speaker frame are around 18"x6"x10".

8" elements:
http://www.ljudia.fi/Product/Product.aspx?id=78482

Higher frequency elements:
http://www.ljudia.fi/Product/Product.aspx?id=78543

Splitter Filter thing:
http://www.ljudia.fi/Product/Product.aspx?id=79421

I'm trying to go low budget route but still getting best possible for 100 euros / pair and those are what I came up with, maybe bad choices?

No need for Hifi for golden ears as my ears are pretty much made from pottery when it comes to estimating sound quality so can't see point spending several hundreds to such thing, but still would be nice to avoid total crap

Edit: These are not for car, for computer so I can hear Schubert again There is also sub coming, 12" or something like that it was, that I get free.

[tommysb]

In hifi, the less the enclosure resonates, generally the better. Also generally, some form of absorption is put in the speakers to minimise reflections between parallel faces, and also makes the space seem acoustically 'larger'.
You can port the loudspeakers if you like, the 'Helmholtz Equation' will be useful in working out the tuned frequency of the cabinet if you do this.

I'd say PVA glue some 12mm mdf inside (or outside), flat to the face of the existing speaker walls, to stiffen the cabinet. Ruffle up some felt and staple it inside, so it occupies a bit of volume.

Tune the cabinet to around 50/60 hz for perceived 'BOOM'. With a 20L Cabinet, and 2" tube, this tube should be about 6.25cm long. What I would do, is start with the tube a bit longer, assemble the speaker, and have a listen. It is easy to reduce the tube length (if the tuning is too low), but more difficult to increase it!

Have a listen.

And one of the greats of acoustics, Leo Beranek, remarked,

Beranek's Law

"It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion."

[jtbo]

Thx from tips!

I did some googling, came up with site where I can calculate stuff, based on calculations I think that my speaker box (found word for it) is bit small, to make it sound nice and good, I would need to separate high and low sections, but by doing so I will get bit too much bass sound, so I guess that I have to leave inside of box to single space.

Double checked measurements and data, I have actually 5.5cm (2.17") diameter reflex tube that is 12.9cm (5") long, and speaker box is 47 cm (18.5") x 27 cm (10.63") x 24 cm (9.45"), my memory is not perhaps same as it used to be when I was young lad

Anyway, I did bit of calculations so here are some results:


Green line is for Vented with that reflex tubes I have ordered, purple line is without tube.

I plan to use quite low volume levels, so I guess that I go with vented route as it helps at least a tiny bit with low sounds disappearing because of how ear works, but I will have also sub, so I don't need much of boom from these.

URL where calculations can be made:
http://www.linearteam.dk/default.aspx?pageid=isdonline

I guess there is now rough quideline how to proceed with build, if in testing there is too little boom, I can always cut reflex tube bit shorter and that should give more boom at cost of lowest end silencing, but I don't know what use there is with those last 100Hz, surely subwoofer should handle those if I can ever even hear such low sounds

It could be that I do sheet rock surface for speakers at some point, that is then easy to paint to make look good, sheet rock is rather heavy 16.8kg/sq meter so it should make speaker box to settle in terms of vibrations quite well, -40db sound dampening material should handle inside reflections rather well, just need to figure out how to dismantle speakers without causing too much damage.

Someone else's sales ad had photo of very same speakers that I'm about to fix, if I fail, that is perhaps not too great loss to world of speakers :

[jtbo]

Bit of soldering, bit of sealant/glue and I have now working speakers.

Incredible clear sound, also very good stereo effect and these seem to work really low if needed, very happy

Only thing is that my amplifier is not best of the best, it is Philips unit from early 80's and there is bit of hiss (a lot actually), but compared to earlier soap boxes sound is really good.

However these things take fairly huge amount of space from my computer desk, as much as triple 19" monitor setup would take

[tommysb]

Incredible clear sound, also very good stereo effect and these seem to work really low if needed, very happy

Beranek's law at work there!

What did you aim to tune them to? 30Hz? That's more than adequate for most recorded music, sounds like you done good!

[jtbo]

Beranek's law at work there!

What did you aim to tune them to? 30Hz? That's more than adequate for most recorded music, sounds like you done good!

45Hz, physical limitations did cause that I could not get any lower than that, 35-40 not much of reason to go any lower as low end of element is 35Hz.

edit: Oh yes, Beranek's law indeed, I have no any real idea if these do sound crap or godly, but compared to old plastic boxes these are godly