Cheapie Dai-1chi 8" FR driver in an isobarik box?

[Brisso57]

Following up on a previous thread, here
diyaudio.com/forums/showthread.php?postid=271555#post271555

I'm intrigued to know if anyone thinks it's worth trying two of these in a ported box, mounted isobarik-fashion, coaxially, nose to tail, with a small pressure chamber.

What box size?
What pressure chamber size?
Connected in serial? or in parallel?
What port dia & length?
Any benefit in giving the inner unit a whizzer-ectomy?

Recapping the specs:
Dai-1chi SDC8-30 8" unit
Fo 54 Hz
Sens 91dB
30W nom
Qms 2.32
Qes 0.91
Qts 0.65
Vas 47.11 L
Z 8 Ohm Zo 24 Ohm
Sd 0.022 sq M

Any thoughts? javascript:smilie('')

[Geoff H]

Hi Brisso57, They wouldn't be the ones from ebay a few weeks back with the cloth surrounds by chance?

Either way, probably not the best thing for an isobaric sub. I don't think there's much in the Xmax department.

Geoff.

[Brisso57]

Originally posted by Geoff H
Hi Brisso57, They wouldn't be the ones from ebay a few weeks back with the cloth surrounds by chance?

Either way, probably not the best thing for an isobaric sub. I don't think there's much in the Xmax department.

Geoff.

No. They're not. (At least I don't recall that listing.)
I was just wondering if I could get better bass than in, say, a BR box.

Doug

[bjorno]

…… in a ported box…..

Forget a normal ported box.

b

1(2)

[bjorno]

2(2)

[Brisso57]

Thanks a heap, Bjorno! :-)

I'll digest the info you've provided and no doubt I'll be back with questions.

But first up, in such designs, what is the practical way of reliably separating volumes of differing density?

cheers,

Doug

[bjorno]

what is the practical way of reliably separating volumes of differing density?

Hi Dough,
I use insect screening net with similar mesh size like:

http://www.diyaudio.com/forums/showt...90#post1171590

The divider damping purpose is smoothing the dip at about 125 Hz and is not critical at all; I doubt you will hear the dip at all if left out.

This box should be designed as a very loosely filled box (acoustic compliance of the box paralleled acoustically with an acoustic resistance), i.e. ported (acoustic résistance, no mass) with the inside rear wall covered with ¼” felt or foam and only the external port is critical stuffed to convert.

The aperiodic external port is 1/3 x Sd = minimum size and can be made larger but I prefer this enlarging only if the air velocity is too high.

Small named this box type to The Leakage-damped Closed-box System, B3 aligned and is probably the easiest method to tame high Qtc for a WR or FR enclosure with high driver Qts besides the more difficult but superior Driver Qm damping method that also saves full bandwidth when done right.

b

1(1)

[bobhayes]

Straight from the Wagner catalogue? I have 'em highlighted!

I would be keen to pick up a pair (or more) of the drivers to mess about with.
How much are they? My catalogue has no prices in.
The information published shows a nasty peak (typical) around 2 - 3kHz, with falling response there after. Might stick a little tweeter in the mix for the sparkle.
I am thinking of mounting on open baffle maybe.
Keep us updated with your ideas and results.

[Brisso57]

Originally posted by bobhayes
Straight from the Wagner catalogue? I have 'em highlighted!

I would be keen to pick up a pair (or more) of the drivers to mess about with.
How much are they? My catalogue has no prices in.
The information published shows a nasty peak (typical) around 2 - 3kHz, with falling response there after. Might stick a little tweeter in the mix for the sparkle.
I am thinking of mounting on open baffle maybe.
Keep us updated with your ideas and results.

You can get them here
www.digitalmegahouse.com.au/speakers.html
which is where I first saw them.

I, too think that I'll try them first on an open baffle ... because I have two sheets set aside to try with another pair of drivers in any case. Serendipity!

I'll likewise keep reporting back ...

Doug

[Geoff H]

WES May 2005 catalogue lists the DC8-30 at $14.50. For OB use, look at the DC65-30 with a bass helper.

And this looks like the RS - Foster 4" dual cone, complete with cloth surround. 8ohm version in the WES catalogue.

http://www.digitalmegahouse.com.au/dc4-40.html

WES still don't have prices on the site.
http://www.wagner.net.au/Catalogue/wagner0020.html

Geoff