Have drivers - Need box

[Pano]

Looking for ideas.
I have a pair of lovely old "Voice of Music" 8" full range drivers from Denmark. Probably Philips made. I'd like to figure sort what sort of box to put them in.

They had been running on open baffle with a helper woofer and I liked the sound of them. But I want something simpler, like a MLTL or such. Size is not much of an issue, but I don't think a BIB will work, as my ceiling is too high.

Below you will see the drivers and here are the specs as I measured them:

Re____8.54
Fs____77.4
Qes___1.41
Qms___4.84
Qts___1.01
Vas___36L

Anything other than OB for these? Any ideas? Thanks.

[chris661]

Looks like a high Fs, so you may be looking at a transmission line, or some kind of horn. They are both used (more TL) for smaller, higher resonance drivers, so a larger version may work here.

I am writing from only what I know about these (which is very little), so you shouldn't take this as 100% certain. Get the opinions of others aswell.

Chris

[EC8010]

Oh dear, with a Q like that it looks like open baffle. Of course, you could always resort to electronic trickery and make an amplifier with a negative output resistance to reduce the Q. It would probably oscillate, though.

[Henkjan]

I'd say a TL tuned to ~50Hz should be fine

[ttan98]

Panomanaic,

Are you still interested in pursuing the modification of the Sure Electronics TK2050 amp. and present your mods on this forum?

Just asking.

[Pano]

Thanks guys. Yes - high Qt, high Fs. The drivers were probably in some open back radio or console. They did work well on OB - with a woofer.

They may not be much good for anything else, but I was hoping. They are a rather nice exended midrange driver.

[GM]

Greets!

Well, the obvious is sealed, so ~137 L for a Qtc = Qts alignment or a max flat impedance TL with more gain in the driver's box BW for some acoustic BSC, though at an increased box size of ~180 L. With only a ~ one octave (55-110 Hz) box gain BW it seems hardly worth the $$/effort to build a pair of ~430 L corner loaded cabs to get it, so by the same token, a typical BIB style pipe horn is a poor choice also.

It would be efficient though at around 110 dB/2.83 V/m, so a lot to bleed off to match its point source radiation, but if you ever decide you want a ~113 dB efficient ~flat to 40 Hz (depending on room construction) bass horn for a < 200 Hz XO, use both drivers in it with a high order slope.

A MLTL theoretically wants a ridiculous ~834 L/30 Hz 'one note' alignment with no driver protection, but I found high Qts drivers respond well to pipe loading if a classic baffle layout is used, i.e. one where the vents are near the driver, so using the same Vb as a Qtc = Qts sealed alignment and a tuning around an octave below Fs or ~137 L/39 Hz may work once properly damped:

L = 59.06"
CSA = 141.6"^2 - wider the baffle the better to reduce the need for BSC
zdriver = 21.91"
zport = nominally at 21.91" - recommend one vent at each quadrant as close as practical to the driver's frame without touching it

dport = (4) 4" dia. tubes
Lport = 4"

All dims i.d. and approximate. In such a layout, the response's smoothness/extension is almost solely based on the stuffing density between the top down to the top of the driver with just enough around the driver on down to keep panel reflections from modulating the driver and quell any pipe 'hollowness', so just one side and back should be lined to 'taste' IMO.

Again, since the initial stuffing density sets the effective vent length, then if once smoothed to 'taste' it can't handle a low E bass fundamental without overdriving it, then try up to 7" long vents.

GM

[Pano]

Hey GM _ thanks. Let me mull that over. Might be just what the doctor ordered.

Do you have any links to a similar layout that I might look at?

[GM]

You're welcome!

If you mean the driver/vent layout, it's been a common HE prosound layout when an ultra large vent area is required since the bass reflex was patented (see A15): http://www.lansingheritage.org/image...ro/1993-36.JPG

Anyway, hope you at least cobble together a proof-of-concept and get back to us as the ones I built were so long ago and for relatively non discriminating listeners that while my memory is that they did fine in a typical room near/at a wall with SS driven vinyl, decent CDs with their greater dynamics work a speaker harder and folks around here are a tough crowd to please.

GM