What shall I do with this win?

[Paul Barker]

http://cgi.ebay.co.uk/ws/eBayISAPI.d...B:EOIBSA:UK:11


SEAS 25 F-EW. 10" paper cone bass driver

HD 13 D 37. Two AUDAX

Crossovers have built-in rotary potentiometers for adjusting the mid-frequency and high-frequency response of the drivers.


I couldn't resist it, price was a steal.

I liked the bass Peter got from the woofers at phono shootout, though I know he has a special cabinet design.

I was wondering what I should do with the combination. Presume the tweeters and crossovers are fairly OK for the woofers.

Bear in mind I have redundant Scan Speak tweeters from the aroel and I do like those tweeters very much, though don't like them going too low i.e. 3.5khz is I fell a little low for them, they distort.

I also have ribboins which I can't find a use for yet.

I know Peter would help me out in private over this but I thought it might be OK to discuss openly, knowing from my end comes total ignorance.

[petercom]

This is not quite the same unit as I used in the WD25A, but the characteristics are not too dissimilar. I used a similar unit in the Heybrook HB3. Suits a closed box as it has a nice low fs (26Hz) and Qts (0.35) is in the right region, but the latter is also suitable for the aperiodic design of the WD25T, so you are welcome to use that.

The HB3 was a 3-way, and you can do the same with this little lot. The HD13 D37 is a classic dome midrange with a lovely lower treble up to 13kHz. The treble units look like Audax HD12x9D25, which I used in the HB2. Very nice performance with the right crossover.

[Scottmoose]

I can't speak for the midrange and tweeter, still less the crossover, but you could also try a TL, so here's a quick first pass at a classic variety, with a 3:1 taper, partly generated in Martin King's alignment tables, and partly in his TL Offset Driver MathCad worksheet. It's a hefty cabinet I'm afraid. I thought I'd throw this into the mix for discussion / interest anyway, for sake of variety.

So (sealed end) =2.25Sd. For this, you'd need an area of approx 10in x 12.5in.
Sl (terminus) =0.75Sd.
Line length 89in (35Hz line for a 3:1 taper ratio)
Driver offset 0.336 of line length (taken from So, so driver centre 29.9in from the sealed end)
The de rigure 0.5lbs ft^3 of stuffing used throughout. You can get a 2-3Db boost below 100Hz by only stuffing the first 2/3 or so the line, where it will only attenuate the amplitude of the unwanted higher harmonic resonances.

Best
Scott

[James D]

I had suggested to Paul that a MLTL would suit this driver if Peter's aperiodic scheme didn't appeal. Nice to see such low ripple from the sim too

What do you think of a TQWT for this one too?

It looks like an on paper match for the Decca Ribbons - as long as its tone matches and it is fast enough to mate through the cross over region. Peter might have an opinion on that...

James

[petercom]

It is worth a try, but the early cone break up at 400-500Hz means the midrange isn't ideal as a crossover to the ribbons, and you can't use it above 2kHz anyway. Best as a 3-way methinks, the HD13D37 domes should suit the ribbons with crossover points of 800Hz and 5kHz.

The reason the TL simulation shows little ripple and good extension is the Qts at 0.35 is in the perfect region for a TL. Would be a very big box, though.

[Scottmoose]

Yeah -assuming 3/4in material, and an internal width of 10in, you'd be looking at an enclosure with an external depth ~18.75in. Nothing really...

A straight MLTL is my favourite option. Here's one I tried in a sim. It's too flat at the moment, but could have potential.

Height: 45in
Width 10.5in
Depth 12.5in
Zdriver: 15in
Port centre 3in up from the internal base. 4in diameter, 5in long.
Stuff 0.25lbs ft^3 of hollow-fibre from the top of the line 35in down.
Methinks bracing might be a good move with this one...

Same goes for an ML TQWT. Rough dims I checked were
60in tall,
12.5in wide.
2.5in deep at the top,
14.5in deep at the base,
Zdriver 30in.
Same port placement and size as before.
Again, it's way too flat at the moment, and nothing like as good as what you could do Peter, but they might be of interest. First plot is the MLTL (considerably more managable in size), second the ML TQWT.

Regards
Scott

[vitalstates]

Hi Paul

must be bargain of the year, congrats. Those tweeters look suspiciously like scan speak, are they???. If so its a double bargain.

Ed

[petercom]

Scottmoose - what is this MLTL business supposed to be other than a damped reflex box?

Vitalstates - I think you are looking at the midrange units! The domes are 37mm diameter. Both these and the HD12x9 treble units are Audax, as described.

[Scottmoose]

I don't pretend to be any form of an expert in the physics, but as I understand it the restricted air-mass in the vent provides an additional load on the 1/4 wave resonances generated by the enclosure proper, lowering the first QW mode. I seem to remember Greg Monfort describing them in a different way as two summed resonant structures, a 1/4 wave and a 1/2 wave combined to create a hon-harmonic resonant structure in its passband.

Perhaps people are looking at the same thing from different angles -what's one man's MLTL could be another man's damped BR enclosure? Whatever you call them, they work.

Regards
Scott

[Paul Barker]

Thanks all,

I'll take all your points on board when they arrive. looks like some interesting drivers then.