audio-talk

I have been offered a pair of these at a good price.https://www.falconacoustics.co.uk/downl ... asheet.pdf.

I cannot workout how best to use them though as a subwoofer.
I know these are used in the Linkwitz OB speakers, I don’t have room to have 2m space around them for an OB sub.
In a sealed baffle with a qtc of around 0.3 they look like they would level up with some bass boost to give an f3 of 30hz and an f12 of 20hz.

Maybe not a bargain.. they cannot make this driver just for the Linkwitz speaker can they?

OK a big box but happy to sit close to one wall....

Reflex box but SC4 alignment (Forth-Order Sub-Chebyshev) so not a boom box alignment - good transients
F3 28Hz no peaking so flat to the F3. F12 19Hz. Qts 0.36 so a little overdamped that helps in a domestic room. port 12cm and 16cm deep. Volume 210litres so a box that is 43cm wide by 53cm deep and 91 cm high (internal dimensions ignoring driver volume)...

That should sound nice with Class D 50W-200W amplifier and looking at the plot it would be fine out to 200Hz with a 12dB/octave roll off but I would look to only go to say 80-100Hz max to minimise localisation...

JamesD wrote: ↑Thu Dec 03, 2020 8:22 pm Qts 0.36 so a little overdamped

Qtc 0.36 ?
I had a feeling you'd suggest a big box !

Thanks James. Hmm, so ported in a very big box. The box size is the same size as my current “monsters” which house the 15” Supravox drivers in an aperiodic arrangement, which are good to 35 Hz.

I have found on the web “wolfhorn” a tapped horn that goes to 16 hz with a pair of these drivers in it.... great you may think but it’s 500 ltrs. I would not be allowed a “wardrobe” in the room.

My friend Dave ( golden ears) has a pair of these per channel in his Linkwitz LX521 speakers - they are very capable in the lower registers it surprised me what these drivers in OB were capable of. His room is twice as big as mine and I have never seem the drivers move more than a mm or so, not the +/- 28mm linear travel they claim. But they are not subwoofers.

If they're a good price, I can think of a few interesting things to do with them:

- Tiny sealed cube subwoofers. Throw a load of power in there.
- Medium-sized boxes with a chunky compression driver. ~700Hz crossover. Not particularly conventional, but would be a really cool speaker.
- Big ol' tapped horn, for crazy bass

Wouldn't mind a pair of those drivers. If you decide to pass on them, would the deal be open to others?

Chris

Mark said:

Qtc 0.36 ?
I had a feeling you'd suggest a big box !

With a VAS of 363l it would be difficult not to do a big box! Thats my excuse anyway...

A boom box config (the popular QB3 alignment) would get a small box but to my ears sounds poor... its the typical reflex 'one note' bass alignment when pushed to far but one could produce a box half that size for a 30Hz F3 but its not a nice sound - SC4, or better, SBB4 (even bigger box required) sound much better to my ears and get quite close to a big sealed box sound but with more extension...

I'm not really a fan of small subs driven below Fs with lots of power for music - although they make great HT effects subs ...

They do look like interesting drivers though

Now a bass horn would be very interesting to hear - would need to get the big organ music out!

Not sure where the VAS of 363 Ltrs come from. Spec sheet states 46 ltrs - which was one of my issues to get a flat alignment the box volume was 9 ltrs and the F3 was around 100Hz.

The other version of this driver, without 4 layers of windings.. is easy to sim into a subwoofer, with an F3 of 30hz without any filters. The specs of this driver as I said suggested a very niche market

I have read that one of the first sealed speakers from AR had a driver with a Qts of 0.15 - so am intrigued how they got any bass at all.

Seas recommend using it in a small box with some DSP contouring.http://www.seas.no/index.php?option=com ... Itemid=365

Damn!!!

Sorry misread the line - got the figure from the line above that has Sd at 363.... OK I'll redo it with VAS correct... I'll do it over lunch as busy with work now....

An SBB4 or SC4 looks like 40l ish for around 30Hz F3 and smooth response i.e. no peaking and around 20Hz F12.... wow pretty amazing... Qts around 0.44. I'll get these more accurate at lunch

JamesD wrote: ↑Thu Dec 03, 2020 10:59 pm .... would need to get the big organ music out!

Obligatory Kenneth Williams jpeg?

Dave the bass wrote: ↑Fri Dec 04, 2020 12:02 pm

JamesD wrote: ↑Thu Dec 03, 2020 10:59 pm .... would need to get the big organ music out!

Obligatory Kenneth Williams jpeg?

The "gentlemans sausage" overture ?

Ignoring the innuendos/humour... found a paper about how Grimm Audio do there subwoofer, which uses this driver in a small box, servo control with current amps. https://rmsacoustics.nl/papers/whitepaperMFBdesign.pdf

That Grimm Audio paper is interesting and I would love to hear the end result. I've only heard the Philips motional feedback loudspeakers and I didn't like them much although they were impressive...

The earlier Seas design was more to my taste in terms of design... Although now I've had a look at the beastie in various designs with the correct parameters it is both difficult and amazing...

A conventional SC4 reflex box design yields 15l with a 41z F3 and a 22Hz f12 with no peaking which would probably work well in a room on music as 30Hz is only 6.5dB down so its a nice match for typical room gain and its small - relatively speaking... it gets more interesting if you slug the Qts with a series resistor of 1.2R reducing it to about 0.35 to give an SC4 reflex box 25l, F3 30Hz and f12 at 20Hz but efficiency is low and you need a to step up the driving power to 150W or so - easy enough with a class d amp.

Interesting choices...

When it comes to bass reflex cabinets, the relatively large Xmax of the driver (assuming you're planning on using some/all of it) will mandate a port with a fairly large cross-sectional area. In turn, that means a very long port length.

Passive radiators are a good workaround here.

Chris

My sanity is restored, you getting about the same as I do using a Jeffery’s box calculator. I was looking at going slightly bigger on the box, sealed with a Qtc of around 0.3. So almost getting to the OB loading but without the rear wave to worry about. I would be driving them with some 500watt amps via the DSP, so I can contour the freq response. Other way would be a 500uf capacitor to reduce the top end response.

I have heard the Grimm speakers... they are the best speakers I have ever heard. The imaging was unbelievable. They didn’t have the servo controller subs, just tradition DSP controlled one. If I had £25k spare I would have had a pair. They even have a wireless phonostage for another £6k.

I might bite the bullet... if it doesn’t work out then they will probably end up in Sheffield.