Mark's new Alpair 12

[Jozua]

Gm

I am referring to the new fullrange Tangband driver you reviewed so favourably.

This new driver might be a better long term option, especially if there is uncertainty re the availability of the Jordan driver.



Regards

Jozua

[GM]

Greets!

OK, though I didn't review it as such, only expressed some opinions based on its published data. I'm confused though, did you mean the questionable availability of the TB driver?

GM

[Jozua]

GM

I am under the impression that the Jordan driver was hard to find.

I was tempted with the TB driver but I suspect the Alpair might be better option. It would become much more attractive option when I know there is a enclosure design available that will extract the very best from the driver.

I just want to do a single build and get the best from the driver.


Regards

Jozua

[Scottmoose]

Just a reminder -extracting 'the best from the driver' is system / room / requirement dependant; 'best' unfortunately is an arbitary term at, er, 'best.'

[markaudio]

Hi Jozua,
Scott and me have been working together on a easy-build plan that sort of follows on from Pensil-70, a TL that was originally designed for the CHR-70.

This Scott-Pensil 12 isn't finished but here's the outlines to give you some idea. It's just under 1000-mm tall so should fit into most living spaces. More details on this to follow soon.

Thanks

Mark.

[Jozua]

Mark

I am beginning to consider using two drivers a channel with a meter long ribbon on the side for a virtually crossoverless speaker. Hopefully two drivers will allow a more realistic volume level.

I am looking forward to your enclosure info.

Regards

J

[GM]

Originally Posted by Jozua

I am under the impression that the Jordan driver was hard to find.

I was tempted with the TB driver but I suspect the Alpair might be better option.

OK, I'm still confused. The only Jordan I've auditioned is the JX92S, which isn't a direct competitor to either the 8" TB or Alpair 12 since it has by far the smallest radiating area (Sd). I haven't been able to follow the forums for awhile now, so not aware of any potential long term shortage of it other than what some folks appear to believe I'm capable of causing. All I've read is that the measured specs of some recent units were way out of published spec, so may not perform as well in my designs as Jim Griffin's older units I auditioned some years ago do.

What Scott said WRT extracting the 'best' out of a driver, but from a purely box loading POV, 'best' for a wide BW app will always be either OB or reactance annulled compression horn since a point source driver wants to 'feel' a matching acoustic impedance [load] on both sides of its diaphragm.

From a purely T/S specs POV, there's two basic 'controlling' scenarios, predominately electrical or compliance, so with the TB's better balance of Fs, Vas, Qts it offers more system alignment flexibility and low power detail potential.

Obviously, there's more to this 'story' and where the 'art' of driver/speaker design comes to the forefront, i.e. keeping from 'bouncing' off the 'wall' of science as the inventor Tom Danley periodically opines and the myriad design trade-offs it implies that for now only experience can teach.

GM

[markaudio]

From a purely T/S specs POV, there's two basic 'controlling' scenarios, predominately electrical or compliance, so with the TB's better balance of Fs, Vas, Qts it offers more system alignment flexibility and low power detail potential.

Hi Greg,
I take issue with this comment.

I disagree with your assumption on the balance of Fs, Vas and Qts will "deliver" better performance. T/S aren't a "universal" indication of a driver's performance. There are a number of drivers that on paper should perform, but are compromised by their design, materials used, component selection and a wide production tolerance variance.

I've put much effort into the Alpair 12's design to deliver detail and dynamics across its range. The Alpair 12 is a single cone/cap design. For a driver of this size, it's rare (possibly current production unique) to have full range delivery with no use of whizzers, phase plugs and alike, all of which have significant design, production and performance compromises.

It will be interesting to see what future Alpair 12 users get from this driver in the way of performance and the utilised box designs.

Mark.

[markaudio]

Hi Guys,

Talking of box designs, here’s the first Alpair 12 idea from Scott, initially from early discussion related to my Pensil-70 (for CHR-70).

Named it the “Mark-Scott Pensil 12, It's can be described as a “Damped Air Coupler” it hasn't seen the light of day for years, this design has drawn its inspiration from the concept of LF air-couplers, some of which were built under floors back in 1950s - early '60s America.

Here’s a brief summary of Scott’s comments as he worked through the design:

Strictly speaking, this is a pre-T/S alignment BR, reduced per the original methods by 25% to make for a more manageable box. Because modern drivers like the Alpair 12 aren't a natural match to this sort of alignment, to compensate it’s stuffed like a TL.

I'd expect 0.5 - 0.75-lbs ft^3 of hollow-fibre pillow stuffing to be optimal, depends on the amp as well as taste.

Scott’s offered to expand on this concept when time permits, so keep a look out for his post of this thread.

It's a nice simple build, with a removable back panel making it ideal for experimentation and adjustment to suit a particular room situation and personal taste.

I've suggested using 20-mm MDF or Marine ply as a minimum thickness, feel free to use thicker as desired.
Cheers,

Mark.

[Scottmoose]

There isn't a great deal to say TBH. It's just a traditional bass reflex cabinet stuffed so it works properly with contemporary drivers like the Alpair 12 with their high-damping & low compliance. Should be ~flat to 60Hz & a nice unreactive impedance, so most amplifiers should be happy. Bit of a flavour of a (large) vented alignment (I do like big boxes) & a TL. I thought doing something a bit different might be fun.

Re the T/S specs. thing, I don't think GM was implying they're the be-all & end-all, let alone in terms of a driver's 'sound'; it's simply that some drivers are slightly easier to work with in a wide variety of loads than others. That doesn't necessarily mean they sound any good of course; as he says, there's a lot more to speaker design than just T/S specs.