Lowther

[3DSonics]

Hi,

Which are good drivers are to use?

THAT depends entierly on use.

As a rule, drivers with a Qt much below 0.4 are best suited for Horns, if they show an additional Midrange/Treble rise (like many fostex and all Lowther drivers) they may be best suited for front horns or Olson compound horns (which load both rear and front of the driver)

If the driver has a Qt around 0.4 it would be best suited to a Reflex enclosure or overddamped sealed enclosure. Any rising midrange may have to be equalised.

If the driver has a Qt above 0.4 it is best suited to sealed boxes with around 0.5 to 0.6 Qt starting to sugest dipole (open baffle) operation.

Then there are of course "multiway through the backdoor" systems. A typhical approach is called "FAST" (Fullrange And Subwoofer Technology". Here you select a driver with a reasonably flat response but obvious bass defficiency, place it into a small sealed enclosure, add a 1st order highpass at or below around 250Hz and add a woofer cabinet below, active, passive, as you like, generally with a suitably tuned 3rd order lowpass and matching sensitivity or the sensitivity matched through active means.

A variation on FAST is what I call D^3L^2QD (Dee Cubed El Sqared QueDee), where a very low Q Fullrange or wideband driver is mixed in the same enclosure with a high Qt and higher Fs drivers which also operates into the lower midrange to balance out the rising midrange response of such drivers. With well selected "helper woofers" a crossover may be unneccesary, otherwise a lowpass is needed on the High Q fill in helper.

Other optiosn exist across a very wide range of possibilities.

So, first define your goals and the select.

Otherwise it is like asking: what is a good motor vehicle?

(Hint, anwer is "A tank", in london traffic anyway. You know, just point it in the direction you want to go, floor it and use the gun to clear overly rigid obstacles)

Ciao T

 

[horninfected]

Interesting point of view there. Ive been invited to listen to some lowthers so that'll give me an idea. At the moment I wont be using lowthers, Ive decided to build my first example using fostex 207e's, their latest 8" full range driver, this is getting very good reviews from users in the US and seems to be a much easier driver to work with and alot cheaper. Im pretty sure I wont be using a hord design at all, there appears to be much more success with quarter-wave TL's such as these www.quater-wave.com. It early days at the moment and Im just looking forward to getting something off the ground.

Hi!

I wondered how your project phased out? You probably discovered that Fostex have a narrow sweet spot and not quite the clarity of Lowther?

Front horns do so much for these drivers . . .

Best wishes

Horninfected

 

[horninfected]

I haven't posted recently but people seem to know me as a Lowther fanatic - and to be frank, every time I'm impressed by other speakers I come back to Lowthers - with the proviso that they are appropriately specified with the right units - and think that there's nothing that beats them.

People who don't like Lowthers tend not to have heard the right units in the right cabinets. For direct radiation, then PM6 or DX/EX2 should be used. For situations requiring reflection off a wall behind, with the unit facing backwards to the wall, PM7 or DX/EX3 or 4 gives the extra treble, whilst DX/EX 4 are necessary to drive front horns. The pepperpot phase plugs are much too directional and the old bullets or the doorknob phaseplugs, with the whizzer cone rollback flipped forward so as to make a straight cone, give the cleanest and clearest possible sound.

For people unsure about the expense of Lowthers, there's an interesting trick that can be done with some speakers that can be picked up very economically. This is to buy a pair of either
Celestion Ditton 15
Celestion Ditton 200 or
Wharfedale Laser 120 units. These all have 8 inch woofers and a tweeter and are quite low efficiency. The Ditton 15 has woofer, tweeter and auxiliary bass radiator whilst the other two have two 8 inch units, one serving bass and the other midrange. I take out the ABR of the Ditton 15, and move the bass unit to the bottom slot, or with the other two, take out the middle unit serving midrange - and then insert in its place a modified full range unit wired in parallel with the remaining speaker from the amplifier fed by a 100uF capacitor - or 47uF capacitor if heavy bass is expected.

The modification I carry out enlarges the secondary whizzer cone of the full range unit to the same finishing diameter and conical angle as the Lowther and it gives an amazing presence to instruments - and letting the low efficiency woofer and tweeter augment the ends of the spectrum. The result is good. But there's better.

A friend who's been playing with speakers from before I was born has designed a speaker that really does give ultimate sound.

The top horns are based upon a variation of the Lowther TP1 design in the form of the Prophecy Audio horns by John Richardson http://www.tnt-audio.com/casse/prophecy_horns_e.html . He only made four pairs and by chance I happen to have bought his prototype many years ago from my friend Michael Wallis. These horns bring the sound alive. They are performance speakers and the instruments are aurally in front of you rather than any awareness of mere reproduction. The problem with these horns is what to use below around 150Hz . . .

For my pair I've used a pair of Lowther Acoustas facing backwards into the corner of the room to extend the horn, together with in parallel, a pair of Tannoy DC2000s using just the bass units - feeding the Prophecy top horns with DX4s through a 100uF capacitor and the bass units through a 3.5uH coil.
Rather than the mass of the Prophecy bass units or seeing the back of my Acoustas, Michael who for years has mastered bass horns to match Voigts and others, has now solved the problem: . . .

and particularly without bass resonances.

Best wishes

David P - very horninfected . . .