RT-2 Horn sub, the result

[tinitus]

Originally posted by Elbert
How did the Gamma actually compare with other drivers you tried, what made it better?

Specs

[Elbert]

Very interesting Anders,

Too bad with that freak radiator accident wrecking the horn!

Do you by any chance remember what other drivers you tried besides the gamma?

I was also thinking that there should be modern drivers available which could be superior to the "old" gamma design, but it seems that drivers with low Fs and very light cones are really difficult to come by today?


It's a real shame that the original article didn't cite more parameters for the drivers that were tested at the time, and a lot of those drivers are of course non-existing today, not to mention any technical data..

The only thing to go by is a woofer called Hokutone W300, which was said to be the best performing, it was cited to have a moving mass of 23 (!) g.

[AKN]

Elbert,

Do you by any chance remember what other drivers you tried besides the gamma?

Yes, In order of performance:

1. Gamma LA-1231 (could have been LA-1232, higher Q)
2. Philips AD12100HP8
3. HH B12L (high fs midbass)

[tinitus]

In my youth many of my friends played on GAMMA speakers, they were simply all over the place, around here...with better crossovers who knows what quality we would have had

Apart from that the 12" GAMMA interests me because it seems like it would work nicely in closed box, and that with good sensitivity...if specs holds...and its said to do well in lower midrange too, which is really rare

Not many woofers are fit fore closed box, another could much to my surprice be the DAYTON RS270S
Its also affordable, but havent had my attention as it has been available only in US...but now Intertechnik sells them, well carefully used I would expect it to have lots of potential, like fore a moderate but musical sub, which I havent seen tried yet

[Elbert]

Hmm.. wonder if it would be possible to get hold of a secondhand Gamma driver for a reasonable price?

Considering the uncertainties, I find the price of a new one a bit high to take the risk, also considering that this is an " ancient" design of east european origin..

As I was browsing around, I found some data on a sweedish forum:

http://www.hififorum.nu/forum/topic....97&whichpage=3

GAMMA 12":
Resonans : 25hz
Frekvensområde : 25 - 5khz
SPL : 94 db 1w1m
Magnetmassa : 2,6kg
Magnettyp : Alnico
Magnetflöde : 1,3 T
Talspoledia. : 38 mm
Talspolevikt : 7 gram
Konvikt : 12 gram
Rörlig massa : 19 gram (utan luft)
Resistans : 6,8 ohm
Trådlängd : 15 m
Talspolehöjd : 20 mm
Spalt höjd : 8 mm
mebrankant : Textil/gummi
Vikt : 3,6 kg
Xmax är 5,5 mm
Xlim_ 11,5

Now, if this is the data for the driver they are selling at Hifikit.se, I'm not sure..

http://www.hifikit.se/

I also find it a bit puzzling that I can't find the driver for sale anywhere else..?

[AKN]

Elbert,

No AlNiCo magnet anymore in Gamma LA-1231.

The maker of "Gamma": http://vissokogovoriteli.plc.bg/

This driver is perhaps close to LA-1231, several simular drivers do exist on the site.

[Elbert]

Hi Anders,

Yes, I've had a look at this site and that driver before..

Although somewhat similar in appearance to the Gamma LA 1231, I think it is not the same driver. For instance, If one looks at the VAS numbers quoted on the manufacturer site and at Hifikit.se, the valueas are 206 L vs 340 L respectively..

Alnico or ferrite.. all other things being equal, I can't see any reason why one magnet material is superior to the other as long as the flux in the magnet gap is similar. Having said that, some speaker designs exploit the smaller magnet size made possible by the higher flux density of Alnico by reducing driver weight (PA) or through enabling a more compact (and thereby a less acoustically obtrusive) motor system.

Of course, one shouldn't discard the "mythical" appeal of the more exotic alnico material...

[AKN]

Elbert,

I'm not supporting the mythical approach at all but I think in this case maybe the old motor was better. By simply looking at it one could easy see that the new motor has decreased X-mech and probably less flux (given the tiny magnet) than the old AlNiCo motor.

If one build this horn it must be of either historical or soundquality reasons. If one want a house wrecker there is better alternatives.

If you ditch your RT-2, why not convert it to the latest fame, tapped horn? The design almost lend itself to TH conversion.

[tinitus]

Originally posted by 4fun
Elbert,

If you ditch your RT-2, why not convert it to the latest fame, tapped horn? The design almost lend itself to TH conversion.

I did suggest that earlier, but wasnt noticed...I reckon Elbert may not know about Tapped horns
I did see the possibility like you do, that its practical doable and quite easily changed
It may not be perfectly ideal, but there doesnt seem to be much to loose in trying

[Elbert]

Seems like this is transforming in to yet another driver selection thread..

As I started searching for low Fs/ low Mms drivers, I came across A Visaton Driver called W300S..

http://www.visaton.com/en/chassis_zu...n/w300s_4.html

Again, I tried a Hornresp sim, and the frequency plot seems to suggest an improved low frequency response over the SEAS 13" (se enclosed image)

I also compared it against the response curve for the gamma, and it performed even better than that.

Anyway, what I do notice when I look at all the plots, are all the ripple sin the response, which to me suggests that the horn is acting more like some sort of quarter wave conical horn (voight) or a transmission line than a true horn.. But still, the efficiency numbers are quite high, at least compared to direct radiating drivers in closed or BR enclosures..