According to the simulation I've done, there's plenty of headroom with regards to max excursion all the way down. Currently I don't even have the amp power available to take me near the damage excursion limit.
And no sir, the rear chamber is 100% tight, the carpentry work was at least one thing I got reasonably right with this project so far!
Now, If I can just get that SEAS woofer in there...
And no sir, the rear chamber is 100% tight, the carpentry work was at least one thing I got reasonably right with this project so far!
Now, If I can just get that SEAS woofer in there...
.. And in it went...
Well, that was a remarkable difference, suddenly the basement was back in the music!
Allthough there is probably still some room for improvement with proper equalisation and X-over adjustments (and perhaps an inductor), the Horn now seems to go just as deep as the old BR woofer, so that proves that I screwed up on woofer selection and that the horn has true potential given the right driver.
Too bat in a way, that Eminence driver was just soo sexy looking with that big fat magnet and everything!
Enclosed is a hornresp sim based on the horn profile provided by Bjorno was kind enough to share. The gray curve is the result with the 27 Hz Fs SEAS woofer.
http://www.seas.no/images/stories/vintage/pdfdataheet/h172_and_179_33f-wb_and_dd.pdf
The graph shows a somewhat improved low end response, but the audible result was certainly more dramatic than what the simulation plot suggests.
So, goodbye High Fs PA midwoofer and welcome lo Fs HiFi Sub!
but then there is a new problem, the main speaker will want it's woofer back, and I need to find something equaly, or even better, performing to go in the horn...
there are a number of super-low Fs monster woofers out there (a lot of them with very poor efficiency it must be said).
What worries me a bit is that most of these woofers have very heavy cones.
The original article warned against using woofers with heavy cones just like it advised the use of low Fs drivers..
Hmmm..
but now that I've got an improved hornresp model and have performed some practical experimentation correlating simulations with real life results, this tool might be a bit more usefull for selecting a new woofer.
I must however change my conclusion from "disappointing" to "really promising"
Well, that was a remarkable difference, suddenly the basement was back in the music!
Allthough there is probably still some room for improvement with proper equalisation and X-over adjustments (and perhaps an inductor), the Horn now seems to go just as deep as the old BR woofer, so that proves that I screwed up on woofer selection and that the horn has true potential given the right driver.
Too bat in a way, that Eminence driver was just soo sexy looking with that big fat magnet and everything!
Enclosed is a hornresp sim based on the horn profile provided by Bjorno was kind enough to share. The gray curve is the result with the 27 Hz Fs SEAS woofer.
http://www.seas.no/images/stories/vintage/pdfdataheet/h172_and_179_33f-wb_and_dd.pdf
The graph shows a somewhat improved low end response, but the audible result was certainly more dramatic than what the simulation plot suggests.
So, goodbye High Fs PA midwoofer and welcome lo Fs HiFi Sub!
but then there is a new problem, the main speaker will want it's woofer back, and I need to find something equaly, or even better, performing to go in the horn...
there are a number of super-low Fs monster woofers out there (a lot of them with very poor efficiency it must be said).
What worries me a bit is that most of these woofers have very heavy cones.
The original article warned against using woofers with heavy cones just like it advised the use of low Fs drivers..
Hmmm..
but now that I've got an improved hornresp model and have performed some practical experimentation correlating simulations with real life results, this tool might be a bit more usefull for selecting a new woofer.
I must however change my conclusion from "disappointing" to "really promising"
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Nice to hear we were on the right track, and you have done good work to prove it, makes it meaningfull to be here
One reason your Seas works subjectively better but really dont measure that much different could, besides the lower Fs, be due to different and higher Qts
A 10" SB Acoustic may be a good choice, but its not the cheapest, 212 EUR from IntertechniK
They also sell the US Dayton, and the 10" RS270S cost only 99 EUR and is said to be real good value
The Dayton has 12mm Xmax which is ok, unless you play exstremely loud
The SB Acoustic is a real performer in terms of Fs and Xmax
I have never heard any of them, just fore inspiration
One reason your Seas works subjectively better but really dont measure that much different could, besides the lower Fs, be due to different and higher Qts
A 10" SB Acoustic may be a good choice, but its not the cheapest, 212 EUR from IntertechniK
They also sell the US Dayton, and the 10" RS270S cost only 99 EUR and is said to be real good value
The Dayton has 12mm Xmax which is ok, unless you play exstremely loud
The SB Acoustic is a real performer in terms of Fs and Xmax
I have never heard any of them, just fore inspiration
This thread has certainly been useful so far!
One thing is theorizing and discussing, but the real fun part is to do some practical experiments!
Some of those drivers look interesting, but I'm more on the lookout for a 12" driver as this is what the horn is dimensioned for.
Just did some more hornresp sims, and I the general trend seems to be that low Fs woofers with heavy cones generate very uneven responses.
Having said that, the low end extension seem to be better, so it might be that there is an inevitable inherent compromise there.
One thing is theorizing and discussing, but the real fun part is to do some practical experiments!
Some of those drivers look interesting, but I'm more on the lookout for a 12" driver as this is what the horn is dimensioned for.
Just did some more hornresp sims, and I the general trend seems to be that low Fs woofers with heavy cones generate very uneven responses.
Having said that, the low end extension seem to be better, so it might be that there is an inevitable inherent compromise there.
Hi,
I've built that basshorn back in the eighties and I was very satisfied with it, good performance for it's size being a horn.
Back then I had best result with a Gamma LA-1231 (some rebranded Bulgarian unit), very lightweight cone and large VAS. Gamma driver still available at Hi Fi Kit same cone but ferrite magnet opposed the prior AlNiCo magnet used on earlier units. What the motor change have done to the specs I don’t know but I suspect performance has decreased somewhat.
I remember that I the gamma unit had limited power capability, remembering that I fried the coil playing loud at a party.
I did also try a low VAS high Fs driver and the result were almost a disaster as I recall.
I've built that basshorn back in the eighties and I was very satisfied with it, good performance for it's size being a horn.
Back then I had best result with a Gamma LA-1231 (some rebranded Bulgarian unit), very lightweight cone and large VAS. Gamma driver still available at Hi Fi Kit same cone but ferrite magnet opposed the prior AlNiCo magnet used on earlier units. What the motor change have done to the specs I don’t know but I suspect performance has decreased somewhat.
I remember that I the gamma unit had limited power capability, remembering that I fried the coil playing loud at a party.
I did also try a low VAS high Fs driver and the result were almost a disaster as I recall.
Hei Anders!
Well, as a matter of fact, I just did a hornresp sim with the gamma driver you mentioned, and the response curve is by far the best looking so far, so it is very interesting to hear that you had such good results with this driver!
And your disasterous result seems to correlate very well with my own recent experience using the Eminence Delta pro 12".
If the driver had been slightly less expensive (300 NOK in shipping to Norway bumps up the price), I would have concidered buying one just to try it out.
But at the moment I'm having doubts wheteher I should continue to sink more money in to this project as I suspect that even with an optimal driver, I will not get the deep bass I really wish for.
And with a box that size, I really feel that there should be an advantage compared to what one can achieve today with a BR enclosure of the same size..
on the Hifi-kit web page, the Gamma is rated at 150 watts, so perhaps there has been some improvements over the years?
Well, as a matter of fact, I just did a hornresp sim with the gamma driver you mentioned, and the response curve is by far the best looking so far, so it is very interesting to hear that you had such good results with this driver!
And your disasterous result seems to correlate very well with my own recent experience using the Eminence Delta pro 12".
If the driver had been slightly less expensive (300 NOK in shipping to Norway bumps up the price), I would have concidered buying one just to try it out.
But at the moment I'm having doubts wheteher I should continue to sink more money in to this project as I suspect that even with an optimal driver, I will not get the deep bass I really wish for.
And with a box that size, I really feel that there should be an advantage compared to what one can achieve today with a BR enclosure of the same size..
on the Hifi-kit web page, the Gamma is rated at 150 watts, so perhaps there has been some improvements over the years?
300 Watts? Small wonder the thing melted, hehe!
Expect and expect... Well.. I was assuming that it could go down to 40 something with reasonable output, but you might say I was perhaps expecting more a certain listening experience than numbers. Like jbell pointed out numbers are one thing...
I guess I was hoping for something that could really set the room in motion without getting pushed in to distortion you might say..
How did the Gamma actually compare with other drivers you tried, what made it better?
Expect and expect... Well.. I was assuming that it could go down to 40 something with reasonable output, but you might say I was perhaps expecting more a certain listening experience than numbers. Like jbell pointed out numbers are one thing...
I guess I was hoping for something that could really set the room in motion without getting pushed in to distortion you might say..
How did the Gamma actually compare with other drivers you tried, what made it better?
Elbert said:300 Watts? Small wonder the thing melted, hehe!
Expect and expect... Well.. I was assuming that it could go down to 40 something with reasonable output, but you might say I was perhaps expecting more a certain listening experience than numbers. Like jbell pointed out numbers are one thing...
I guess I was hoping for something that could really set the room in motion without getting pushed in to distortion you might say..
How did the Gamma actually compare with other drivers you tried, what made it better?
The Gamma had great sensitivity and did go lower in RT-2 compared to other available units. That said, I think that many modern drivers would also perform nicely.
I had certainly no problem reaching down to 40 Hz with good sensitivity and low distortion. I used third order active filter crossing at 100Hz over to main speakers.
I was 15 years young back in 1982 when I did build the RT-2 together with my grandfather, an experience I'll never forget. The RT-2 was then in duty for about 10 years until a heat radiator sprung leak and destroyed the horn.
Back then I did not have any measurement capabilities as of today. It would be higly interresting to see some in room measurements for this bass horn.
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.
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.
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
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
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.asp?ARCHIVE=true&TOPIC_ID=40097&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..?
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.asp?ARCHIVE=true&TOPIC_ID=40097&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..?
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.
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.
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...
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...
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.
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.
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_zubehoer/tiefton/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..
As I started searching for low Fs/ low Mms drivers, I came across A Visaton Driver called W300S..
http://www.visaton.com/en/chassis_zubehoer/tiefton/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..
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