"room loading" is very real. It's as real as standing waves 😀 Placing a horn on the floor, in a corner, against a wall all will effect it's performance. I have leaned that the best I can do in my room is build the horn to work with acoustic - Bass horns can and are used down to their flare frequency. You maybe confusing free space midrange horns like tractrix or conical profile that often don't load or "eq" the lower end of the response to the flare frequency. This happens most with compression drives that aren't intended to be used very low. For example I have a 150Hz conical horn that loads to 150 Hz hen set on the floor loaded with 10" JBL 2123. The same horn when loaded (much longer) a Selenium D405 4' compression driver only works to 500 cycles.
Reactance annulling is for cone drivers or for the sadists that redesign the back chambers of their compression drives.
Oh yes, Hornresp has the option of telling it to simulate where the horn will be used in the room
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Hi JoshK,
'unaHm' is referring to using the Hornresp 'System Design With Driver' and 'System Design From Specifications' tools to automatically generate a design, in which case a hyperbolic-exponential (Hyp) flare profile is always specified.
Kind regards,
David
Hi unaHm,
Not really. I was just showing the difference between the power response and the pressure response.
Kind regards,
David
Thanks Pooh,
I am using AJ-Horn, it's hard to break this habbit. There is no extension (like going from 50Hz to 30Hz) in AJ-horn when i switch from halfspace to corner loading for any given bass-mid horn.
So for a cone fronthorn reactance annuling is extremly important and for a normal 1 inch CD used above 2 kHz this is nothing to be worried about?
I am using AJ-Horn, it's hard to break this habbit. There is no extension (like going from 50Hz to 30Hz) in AJ-horn when i switch from halfspace to corner loading for any given bass-mid horn.
So for a cone fronthorn reactance annuling is extremly important and for a normal 1 inch CD used above 2 kHz this is nothing to be worried about?
Hello, I'm not familiar with the AJ program.
Mr. McBean's Hornresp program surely shows the Position differences when modeling the horns. I think once you use the new program you will find it is very accurate in the pistonic regions (low and mid) in it's modelling of what you actually build. I should mention real loading Is nearly impossible unless the horn is built into the corner, wall or floor (and the wall is perfectly rigid as in brick or concrete) so I recommend if you plan on placing the horn in a corner 1/8 th space build for 1/4 space because it is difficult to get the horn in the actual corner - same goes for the other positions. if you plan on placing the horn 1/4 space simulate the design for half space ECT
I would not worry at all about reactance annulling with compression drivers and if you use Hornresp use the freespace 4pi setting
Mr. McBean's Hornresp program surely shows the Position differences when modeling the horns. I think once you use the new program you will find it is very accurate in the pistonic regions (low and mid) in it's modelling of what you actually build. I should mention real loading Is nearly impossible unless the horn is built into the corner, wall or floor (and the wall is perfectly rigid as in brick or concrete) so I recommend if you plan on placing the horn in a corner 1/8 th space build for 1/4 space because it is difficult to get the horn in the actual corner - same goes for the other positions. if you plan on placing the horn 1/4 space simulate the design for half space ECT
I would not worry at all about reactance annulling with compression drivers and if you use Hornresp use the freespace 4pi setting
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I am not worried at all about reactance annuling for 1 inch drivers 2 kHz and up, the word would be curious 🙂 Seems so easy to do with some putty in the backchamber. Just wondering if anybody tried this.
Altec/GPA has used loading caps since at least the late 1940s to reactance annul their 1" compression drivers to increase power handling. In these cases, the gap between the cap and diaphragm allows very little excursion over any portion of the diaphragm dome, surround.
Factor in that at least with these drivers mounted on Altec horns, removing the rear cover causes almost no change in the driver/horn's response, indicating that this small net Vb is essentially an I.B. acoustically, so doubt that adding putty would make any audible change.
GM
Factor in that at least with these drivers mounted on Altec horns, removing the rear cover causes almost no change in the driver/horn's response, indicating that this small net Vb is essentially an I.B. acoustically, so doubt that adding putty would make any audible change.
GM
Thanks David. I suppose I'm just trying to find something suitable. 'On paper', a lot of the designs look fine, but I'd like someone's experienced opinion to say 'yes that's fine, go ahead' 🙂
I've also noticed with HornResp that using the "System Design with Driver" tool that S1 seems quite small. I've just plugged in a design with the Alpha 8 and specified a lower roll-off of 125Hz and upper of 1kHz, and the SPL graph looks quite nice!
However, the compression ratio that the size of S1 creates is 13.5:1! Would that create a potentially damaging situation for that driver?
However, the compression ratio that the size of S1 creates is 13.5:1! Would that create a potentially damaging situation for that driver?
That seems a bit extreme.
I'm using more than double that area with my Alpha 8s, and have had no problems.
They seldom see more than 180 watts peak, and are crossed at 100 Hz.
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Art,
That's a very nice set of unity/synergy horns! 🙂
Ok, I'm glad that my uncertainty can be backed up.
So, going from that, a S1 of 31.1cm^2 is acceptable? It seems that more compression smooths out the frequency response...but obviously we can't get something for free!
That's a very nice set of unity/synergy horns! 🙂
Ok, I'm glad that my uncertainty can be backed up.
So, going from that, a S1 of 31.1cm^2 is acceptable? It seems that more compression smooths out the frequency response...but obviously we can't get something for free!
The amount of compression is related to distortion. Maybe you can fiddle a bit with the compression ratio and look at the Thd numbers Hornresp plots for the different ratio's.
They are actually Paraline horns, Synergy and Unity horn throats are the size of the compression driver exit.
31.1 cm^2 should be on the edge of what is O.K., I don't think the Alpha 8 cones will kink with that exit size.
Interesting. It's the first time outside of Patrick Bateman's threads that I've seen an implementation of the Paraline. Very cool!
Ok. I'd assume also that you're using the drivers for PA applications, so you're going to be putting a lot more power into them (than I will be in my home application) and more likely to see damage.
So err, thanks for being the guinea pig! 🙂
Still, I noticed that your answer is a cautious one. If it were you, what would you set the exit size to?
I'd do some experimentation to determine the size throat that gives the best actual measured response.
For a FLH, using a phase plug can increase (and clean up) the upper response too, but is another fiddly bit to construct.
The picture below shows a phase plug design I used for some dual 15" cabinets back in 1997, the plug is similar to what EV did in their MT2 and MT4 10" horn throats.
Art
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After a bit of experimenting with HornResp (which I know isn't the same as real-world, in-room measurements), I found this design to be interesting:
Again it's a Tractrix curve, but this time I aimed at a low frequency roll-off of 125Hz. So far, this seems to be the smoothest and most consistent response graph I've seen.
I need to look into the topic of phase plugs more...I think I've seen them being used on these forums as much as they haven't, so it's another avenue I've not been sure on pursuing or not 🙂
Also, I've re-read some of the information on Bill Fitzmaurice's site in terms of corner-loading the T18 subs. He's stated that one of the best placements for them is to fire into a corner, about 12 inches from the mouth of the horn to the corner of the wall. While this improves the T18's performance, it also allows me a little more room to make a mid horn a little longer, if necessary, if I wanted it to stack nicely on top of the sub.
That leads me to around 30 inches so far, which might allow me to accommodate the Tractrix horn and a small driver chamber...if I folded or bent it at the throat end...
Again it's a Tractrix curve, but this time I aimed at a low frequency roll-off of 125Hz. So far, this seems to be the smoothest and most consistent response graph I've seen.
I need to look into the topic of phase plugs more...I think I've seen them being used on these forums as much as they haven't, so it's another avenue I've not been sure on pursuing or not 🙂
Also, I've re-read some of the information on Bill Fitzmaurice's site in terms of corner-loading the T18 subs. He's stated that one of the best placements for them is to fire into a corner, about 12 inches from the mouth of the horn to the corner of the wall. While this improves the T18's performance, it also allows me a little more room to make a mid horn a little longer, if necessary, if I wanted it to stack nicely on top of the sub.
That leads me to around 30 inches so far, which might allow me to accommodate the Tractrix horn and a small driver chamber...if I folded or bent it at the throat end...
That curve looks extremly nice.
I would be worried about two things. 1. Tractrix might not be the best choice for getting the most out of bass down to Fc. 2. The compression ratio is still very high. I am very aware i am a NOOB, but from what i have red sofar (Bruce Edgar / Volvotreter) 1/4 to 1/2 compression ratio's are easier on the ear... Please notice Art is using this very high compression ratio in a conical horn with has the lowest added THD due to narrowing of the troath.
I would be worried about two things. 1. Tractrix might not be the best choice for getting the most out of bass down to Fc. 2. The compression ratio is still very high. I am very aware i am a NOOB, but from what i have red sofar (Bruce Edgar / Volvotreter) 1/4 to 1/2 compression ratio's are easier on the ear... Please notice Art is using this very high compression ratio in a conical horn with has the lowest added THD due to narrowing of the troath.
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i doubt, that you can build this
An externally hosted image should be here but it was not working when we last tested it.
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