MaVo said:
Thanx, didn't know that.
Seems counter-intuitive; I thought the upper knee would be related to the shortest fold, and using DTS-20 folding (driver in middle, path going down front center, dividing, going up sides, down back) would get around it by having a short fold.
I still wonder how Danley does it...
even with resonators & coils.
So I'm back to plan A:
building two pair of THs, one for first octave, one for second octave.
At least I can get it back to 8 feet of so.
Any suggestions...
Why dont they? Is there some special anti standing wave device i have not heard of yet?
For completeness, a quote from Thomas Danleys labhorn posts:
"Also, at the frequency where the difference in path length between the inside of the bend and the outside of the bend is N 1/2 wavelengths, there are deep notches in the response.
This is a result of the opposite phases recombining (and
canceling out) after the bend. A good rule of thumb is make sharp bends with a short radius -or- bend angle is inversely proportional to radius). The point is again remember the "acoustic size" of what ever your dealing with.
As you can see on the LAB sub the only large degree bend has a small radius (the one at the nose).
Still more complication, at the point where the wall area is a significant acoustic size, the sound pressure couples to the width mode resonance (caused by the parallel walls) which puts the first in a series of notches in the response coming out of the mouth.
In this situation, there is a 1/2 wavelength standing wave with the pressure maxima at the walls and velocity max in the center.
Coupling to this mode saps off energy at frequencies related to the N 1/2 wavelengths.
Here, your horn mouth width (where it has parallel walls) also kind of sets your upper frequency limit
For a 21 inch wide horn like the LAB sub, the first width mode notch should be in the mid 300's which is a non issue."
For completeness, a quote from Thomas Danleys labhorn posts:
"Also, at the frequency where the difference in path length between the inside of the bend and the outside of the bend is N 1/2 wavelengths, there are deep notches in the response.
This is a result of the opposite phases recombining (and
canceling out) after the bend. A good rule of thumb is make sharp bends with a short radius -or- bend angle is inversely proportional to radius). The point is again remember the "acoustic size" of what ever your dealing with.
As you can see on the LAB sub the only large degree bend has a small radius (the one at the nose).
Still more complication, at the point where the wall area is a significant acoustic size, the sound pressure couples to the width mode resonance (caused by the parallel walls) which puts the first in a series of notches in the response coming out of the mouth.
In this situation, there is a 1/2 wavelength standing wave with the pressure maxima at the walls and velocity max in the center.
Coupling to this mode saps off energy at frequencies related to the N 1/2 wavelengths.
Here, your horn mouth width (where it has parallel walls) also kind of sets your upper frequency limit
For a 21 inch wide horn like the LAB sub, the first width mode notch should be in the mid 300's which is a non issue."
MaVo - I planning on building a pair of your 38 Hz Tang Band tapped horns. Are there any improvements I could try out? Will rounding the outer radius of the bend do anything noticable for sq? Does the overall width of the horn matter - can I increase it slightly for ease of building?
What does the 4.7 mH inductor do? Will I need it if I am running the horns off a seperate amp connected to my LF out on my receiver?
I will be running the tapped horns with two 5" "Microbe" bookshelf speakers I built.
What does the 4.7 mH inductor do? Will I need it if I am running the horns off a seperate amp connected to my LF out on my receiver?
I will be running the tapped horns with two 5" "Microbe" bookshelf speakers I built.
Max mouth size?
As I understand it, compression ratio of a TH is defined by the ratio of throat area to cone area. In other words, Cone area (Sd) / S2 (throat area) has to be less than four or the driver will fail.
Earlier in this thread I read the mouth should be 2*Sd as a starting point. However, 4*SD seem to model really well (large BW) in a long TH, but I suspect there is a reason I haven't seen a large (3500cm^2) mouths.
Any input?
As I understand it, compression ratio of a TH is defined by the ratio of throat area to cone area. In other words, Cone area (Sd) / S2 (throat area) has to be less than four or the driver will fail.
Earlier in this thread I read the mouth should be 2*Sd as a starting point. However, 4*SD seem to model really well (large BW) in a long TH, but I suspect there is a reason I haven't seen a large (3500cm^2) mouths.
Any input?
cowanaudio said:
G'day to you too William from a fellow Aussie - ex QLD'er now living in the USA.
At a guesstimate, the HT horn I'm playing around with will be about 45x30x18" which would still be small compared with a FLH that could play down to 18hz, no?
Playing with the TH wizard, it seem that increasing the mouth size boots the sensitivity and really smooths out the response above 70hz. I'm getting about +/- 3db from 20-180hz. Only trade off seems to be a slightly lower cuttoff by a few HZ. L23 is rather huge at 489cm.
I'm sure I'm doing something dumb/wrong... will post up the graphs and numbers later today.
OK I think I see the error in my ways.
When I come to work out the dimensions of the horn, having a large mouth (S4) also means having a large S3 area... obvious now that I think about it. So the larger the mouth, the larger the cross section of the horn.
So as William suggests I would end up with a huge horn if I had a 3500 sq cm mouth.
When I come to work out the dimensions of the horn, having a large mouth (S4) also means having a large S3 area... obvious now that I think about it. So the larger the mouth, the larger the cross section of the horn.
So as William suggests I would end up with a huge horn if I had a 3500 sq cm mouth.
GM said:
Yeah that's why I was surprised by Chris8sirhC's comments of building a 30hz horn if I plan to cross it over at 80hz.
I keep going around in circles here and I'm sure I'll just end up designing something that's already been posted earlier on, but at least I'm learning a lot in the process. I don't feel comfortable building something that I don't comprehend.
GM, I'll try to find your HR models for reference. Any idea what page they're on?
hey guys i'm still learning HornResp.
Could one of you guys see if an Elemental Designs 9Kv.2 sub models well in a TH. This is going to be for car audio use so low end only needs to be down to 30-35Hz. Sub will be low pass around 80-100Hz depending on what Hornresp says.
Thanks.
http://www.edesignaudio.com/product_info.php?t=2&products_id=29
Qts: .30
Qes: .38
Qms: 3.5
Fs: 23 Hz
Re: 7.4
Vas: 45 L
Mms: 71.4 g
Bl: 15.34 T*m
SPL: 83.43 dB
Sd: 231 cm^2
Xmax: 14.1 mm
Voice Coil: 38 mm
Could one of you guys see if an Elemental Designs 9Kv.2 sub models well in a TH. This is going to be for car audio use so low end only needs to be down to 30-35Hz. Sub will be low pass around 80-100Hz depending on what Hornresp says.
Thanks.
http://www.edesignaudio.com/product_info.php?t=2&products_id=29
Qts: .30
Qes: .38
Qms: 3.5
Fs: 23 Hz
Re: 7.4
Vas: 45 L
Mms: 71.4 g
Bl: 15.34 T*m
SPL: 83.43 dB
Sd: 231 cm^2
Xmax: 14.1 mm
Voice Coil: 38 mm