Member
Joined 2009
I don't think this design functions like a ripole. The idea is that the slot amplifies the front wave only. I expect something similar to cardioid behavior.
The AMT-3 has a slot ratio of about 3 to 1 in the front. This is rather conservative. Some ripoles have up to 5 to 1 in order to get lowest bass. A ratio of 1.5 or 1 to 1 in the back is common for ripoles too. In simulations (or built ripoles) you hardly see any more change when going below 1.5 to 1. The air space between cone and back slot simply is too large to allow for that. The 9 dB front-to-back difference stated in the article doesn't really qualify as a cardioid pattern IMHO.
Rudolf
Member
Joined 2009
Hypercardioid?
The slot ratio is one thing and then there is the polarity of the drivers. I might be wrong but I was under the impression that a ripole configuration implies both drivers move together in phase. Here they are reversed. I'm not quite sure what effect that will have on the radiation pattern.
A polar graph will be very informative. This is a very interesting design, I'm also curious to see if the sides can be curved without losing much of the 1:3 output ratio.
Member
Joined 2009
ripole/slot loaded? wait a sec...I think its its NEITHER.
Maybe im ignorant, but i believed that a ripole (IF thats what this is) actually loses efficiency since you are slot loading both the front and rear of the driver equally with air mass to lower the effective Fs by increasing the 'seen' moving mass of the cone. hence t/s do not all stay the same either.
With unequal 'slot loading' or 'air mass loading' arent we just approaching a condition more akin to a 'narrowed aperture' H-frame with assymetric driver placement? I kinda get the heil AMT arguement, with multiple woofers facing eachother in phase, somewhat like a 'flareless' horn. however the 'pinch' principle is good for efficiency, but is it good for sound quality, especially at LF where the larger vols of fluidic air are required to be squeezed through a <Sd gap.....much like in vented(well most) designs. Air noise might likewise be a problem, I wouldve imagined. After all an AMT tweeter moves far less air and is far less restricted in doing so........
I too have seen some designs like this before, although not the one Rudolf posted. There seems to be a lot of Euro interest in 'ripole' type designs. I myself was considering doing this with a larger woofer, to compare against a U and H frame using the same driver. following on an OB midHF from about 300hz, in this way the 'air-mass-loaded OB sub' could function as both a stability aid at the bottom of the MidHF baffle, with each slot radiating in the desired direction. Appearing much like a simple slot port at the bottom of the baffle.
Intriguing i must say. The only 'no-go' for me was the lack of a suitably capacious listening area in my home.......once i get rich or move to the states then ill persue it
Maybe im ignorant, but i believed that a ripole (IF thats what this is) actually loses efficiency since you are slot loading both the front and rear of the driver equally with air mass to lower the effective Fs by increasing the 'seen' moving mass of the cone. hence t/s do not all stay the same either.
With unequal 'slot loading' or 'air mass loading' arent we just approaching a condition more akin to a 'narrowed aperture' H-frame with assymetric driver placement? I kinda get the heil AMT arguement, with multiple woofers facing eachother in phase, somewhat like a 'flareless' horn. however the 'pinch' principle is good for efficiency, but is it good for sound quality, especially at LF where the larger vols of fluidic air are required to be squeezed through a <Sd gap.....much like in vented(well most) designs. Air noise might likewise be a problem, I wouldve imagined. After all an AMT tweeter moves far less air and is far less restricted in doing so........
I too have seen some designs like this before, although not the one Rudolf posted. There seems to be a lot of Euro interest in 'ripole' type designs. I myself was considering doing this with a larger woofer, to compare against a U and H frame using the same driver. following on an OB midHF from about 300hz, in this way the 'air-mass-loaded OB sub' could function as both a stability aid at the bottom of the MidHF baffle, with each slot radiating in the desired direction. Appearing much like a simple slot port at the bottom of the baffle.
Intriguing i must say. The only 'no-go' for me was the lack of a suitably capacious listening area in my home.......once i get rich or move to the states then ill persue it
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No, I used the 8" Vifa woofers I got from Quadrature about 20 years ago.
Cool about the Visatons, but I don't imagine they were done before 1973...
I would prefer to have the B5 without the eq... schematics......?
Smarty pants, why don't you just take those parts out?
I actually did that 11 years + a month ago... close but no cigar, with no clue that with a bit more it could have had the advantage of Dr Heil's creation
Now i should still have a dozen of the 12" Foster left over after i do the pair of push-push push-pull isobarik woofers. That will give me a lot more shelf space (and still more helper woofers)
dave
Probably right. The issue of slot ratio is mostly one of turbulence and
resonance issues. 3:1 is the highest I have been comfortable with.
How would this work if one were to enclose the speakers instead, would it mean a much small box be needed but still gives a lot of oomph? I know it is not open baffle anymore but having oversized speakers are luxuries to most people.
On a different note, what if one were to enclose it with something not really sound tight, for example foam material, just to reduce the rear waves coming out...
Oon
On a different note, what if one were to enclose it with something not really sound tight, for example foam material, just to reduce the rear waves coming out...
Oon
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