GM
> for a 500Hz XO point, a ~356Hz mass corner is more appropriate for a horn going down to 70-80Hz
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Oops! I did a typo, it should be ~353Hz, not that the difference is audible.
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>I thought:
- for a 500Hz XO point, >500 mass corner is nneded.........Why does it matter if Fmh is high or low?
====
It is if you're trying to throw high SPL hundreds of yards away in a narrow arc with little concern for sound quality (SQ), but for HIFI not a good plan since distortion will be excessive due to the high compression ratio (CR) required if only a single large, low Fs driver is used. Also, a low Fs driver with this high a mass corner won't have much excursion, so this will limit peak SPL down low.
Some folks argue that so little power is required in typical HIFI apps that the distortion is low enough to be a non-issue, but my ears say otherwise (at least they did way back when I had good hearing), so I don't recommend it except for the low/high BWs where our hearing acuity is ~non-existant.
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>- for a horn going down to 70Hz, as long as Fs < 70Hz (it's 50 hz), that's ok.
====
For a compression horn, ideally it should be somewhat higher than 70Hz. BF has mentioned ~20% as a rule-of-thumb (ROT) and back in the '60s an Altec engineer told me ~25%, but Leach's math says whatever driver's specs can yield a SQRT(70*500) = ~187Hz Fc in a sealed cab, with Fs, Qes, and Vas determining the CR and 'M' factor, so like any other cab type, not so 'cut n' dried' if designing for a particular alignment.
As Earl Geddes, Tom Danley, etc. 'preaches', for HIFI/HT apps the goal is low distortion and ~even power response over some vertical/horizontal coverage angle, so expo, tractrix, high gain or high aspect ratio CD isn't desirable for best performance. Unfortunately, most of us have to contend with size and/or WAF restrictions, so huge conical horns aren't an option and some compromises are required.
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>The idea of the 40 V x 120 H to integrate with the ribbon, was for the mids (500 Hz up). Though it souns like that idae should be dropped.
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Understood, and what I was referring to when I listed why it wasn't a viable design AFAIK.
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>I imagine that 90 * 40 is a reasonable option.
====
Yes, and no IMO. I use Altec 511s for 500-20kHz for a couple of reasons, though they do audibly 'color' (distort) the sound when used in our acute hearing BW. The coverage angles are what I need with the current set-up and I just happen to like how they sound once their infernal ringing is well damped, but have no delusions that they are ~accurate reproducers. Indeed, neither multi-cells, other brands, nor my own 90 x 40 designs I've auditioned are acceptable substitutes to me, though if I ever decide to re-do the system for more accurate reproduction I'd do it based on the room's dims, screen size and viewing distance, which currently equates to ~60 x 60 conical, loaded with either a good duplex or a Unity configuration.
====
> or if the one ribbon has enough power handling for the app, just use the 'WG'
What's the 'WG' - a particular waveguide?
====
No, just an abbreviation for 'waveguide'.
GM
> for a 500Hz XO point, a ~356Hz mass corner is more appropriate for a horn going down to 70-80Hz
====
Oops! I did a typo, it should be ~353Hz, not that the difference is audible.
====
>I thought:
- for a 500Hz XO point, >500 mass corner is nneded.........Why does it matter if Fmh is high or low?
====
It is if you're trying to throw high SPL hundreds of yards away in a narrow arc with little concern for sound quality (SQ), but for HIFI not a good plan since distortion will be excessive due to the high compression ratio (CR) required if only a single large, low Fs driver is used. Also, a low Fs driver with this high a mass corner won't have much excursion, so this will limit peak SPL down low.
Some folks argue that so little power is required in typical HIFI apps that the distortion is low enough to be a non-issue, but my ears say otherwise (at least they did way back when I had good hearing), so I don't recommend it except for the low/high BWs where our hearing acuity is ~non-existant.
====
>- for a horn going down to 70Hz, as long as Fs < 70Hz (it's 50 hz), that's ok.
====
For a compression horn, ideally it should be somewhat higher than 70Hz. BF has mentioned ~20% as a rule-of-thumb (ROT) and back in the '60s an Altec engineer told me ~25%, but Leach's math says whatever driver's specs can yield a SQRT(70*500) = ~187Hz Fc in a sealed cab, with Fs, Qes, and Vas determining the CR and 'M' factor, so like any other cab type, not so 'cut n' dried' if designing for a particular alignment.
As Earl Geddes, Tom Danley, etc. 'preaches', for HIFI/HT apps the goal is low distortion and ~even power response over some vertical/horizontal coverage angle, so expo, tractrix, high gain or high aspect ratio CD isn't desirable for best performance. Unfortunately, most of us have to contend with size and/or WAF restrictions, so huge conical horns aren't an option and some compromises are required.
====
>The idea of the 40 V x 120 H to integrate with the ribbon, was for the mids (500 Hz up). Though it souns like that idae should be dropped.
====
Understood, and what I was referring to when I listed why it wasn't a viable design AFAIK.
====
>I imagine that 90 * 40 is a reasonable option.
====
Yes, and no IMO. I use Altec 511s for 500-20kHz for a couple of reasons, though they do audibly 'color' (distort) the sound when used in our acute hearing BW. The coverage angles are what I need with the current set-up and I just happen to like how they sound once their infernal ringing is well damped, but have no delusions that they are ~accurate reproducers. Indeed, neither multi-cells, other brands, nor my own 90 x 40 designs I've auditioned are acceptable substitutes to me, though if I ever decide to re-do the system for more accurate reproduction I'd do it based on the room's dims, screen size and viewing distance, which currently equates to ~60 x 60 conical, loaded with either a good duplex or a Unity configuration.
====
> or if the one ribbon has enough power handling for the app, just use the 'WG'
What's the 'WG' - a particular waveguide?
====
No, just an abbreviation for 'waveguide'.
GM
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