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Fostex FE208-SOL box?
Fostex FE208-SOL box?
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Old 16th August 2019, 04:23 AM   #21
GM is offline GM  United States
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Quote:
Originally Posted by vcelkamaja View Post
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Well, front firing won't load as smoothly as one designed to be fired in the corner till the WLs get large enough not to notice the side gaps, but our hearing acuity is so poor down low that you notice anymore than you [don't] notice how badly most rooms modify the bass line.

The horn is designed under the assumption that it will be driven by a high output impedance such as you propose, but if you don't there will be a wide band 'sag' in the driver's critical mids BW like when driven with a SS or high DF PP tube amp and tone controls won't fix it unless it has a separate mids tone control or at least a 1/3 octave graphic EQ.

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Old 16th August 2019, 04:38 AM   #22
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Originally Posted by DrBoar View Post
The depicted horns are quite long but have small mouth area so the mouth area is the limiting factor for bass.
FWIW I prefer to view them as ducted port [mass loaded] TQWT alignments [ML-TQWT]. Would have to sim them, but maybe better bass 'horns' overall. It's what I use, though with a much shorter taper to suit my app, hence not as much wide band gain.

The Fostex won't have such limitations, so will need all the wide band horn gain it can get.

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Old 16th August 2019, 04:38 AM   #23
vcelkamaja is offline vcelkamaja  Czech Republic
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Originally Posted by DrBoar View Post
Most basshorns both work as pipe resonators and horns. To work as a horn it has to both be long enough and have bieg enough mouth area. The depicted horns are quite long but have small mouth area so the mouth area is the limiting factor for bass. To complicate things further: a horn placed close to a corner works as horn with twise the mouth area placed at a wall. So in this case placing the horn close to a corner will make the horn go a bit deeper in the bass.
Thanks a lot for explanation - the mouth area for the bigger one is 910 cm2 (original Fostex design 1027 cm2). What happens if I just make it bigger while keeping other dimensions as they are (Bigger opening in the front panel - rectangular hole)
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Old 18th August 2019, 08:13 PM   #24
vcelkamaja is offline vcelkamaja  Czech Republic
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Any feedback please? What happens if I make the mouth area bigger while keeping all other dimensions unchanged?
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Old 19th August 2019, 12:04 AM   #25
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Do mean making the small cab's vent duct bigger? If so, it will be tuned higher, maybe enough to make it sound 'boomy'/'flabby' [under damped response].

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Old 19th August 2019, 09:06 PM   #26
DrBoar is offline DrBoar  Sweden
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To be a ML-TQWT they need a severe constriction at the open end, usually a pipe/vent that gives the mass loading.
A straight pipe will have a resonance close to a frequency corresponding to a wavelength 4 times the lenght of the pipe (hence quarter wave resonator). Tapering the a pipe will lower the Q of the resonance that is widen the frequency range of the resonance. Negative taper lower the resonance a positive taper (bigger at the open end) increase the frequency. This increase can be counteracted by constricting the open end down to perhaps 50% if the surface area of the cone of the driver.

So a Pipe with a positive flare will act as a horn where the diameter of the horn mouth is a sizable fraction of the wavelength. How big depends on how the mouth is placed relative surfaces (hanging in space, on the floor freestanding, on the floor against a wall or in a corner). Below this frequency the flared pipe can still act as quarter wave resonator if it is long enough. So any bass horn of a practical size work as a hybrid with both horn features and pipe features.

Bigger mouth = more horn features in the bass. Something like the "Schmacks horn" will work like a horn a bit deeper than the Fostex designs, but then the volume is roughly twise as much.
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