As NB noted, T/S cab theory peters out at a driver's effective upper mass corner = ~342 Hz for the small format VOT horns with horn directivity extending it out to the driver's stepped up response, filling it out to ~1600 Hz.
At the end of its 'reign', with a 500 Hz horn it was XO'd @ 1200 Hz for power handling purposes.
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The 'shaded' 'pockets' also act as an acoustic low pass filter, though all those shown in the 1st post appear to be Altec's proven 8" x 16" = 128"^2 throat design, which with virtually all Altec 15" 128"^2 Sd and its numerous copies' over the decades makes it a 1:1 CR and FWIW/YMMV, I can't recall seeing any of the pioneer's horns having < 1:1, though seen some with > 1:1.
Numbers? It's an A2 VOT consisting of (2) dual 15" 210 horn cabs + 'wings', 1505 15 cell/500 Hz HF horn (page 6).
There also were 300, 400 Hz horns used with one or more public Address (PA) driver(s), though normally used at 500 Hz in theater apps for greater polar response control.
Indeed. Within the driver nearfield, and that means at lower frequencies in this case, the front of the "baffle" will fill out that way, moving in the direction of a cylindrical source.
They do and always will, but the purpose of a phase plug is to reduce this by extending the bandwidth to some degree. A throat chamber could be said to be a practical limitation more than a feature, but it seems that way because it is so often exploited in lower frequency horns.
^What GM said^
Smartest Altec man I know.
I have it on good authority he knows someone with the 300 hz horns, the 210 cabinets and the N-500 XOs. 😉
IIRC, 500 was the lowest Altec ever XOd their systems.
Smartest Altec man I know.
I have it on good authority he knows someone with the 300 hz horns, the 210 cabinets and the N-500 XOs. 😉
IIRC, 500 was the lowest Altec ever XOd their systems.
yup.
2 drivers, higher mass corner than the b&c 12".......
Shared loading, even cleaner, less likely to blow them up, or a bit more room for eq...................
Some Jbl paper mentioned as you double the drivers, excursion is halved, and harmonic distortion goes down to 1/4 what you had with 1 driver.
And best question, why not ?
Especially when you have paid (in size) for a long bass horn with a big mouth........
Again, my opinion, may not be suitable for all audiences........
2 drivers, higher mass corner than the b&c 12".......
Shared loading, even cleaner, less likely to blow them up, or a bit more room for eq...................
Some Jbl paper mentioned as you double the drivers, excursion is halved, and harmonic distortion goes down to 1/4 what you had with 1 driver.
And best question, why not ?
Especially when you have paid (in size) for a long bass horn with a big mouth........
Again, my opinion, may not be suitable for all audiences........
How should I read those sims? Is that the predicted working/loading of the horn, or the actual output of the speaker as a whole?
Without the horn, a driver would not drop so soon, so steeply, so what's going on?
Without the horn, a driver would not drop so soon, so steeply, so what's going on?
A double 80 Hz 12MH32 horn can do well past 600 with the right expansion rate geometry and W x H ratio. My own research revealed this while working on a midbass horn design to go with my A290s.
Main problem with most midbass horns I've tried is they're too short for their mouth size and have alot of internal reflections that cause ripple. You'd need at least 30 " WG length to go down past 100 hz without noticeable coloration.
Main problem with most midbass horns I've tried is they're too short for their mouth size and have alot of internal reflections that cause ripple. You'd need at least 30 " WG length to go down past 100 hz without noticeable coloration.
Has anyone ever tried a dual cone driver FLH, where the upper driver is run up to cutoff and the lower one is being lowpassed ie like in a 2.5 way speaker? This may be a pointless thing to do in a pro audio application, but in a hifi situation, it could be useful to not have the driver closest to the floor playing up higher to avoid major floor reflections.
Or maybe keeping it would reduce the floor issues by providing the right reflection? (If I haven't made my point clear I could do some sims to demonstrate)
Yeah, time to popup a simulator 🙂 lower driver would be close to floor, path length difference between direct sound and floor reflection would be shorter than with the upper driver, pushing all interference higher up in frequency out of harms way, so it works opposite as profiguy reasoning. Or, the two making interference and narrowing response lower in frequency than either alone. But, if it feels there is some audible difference then no reason to believe there is not, but instead time to investigate what makes it.
Like this one
I'm totally guessing it, I've never heard such speaker so can't say anything about any audibility, or anything really 🙂 all I know much things change between two devices, unless very tightly controlled, so its always hard to say what actually makes the audible differences. It would be very interesting to hear such thing and tune out, to really find out what makes bad sound.
Like this one
feels counter intuitive with assumption that deep devices sound more "horn" like than shallower ones, like no horn at all, which has become a myth for "horn sound". You seem to describe it the other way around than my assumption about horn coloration. From this reason I believe the horn sound is not in the depth but something else, like the mouth round over, or from the expansion, or from multiple things like some audible issue moving higher or lower in frequency where its not that audible anymore. Describing problems as ripple and knowing that edge diffraction makes that from mouth size up to beaming, the deeper horn would perhaps have reduced bandwidth of diffraction related secondary sound source and related interference ripple than a bigger mouth/shallower device. Fix is good ol' huge roundovers.
I'm totally guessing it, I've never heard such speaker so can't say anything about any audibility, or anything really 🙂 all I know much things change between two devices, unless very tightly controlled, so its always hard to say what actually makes the audible differences. It would be very interesting to hear such thing and tune out, to really find out what makes bad sound.
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Thank you.
To picture it in my head: are you thinking (for example) something like Inlow's 135Hs horn but with 2x 8PE21, meaning same horn mouth and length and taller throat to accommodate the two 8"?
In my mind that would lead to a horn with the same 875Hz mass corner on top, same lower reach driven by horn mouth, and double efficiency per the two drivers. Could this reach below 135Hz because of the two drivers?
FWIW I have 4 sealed 12" servo subs that I haven't tried running above 80Hz so would have a hole up to where the horn would take over.
No, I pass them at about 200Hz and use satellites. More like a 2.2 set up. The satellites are run FR as well.
Also the horns are much better when placed on their sides. Upright might work for theatres but not in outdoor applications.
Attachments
Although all this wonderful information makes sense to me but then it doesn't make sense if I take the example from the first post. The speaker has a claimed FR of 36Hz - 20kHz ± 2dB with a crossover at 850hz
https://www.blumenhofer-acoustics.com/Products/SerieCorona/Corona-2x220/Corona-2x220.php
Is that 'horn' mainly for show then, or what? If I read everything here correctly, it shouldn't reach that low, and probably not that high.
https://www.blumenhofer-acoustics.com/Products/SerieCorona/Corona-2x220/Corona-2x220.php
Is that 'horn' mainly for show then, or what? If I read everything here correctly, it shouldn't reach that low, and probably not that high.
This is a good thread you started CoolJazz, wealth of information to absorb and consider. Cheers for that!
I'm in the "trying to make sense" camp too ... the Corona example seems more of ported cabinet with a very shallow horn to slightly aid with the mids? Doesn't seem like the horn around the large drivers would dominate the overall presentation but perhaps add to in a subtle way. Without hearing it, curious to know how the experienced heads here perceive that particular design.
I'm in the "trying to make sense" camp too ... the Corona example seems more of ported cabinet with a very shallow horn to slightly aid with the mids? Doesn't seem like the horn around the large drivers would dominate the overall presentation but perhaps add to in a subtle way. Without hearing it, curious to know how the experienced heads here perceive that particular design.
CoolJazz questioned the usable response of some of the designs shared here, noting the sims rolling off the high end. It didn't align with higher crossover points mentioned.
Knowing the mass corner theoretically exists and the simulations are never going to be the actual response, I'm thinking the HornResp sims roll off the high end too much. At least by half octave if not full octave. After inputting a straight forward ported cab I own, the sim was off by one octave to my measured in room response. Sim shows 600Hz, measurements show 1200Hz.
Is that to be expected or do I need to give my head shake ?
Knowing the mass corner theoretically exists and the simulations are never going to be the actual response, I'm thinking the HornResp sims roll off the high end too much. At least by half octave if not full octave. After inputting a straight forward ported cab I own, the sim was off by one octave to my measured in room response. Sim shows 600Hz, measurements show 1200Hz.
Is that to be expected or do I need to give my head shake ?
Raw driver simmed response is limited to its Fhm, inductance, so input the latter and you get WinISD's flat line to 20 kHz.
The box/horn since T/S theory peters out at the driver's effective upper mass corner:
upper: Fhm = 2*Fs/Qts'
lower: Flc = Fs*Qts'/2 (AFAIK only used for reactance annulled BLHs)
Qts': 2*Fs/Fhm
Maybe more easily understood from a horn loading POV along with all the extra math (pg. 7):
http://www.xlrtechs.com/dbkeele.com...Preprint) - LF Horn Design Using TS Paras.pdf
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
(Rs) = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor and/or there's other series resistance.
Indeed! Some Altec measurements among which compares the Altec 'deep' cone Vs JBL's 'shallow' cone (pg. 5).