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Multi-Way Conventional loudspeakers with crossovers

Which 15" transducer for Altec VOT/825/A7?
Which 15" transducer for Altec VOT/825/A7?
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Old 2nd April 2019, 04:51 AM   #31
GM is offline GM  United States
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You're welcome! Understood, I happen to be intimately familiar with this cab alignment, having used it as an example when being taught horn design basics way back when, so knowing the flare frequency, etc., makes it easy in HR, though if you know it you can juggle mouth area Vs length till it calcs the correct one.

HR can be confusing WRT truncated horns in that the pioneers designed a full size horn [this one was originally described as a 1/2 size 55 Hz expo], then cut a 'slice' out of it at the desired throat area and further down as required to meet the needs of the app.

GM
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Old 2nd April 2019, 08:31 AM   #32
bob4 is offline bob4  Germany
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I corrected the input parameters, now I have the correct flare frequency of 110 Hz. Marginal differences. I did 0.5PI and 2PI, comparing the Beyma SM115N to Fane Sovereign Pro 15-600. Due to a bit higher xmax and higher tuning, the Fane would take a few watts more and be 2-3 dB louder, but with an uneven response. The beyma still comes out with a smoother curve in 0.5 PI.

125 dB with 40 Watts

Any thoughts on these response curves?

(Couldn't resist setting S1 to 640 cmsq, since that is the actual baffle cutout )
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File Type: png BeymacorrInput.PNG (48.8 KB, 103 views)
File Type: png BeymaVsFaneCOrr.PNG (66.5 KB, 107 views)
File Type: png BeymaVSFane2PI.PNG (62.4 KB, 106 views)
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Old 2nd April 2019, 07:37 PM   #33
Cal Weldon is offline Cal Weldon  Canada
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Which 15" transducer for Altec VOT/825/A7?
Yes, they are good at disturbing the neighbours.
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Old 3rd April 2019, 07:08 AM   #34
GM is offline GM  United States
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Why is this in the FR forum?

GM
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Old 3rd April 2019, 08:01 AM   #35
bob4 is offline bob4  Germany
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I don't know, I was wondering about that myself.... when Cal did the "surgery", he announced that this thread shall be moved to the "multi-way" subforum....

EDIT: I wouldn't mind at all, more attention for my thread
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Old 4th April 2019, 08:38 AM   #36
bob4 is offline bob4  Germany
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Quote:
Originally Posted by GM View Post
Yes.

Sorry, no; between the wrong throat and not factoring in that its axial length is sloped down some, the 110 Hz flare couldn't be made.

Compression ratio, i.e. horn throat [St] = driver effective piston area [Sd].

Yeah, though judging by some sims I've seen posted recently it may be possible in HR now, but a very low priority for me, and none for you since tuning will be done empirically.

GM
GM, since you seem to have some A7 records in your hornresp, would you mind sharing some frequency plots, and which woofers you have simulated. It would be nice to compare. Also it would be much appreciated if you have any comments in regards to how these simulations correlate with your experience? Do you happen to have measurements of any A7 configuration?

best regards,
Bob
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Old 15th April 2019, 01:08 PM   #37
bob4 is offline bob4  Germany
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FYI,
Wood has arrived, Beyma woofers have been ordered..... I will try to present some results later on when it gets built, but i am not building it myself. It is a friend's project.
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Old 15th April 2019, 02:41 PM   #38
Cal Weldon is offline Cal Weldon  Canada
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Which 15" transducer for Altec VOT/825/A7?
I musta goofed and merged the wrong way. We are in Multi-way now.
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Old 16th April 2019, 09:38 AM   #39
GM is offline GM  United States
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Quote:
Originally Posted by bob4 View Post
GM, since you seem to have some A7 records in your hornresp, would you mind sharing some frequency plots, and which woofers you have simulated. It would be nice to compare. Also it would be much appreciated if you have any comments in regards to how these simulations correlate with your experience? Do you happen to have measurements of any A7 configuration?

best regards,
Bob
Actually, I don't, just the 803A I did to show you the horn inputs. As for measurements, we had no need way back when as all Altec designs were well documented by them, though sadly, EV destroyed any paperwork they didn't need, so limited to a relative few plus whatever DIYers have posted.

Note too that available drivers were for the most part all of a 'sameness' for max interchangeability for each genre of speaker types with W.E./Lansing/Altec being the most copied. Haven't paid much attention to current production, but from what little I've noticed, nothing's really changed in prosound, cinema, M.I. apps beyond the usual improvements in CAD, etc., materials, manufacturing.

As for choosing drivers, the horn 'rings' at ~220 Hz, the mean of its 110-440 Hz BW, so in T/S parlance we ideally want the driver mass corner [Fhm = 2*Fs/Qes'] to be ~220 Hz and ~440 Hz like the average 803A if driven with a period correct matching impedance to drop it back down.

Later Altec drivers don't spec too close until one factors in thermal power distortion, so somewhat misaligned for HIFI/HT apps, ergo ideally one would dial in a bit of some form of series resistance to smooth it out, though few do, or use whatever Fs, Qes driver that meets the 'magic' ~220 Hz Fhm spec and of course there's still the issue of having the right amount of breakup modes BW to fill in above the horn's upper roll-off.

The sims are fine for comparing basic horn response for comparison, but that's it as there's not enough there to have any real correlation with how they sound, though if we can properly sim the back box we might can get an idea of how it sounds, though frankly, it's been so many decades since I've been exposed to them, especially in a HIFI app, that I wonder if I would recognize it if blindfolded since they don't sound like horns at all when properly 'voiced', damped, just very open, efficient, dynamic speakers with excellent [projected] vocals combined with a rolled off bass if not hard in a corner.

Most folks though seem to prefer them as the cinema/PA/MI sound systems they were meant for though, so too 'raw', harsh for me except as dance party speakers or behind screens in the neighborhood cinemas and the couple of early HTs I was exposed to.

Even consumer speakers with horns I prefer with grills and what we nowadays call CD horn EQ, but most don't, though with the M19's mouth foam combined with its more adjustable XO, one can do similar and of course designed as a whole system with period correct matching impedance tube amps with variable DF tone controls + horn baffles, all of this becomes moot to all but the inveterate tinkerer.

GM
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