Model Nineteen Bass Response?

[Tom Brennan]

How deep do they go? Has anyone measured them, or worked out the math for theoretical f3?

Just curious.

[GM]

416-8B calcs a ~39 Hz F3/half space, but in a sim using MJK's advanced MathCad worksheet it's closer to a T/S max flat ~35 Hz, whereas the 416-8C calcs ~35 Hz and sims just below it, though with some under-damped peaking due to the cab being a bit too large for its lower Vas, Fs, Qts.

[Tom Brennan]

Thanks GM

[martyh45]

Hi GM, Did you model the shape of the box when you ran that or just the volume/port? I?m still curious regarding the effect of the constricted space between the upper and lower volumes.

[GM]

Originally posted by Tom Brennan:
Thanks GM

<font size="2" face="Verdana, Helvetica, sans-serif">You're welcome!

[GM]

Greets!

I modeled the height, width x depth, driver and vent location, but I shortened the height based on the losses due to the horn and 'p-i-n-c-h-e-d' portion since I had no other way to account for them. Still, the calc'd values assumes a ~uniform particle density and centrally located driver, vent, so the extra effort shows up in some downward shifting of F3, Fb.

WRT just the 'pinch', in modeling a stepped TL it doesn't affect the output enough to matter, so I assume it's not an issue with the M19 beyond some additional standing waves between parallel surfaces along any undamped walls, which shouldn't audibly affect the woofer's output.

GM

[gamalot]

Dummy questions here.

So, does this mean a 19 is tuned to 39 Hz if it has the 416-8B?

Is this measurable with equipment?

Is 39 Hz considered good or just OK?

Sorry but I don't honestly understand alot of the terms some of you refer to.

Gary

[bowtie427ss]

Not dummy questions at all Gary, until our teachers/mentors chime in i'll try to convey what i know.

The F3 of 39hz is the system(woofer+box) -3db point, sometimes called 3db downpoint. My understanding is that this is the point(on the frequency scale) at which the system's response has rolled off 3 db from the system tuning point(Fb).

A graphic representation of this would make it much easier to comprehend............. anybody have a screenshot from boxplot or similar modelling program?

The tuning point will be above 39hz.

If the system has the characteristic of a slow or shallow roll-off then the Fb or tuning point could be up to several 10's of hz above, in the case of a fast or steep roll-off(like a horn), the tuning point could be just a few hz above F3.

Remember a lot of designs seem to aim for a tuning in the neighborhood of 41hz, the lowest playing note of a standard tuned 4 string bass guitar.

Of course this can all be measured for verification, but the accuracy of the measurements depends on a strictly controlled environment(anechoic chamber) and precisely calibrated instruments, making it an expensive and time/space consuming task.

Is 39 Hz considered good or just OK?

<font size="2" face="Verdana, Helvetica, sans-serif">This is where it gets a bit confusing, while 39hz may at first seem a bit high relative to what we perceive with our ears, consider that the 19's response probably rolls off very slowly giving it great LF extension. The F3 of 39hz isn't enough information by itself to determine whether it's good or bad.

I really need to leave this to our seniors here, they can just say so much more while using much less verbosity.

[gamalot]

I was trying to match what I perceive with the 19s to the above numbers.
I feel 19s have very nice low end or at least all mine did with 416-8Bs, can't comment on the 8Cs.
I have heard a few complain they lack the low end and all I can think is something is broken or not functioning correctly. OR, that listener is one who likes muddy bass.

Am I wrong about this?

Gary

Gary

[LICORNE]

Quote from CBS technology centre.


The bass is somewhat on the robust side,although
nicely defined and free of boominess.


The middles have a touch of forwardness and the highs are clear and transparent,with a slight
mellowness that might be attributed to the rolloff
above about 12 khz.

But probably the most striking characteristic is
its stereo image which seems three dimensional
to the point of being detached from the speakers

The center of the image seems to extend forward
between the 2 speakers and toward the listener rather than rearward beyond the plane of the speakers as is usually the case.


http://www.altecpro.com/pdfs/vintage...r%20Manual.pdf

sold