I've seen talk on the net about the function of the upper chamber in the Model 19. Specifically that it was a reverberant chamber. In one of my shop built enclosures, I did not join the upper and lower chambers. Other than further extending the bass, am I missing something? If I am, is the size of the opening between the upper and lower sections critical?
Technically, it's an acoustic band-stop filter, which normally is used to notch out a peak in a signal's response and while I haven't modeled it, it seems more a byproduct of the desired 'look' than intentional performance tweak since the net volume [Vb] combined with large vent area [Av] of it implies a very high tuning, not to mention I've never seen/heard anything from Altec about it, so apparently of no marketing benefit. In short, a doubled tuned reflex.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Thanks GM. I figure 3-4" holes would do it. You agree?
???
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
I meant 3 4" holes in the underside of the upper cabinet and the same in the lower; the cabinets separated by the specified riser/throat.
You're welcome!
Well, this will tune the resonator [horn box] lower than stock due to the vent will being smaller. Since this is a simple Helmholtz resonator its tuning [Fb] can be 'ballparked' with an online calculator, but can't find my notes where I calculated its net volume.
Ideally need to measure your two to see how it affects the frequency response.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
I wonder if the notch somewhere around 400 Hz is it? http://usr.audioasylum.com/images/0/...erresponse.jpg
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
The "hole" that connects the upper and lower chambers is rectangular and is nearly as large as the inside dimension of the 2" piece that resides between the two.
A few 3" holes would result in a weird effect I'm sure.
I had mine completely apart at one time an have photos....somewhere.
I may have posted them here, but the search function does not seem to be working?
Ron
Enjoying Altec Speakers since 1972
Nope, get 'failed' messages for both regular and advanced searches.
GM
- - - Updated - - -
Tried Googling altec m19, hostboard and got a bunch of links, so guess this is the way to go for now.......
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Here's a guy that does a whole series on taking apart an M19 and cleaning it all up etc. I took a quick look and you can get a good idea of the opening size to the upper horn chamber at around the 4:41 -49 mark in this video. https://www.youtube.com/watch?v=_NaQ2NGfum4
Cheers, Dave.
Last edited by DaveCan; June 12th, 2017 at 08:51 PM.
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