830a Mod

**Mustang Marvin** · December 2nd, 2015, 01:12 PM

I would like some insight on building a pair of 830a corner cabinets. I would like to remove the horn and replace it with a port for improved bass. I will use 2 416c's.
Any help is appreciated.
Marvin

GM · December 2nd, 2015, 08:58 PM

Hmm, the lone 830 I've seen 'in the flesh' is vented in Altec's tried n' true 'horn-in-vent', though semi-aperiodically damped with three thick fiberglass insulation pads since it's acoustically way too small for dual 803/416s in a sealed alignment, much less a reflex; that, and there's no gasketing on the side panels, so leak here also at higher pressures.

A quick Google confirms it: https://www.google.com/search?q=alte...sAQIIg#imgrc=_

http://www.soundup.ru/images/stories...-systems-7.JPG

Anyway, other than some basic catalog dims and scaling off a monitor, don't know of any accurate drawings 'in the wild'.

GM

**Mustang Marvin** · December 3rd, 2015, 11:48 AM

Thanks M,
Thats pretty much my take as well. My idea of a mod would be to actually seal the box and using a port instead of the horn. By my calc the port would be 8" in dia by 3.11" deep. The volume is stated as 9 1/4 cu ft. I would think this would make it a bass reflex box. (maybe)
I can find very little info in this system except pictures. I do have a diagram though. I like this design. It would fit nicely in my room.
Your thoughts...

**dbale** · December 3rd, 2015, 05:21 PM

Originally Posted by GM

Anyway, other than some basic catalog dims and scaling off a monitor, don't know of any accurate drawings 'in the wild'. GM

Not as wild as I used to be ...

If a 850A cabinet is an unloaded 830A they exist here.

**Mustang Marvin** · December 4th, 2015, 11:17 AM

The only info I can find for the 850a states it is a column Speaker. Some of the old info is hard to find. The only plans I can find for the 830a is in the "How To Build Speaker Enclosure" book byBadmaieff and Davis. Evidently there are not many people familiar with them. Even my friend Speakerman57 says the response was not as claimed. This is why I thought they could be modified to a bass reflex design for more bass.
Theoretically, does this make sense? I would doubt anyone has actually tried this.
But, I like the design and thought it would be possible.

**dbale** · December 4th, 2015, 03:12 PM

From 1959 catalog page
830A laguna
Cabinet without speakers may be ordered separately as model 850A

http://www.hifilit.com/Altec/1959-h.jpg

**Mustang Marvin** · December 4th, 2015, 04:56 PM

Dang, I guess I'm a little late with my order. I guess I just have to make my own.
I'm still waiting for someones opinion on the version I have in mind. By the way, I am using a GPA 399 with an 805 wood horn on top. Fantastic sound. Do you think my ported 830a would be a good match? It would be great to hear some advice from fellow speaker builders as to the idea.
Thanks,
Marvin

GM · December 11th, 2015, 04:51 AM

Originally Posted by Mustang Marvin

The only plans I can find for the 830a is in the "How To Build Speaker Enclosure" book byBadmaieff and Davis. This is why I thought they could be modified to a bass reflex design for more bass.
Theoretically, does this make sense?

Gees, I'm really losing it memory wise as I've got two printings of this book and quoted out of it many times over the last couple of decades, including here.

Not to me since the cab is too small for venting dual 416s unless you don't mind needing a separate sub system to fill in the bottom 2-3 octaves and why the original is basically a leaky 'sealed' alignment. You can tune it low of course, but it probably won't have much bass even corner loaded unless it's a small, well-constructed/sealed room.

Now if you make it a true floor model to increase its net volume [Vb] a bit, then this makes some sense. Another thing is that it's more a 'pretty face' than a proper speaker cab construction wise, i.e. not meant to play modern recordings at > a fraction of the driver's power rating. I mean at the time, recordings typically ran out of 'steam' around 80 Hz same as prosound apps till fairly recently.

BTW, the 9.25 ft^3 must be its shipping size since a quick scaling and making a few material dimensional assumptions [no need to have exact dims for all the woodworking details], the net volume is only around 5.75 ft^3, so ~6.35 ft^3 minus the vent if it's other than baffle thickness, small even for a single sealed alignment if other than for a T/S max flat driven with a modern SS amp or at least a very low output impedance PP tube amp.

Anyway, be back as time permits with more details, etc..

GM

**bowtie427ss** · December 11th, 2015, 08:49 AM

If you want to get radical, yet stay reversible.............. Unhook one of the 416's and use it as a passive radiator. You can tune it by adding mass to it's cone, and add an L-pad across it's terminals to tune the damping to a degree.

**Mustang Marvin** · December 11th, 2015, 09:26 AM

Thanks to both replies. It's good to hear from you. I haven't been on the forum in awhile.
Great information. I think I will pass on the 830's. I still have the 416's. Any suggestions on a bass cab?. I really liked the corner aspect of the 830's. That's why I thought they might work.
I plan on ysing my 805 wood horns with GPA 399's for the highs. I love them.
Anyway, thanks again for the info...
Marvin