VOTT A5 - improved crossover design --- help!

[bradmich]

Hey Gang,

Longtime vintage audio guy however, my first entry into VOTT A5 – found a pair that needs a loving restoration.

I have a crazy plan to rebuild these like no other- All veneer cabinets, custom hardware, powder coat the horns etc. Question?

I’ve heard/seen several references to crossover upgrades/improvements but can't seem to find anything specific?

Can anyone point me to a schematic for 8-ohm drivers? (808a and 421a)

Will truly appreciate it and will post pics when done – it’s my stay-at-home covid, cold-as-crap outside winter project!


Thanks! Mark
2020 WTF | 2021 TBD

[Robh3606]

This will get you started

http://www.audioheritage.org/vbulletin/showthread.php?29391-Hiraga-s-crossover-for-Altec-A5x


Welcome!

Rob:)

[Mr. Widget]

Welcome to the forum, please post more info on what you have. Photos are always helpful and fun for us to look at. It is often the case that what started life as one version of a VOTT, ended up as a very different speaker. Your woofers may have been reconed into a different model and the diaphragms in your compression drivers may have been changed.

I am not an Altec expert, and with luck one of our members with far more Altec knowledge will pop in with better advice, but I am not sure if the 421A musical instrument speaker was stock or is now what you will want assuming home music playback as your goal. You may also want to upgrade your HF unit... after all if you are going to spend the time money and effort to veneer the cabinets, I would assume you want the best possible acoustic performance.

As an overall direction, once your drivers are determined then a proper crossover can be built or suggested. I would definitely use one that has frequency equalization built in to extend the highs. (similar to the network in the Model 19) For the cabinets, plan on adding significant bracing to reduce the inherent cabinet resonances.

This will hopefully be a very fun and rewarding project.


Widget

[bradmich]

Hey Gang

Included some pics... hope this helps
Yes- Plan is to use them for home theater
Did not want to make a repeat of the existing design - as I understand there are improved designs out there.


87931

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[bradmich]

87936

Like most of you here, I just hate seeing vintage gear getting kicked around and going to waste... drives me crazy.
I know VERY little about Altec - so do appreciate your advice and feedback.

Thanks! Mark

[Riley Casey]

I don't remember A7s having 421s as stock bass drivers so you may have to re-invent the crossover wheel right off the bat.

[bradmich]

Argh!.. what "should" be the right drivers?

[Mr. Widget]

You have one of the right drivers, but not necessarily one of the best drivers. Not sure who told you that you had an A5 system, but it appears you have the 1208A system which was a PA speaker that used the VOTT cabinet, the 808-8A compression driver on a 511B horn and a 421A musical instrument woofer. Which horns are your 808-8A drivers mounted to?

This system is less hi-fi than even a stock VOTT A7-500, which would be a better starting point. If it was my project I would research the most linear driver compliment, use an updated crossover, brace the cabinet, and be off to the races.


Widget

[grumpy]

A5 - 515 variants
A7 - 416 variants

The horn and driver were also varied over time and options. Looks like A5 usually had a large format compression driver (288) and bigger horn.

Expecting these are A7-like with the 511/A/B horn (?) ... there was also a 511E that accepted a larger format driver, but these are fairly rare.

I believe there are a number of threads with customization (bracing/retuning of cabs) of these systems floating around here somewhere.

[bradmich]

Widget, (serious) nice deduction on what these are! yes, 511b horns! ...Mr. Green, in the library, with the candlestick :)
The horns were mounted in the woofer baffle - assumed someone just wanted to save space.

Thanks Grumpy too!

OOOOOKKK, guess I'm starting raw.

What Woofers do you recommend (best ones) and is there a crossover Schematic you recommend for Home theater
...Assuming I keep the cabinets (Bracing etc.), 511b Horns and 808A drivers.

Many thanks! Mark

PS- you guys are good- know your stuff
(I was a car audio designer back in the 80's -designed systems for Lamborghini/Ford/Porsche.. appreciate good knowledge/experience).

[Mr. Widget]

PS- you guys are good- know your stuff
(I was a car audio designer back in the 80's -designed systems for Lamborghini/Ford/Porsche.. appreciate good knowledge/experience).There are several folks here who know far more about Altecs than Grumpy or I... unless Grump is a closet Altec head and I didn't know it. :D

I would look over some of the Valencia threads here to see what others have done. The Valencia is a domestic version of the VOTT.
If you put Valencia in the search box up top, you will be taken to quite a few threads that you may find useful. This will keep you busy while you wait for a true Altec expert to pop in.


Widget

[grumpy]

No expert here, just what I’ve picked up along the way :)
(and a 416b/511b set waiting for action).

IIRC, folks have flipped that cab, which gets the mid/woof up higher, and blocked off the horn hole (perhaps leaving some open space as a port). Then mount the horn etc on top, ala A7.

Later 802/902 model compression drivers with the lighter diaphragms are worth looking at for home use.

The Valencia woofer doesn’t have the short horn of the A7, so it might be worth googling A7 mods/networks for home use... would make sense to keep the HF horn eq bits to bring up the top end, and up the crossover freq to maybe 800Hz+ (Easier on the diaphragm and perhaps less horn sound)

[bradmich]

Thanks gents...

I talked to Bill @Great Plains Audio.
He can re-cone the 421s to 416s so all good there!

I'll send pics when they're done... likely 2-3 months from now...