question on my DIY A7-500 of many years past,,

**Derry** · April 24th, 2010, 09:10 PM

I could not afford the factory built Altecs in 1965 so I purchased parts and built my cabinet (A7-500) to work with my Dynaco 70 which I also built,, the Dynaco is long gone but the Altec DIY speakers have gone through two kids and are now back home,,

I still have all the original literature and price sheets,, the parts I purchased were:

N-800E network $46.50
806A driver $57
811B horn $24
416A speaker 15" $63

everything is in excellent condition and seems to be working great,, I do notice the lack of much bass even though that woofer is rated to 20HZ, I believe real world is more like 40 or 50HZ,,

my two questions are:
1. would it be worthy to replace any of the components in the network,,??
2. any way to increase the bass,,??

thanks

Derry

**voice of the theater** · April 24th, 2010, 09:29 PM

First of all--I'm a little confused about your setup--can you post some photos?? You're calling it an A7-500 but you're not using all the A7-500 components. I'm assuming you mean that you built an A7-500 cabinet to Altec specs and you installed the components that you've listed (which are not all A7-500 components). The A7-500 would have a 500 hz crossover (not the 800 hz one that you're using), also would have a 511 horn and not an 811b etc. Anyways, to answer your questions--to improve the sound of your speaker system you could start by replacing the capacitors in the crossover. After 45 years they have probably shifted far from their original values and that can change the sound of your speaker system (for the worse). Without seeing your cabinet, you may be able to coax more bass from your speaker system by reducing the size of the port ("blocking off" part of it) either through experimentation (trial and error) or by a more scientific approach which I'm sure others here on this forum will know much more about than myself. If you try those two steps and still hear the need for further improvement, you could ship your drivers to Great Plains Audio to have them remagnetized (and possibly reconed/rediaphramed--if needed)...

**Altec Best** · April 25th, 2010, 10:25 AM

Originally Posted by Derry

but the Altec DIY speakers have gone through two kids and are now back home,,

I still have all the original literature and price sheets,, the parts I purchased were:

N-800E network $46.50
806A driver $57
811B horn $24
416A speaker 15" $63

First off to see that the speakers are now back at home and still functional is Awesome :2thumbsup:That really shows Altec's build quality.But as V.O.T. has suggested the woofers probably need to be rebuilt Cones,Remag,etc..

Crossovers same thing - Rebuild

I love the prices for the componets most definately

$60 bucks for a brand new driver

**Derry** · April 25th, 2010, 11:52 AM

thanks for the comments and directions, will pull the crossovers and see what is inside for replacement,,

after looking at the literature I guess I built the an A7-500 cabinet with the 800 network and the components that were meant to accompany it as they were priced less,, think I was making about $450 a month back then so this purchase was very expensive,,

I have attached a few photos as well as the 1965 price listing attached to the Altec literature,,

yes that is a vintage AR2a in front of the VOT that has just been reworked,, now hooked up to the Marantz and sounding very good,,

seems a lot of my aged equipment I passed on to the kids is now returning,, they gave back a Fisher tube receiver (model 400) that is working, a Pioneer turntable which I had to replace the drive belt and the AR2as,, they still have a few sets of Pioneer speakers they have had reworked and are part of their present audio system,,

great forum and sure I will be asking more questions as the VOT rework starts,,

thanks

Derry

**Old Guy** · April 25th, 2010, 12:03 PM

Originally Posted by Derry

thanks for the comments and directions, will pull the crossovers and see what is inside for replacement,,

after looking at the literature I guess I built the an A7-500 cabinet
Derry

Just an A7 cabinet actually, there is not an A7-500 cabinet.

The A7 box can be re-tuned, there are a number of discussions here if you search...

And of course there is always the sub option.

Glad to see the old soldiers still mustering...

**Derry** · April 25th, 2010, 12:18 PM

thanks Old Guy, will see what all I can read here to retune the cabinet as part of the rework,,

have an SVS 13 ultra for the real bass but would like the Altecs to be able to perform at a respectable level,,

Derry

GM · April 25th, 2010, 01:42 PM

Originally Posted by Derry

I could not afford the factory built Altecs in 1965......................think I was making about $450 a month back then so this purchase was very expensive.......

.........everything is in excellent condition and seems to be working great,, I do notice the lack of much bass even though that woofer is rated to 20HZ, I believe real world is more like 40 or 50HZ........

my two questions are:
1. would it be worthy to replace any of the components in the network,,??
2. any way to increase the bass,,??

Sounds familiar! In '64 I DIYed the model 825 cab too, though for an A7-500 Vs your 800 Hz A7 (AKA A7-8) variant, though you did better than me salary wise, I was only making $375/mo..

That said, you left out the horn flares, so instead of a crude reflex loaded front and back loaded horn you created a very high tuned 6th order band-pass (BP) alignment, so missed out on the A7's sonic 'magic'. Assuming you're still not interested in the woodworking required to add them, at the very least I recommend lining all surfaces except the baffle of the woofer's front chamber and all of one side, back, and bottom of the back chamber with 1" acoustic fiberglass insulation or similar to smooth out its response.

1) As already noted, the XO's caps if they're original since oil caps this old tend to be way out of spec. Of course, clean terminals and replace any wiring that shows any corrosion with the insulation peeled back a bit.

2) Right, stock tuning is ~65 Hz, so F3 = ~46 Hz. To keep this simple, consider the cab a ~12.66 ft^3 reflex, so reducing the vent's area will lower Fb which will roll off its LF band-width (BW), ergo the only way to flatten it to this lower tuning is by trading efficiency for BW with a baffle step compensation filter (BSC) if the woofers haven't lost much of its motor strength over the decades. If this is done, then the horn will be too 'hot', requiring additional shelving to tonally balance it out.

GM

**Panomaniac** · April 26th, 2010, 01:34 PM

Very cool! Nice to see that your babies have come home to papa.

You do have a sort of odd duck, there. No horn flare in front of the 15", as mentioned above. That's really going to change things. Maybe you could put one in?

Definitely close up that big port you've got there. For my cabs a port of 19.5Wx3.5Hx6.25 deep did the trick. Bass is much more extended and less boomy. Port tuning is going to be room and taste dependent, tho.

Also (as mentioned above) be sure to put in insulation. Fiberglass, rock wool or some of the "Bonded Logic" all cotton insulation, if you can get it. Those are the things to do 1st, before you embark on crossover work.

Just FYI. The $63 you spent on each 416A driver would be about $430 in today's money. It all works out. =)