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aaadougford
03-29-2011, 06:46 AM
I currently have a 811B horn with 806A driver and a N800-D network. I want to change out the network and HF driver to make everything 8 ohm as the original speaker specs for Altec Santiago's were. To add, I will be replacing the N800-D with a N801-8A network as was originally. Since the original HF 806-8B is such a rare bird to find I'm considering either a 806-8A or 902-8B. Is there a reason to use one over the other. Is there something other I need to consider?

Thanks,
Doug

Earl K
03-29-2011, 02:00 PM
Hi Doug,

Since the original HF 806-8B is such a rare bird to find I'm considering either a 806-8A or 902-8B. Is there a reason to use one over the other. Is there something other I need to consider?


If they were mine , I would be inclined to first work with what I have, to see if I could achieve some sort of sonic satisfaction .

If the 806A can't be made to work out ( as in the following suggestions ) you might consider buying GPAs ( alnico ) 802-8G mkII driver .

Here's a sweep ( done by Zilch ) of an 806A on both a 511 & 811 ( from srbliss, wiredbecker ?? ) / the purple sweep has HF compensation of some type ( midrange padding ) applied .


http://www.audioheritage.org/photopost/data//500/Zilch_806_on_811_511B_.PNG

- That purple trace is a pretty good looking sweep ( for both both low-end & high-end extension ) /// it shows ( the possibilty of ) much better performance from an 806A, than what is typically displayed by the drivers detractors .

- The weaker motor system of the 806 appears to not induce as much midrange roller-coasting as the 802 motor ( ie; some of the typical notches at 3 K & 7-8K, are not as pronounced ).

- See ( for more dramatic "rollercoasting " );
http://www.audioheritage.org/photopost/data//500/SkyW_811vs511_902_35480_PlusSize.PNG

Of course , one can see that to achieve the linear response ( of the first pic ) one needs to shed, @ 12 db of midrange energy .
- 12 db of padding means, that the 411-8A woofer ( like you have ) could be a workable match ; ( 102 -12 = a woofer of roughly 90 to 93 effiency to match up to ) .
- This assumes ( of course ) that transducers of equal impedance which I think is not really the case ( though I think the 806A is more of a 10 to 12 ohm driver / not 16 ohms ).

Crossover :

-The N809-8a I believe is the same as the N801-8A , but with different connectors .
http://www.audioheritage.org/photopost/data//500/N809-8A_Network.png
- You could build this from scratch with parts from P.E. instead of getting an N801-8A from eBay .
- Anyways, if you start with this topology and then graft the following HF compensation onto it ( placed just before the drivers ) / you should have achieved a pretty decent starting point ( that should be highly listenable ) .

- BTW, R3 ( part of the woofers Zobel ) can vary from 5 to 8 ohms . I think I'd simply make it 8 ohms to start with .

http://www.audioheritage.org/photopost/data//500/Altec_30904_30923_filter.jpg

- FWIW,,, here's a single LF predication ( box/woofer alignment ) for the 411-8A in a 6 cu ft box , tuned to 25hz .
- If you are thinking of building new cabinets, then download WinISD Pro (http://www.linearteam.dk/default.aspx?pageid=winisdpro) and play around with a few different box sizes & tunings .

http://www.audioheritage.org/photopost/data//500/Altec_411-8A_in_6_cu_25hz.png

<. cheers, EarlK