compensating driver and horn

[sailor]

Hi, I am new to this forum and new to playing with horns. I have recently obtained a pair of Altec 902-8A drivers and 511B horns and wish to crossover at 800Hz and realize that compensation is required in the XO. The 15" bass driver is also 8 ohms. Can anybody direct me to a suitable schematic. If the circuit has a pot in it for adjusment then I would probably replace this with a large 4 position rotary switch with appropriately chosen fixed good quality resistors.

[Zilch]

http://home.earthlink.net/~jmarkwart/

[sailor]

Thanks Zilch, the link you supplied deals mostly with the 604 crossover, providing phase and HF compensation. I am looking to XO at 800Hz with compenston to suit the Altec 902 + 511B combo. Could anybody direct me to a suitable schematic. I have had no success searching for this.
Regards

[Zilch]

The Model 19 crossover is there in the left column. The 811 and 511 horns behave similarly. The 604 crossovers are derivatives.

That "dual control" variable compensation approach was used in later versions of VOTT, I believe, though I've never seen a schematic. Someone on the Altec forum may know more.

Here's my sim analysis of the M19 version:

http://audioheritage.org/vbulletin/s...26&#post128826

[CONVERGENCE]

Hi,

I found this model 809 XO.

Here is the site for schematics.

http://www.altecpro.com/pdfs/vintage...0Schematic.pdf

You also have the N801-8a 8ohms 100 watts
and the N800D 75 watts 16 ohms.
.................................................. ..

[sailor]

Hi Zilch, I tried Jeff Markwart's site but the model 19 XO links to a pdf "courtesy of Jim Easley" which opens as a blank page. Also tried the link Convergence kindly provided but once again another blank page. Having no luck here will try a cookbook approach for 800Hz XO. My 15" speaker is about 11 ohms at this frequency but I don't know what the Altec 902-8A is. My problem is what components and what values do I need to compensate this compression driver when mated to a 511B horn. Any help and advice greatly appreciated.
Regards.

[speakerdave]

Here's the 809:

[Zilch]

You've got to "Click here to download file" on the Markwart site pages to get the PDFs.

Here's the M19 network. R1 is the HF adjustment and R3 is the MF. I use the series leg of an 8-Ohm L-Pad for R1, and the parallel leg of another for R3. I believe you can split L1 and R1 out of the LF circuit, though I haven't verified that through testing. It acts as a variable step filter there, but the sims don't reveal it as significant.

[sailor]

Hi Zilch, Thanks for the schematic. Can I asume that the 6uf cap across the two 3.9 ohm resistors forms the compensation and can I just add this to a 800Hz cookbook XO. Any idea what the Altec 902 impedance is at this frequency?
Regards.

[Zilch]

Hi Zilch, Thanks for the schematic. Can I asume that the 6uf cap across the two 3.9 ohm resistors forms the compensation and can I just add this to a 800Hz cookbook XO. Any idea what the Altec 902 impedance is at this frequency?
Regards.

http://audioheritage.org/vbulletin/s...35&#post160635

No impedance info on 902, sorry.

You need the whole deal to control the compensation, of course.

See the sim:

http://audioheritage.org/vbulletin/s...689#post128689

It's blue curve @ #4, basically.

For more compensation, you need the midpoint R to common.

Max compensation shown is with the fixed 2 Ohms only, blue @ #3

See also:

http://audioheritage.org/vbulletin/s...762#post160762

[spkrman57]

Hi Zilch, Thanks for the schematic. Can I asume that the 6uf cap across the two 3.9 ohm resistors forms the compensation and can I just add this to a 800Hz cookbook XO. Any idea what the Altec 902 impedance is at this frequency?
Regards.

The 902 1" driver will deliver a better top end close to the rated 18khz limit starting at 1500hz rather than 800hz.

I use 902's in several of my system projects. I've used them with 511B/811B/Edgar tractix round wood horns/etc.... I have found starting a octave higher will deliver better response approx a octave higher.


Just another quick opinion comparing JBL 2426 and Altec 902 1" drivers.
The JBL is nicer on the midrange while the Altec is better on the upper frequencies.

Ron (2.5 cents worth)

[Tom Brennan]

FWIW I once had quite nice results using 2426s on Altec 1005 multi-cells. As I recall the highs were nicely extended and the sound was very fine.