Help ! Heresy 1 and Altec 811

[marmelbirne123]

Good Day 😃

This is my first posting here and i hope you can help me with my questions. i recently bought a set of 1980 Heresy 1 - They sounded good to me to the point i got myself a

Stromberg Carlson ASR 433 - So i asked a friend and we did this impedance correction mod. Then it sounded super nice but i was still hungry for more. After that, a friend lend me his altec 811 Horns, so i got me some horn-mount adapters, pulled out my K55V´s and mounted them on top of the Heresy! Wow! What a big suprise it was...But i came to the point where i thought the midrange was too loud...of course i thought, the Horn is much bigger than the original one. So i googled and came across this mod where it says: You can lower the midrange by changing the taps on the autotransformer and adding an resistor across the network? BUT: I only want to lower the midrange. This mod includes changing the tweeter to another tab...but is it possible to ONLY lower the midrange - 3db and leave the tweeter like it is? Am i one the correct way or is that all bullshit?  Also i planned to maybe mount the Tweeter above the Altec. Is that a better idea than leaving it inside the cabinet? Any more tipps how to adjust the crossover are very appreciated!

Thanks and all the best from Berlin, Germany

😎

 

Edited July 1, 2019 by marmelbirne123

[glens]

3 hours ago, marmelbirne123 said:

is it possible to ONLY lower the midrange - 3db and leave the tweeter like it is? 

 

Should be.  I'm not familiar enough with the crossover to say for sure without looking at the diagram, but it should certainly allow for what you want to do.

[karlson3]

how about putting a 16 ohm L-pad "before" your driver/horn combo?  You could take an adjustable L-pad and find a setting which sounds / measures right to you then replace the series and shunt Rs with fixed resistors of decent quality. 

(811 and 511 make good midhorns)

 

 

[marmelbirne123]

6 hours ago, karlson3 said:

how about putting a 16 ohm L-pad "before" your driver/horn combo?  You could take an adjustable L-pad and find a setting which sounds / measures right to you then replace the series and shunt Rs with fixed resistors of decent quality. 

(811 and 511 make good midhorns)

 

 

fantanstic answer, thanks for the input so basically something like this would do the job? https://www.parts-express.com/speaker-l-pad-attenuator-50w-mono-3-8-shaft-16-ohm--260-254 .

And then i just replace it with a measured capacitor? Not sure what is meant by " shunt R´s with fixes resistors"

Thanks again!

[glens]

He's merely suggesting you find the "volume" level that's correct, measuring the resistances both in front of and across the l-pad output, then using individual higher-quality resistors instead of the l-pad.  The l-pad may "sound" just fine by itself.

[karlson3]

The L-pad should sound good enough and add some flexibility if the speaker is moved  -  - just mark its level position(s).    The tweeter could be placed "back" in the plane of the midrange driver.  If so then use felt or perhaps carpet on top of your 811 horn to reduce reflections.

 

Here's an L-pad calculator    https://www.diyaudioandvideo.com/Calculator/DriverAttenuationLPadCircuit/

 

say you wish to attenuate your 811 by 3dB - then enter the nominal impedance of your driver and the amount of attenuation (and a wattage - if interested)  Then the calulator will show the series and parallel ("shunt") resistors plus the power the driver receives.

 

For instance when 16 ohms and 3 dB attenuation are entered, the calculator shows

the values below.   One would use typically whatever 5% value is closest.

 

With the adjustable pad you can dial the amount of attenation in by experiment then if wanting to make a fixed L-pad,  measure the pad's series and parallel resistance with a multimeter and find which fixed resistors to purchase.

 

 

 

 

 

[Marvel]

On 7/1/2019 at 6:24 AM, marmelbirne123 said:

After that, a friend lend me his altec 811 Horns, so i got me some horn-mount adapters, pulled out my K55V´s and mounted them on top of the Heresy!

 

Did you leave the original midrange horns in the cabinets? I would assume you either plugged the hole where you removed the driver from the horn or also removed the horn and put a piece of wood over the hole in the baffle. You don't want to leave it open as a port. 😀 (you can do that, I believe my son did, with no ill affect)

 

Bruce

[Marvel]

Also, please note that the alignment between the mid and tweeter will be off more with the 811 horn. If the drivers/voice coil/diaphragms of the mid and tweeter are in alignment, there will be more clarity and better imaging. As an example, I put the tweeters from my La Scalas in separate small baffles and placed them on the top of the cabinets to the rear, over the midrange driver. It made a substantial difference in the sound (for the better).

 

Bruce

[marmelbirne123]

....ok that seems very logical to me. Does it make any difference WHERE in the crossover i sold in the L-Pad ?

12 hours ago, karlson3 said:

The L-pad should sound good enough and add some flexibility if the speaker is moved  -  - just mark its level position(s).    The tweeter could be placed "back" in the plane of the midrange driver.  If so then use felt or perhaps carpet on top of your 811 horn to reduce reflections.

 

Here's an L-pad calculator    https://www.diyaudioandvideo.com/Calculator/DriverAttenuationLPadCircuit/

 

say you wish to attenuate your 811 by 3dB - then enter the nominal impedance of your driver and the amount of attenuation (and a wattage - if interested)  Then the calulator will show the series and parallel ("shunt") resistors plus the power the driver receives. 

 

For instance when 16 ohms and 3 dB attenuation are entered, the calculator shows 

the values below.   One would use typically whatever 5% value is closest. 

 

With the adjustable pad you can dial the amount of attenation in by experiment then if wanting to make a fixed L-pad,  measure the pad's series and parallel resistance with a multimeter and find which fixed resistors to purchase. 

 

 

 

 

 

 

[marmelbirne123]

12 hours ago, karlson3 said:

The L-pad should sound good enough and add some flexibility if the speaker is moved  -  - just mark its level position(s).    The tweeter could be placed "back" in the plane of the midrange driver.  If so then use felt or perhaps carpet on top of your 811 horn to reduce reflections. 

How is that meant? The midrange driver (K55V) is mounted on the Altec811 via adapter plate. You mean i remove the horn of the tweeter and just insert the tweeter driver next to midrange driver? 👀 I once saw that someone placed his tweeter and horn inside his Altec 811 horn, not sure though how he got it fixed in there.

[marmelbirne123]

12 hours ago, Marvel said:

 

Did you leave the original midrange horns in the cabinets? I would assume you either plugged the hole where you removed the driver from the horn or also removed the horn and put a piece of wood over the hole in the baffle. You don't want to leave it open as a port. 😀 (you can do that, I believe my son did, with no ill affect)

 

Bruce

No, i  stuffed em with some cotton wool from both sides. ✌️

[marmelbirne123]

12 hours ago, Marvel said:

Also, please note that the alignment between the mid and tweeter will be off more with the 811 horn. If the drivers/voice coil/diaphragms of the mid and tweeter are in alignment, there will be more clarity and better imaging. As an example, I put the tweeters from my La Scalas in separate small baffles and placed them on the top of the cabinets to the rear, over the midrange driver. It made a substantial difference in the sound (for the better).

 

Bruce

Yes, i already thought about it. Bummer is: One of my Heresy has a k52H driver. Never heard a difference but what would you suggest ? replace all 4 diaphragms at the same time but also on different types of drivers?