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Another Electro Voice Interface D/Sentry VI thread.

As Peter mentioned, I'm also suggesting to remove the protection unit from the circuit.
Firstly, if it's rellais contacts are aged or corroded, they could cause the type of distortion by louder playing as you described.*
Vibration could simply cause loosing the contact in this case.
But even if this would not be the case, it is worth to remove protecion unit from the circuit anyway.
Once I've done this, I felt that hi tones became to play more openly, without adding any harshness or aggressiveness.
I don't expect you would use the Deltas for discoteque volumes later on :)
Good thing is that ST-350b or even ST-350a are only commonly available drivers for Deltas. You can buy them quite easilly. I have two spare pairs ST-350b I could sell one pair whenever needed.

* tweeters protection unit is working as following:
It cosists 4 diodes of "graetz bridge" connected parallel to the tweeter. as it has relatively high impedance, it has minimal influence on ST350's native impedance.
Once musical program's playing louder, the DC current/voltage coming from the graetz is also getting higher and higher. There's electrolytic capacitor connected to + and - poles of the graetz bridge and this one is more and more charging, following the average voltage of the graetz.
In certain moment the voltage on capacitor reaches the critical voltage to open the rellais, which is also connected to the capacitor's +/- poles.
Once the rellais is opened, audio signal current is not going via rellais contacts anymore. It starts to flow via protection lamp instead (lamp is connected between both sides of the rellais contacts).
Then that lamp (tungsten filament) becomes additional resistance in the circuit and start eating dangerous over current instantly. Moreover, it's resistance is not linear.
The higher current/voltage, the higher resistance. In certain moment the lamp becomes glowing then and this way protect even more while indicates that your should decrease volume significantly.
If you don't follow or even further increase volume, the current thru the lamp's filament exceed critical level, the lamp gets burned and circuit/tweeter becomes instatnly disconnected.
If this circuit is calculated and adjusted properly, in most cases it will save the tweeter against damage from continiuosly loud signal.
But nothing's perfect. The aging of parts can change the proper protection levels.
Also this unit will not protect against very fast but extremely short peaks in the musical program. Another effect of this protection unit is negative impact on the sound quality. It's due to the fact that signal of tweeter is in charge of passing additional cables but mainly rellais contacts.
My decision was clear, I've disconected that unit to get less protection but better sound.
 
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elektroboy said:
I'm also suggesting to remove the protection unit from the circuit.
Firstly, if the rellais contacts are aged or corroded, they could cause the type of distortion by louder playing as you describe.
Vibration could simply cause loosing the contact in this case.
But even if this would not be the case, it is worth to remove protecion unit from the circuit anyway.
Once I've done this, I felt that hi tones became to play more openly, without adding any harshness or aggressiveness.
I don't expect you would use the Deltas for discoteque volumes later on :)
Good thing is that ST-350b or even ST-350a are only comonly available unit. You can buy them easilly. I have one spare pair ST-350b
I could sell if needed.
Click to expand...

Thanks for the help. Since I now have holidays I am going to repair them as soon as possible.
Do you mean the lamp with protection unit?
 
Khaefeli said:
One last question. What do you mean with relais?
Click to expand...
I meant "relay", just wrote that word in german instead of english. sorry ;) \
https://en.wikipedia.org/wiki/Relay
electromechanical-relay.gif
 
Du sprichst Deutsch? :)
Danke für die schnelle Antwort. Ich werd sie morgen aufmachen und schauen ob ich dieses relais entdecke.
Zum Sichergehen.. du meinst ich sollte von vor der graetz-brücke bis nach der Lampe eine Überbrückung(draht) befestigen.
Bestell mir morgen gleich Lötausrüstung(löten an sich kann ich) und 2 dieser schwingspulen für den hochtöner. Hoffe schwer das sich die Boxen so reparieren oder wie du sagtest sogar noch klanglich verbessern lassen. (If you dont speak german I'll write this text on english again.)
 
I've just putted the tweeter that scratches into the other speaker and there it works proberly. No scratching sound.
 
Now I putted it back to where it was before and until now I've played Gunsnroses yesterday with axels high pitch voice on high volume and not the slightest scratchy sound was there. I dont know if it is solved now because when the problem lately first appeared it also had times in which I could listen for like 10-20 seconds. But I am now listening since 15 minutes and all is well. Could it be that the problem was that the contacts where just bad soldered and now since I soldered them again their good?
 
I've just measured it. I play with 93 db in 1m distance and the high pitch voice has peaks araund 109 db. And still its playing good.
 
Khaefeli said:
Du sprichst Deutsch? :)
Danke für die schnelle Antwort. Ich werd sie morgen aufmachen und schauen ob ich dieses relais entdecke.
Zum Sichergehen.. du meinst ich sollte von vor der graetz-brücke bis nach der Lampe eine Überbrückung(draht) befestigen.
Bestell mir morgen gleich Lötausrüstung(löten an sich kann ich) und 2 dieser schwingspulen für den hochtöner. Hoffe schwer das sich die Boxen so reparieren oder wie du sagtest sogar noch klanglich verbessern lassen. (If you dont speak german I'll write this text on english again.)
Click to expand...
Sorry, but my German is rather weak. I'm reading in German but speaking/writing is more difficult. I'd prefert to stay by english, also in view of readability for other members.
With regards the problem, it seems it could be the some weak contact, cold solder, bad capacitor, or eventually problem with protection unit.
I would eventually advise to reverse tweeters between boxes once again and listen long enough to make sure the "scratching" tweeter is not starting to scratch in the "good box" after longer listening time. Let's say one or two days.
Or if problem would be caused one of above mentioned reasons, then "good" tweeter in "scratching box" should start to do the same scratching sound.
 
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Ok so If the problem is the crossover, I'm thinking about putting out all the switches, because that would make a less amount of contacts and possible failurepoints.
 
If I would do that, would it work like shown in the picture? I washed out the things I would cut out of the circouit and I've marked the new connections that I would make. Screenshot (13).png
 
Khaefeli said:
Ok so If the problem is the crossover, I'm thinking about putting out all the switches, because that would make a less amount of contacts and possible failurepoints.
Click to expand...
you should find out what is causing the "tweeter's scratching" problem anyway...
Khaefeli said:
If I would do that, would it work like shown in the picture? I washed out the things I would cut out of the circouit and I've marked the new connections that I would make. View attachment 689945
Click to expand...
Your should decide what is your prefered placing of the Deltas and choose the of the Environment Switch, 1/4space (wall/ground) or 1/2space (ground) accordingly.
If you decided 1/4 is the best, adapted scheme on your picture is generally OK.
I only don't understand why you have drew the resistor near "0dB".
If you like and want to keep "0dB" tweeter's level, you need to bypas it directly on the crossover. In other words, tweeter's signal need to go from Input+/Biamp+ terminals directly to the 1,5uF capacitor.

Howeever if you would like to use 1/2space (=stand alone, ground position of the speaker at least 1 meter from any wall) you need to follow 1/2space scheme (switches by VMR and tweeter to be in oposite positions.

As I have quite big listening room (cca 40m2) I've placed my Deltas as standalone. So I'm using 1/2space position.
Based on long long listening tests and later fine tuning of L-pads, I prefer this position.
In my room and to my ear it sounds much much better than placing them 10cm near back wall while using 1/4space scheme.
There is significantly better holographic, 3D scene with such 1/2space, standalone setup.
But I understand there are fans of the wall placing too.
 
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Thanks for looking at my crossover plan and explaining me what to do. I will use 1/4 position since i have quite a small room. Im going to do this tomorow/today and then i'll see if it works.
Again lots of thanks to you and peter for helping me with my deltas.
 
I just read a bit about crossovers electronics and finally got to a sheme that i believe should actually work.Screenshot (1)).png I guess the previous ones were pretty unusable.
 
I now did the changes and it worked proberly. But after 10minutes of listening it scratches back again. Does anybody know what it could be. Me my self thought it could be caused by the fact that one contect of the vmr 6 wasnt soltered, so i did that. It scratches less but as before sometimes the amplifier makes a clipping sound and turns down volume. Do you know what could be the problem?
 
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