moray james Posted February 25, 2021 Share Posted February 25, 2021 The symbol for a PPTC (AKA Resettable Fuse) is: This poly switch is there to protect the tweeter from heavy hands on the volume control by partially deaf people. The parallel resistor insures that there is always 100 ohms in series with the tweeter (I think, for those who design xovers feel free to correct me, thanks). Quote Link to comment Share on other sites More sharing options...
OO1 Posted February 25, 2021 Share Posted February 25, 2021 2 hours ago, Marvel said: The long midrange horn is actually getting the driver in a closer position for time alignment with the woofer. the mouth of the horn seems quite longer than a K400 Quote Link to comment Share on other sites More sharing options...
mboxler Posted February 25, 2021 Share Posted February 25, 2021 21 minutes ago, moray james said: The symbol for a PPTC (AKA Resettable Fuse) is: This poly switch is there to protect the tweeter from heavy hands on the volume control by partially deaf people. The parallel resistor insures that there is always 100 ohms in series with the tweeter (I think, for those who design xovers feel free to correct me, thanks). I believe you meant to say "at most" 100 ohms in line with the tweeter. When low current is passing through the circuit, the switch is low resistance (0 ohms?), and all the current is flowing through the switch and tweeter. 0 ohms in parallel with 100 ohms is 0 ohms. If too much current is flowing through the switch, it's resistance increases, and current begins to flow through the resistor as well. This continues until the switch can cool. Until then, there is a voltage drop across the switch//resistor, and therefore less voltage across the tweeter. Quote Link to comment Share on other sites More sharing options...
henry4841 Posted February 25, 2021 Share Posted February 25, 2021 49 minutes ago, moray james said: The symbol for a PPTC (AKA Resettable Fuse) is: This poly switch is there to protect the tweeter from heavy hands on the volume control by partially deaf people. The parallel resistor insures that there is always 100 ohms in series with the tweeter (I think, for those who design xovers feel free to correct me, thanks). Learn something every day. I just googled RDE 50 and came up with a ceramic capacitor that Mouser and Digikey sells. If that is the case then the circuit should be just a protection circuit which does make sense. No help for OP. Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted February 25, 2021 Author Share Posted February 25, 2021 27 minutes ago, RandyH000 said: the mouth of the horn seems quite longer than a K400 No, it is the same size as the k401 Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted February 25, 2021 Author Share Posted February 25, 2021 RDE 050 is a polyswitch, in french a varistance Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 25, 2021 Share Posted February 25, 2021 18 minutes ago, RandyH000 said: the mouth of the horn seems quite longer than a K400 The depth of an FH-1 is about the same as a La Scala, and a K-400 reaches the back of the cabinet the same as the wood copies. It really should be further back to be in alignment. Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted February 25, 2021 Author Share Posted February 25, 2021 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted February 25, 2021 Share Posted February 25, 2021 Just came to me. Not as quick thinking as I use to be. If the polyswitch is bad, open it would be the problem of low highs since all the sound would be going through the 100ohm resistor and also changing the crossover frequency. Easy to check with ohmmeter or even just jump across the polyswitch with a jumper wire. Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted February 25, 2021 Author Share Posted February 25, 2021 yes you are right, yesterday i measured it .. the polyswitch is ok, i have less than 0,5 Ohms for the 100 Ohms in // with the polyswitch Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted February 25, 2021 Author Share Posted February 25, 2021 i am thinking that perhaps is the Atlas sound PD-5VH not the good driver for the La Scala with the AL-3 crossover. On the crossover diagram, i see that the squawker has no highpass filter, so it plays until his own response curve, something like 3 kHz .. The tweeter begin to work over 4500 Hz i think ... so it give a hole from a little more than 3 kHz to 4,5 kHz .. isn't it ? Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted February 25, 2021 Author Share Posted February 25, 2021 i should search a k-55m driver, perhaps it goes higher than the Atlas sound Quote Link to comment Share on other sites More sharing options...
henry4841 Posted February 25, 2021 Share Posted February 25, 2021 24 minutes ago, SpeedLimit said: yes you are right, yesterday i measured it .. the polyswitch is ok, i have less than 0,5 Ohms for the 100 Ohms in // with the polyswitch Short across it anyway. Could be when a signal reaches it that it opens too early. Never know. Quote Link to comment Share on other sites More sharing options...
Hemihorn Posted April 25, 2021 Share Posted April 25, 2021 best crossover suggest get miniDSP HD and umic one download eq wizard free.keep autoformer to impedance match and put capacitor on tweeter for protection 6db slope. Then you can experiment as much as you want with crossover with an infinite combination.you can also level match and time align all drivers.Then if you want to build a passive network you have a starting point and know what you like. Quote Link to comment Share on other sites More sharing options...
geoff. Posted April 25, 2021 Share Posted April 25, 2021 You can confidently remove the polyswitch from the crossover. It is only “needed” if you use K-77s, kind of like Zeners in an AA. You might bypass them and eliminate that variable. Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted April 25, 2021 Author Share Posted April 25, 2021 in the meantime i have built a type a filter and it works much better. I think it is because i use Atlas sound pd-5vh drivers and not the electrovoice k55 m drivers Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted April 25, 2021 Author Share Posted April 25, 2021 Perhaps thé al-3 works better with the EV drivers but i didn't find any Quote Link to comment Share on other sites More sharing options...
babadono Posted April 25, 2021 Share Posted April 25, 2021 On 1/17/2021 at 4:56 AM, SpeedLimit said: Vous parlez français ? En fait, je viens de commander les 2, les DE10 et les DE120 en 8 ohms ainsi qu'une paire de diaphragme de10 en 16 ohms au cas où j'en ai un autre usage. Je testerai les 2 tweeters. C'est vrai que le DE10 sont beaucoup moins chers .. Merci en tout cas pour tous les renseignements. Je m'étais trompé pour les boomers, j'avais acheté les Kappa 15A en 8 ohms, je ferai un autre usage de ces haut-parleurs. Il me reste à trouver une paire de K-401, car j'en ai fabriqué en bois mais je préférerais avoir les originaux qui seront bien mieux que mes copies en bois. Merci encore RandyH000 et bon dimanche, le mien se termine bientôt .. This is America---speak Spanish!! Quote Link to comment Share on other sites More sharing options...
SpeedLimit Posted April 26, 2021 Author Share Posted April 26, 2021 6 hours ago, babadono said: This is America---speak Spanish!! I was just making an answer to RandyH000. What is wrong for you or with you ? Are you so much against people who is not from your country ? I only was a little happy to change some words with Randyh000. Have a good beginning of the week Quote Link to comment Share on other sites More sharing options...
babadono Posted April 26, 2021 Share Posted April 26, 2021 Quote Link to comment Share on other sites More sharing options...
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