Croc Posted March 19, 2011 Share Posted March 19, 2011 Got 511 horns for my La Scalas - and although i love midrange timbre and clarity and increase in details - they create a new problem. But first few words about the setup: - ~1977 La Scalas which AA xover was modified to A by removing diodes and second coil. Caps were refreshed few years ago by Bob's oil caps. - tweeters i use are JBL 2404 - small braces on bass bins so what's the problem? the midbass became slow and wooly - the fast and snappy character of La Scalas has been lost. i'm thinking to try attennuate squawker. saw this thread with instructions: http://forums.klipsch.com/forums/t/135666.aspx any additional ideas? because imrovements it brought i really like - if i just could solve this midbass issue.... Thx, Gennady Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 19, 2011 Share Posted March 19, 2011 I would change the crossover frequency to 500hz and let the bass bin take over the upper mid bass mission.......and after makeing the change....then decide if you need a mid horn level adjustment. use a swamping resistor if your going to change the mid horn tap setting. Quote Link to comment Share on other sites More sharing options...
Croc Posted March 20, 2011 Author Share Posted March 20, 2011 make sense. what to mod to raise xover point to 500hz? another one - for mid attenuation Al says to use 16 ohm resistor across the output to the mid driver, and dropping to tap #3 : so it needs to be 12 watt or more? Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 20, 2011 Share Posted March 20, 2011 Using a 16 ohm resistor would probally be OK for Heresy or Cornwalls, but not for LaScala's. the 16 ohm resister changes the crossover frequency to high. For general approximates, you have two choices, one with no soldering which is good just to get a feel of what the sound will be like, the other with soldering to implement the final solution. To change the crossover frequency to 500hz, you need a 9.9uf capacitor to replace the 13uf capacitor. You can test what this will sound like by temporarily a 5 watt 110 ohm resistor across the mid driver terminals. The 110 ohm resistor changes the calculations in a way that results in the 13uf cap being OK for 500hz. These are approximates...you or I do not have the proper tools to do exacting work. Quote Link to comment Share on other sites More sharing options...
Croc Posted March 20, 2011 Author Share Posted March 20, 2011 just to clarify - this is type A network, right? that new 9.9uf capacitor - what type/viltage should it be? Thx, Gennady Quote Link to comment Share on other sites More sharing options...
Croc Posted March 20, 2011 Author Share Posted March 20, 2011 Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 20, 2011 Share Posted March 20, 2011 It says "type a" right on the schematic......doesn't change the fact that if you add a 16 ohm resistor in between the auto-former and the driver your crossover frequency will rise to high. You need to use a parallel resistance program to first get the new resistance of the parallel combination for the driver+the new resister, then you run that new number into a crossover calculator. every time you change the load in between the auto former and the driver the crossover frequency will shift. If you use the 16 ohm resister, you will have a hole between 600hz and 800hz. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 20, 2011 Share Posted March 20, 2011 speakerfritz said: "Using a 16 ohm resistor would probally be OK for Heresy or Cornwalls, but not for LaScala's. the 16 ohm resister changes the crossover frequency to high." I am guessing that you did not notice the drawing showing the tap used going to tap 3? Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 20, 2011 Share Posted March 20, 2011 speakerfritz said: "Using a 16 ohm resistor would probally be OK for Heresy or Cornwalls, but not for LaScala's. the 16 ohm resister changes the crossover frequency to high." I am guessing that you did not notice the drawing showing the tap used going to tap 3? I saw that. Not going to feed into confusion. If you we move to tap 3, net impedance change would be zero. Net crossover frequency change will also be zero. I'm trying to address the methods used to correct the crossover frequency to what the manufacture of the altec 511 recommends. choices are changes caps, change load. you can change the load to shit the crossover frequency....but if thats the approach...it would not make sense to change the load using resistors and then change it back using a tap setting change. the new frequency change will be zero. Important point...changing the level of the auto-former will not change the crossover frequency if you use the methods described at the link. The original issue was a loss of mid bass. reducing the level of the mid driver in the manner described at the link will not increase mid bass. It sounds like the OP ha pre-decided to do a level change and just wants encouragement....which I am not going to encourage with out first fixing the crossover frequency issues. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 20, 2011 Share Posted March 20, 2011 Impedance of the K-55 is about 11 ohms at 500hz. Combination of 16 ohm resistor and 11 ohm driver is 6.52 ohms. Effective impedance then when connected to tap 3 is 26 ohms. I will let you do the rest of the math. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 20, 2011 Share Posted March 20, 2011 Very nice....now we have 500hz and a -3db for the mid driver. Lets see if "the midbass became slow and wooly" problem gets fixed. Quote Link to comment Share on other sites More sharing options...
Croc Posted March 21, 2011 Author Share Posted March 21, 2011 so what's the verdict? mit attenuation or xover point move? resistor or cap? what wattage/voltage shoud it be? Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 21, 2011 Share Posted March 21, 2011 so what's the verdict? mit attenuation or xover point move? resistor or cap? what wattage/voltage shoud it be? we were waiting for your report....the resistor seems the easiest...if you're OK with a -3db cut along with the crossover point change. Quote Link to comment Share on other sites More sharing options...
Croc Posted March 21, 2011 Author Share Posted March 21, 2011 i see. what wattage/voltage shoud resistor and cap be? Quote Link to comment Share on other sites More sharing options...
Croc Posted May 11, 2011 Author Share Posted May 11, 2011 an update - abvout a month ago i installed Bob's midrange gaskets and it tamed the mid bass problem. apperantly the opening of the gasket is smaller than k55 throat - so it's probably a must item to use as it affects sound a lot. anyway - it looks like i really missing something - 511 horn doesn't get down to 400 Hz as k400 does - so probably i'm having a 100 Hz "whole" (thx to speakerfritz for pointing this out). and indeed it sounds now like not enoough energy in the mid bass (i hope it's not psychological []). i don't understand in xovers - so pls tell me is it possible to raise woofer to 500Hz? or maybe it's just better to go for "drop in" solution such as Dave's Fastrac horn? Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 11, 2011 Share Posted May 11, 2011 anyway - it looks like i really missing something - 511 horn doesn't get down to 400 Hz as k400 does - so probably i'm having a 100 Hz "whole" (thx to speakerfritz for pointing this out). remember , you came into the picture already in the middle of a 511 install.....we don't know what problem you were trying to solve? Quote Link to comment Share on other sites More sharing options...
Croc Posted May 11, 2011 Author Share Posted May 11, 2011 what do you mean by that? the problem currently that it doesn't sound 100% right. since you enlightened me that 511 and K400 have different frew responce - i think this should be solved. how? sounds to me that moving xover point from 400 to 500 is required. but i'm not 100% sure as i'm not speaker design expert. so expirienced guys' input will be highly appreciated. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 11, 2011 Share Posted May 11, 2011 what do you mean by that? What were you looking to gain by moving to the 511? It's got to be more than getting it to behave like a k-400. What were you told that the 511 would do for you? When you first posted this project, you had already decided to install a 511. how? sounds to me that moving xover point from 400 to 500 is required. so you want to know what changes need to be made to your crossover to get a 500HZ xover point? let me see if I can go back and find which xover you have. Ok, if we assume to made the changes that Bob recomended which was to put in a resister and move the squawker to a lower tap, to complete that change, you would need to replace the 2.5mh inductor with a 1.27mh one. Thats what will raise the crossover point into your woofers. You can also just add a second 2.5mh inductor in parallel to the first, which will also result in 1.25mh. Quote Link to comment Share on other sites More sharing options...
Speakmeister Posted May 11, 2011 Share Posted May 11, 2011 Croc, did you know that the Belle and LaScala shared the same crossover for many years but had a different crossover frequency? The lower order slopes of the A or AA mean you are crossing over where the horn wants ( the electric crossover not the dominating factor, the acoustic crossover is). Quote Link to comment Share on other sites More sharing options...
Guest " " Posted May 11, 2011 Share Posted May 11, 2011 Croc, did you know that the Belle and LaScala shared the same crossover for many years but had a different crossover frequency? The lower order slopes of the A or AA mean you are crossing over where the horn wants ( the electric crossover not the dominating factor, the acoustic crossover is). absolutely correct. And in the later AB network, more was allowed to go into the woofer by totally eliminating the 2.5mh inductor that was in place during the AA days. Quote Link to comment Share on other sites More sharing options...
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