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Hello,
Sorry if this question has been answered previously. ?I just finished a replacement of cap on the DQ-10 crossover. ?While measuring the crossover, ?I notice that the Tweeter and STweeter adjustment potentiometer changes the voltage to the tweeter and Stweeter in only three position. ?The positions where the voltage to the tweeter and Stweeter changes are fully minus, fully positive, and any in between position. ?It is not variable as expected and acts almost like 3 position switch. ?It is the same on both speakers. ?Is this what was intended in this crossover design? ?Has anyone experienced the same?
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You may
what to try measuring the potentiometer resistance with it out of the circuit to
verify that it is functioning correctly.
Rich
On Sunday, November 13, 2022 at 08:27:56 AM CST, Ed Marrs <ed.marrs123@...> wrote:
Hello,
Sorry if this question has been answered previously. ?I just finished a replacement of cap on the DQ-10 crossover. ?While measuring the crossover, ?I notice that the Tweeter and STweeter adjustment potentiometer changes the voltage to the tweeter and Stweeter in only three position. ?The positions where the voltage to the tweeter and Stweeter changes are fully minus, fully positive, and any in between position. ?It is not variable as expected and acts almost like 3 position switch. ?It is the same on both speakers. ?Is this what was intended in this crossover design? ?Has anyone experienced the same?
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That is definitely odd. Do desolder and check the readings again. Usually you would start off setting them to 12 o'clock. And the tweets should be darn close to each other and responsive to slight adjustments either positive or negative. From there I've never had to venture beyond 11 or 1 o'clock on either side. In fact you will find that for optimal results they require slightly different settings for digital or analog playback. Usually they do a bit better running a tad hotter on analog materials.?
DD
You may
what to try measuring the potentiometer resistance with it out of the circuit to
verify that it is functioning correctly.
Rich
On Sunday, November 13, 2022 at 08:27:56 AM CST, Ed Marrs < ed.marrs123@...> wrote:
Hello,
Sorry if this question has been answered previously.? I just finished a replacement of cap on the DQ-10 crossover.? While measuring the crossover, ?I notice that the Tweeter and STweeter adjustment potentiometer changes the voltage to the tweeter and Stweeter in only three position.? The positions where the voltage to the tweeter and Stweeter changes are fully minus, fully positive, and any in between position.? It is not variable as expected and acts almost like 3 position switch.? It is the same on both speakers.? Is this what was intended in this crossover design?? Has anyone experienced the same?
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Sounds a bit like the movable part of the pot, center terminal called the wiper, is only making contact near the ends the rotation.
You should try rotating the pot repeatedly over its full range. This may restore operation but probably only temporarily.
this can be verified with a resistance test between the two outer terminals (about 25 ohms)and each of the outer terminals and the center terminal. In the second test the resistance should be near zero when the knob is at one end and 25 at the other end and should vary smoothly as you turn the knob.?
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I believe I did measure resistance and nothing look out the ordinary. ?I think I’ll check once more. ?I am currently measuring SPL measurements and I do see a variable change in the frequency response, with potentiometer changes. ?It’s usual that I didn’t see a variable voltage change. ?Only what appears to be discrete -, +, and in between voltage across the tweeter and Stweeter.. ?This speakers appears very bright and I may run them with potentiometer turned all the way down. ?Our perhaps a bit of EQ.?
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Here are the measurement before and after changing the capacitors.? No real difference other than the repair of the shorted cap and coil found in the right speaker.? The shaded region on the left speaker shows the cross-over response of the tweeter and stweeter at the two potentiometer extremes + and -, and the middle line in between represents any position other than + or -. However, after my SPL measurement, I am now unsure of my original voltage measurements across the tweeter and stweeter for variable potentiometer positions.??
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Hi,
I can't here any diffrent in sound when adjusting the control...something wrong?.?
Best regards? Jonas
Here are the measurement before and after changing the capacitors.? No real difference other than the repair of the shorted cap and coil found in the right speaker.? The shaded region on the left speaker shows the cross-over response of the tweeter and stweeter at the two potentiometer extremes + and -, and the middle line in between represents any position other than + or -. However, after my SPL measurement, I am now unsure of my original voltage measurements across the tweeter and stweeter for variable potentiometer positions.??
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Jonas sondell
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It wasn’t until I decided replace the crossover capacitors, that I found a shorted capacitor and coil.? This rendered my tweeter, Stweeter and adjustment useless.? Check for the burn marks on the board under R3.? It was difficult for me to hear if the tweeter, let alone the Stweeter was working properly.? My hearing appears to cut off just above 12 KHz.
Hi,
I can't here any diffrent in sound when adjusting the control...something wrong?.?
Best regards? Jonas
Here are the measurement before and after changing the capacitors.? No real difference other than the repair of the shorted cap and coil found in the right speaker.? The shaded region on the left speaker shows the cross-over response of the tweeter and stweeter at the two potentiometer extremes + and -, and the middle line in between represents any position other than + or -. However, after my SPL measurement, I am now unsure of my original voltage measurements across the tweeter and stweeter for variable potentiometer positions.??
--
Jonas sondell
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Not deoxit or bad potentiometers Bill Meyerhoff?
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On Nov 13, 2022, at 20:20, Samuel Crider <dieseldude1@...> wrote:
? That is definitely odd. Do desolder and check the readings again. Usually you would start off setting them to 12 o'clock. And the tweets should be darn close to each other and responsive to slight adjustments either positive or negative. From there I've never had to venture beyond 11 or 1 o'clock on either side. In fact you will find that for optimal results they require slightly different settings for digital or analog playback. Usually they do a bit better running a tad hotter on analog materials.?
DD
You may
what to try measuring the potentiometer resistance with it out of the circuit to
verify that it is functioning correctly.
Rich
On Sunday, November 13, 2022 at 08:27:56 AM CST, Ed Marrs < ed.marrs123@...> wrote:
Hello,
Sorry if this question has been answered previously.? I just finished a replacement of cap on the DQ-10 crossover.? While measuring the crossover, ?I notice that the Tweeter and STweeter adjustment potentiometer changes the voltage to the tweeter and Stweeter in only three position.? The positions where the voltage to the tweeter and Stweeter changes are fully minus, fully positive, and any in between position.? It is not variable as expected and acts almost like 3 position switch.? It is the same on both speakers.? Is this what was intended in this crossover design?? Has anyone experienced the same?
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Ed, If the voltage plots you sent are correct it appears that C3 was shorted and the pot only connected when it was at the extremes of its rotation. This can happen due to the way the pot is made. C6 also COULD have been open. It seems very likely the pot is bad. if you have a couple of 12 ohm resistors you could wire them like this to substitute in for the pot. See the pic below for details. Normally you would set the pot, measure resistances, ?then substitute. In the case the pot is not working so just use 12 ohms for both resistors. This will simulate a centered pot.
I don't know how you made these measurements of of driver voltage, perhaps you can elaborate.
Also because of the network architecture, unless you are very experienced it is hard to measure some of the components in circuit. You have to unsolder at least one lead, two on the pot, to make more reliable measurements.
My career for 32 years was teaching folks how to make measurements correctly. It can be very tricky. There are lots of common mistakes.
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Charlie, I’m going to see if I can remeasure the affect of the potentiometer on the tweeter an stweeter, this weekend.? The response curves of each speaker were taken using a true RMS DVM, with all speakers connected to the crossover.? First measuring the input RMS voltage to the speaker (Vin), then measuring the RMS voltage across the individual + - speaker terminals (Vs).? Then plotted 20?log (Vs / Vin).?
On Tue, Nov 15, 2022 at 5:44 PM Charlie Conger < ctconger@...> wrote: Ed, If the voltage plots you sent are correct it appears that C3 was shorted and the pot only connected when it was at the extremes of its rotation. This can happen due to the way the pot is made. C6 also COULD have been open. It seems very likely the pot is bad. if you have a couple of 12 ohm resistors you could wire them like this to substitute in for the pot. See the pic below for details. Normally you would set the pot, measure resistances, ?then substitute. In the case the pot is not working so just use 12 ohms for both resistors. This will simulate a centered pot.
I don't know how you made these measurements of of driver voltage, perhaps you can elaborate.
Also because of the network architecture, unless you are very experienced it is hard to measure some of the components in circuit. You have to unsolder at least one lead, two on the pot, to make more reliable measurements.
My career for 32 years was teaching folks how to make measurements correctly. It can be very tricky. There are lots of common mistakes.
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Charlie, Thanks for the modification information.? It appears that I have an issue with the potentiometers in the pair of DQ-10 that I recently recapped and repaired.? Attached are the measured SPL frequency responses of the pair that I am having the issue with (ROC) and a different pair of DQ-10 (NL).? The discrete high end changes (fully CW, fully CW, and anywhere in the middle) of the problem pair, confirms what I was seeing with the voltage measurements.? I'll have dig in further.? Perhaps with the modification you described.
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I should have mentioned the measurements were made with the tweeter potentiometer at 7 o’clock (fully CCW -), 9 o’clock, 12 o’clock, 3 o’clock and 5 o’clock (fully CW +) positions.
Charlie, Thanks for the modification information.? It appears that I have an issue with the potentiometers in the pair of DQ-10 that I recently recapped and repaired.? Attached are the measured SPL frequency responses of the pair that I am having the issue with (ROC) and a different pair of DQ-10 (NL).? The discrete high end changes (fully CW, fully CW, and anywhere in the middle) of the problem pair, confirms what I was seeing with the voltage measurements.? I'll have dig in further.? Perhaps with the modification you described.
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Looks like I'll be replacing the two potentiometers.
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Boy that speaker has lived a hard life! Charlie Conger 713 472 9140
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On Nov 19, 2022, at 6:49 PM, Ed Marrs <ed.marrs123@...> wrote:
?Looks like I'll be replacing the two potentiometers.
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It seems so.? Thanks you so much for your advise and encouragement on this project.
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Ed, better to replace the pot with fixed resistors once you determine the correct level. This is best done with measurements but pink noise, adjusted to sound the same on left and right channels, is also a good alternative. The latter does require trial and error and learning what pink noise should sound like.
The ACOUSTIC measurements you show above have too much high frequency for most listeners. You want the response to be FLAT but only on the tweeter axis at 1 M from the speaker. It is important to take this in a precise way, that is within 1/2" of identical mic and speaker positioning. ?At the typical listening position this will translate into about 5dB down at 15khz due to in room power response (the total energy radiated into the room vs on axis)?
The fixed resistors will both sound better and more importantly be stable. The variable pots are subject to wear and degradation. See post 6307 for a method to do this. Based on you ACOUSTIC measurements, the only ones that matter due to driver variations, the midrange to lower pot settings on the functioning speaker are the ones to shoot for. Using pink noise is a VERY SENSITIVE test, far more sensitive than music. The correct way to do this is to have helper adjust the pot while you listen what you are shooting for is the smoothest sound with no sudden "peaks" in the noise character. With a little practice this will produce a level accurate to about .5 dB which is excellent. If you have a real time spectrum analyzer function of your software AND you use (1/3) octave based measurements you can use this to calibrate your ears to hear these fine changes.
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Charlie Conger
jonas Ehnstr?m
Bill Meyerhoff
