Blue Shadow
Waiting for Vintage Gear from this century
Those two 4Ω 15W resistors in my DQ-10s got kinda hot today. Yes, I was playing them loud. Any issues I need to look at?
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Are the two resistors in series with the woofer supposed to get really hot?
- Thread starter Blue Shadow
- Start date
Those two 4Ω 15W resistors in my DQ-10s got kinda hot today. Yes, I was playing them loud. Any issues I need to look at?
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RTally
Speaker addict
Assuming that the woofer is a nominal 8 ohms, then one-half the power going through your woofer goes through those two series resistors. That means your speaker should have a maximum rating of 30 watts to stay within the resistor specs. That would be 30 watts of continuous power, peaks can be higher.
This is one of the reasons that a well-designed crossover has air space around the resistors. The air space allows the heat to dissipate. Alternatively, a designer could use over-rated resistors and not worry about heat degradation of the resistors.
As long as there is enough air space to dissipate the heat generated from the resistors, I would not worry about it. If the resistors look discolored, they may have gotten too hot and should be replaced.
Generally, I would think that if you are overheating resistors, you run the chance of overheating the voice coil.
This is one of the reasons that a well-designed crossover has air space around the resistors. The air space allows the heat to dissipate. Alternatively, a designer could use over-rated resistors and not worry about heat degradation of the resistors.
As long as there is enough air space to dissipate the heat generated from the resistors, I would not worry about it. If the resistors look discolored, they may have gotten too hot and should be replaced.
Generally, I would think that if you are overheating resistors, you run the chance of overheating the voice coil.
RTally
Speaker addict
Also, how hot is hot? Most resistors are rated at 70 degrees C in free air. A trick I learned in the field is that if you can touch it momentarily without getting a blister, but you do not not to touch it longer than a moment, you are at around 60 degrees C or less. But it is better to measure it with a thermometer.
Blue Shadow
Waiting for Vintage Gear from this century
300°F is hot. Smell of melted wax that coated these crossovers when new but was removed when they were recapped is what alerted me to the issue, listening from the other room. I've played this loud for long sessions before. Swapped out the hottest one and listening again a little lower volume and will keep an eye on these two and get the other one on the bench for a quick look see.
Might need to get some 20 watters and mount them off the board or just glue a damn computer heat sink to them.
Might need to get some 20 watters and mount them off the board or just glue a damn computer heat sink to them.
Bill Ferris
Lunatic Member
Also it might not be a bad idea to make sure that the speaker`s main fuse, is in fact, a 3 amp fast blow, if not already been confirmed.
Both of my sets of DQ -10`s 80 mfd. electrolytic caps rubber end seals were dried out and cracking, probably from living next to those warm ~ hot running resistors of the years, so if not already addressed, should be, no matter which "popular type`s" are chosen to replace, IMHO/E.
Both of my sets of DQ -10`s 80 mfd. electrolytic caps rubber end seals were dried out and cracking, probably from living next to those warm ~ hot running resistors of the years, so if not already addressed, should be, no matter which "popular type`s" are chosen to replace, IMHO/E.
It is a 5-way speaker!
sax6
Loudness always ON
Ahhh ! OK.
Freddymac2
Super Member
For many years i drove my DQ 10's with 200 watt Dyna and Ampzilla amps, at high levels. It never occurred to me to look at the condition of the crossover components. After 30 + years of hard use, many of the original cheap Mexican caps were totally toasted. i don't think anything is wrong with your speakers or crossovers.
maxhifi
Addicted Member
I wouldn't worry about it one bit. Resistors have a job of converting electrical energy into heat, and it sounds to me like that's exactly what they're doing. Here's a curve of temperature rise versus power, for YAEGO ceramic resistors. Keep in mind that a 15W soldering iron gets hot enough to melt solder! 300F is only 150C, which means if you have an ambient temperature of say 25C, your temperature rise is only 125C - that's well within the limits for a 15W ceramic resistor, and corresponds to a conservatively specified resistor. In other words, it ain't broke, so don't fix it.
I wrote on PE Tech Talk:
" Normally a cap would be used across the woofer in a series XO but
they must have, well actually I don't know what they were thinking with a resistor there."
I was going to say they must have used what worked to get the required response.
fdieck wrote, LOL:
"I think they were thinking " I hope this damned thing doesn't catch on fire."
From here:
http://techtalk.parts-express.com/forum/tech-talk-forum/67019-clone-unknown
" Normally a cap would be used across the woofer in a series XO but
they must have, well actually I don't know what they were thinking with a resistor there."
I was going to say they must have used what worked to get the required response.
fdieck wrote, LOL:
"I think they were thinking " I hope this damned thing doesn't catch on fire."
From here:
http://techtalk.parts-express.com/forum/tech-talk-forum/67019-clone-unknown
ConradH
Lunatic Member
Since the resistors are in parallel with the woofer (they see the same voltage), and are of about the same impedance, how hot do you suppose the voice coil is getting? There are reasons they might not get as hot, but I'd be wondering if your drive level isn't a bit too aggressive.
Most people who've owned DQ10's state that each time they upped the power,
for example from 40 to 100W, then to 200W they sounded better and better. I've
always found that the extra headroom really helps with most speakers that can
take it.
I picked up a pair of really nice DQ10s recently and plan to double the power
rating of several of the resistors including the subject ones of this thread.
There are pictures of DQ10 rebuilds where the XO board is burnt under the
resistors, they should be elevated since by design they get HOT.
for example from 40 to 100W, then to 200W they sounded better and better. I've
always found that the extra headroom really helps with most speakers that can
take it.
I picked up a pair of really nice DQ10s recently and plan to double the power
rating of several of the resistors including the subject ones of this thread.
There are pictures of DQ10 rebuilds where the XO board is burnt under the
resistors, they should be elevated since by design they get HOT.
Blue Shadow
Waiting for Vintage Gear from this century
I recall some charred boards from DQ-10s but don't recall which caps showed the issues.
These crossovers have been recapped since they were either original lytics throughout (except the 0.1 and 0.15 caps for the tweeter). I'll be looking at this crossover to verify things.
I have driven these hard with ss power, 100 wpc, 185 wpc and 150 wpc and it was this last one that made me notice the heat. I expect the others have done that, too but maybe not driven for as long/as loud. I blame part of that on the electronic music Tom sent me.
As to the power needed to drive these speakers, I will say it again, all three ss amps are not even close to the sound of the 50 tube amps. The guys always say these sound so much better. So easy to swap, I use the tubes to listen in the sound room and the ss amps to listen around the house. I don't need the tubes to play music when I'm washing dishes. The guys say the ss amps sound like a nice stereo playing and the tube amps sound like there is music in the room. "Now that is what it is supposed to sound like" was one comment made following the swtich. Another, first time visitor, mentioned that hearing the tube amps was the highlight of his listening session as did one other who mentioned the DQ-10s were a walk down memory lane, a great speaker, but he had moved one, but knew the tubes were the right juice to drive em based on how they sound.
If the woofer voice coils are getting that hot, I guess I'm glad they are similar to the Advent woofer and replacements are easily found.
Maybe time for some relocation of the resistors to prevent issues.
These crossovers have been recapped since they were either original lytics throughout (except the 0.1 and 0.15 caps for the tweeter). I'll be looking at this crossover to verify things.
I have driven these hard with ss power, 100 wpc, 185 wpc and 150 wpc and it was this last one that made me notice the heat. I expect the others have done that, too but maybe not driven for as long/as loud. I blame part of that on the electronic music Tom sent me.
As to the power needed to drive these speakers, I will say it again, all three ss amps are not even close to the sound of the 50 tube amps. The guys always say these sound so much better. So easy to swap, I use the tubes to listen in the sound room and the ss amps to listen around the house. I don't need the tubes to play music when I'm washing dishes. The guys say the ss amps sound like a nice stereo playing and the tube amps sound like there is music in the room. "Now that is what it is supposed to sound like" was one comment made following the swtich. Another, first time visitor, mentioned that hearing the tube amps was the highlight of his listening session as did one other who mentioned the DQ-10s were a walk down memory lane, a great speaker, but he had moved one, but knew the tubes were the right juice to drive em based on how they sound.
If the woofer voice coils are getting that hot, I guess I'm glad they are similar to the Advent woofer and replacements are easily found.
Maybe time for some relocation of the resistors to prevent issues.
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