Hey, I was wondering if it's okay to run the 6x8 woofer into it's x-over, without the tweeter that comes with it, off of an amp.
I lost the tweeters for the set, after moving around a lot. Do you think it would blow the x-over or the amp? If it does damage it, do you think the fuse would blow on the x-over first?
Or, is it better to just run the woofer without the x-over at this point? I have another 5.25" component set, so the highs will be there, but I want the extra mids from the 6x8. :\
I lost the tweeters for the set, after moving around a lot. Do you think it would blow the x-over or the amp? If it does damage it, do you think the fuse would blow on the x-over first?
Or, is it better to just run the woofer without the x-over at this point? I have another 5.25" component set, so the highs will be there, but I want the extra mids from the 6x8. :\
If it's a 12dB/octave tweeter crossover, you need to load the tweeter connections. Radio Shack has 8 ohm 20 watt resistors that will work.
It would not hurt the 6x8 to run it direct.
It is best to use the XO from the set.. You can run the woofer direct but there may be some HF artifacts that are objectionable. Then again if they are in the rear and not the "main" set then the extended response of the 6x8 might be just right to compliment the fronts.
It is best to use the XO from the set.. You can run the woofer direct but there may be some HF artifacts that are objectionable. Then again if they are in the rear and not the "main" set then the extended response of the 6x8 might be just right to compliment the fronts.
If it is a basic parallel LP and HP filters why would you feel loading the HP is required? Series XO yes but parallel?
For a standard LC 12dB/octave crossover, when you remove the load, what you have is an LC circuit connected directly across the speaker output of the amp. At the crossover frequency, the LC circuit will be a direct short across the speaker terminals. This is covered on page 91 of the site.
I pulled a 12dB/octave 5k high-pass crossover from one of the tweeters on my bench and drove a 5v signal into it with a signal generator (no tweeter connected). The generator has a 50 ohm output impedance. At 100Hz, the voltage remained at 5v. At 5kHz, the voltage was dragged down to below 0.1v. At 20k, the voltage was allowed to rise again to about 2v. The same thing would happen with an amp but instead of dragging the voltage down at the speaker terminals, the amp would be loaded to a point of either failing or going into protect.
I pulled a 12dB/octave 5k high-pass crossover from one of the tweeters on my bench and drove a 5v signal into it with a signal generator (no tweeter connected). The generator has a 50 ohm output impedance. At 100Hz, the voltage remained at 5v. At 5kHz, the voltage was dragged down to below 0.1v. At 20k, the voltage was allowed to rise again to about 2v. The same thing would happen with an amp but instead of dragging the voltage down at the speaker terminals, the amp would be loaded to a point of either failing or going into protect.
System Crossover
Crossover Frequency 3200Hz @ 4
Crossover Slope 24dB/octave High-Pass 12dB/octave Low-Pass
Filter Q Butterworth
Tweeter Protection Optical Compression
here are the x-over specs. Supposedly each component is 4ohms, and after the x-over it is still 4 Ohms. I just measured the woofer and it's a little over 3Ohms, which should mean it's a 4 Ohm driver as stated.
However, I measured the tweeter from the other comp set, and it shows about 6.7 Ohms - so, would that mean it's an 8ohm tweeter? It's corresponding woofer read 4.3-4.7.
So, the x-overs are wired in such a way to make it 4 Ohms, in the end. Hum. Also they are rated at 100wRMS for the comp system. So, does that mean each speaker is about 50wRMS, and I should get a 50w resistor, @ 8 Ohms, or 4?
Hmm
Crossover Frequency 3200Hz @ 4
Crossover Slope 24dB/octave High-Pass 12dB/octave Low-Pass
Filter Q Butterworth
Tweeter Protection Optical Compression
here are the x-over specs. Supposedly each component is 4ohms, and after the x-over it is still 4 Ohms. I just measured the woofer and it's a little over 3Ohms, which should mean it's a 4 Ohm driver as stated.
However, I measured the tweeter from the other comp set, and it shows about 6.7 Ohms - so, would that mean it's an 8ohm tweeter? It's corresponding woofer read 4.3-4.7.
So, the x-overs are wired in such a way to make it 4 Ohms, in the end. Hum. Also they are rated at 100wRMS for the comp system. So, does that mean each speaker is about 50wRMS, and I should get a 50w resistor, @ 8 Ohms, or 4?
Hmm
Speaker impedance isn't constant across the entire audio band unless the crossovers are very complex.
The nominal impedance may be 4 ohms but the actual impedance at various points in the spectrum may be quite a bit higher.
For the tweeter load, as long as it's loaded with a relatively low value, you will be OK. The problem is when it's unloaded or very lightly loaded. It's unlikely that you will ever drive more than what the 8 ohm, 20 watt resistor can handle into the tweeter section of the crossover. If you use this, before closing up the panel where the crossover will be located, drive the system hard for a while to see how hot the resistor gets. If it's so hot that it could melt the surrounding material, do whatever is needed to protect from the hot resistor.
Another option would be to desolder the tweeter components in the crossover (or at least the capacitor that's in series with the inductor for the tweeter section).
The nominal impedance may be 4 ohms but the actual impedance at various points in the spectrum may be quite a bit higher.
For the tweeter load, as long as it's loaded with a relatively low value, you will be OK. The problem is when it's unloaded or very lightly loaded. It's unlikely that you will ever drive more than what the 8 ohm, 20 watt resistor can handle into the tweeter section of the crossover. If you use this, before closing up the panel where the crossover will be located, drive the system hard for a while to see how hot the resistor gets. If it's so hot that it could melt the surrounding material, do whatever is needed to protect from the hot resistor.
Another option would be to desolder the tweeter components in the crossover (or at least the capacitor that's in series with the inductor for the tweeter section).
Oh, I see.
To be clear though, if I am feeding it around 50w RMS, how come the 20w resistor is ideal? Is having headroom a problem? Getting a higher rated resistor, I mean.
Interesting though, =) Thanks for helping me through this
To be clear though, if I am feeding it around 50w RMS, how come the 20w resistor is ideal? Is having headroom a problem? Getting a higher rated resistor, I mean.
Interesting though, =) Thanks for helping me through this
IF (not likely) the audio content has a perfectly equal amount of content above and below the crossover point and you used a 50 watt amp, you'd have half of the 50w going to each section of the crossover. That would require a 25 watt resistor. The content in real music won't have nearly 50% above 3500Hz. Add to that audio isn't constant power, that reduces the power even more. The 25w isn't necessarily ideal but it should be sufficient. With audio, there are MANY variables and it's often difficult to say what's 'ideal'.
You can use a higher rated resistor. The RS resistor is generally readily available locally.
You can use a higher rated resistor. The RS resistor is generally readily available locally.
So what you are saying is that if a tweeter coil burns and you have an open HP circuit it will change the frequency response of the Mid / woofer? Or the output of the amplifier? Or will some how be detrimental to the amplifier?
The fact remains, if you have a two way XO with parallel filters zero, one or both of the filters can be used in any combination without "loading" the others and it will be safe on the amplifier. Adding a loading resister is not required and as you metioned could be a fire hazard. Also you didn't specify that the resistor should be a low inductance (preferably not wire wound) type.
Perry, you are the man on car amps no question there but on this one you might might be misinterpreting the OP.
Did you read page 91 of the car audio site and look at the graph? That graph was generated by LEAP. It was not drawn by me.
How could the test with the open crossover and the signal generator be mis-interpreted?
How could the test with the open crossover and the signal generator be mis-interpreted?
Well just as I was about to run to radioshack, I remember I had an old 3-way speaker in storage which had been terribly damaged on the woofer cone/surround, but as I remember the tweeters were okay. So, I removed the tweeters from the woofer, and also the little filter that they were wired to, since I planned on using them in the XO with the open spots.
But, I'm a little boggled. There is a tiny tweeter, and a large tweeter, and 3 wires come out of the little mounting device. Red, Black, and Green. I am getting 0 Ohms with the DMM on both sets (one from each 3-way). So I think maybe it's just a wiring issue. But I dont want to dig in until I know what I'm looking at. Any ideas?
But, I'm a little boggled. There is a tiny tweeter, and a large tweeter, and 3 wires come out of the little mounting device. Red, Black, and Green. I am getting 0 Ohms with the DMM on both sets (one from each 3-way). So I think maybe it's just a wiring issue. But I dont want to dig in until I know what I'm looking at. Any ideas?
It was a wiring issue, unfixable without opening up the mounting device. Unfortunately they were so old and brittle I popped the cone off of the larger tweeter. Nevertheless, Both smalls are great, and reading a healthy 4 Ohms, making this wiring job that much easier. Straight to the XO they go.
Thank you so much for your help Perry. *bows*
Thank you so much for your help Perry. *bows*
If it is a high pass you won't see any continuity through it with an Ohm meter. Resistance is measured with DC current and caps in HP filters block the DC current.
As Perry said, a picture is worth a thousand words.
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