Hello all !
So I've been fooling around with online crossover calculators and got wondering.... For say a two-way speaker it asks for the impedance of each driver in order to do the calculations. So my question is if I am adding resistors to each driver to make each one a 16 ohm load should I be entering in the original impedance (sans resistors) of each driver into the calculator or the impedance after adding resistors ? Values change so drastically when you add resistance to the mix !
So I've been fooling around with online crossover calculators and got wondering.... For say a two-way speaker it asks for the impedance of each driver in order to do the calculations. So my question is if I am adding resistors to each driver to make each one a 16 ohm load should I be entering in the original impedance (sans resistors) of each driver into the calculator or the impedance after adding resistors ? Values change so drastically when you add resistance to the mix !
A resistor dissipates energy, it doesn't convert it into acoustical energy- well, speakers are rather inefficient too !
However, the answer is a no-no.
The online calculators might be of some utility for high pass only, as woofers are rather unpredictable..
However, the answer is a no-no.
The online calculators might be of some utility for high pass only, as woofers are rather unpredictable..
I am actually looking to run a fullrange driver with a tweeter to top off the top end. So the tweeter is a 6 ohm. The impedance curve show by seas shows that it stays between 6-8 ohms in the frequency range I would be using it for. So I am looking at using it from about 10 kHz up. So I've put a 10 ohm resistor on it to make around 16 ohms. The fullrange is a 4 ohm with a 12 ohm on it.
I think you need to back up a notch or three. It sounds like you're trying to use resistors to make your drivers 16 ohms to match the output of a tube amplifier- this is not a good method. Crossovers are fairly complex, and the impedance in the passband isn't the only issue.
Can you be very specific about what you're using and how?
Can you be very specific about what you're using and how?
I am making both drivers 16 ohm to make an 8 ohm load when run in parallel. I am using just cap for the tweeter, It's not for my tube amp.
OK, are you also to be running these in parallel physically? Ie, will they be in the same cabinet, or beside each other or something else?
You don't put any resistor in line with a woofer- at least not more than 1-1.5Ω in some ( sealed enclosure ) case - and the capacitor decouples the tweeter
from the amplifier. Look at any design whatever it may be fullrange + tweeter
or woofer-mid-tw...the resistors in series alone play a different role.
from the amplifier. Look at any design whatever it may be fullrange + tweeter
or woofer-mid-tw...the resistors in series alone play a different role.
That is plain wrong. If you use a cap then you have a crossover, and the drivers are not seen as separate entities anymore. The impedance will be a combination the of drivers impedance and the crossover.
Adding a series resistor to a woofer is basically a no-no because you are wasting energy without a real benefit. If your amp cannot drive a 4 Ohm driver then change driver or amp. Mixing a 4 Ohm woofer to a 6 Ohm tweeter doesn't pose any problem.
Another problem I see is running the fullrange without a low pass filter. You'll have lobing problems in the treble.
Ralf
So what I am using is a Seas FU10RB 4 ohm fullrange with just an 12 ohm resistor run in parallel with a Seas 27TBCD DXT tweeter 6 ohm with a 10 ohm resistor and a capacitor. (I do have a pair of Seas FU10RB in 8 ohm available if needed). I am not worried about a lowpass filter as of yet as my amp will let me control it.I would just like to start with a simple first order crossover and expand along the way. I am looking to learn along the way and expand as a go. I do see many coaxial speakers with just a capacitor on the tweeter and they seem to work okay for what they are. The drivers I have are in a sealed box currently and I could modify to port them if needed. Basically what I am looking for is a 6 ohm load or higher as the amp says 6-8 ohms.
So should I lose the resistor on the woofer and put a higher value on the tweeter ?
That's not really how it works, drivers have an impedance curve that isn't flat. A woofer and a tweeter won't really sum together like two woofers would because the woofer's impedance will generally rise as frequency increases.
Here's an example:
That might be a better option.
Edit: Here's the plot for the 8 ohm version of your driver. The curve isn't as drastic for a full range type driver, but it's still there.
An externally hosted image should be here but it was not working when we last tested it.
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Why do you need 8 ohms, first? 2nd, the fullrangers have pretty good top end extension and a rising response, but a low sensitivity at 85dB. If you want to use a full size tweeter like the Dxt, you're better making a 2 way than a 1st order highpass on the tweeter and resistive attenuation. These may well be good candidates for a series crossover, which can sometimes allow for a design with fewer parts count for a simple XO.
Before getting into that, if you just want to get your feet wet, I suggest getting a variable 8 ohm l-pad and pairs of a few small capacitor values- .2uF, .5uF, 1uF, 2uF. This will give you a reasonable range for adjustment, and you can tweak the cap value by adding values in parallel. Use inexpensive film capacitors for this. The L-Pad will control both volume and add impedance compensation via the parallel value, so it'll be an easy thing to fiddle with.
Eventually you'll probably want to try a few inductors to suppress the top end of the fullranger and run your tweeter a little lower in frequency. A few values (again in pairs) ranging from .22mH, .5mH, 1mH would be sufficient for this, and you should use probably 16-18 awg aircores. The fullrange won't need impedance compensation because of the low-inductance coil.
That'll be enough to get you something workable with those drivers- once you have a feel for it and have tried a few crossovers, it's easier to understand the jargon and do a proper design, if you're gung-ho about getting your feet wet.
All of this presupposes you have the drivers already- if you don't, there are several very inexpensive kits, such as the Tritrix at parts express, that are a good and inexpensive way to start getting your feet wet with a guaranteed good result.
I do own all these drivers. (FU10RB 4 ohm and 8 ohm versions and the dxt tweeter.) I also have .75 mh and .92mh coils and 3.3uf and 8.4uf caps. I have a few 8,10,12 and 4 ohm resistors. I can and will order more x-over components as I experiment and adjust. I am trying to start really simple and experiment as I go. So what I am looking to do is come up with a 6-8 ohm average load and tinker with a caps and later coils as I progress. I did calculate that I would need about a 1.1uf cap and a .22mh with my current design.
The waveguide around the tweeter may allow for simpler crossover such the series cap.
Going higher order of course allows for higher power to be applied.
High value resistors ( > 10 Ω ) are used to flatten peak impedance when put in parallel to the driver. Low value ones are used to set equal output when the tweeter's too loud
and it's different if they are placed before or after the capacitor.
The waveguide gives an acoustical load to the very vicinity of the dome (or cone) and depending on its diameter and form it amplifies the very low end ( well- it doesn't let it decay ) of its band, so when filtering with a cap you simply shift the Fc higher and the acoustical result is still flat response; so, also 1-1.5-2.2 uF values are useful
Going higher order of course allows for higher power to be applied.
High value resistors ( > 10 Ω ) are used to flatten peak impedance when put in parallel to the driver. Low value ones are used to set equal output when the tweeter's too loud
and it's different if they are placed before or after the capacitor.
The waveguide gives an acoustical load to the very vicinity of the dome (or cone) and depending on its diameter and form it amplifies the very low end ( well- it doesn't let it decay ) of its band, so when filtering with a cap you simply shift the Fc higher and the acoustical result is still flat response; so, also 1-1.5-2.2 uF values are useful
When you put a resistor in series with a woofer it raises the top end and can cause peaking in the bass. Basically, where the driver impedance is smallest, these frequencies will be cut the most.
If your impedance dips a little below the amp rating it won't necessarily be a problem. A lot could be. If you use resistance it should probably be the smallest necessary.
You also don't need to make the two drivers the same impedance as each other.
If your impedance dips a little below the amp rating it won't necessarily be a problem. A lot could be. If you use resistance it should probably be the smallest necessary.
You also don't need to make the two drivers the same impedance as each other.
Okay I follow perfectly ! I think. I really don't need a resistor on my fullrange.....Which is fine. So I just need to put the resistor(s) in series with the tweeter ? Or would I be better to use lower values in parallel ? Now last question by adding a little more resistance to the tweeter, it would lower the output slightly would it not ? Also would I be better off using the 8 ohm fullrange instead of the 4 ohm ?
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