What did I just do here?

[Hi Ho]

I built my speakers a few years ago and have been very happy with them. When I designed the crossovers with the help of some members of the AudioKarma forum I vaguely remember something about possibly needing to pad the tweeters with some resistors. I never did and I thought the speakers sounded great if not a little hot on the high end. I was looking through some random parts the other day and found two 4 OHM ceramic resistors that I purchased when I ordered the parts for the crossovers. I recalled the discussion and decided to put the resistors inline with the tweeters and see what happened.

Wow! What a difference. I thought they sounded good before but they simply sound fantastic now! Gone are the occasionally harsh highs and occasional bursts of "over-brightness". The imaging is much improved. I can sit on the couch and not have to have my head in a vice to get an amazing sound stage.

What exactly have I done? Did I simply reduce the level of the tweeter? Are there any other effects to adding a resistor like this? Here are the schematics and the woofer/tweeter:



Tweeter: Dayton DC28FS-8 (8ohm)
Woofer: Dayton RS150S-8 (8ohm)

I inserted the 10W 4ohm resistor inline with the positive lead to the tweeter.

 

[TLS Guy]

I built my speakers a few years ago and have been very happy with them. When I designed the crossovers with the help of some members of the AudioKarma forum I vaguely remember something about possibly needing to pad the tweeters with some resistors. I never did and I thought the speakers sounded great if not a little hot on the high end. I was looking through some random parts the other day and found two 4 OHM ceramic resistors that I purchased when I ordered the parts for the crossovers. I recalled the discussion and decided to put the resistors inline with the tweeters and see what happened.

Wow! What a difference. I thought they sounded good before but they simply sound fantastic now! Gone are the occasionally harsh highs and occasional bursts of "over-brightness". The imaging is much improved. I can sit on the couch and not have to have my head in a vice to get an amazing sound stage.

What exactly have I done? Did I simply reduce the level of the tweeter? Are there any other effects to adding a resistor like this? Here are the schematics and the woofer/tweeter:



Tweeter: Dayton DC28FS-8 (8ohm)
Woofer: Dayton RS150S-8 (8ohm)

I inserted the 10W 4ohm resistor inline with the positive lead to the tweeter.

The resistor is in the wrong place. It needs to go right before the tweeter. Also the resistor will raise the impedance and change the crossover point. If you can tell me the sensitivities and the impedance of the drivers I can help you design a correct L-pad.

 

[Hi Ho]

The resistor in the schematic is not the one I just added. I added a second just in front of the tweeter that is not shown in the schematic.

Here are the full specs of the tweeter and woofer:

Woofer

Tweeter

 

[TLS Guy]

The resistor in the schematic is not the one I just added. I added a second just in front of the tweeter that is not shown in the schematic.

Here are the full specs of the tweeter and woofer:

Woofer

Tweeter

Someone made a bad mistake drawing out the circuit. That four ohm resistor in the high pass filter is in the wrong place. I have never seen a circuit like that and the filter Q is upset. I have done a model and there is a nasty peak at 1500 Hz and then dip.

Take out the four ohm resistor from the current position and shunt the tweeter with it. Now place a 5 ohm resistor in series with the positive tweeter terminal to the 6 mfd cap.

Get rid of the 1.5 ohm resistor and then connect the 12 mfd cap directly to ground. Then you have a nice crossover with good diffraction compensation.

The low pass filter is better without that 1.5 ohm resistor changing the Q of the filter.

 

[Hi Ho]

Where does that leave the crossover point? Also, these aluminum drivers have some pretty nasty breakup above 3.5K so in theory the crossover was designed with a rather steep slope.

I really don't know what I'm doing here but I'd be willing to try your suggestions. The only thing I'm missing at the moment is a 5ohm resistor.

 

[TLS Guy]

Where does that leave the crossover point? Also, these aluminum drivers have some pretty nasty breakup above 3.5K so in theory the crossover was designed with a rather steep slope.

I really don't know what I'm doing here but I'd be willing to try your suggestions. The only thing I'm missing at the moment is a 5ohm resistor.

For now just use your two four ohm resistors, one in series with the tweeter, and one in parallel. If the HF sound hot, just add the 1.5 ohm you remove and put it in series with the four ohm resistor in series with the tweeter. You can play with the series resistor until you get the balance you want.

Crossover is just below 2 kHz. I did not touch your notch filter. The composite electrical and acoustic slopes are fourth order at crossover, nice and symmetrical. The even order slopes make for a good lobing pattern.

Changing the resistors like I'm suggesting makes the whole thing a lot better and smoother. The diffraction compensation is also optimized.

You can test it out without spending a penny.

 

[Hi Ho]

What about the .25mh coil? With that coil still there doesn't the circuit still look very much the same if I do what you say?



Would I move that 4ohm resistor to the other side of the coil?

 

[TLS Guy]

What about the .25mh coil? With that coil still there doesn't the circuit still look very much the same if I do what you say?



Would I move that 4ohm resistor to the other side of the coil?

The 4 ohm resistor must move to the other side of the coil. It should never have been like that in the first place. And get rid of the 1.5 ohm resistor in the low pass circuit. Connect the coil to ground when you remove the resistor.

 

[Hi Ho]

I followed your suggestions using the 4ohm in place of the 5ohm and I have been listening to the speakers quite a bit. I also inserted the 1.5ohm resistor to tame the tweeter. There is a definite improvement. There certainly was a peak around 2k and I don't hear that anymore.

What difference does a 5ohm resistor make as opposed to a 4ohm? I have no idea what each individual part is doing in this circuit or how they affect the sound.

 

[TLS Guy]

I followed your suggestions using the 4ohm in place of the 5ohm and I have been listening to the speakers quite a bit. I also inserted the 1.5ohm resistor to tame the tweeter. There is a definite improvement. There certainly was a peak around 2k and I don't hear that anymore.

What difference does a 5ohm resistor make as opposed to a 4ohm? I have no idea what each individual part is doing in this circuit or how they affect the sound.

It pads the tweeter a little more. Did you move the 4 ohm resistor to the correct side of the coil in the high pass filter? That is the most important change of all.

 

[Hi Ho]

Yes, I moved it. I just changed the center speaker tonight and it all sounds great. I think i'll keep it as is and just make it more permanent. Right now the crossovers are just sitting unsecured.

 

[TLS Guy]

Yes, I moved it. I just changed the center speaker tonight and it all sounds great. I think i'll keep it as is and just make it more permanent. Right now the crossovers are just sitting unsecured.

I thought that would be good. The design modeled well with the mods, not good before.

So I hope you will be happy with them now.

Crossovers are difficult. I have spent all doing a slight mod to the couple of powered active crossovers that provide the step correction signal to a couple of the drivers in this rig.

Thanks for the follow up!