Want to foll off high freequencies to tweeters

Gary Batson

I want to roll off the high freequencies above about seven kilohertz going to the directional tweeters in my SDA 1's. What would I put between the crossovers and tweeters to do this?

Systems

A small inductor added after the tweeters hi pass filter will give you a shallow 6db per octave treble roll off.The value of the coil would be calculated using the tweeters nominal impedance.

ben62670

His phase most likely would be incorrect if he did that. Depending on the driver he might have to reverse the + and - on the tweeter . What I did to my SDA2's was disable the SDA tweeter(they cross at 2500), and replace the main tweeters first resistor with a 2.7 ohm instead of 4ohm. Done and done. Polk changed the design after they did that with the first generation SDA's. It does work very well, and cost less than $10. Then of coarse get the RDO tweets, and then change all the caps. THEN you are done. For a while:)

Systems

The coil will only change the phase 45 degrees so it is unlikely you would need to change the polartiy.

But Ben has a different solution that is worth a try.

Gary Batson

I don't want to completely disable the tweeter because its response dips so far into the midrange. in fact when I pulled the fuse on the tweeter I found that the tweeter produced most of the midrange. I think I need it for imaging. The high frequencies comming from both the stereo and the deminsional tweeters seem to resonate in my ears causing spikes at higher frequencies and pain. I tollerate it because I like the SDA effect. I have the new tweeters and they are an improvement.

Gary Batson

If a coil changes the phase of the tweeter. Is there a way to change it back? That would probably effect imaging. I don't know how to figure what size coil I need. I need to be told outright. Just pretend that you're talking to somebody really stupid. It wont be far from the truth.

Gary Batson

I don't want to completely disable the tweeter because its response dips so far into the midrange. in fact when I pulled the fuse on the tweeter I found that the tweeter produced most of the midrange. I think I need it for imaging. The high frequencies comming from both the stereo and the deminsional tweeters seem to resonate in my ears causing spikes at higher frequencies and pain. I tollerate it because I like the SDA effect. I have the new tweeters and they are an improvement.

ben62670

Hi Gary. You are absolutely right that the tweets affect the mids. I changed out my tweets to Morels in one of my speakers, and lost a lot of the mids, and highs. I had to change the resistor to a 2ohm to get it right again. The same thing happened with my SDA2's. Thats why you need to take out the 4ohm resistor, and replace it with the 2.7ohms(it will bring your mid, and high level back up), and disable the dimensional tweeter. It cost less than $10 bucks. The SDA3.1TL's only used one tweet, the Monitor 12's, RTA15TL's, and so on. The new tweets can definitely handle the job by using a single driver. Polk quickly took the dim tweeter out of the design, and they also dropped the XO frequency to 2000. At 2500hz there will be no issues at all with a single tweeter. The SDA effect will still be present, but the highs will not be reflecting with phase issues around the room. Again that is why they dropped the dimensional tweeter. Sorry to be repetitive here, but I have done this mod, and it worked very well.

Good luck with what ever path you take.
Enjoy your speakers:)

Ben

PoweredByDodge

... adding a coil after the existing crossover network will not simply add a 'nice' rolloff, unless the tweeter is only highpassed. if the tweet is bandpassed already, then the coil in series will screw with the slope. that being said, the likelihood of a factory built bandpassed tweet is slim. g'luck.

scottnbnj

have you thought about room acoustics or tried acoustic treatments? if you haven't, it might be worthwhile try that before altering the speaks.

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Ricardo

Or you could get the replacement tweeters from Polk; the SL2000's (which I assume are the ones in your SDA?) are known to have spikes at some frequecies that I don't recall now. The new silk tweeters eliminate that.

avguytx

Seems like I read that it's a 4 to 5db peak around 14 or 15kHz. One of these days, I'll get me some RD0's to compare. At least I'll extra tweeters for swapping around in the Monitor 10B's, too. Those are next on the list for some redo. Well, sometime soon.