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8 Ohm 20 Watt Resistors to Tweeters?


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kenwood_nut 
Stock Boy - Posts: 227
Stock Boy spacespace
Joined: April 10, 2009
Location: Washington, United States
Posted: September 24, 2020 at 8:10 AM / IP Logged Link to Post Post Reply Quote kenwood_nut
After years of running tweeters in parallel with front speakers off my amps, I've never ran into any issues until recently. Not sure why. I'm guessing my newest amp has a more true RMS rating than past ones, thereby sending far too much power to the tweeters. Let me explain what's happening, then I'll get on to the reason for this post.
I purchased a pair of Alpine DDT-S30 tweeters with crossovers. To begin with, right out of the box, there was NO SOUND from the tweeters with the crossovers installed inline with the positive wires. When I removed the crossovers and ran the tweeters directly off the inputs, I got sound. That told me the crossovers were junk. Anyway, I then used a pair of 5,000kHz bass blockers inline with the tweeters, which worked well... for ONE DAY! Apparently I sent way too much power to the tweeters and fried them in one day! My 4 channel Nakamichi amp is rated at 75 wpc RMS at 4-ohms and 150 wpc RMS at 2 ohms, so it's obvious the tweeters got far too much power. Funny, I've run both Pioneer and Kenwood tweeters in parallel with front speakers off 4-channel amps in the past and never had a problem!
SO... next, I purchased a pair of Cerwin-Vega H7TAK tweeters rated at a much higher power handling than the Alpines. They come with really nice crossovers that are clearly marked with input and output sides. Problem is, it says in the owners manual that if you are running these tweeters off a high power amp of 75-150 wpc or more, you MUST use an 8-ohm 20-watt resistor! Well, I ordered a pair but am still waiting on them. In the mean time, I wanted to see how things worked running the tweeters in parallel with my front Pioneer 4-way door speakers. They sound AWESOME! Crystal clear highs! The difference in the car is night and day... for about 5-10 minutes at increased volumes, then I lose my highs! If I turn down the stereo or just turn it off, the highs come back like nothing happened.
One question here is are the crossovers that came with the tweeters shutting down when they get too much power, or is that the front channel of my amp? It's weird that the highs come back after a few minutes of cool-down time.
I've messed with car audio since back in the 70's when I was running the top-of-the-line Pioneer SuperTuner II deck into a Spark-O-Matic booster-equalizer into Kraco 6x9's baby! Oh yeah... memories! Then when I saved up some money from my dishwashing job, I moved up the a pair of Jensen triaxial 6x9's! LOL! Now, at 62 years old, I'm having to deal with and understand resistors in car audio for the first time ever! I'm just not understanding this stuff. If I lose ANY of the highs from my tweeters, I'm tempted to either buy a small 2-channel amp to drive them OR simply run them off my Alpine head unit. Guess I won't know until I get the resistors later this week.
Maybe at 62 years old a person tends to lose his or her understanding of car audio basics, but it also could be too much Corona every night or too many hours working which is affecting my brain cells and causing me to not understand tweeters and wiring them, but as I mentioned earlier, I've never had ANY issues with tweeters shutting down or frying when I ran them in parallel with my front speakers off a 4-channel amp UNTIL NOW!
Basically, I'm just wondering what difference the 4-ohm 20-watt resistors are going to make, and if they are going to cut down on the highs I hear.
Thanks for any advice or knowledge.
Custom_Jim 
Copper - Posts: 193
Copper spacespace
Joined: November 28, 2003
Location: Missouri, United States
Posted: September 24, 2020 at 11:17 AM / IP Logged Link to Post Post Reply Quote Custom_Jim
While you got me by a year (I'm 61) I have seen a lot of things change through the years. I used to work for 2 different Alpine authorized retailers here in Saint Louis, and since I had been away from them for years, so I did a search on those model tweeters you got and on a video there are counterfeit ones out there and I have to wonder, is that what you got ?.
Counterfeit Alpine Tweeters
Jim
1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street
1977 Nova (Sold)
kenwood_nut 
Stock Boy - Posts: 227
Stock Boy spacespace
Joined: April 10, 2009
Location: Washington, United States
Posted: November 28, 2020 at 8:16 AM / IP Logged Link to Post Post Reply Quote kenwood_nut
I got those resistors in and they DO help! I've been able to turn up my stereo pretty darn loud and not fry the tweeters! But one thing weird is I've noticed that after maybe 15 minutes to a half hour of cranking it up, the tweeters seem to lose their output and I lose my ultra highs! WEIRD! But if I turn down (or off) the stereo for a few minutes the tweeters come back on! It's like the resistors are getting overheated or something. I'm not sure. I'm not losing my front door speaker output, only the output from the tweeters!
Even though the resistors helped to not fry my new tweeters, I'm thinking about disconnecting them from the front speakers (I'm running them in parallel with the front door speakers)and connecting them right to the deck instead. This will bring my RMS back down to 75 wpc instead of 150 wpc RMS when the amp is getting 2 ohms. The amp will love me, and the tweeters will appreciate a break! But I know I'll lose a LOT of my highs!
Not sure WHY my tweeters shut down but not the door speakers when I crank it up for a few songs! I'm running the front channel of my 4-channel Nakamichi amp in high pass, not full range, so the front speakers are not getting much bass or mids, at least not enough to overpower them I'm guessing.
So WHAT exactly is shutting down on the tweeters? The 20-watt 8-ohm resistors? Or is it the crossovers? I'm stumped after 45 years messing with car audio!
Custom_Jim 
Copper - Posts: 193
Copper spacespace
Joined: November 28, 2003
Location: Missouri, United States
Posted: November 28, 2020 at 2:01 PM / IP Logged Link to Post Post Reply Quote Custom_Jim
Years ago I remember passive crossovers using thermistors in the circuit and I was told that they worked by reducing power by increasing resistance to a tweeter due to a rise in excessive current/heat ?. I wonder if there is something like that in a passive crossover you might be running ?.
Jim
1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street
1977 Nova (Sold)
kenwood_nut 
Stock Boy - Posts: 227
Stock Boy spacespace
Joined: April 10, 2009
Location: Washington, United States
Posted: November 29, 2020 at 8:14 AM / IP Logged Link to Post Post Reply Quote kenwood_nut
That very well could be the issue here! I was kind of thinking it wasn't the resistors, but not sure. The tweeters are Cerwin-Vega H7TAK's and they have some pretty nice crossovers, but "nice" doesn't mean they can handle heat. Since my Nakamichi 4-channel amp is putting out 150wpc RMS into both front channels because I'm running the tweeters and Pioneer TS-A1686R door in parallel, I'm sure those crossovers have every reason to get hot. Of course I've turned my front gains way down and my high-pass frequencies are set above 5,000Hz on the amp. But I wouldn't think mids and highs would produce as much heat as lows.
So, after reading your response, I came up with an idea! I think what I'll do is remove the dash cover over the radio/heater controls/vents on my Saturn Ion, then crank the stereo up for a while. As soon as I hear the tweeters stop putting out their highs, I'll feel both the crossovers AND the resistors and see if either seem hotter than normal. If they are, I'll look into some better tweeters or crossovers.
I'm a HIGHS nut, so I appreciate the highest highs I can get out of my stereo. Therefore, I have my 3-band equalizer in my Alpine UTE-73BT head unit set to the maximum level and my midrange set to 2, then on my Rockville R7EQ equalizer I have the 3 far right high frequency knobs at their highest setting! THIS is why I bought 6-1/2's that had high frequency response then added tweeters. As a drummer for years, I appreciate the "ting" of cymbals and the "ding" of xylophones! Every single day of the week I'm out in my car, SOMEONE yells over to me "Sounds NICE!", which tells me they (like me) can't stand hearing a car roll by where all you hear is bass pounding in the trunk but nothing more, even with all their windows down! Because those people just put an amp and sub in their trunk, probably ran it off the high-level speaker leads, but kept their car's stock speakers and no equalizer! I'm not trying to win any sound-off competitions or anything, but I want my music to sound GOOD! Crystal clear highs, with just enough bass to feel it and hear it, not vibrate my car apart! ;)
Again, I appreciate your reply! I'm going to seriously check into the heat thing!
8 Ohm 20 Watt Resistors to Tweeters? -- posted image.
8 Ohm 20 Watt Resistors to Tweeters? -- posted image.
8 Ohm 20 Watt Resistors to Tweeters? -- posted image.
8 Ohm 20 Watt Resistors to Tweeters? -- posted image.
8 Ohm 20 Watt Resistors to Tweeters? -- posted image.
Custom_Jim 
Copper - Posts: 193
Copper spacespace
Joined: November 28, 2003
Location: Missouri, United States
Posted: November 30, 2020 at 1:46 PM / IP Logged Link to Post Post Reply Quote Custom_Jim
Something else I remember doing and seeing was adding a filament type of light bulb in the crossover:
From a google search:
Light bulbs:
Over the years various manufacturers have employed various types of "light bulbs" wired in series with the speaker as a means of speaker protection. As the load current increases the bulbs filament heats up and the resistance of the light bulb increases thereby attenuating the power delivered to the speaker. The bulb actually acts like a "compressor" by turning down the peaks. Selecting the correct bulb is tricky and best left to professional designers who can conduct careful lab tests to select the right bulb. Not that you shouldn’t try it if you want. Just don’t expect some nice rule for making it work! Bulbs can be successfully used for live sound because they will not interrupt a performance. Hi-fi purists would likely be offended by the potential effects of bulbs on audio quality.
Jim
1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street
1977 Nova (Sold)

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