# I have a question ( Coaxial in parallel with tweeter )

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Hello Guys!, My name is Franz and I have big question i know you can answer easily.
1 year ago i got a 4 channel amplifier capable of 75 W rms per channel at 4 ohm and 100 W rms at 2 ohm per channel.
I hooked up 4 coaxial full range speakers of 4 ohm (One per channel). The problem was
i was lacking of highs. So i am thinking about adding extra tweeters to my system by putting
them in parallel with the coaxial speakers with their respective crossover (crossover only for the
tweeters because the coaxial are full range(they have mid bass and tweeter)).
Is that solution ok, or is it wrong? (For example: 4 ohm coaxial in parallel to 4 ohm tweeter per
channel: So the amplifier is gonna see 2 ohm per channel, so my max power per channel
is going to be 100 W rms) Mathematically i know, the impedance is not linear in the
frequency axis and the coaxial is gonna request more power than the extra tweeter butttt....
And here is another question, if i turn up the volume slowwwwly,
how i know when my amplifier or tweeter is gonna blow up or start clipping?
Post data: My neighbor has an oscilloscope hehehe.

My actual system is: (JBL 600Wrms 4ohm mono amp ==> subwoofer Rockford P3 600Wrms 4ohm)
(Rockford prime amp r400-d4 ==> 4 coaxial speakers = Rockford T1650)

(in the future ==> one new amp for adding only midrange woofer and bullet tweeter)

#### Galu

Hi Franz and welcome to the forum!

Just need to clarify what you have in mind.

Do you intend to put an extra tweeter in parallel with the existing tweeter so that both are driven by the existing crossover components in the coaxial speaker?

Or, do you intend to put an extra tweeter with its own crossover components in parallel with the entire coaxial unit?

As to your second question, if you turn up the volume to the point where the amp or the speakers are becoming stressed, then your ears should tell you to stop!

P.S. If you run your system to such extremes on a regular basis then this could damage the high frequency response of your ears!

P.P.S. Clipping shows up on a 'scope when a pure sine wave input arrives at the amplifer output with the peaks and troughs cut off so that it begins to resemble a square wave.

#### Perry Babin

Yes, clipping will be visible on the scope but you won't have the scope in the vehicle and the volume position isn't a good indicator of the clipping point since music varies so greatly.

The breaking point of the tweeter is virtually impossible to predict due to the number of variables. Common sense helps but the levels are high enough in a car environment that it's difficult to tell where the tweeter starts to become distressed unless it's a really low power tweeter. With a bullet tweeter, who knows. They are typically so awful that they always sound distorted.

#### Galu

It will be safe to add an extra 4 ohm tweeter in parallel with your coaxial speaker provided you put a non-polar film capacitor in series with the tweeter.

This will not reduce the overall load of the amp to 2 ohm except maybe at the high frequencies where there is not much power involved anyway.

I suggest using a 6.8uF film capacitor.

Hi Franz and welcome to the forum!

Just need to clarify what you have in mind.

Do you intend to put an extra tweeter in parallel with the existing tweeter so that both are driven by the existing crossover components in the coaxial speaker?

Or, do you intend to put an extra tweeter with its own crossover components in parallel with the entire coaxial unit?

As to your second question, if you turn up the volume to the point where the amp or the speakers are becoming stressed, then your ears should tell you to stop!

P.S. If you run your system to such extremes on a regular basis then this could damage the high frequency response of your ears!

P.P.S. Clipping shows up on a 'scope when a pure sine wave input arrives at the amplifer output with the peaks and troughs cut off so that it begins to resemble a square wave.
Hello Galu! First of all, thanks for your reply. I am trying to to put an extra tweeter with its own crossover components in parallel with the entire coaxial unit. And yeah. So for sound quality: tweeter > bullet twetter?

#### Galu

Hello Galu! First of all, thanks for your reply. I am trying to to put an extra tweeter with its own crossover components in parallel with the entire coaxial unit. So for sound quality: tweeter > bullet twetter?
It's OK to do that, and you'll have seen my suggested minimum requirements in post #5.

However, you may wish to give the tweeter better protection from low frequencies by using a 2nd order crossover (4.7uF in series with tweeter and 1.5mH in parallel with tweeter).

Bullet tweeters are usually used in PA systems where sound pressure level is more important than purity of reproduction. Perry says they sound awful in a car environment, and I would tend to agree with him.

I ran a mobile disco back in the 70s and I know a little about playing music loud. So don't get me wrong when I mention that I've read that you car audio guys turn up the bass and mid frequencies so loud that the high frequencies get swamped. I suspect that may be why you want the additional tweeters!!

It's OK to do that, and you'll have seen my suggested minimum requirements in post #5.

However, you may wish to give the tweeter better protection from low frequencies by using a 2nd order crossover (4.7uF in series with tweeter and 1.5mH in parallel with tweeter).

Bullet tweeters are usually used in PA systems where sound pressure level is more important than purity of reproduction. Perry says they sound awful in a car environment, and I would tend to agree with him.

I ran a mobile disco back in the 70s and I know a little about playing music loud. So don't get me wrong when I mention that I've read that you car audio guys turn up the bass and mid frequencies so loud that the high frequencies get swamped. I suspect that may be why you want the additional tweeters!!
hahahaha, thanks Galu! So i will watch your #5 post and get that requirements in mind

#### Galu

One final thing Franz.

I recommend you choose a tweeter that has a sensitivity figure which is higher than the 88dB @ 1W/1m of the Rockford Fosgate T1650 coaxial.

This will ensure that the treble is reinforced in the way you desire.

If the tweeters turn out to be too loud you can always calm them down by inserting a 10 or 20W ceramic wirewound resistor in series with the crossover capacitor.

The resistance value would have to be determined by experiment, but is likely to be in the region of 1.0 to 3.9 ohm.

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