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Is it possible to re-wire car speakers (model JBL GT7-5) to a headphone jack (3,55 mm stereo plug) directly without an amp? And if not, what do I need to-do?

This what I know about the speakers:

  • 13cm (5.25") 2 way speaker
  • Peak power: 105 W
  • RMS power: 35W
  • Sensitivity: 93 dB (2.83V/1m)
  • Frequency response: 70 - 20 kHz
  • Voice Coil: 4 Ohm
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  • \$\begingroup\$ Probably not, have you thought what power the headphone jack is designed to provide? Not sure what you mean by a headphone "jackstik", not seen one for sale... You will probably need an amplifier to match the output to the speakers - are they 4, 8 or 16 ohm? \$\endgroup\$
    – Solar Mike
    Apr 13, 2019 at 18:18
  • \$\begingroup\$ This is what I know about the speakers: 13cm (5.25") 2 way speaker - Peak power: 105 W - RMS power: 35W - Sensitivity: 93 dB (2.83V/1m) - Frequency response: 70 - 20 kHz - Mounting depth: 57 mm - Mounting cutout diameter: 120mm - Voice Coil: 4 Ohm What I meant by 'headphone jack' was a jack you see normally used with headphones, i've deleted the 'headphone' part since it wasn't necessary for the question. \$\endgroup\$
    – Mukk3l
    Apr 13, 2019 at 18:28
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    \$\begingroup\$ Deleting "jackstik" and keeping headphone may have been better - and you have not answered the question about the headphone power... Do edit your question with all the info - you should not expect people to "trawl" through comments building your question like a puzzle... \$\endgroup\$
    – Solar Mike
    Apr 13, 2019 at 18:32
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    \$\begingroup\$ I'm beginning to think that "jackstick" means a 3.5 mm stereo headphone jack plug. \$\endgroup\$
    – Transistor
    Apr 13, 2019 at 18:34
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    \$\begingroup\$ Yes, exactly. @Greenonline (except I have two car speakers that's not connected to anything yet, but yes, I wanted to wire a 3.5 mm stereo jack to the speakers so I could connect them to my iPod/iPhone/whatever, but from the answers below it seems that it's not a possibility without risking shorting something) \$\endgroup\$
    – Mukk3l
    Apr 14, 2019 at 18:57

3 Answers 3

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It does seem that the other answers fail to address the question you have asked.

Is it possible to re-wire car speakers (model JBL GT7-5) to a headphone jack (3,55 mm streo plug) directly without an amp?

The short answer is no, you cannot connect a speaker that size to a headphone jack and expect to hear much sound; you also risk damaging the headphone amplifier if it is not short circuit protected.

This leads to the next question

And if not, what do I need to-do?

You need to add an amplifier between the headphone output and the speaker. There are plenty to choose from out there, as you are new to electronics, I suggest to get one that is enclosed and has its own power supply.

The key points to look out for are:

  • Output Impedance, this must be able to drive 4 Ω speakers, otherwise you will risk damaging the amplifier
  • Output Power, avoid amplifiers with a power output higher than the power that the speakers can take, or you will risk damaging them at high volume.

It will be up to you to decide if you want the amplifier to be battery or mains powered.

Here below is a simple schematic of how to connect the amplifier

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ I think the rest of us don't think s/he's trying to drive the speakers from a headphone output but, for some reason, wants to connect the speakers to a power amplifier through a 3.5 mm stereo plug. The plug would be on the right side of your schematic - between the amp and the speakers. And if they're bridge mode it's definitely going to cause problems. \$\endgroup\$
    – Transistor
    Apr 13, 2019 at 20:45
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    \$\begingroup\$ @Transistor the question is very clear, he/she asks if the speakers can be driven without an amplifier directly from the headphone jack. \$\endgroup\$
    – Elmesito
    Apr 13, 2019 at 20:48
  • \$\begingroup\$ The question has been edited several times. We were working with a "jackstick" in the beginning. OP may have accepted my answer too quickly. \$\endgroup\$
    – Transistor
    Apr 13, 2019 at 20:53
  • \$\begingroup\$ @Elmesito you will have an idea of how the original question started if you look at my first comment... \$\endgroup\$
    – Solar Mike
    Apr 13, 2019 at 22:41
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    \$\begingroup\$ The main idea is as stated above by Elmesito, the question has been edited to be more clear and precise, ill accept your answer @Elmesito, since it was what i was asking for - I accepted Transistor's answer since I didn't expect to get a better one, and I got the main idea, that i should not wire a jack directly to 35V speakers without an amp. \$\endgroup\$
    – Mukk3l
    Apr 14, 2019 at 18:51
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Yes, do it and have fun! You won't ruin anything, baring shorting your wires together. You'll learn a bit about speaker efficiency and amplifier power. (there is an amplifier in your source, it's just little.)

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  • \$\begingroup\$ What will happen the amplifier's output stage if the wires short or the contact short during insertion or removal? \$\endgroup\$
    – Transistor
    Apr 13, 2019 at 18:54
  • \$\begingroup\$ That all depends on the amplifier. Some amplifiers can tolerate short circuit indefinitely, some can not. Those that can not might have a fuse, or they might not. Also, most (ALL?) audio output circuits that have such a receptacle to take a jack should have already taken into account these momentary shortings, as they are inherent in the connector. \$\endgroup\$
    – Aaron
    Apr 13, 2019 at 19:31
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    \$\begingroup\$ @Transistor If anyone creates an amplifier that has a 3.5mm headphone socket, and the amplifier blows up whenever someone plugs in a 3.5mm plug, then that person was an idiot. \$\endgroup\$
    – Simon B
    Apr 13, 2019 at 23:07
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enter image description here

Figure 1. A jackstick?

A 35 W, 4 Ω speaker will require a current of \$ I = \sqrt {\frac {P}{R}} = \sqrt {\frac {35}{4}} = 3 \ \text A \$.

A Lumberg good quality equivalent is rated at only 1 A and you may find that the sockets are even worse.

Another consideration is the voltage. \$ V = \sqrt {PR} = \sqrt {35 \times 4} = \sqrt {140} = 12 \ \text V \$. This will be OK.

These jacks, however, are not suitable for this application as they can short as they are inserted and removed. This could destroy the output stage in your amplifier. You will also have considerable difficulty in wiring 3 A cable into a 3.5 mm jack plug.

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    \$\begingroup\$ 35W speaker does not require 3A!!! It is only capable of handling that much current. What happens if you only supply a 0.5V sinewave to it? 3Amps, I think not! \$\endgroup\$
    – Aaron
    Apr 13, 2019 at 19:36
  • \$\begingroup\$ Let's do the maths: As shown above, if you are running at 35 W the current will be 3 A. At peak power of 105 W the current will be 5 A. If you feed it with a 0.5 V sinewave then you'll get \$ I = \frac {V}{R} = \frac {0.5}{4} = 0.125 \ \text A \$. Music tends to have high-volume peaks as well as quiet passages and silence between tracks. Problems may occur with high resistance contacts, particularly on peaks and may lead to distortion as well as overheating. \$\endgroup\$
    – Transistor
    Apr 13, 2019 at 19:50

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