Just bought some passive waterproof speakers to be ceiling mounted in the bathroom. They're 80 watt, 8ohm, pretty bog standard. The problem is this - when we have e.g. an iPod plugged into a cheap Bluetooth speaker via a 3.5mm audio cable, it produces an acceptable volume. However, when we connect the wires for the bathroom speakers into a headphone jack and plug this into the iPod, it is considerably quieter, not really loud enough at all.

The speakers certainly have enough power, so is there something else causing the issue here? Could e.g. the Bluetooth speaker have an inbuilt amp, hence why that is loud enough? The speakers were only cheap, so we don't want to go spending loads on an amp - plus there's the issue that if we needed an active amp, that would mean messing about with batteries/power cables in the attic, which is a lot of hassle. Are we just best to return them or is there a simple solution here?

We'd want to be able to play the speakers from a 3.5mm jack so that we could connect it to phones/iPods etc. Any help/advice much appreciated, thanks.


closed as off-topic by Kaz, Joe Hass, Samuel, Anindo Ghosh, Daniel Grillo Jan 16 '14 at 5:21

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  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Kaz, Joe Hass, Anindo Ghosh, Daniel Grillo
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    \$\begingroup\$ The power rating for a speaker doesn't mean that the "speakers...have enough power". Speakers don't have any power. The rating tells you how much power an amplifier can deliver to them without damaging the speakers. \$\endgroup\$ – Joe Hass Jan 15 '14 at 23:39
  • \$\begingroup\$ The Bluetooth speaker has an internal amplifier, by definition, as the signal received by Bluetooth RF is a digital signal which is converted to analog and then amplified to a level that suits. | There are a class of reasonably easy solutions that go like: - Run cable from your speakers to a point outside the "wet area". Ideally to somewhere with mains power. - Find as cheap as possible an amplifier wity 3.5mm input that drives its speaker or speakers as loud or louder than you require. - Open it up (or use external spkr jack if provided) and connect to the leads to your speakers. ... \$\endgroup\$ – Russell McMahon Jan 16 '14 at 9:57
  • \$\begingroup\$ ... Semi-worst case this probably involves cutting or desoldering the wires to the existing speakers and adding the wires to yours. See below re impedance. - If 3.5mm input to amp is accessible to you, use it.If not, run an extension audio input lead. - POwer the amplifier (from the mains that is available in the place you chose :-) . || - A possible cheap msource are "powered speakers" intended for PC use. These are usually lowish cost unless they have fancy $ multiplying brand labels attached. Often available used at low or no cost. | Impedance of speakers may be <> 8 Ohms. ... \$\endgroup\$ – Russell McMahon Jan 16 '14 at 10:00
  • \$\begingroup\$ ... 3 Ohms or similar is commonish. 16 Ohms maybe. MAY be high impedance but not usually. 3 to 16 Ohms may work OK. You are very unlikely to hurt your speakers - if the amp does not like it it may distort but this is usually when 8 Ohm amp drives 3 Ohm spkrs and not vice versa. 3->8 will usually give lower volume. Best is an amp that uses 8 Ohm speakers. You can get a better match of sorts to 3 Ohm speakers. A low cost 2nd hand amp that will be POK in this application is often low cost used (depending on country). ... \$\endgroup\$ – Russell McMahon Jan 16 '14 at 10:09
  • \$\begingroup\$ ... A matching transformer can be used if amp and speakers differ in impedance but this is unlikely to be attractive. \$\endgroup\$ – Russell McMahon Jan 16 '14 at 10:09

Headphones jacks aren't intended to drive speakers directly. Headphones differ from loudspeakers significantly in two ways:

  • headphones typically have substantially higher impedance, some hundreds of ohms, compared to the typical 8 ohms of a loudspeaker.
  • headphones, being right next to your ears, need substantially less power to achieve a suitable volume.

To solve this, you need an amplifier somewhere, one intended to drive loudspeakers. No way around it. An iPod (and likely any other device with only a headphone jack) can simply not output enough power to drive loudspeakers without help from an amplifier designed for that purpose.

  • \$\begingroup\$ Thanks for the answer, was all I needed to know. Cheers. \$\endgroup\$ – ecs Jan 15 '14 at 23:40

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