How to Get the Best Sound Out of Your iPhone Car Stereo Adapter

Avoid interference and enjoy your sound

You've got an iPhone, you've got a car, and you want to use them together so you can enjoy your music wherever you go. Your options for connecting an iPhone to a car stereo include wireless adapters, cassettes, and CarPlay. Since CarPlay is a direct connection, the sound quality is just about perfect.

With the other options, though, you may find there's some radio interference or less-than-ideal sound. If you're running into this problem, try these tips for getting the best sound quality from your car stereo adapter.

Hands scrolling on smartphone, inside car
Getty Images/Klaus Vedfelt

Tips for Using an iPhone FM Car Stereo Adapter

FM adapters plug into your iPhone and let you send music from your iPhone to your car stereo using very low power, and therefore very short range, FM broadcasts that you tune in using your car's radio. When you do this, though, you’re likely to find that other FM radio signals interfere with your music.

Here are a few tips to reduce interference.

Try the High or Low End of the Dial

To broadcast a clear signal from your iPhone to your car stereo, you'll need to find an unused FM frequency. Check the low end of the dial (say 90.1 and lower) and the high end (107.1 and higher) for unused channels.

The rise of public, college, and religious radio is making it harder to find empty frequencies even at the low and high end of the dial, but you should be able to find something in many areas.

Look for Channels With No Neighbors

Most iPhone FM transmitters let you choose what FM channel you want to broadcast the signal on. You’ll get the best audio quality out of your FM adapter, and the least interference from other channels, if you broadcast the iPhone signal to an FM channel with no signals on either side of it. That is, the best channel to use will not only have any signal on it, but the frequency on either side of it will also have little to no signal either.

For the sake of this example, let’s use 89.7. To see whether 89.7 will work for you, check 89.5 and 89.9 also. If there is no signal, or only a faint signal, on any of these frequencies, you should be fine.

Finding a block of three frequencies with no signal is hard, so if you can’t find three perfectly clear ones, just try for those with the weakest signal interference.

Use a Station Locator

Some wireless car adapter manufacturers make tools available to help you find the best channel for broadcast in your area. Try the ClearFM app or the Radio-Locator website to get a good suggestion for an empty frequency.

When Your Area Is Saturated With Radio Stations

As more radio stations come online, it’s going to get harder to use an FM transmitter in your car without interference. People living in major cities saturated with radio stations already know this. If you live in one of these areas, you’re probably going to be better off using CarPlay.

If you’re not sure whether you’ve got enough empty frequencies in your area, be sure to check that return policy before to buy and hang onto your receipt.

Tips for Using a Cassette Adapter

No matter what kind of iPhone cassette adapter you buy, one made specifically for an iPhone or a generic one that can be had at any electronics or department store, you'll find that it's not always easy to get the best sound from the combination of iPhone and car stereo. Sometimes there's an audible hiss, other times the music isn't loud enough.

Try these tips to improve the sound:

Turn Up the iPhone Volume

Don’t turn it all the way up, but make it loud. Once the iPhone volume is loud enough, don’t change it.

Adjust the Stereo Volume

If you want to make the music coming through the car stereo louder or quieter, use the car stereo volume knob, not the volume buttons on the iPhone.

Keep the iPhone Volume Higher Than the Stereo Volume

Finding the right balance between iPhone and car stereo volume sometimes requires a little experimenting. Try not to raise the car stereo volume above the iPhone's volume. This can cause a hissing noise.

Try Tape A/B

If your cassette adapter is making a clicking noise, try using your car stereo's "Tape A/B" feature to play the other side of the adapter. Not all car stereos have this feature. Older models, and those that require you take the tape out to play the other side, won’t work.

Was this page helpful?