So you've heard someone mention ribbon tweeters, how amazing they are, and now you want to get the inside scoop. You may have also heard people say how fragile and difficult they are to use in cars. Well, now's the time to separate fact from fiction and learn what issues you need to know about when using ribbon tweeters in your car.
First off, what is a ribbon tweeter and how are they different from regular tweeters? Here's a look at an Aurum Cantus g3si ribbon tweeter:
Imagine your regular old dome tweeter and voice coil. With a ribbon tweeter, there is no separate dome and voice coil. The aluminum ribbon element acts as both the radiating element (the dome) and the voice coil together. Also, the ribbon element is much thinner, lighter, and faster to respond than your typical coupled voice coil and dome tweeter.
So what are the advantages of a ribbon over a regular dome?
- High sensitivity and superb dynamics. Less than a few watts will typically yield very high spl levels. Also, above a certain frequency usually 10khz or so, a ribbon acts as a line source meaning that for every doubling of distance, you lose only -3db rather than -6db like you would with conventional point source drivers. The longer the ribbon, the lower the frequency.
- Greatly improved horizontal off-axis response resulting in excellent high frequency detail retrieval, a more open and "airy" sound, and a wider/deeper soundstage.
- Very fast decay times, which give you a smooth, uncolored, and grain free sound. The worst example of this here is your typical metal dome tweeter, which can be extraordinarily detailed but sound harsh and "metallic".
- A limited vertical dispersion. Simply put, the sound present above and below the tweeter is greatly reduced in comparison to the sound radiating directly in front, and to the sides of the tweeter. This is an advantage because it reduces in-car reflections from the floor and the underside of the dash when mounted in kickpanels.
- In the case of Aurum Cantus tweeters, replacing/reconing the ribbon is extremely cheap and easy, usually costing you only a few minutes of time and about $5-$10 USD.
- Limited vertical dispersion. While this can be an advantage, it can also be a disadvantage. The tweeter must be aimed directly at the listening position, otherwise the spl will drop off. Can be a pain to work with if there are 2 people of different height sitting in the car.
- Fragile ribbon element. Yes the ribbons are very fragile. You do not want to blow directly on them, and they require steep crossovers usually 18db (3rd order) or above to protect them from overexcursion. It is also absolutely recommended that you place a capacitor inline with the tweeter to prevent them from being damaged by turn on/off noises etc.
- Size. These suckers are pretty big and deep.
A pic of an Aurum Cantus g3 ribbon with a protective cap inline:
A pic of an Aurum Cantus g3 ribbon installed in the kickpanels of a 94 Honda Accord:
Unequalized frequency response of a g3 ribbon (red and green lines) mounted in the kickpanels. Measurement taken at the driver's headrest. Note the steep rolloff at 1.5khz, and the flat extended response out to 20khz!
Compare the high end response to the Morel mdt-43... a conventional tweeter known for having excellent high end dispersion. This tweeter was heavily equalized to boost it's upper end frequency response. It still doesn't quite make it to 20khz
Some tips for using ribbons in cars
- Kickpanel mounting is generally best because these guys are big!
- 1-5 watts is plenty of power, and will easily play at painful listening levels.
- Always use an inline capacitor to protect the ribbon. A Solen 27uF poly cap works fine.
- Make sure to vertically aim the tweeter at your head level.
- Use a steep 18db (3rd order) or higher highpass crossover.
- Loud bass or slamming doors will not damage the tweeter. Stepping on the tweeter will not damage it either, since the ribbon sits behind a strong protective grille. I've personally recorded spl levels > 135db in car without any damage to the ribbon element, and after nearly a year of constant use with people stepping on the driver, kicking it, and slamming my doors hard the ribbon is still in pristine condition.
So who makes ribbon tweeters? Check out these links for more info:
Fountek ribbons are generally cheaper and offer similar performance to the Aurum Cantus units, but are considerably more expensive to fix and utilize plastic bodies instead of solid aluminum.
There is also another category of tweeters called "planar tweeters". You can think of them as close cousins to ribbon tweeters. The most noteable difference is that the planar is not a pure aluminum element as with a "true" ribbon, it's in fact usually a plastic or similar sheet with aluminum embedded in it. It's also attached to the frame on all sides, whereas a ribbon is only attached at the top and the bottom. Personally, I have yet to hear a planar driver that can match the performance of a "true" ribbon tweeter.
Just wanted to update this post with a new type of ribbon design by LCY. My experience with this driver is that it uses a shorter ribbon than usual, stacked side by side and a horn loaded faceplate. What this does is radically increase the vertical dispersion of the ribbon, giving a more spacious soundstage with a wider sweetspot. These ribbons are also a tad bit smoother sounding than any other ribbon I've used from AC, Fountek, to Raven.
Compare the vertical response from your typical 12cm ribbon to that of the LCY-130. (These pictures taken from www.lcy.com.hk and are copyright of LCY)