Speaker Break In and How to Do It Yourself, With a Mythbusters Section

By Jim Seavall

There’s been a lot of speculation on speaker break in for guitar amp speakers on the Internet. Much of the information online is based on subjective opinion, and not much real world testing. I’m writing this article to try to dispel the myths and misconceptions.

First, yes speakers break in. That’s a fact. How long they take to break in has many factors including the materials used in the speaker, how flexible those materials are (or can be) and how long it takes to loosen them up. All speakers are made in pretty much the same manner using a cone, attached to a voice coil, a dust cap to protect contaminants (dust, dirt, etc) from getting into the voice coil and it’s gap around the pole piece it is centered around and a spider/suspension piece that holds the voice coil in place to keep it centered at the bottom, and the cone is glued to the frame to keep it stable on the frame edge.

Some speakers use a compound called “doping” around the top cone edge and the dust cap, some don’t. It depends on what the speaker maker is designing the tone of the speaker for, and other factors affecting the control of the cone from moving too wildly and producing cone cry, and other typically unwanted noises.

While a speaker works fine out of the box, typically they’re very tight, bright and don’t respond as well to the nuances of pick attack, gain, volume level adjustment we guitar players like to employ while playing. Breaking in the speaker makes the cone, spider and related parts more pliable, and easier to move. When this occurs you can get a fatter bass response, trim the treble harshness, widen the midrange tones and warm up your entire tone, which results in a bigger, broader speaker voice.
As guitar players, anything that broadens our tone, while not ripping our heads off with treble is usually considered a good thing!

Getting a speaker broken in takes a lot of loud playing time (more than 25w typically), or a lot of movement to the speaker parts to make them more pliable, which makes the speaker more responsive. How much time and volume depends on your speaker’s construction materials, and how big your magnet is (light 35 oz to heavy 50 oz and beyond to 14 lb magnets in JBL’s and EVM 12’s). The reason the magnet size is a factor is that the stronger the magnetic pull on the cone, the harder the cone is to move. That’s because the heavier magnetic strength limits the cone movement more than a lighter magnet since the voice coil is reacting with the magnet. That’s why an “H” heavy magnet speaker takes longer to break in than an “M” medium magnet weight. Of course you can lengthen the break in time on the H model to get broken in, and typically it’s an extra 35-40% longer due to that difference.

Breaking in the speaker naturally by playing;   Go ahead, it’s going to break in eventually, but the louder you play and the more often you play, the faster it breaks in because a bigger signal is sent with the volume increase that moves the speaker parts more, making them more pliable and responsive. Breaking in the speaker can be done in other ways as well. You can wire your speakers to your stereo system at home, turn on some music with lots of low end, low mids, turn up the bass and mids, turn down the treble, turn up the volume to approximate 25w or more of power and let them get played by the stereo to break them in. Make sure you have neighbors that aren’t too close, won’t call the cops on you if they are, and like the music you’ve chosen to blast through your speakers while you’re at work! You can also use a variac (variable output transformer) to break them in. The variac puts out a 60 cycle hum that moves the speaker parts similar to a bass guitar in the low E and A strings. The bass frequencies move the speaker more than the treble frequencies, so they’re preferable to break in from my tests. The major consideration in this method is how much voltage to use so you don’t fry your voice coil while still moving the speaker. The smell of a burnt voice coil is not pleasant so let’s avoid that, not to mention the expense involved with reconing the speaker, since you then have to break it in again.

Variac break in procedure:

First you need a variac with at least a 1 amp capacity, with a dial that lowers the voltage to 5 volts. These are pretty common to find, and run around $80 or so on eBay with shipping. Next, you need a cable to hook up to your speakers. I use a 4x12 cabinet that has a ¼ jack on it (like your guitar amp speaker output jack) but I use an old computer cable with the IEC end (not the male 3 wire prong end, you need that to plug into the variac). You cut off the IEC end of the cable that plugs into your computer (the female end), and you’ll usually find three colored wires, white, black and green. The white goes to the positive of the ¼” plug, the black to the negative of the plug, and the green wire is cut and taped off. You need this type of cable to handle the voltage the variac will send to your speakers. DO NOT USE AN INSTRUMENT CABLE, YOU WILL FRY IT IN SHORT ORDER!

Next you’ll hook up your cab to the variac, but there is a very important task you need to do FIRST. You will need a multimeter. You’ll need this to check the voltage coming out of your variac through the cable you’ve made. This is critical. Too much voltage, fried speaker. I’ve done extensive testing on breaking in speakers, and the higher wattage voice coils take longer to break in and can handle more volts, the lower wattage coils less time, less volts. You will set the variac dial to the lowest setting on its dial. Plug in your cable (loose), not in the speaker jack yet. Hold the multimeter leads on the plug end, red cable to the tip of the plug, black cable to the barrel of the plug. Turn on the variac and slowly turn the dial until it reads 9 volts (or close). This is the setting I use for most speakers that are low power models (20-30w). If you have a 65w speaker, then you are safe at 11-12 volts.

How I arrived at these voltage settings is simple. I measured my 50w Marshall clone with the volume set at 9. According to previous measured results with an oscilloscope, waveform generator, etc my amp builder determined it puts out 95w at 9 on the volume knob resulting in a voltage reading of 36 volts to the cable in the speaker jack. If you set the variac at 9 volts, you’re essentially sending about 25w to the speaker, which is many speakers limit. Assuming your speakers are wired in parallel each one gets that voltage. It will be quite loud at this setting, you’ll want to leave the room, or do this in your garage, studio or your worst enemies garage, if you can gain access!

With the 65w speaker types you can go to 11-12v, which is around 35w of power sent. I strongly advise you not to exceed this voltage so you don’t fry your speaker voice coil. You could do a higher voltage at your own risk, but then you’d need a digital timer set to two hours on, one hour off to cool the voice coil, and have it run for about two days. For a decent amount of break in you’ll need to do an M magnet about 16 hours, and around 20-24 hours for an H magnet. This gets the speaker broken in and sounding warmer quite nicely. There is still about 5-10% of break in left to do, and that can only be done by more playing, or loud club/concert level playing as it will move the cone even more due to playing attack, palm muting, open chords, etc. While the variac could do this, it would be bordering on being unsafe for the voice coil to run that hot with a higher voltage used without taking breaks. I recommend no longer than 24 hours in one session at the 9-12v settings described above, then give the speakers time to cool (feel the magnet, if it’s hot, time to let it cool) before doing anymore.

You can also run the variac at a lower voltage level, and run it longer. I don’t recommend more than 3 days with my speakers (with break time to cool), and this is in a closely controlled/monitored environment. It requires removing the speaker from the cab each day, test it with a waveform generator to make sure the voice coil isn’t burnt and rubbing every 24 hours. Most clients aren’t going to go for that much hassle, so it’s your choice. I rarely do it myself, as I find it’s more fun to go to an open mic night or jam session with friends and do it that way.

There are plenty of myths out on the net; time to dispel some.
1) You cannot break in a speaker properly with 5 minutes of playing, I don’t care what volume you use. Whoever came up with that isn’t a guitar player.
2) You cannot run your speakers at 26 volts all night and expect them to survive. I have documented pictures of the results, and it’s not pretty. Most often you will fry the voice coil, in one case the speaker caught on fire and burned the cone/coil and the wire attached to it. I was lucky. My FBI break in cab (FBI = Factory Break In) has a lid on it, which limits the airflow to feed a fire. However I was very upset to find this speaker burnt up following the builder’s break in technique, and then they refused to rebuild it although it was brand new and I used their instructions (which they have now removed from their site so as not to tarnish the legacy of the person who posted those instructions) to break in the speaker.
3) You can break in a speaker too fast, and too far. I’ve done that as well in my testing, which is why the voltages I’ve set out above are what I have found are safe. While the speaker may be broken in, it can be so loose that it sounds tired. All speakers break eventually, they don’t last forever. But artificially breaking them in to sound good is one thing. Doing it to the point of destruction and poor tone won’t make you happy.
4) Power handling/volume. A 20w M75-PVC Scumback with the KRAFT paper voice coil is just as loud as the 65w nomex version. The voice coil determines the power handling, not the decibel output. That is a function of the cone used, magnet weight, etc. A higher powered M75 is just as loud as a lower powered M75. It’s the same for my entire line, so low power speakers break in faster, but are the same volume as the high powered speakers.
5) Large magnets put out more decibels. H series speakers usually are in the 99/100 db range, M series around 96/97 db, it depends on the cone type (55 or 75hz, and what rib type is used on the cone, there are differences). Your typical JBL or EV speaker has a 14 lb magnet, which is why it puts out 104 db. They also use 4” wide voice coils to wrap more wire on the coil to handle more power. The myth comes from that build scenario. It’s not the higher power 150/200w voice coil that makes the speaker louder, it’s the huge magnet field from the larger magnet.
6) Cone Cry: You can make any speaker produce cone cry. The object is to make sure it doesn’t happen in the guitar’s usable range, which is usually from round 80 Hz to 5khz. Cone cry is a nasty noise, showing up sometimes as a howl like a werewolf, or a bright pinging tone on high B & E strings, to a double tone that’s not a full octave off the original note it’s crying from. None of it sounds good. The only way around it is to dope the cone more, or not play those notes, or use it with your fuzz pedal to drown it out.
7) Square wave signals…these are generated when you use too much fuzz, overdrive, and the tone is so saturated it sends a square wave to the speaker. Speakers don’t tolerate square waves for a long time, they eventually get overheated and hang up in a set position in their excursion and result in getting a voice coil burn or fry. If you’re going to use fuzz, get 3 times the rated power of your amp’s power to offset the heat induced by the square wave. Even then there are no guarantees.
8) “Pushing the speaker hard sounds best!” Another myth that’s been going on forever. You will eventually ruin the speaker by “pushing it” with overdrive pedals without enough speaker power handling. You cannot run your 100w Marshall on 10 into a single 4x12 cab with four 25w or 30w speakers. Why? Because your amp is rated conservatively. That means once you pass it’s clean tone (3% distortion total) into a singing overdrive tone (naturally with the amp turned up around 6-8) you’ve gone from 100w clean at 4 on the volume knob to 180-200w at 8 on the volume knob. They sold two 4x12 cabs with those old Marshalls for a reason, they knew the speakers would blow. I have a JCM 800 manual available online that shows the 100w JCM 800 put out 115w clean at 3% distortion (4 on the volume knob) and in excess of 170w at 10% distortion (around 8 on the volume knob). Email me if you want it or go to this link to see it yourself. http://www.scumbackspeakers.com/specs/jcm800powerspecs.jpg
9) In closing, you can’t just run amok on your amp with your speakers unless you have enough power handling to run amok. Make sense? Towards that end I always recommend you get twice the speaker power handling of your amp’s clean rated power. That means 100w of speaker power handling for a 50w amp if cranked, and 200w for a 100w amp if cranked (or as I like to call it DIMED!). No one wants to fry their speakers or their output transformer after you fry your speakers. It’s expensive, you’re not playing through an amp and most electric guitars aren’t designed to sound good as an acoustic.

I hope this article helps clear up some of the myths, untruths, and regurgitated hype that’s on the internet regarding speakers and speaker break in. If not, email me and I’ll try to help. Now, get back to playing!

Jim Seavall
President, Scumback Speakers & Cabs, Inc.
sales@scumbackspeakers.com