Keeping your rig alive! How to not break stuff.

DiMarco

nutcase
Good Vibe Sponsor
Joined
Nov 19, 2009
Messages
6,839
Reaction score
3,780
Part one - Keeping your amplifier alive: Ohms! What are they anyway?

Short answer: impedance. The current the electrical circuit can handle.

I'll use the much used waterpipe analogy because I think this makes it easier to understand.
When we throw a signal at our speakers, think of this signal as the water and think of the impedance as the pipe.

The audio signal acts as the water flowing through the pipe. The bigger the pipe, the more easily water can flow through it. Bigger pipes also handle more volume of flowing water. A speaker with a lower impedance is like a bigger pipe in that it lets more electrical signal through and allows it to flow more easily.

As a result, you see amplifiers that are rated to deliver 500 watts at 8 ohms impedance or 1000 watts at 4 ohms. The lower the impedance, the more easily electricity flows through the speaker.

A lot of amplifiers aren't designed to work with 2ohm loads. Using the pipe analogy you can put a bigger pipe in, but it'll only carry more water (audio) if you have a pump (amplifier) powerful enough to provide the extra flow. If the amp can not keep up, it will heat up trying and roast. For this reason manufacturers state the maximum pipe size (minimum amount of ohms) the amp can handle without risking this damage.

When we hook up cabinets to the powersection of an amp you can either daisychain the cabs or in the case of two speakon outputs, you can hook up each cabinet to its personal output. In both cases you are connecting the cabinets in parallel - not in series unless it is specifically stated otherwise. Keep that in mind. By running the pipes parallel, you increase the pipe's total volume thus lower the amount of ohms.

Calculating this amount is done as follows: 1/ohms cab1 + 1/ohms cab2 + 1/ohms cab3 + 1/ohms cab4 = 1/ohms total.

So for example if we have two 8 ohm cabs and one 4 ohm cab the equation is this: 1/8 + 1/8 + 1/4 = 1/2 or 2/4 or 4/8 which is 0.5 ... 1/0.5 is 2 thus there is a total impedance of 2 ohms.
Second example: one 8 ohm cab and one 4 ohm cab: 1/8 + 1/4 = 3/8 which is 0.375 ... 1/0.375 = a total impedance of 2.6667 ohms.

Do note when combining non-matching impedances you're connecting both a thick pipe and a thin one. The 4ohm cab will be receiving more signal then the 8ohm cab will in that second example.

Because we do not like calculating too often, here's a short table of real life speaker cabinet combinations you can expect to work at which impedance:

8 ohm:1x 8 ohm
4 ohm:1x 4 ohm or 2x 8 ohm
2.6667 ohm:1x 4 ohm + 1x 8 ohm
2 ohm:2x 4 ohm or 4x 8 ohm or 1x 4 ohm + 2x 8 ohm

IMPORTANT: An amplifier will perform best when matching its output impedance with the input impedance of the speakers ie connecting it to the waterpipe size it was designed to work with. For instance hooking up a 16ohm cab to a 4 / 8 ohm rated output might work but will result in unpredictable EQ deviations and less power. And I repeat: if you connect too big a pipe (too low an ohms value) to your amp it will fry because it can not deliver the current and run too hot trying.

(FYI: calculating the impedance when connecting speaker units in series is done by simply adding up the impedances ie 4+4ohm = 8ohm. But unless you're building speaker cabs yourself this is of no importance within the scope of this post.)





Part two - Keeping your speakers alive: Watts! Watt are they anyway?

Short answer: measured power the amp can throw at your speakers without distorting the signal.

Remember the analogy? 4ohm pipe vs 8ohm pipe -> bigger pipe is the 4ohm one so that will handle more watts. For this reason manufacturers state the output in watts at both 8 and 4 ohms, also 2 ohms if the amp can handle that.

There are two main reasons a speaker can break: Mechanical damage and its coil burning out.

The amount of watts a speaker can take tells you something about beyond what amount of watts this speaker will start sounding bad or even damage itself from trying to move too much. The speaker cone can only move back and forth a given amount of millimeters. If it starts reaching its maximum it may damage or get stuck mechanically. This amount of millimeters is refered to as the speaker's XMAX. The speaker's suspension and voice coil are designed to work within the boundaries of this XMAX value.

By throwing too many watts at the speaker, you are pushing it too far and it will either break mechanically OR its speaker coil overheats and burns out. But speaker coils can also burn out from another, often overlooked cause...

If an amplifier can not deliver the amount of watts for the sound level you need, and you turn up this amplifier too loud its signal will start clipping. In doing so, the amplifier introduces DC components into the signal. What this does to your speaker is keep it positioned either all the way inward or all the way outward and hold it there for a moment. As a result, the voice coil of the speaker will start heating up. If it heats up long enough or hard enough it will burn and your speaker will not work anymore.

But it can get worse! Some amplifiers are not designed to run without any speakers connected. Burning your voice coil can be like disconnecting your speaker from the amp, which can result in sparks flying and the amp itself burning out too. Luckily though tube amplifiers distort in a different way then solid state amps do and seldomly incorporate said DC components. It is mainly these tube amps that can not be used without any speakers connected to them.






Part three - Keeping your rig alive: Don't do stupid things! and gear considerations

With the impedance/ohms in part one we can simply calculate what we should or should not do. With the watts story in part two however everything depends on your behaviour. Do not ever let solid state or class D amps clip and try to never let your speakers flap out!

If you need higher volume levels from your rig here are the only two simple but important considerations:

1. Your amp can never be overpowered (if you act sensibly with it) but it can be underpowered for your needs. My Ampeg can produce 1600 watts, I use it at rehearsals with a cabinet that is rated at 450. The amp has a lot of headroom this way and I will not ever turn it up to the point where the speakers start distorting or flapping out. Other bandmembers would be really pissed if I turn it up louder anyway. If I let another band use my rig however and their bassist is stupid, he/she could well fry my cab with my amp. Be aware of the stupidity factor when other people are involved. Match your amp and speaker watts if others use your gear sometimes.

2. If you really love your amp's sound but want it to be louder, more cabinets does not have to be the solution. Each speaker is different in respect to how efficient they are. My Barefaced cab is rated at 103 decibels measured at 1 meter distance when throwing just 1 watt at it. My home built Celestion cabinet will only have an output of 94 decibels from that same signal. This means the Barefaced will produce far more noise with a small amp then the Celestion cab ever will. Speaker efficiency is always reflected in the speaker cabinet's price but these more efficient cabs are way less prone to breakage as a result. Keep this in mind! Investing in good cabs pays off.


Okay that's all for now. Stay safe guys and keep rockin'
 
Last edited:

DiMarco

nutcase
Good Vibe Sponsor
Joined
Nov 19, 2009
Messages
6,839
Reaction score
3,780
Some tricks for your rig to go louder:

1. Don't use a smiley face aka scooped EQ setting within band context. It makes you drown in the mix and too much of your amp's energy gets thrown at the lowest frequencies that way.

2. Using a graphic EQ, bandwidth optimizer or parametric EQ cut everything under 40Hz to a certain extent. Your E string sits at 41.2Hz. Drop D is 36.7Hz, low B 30.87. The second harmonic of the B0 (61.7Hz) is much more evident in the mix anyway and all you do with sub frequencies is get in the way of the kickdrum. Cutting the sub frequencies frees up MANY MANY WATTS for you to use at more important frequencies and will enable your speakers to go much louder without flapping out. This means cutting those sub frequencies will make your rig sound tighter and go a lot louder.

3. If you use a compressor to take out the worst spikes in your audio signal, your rig will also be able to be used at a louder volume without damaging stuff. You can do this without obviously squashing your signal.



Some tricks for your rig to appear louder in the mix without actually being louder:

A ten band graphic or parametric EQ pedal can work wonders if the EQ controls on your amp are fairly limited.
Know the EQ frequency ranges by their nature so you can utilize the many possibilities of the midrange to be able to punch through a dense guitarmix better.
They say "the magic is in the midrange" for a reason. Here's the nature of useful frequency ranges for bass (and guitar), ordered by low frequency to high:

20-32Hz: Rumble.
40-65Hz: Ground.
55-90Hz: Bottom.
90-160Hz: Boom/Punch.
130-230Hz: Warmth.
250-450Hz: Fullness/Mud.
450-850Hz: Honk.
750-1500Hz: Whack.
1kHz-2kHz: Tinny.
2kHz-3.5kHz: Crunch.
3.5kHz-5kHz: Edge.

Everything over 5k can be considered Treble. and plays no real role in sounding loud/present in the mix or not.

If you want fatness in the mix, focus on Boom/Punch to get there. More presence is obtained with Warmth and Fullness for a bass. Cut some honk if your bass already has too much of that. Get a more aggressive tone with Whack, Crunch or Edge depending on your taste. Never boost Rumble frequencies whatever you do. String noise from roundwounds sits in the Tinny and Crunch ranges. And once more: Don't scoop out the colourful mid frequencies but learn to use them. Sounding good solo at home is something different then sounding good in a mix. You really do not have to be overly loud to be clearly audible in the mix on stage.
 
Last edited:

Henrythe8

Dolphin Hoarder
Joined
Dec 15, 2013
Messages
2,494
Reaction score
840
Age
48
HAHAHAAAAA, love it. Great post.
I'd like to add one thing : Parametric Mids.
There always is this resonating frequency that changes from one venue to another. I usually play with the mids boosted, and then search which frequency is badly resonating . When I find it, I usually cut it off. Regadless of the EQing of my general sound.
 

Henrythe8

Dolphin Hoarder
Joined
Dec 15, 2013
Messages
2,494
Reaction score
840
Age
48
The Frequency Map should be a thread on its own. :)
We use at least two different sets on preamp : the one in the basses and the on in our amps. Not to mention what we have on our pedalboards. I'm not sure we all are familiar with the frequencies we boost/cut on our basses.
I'm not as proficient as @DiMarco on those. My personal experience tells me that the three bands I'm interested in are
60 to 80hz for bass, which roughly translated into the bottom.
200 to 600hz for mids, which is broad but allows me to dial lowmids in the low area or upper "Honk".
3kHz for Hi. Over 3k is in my opinion not worth fiddling for.
 

DiMarco

nutcase
Good Vibe Sponsor
Joined
Nov 19, 2009
Messages
6,839
Reaction score
3,780
Depends on the sound you're after. The 10k treble on a Warwick LWA amp can give you some more air. The John East uni 4 knob onboard pre lets you decide where you want your treble freq to sit, mine is around 7500Hz. Mid control has a sweep which I haven't really needed yet.

The trick is making your sound work in the mix and with mids a little (1 or 2db) goes a long way.
 

Henrythe8

Dolphin Hoarder
Joined
Dec 15, 2013
Messages
2,494
Reaction score
840
Age
48
With my tinnitus, I don't really hear high frequencies anymore. :)
 
Top Bottom