Im playing in a 4 piece indie rock band, with two 100w boss katana and a relatively enthusiastic drummer for the genre. We play at small venues, clubs, outdoors and the stage size is usually not that big. That, and because of the fact we dont have a van, is the reason why I would like to go as portable as possible. I would love to just use a 2x10. Adding a second 2x10 sounds like very flexible rig also. I should mention that I have never used a 2x10 before.
My experiences so far were only 4x10 and 1x15. I had good and bad experiences with both. Im into funk and love the response of 10", don't need the low end 15" deliver. I usually boost the upper mids. My worst experience was a 4x10 warwick on stage (couldn't hear myself at all) and a 1x15 in a small room.
Do you think a 2x10 could be enough? How many watts class d then?
Would a 1x15 maybe be the compromise Im looking for in terms of dimensions and realative speaker cone area?
Or maybe even 2x12 would be the slightly smaller alternative to 4x10?
The first thing is to figure out how loud you need to play. I am usually good with a rig that can produce about 124dB calculated. My last touring rig was good for almost 127dB calculated. I did some gigs where more SPL would have helped me hear better...but I am only willing to play so loud, and I don't think I ever pushed this rig close to it's max.
For context, my cab was an Eden D210XLT with a 103dB 1W/1m sensitivity rating and the rig had about 250W of usable power.
SPL results from two things: usable power and speaker sensitivity. How much power you can use is determined by how much power is available from the amp, and also how much power your speaker can handle. This information is usually stated in the specs for the amp and cab.
The power the amp can provide depends on the impedance of your speaker system. For example, the big Mesa Subway amps are rated for 400W at 8 ohms, and 800W at both 4 and 2 ohms.
The next think you need is the sensitivity rating of the speaker. Again this is usually included in the specs. Most companies express the rating as the resulting SPL measured at 1 meter when 1W is applied. A 1 Watt sensitivity rating will look something like this:
97dB 1W/1m
You may also see sensitivity rating that are expressed in terms of 2.83V at the rated impedance. For example:
98dB 2.83V/1m at 4 ohms
97dB 2.83V/1m at 8 ohms
The trick here is 2.83V at 8 ohms is 1W and 2.83V at 4 ohms is 2W. To convert the 4 ohm rating to a 1W rating, simply subtract 3dB:
98dB 2.83V/1m at 4 ohms = 95dB 1W/1m
The final step is calculating the decibel change that occurs when the power is raised from 1W to however much power you can use. The result is then added to the 1W/1m sensitivity rating, which produces the calculated SPL.
Formula:
Calculated SPL = [Log(Usable Power) x 10] + Sensitivity Rating
Let's assume an 8-ohm cab with a 97dB 1W/1m sensitivity rating that can handle 350W and a big Subway amp. The amp can make 400W at 8 ohms, but we can only use 350W.
Here is the formula with the specs inserted.
Calculated SPL = [Log(350) x 10] + 97
Calculated SPL = 122.4dB
122.4dB is the calculated SPL at 350W for a speaker with 97dB 1W/1m sensitivity rating.
Since this is a bit shy of 124dB, it may not be quite loud enough for my needs (in some situations)...it may be entirely fine for you...are you may find it totally inadequate.
If we decide to add a matching cab, the power handling doubles, the impedance is cut in half, and the sensitivity goes up by 3dB.
So the impedance of both cabs connected in parallel is 4 ohms. Our amp can make 800W at 4 ohms, but our speakers can only handle 2 x 350 = 700W. The combined sensitivity rating of the cabs is 97 + 3 = 100dB 1W/1m.
Let's input these figures into our formula to see how loud the rig is with two cabs.
Calculated SPL = [Log(700) x 10] + 100 = 128.5dB
-By adding a matching speaker and doubling the usable power, we get about +6dB.
-If you double the speakers and hold the power constant, we get about +3dB.
-Most solid state amps increase the power a bit when the impedance is cut in half, but they don't double the power. So you get an increase between 3dB and 6dB.
If you plan to add a cab, either get a matching cab or a cab that is specifically designed to work with your existing cab. Also make sure your amp is safe at the combined impedance provided by the cabs. Why?
It is possible to design cabs with different driver sizes so that they play well together, but this is not always done, even within the same product line. Pairing cabs that are not designed to work well together is unlikely to produce optimal results. It may result in poor tone quality, and it may even reduce the maximum SPL your rig can produce. Many solid state amps are designed for 4 ohms minimum. This means they can safely push a pair of 8 ohm cabs, but not a pair of 4 ohms cabs...which results in a load of 2 ohms.
The final bit of (hopefully) helpful info I will provide is to recommend that you don't make any assumptions about driver size and voicing. I tend to like a cab with nice mids, rather than deep subby bass. Some of my favorite cabs have had 15' drivers. Likewise, some cabs with 10s are voiced to produce massive lows. When it comes to a cab's voicing, designer intent is way more important than driver size.
If you are considering a solid state amp, I would recommend a power rating between approximately 500W and 800W. Next decide how big of a cab you want and how many you are willing to cart around. Do the math to identify which cabs can meet your expected SPL requirements. Ideally you demo the contenders and select the model that produces the type of tone you want.
Make sure you understand the impact impedance has on the amp's power ratings. Amps that run 500W and 800W at 4 ohms may only put out 250W and 800W at 8 ohms. So if you plan to get a single 8 ohm cab it becomes more important to select a model with a high sensitivity rating. Likewise, if you decide to get a pair of 8 ohm cabs with a super high sensitivity rating, an amp that pushes 350W at 8 ohms and 175W at 4 ohms may be more than enough.
Good Luck!
