Subs to tops ratio?

[Mark M]

What as a rule of thumb is the ratio between subs and tops? If I was running 1K through the subs what should I be looking at for the tops?

 

The application is for a band PA.

 

Thanks

[TonyMitchell]

What as a rule of thumb is the ratio between subs and tops? If I was running 1K through the subs what should I be looking at for the tops?

 

The application is for a band PA.

 

Thanks

 

 

Amplifier power is irrelevant. What boxes are you using? Look at the efficiency of each box and base your calculations on that. Also keep in mind the type of music being played... if a particularly bass heavy act or genre, you will probably want to bring some extra subs.

[Mark M]

Sorry that wasnt a very good question. If the subs were rated at 1k RMS @ 4ohm what do I need to match the tops too? At times we'll be putting a full band through it and at others just a drummer.

 

The system will be used with quite a bit bottom end, were actually putting on a drum clinic event which will consist purely of 3 drum kits (not played at the same time) and backing music, but we want that rock and roll sound to make the kits sound good.

 

Edit, not sure on the boxes yet. Just pricing a few things up.

[Simon Lewis]

Mark,

 

What Tony was saying is that the power applied is not indicative of the acoustic pressure achieved in front of the loudspeaker. An inefficient box fed with 1kW could be quieter than a very efficient box fed with 100W.

 

You need to consider the stated loudspeaker sensitivity and the maximum continuous sound pressure level output.

 

Simon

[Mark M]

Ok thanks, I dont have any stats to hand at the moment but do the stats need to match? Ie 120db sensitivity from the tops to 120 to the subs? Or do the subs need to be more?

 

Sorry if this is a really stupid question but havent really got the foggiest about any of this.

[themadhippy]

The other thing to consider is the crossover frequency,from an old fane book

X-over Frequency (Hz)	Power to Bass (%)	Power to Mid+High (%)
250						   40							60
350						   50							50
500						   60							 40
1,200						 65							35
3,000						 85							15
5,000						 90							10

[Simon Lewis]

The other thing to consider is the crossover frequency,from an old fane book

 

The Fane book carries the caveat that "certain electronic music and reggae may have increased bass content"! It would not be unusual to provide a significant portion of overall power to the bass passband in a modern band or music playback system.

 

It does make sense to have the boxes reasonably well matched in terms of sensitivity, but if you ask the manufacturers they will suggest recommended pairings for their products.

 

 

Simon

[TonyMitchell]

Mark, you will often find mid/top boxes are more efficient than subs of the same series/brand.

For example, d&b Q7 (mid/top box) plays to 138dB, whereas Q-SUB plays to 133dB.

When using just one Q-SUB (per side) with a Q7 on a stick, I trim 3dB off the Q7s.

[djandydee]

If the subs were a single 18" reflex and the tops were a 12" reflex and a 1" CD on a CD horn like a typical DJ setup at a wedding, you would need about 1000 watts in the subs and about 200 watts in the tops for the desired meaty sound.

 

Having measured quite a few top end systems, it is not un-common to see a 10dB boost in the 40-80hz range (sub) which when a known track is played sounds very full and warm.

[mervaka]

through what drivers?

[mostlyharmless]

I've seen plenty of rigs with twice as many subs as tops.

 

All depends on what your speakers are, and what sounds right. Do the manufactuer have a recommended matching sub/top pair?

[Boltonguy]

when you add subs to a pa system, you are taking away the problem frequencies from the tops. therefore the tops can be driven a little more without clipping. I would say a couple of 500w tops would be fine on top of 1000w subs. but like the others say, we really need to know the make/model of the subs to give a more acurate response. Along with size of venue etc. Hope this helps.

[johndenim]

I'd suggest having a look at a few systems

You will find that there are all kinds of combos, 12" sub to 8" top, 15" sub to 10" top, 18" sub to 12" top, even x2 18" subs to x1 12" top.

 

personally some systems suggesting a 15" top with a 15" sub are sometimes a little lacking in the LF department.

Go into your local retailer and have a listen, specs can come after you like whatever combo you hear.

[mercuryavltd]

What as a rule of thumb is the ratio between subs and tops? If I was running 1K through the subs what should I be looking at for the tops?

 

The application is for a band PA.

 

Thanks

 

It is a rough rule of the thumb : but we use a ratio of 60% power to the subs, with 40% power to the tops for a portable PA system. This seems to work well in real life applications. ( The ratio assumes a crossover point in the region of 120Hz and that the sub and top cabinet are similarly efficient/sensitive )

 

1000W / 60 x 40 = 666W

 

To answer your second point, the sensitivity figures don't need to match, but if there is a difference you need to allow for this. i.e. if the tops are less sensitive than the subs then you might need to allow more than 40% of the total power for the tops accordingly.

[bobjones1888]

I try and have 3db more low frequency than mid/high frequency and it generally seems to work out pretty damn good 98% of the time. But that's just my opinion, and what works for me. For you, you might want more low frequency. I find it out in this way :

 

Say I have a pair of a tops that are rated at giving a peak spl of 136db (I just use the peak spl as a guid in order to get some idea about getting 6db more low frequency), then if my subs are rated at 132db, I'll have 4 subs, so peak spl (generally take off 6-10db to get a rough idea at what spl you might actually get) 138db. Don't do what a lot of people do and go by the wattage of the speakers. Wattage rtatings tell you nothing about how loud a speaker or sub will be, it only tells you how much wattage they can take.