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[john sanders]

Just wanted some thoughts on the practice of running top cabinets full range while also using subs.

[Tom Young]

Just wanted some thoughts on the practice of running top cabinets full range while also using subs.

This would fall under the heading of "sloppy practices".

Even a weekend warrior with no budget for or interest in complex measurement and a decent DSP loudspeaker management system can figure out how to get the fullrange high-passed so there is minimal overlap, etc. This provides clearer/cleaner sound in that frequency range.

Doing so also helps protect the fullrange (the woofer in particular) from the abuses of attempting to reproduce too low energy at higher levels.

If you refer to those who may do this intentionally (other than the few who do utilize overlapping for clealy defined benefit), I can't relate and therefore I have no comment.

[john sanders]

Thanks Tom,

I needed a clear explanation of why this is "a sloppy practice" and you certainly gave the answer I was looking for.

[Chuck Simon]

It can work depending on the capability of your top cabs.  If you look at tunings for JBL SR 4700 series, for example, you will see that they suggest the "sloppy practice" of running tops full range. 

"The SR4731A and SR4733A have the subs programmed as more bass boxes with the LF of the SR473X going all the way down. The alternative of course is high passing them at 80 Hz."

[Kevin McDonough]

Thanks Tom,

I needed a clear explanation of why this is "a sloppy practice" and you certainly gave the answer I was looking for.

If you run the tops full range and also have subs, your going to have some overlap where they're both playing the same frequencies (probably in the 60-100Hz region depending on the speakers in question).

In theory, this could be used as a benefit. If you measure the delay on each woofer and line them up so they were both playing perfectly in phase they would combine at those frequency and you would get a boost in volume.

However in real life this wouldn't work, for two reasons.

Firstly each woofer will have group delay. Without getting too technical, this basically means that the delay isn't a constant for each cabinet, but instead is different for different frequencies. So even if you measured and lined them up at one particular frequency, they would quickly drift out again as you move to frequencies either side.

and secondly, even if the group delay for those two woofers somehow miraculously matched and you could delay them to both be in phase perfectly, that would only count for that point in space. As soon as you try and move the measurement mic around the room, the path difference could change and so the delay would need to be different.

Soon as you try and mix driver sizes, or cabinet types (bandpass and reflex etc) playing the same frequencies you're always gonna have problems and as Tom says its sloppy practice. It'll make a noise, but be muddy and have phase problems as you move around the room, and not be as clear and sound as good as it should.


Ideally you always want to have one type of speaker playing each band of frequency. So one set of matching speakers (say 18"s) playing sub, one other band of speakers playing mid (say the 12" section of a set of mid tops) and one other playing highs etc etc.

You should have have minimal overlap of the frequencies at the crossover, and delay them so they're in phase at the centre of the crossover frequency. Hopefully the slopes of the crossover lower the sound quick enough on either side of the crossover point that as they begin to drift out of phase the volume and so effects caused are minimised.

(However unless your using expensive FIR filters, the crossover slopes themselves add a phase difference to that band of sound, more pronounced as the slopes get steeper, and so it becomes a bit of a cat and mouse game of tweaking and adjusting to find the best balance of crossover frequency, overlap/slope, phase, delay etc that gives you the best overall sound both per cabinet and for the system overall)


k

[Scott Carneval]

Even if you could get the subs and tops perfectly phase-aligned, which as Kevin explained is near impossible, the boost in volume will come in the 50-100hz range, which is a range which most PA systems have more than adequate response.  It won't add anything at all in the 30-50hz range, which is what I suspect you're trying to improve. 

[Chuck Simon]

"the boost in volume will come in the 50-100hz range, which is a range which most PA systems have more than adequate response."

Really?  I would think that the reason one would attempt to run their tops full range would be to get more volume in the 50-100hz range, and I assume that is why JBL suggests it.

You know club owners and their audiences want, no demand, excessive amounts of low end and if that is your only way of achieving it, I say give it a try.  They probably aren't going to have any test equipment on hand to judge your decision.

[Scott Carneval]

"the boost in volume will come in the 50-100hz range, which is a range which most PA systems have more than adequate response."

Really?  I would think that the reason one would attempt to run their tops full range would be to get more volume in the 50-100hz range, and I assume that is why JBL suggests it.

You know club owners and their audiences want, no demand, excessive amounts of low end and if that is your only way of achieving it, I say give it a try.  They probably aren't going to have any test equipment on hand to judge your decision.

I guess I don't really consider much above 60hz to be bass...more like just boominess.  I want chest thumping, hard hitting, shake sh!t off the walls bass. 

[Tracy Garner]

Just wanted some thoughts on the practice of running top cabinets full range while also using subs.

I depends - Whenever I do this it is for a specific purpose based on the amount of headroom I have on the top-cabinet amps. Yes it defies audiophile principles. At the same time, the audience wants loud. Those overlap frequencies are in the "drink more" range. It works when properly deployed.

[Ivan Beaver]

Just wanted some thoughts on the practice of running top cabinets full range while also using subs.

I run the tops full range-within their rated response.

The reason is simple.  If you crossover the tops to the subs-and then send a signal that has moderate bass response (say male vocals-guitars etc) only to the tops (that may be high passed at say 80Hz), then they will sound "thin".  The only way to 'warm them up" is to run them to the subs-kinda bypassing the whole idea of specific instruments going to the subs.

While if the "full range cabinets" went down to say 50hz, then they would have plenty of "warmth" without having to send the signals to the subs.

Of course the mains and subs have to "play well together" for this to work.

It really depends on how you want to look at the overall signal processing.  Getting hung up on one aspect-can leave gaps in others.

[David Parker]

Just wanted some thoughts on the practice of running top cabinets full range while also using subs.

Well, there are ways to do anything I guess, but I'll relate my experience. I had 2-15+horn tops and double 18 subs. My thoughts were that if I ran my tops full range, they made a certain amount of bass. If I added the subs to that, it would make MORE bass. IN my case, that was wrong. I had no way of time aligning the tops and bottoms, and at the time didn't even know what that was. My tops and subs fought each other, and I tore up LOTS of 18's trying to get the system to work. I got a proper crossover and hi passed the tops and lo passed the subs and had a LOT more bass, a lot cleaner bass, and never blew another 18. I'm sure somebody a lot smarter than me can make it work just fine, but I couldn't. After I split things up with a crossover, I had no more problems and started making money instead of keeping my reconer in business.

Try it and see what happens, but be sure and make it an A-B test. Make sure your changes actually help. Your cabs may play together just fine.

[Robert Weston]

For most shows, I run my tops (1 x 15" and horn) in full-range mode (i.e. using the full-range input); however, the top cabs are only producing around 100hz and up (subs handling everything else below) - crossover is a dbx-260.  It sounds good and there's plenty of power, and guests/attendees/managers provide good comments on the sound quality.

Over the past many years, it seems that internal crossovers have greatly improved.  I used to have to tri-amp because internal crossovers were crap, but now it seems any quality cabinet made in the last 10 years has a decent crossover.  It it works full-range, I'll do it... if not, I have the option of bi-amping the tops.

[Patrick Tracy]

Just wanted some thoughts on the practice of running top cabinets full range while also using subs.

Heck, even without subs I high pass my tops. I use the same crossover and sweep the frequency down toward the -3dB point of the speakers.

[Ivan Beaver]

It is a common thought that by running the full range and subs so they overlap-then you will get "more bass".  This is generally not true (even if properly aligned). 

The reason is that (in many cases) the subs will be run quite a bit hotter than the full range-so the level from the full range in the sub area is way down (typically 10-15dB) so they add very little-if any-to the output.

But if not aligned they can subtract.  IF you figure that if you have 2 cabinets and get perfect summation-you can pick up 6dB.  But in worse case you could get complete cancellation.

So as usual-it depends.

[Merlijn van Veen]

It is a common thought that by running the full range and subs so they overlap-then you will get "more bass".  This is generally not true (even if properly aligned). 

The reason is that (in many cases) the subs will be run quite a bit hotter than the full range-so the level from the full range in the sub area is way down (typically 10-15dB) so they add very little-if any-to the output.

+1

Only when subs and tops are run at equal levels and are phase alligned in the overlap region, i.e. by means of all-pass filters, you could achieve up to 6 dB of summation. This bump could be equalized on the input of your DSP without loss of power. This practice could benefit small setups that need the extra power. This "marriage" can hold over distance depending on the physical displacement, which nobody seems to have mentioned AFAIK. I've you stack your tops directly onto your subs, you most likely won't find any listening positions with more than 120 degrees of phase separation, read 0 dB summation or even cancellation, in most cases. However act with caution.

[Don Boomer]

I run the tops full range-within their rated response.

Wow ... your answer surprises me, but I respect your opinion and must admit I've always followed the conventional wisdom here and used a crossover.  So I guess I've never actually tried it.  Well, maybe that's only partially true as I usually run aux fed subs.

I guess this will give me one more project to test out (when I get some spare time )

I guess I usually have all the lows I need and would rather make the trade off to cut them from the top box in exchange for the extra margin of power handling and reduced distortion.

[George Friedman-Jimenez]

I run the tops full range-within their rated response.

The reason is simple.  If you crossover the tops to the subs-and then send a signal that has moderate bass response (say male vocals-guitars etc) only to the tops (that may be high passed at say 80Hz), then they will sound "thin".  The only way to 'warm them up" is to run them to the subs-kinda bypassing the whole idea of specific instruments going to the subs...

Ivan, do you send bass and kick (and keys?) to both the subs and tops but vocals and all other instruments only to the tops?

[ProSoundWeb Community]