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Effect on frequency response from adding a 2nd cab

LoTone

LoTone

Clean as an Entwistle...
Supporting Member
Nov 4, 2010
1,993
2,628
Quebec, Canada
#1
I am wondering if there is some kind of acoustic effect affecting the dynamic range of a rig when adding a second cabinet.

For example, I just won an auction at The Bass Place The Bass Place - Homepage - The Bass Place for an Ashdown ABM NEO 408. It's a sealed tweeterless 4x8" cabinet.

If I add a second cabinet of the exact same brand and model, I understand that the overall rig will be louder because the 2 cabinets together will move more air but, will the fact of adding a second cabinet lower the overall usable frequency of the rig?
 
#3
CL400Peavey said:
No.
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Usable lower frequency at volume.... yes. I am not a scientist (somewhere, 200 TB'ers are saying "then stop now").

No, your cabs won't magically become rated for lower frequency (and I doubt that you were expecting that- I am guessing that you are asking merely on a practical level, "what's my bass gonna sound like?").

With a matching cab added (assuming a normal amp), you will have more overall volume available and more room to work with eq.

Low frequencies seem to be the determinants of speaker farting which requires one to turn down main (or cut bass which gives you a less bassy tone). Adding another cab will allow you to play at higher volumes without cutting the bass freq so you will be able to get a more bassy tone.

Even adding a 112 to 212, in my experience, just gives a way deeper tone at any volume level and then I eq accordingly.
 
#7
Two cabs will seem to go lower than one cab for this reason:

The frequency at which beaming (narrowing of radiation pattern) sets in will go down by about a factor of .7 for each doubling of driver cone area. This will happen whether they are stacked vertically or side-by-side. The net result is, less high frequency energy relative to the low end. It's not a huge difference, but it's real. Two cabs might measure the same as one cab on-axis, but the difference happens off-axis, and off-axis sound is like the elephant in the room. This is one of the reasons why it's hard to make a 210 that sounds like a scaled-down 810.

There is also an effect on dynamics. Let's say you have been bringing one cab and you notice that, at the end of a loud set, you have to turn up the volume control trying to maintain the same loudness, and the low end is mushy and everything is compressed. You might be inclined to blame it on your amp, and vow to get a bigger amp, but the problem is your cab: The woofer magnets are heating up so much that they are losing magnetic strength. Fortunately this is temporary, and by the start of the next set the magnets have cooled down and regained their strength and you forget all about it... well, until the end of the set. Now if you bring a second cab to the same gig and run at the same volume level as before, you will probably be just fine because less heat (half the wattage) is needed into two cabs and that reduced heat is spread out over twice as many motors so the magnets don't get hot enough to lose a significant amount of their strength. So by adding that second cab, you still have dynamics (pop and thump and impact) on the last song of that loud set.
 
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#8
Stacking cabs of equivalent capability adds oomph for several reasons - Duke lays out the basics above... not the least of which is as he explains the commensurate lesser effect of power compression = less loss of output to heat per driver at high output. Playing through a wall of drivers that are coasting inside their operative range - versus a a lesser number of drivers meeting the edge of their thermal ability - is a blissful experience.
 
#9
What I meant is that usually manufacturers document the "frequency response" of the cabinets with a pair of frequency from low to high. To me, that was the same thing as the dynamic range. My bad. Sorry for the confusion.

wcriley said:
Thread title is dynamic range.
Question seems to be frequency range.
??????????????????
Click to expand...
 
#12
Good grief guys, perhaps reviewing the math would be a good idea...

Yes, increasing the number of identical cabinets will increase the low freq. extension for a couple of reasons, the first being as a result of diaphragm coupling (dominant at low frequencies relative to wavelength versus source separation).

Another reason is that as the baffle gets larger constructive support improves. A driver on a baffle looks like baffle extension.

Then there's the improvement in linearity (small versus large signal model) of the driver system, and the ability to handle increased power at lower frequencies which open up the potential for active extension processing.

Also, dynamic range will increase as the maximum SPL will increase (especially when considering the added power capability)

Of course, adding size and weight are the tradeoffs!
 
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