• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Bass cab dual use filtering question

J

Jeroenslowend

Jan 3, 2020
27
10
#1
A few years ago I have build a fearful 12/6/1. Later i build an 12-Sub with its own low pass filter (CBG filter)
I used the sub once as a sub for my PA and was very pleased with the result. So I build another 2 12-Subs :) without filter, and they are driven bij an active crossover, crossed at 125Hz and their own amp.
For a bigger show I would like to deploy 2 subs per side. So: I have 4 greenboys, 2 with filters, 2 without filters.
I would like to know if the passive filter changes the phase response?
Should I add a switch in the the cabs with filters to bypass the highpass filter, or can I just connect them in parralel 2 per side?
 
#2
This an example of a setup in cardiod configuration
 

Attachments

  • IMG-20230704-WA0007.jpg
    IMG-20230704-WA0007.jpg
    18.8 KB · Views: 21
#3
AFAIK the filter only impacts the phase through the crossover region.

image-682.png

Notice that the -3dB point is considered the knee. However, the filter is having an impact at a lower frequency.

If I understand the filter on the subs is the same LPF used on the 12/6/1. If this is true, I believe the crossover is around 850hz. So my guess is crossing the sub at 125hz should put it outside of the range where the filter has a significant impact on phase response.

Still...if it were mine, I would probably add a switch to bypass the filter.
 
#5
Jeroenslowend said:
For what reason would you do that?
And would you switch both end of the filter, or just connect the speakon input directly to the + and - of the speaker, leaving the filter connected?
Click to expand...

I would disconnect the filter.

That doesn't necessarily mean you should worry about it. IMHO do an experiment. Compare the two cabs with filters to the two cabs without filters...if you can't hear a difference, maybe you're good to go.
 
  • Like
Reactions: Hoochie Coochie Man
#6
If that's a 2nd order filter, there can still be significant phase shift an octave above the effective crossover point.

Seems like a complicated (or inconvenient) solution to a problem that maybe isn't a challenging as the solution (IMO).
 
  • Like
Reactions: RColie and bottomzone
#7
agedhorse said:
If that's a 2nd order filter, there can still be significant phase shift an octave above the effective crossover point.

Seems like a complicated (or inconvenient) solution to a problem that maybe isn't a challenging as the solution (IMO).
Click to expand...


From the fEARful plans published by Speaker Hardware:

"The subwoofers require a low pass if you intend to use them with a fEARful. As a PA sub you don’t want the crossover."
​
AFAIK, the 12 Sub uses an approximate 850hz 2nd order LPF and he's talking about crossing them actively at 125hz.
 
#8
Wasnex said:
From the fEARful plans published by Speaker Hardware:

"The subwoofers require a low pass if you intend to use them with a fEARful. As a PA sub you don’t want the crossover."
​
AFAIK, the 12 Sub uses an approximate 850hz 2nd order LPF and he's talking about crossing them actively at 125hz.
Click to expand...

850Hz seems awfully high for a sub IMO.
 
  • Like
Reactions: HolmeBass, LowActionHero, bottomzone and 1 other person
#10
@agedhorse

As I understand, the OP has the following:

12/6/1 (Full CBG crosover including ~850hz LPF on woofer)
12 Sub (~850hz LPF)
12 Sub x 2 (no LPF)

He wants to use all four as subwoofers actively crossed over at 125hz.
 
#11
Wasnex said:
@agedhorse

As I understand, the OP has the following:

12/6/1 (Full CBG crosover including ~850hz LPF on woofer)
12 Sub (~850hz LPF)
12 Sub x 2 (no LPF)

He wants to use all four as subwoofers actively crossed over at 125hz.
Click to expand...

If they are really low passed at 850Hz, then there should be no issues low passing at 125Hz, but the whole thing like more of a pain than necessary.
 
  • Like
Reactions: bottomzone and Wasnex
#14
Do you know what slope the 125Hz crossover is in the amp? The only thing I'd be concerned with would be the series resistance of the passive crossover. Otherwise, the 125 LP would negate the driver from ever "seeing" the 850 passive LP.
 
  • Like
Reactions: agedhorse
#18
If the greenboys are crossed over at 850 hz, this is a non-issue. Bass cabs might cross over the low frequency driver that high, but PA subs are usually externally crossed over between 100 and 125 Hz or so.
 
#19
Jeroenslowend said:
24db/oct butterworth
Click to expand...
You might try the LR alignment, this results in constant power summing. It’s very similar to the BW alignment except for the corner frequency definition. It’s essentially an underlapped pair of BW HP/LP filters.
 

Latest posts

Top Bottom
Back