I've always tuned my PA systems by ear, with decent results, but have recently decided to get more serious about it.
I bought True Audio's "TrueRTA" software (the 24 band per octave version) and am using very high-end studio omni mic and audio hardware.
So all good, but I'm having a hard time getting smooth results. Granted, I'm currently setup in a large room (using low volume to minimize nodes, etc) but am only going for a rough tweaking. Afterwards I'll do the fine-tuning outdoors.
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But I digress.
I'm setting up both 18" sealed subs,, and dual 12" ported subs, paired with EAW KF394 tops which have their HPF factory set to about 65 Hz. (That seems low to me, but that's what it is.) I'm not sure what filter TYPE they use, as it's part of the EAW "Greybox" setting. - I could probably find out, if it matters.
My question is as in the title.
I use an EAW UX3600 processor, so I have a lot of control options.
So specifically:
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HPF: Some experts have recommended 24 dB BW at maybe 5-6 Hz below the Fb, but another (A very good tech from one of the driver manufacturers) recommended a 12 dB but a little higher frequency, (closer to the box tuning) and he did not mentioned filter type.
It seems to me the 24 dB would offer more protection, though 12 dB might make sense with the 2X12" box, since the LF extension is somewhat compromised. (Fb is 43 Hz)
LPF: I've read lots of threads on lots of forums, but there's isn't a clear consensus. Folks seem equally divided between BW and L-R, though Ivan Beaver (Danley) seems to be fond of Bessel. BW seems to be the flattest, so I'm surprised it's not the clear winner.
- And slope recommendations are all over the place. Many even recommend over or underlapping at the transition point. I know it ultimately comes down to using my ears, but ughhh ......
LF Compensation: This is the one that puzzles me the most. Is it common to use a shelf filter, so as to get a very smooth result? It seems to me that this would then sort of "fight" the subs' HPF, and maybe cause phase issues? But a bell-type is really hard to dial-in.
If I use a bell-type then should I experiment with a tight Q close to 40 Hz, or a wide Q set a little higher?
-----------------------------
One last question: Is it typically recommended to go for a "roughly flat" response in the 40 Hz area, or do some guys prefer a small bump? (Same question for 80 Hz.)
If it matters, I use these rigs for both a rock band and DJ playback.
Thx.
I bought True Audio's "TrueRTA" software (the 24 band per octave version) and am using very high-end studio omni mic and audio hardware.
So all good, but I'm having a hard time getting smooth results. Granted, I'm currently setup in a large room (using low volume to minimize nodes, etc) but am only going for a rough tweaking. Afterwards I'll do the fine-tuning outdoors.
---------------------------------------------
But I digress.
I'm setting up both 18" sealed subs,, and dual 12" ported subs, paired with EAW KF394 tops which have their HPF factory set to about 65 Hz. (That seems low to me, but that's what it is.) I'm not sure what filter TYPE they use, as it's part of the EAW "Greybox" setting. - I could probably find out, if it matters.
My question is as in the title.
I use an EAW UX3600 processor, so I have a lot of control options.
So specifically:
----------------------------------------------
HPF: Some experts have recommended 24 dB BW at maybe 5-6 Hz below the Fb, but another (A very good tech from one of the driver manufacturers) recommended a 12 dB but a little higher frequency, (closer to the box tuning) and he did not mentioned filter type.
It seems to me the 24 dB would offer more protection, though 12 dB might make sense with the 2X12" box, since the LF extension is somewhat compromised. (Fb is 43 Hz)
LPF: I've read lots of threads on lots of forums, but there's isn't a clear consensus. Folks seem equally divided between BW and L-R, though Ivan Beaver (Danley) seems to be fond of Bessel. BW seems to be the flattest, so I'm surprised it's not the clear winner.
- And slope recommendations are all over the place. Many even recommend over or underlapping at the transition point. I know it ultimately comes down to using my ears, but ughhh ......
LF Compensation: This is the one that puzzles me the most. Is it common to use a shelf filter, so as to get a very smooth result? It seems to me that this would then sort of "fight" the subs' HPF, and maybe cause phase issues? But a bell-type is really hard to dial-in.
If I use a bell-type then should I experiment with a tight Q close to 40 Hz, or a wide Q set a little higher?
-----------------------------
One last question: Is it typically recommended to go for a "roughly flat" response in the 40 Hz area, or do some guys prefer a small bump? (Same question for 80 Hz.)
If it matters, I use these rigs for both a rock band and DJ playback.
Thx.
Hi, never heard back from you after I left a phone message returning your call 9/10/21.
Sounds like you finished the 12" subs!
There won’t be a “consensus” about what type of filters to use, as cabinet response, room response, output target frequency, phase response and level are all case dependent for each particular alignment.
Since the response of a ported cabinet drops steeply below Fb (around 24dB per octave is typical) as the port output rapidly becomes out of phase with the driver’s output, a steep cut below Fb is advisable to reduce useless power expenditure and excursion for little output gain.
A BW has a steeper “knee” at the crossover frequency (-3dB compared to -6dB for LR), so is often used for the HPF to allow the maximum output to the lowest frequency with the least sonic compromise.
As I recall, you don’t like harmonic distortion, so I’d recommend a BW24 HPF within 1/3 octave below Fb for the 12”.
Since excursion quadruples for each octave lower to achieve equal output in a sealed sub, and the Bag End 18” have little excursion, you may want to use the similar HPF for them to maximize output. Otherwise, you could do what Bag End does, and progressively limit gain as frequency lowers to keep excursion in check.
For the LPF, the acoustic response of both sub and mains must be considered, there is no type of named crossover that is “best” for all.
The EAW KF394 impedance specs “complete” indicate it’s Fb at 60Hz, the “LF” 70Hz, curious.
The processed (free space) response rolls off sharply below 80Hz, about -6dB at 70Hz, and -30dB at 40Hz, which looks like a 80Hz LR24 filter may be used along with a narrow +10dB boost around 80Hz to compensate for the falling unprocessed response.
The “trick” to aligning the top to the sub(s) is alignment of the time and phase response at the crossover frequency, if they are within 60 degrees of phase alignment through the crossover region, they will sum well.
The phase (mislabeled “SPL” on the Phase Linearity chart) of the KF394 goes through 540 degrees of shift between 45 and 600 Hz..
Since the sealed Bag End 18” subs will each have a different phase and frequency response from the KF394- what works to align one won’t be optimum for the other.
Phase alignment will be also be dependent on the positioning of the cabinets relative to each other, as well as response you choose- flat response through the crossover region or the “haystack” bass boost commonly employed .
The alignment process is far easier if you can see the phase response, REW (freeware) has that function, doesn’t look like TrueRTA does.
Merlijn Van Veen has covered the alignment process in great detail, check it out:
https://www.merlijnvanveen.nl/en/st...gnment-the-foolproof-relative-absolute-method
Art
Sounds like you finished the 12" subs!
There won’t be a “consensus” about what type of filters to use, as cabinet response, room response, output target frequency, phase response and level are all case dependent for each particular alignment.
Since the response of a ported cabinet drops steeply below Fb (around 24dB per octave is typical) as the port output rapidly becomes out of phase with the driver’s output, a steep cut below Fb is advisable to reduce useless power expenditure and excursion for little output gain.
A BW has a steeper “knee” at the crossover frequency (-3dB compared to -6dB for LR), so is often used for the HPF to allow the maximum output to the lowest frequency with the least sonic compromise.
As I recall, you don’t like harmonic distortion, so I’d recommend a BW24 HPF within 1/3 octave below Fb for the 12”.
Since excursion quadruples for each octave lower to achieve equal output in a sealed sub, and the Bag End 18” have little excursion, you may want to use the similar HPF for them to maximize output. Otherwise, you could do what Bag End does, and progressively limit gain as frequency lowers to keep excursion in check.
For the LPF, the acoustic response of both sub and mains must be considered, there is no type of named crossover that is “best” for all.
The EAW KF394 impedance specs “complete” indicate it’s Fb at 60Hz, the “LF” 70Hz, curious.
The processed (free space) response rolls off sharply below 80Hz, about -6dB at 70Hz, and -30dB at 40Hz, which looks like a 80Hz LR24 filter may be used along with a narrow +10dB boost around 80Hz to compensate for the falling unprocessed response.
The “trick” to aligning the top to the sub(s) is alignment of the time and phase response at the crossover frequency, if they are within 60 degrees of phase alignment through the crossover region, they will sum well.
The phase (mislabeled “SPL” on the Phase Linearity chart) of the KF394 goes through 540 degrees of shift between 45 and 600 Hz..
Since the sealed Bag End 18” subs will each have a different phase and frequency response from the KF394- what works to align one won’t be optimum for the other.
Phase alignment will be also be dependent on the positioning of the cabinets relative to each other, as well as response you choose- flat response through the crossover region or the “haystack” bass boost commonly employed .
The alignment process is far easier if you can see the phase response, REW (freeware) has that function, doesn’t look like TrueRTA does.
Merlijn Van Veen has covered the alignment process in great detail, check it out:
https://www.merlijnvanveen.nl/en/st...gnment-the-foolproof-relative-absolute-method
Art
Great stuff, Art. THANKS.
Re the KF's HPF, I tried my own settings without greybox, and you were right: 24dB/oct L-R at 80 Hz, with a small boost pretty much nails what they show on that graph. - Though I think the boost is closer to 90Hz. (I could be wrong, as I'm pretty new to this.)
I need to do a lot of reading / thinking about the phase issues. This kinda of scares / frustrates me a bit.
- But doesn't that whole issue kind of suggest using the steepest filters possible, to minimize interaction between the tops and subs? For instance, I the EAW processor goes as high as 36 dB/oct. Would ringing then be an issue?
Re the KF's HPF, I tried my own settings without greybox, and you were right: 24dB/oct L-R at 80 Hz, with a small boost pretty much nails what they show on that graph. - Though I think the boost is closer to 90Hz. (I could be wrong, as I'm pretty new to this.)
I need to do a lot of reading / thinking about the phase issues. This kinda of scares / frustrates me a bit.
- But doesn't that whole issue kind of suggest using the steepest filters possible, to minimize interaction between the tops and subs? For instance, I the EAW processor goes as high as 36 dB/oct. Would ringing then be an issue?
Before you get too frustrated, keep in mind that phase and time can only be aligned for one specific location if the cabinets are not all within 1/4 wavelength at the crossover frequency, pretty much impossible when you have 6 subs and two stereo mains.
Some claim ringing is an issue, though compared to room, location and phase alignment/cancellation issues, pretty benign.
Most "phase issues" are heard as peaks or cancellations, the steeper the slope, the lesser the frequency range phase alignment affects amplitude response.
That said, after individually applying PEQ to smooth response within the crossover pass bands of the individual cabinets, 24dB/octave seems adequate, while 12 or even 18 aren't quite enough when the distance between cabinets is large relative to wavelength.
Art