I wasn't disagreeing with you, just suggesting to Akiyama, that maybe alot of us here find the HPF a useful tool for live situations.
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I wasn't disagreeing with you, just suggesting to Akiyama, that maybe alot of us here find the HPF a useful tool for live situations.
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
You do realise this is the internet and that's not allowed?
My only concern with HPF/LPF is phase issues. No filtering/eq always sounds more natural (not to be confused with "better"/"brighter"/"wider"/"less muddy", etc.) than with filtering. But I guess music and especially sound of bass guitar from bass guitar amplification is always a compromise thing.
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
IME, filter phase for LPF’s and HPF’s is undetectable apart from the amplitude component of the filter action.
You have to remember that all filters (including eq, crossovers and speakers themselves) alter the phase versus frequency relationship of the signal, and in reasonable designs it’s inconsequential.
Asisde from compensating for room acoustics, is there a way of calculating the optimal hpf for a given speaker system?
I have typically been using two hpfs in my helix when using my frfr speaker - one hpf in each patch for speaker protection that's set at the -3dB point of my frfr speaker (53hz), and another variable hpf in the global eq that I adjust for the room (I just turn it up till it tightens up). However, the global eq is set to not affect the XLR out to FOH. FWIW each hpf in the Helix is -12dB, so, correct me if I'm wrong, using two in series essentially makes it -24dB
However, we added a sub to our PA in the last year or so and I no longer bring my frfr speaker to gig, so I'm now reconsidering my approach.
Our sub (EV ELX200-12SP) is rated at:
I read a JBL guide today that recommends setting the hpf to the frequency response of the speaker. It would appear that is what I had been doing to date. But I'm not sure if using two hpfs in series is doing more harm than good.
But I'm now thinking should I:
I have typically been using two hpfs in my helix when using my frfr speaker - one hpf in each patch for speaker protection that's set at the -3dB point of my frfr speaker (53hz), and another variable hpf in the global eq that I adjust for the room (I just turn it up till it tightens up). However, the global eq is set to not affect the XLR out to FOH. FWIW each hpf in the Helix is -12dB, so, correct me if I'm wrong, using two in series essentially makes it -24dB
However, we added a sub to our PA in the last year or so and I no longer bring my frfr speaker to gig, so I'm now reconsidering my approach.
Our sub (EV ELX200-12SP) is rated at:
- Frequency response (-3 dB) 49 Hz - 135 Hz
- Frequency range (-10 dB) 41 Hz - 165 Hz
- Frequency Response: 53 Hz – 20 kHz (+/- 3 dB)
- Frequency Range: 46 Hz – 22 kHz (-10 dB)
I read a JBL guide today that recommends setting the hpf to the frequency response of the speaker. It would appear that is what I had been doing to date. But I'm not sure if using two hpfs in series is doing more harm than good.
But I'm now thinking should I:
- Carry on as I have been and just set it for the response of the sub instead in my presets and use the global for my frfr in rehearsals.
- Set the presets hpf to the sub, and use the global eq hpf to optimise FOH
- Remove the hpfs from the presets and just use the global eq hpf for everything?
- Or is there something else I should consider?
That's what I would do...
Edit: ..unless you need different settings for each preset, of course...
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- Feb 12, 2006
- 60,951
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
There’s no universal answer, but note that cascading 2 HPF’s on the same signal path usually results in the HPF frequency shifting upward roughly 1/3-1/2 octave.
As a general rule, the best woofer protection occurs when the HPF is set to the -3dB frequency of the speaker’s response. That said, this may impact the low frequency response more than you like so as a compromise it’s still pretty effective set to the -6dB point.
It will still be somewhat effective set to the -10dB point, much better than nothing, but you will need to be a little more careful.
Note that some powered speakers contain internal processing (eq and HPF) that also address what’s happening at the bottom end and are more self protecting than a passive cabinet
As a general rule, the best woofer protection occurs when the HPF is set to the -3dB frequency of the speaker’s response. That said, this may impact the low frequency response more than you like so as a compromise it’s still pretty effective set to the -6dB point.
It will still be somewhat effective set to the -10dB point, much better than nothing, but you will need to be a little more careful.
Note that some powered speakers contain internal processing (eq and HPF) that also address what’s happening at the bottom end and are more self protecting than a passive cabinet
I’ve tried different HPF settings on my bass amp with similar results. Around the -3dB frequency it starts to attenuate too much low end but at the -6dB point the low end is still full but more controlled.
I have both the Broughton HPF/LPF and Resonant Filter Equalizer. With my pf50t I would like to use both pedals, the RFE allows resonant bumps for tone sculpting, while the HPF/LPF has gain control which is useful for getting extra stage volume. I am new to all this and hoping for suggestions on how to use this combination, and perhaps need to adjust the RFE to get back to the -3dB range?
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I can't speak to those pedals, but either Butterworth (my own personal preference) or Chebyshev (a little quirkier because of the need for ripple management) are the most common.
These filters are often the same circuit architecture, the difference being primarily the way the feedback is applied and how much. It's very much a bit of art and good judgement/experience along with the science.
If you know the speaker's resonant frequency, would it make sense to configure a second order Sallen-Key hpf with a Butterworth slope, and a cutoff frequency set to the speaker's resonant frequency? Objectives are power efficiency and speaker protection from too much power and excursion, but without sacrificing (too much) audible low end.
I'd swear I've seen you post something along these lines on this forum (perhaps in this thread). I did browse the first few and last few pages of this thread, but didn't have the courage to visit the no man's posts in between.
Found it, on this very page (Homer Simpson sounds).
No mention of speaker resonant frequency however. How does one proceed without a frequency response for the speaker? What I do know is resonant frequency (29Hz) and frequency response 40Hz-4Khz.
And yes, this woofer is going into you know which wee combo.
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- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
There’s nowhere enough technical
information in that driver to know anything about how it will perform in any specific enclosure.
The driver AS IT PERFORMS IN THE ENCLOSURE is what determines the best choices for HPF frequency. The same driver can have a range of HPF frequencies depending on the enclosure. The resonant frequency of the driver is quite meaningless by itself.
That driver is rather dreadful for bass guitar based on the meager specs provided, and may be worse once the details are parsed out of extracted TS parameters.
information in that driver to know anything about how it will perform in any specific enclosure.
The driver AS IT PERFORMS IN THE ENCLOSURE is what determines the best choices for HPF frequency. The same driver can have a range of HPF frequencies depending on the enclosure. The resonant frequency of the driver is quite meaningless by itself.
That driver is rather dreadful for bass guitar based on the meager specs provided, and may be worse once the details are parsed out of extracted TS parameters.
Both of mine are Butterworth. Schematics are available, likewise for a few other designs out there. The most common arrangement is Sallen-Key with feedback gain chosen to set the Q factor for the desired response shape. In most of these designs (like with speakers), the "named" curves such as Butterworth and Bessel are specific points along a continuous variation.
This seems like a decent tutorial:
Link Removed
About finding the resonance, the "top of the knee" in the response curve will get you close enough.
Something I've learned about speaker drivers is that if the vendor doesn't offer a fairly complete set of specs, with units of measure, then they probably don't know what it is that they're selling. Designing with components that don't have a credible chain of evidence for their specs tends to give any engineer with a sense of fiduciary responsibility a severe case of the heebie-jeebies. This is true for a lot of components and assemblies sold through the popular e-commerce sites.
