Your box resonance is 60Hz-ish, there is no way you can EQ to 20Hz, you will have too much gain and the system will be full of hum and unstable, not to mention will only be able to attain quiet listening levels at best.
A true 40Hz response is surprisingly deep for music, I suggest you aim for that with your drive unit and box combination.
A true 40Hz response is surprisingly deep for music, I suggest you aim for that with your drive unit and box combination.
I had noted this on the very day you advised me. I tried to understand why so.
what I found is this is called as bassel alignment (Q =0.577) here we get linearity in group delays. This has bigger box volume. Bigger box volume means lower F3. Lower f3 means lesser gain with LT. so the above is better over Q= 0.7. did I understand it right ? any point missing? The only problem I see is larger enclosure size.
About selecting F3 of 20Hz, I belive that If i can drive it safely to low as 20Hz I can easily make it for 30Hz or 40Hz, so currently I am calculating @ 20Hz. as we already said first lets experiment with different Q and F3.
My final design which I would assemble would be designed around 30Hz or 40Hz. I am not overhearing your advice.
Also the output of LT is Inverted. It needs a one inverted unity gain output stage. right?
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Yes thanks, I understand you are right... I have put my thought process in above post.
Hi Andrew,
Yes, The above excursion is with both the filters ticked.
I just thought to experiment LT with vented system. The thought was if i can achieve it at lower gain of LT. the other thought was vented as a basic design has 3db gain. so broadly speaking vented gives double (+3db) output with the same rating woofer. 3db gain is like using other woofer delivering same wattage. but frankly this was a thought that stuck me, and trying to do it using tool don't cost much.
To make it easy I just manipulate the crossover points to get control over excursion and to get best possible F3.
I am posting the Graph for LT gain , HPF and Power Graph.
Yes, The above excursion is with both the filters ticked.
I just thought to experiment LT with vented system. The thought was if i can achieve it at lower gain of LT. the other thought was vented as a basic design has 3db gain. so broadly speaking vented gives double (+3db) output with the same rating woofer. 3db gain is like using other woofer delivering same wattage. but frankly this was a thought that stuck me, and trying to do it using tool don't cost much.
To make it easy I just manipulate the crossover points to get control over excursion and to get best possible F3.
I am posting the Graph for LT gain , HPF and Power Graph.
I don't understand the 4th plot: maximum power.
The LT has +9dB @ 20Hz, +5dB @ 32Hz, +1.5dB @ 50Hz and ~+0dB @ 100 & 200Hz. With the high pass added, the 20Hz drops by ~ 1dB to +8dB
Can you tell me at what frequency is 125W delivered to the speaker? What is the power sent at other frequencies when that 125W value is sent?
or does the original 125W graph show the excursion at 125W for all frequencies?
The LT has +9dB @ 20Hz, +5dB @ 32Hz, +1.5dB @ 50Hz and ~+0dB @ 100 & 200Hz. With the high pass added, the 20Hz drops by ~ 1dB to +8dB
Can you tell me at what frequency is 125W delivered to the speaker? What is the power sent at other frequencies when that 125W value is sent?
or does the original 125W graph show the excursion at 125W for all frequencies?
Look at that max power thing... I have put a compare graph its when done same EQd + HPF for both Vented and Sealed system. yellow is for sealed
don't know, but, is it something like its delivering better power when the LT stuff done with Vented? I mean we get benefit of Power as well getting the F3 down to 30 ?
Or I am just missing something ?
don't know, but, is it something like its delivering better power when the LT stuff done with Vented? I mean we get benefit of Power as well getting the F3 down to 30 ?
Or I am just missing something ?
Well, What I understand is, that the graph shows the max wattage that can be handled Vs frequency. So reading the graph, I can say that the system can deliver 125 Watts from 51Hz to 30Hz and from 56Hz and above. between 51Hz to 56Hz the system can handle 120W.
Hope i have understood your question correctly and answered it.
Hi,
FWIW if experimenting with vented boxes don't use a LT.
Instead use a peaking 2nd order high pass filter for a 6th order response.
This should be an overdamped alignment say 6th order Bessel, Butterworth
would sound pretty dreadful. the lowest pole will be the 2nd order hp filter,
and making the Q of this adjustable makes for a relatively flexible system.
e.g. for a typical driver compared to Butterworth vented:
Somewhat increase box volume and detune the port for maximum F-12dB.
The hp filter is tuned lower than the port with maximum gain near Fport.
Use the filter to get back some gain but not all, count on room gain.
This will work better than an LT, with far better control of excursion.
rgds, sreten.
FWIW if experimenting with vented boxes don't use a LT.
Instead use a peaking 2nd order high pass filter for a 6th order response.
This should be an overdamped alignment say 6th order Bessel, Butterworth
would sound pretty dreadful. the lowest pole will be the 2nd order hp filter,
and making the Q of this adjustable makes for a relatively flexible system.
e.g. for a typical driver compared to Butterworth vented:
Somewhat increase box volume and detune the port for maximum F-12dB.
The hp filter is tuned lower than the port with maximum gain near Fport.
Use the filter to get back some gain but not all, count on room gain.
This will work better than an LT, with far better control of excursion.
rgds, sreten.
Robert Bullock covers this in "Bullock on Boxes" chapter 9, very well.
Easy to understand and to implement.
It allows maximum bass extension combined with maximum bass Power, without destroying the driver. That's the most important part "without destroying the driver".
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I was expecting what you said, but then what are the ticked options, LT and High Pass, doing that is different?
Probably I haven't put the thing properly. Let me try again.
The way enclosure is designed changes MaxPower handling. No electronic equalization should change this. but electronic can be used to limit excursion in safe limit and to obtain desired F3.
As Serten said, the way I got it done is wrong. LT is not recommended here. but as vented system can handle the full power at much lower frequency than Sealed , then with the help of electronic correction we can attain lower F3,
Example.
In the above PDF ( Power.pdf) we see rapid fall below 30Hz. So we can design system where F3 at 28 Hz ( cause I see half power here as per graph). as there is not much difference between 28Hz and 30Hz. we tune it to 30Hz as F3 point with the help of electronics.
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Getting late into this thread... much earlier on there was discussion on LF energy <50Hz and <20Hz. I don't have figures, but I can recommend a particular recording that might push such a system to its limits.
I'm presently playing around with a 3-way active speaker. Very roughly thrown together into an existing 28 litre box is an ApexJr Super8 8"woofer with not much of a pedigree. It has LF EQ that peaks around 12dB at 20Hz to bring F3 down from about 50Hz to 25Hz. It is driven by a 70W amplifier. Playing the first track of Jean-Michel Jarre's Aero CD made the amplifier trip its overload circuitry. None of the many other tracks I played did this.
HTH
I'm presently playing around with a 3-way active speaker. Very roughly thrown together into an existing 28 litre box is an ApexJr Super8 8"woofer with not much of a pedigree. It has LF EQ that peaks around 12dB at 20Hz to bring F3 down from about 50Hz to 25Hz. It is driven by a 70W amplifier. Playing the first track of Jean-Michel Jarre's Aero CD made the amplifier trip its overload circuitry. None of the many other tracks I played did this.
An externally hosted image should be here but it was not working when we last tested it.
HTH
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