The actual constructed physical length should be 20.00 cm, and that is also the value that should be specified for Lpt in Hornresp when doing the simulations.
(If the port tube length is specified using Lpt then the 3.46 cm internal end correction is automatically added during the simulation calculations. Note that the end correction value used assumes that the port tube is cylindrical).
No I do not.
(Perhaps try a Google search to see if one exists).
If you are using one of the four horn segments available in Hornresp (assume segment 3) to specify the rectangular port tube, then no internal end correction will be automatically added during the simulation calculations. Ideally in this case the value that you specify for L34 should be the actual constructed physical length plus an internal end correction appropriate for the rectangular port.
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Lp and Ap?
Can someone give me an understanding of these parameters in Hornresp? I understand that it applies to ports?
Can someone give me an understanding of these parameters in Hornresp? I understand that it applies to ports?
Port length (Lpt in cm) and port cross section surface (Ap in cm2).
Ap = Nd BR or TL port cross section area.
Lpt = Nd BR or TL port length.
Ap = TH/TQWP/T-TQWT rear chamber CSA.
Lpt = TH/TQWT/T-TQWP rear chamber port length.
Ap = Stepped TH/TQWP/T-TQWT rear chamber CSA.
Lpt = Stepped TH/TQWT/T-TQWP rear chamber port length.
Ap = Closed mouth Nd BP4 vented rear chamber port CSA.
Lpt = Closed mouth Nd BP4 vented rear chamber port length.
Ap = OD PPSL vented rear chamber port CSA.
Lpt = OD PPSL vented rear chamber port length.
Ap = OD BP6P vented rear chamber port CSA.
Lpt = OD BP6P vented rear chamber port length.
Ap = Stepped Nd BP6P vented rear chamber port CSA.
Lpt = Stepped Nd BP6P vented rear chamber port length.
Ap = Stepped OD BP6P vented rear chamber port CSA.
Lpt = Stepped OD BP6P vented rear chamber port length.
Lpt = Nd BR or TL port length.
Ap = TH/TQWP/T-TQWT rear chamber CSA.
Lpt = TH/TQWT/T-TQWP rear chamber port length.
Ap = Stepped TH/TQWP/T-TQWT rear chamber CSA.
Lpt = Stepped TH/TQWT/T-TQWP rear chamber port length.
Ap = Closed mouth Nd BP4 vented rear chamber port CSA.
Lpt = Closed mouth Nd BP4 vented rear chamber port length.
Ap = OD PPSL vented rear chamber port CSA.
Lpt = OD PPSL vented rear chamber port length.
Ap = OD BP6P vented rear chamber port CSA.
Lpt = OD BP6P vented rear chamber port length.
Ap = Stepped Nd BP6P vented rear chamber port CSA.
Lpt = Stepped Nd BP6P vented rear chamber port length.
Ap = Stepped OD BP6P vented rear chamber port CSA.
Lpt = Stepped OD BP6P vented rear chamber port length.
Just to clarify...
Ap = TH/TQWP/T-TQWT rear chamber port CSA.
Ap = Stepped TH/TQWP/T-TQWT rear chamber port CSA.
Ap = TH/TQWP/T-TQWT rear chamber port CSA.
Ap = Stepped TH/TQWP/T-TQWT rear chamber port CSA.
Thanks guy! I thought I corrected them all. You know stuff starts looking the same after a few times.
Found a bug, found a bug! found a bug! (running away giggling, like a toddler). But it feels like a negative dejavu.
In my compact ported design, I Put RCF LF18X451 into 96l box, once tuned at 39Hz, once at 30Hz.
Set Input voltage Rg in order to match the SPL exactly at 40Hz point to be equal between the two designs.
The higher tuned model shows more power draw at port tuning frequency (40Hz checkpoint) than the 30Hz tuned design at 40Hz, because the 30Hz tuned box now at 40Hz operates closer to the impedance peak.
That should mean that at exactly 40Hz, the 30Hz design is more efficient. Same SPL, less input, means more efficiency. Yet when I pull out the efficiency graph, the 40Hz design is showed more efficient at 40Hz.
While making printscreens, uh, oh, something slowly comes to me. But great find anyways. Is this some kind of discrepancy between apparent power and real power? Some forgotten cosFi correction?
At 40Hz, the 30Hz tuned design with less power input at 40Hz loses to 40Hz design with same SPL.
Now what to make of it....
In my compact ported design, I Put RCF LF18X451 into 96l box, once tuned at 39Hz, once at 30Hz.
Set Input voltage Rg in order to match the SPL exactly at 40Hz point to be equal between the two designs.
The higher tuned model shows more power draw at port tuning frequency (40Hz checkpoint) than the 30Hz tuned design at 40Hz, because the 30Hz tuned box now at 40Hz operates closer to the impedance peak.
That should mean that at exactly 40Hz, the 30Hz design is more efficient. Same SPL, less input, means more efficiency. Yet when I pull out the efficiency graph, the 40Hz design is showed more efficient at 40Hz.
While making printscreens, uh, oh, something slowly comes to me. But great find anyways. Is this some kind of discrepancy between apparent power and real power? Some forgotten cosFi correction?
At 40Hz, the 30Hz tuned design with less power input at 40Hz loses to 40Hz design with same SPL.
Now what to make of it....
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Hi Crashpc,
Many thanks for the feedback - tests done by users to check the validity of the Hornresp simulation models are always most welcome.
The results of your tests show that a system tuned to 40 Hz has a greater power conversion efficiency at the resonant frequency of 40 Hz than does a system tuned to 30 Hz but operating at 40 Hz. This is entirely logical and as expected.
Because of the differences in port sizes and port radiation impedances, individual power outputs will be different for each system, and the phase differences between the two output volume velocities being combined will also be different for each system. Adjusting the Eg input value to make the combined response SPL levels effectively identical for two different multiple output systems does not mean however that the two systems will have the same total acoustic power outputs.
The screenprint below shows the results at 40 Hz for the system tuned to 40 Hz.
The screenprint below shows the results at 40 Hz for the system tuned to 30 Hz.
The results for the above two systems are as expected.
Kind regards,
David
Hello and thank you for your kind response.
I'm very boneheaded though and this response does not clear the discrepancy I have on my mind.
We have two designs, which at 40Hz provide same SPL. Or the one tuned lower shows tad more SPL even. This system showing more SPL needs nearly 500Watts less power to reach the SPL which in my book means greater power conversion efficiency, yet it outputs less accoustical watts and is less efficient?
What am I missing?
Many thanks.
I'm very boneheaded though and this response does not clear the discrepancy I have on my mind.
We have two designs, which at 40Hz provide same SPL. Or the one tuned lower shows tad more SPL even. This system showing more SPL needs nearly 500Watts less power to reach the SPL which in my book means greater power conversion efficiency, yet it outputs less accoustical watts and is less efficient?
What am I missing?
Many thanks.
It slowly crawls under my skin, but gets tough to make out much from it. I mean, how come that so much different acoustical power all else being equal, creates equal sound pressure level. How should we interpret the efficiency, when we get more SPL for less power? It looks like it is not the efficiency we want to work with.
Half the acoustical power creating same SPL in the same system is too erratic. Would it be possible to implement Power/SPL plots also?
Half the acoustical power creating same SPL in the same system is too erratic. Would it be possible to implement Power/SPL plots also?
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In effect you are assuming that if one loudspeaker system has a higher efficiency than another, then it must also have a higher sensitivity. As your test examples have shown however, this is not always necessarily the case - particularly for bass-reflex systems where two output signals with different levels and phase, are being combined.
At a frequency of 40 Hz your 40 Hz system has the higher efficiency, but the 30 Hz system has the higher sensitivity.
The information at the webpage linked below may be of interest:
https://pikip-solarspeakers.com/en/articles/efficiency-sensitivity-acoustic-definition
A Pin / SPL plot would serve little practical purpose. It is already possible to generate one manually however if for some reason you wish to view it. Export all chart data and plot the desired values in Excel or similar, as shown for your 40 Hz example below.
I´m afraid we need more precise wording here.
To date, I believe we thought of sensitivity as volts/decibels ratio in frequency. With efficiency, we thought of Input power versus SPL ratio.
In that realm, the 30Hz design is supposed to be more efficient, as it outptus more decibels per input power in Watts, or same decibels for less power, than 40Hz design. Therefore is is more efficient. That was the kind of efficiency I thought of. And to date I thought everybody was on the same boat. But I might be greatly mistaken.
Either you still missed that, or you are really mathing plain energies and different kind of effficiency (power input versus power output, which is NOT in decibels), which can end up with different results, as graph ignores phenomena like directivity and phase relations indeed, as it doesn´t care about outcomes of the radiation or signal reception. And so less directive or self canceling system can produce less SPL but more output power. at the same input being more efficient.
I get that.
This link you provided nudges me to think that we misunderstood each other. The sensitivity/efficiency relations are given and understood. That is different that calling 132,6dB 2024Watt system more efficient than 132,6db 1500W system. I hope now you can see where I am pointing at.
That all raises the question how come that in-tuning 40Hz port that should also be in-phase with the cone at 40Hz, all giving more acoustical power, somehow cancels out to produce same SPL at more power or less SPL than a port that is only assisting at 40Hz while tuned at 30Hz, being out of phase at 40Hz. It does not add up. But I can see how it is another problem, a case problem, so let´s not get this one mingled with the rest.
So is it the case to reiterate it into question, that if I imagine a 99% self canceling device, it can still show to be more efficient on the graph?
Then I wonder what is the use of such graph. Not in a criticizing way. I thought I had the idea, now I don´t. I would think that Power input versus SPL is of high value, and given the news, I don´t see the value of the current situation. Knowing the relation between power and SPL, and also power/SPL expressed in percent even though being different kind of efficiency, seems to be like a piece of information to not be omitted. Very important for a design. Vital even But I digress - it is a great learning moment for me. Though going into excel really hurts.
Many thanks.
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Not sure what you mean by "we", but I have certainly never thought that.
At a given frequency:
Sensitivity is the SPL at a given distance (originally 1 metre) for a given reference power (originally 1 watt), expressed in decibels.
Power conversion efficiency is the ratio of acoustical output power to electrical input power, expressed a percentage.
Indeed you are. Google "loudspeaker sensitivity vs efficiency" to learn more.
Once again, Google is your friend.
Just to be clear - I am confident that there is no bug in Hornresp.
The two outputs are not in phase at the Helmholtz resonance frequency.
This. My mistake of not going to the point maybe.
The system, that is tuned to work in-phase at 40Hz producing 59,65Watts of output power with 2024Watts of input power is producing 132,6dB SPL.
Why would out of phase system producing 29,68Watts, half of that 59,65W be as loud? Sincerely learning here. Asking help anyone.
//Edit
Ouch! Now that is the learning point I was looking for then. Many thanks.
Well phrased. So much slippery games being played with this now. 2.83 volts for everything as an example. There's always someone trying to play games with the truth!