Hi there,
This was touched on in another thread, and I've also read the Hornresp Help file on this. But I'm afraid I can't quite understand exactly what is being presented and why.
The understanding I have so far indicates that it shows the maximum SPL against frequency that my design is capable of, and what is limting it from going any further.
So as far as I can tell, either the realistic maximum SPL is a line that follows the troughs (low SPL points).. Or that at the maximum wattage and Xmax, the response shape that is shown occurs, because of the various and uneven limitations.
Also, do I need to know about amp current and voltages to effectively use the tool? So far I've been using what I know, which is driver rms/program or peak wattage and Xmax.
I've attached an image of two competing design's Max SPL windows. Could you describe how they compare- particularly what SPL each design is capable of reaching, and why this is so.
Thank you
This was touched on in another thread, and I've also read the Hornresp Help file on this. But I'm afraid I can't quite understand exactly what is being presented and why.
The understanding I have so far indicates that it shows the maximum SPL against frequency that my design is capable of, and what is limting it from going any further.
So as far as I can tell, either the realistic maximum SPL is a line that follows the troughs (low SPL points).. Or that at the maximum wattage and Xmax, the response shape that is shown occurs, because of the various and uneven limitations.
Also, do I need to know about amp current and voltages to effectively use the tool? So far I've been using what I know, which is driver rms/program or peak wattage and Xmax.
I've attached an image of two competing design's Max SPL windows. Could you describe how they compare- particularly what SPL each design is capable of reaching, and why this is so.
Thank you
The Max.SPL tool shows how loud the speaker will get at each frequency, given the limits you've entered. ie, a maximum SPL will be reached when either the driver runs out of excursion, or the maximum power input has been reached.
I tend not to use the "maximum power" option, because the input power is heavily dependent on impedance. ie, if the speaker's impedance goes from 4ohm to 20ohm, then the applied voltage (in order to maintain a consistent power input: P=(V^2)/R ) will vary hugely. PA amps are voltage sources, which apply a voltage and allow current to flow.
As a result, I use a combination of maximum voltage (based on my intended amplifiers) and excursion.
Looking at your graphs, when we apply a protective highpass filter and look at the limitations within the passband, I'd say the first design will hit 118dB, and the second about 128dB, assuming your amplifier is capable of getting the drivers there. At some frequencies, the speakers will get louder than those numbers, but that's a guaranteed "they'll hit that SPL at any frequency in the passband" rating, which is something I'd prefer.
You might find this useful: https://www.prosoundweb.com/spec-wars-looking-inside-loudspeaker-spl-specifications/
I wrote it out of frustration at the games the marketing departments play in the PA world.
Chris
I tend not to use the "maximum power" option, because the input power is heavily dependent on impedance. ie, if the speaker's impedance goes from 4ohm to 20ohm, then the applied voltage (in order to maintain a consistent power input: P=(V^2)/R ) will vary hugely. PA amps are voltage sources, which apply a voltage and allow current to flow.
As a result, I use a combination of maximum voltage (based on my intended amplifiers) and excursion.
Looking at your graphs, when we apply a protective highpass filter and look at the limitations within the passband, I'd say the first design will hit 118dB, and the second about 128dB, assuming your amplifier is capable of getting the drivers there. At some frequencies, the speakers will get louder than those numbers, but that's a guaranteed "they'll hit that SPL at any frequency in the passband" rating, which is something I'd prefer.
You might find this useful: https://www.prosoundweb.com/spec-wars-looking-inside-loudspeaker-spl-specifications/
I wrote it out of frustration at the games the marketing departments play in the PA world.
Chris
Not sure how you derived those two figures, but if true that would be gravely disappointing.
the boxes are about 102-103 db efficient, so I’m pretty sure we’re looking at over 130 in each case.
unless your 118 and 128 figures were adjusted too RMS?
But anyway, thanks for the reply.
Based on what you are saying, I've drawn a green line on the graphs which is what I'm guessing is what horn resp is indicating is the maximum SPL my design can generate, before it runs into limitations.
Am I correct?
Thank you
Based on what you are saying, I've drawn a green line on the graphs which is what I'm guessing is what horn resp is indicating is the maximum SPL my design can generate, before it runs into limitations.
Am I correct?
Thank you
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Ah, I see now how you came up with the 118 and 128dB readings. You've read the bottom most (lowest frequency) amplifier power limitation.
As far as I can tell, usually what is quoted is either a mean point accross the usable bandwidth of the speaker (in this case I'd say 128 and 132 respectively -I am using approximately 40 - 140hz of the graphs). But most often just a peak figure, with varying degrees of relevance, depending on how honest the maufacturer is willing to be. In that case I think we are looking at something like 133dB @ 130hz and 138dB @ 120hz.
But I'm guessing if you were looking at this from a Hifi/Home Theatre perspective, the low end of the response is what you'd home in on. I didn't say, these two are for live sound reinforcement.. And 100-140hz is very relevant.
As far as I can tell, usually what is quoted is either a mean point accross the usable bandwidth of the speaker (in this case I'd say 128 and 132 respectively -I am using approximately 40 - 140hz of the graphs). But most often just a peak figure, with varying degrees of relevance, depending on how honest the maufacturer is willing to be. In that case I think we are looking at something like 133dB @ 130hz and 138dB @ 120hz.
But I'm guessing if you were looking at this from a Hifi/Home Theatre perspective, the low end of the response is what you'd home in on. I didn't say, these two are for live sound reinforcement.. And 100-140hz is very relevant.
It'll almost certainly be excursion rather than amp power limited in those dips, but yes, you've got where Chris is coming from - take the lowest in-band dip as the number to keep in mind.
The thing is, if you take the 128dB figure from the 90Hz region in pic 1, and size your rig based on that, what happens when you get program material with strong 40-50Hz content?
Either it simply won't go anywhere near 128dB, as we already know (if it's a really good well behaved driver), or it'll get somewhere close but with extreme amounts of distortion from pushing the driver well past Xmax if it's any other driver.
Neither does you any favours as a PA operator, hence the preference for assessing the design based on more of a worst case scenario.
HTH,
David.
The thing is, if you take the 128dB figure from the 90Hz region in pic 1, and size your rig based on that, what happens when you get program material with strong 40-50Hz content?
Either it simply won't go anywhere near 128dB, as we already know (if it's a really good well behaved driver), or it'll get somewhere close but with extreme amounts of distortion from pushing the driver well past Xmax if it's any other driver.
Neither does you any favours as a PA operator, hence the preference for assessing the design based on more of a worst case scenario.
HTH,
David.
I actually have a fair amount of experience with live events.
The 40-50hz region is definitely strong enough.
it’s difficult to explain, but your average live subwoofer is tuned to about 40hz @-3. Yet with a 5 string bass, the lowest notes are well outside of that range. But with a sub tuned much higher than that, these infra bass notes are still s
The reason is, a 30hz tuned single 18 sub is just too rumbly and indistinct. And even one tuned to 38hz might struggle for punch.
So the tuning is intentional. I was more hoping to get a definite understanding of what the Max SPL window is displaying, and what it’s used for.
thanks
The 40-50hz region is definitely strong enough.
it’s difficult to explain, but your average live subwoofer is tuned to about 40hz @-3. Yet with a 5 string bass, the lowest notes are well outside of that range. But with a sub tuned much higher than that, these infra bass notes are still s
The reason is, a 30hz tuned single 18 sub is just too rumbly and indistinct. And even one tuned to 38hz might struggle for punch.
So the tuning is intentional. I was more hoping to get a definite understanding of what the Max SPL window is displaying, and what it’s used for.
thanks
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To give another example, Danley’s subs quote a ‘midway’ figure as their main SPL value, and then quote a second figure above a certain frequency (usually between 70 and 100hz).
This is not because they are trying to show off, but because it’s relevant. That low frequency /mid bass punch is actually much more fundamental to a good bass drum sound than is the 30 odd hz fundamental frequency of the drum.
These things I’ve learned from long experience, having recorded these instruments and processed them live.
There’s only any point trying to boost the actual fundamental note of the drum if you have a massive rig. Most of the time we boost at 60-80hz and 100-140 (for the ‘mid bass’ punch.
This is not because they are trying to show off, but because it’s relevant. That low frequency /mid bass punch is actually much more fundamental to a good bass drum sound than is the 30 odd hz fundamental frequency of the drum.
These things I’ve learned from long experience, having recorded these instruments and processed them live.
There’s only any point trying to boost the actual fundamental note of the drum if you have a massive rig. Most of the time we boost at 60-80hz and 100-140 (for the ‘mid bass’ punch.
Peter,
"Tuning" in a ported cabinet is the Fb, (Frequency of Box) where the impedance and excursion are at minimum. FB is independent of F3, the -3dB point. The box response can be designed to be above average response ("boomy", "rumbly", "muddy", "indistinct") at Fb, or below average response ("tight", "punchy" "clear") at Fb. Same is true for a TH, though there are additional impedance and excursion humps above Fb.
Art
What I really like about Tapped horns as opposed to ported, is that you can often vary the slope of the roll off below the -3 point.
With ported, usually the roll off is very steep after said point. But with tapped horns you can create slopes akin to that of sealed.
With ported, usually the roll off is very steep after said point. But with tapped horns you can create slopes akin to that of sealed.
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The dark red sections are excursion limited, and yes, that's how I read the maximum output of your cabinets.
If you haven't already, scroll back up and read the article I wrote. It details the ways manufacturers cheat with their numbers, often by a large amount.
I can say that, from my own experience, there's a pretty serious difference between something that's -3dB at 55Hz, and -3dB at 38Hz. The PA subs I design are flat-to-40Hz, as I find that's the best compromise between output and extension in portable applications.
I believe my explanation of Hornresp's Max.SPL should be sufficient, but please post up if you have any questions.
Chris
PS - When you say you have a "fair amount of experience with live events", consider that my cabinets have been used for Artists You've Heard Of, and Art's been doing this for longer than I've been alive.
The reason why I wouldn’t quote SPLs like that is the best manufacturers out there aren’t that conservative. Danley is one of them, Meyer another. They tend to give you a practical figure based on what you can actually use.
The thing is, I need something to compare it to, in order to estimate the relative performance of my cabinets to those sold professionally. So we’re all limited somewhat in that regard.
I think my claims to understanding what is required in a live situation are reasonable. “A fair amount” is conservative. Though note that I cater for small functions, mostly, so my low end requirements will be less than for medium scale events and certainly outdoors. So there we may be talking somewhat cross-purposes.
The thing is, I need something to compare it to, in order to estimate the relative performance of my cabinets to those sold professionally. So we’re all limited somewhat in that regard.
I think my claims to understanding what is required in a live situation are reasonable. “A fair amount” is conservative. Though note that I cater for small functions, mostly, so my low end requirements will be less than for medium scale events and certainly outdoors. So there we may be talking somewhat cross-purposes.
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Mind you, mentioning that I had a fair amount of experience wasn’t a claim to superiority, as it may have read- it was to put you in the picture about what I likely did and didn’t understand.
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I guess my next question would be if there is any way of reducing the limitation caused by too little excursion?
I’ve tried reducing the size of the throat. That works, but in the process messes up the frequency response.
Might restricting the size of the baffle cut out work? IE only cutting out half the circle, and leaving some material (though obviously not enough such that the cone fouls the ply at high excursion).
I’ve tried reducing the size of the throat. That works, but in the process messes up the frequency response.
Might restricting the size of the baffle cut out work? IE only cutting out half the circle, and leaving some material (though obviously not enough such that the cone fouls the ply at high excursion).
Please do not quote the entire post just above yours. This is mentioned in the rules section.Over-quotes have now been cleaned up.
There are always frequencies where the excursion is minimal but unless by chance you played the speaker at that exact frequency tone for an extended period the cone will still be moving & cooling the voice coil.
I agree with the comment on the High pass for a Tapped horn. Usually this can be lower than you would expect.
The main reason for tuning for a 40Hz + rather than lower is to increase the efficiency and reduce the size of the cabinet. Those extra bottom Hz come at a price.
I agree with the comment on the High pass for a Tapped horn. Usually this can be lower than you would expect.
The main reason for tuning for a 40Hz + rather than lower is to increase the efficiency and reduce the size of the cabinet. Those extra bottom Hz come at a price.
Yes, so I’ve noticed.
It’s the same with bass reflex also - in that manufacturers will tune their designs higher than they otherwise would, in order to get the efficiency.
Also, having gigged with subs capable of sub-30hz information, if you use it to its full potential, it’s too much. Better have a gig than a thunderstorm. Particularly for small/ medium indoor gigs.
I suspect the optimal response from a single type of subwoofer (a sub that covers both the infra range and the ‘kick bass’ range) is probably about -3 @38hz (for bass reflex).
So for my purposes doing small gigs, a Th-mini, for example, would do the job fine.
As is evident from it's impedance curve, the DSL TH-MINI has an Fb around 50Hz, and like a typical bass-reflex, it's response drops at around 24dB per octave below Fb, excursion increasing rapidly as the driver "unloads" and impedance rises.
It's response is around -12 at 38Hz, and can't be equalized flat that low without running out of excursion at relatively low output, though the larger TH does provide around +3dB gain over a smaller bass reflex cabinet with the same Fb.
It's response is around -12 at 38Hz, and can't be equalized flat that low without running out of excursion at relatively low output, though the larger TH does provide around +3dB gain over a smaller bass reflex cabinet with the same Fb.