I'm really confused. 
I was looking at some morel MW-144 drivers for use in MTM config with separate sub. GM warned me that the power handling of the driver was pretty low bleow 90Hz.
Morel rate these drivers at Nominal power 150W DIN and show a freq response graph going down to about 50Hz (vented I assume).
I was thinking of using the drivers in a sealed enclosure for better midrange detail.
to make things simpler, I did some modeling with a single driver in a sealed enclosure, unibox says max power handling 11.9W!!! long way from 150W!
Seems that X max is reached at around 160Hz. Cone excursion with 150W input at 80Hz is around 10mm (Xmax of driver is 3.5mm) which I assume would pretty much destroy the driver.
Surely there is something wrong here! Morel are praised for the exceptionally high power handling ability. Is this power handling assuming that the drivers is not driven below about 200Hz, or is the construction of the driver such that normal calculations don't apply, or when xmax is exceeded the distortion is minimal, and does not cause damage?
I went and modeled in boxplot, and it shows me a power curve that suggests I should be able to get away with about 113W at 80Hz in a sealed enclosure, I'm really confused!!!!!
I don't know how to interpret the cone excursion graph in speaker workshop.
Any suggestions greatly appreciated.
Tony.
I was looking at some morel MW-144 drivers for use in MTM config with separate sub. GM warned me that the power handling of the driver was pretty low bleow 90Hz.
Morel rate these drivers at Nominal power 150W DIN and show a freq response graph going down to about 50Hz (vented I assume).
I was thinking of using the drivers in a sealed enclosure for better midrange detail.
to make things simpler, I did some modeling with a single driver in a sealed enclosure, unibox says max power handling 11.9W!!! long way from 150W!
Seems that X max is reached at around 160Hz. Cone excursion with 150W input at 80Hz is around 10mm (Xmax of driver is 3.5mm) which I assume would pretty much destroy the driver.
Surely there is something wrong here! Morel are praised for the exceptionally high power handling ability. Is this power handling assuming that the drivers is not driven below about 200Hz, or is the construction of the driver such that normal calculations don't apply, or when xmax is exceeded the distortion is minimal, and does not cause damage?
I went and modeled in boxplot, and it shows me a power curve that suggests I should be able to get away with about 113W at 80Hz in a sealed enclosure, I'm really confused!!!!!
I don't know how to interpret the cone excursion graph in speaker workshop.
Any suggestions greatly appreciated.
Tony.
>Morel rate these drivers at Nominal power 150W DIN and show a freq response graph going down to about 50Hz (vented I assume).
====
OK, so? Does it say it can use all 150W at 50Hz, and if so, at what % distortion?
====
>to make things simpler, I did some modeling with a single driver in a sealed enclosure, unibox says max power handling 11.9W!!! long way from 150W!
====
At what frequency?
====
>Seems that X max is reached at around 160Hz. Cone excursion with 150W input at 80Hz is around 10mm (Xmax of driver is 3.5mm) which I assume would pretty much destroy the driver.
====
Depends on what its Xsus and Xmech specs are.
====
>Surely there is something wrong here! Morel are praised for the exceptionally high power handling ability. Is this power handling assuming that the drivers is not driven below about 200Hz, or is the construction of the driver such that normal calculations don't apply, or when xmax is exceeded the distortion is minimal, and does not cause damage?
====
The calcs apply, but WRT the others, more tech info is required to answer them.
====
>I went and modeled in boxplot, and it shows me a power curve that suggests I should be able to get away with about 113W at 80Hz in a sealed enclosure, I'm really confused!!!!!
====
Me too, as I don't get anywhere near this, but I do get far more than 11.9W/80Hz. What f3 are you simming to? Are you using the demo version or paid for 3.0?
====
>I don't know how to interpret the cone excursion graph in speaker workshop.
====
Not familiar with it. What info does it give?
GM
====
OK, so? Does it say it can use all 150W at 50Hz, and if so, at what % distortion?
====
>to make things simpler, I did some modeling with a single driver in a sealed enclosure, unibox says max power handling 11.9W!!! long way from 150W!
====
At what frequency?
====
>Seems that X max is reached at around 160Hz. Cone excursion with 150W input at 80Hz is around 10mm (Xmax of driver is 3.5mm) which I assume would pretty much destroy the driver.
====
Depends on what its Xsus and Xmech specs are.
====
>Surely there is something wrong here! Morel are praised for the exceptionally high power handling ability. Is this power handling assuming that the drivers is not driven below about 200Hz, or is the construction of the driver such that normal calculations don't apply, or when xmax is exceeded the distortion is minimal, and does not cause damage?
====
The calcs apply, but WRT the others, more tech info is required to answer them.
====
>I went and modeled in boxplot, and it shows me a power curve that suggests I should be able to get away with about 113W at 80Hz in a sealed enclosure, I'm really confused!!!!!
====
Me too, as I don't get anywhere near this, but I do get far more than 11.9W/80Hz. What f3 are you simming to? Are you using the demo version or paid for 3.0?
====
>I don't know how to interpret the cone excursion graph in speaker workshop.
====
Not familiar with it. What info does it give?
GM
Hi GM,
It doesn't say. I guess it's misleading though if they show a graph down to 50Hz and then say power handling 150W. Sort of implies that it should be ok up to the rated power handling.
Unibox doesn't say what freq, just says 11.9W (and the explanation is "Maximum allowable power to keep driver within linear excursion range"
Unibox suggests optimal volume of 4.6L (Qtc of .707) I modeled it at 5L which unibox says is F3 of 85.5Hz, Fb 84.6 Hz.
From the look of the graph in boxplot f3 is around 88Hz with this box volume, (note I didn't save the sim before but with these values the power at 80Hz is around 110W, but dropping steeply, flattening out at about 55W around 30Hz. obviously I can't just stop at 80Hz, even with an active xover, but this is just for example purposes.
It's the unregistered demo version of boxplot 3.0. Not really familiar with it, but thought I'd give it a try to see whether it gave different results to Unibox, which it did!
I've attached the graph out of speaker workshop, but the excursion in db's doesn't make any sense to me........
I'm probably missing something somewhere, but it seems strange I get such different results between two modeling programs (unibox and boxplot), both of which have been around for quite a while, subtle differences I could understand, but massive ones??? (unless I'm just completely screwing it up 🙂 )
Maybe I need to go and re-read the destructions!
Regards,
Tony.
It doesn't say. I guess it's misleading though if they show a graph down to 50Hz and then say power handling 150W. Sort of implies that it should be ok up to the rated power handling.
Unibox doesn't say what freq, just says 11.9W (and the explanation is "Maximum allowable power to keep driver within linear excursion range"
Unibox suggests optimal volume of 4.6L (Qtc of .707) I modeled it at 5L which unibox says is F3 of 85.5Hz, Fb 84.6 Hz.
From the look of the graph in boxplot f3 is around 88Hz with this box volume, (note I didn't save the sim before but with these values the power at 80Hz is around 110W, but dropping steeply, flattening out at about 55W around 30Hz. obviously I can't just stop at 80Hz, even with an active xover, but this is just for example purposes.
It's the unregistered demo version of boxplot 3.0. Not really familiar with it, but thought I'd give it a try to see whether it gave different results to Unibox, which it did!
I've attached the graph out of speaker workshop, but the excursion in db's doesn't make any sense to me........
I'm probably missing something somewhere, but it seems strange I get such different results between two modeling programs (unibox and boxplot), both of which have been around for quite a while, subtle differences I could understand, but massive ones??? (unless I'm just completely screwing it up 🙂 )
Maybe I need to go and re-read the destructions!
Regards,
Tony.
Attachments
DIN and IEC power handling tests use filtered noise signals. The filter rolls off the bass and thus the test is a thermal power handling test - having to do with how much heat can be dissipated by the voice coil.
Excessive excursion at low frequencies is a mechanical thing and has nothing to do with Mfg. power ratings.
Morel's power handling reputation is similar to Dynaudio - they brag about pulse power into their tweeters and low compression in these tests. They usually don't mention the woofers. I have never used them, but the reputation is that they overload gracefully.
Woofer excursion predictions are based on the assumption that all parameters remain linear with increased power, but they don't. Stiffness goes up and Bl goes down with increased distortion - this eans that excursion predictions from programs are over conservative and the driver will often handle perhaps 2-4 times the power predicted. The expense of the nonlinearity is compression and distortion.
Excessive excursion at low frequencies is a mechanical thing and has nothing to do with Mfg. power ratings.
Morel's power handling reputation is similar to Dynaudio - they brag about pulse power into their tweeters and low compression in these tests. They usually don't mention the woofers. I have never used them, but the reputation is that they overload gracefully.
Woofer excursion predictions are based on the assumption that all parameters remain linear with increased power, but they don't. Stiffness goes up and Bl goes down with increased distortion - this eans that excursion predictions from programs are over conservative and the driver will often handle perhaps 2-4 times the power predicted. The expense of the nonlinearity is compression and distortion.
I wouldn't wory about the Morel's handling the rated power.
Unibox is great at showing exactly how little power ratings mean. I modelled a Seas Excel W22EX001, rated max power = 120 Wrms, and found that it reached xmax at 20 Wrms. But as I found out, it means very little. What does count is the amount of spl output you get before reaching xmax, and whether that is acceptable to you.
I love Unibox. This figure is more useful. As Ron mentions, the 150W DIN figure is merely the amount of power the driver can take before failure (burns voice coil, melts adhesives etc.), and nothing to do with keeping the driver in a usable range.
Unibox is great at showing exactly how little power ratings mean. I modelled a Seas Excel W22EX001, rated max power = 120 Wrms, and found that it reached xmax at 20 Wrms. But as I found out, it means very little. What does count is the amount of spl output you get before reaching xmax, and whether that is acceptable to you.
I also found this when first measuring other programs against Unibox, such as WinISD. I found that Unibox takes into account more variables, such as box leakage and damping which accounts for some of the difference.
I've heard that some of the graphs in SW are labelled wrongly. It's probably not db (which doesn't make sense) but in mm. Measure it up against your Unibox output and see what you get.
Thanks Guys,
that clears things up a lot. I guess I can go back to my original plan of crossing over somewhere between 200 and 300Hz if I wan't high (edit distortion free) SPL. Had been given a suggestion of running them down to 80HZ and using my Vifa 10"' woofers purely as subwoofers. This from a HT perspective, more than a stereo perspective. They will do both duties (eventually, stereo to start off).
So near but yet so far, the more I learn the more doubts I have! I was blissfully ignorant before 🙂
I guess I can take the approach that whatever I'm going to do it should be a lot better than my existing setup (unless of course I was so incredibly lucky with it, that it defies logic!)..... I think most people here would probably die if they listened to my current speakers (and I don't mean in extacy). I know I nearly did after hearing a pair of Infinity Electrostatics paired with two six foot tall subwoofers with 6 X 12" drivers in each, All run by some monoblock amps weighing 500KG each (there was a sign warning that you should get an engineer to check your floor could handle the load before purchase!). I came home, and turned on the stereo and nearly cryed 🙂
Only one way to find out though.....
Regards,
Tony.
that clears things up a lot. I guess I can go back to my original plan of crossing over somewhere between 200 and 300Hz if I wan't high (edit distortion free) SPL. Had been given a suggestion of running them down to 80HZ and using my Vifa 10"' woofers purely as subwoofers. This from a HT perspective, more than a stereo perspective. They will do both duties (eventually, stereo to start off).
So near but yet so far, the more I learn the more doubts I have! I was blissfully ignorant before 🙂
I guess I can take the approach that whatever I'm going to do it should be a lot better than my existing setup (unless of course I was so incredibly lucky with it, that it defies logic!)..... I think most people here would probably die if they listened to my current speakers (and I don't mean in extacy). I know I nearly did after hearing a pair of Infinity Electrostatics paired with two six foot tall subwoofers with 6 X 12" drivers in each, All run by some monoblock amps weighing 500KG each (there was a sign warning that you should get an engineer to check your floor could handle the load before purchase!). I came home, and turned on the stereo and nearly cryed 🙂
Only one way to find out though.....
Regards,
Tony.
I remember reading somewhere that a 12 dB/oct crossover slope keeps excursion constant below the crossover point. If you cross over that steep at 90hz, and do the same for your subs, it will not only keep them from sounding bad or dying, but 90hz is a fairly reasonable crossover for home theatre setups.
Good luck, in any case!
Good luck, in any case!
Vikash said:
In a hifi system this, IMHO, is one of the least meaningful specs there is, yet it is the one that gets grabbed onto -- like HP or MHz -- in the bigger is better way of thinking all too common, as a measure of a speaker -- most of the drivers i use are rated at 3-4 W 🙂
dave
and as everyone should know:
>Unibox doesn't say what freq, just says 11.9W (and the explanation is "Maximum allowable power to keep driver within linear excursion range"
====
OK, Unibox appears to be listing the Xmax -24dB displacement power rating, though I'm not sure why.
====
>Unibox suggests optimal volume of 4.6L (Qtc of .707) I modeled it at 5L which unibox says is F3 of 85.5Hz, Fb 84.6 Hz.
====
Since it has served me so well for decades I continue to use the Margolis-Small HP calculator program for sealed that BP 3.0 appears to be based on when I want a bit more accuracy.
Just so we're comparing 'apples to apples', here's the specs I'm using:
Xmax = 0.36cm
dia = 10.69cm
Vd = 32.311cm^2
Qts = 0.3625
Vas = 12.34L
Fs = 45Hz
For a single driver in 5L: Qtc = 0.6344, F3 = 94.81Hz/70.3W/100.49dB/m, Fb = 84.09Hz.
For Qtc = 0.707: 3.623L, F3/Fb = 94.46Hz/69.26W/100.43dB/m.
====
>It's the unregistered demo version of boxplot 3.0.
====
It has a number of 'bugs', so I wouldn't pay too much attention to its accuracy. It's really only meant to give you an idea of what you'll get for $25. Well worth the few $$ IMO. I use it all the time to do quick comparisons.
====
>I've attached the graph out of speaker workshop, but the excursion in db's doesn't make any sense to me........
====
That's a phase plot. Do you get the same graph when you ask for a phase plot?
Anyway, while you now have a better understanding of power ratings, etc., like most things in audio you'll have to listen/experiment with the driver if you want to push it beyond its low distortion spec rating to find its/your acceptable distortion limit regardless of what alignment or program you use to sim it.
====
>I remember reading somewhere that a 12 dB/oct crossover slope keeps excursion constant below the crossover point. If you cross over that steep at 90hz, and do the same for your subs, it will not only keep them from sounding bad or dying, but 90hz is a fairly reasonable crossover for home theatre setups.
====
Correct, though all things considered, using the receiver's 80Hz XO would be my first choice just to keep it simple.
GM
====
OK, Unibox appears to be listing the Xmax -24dB displacement power rating, though I'm not sure why.
====
>Unibox suggests optimal volume of 4.6L (Qtc of .707) I modeled it at 5L which unibox says is F3 of 85.5Hz, Fb 84.6 Hz.
====
Since it has served me so well for decades I continue to use the Margolis-Small HP calculator program for sealed that BP 3.0 appears to be based on when I want a bit more accuracy.
Just so we're comparing 'apples to apples', here's the specs I'm using:
Xmax = 0.36cm
dia = 10.69cm
Vd = 32.311cm^2
Qts = 0.3625
Vas = 12.34L
Fs = 45Hz
For a single driver in 5L: Qtc = 0.6344, F3 = 94.81Hz/70.3W/100.49dB/m, Fb = 84.09Hz.
For Qtc = 0.707: 3.623L, F3/Fb = 94.46Hz/69.26W/100.43dB/m.
====
>It's the unregistered demo version of boxplot 3.0.
====
It has a number of 'bugs', so I wouldn't pay too much attention to its accuracy. It's really only meant to give you an idea of what you'll get for $25. Well worth the few $$ IMO. I use it all the time to do quick comparisons.
====
>I've attached the graph out of speaker workshop, but the excursion in db's doesn't make any sense to me........
====
That's a phase plot. Do you get the same graph when you ask for a phase plot?
Anyway, while you now have a better understanding of power ratings, etc., like most things in audio you'll have to listen/experiment with the driver if you want to push it beyond its low distortion spec rating to find its/your acceptable distortion limit regardless of what alignment or program you use to sim it.
====
>I remember reading somewhere that a 12 dB/oct crossover slope keeps excursion constant below the crossover point. If you cross over that steep at 90hz, and do the same for your subs, it will not only keep them from sounding bad or dying, but 90hz is a fairly reasonable crossover for home theatre setups.
====
Correct, though all things considered, using the receiver's 80Hz XO would be my first choice just to keep it simple.
GM
Nappylady said:
Thanks Nappylady. Initially It will be a passive Xover, but eventually HT pre-amp, so will be active, probably with quite a high slope (not sure but I would guess 18db/oct at least) so I guess that means I should be pretty safe.
Also I think I'm just paranoid since I used to blow so many tweeters (and with the xover I had they were only rated at about 10W), and I figured the mids would be getting significantly more power than that, and driving them down to 80Hz even more! I really never use the stereo at those volume levels any more, though. When the stereo can be heard 3 blocks away, and the police get called it really is a little too loud 😉 I don't think I would want to subject quality speakers to that sort of treatment anyway, build some cheap and nasties if I ever get the urge 🙂
planet10 said:
Yeah it's a bit like the teenager bragging about how he's got 200W speakers in his car, which means they are really loud, even though he has a 5W RMS/channel amp driving them 🙂
I like the bit about the bigger electrons 🙂 Maybe I should start designing a quantum amplifier that run's on quarks, they are smaller so surely it should sound even better, and while I'm at it some quantum speakers to go with it, which could be in any state at the same time, and would therefore not have any distortion at all!!!! 😉
GM, I'm going to do a separate post to reply, to give me time to digest your info 🙂
Regards,
Tony.
GM said:
OK I see where the difference is now. I had stuck in 142mm as dia which now that I look at it is OD (outside diameter?) duhhhh. That would certainly make a difference, unibox uses Sd which is 90cm^2 but in boxplot I just put in 142 mm...... also I'm using xmax of .35cm. What is Vd? ~32cm^2 doesn't fit with anything I've seen..........
I checked but SW doesn't have a phase plot graph, but on comparing the supposed excursion graph to what unibox produces it looks very simmilar, I think it probably is an excursion graph, the scale is just meaningless. (sorry there is a phase graph, it's on one of the freq response graphs, and yes it does also look very much like the plot I attached).
Yep I guess I have to suck it and see 🙂 maybe I will only get two drivers to start off with build one cabinet, and try it out, that way if I'm not happy I won't have so much to loose!
Where did you get the 10.69cm dia from BTW?
Regards,
Tony.
wintermute said:
The usual cause of that is simply running your amp out of power & generating all sorts of nasties that eat tweeters for breakfast.
dave
>Also I think I'm just paranoid since I used to blow so many tweeters (and with the xover I had they were only rated at about 10W),
====
Assuming you didn't have them XO'd too close to their Fs, clipping the amp is what normally blows them.
====
>I don't think I would want to subject quality speakers to that sort of treatment anyway, build some cheap and nasties if I ever get the urge
====
This is like running a Yugo flat out Vs creeping around in a Ferrari. Quality speakers, when driven by a quality amp of sufficient power to handle the transients without clipping are for 'cranking'. 😉
====
>OK I see where the difference is now. I had stuck in 142mm as dia which now that I look at it is OD (outside diameter?) duhhhh.
That would certainly make a difference, unibox uses Sd which is 90cm^2 but in boxplot I just put in 142 mm......
>There did you get the 10.69cm dia from BTW?
====
OK, (90cm^2/pi)^0.5*2 = ~10.7cm diameter Vs my 10.69cm, close enough.
====
> also I'm using xmax of .35cm. What is Vd? ~32cm^2 doesn't fit with anything I've seen..........
====
Vd is the amount of air displaced at some excursion, so 90cm^2/32.311cm^2 = 0.359cm excursion, or insignificantly more than what you're using.
====
>I checked but SW doesn't have a phase plot graph, but on comparing the supposed excursion graph to what unibox produces it looks very simmilar, I think it probably is an excursion graph, the scale is just meaningless.
====
OK, but even so, at a glance it doesn't look right. If I get a chance I'll check it further to see if I can get the correct scale if the plot proves accurate.
====
>Yep I guess I have to suck it and see maybe I will only get two drivers to start off with build one cabinet, and try it out, that way if I'm not happy I won't have so much to loose!
====
Yes, and no. I've built many mono 'proofs of concept', but the stereo version didn't always pan out due to lack of good room integration, so YMMV if you're limited as to where they must go.
GM
====
Assuming you didn't have them XO'd too close to their Fs, clipping the amp is what normally blows them.
====
>I don't think I would want to subject quality speakers to that sort of treatment anyway, build some cheap and nasties if I ever get the urge
====
This is like running a Yugo flat out Vs creeping around in a Ferrari. Quality speakers, when driven by a quality amp of sufficient power to handle the transients without clipping are for 'cranking'. 😉
====
>OK I see where the difference is now. I had stuck in 142mm as dia which now that I look at it is OD (outside diameter?) duhhhh.
That would certainly make a difference, unibox uses Sd which is 90cm^2 but in boxplot I just put in 142 mm......
>There did you get the 10.69cm dia from BTW?
====
OK, (90cm^2/pi)^0.5*2 = ~10.7cm diameter Vs my 10.69cm, close enough.
====
> also I'm using xmax of .35cm. What is Vd? ~32cm^2 doesn't fit with anything I've seen..........
====
Vd is the amount of air displaced at some excursion, so 90cm^2/32.311cm^2 = 0.359cm excursion, or insignificantly more than what you're using.
====
>I checked but SW doesn't have a phase plot graph, but on comparing the supposed excursion graph to what unibox produces it looks very simmilar, I think it probably is an excursion graph, the scale is just meaningless.
====
OK, but even so, at a glance it doesn't look right. If I get a chance I'll check it further to see if I can get the correct scale if the plot proves accurate.
====
>Yep I guess I have to suck it and see maybe I will only get two drivers to start off with build one cabinet, and try it out, that way if I'm not happy I won't have so much to loose!
====
Yes, and no. I've built many mono 'proofs of concept', but the stereo version didn't always pan out due to lack of good room integration, so YMMV if you're limited as to where they must go.
GM
GM said:
I hadn't considered that, allways thought that if the amp wasn't cranked right up, then it wouldn't be clipping, but I guess if the amp can deliver full power on a .7V input signal, then with CD as source you could get full power long before winding the volume control right up (specs on the amp are .01% THD at 100W So I had always naively thought it wouldn't be clipping . I think it has enough reserves in the PS to deliver about 150W very short term, but I'd have to check that.
Arrrr math, I remember math 🙂
That makes sense!
Don't worry about it too much GM. I can use the other progs. SW is good for testing, but not as good for modeling IMO.
Oh well wish me luck. I think they will be better than what I currently have anyway It turns out...... Should keep me happy for at leas a while 🙂
Regards,
Tony.
>I hadn't considered that, allways thought that if the amp wasn't cranked right up, then it wouldn't be clipping, but I guess if the amp can deliver full power on a .7V input signal, then with CD as source you could get full power long before winding the volume control right up (specs on the amp are .01% THD at 100W So I had always naively thought it wouldn't be clipping . I think it has enough reserves in the PS to deliver about 150W very short term, but I'd have to check that.
====
The real issue here is one of dynamic headroom. Some CDs have >30dB peaks centered around 300Hz and are usually clipped to boot, so are nasty for the tweeter to begin with.
+30dB requires a hair over 1kW on the face of it, but this doesn't factor in the driver's efficiency, etc., but to keep an example simple......
Using speakers that are 88dB/m eff. in the 300hz BW with a tweeter XO'd at 2.2kHz/2nd order and they're cranked to a moderately high 88dB/m average when along comes a +30dB transient spike.......all of a sudden the speaker is demanding 1kW from this dinky little 150Wer, so it clips. If there's no limiter then you'll hear a high pitched 'crack' from the tweeter. If it does, then it should compress it down to 150W at a high enough slew rate that you won't even notice it clipping without a light to clue you in.
Thing is though, the tweeter is demanding its portion of the 1kW, and with up to 150W available, the limiter doesn't really protect it unless it has a >150W rating. In this example, SPL falls ~11.66dB between 300Hz and 4.4kHz, or ~ +18.34dB = ~54.22W required, so probably won't blow it. Crank it up 3dB more though, and while it's still not all that loud at a typical listening distance, it's demanding ~108.2W. Not many tweeters can take this much overdrive repeatedly. Movie/many music recordings get around this by limiting the peaks to +20dB, so folks like me that have very efficient systems need an expander to uncompress them.
Anyway, good luck with the project!
GM
====
The real issue here is one of dynamic headroom. Some CDs have >30dB peaks centered around 300Hz and are usually clipped to boot, so are nasty for the tweeter to begin with.
+30dB requires a hair over 1kW on the face of it, but this doesn't factor in the driver's efficiency, etc., but to keep an example simple......
Using speakers that are 88dB/m eff. in the 300hz BW with a tweeter XO'd at 2.2kHz/2nd order and they're cranked to a moderately high 88dB/m average when along comes a +30dB transient spike.......all of a sudden the speaker is demanding 1kW from this dinky little 150Wer, so it clips. If there's no limiter then you'll hear a high pitched 'crack' from the tweeter. If it does, then it should compress it down to 150W at a high enough slew rate that you won't even notice it clipping without a light to clue you in.
Thing is though, the tweeter is demanding its portion of the 1kW, and with up to 150W available, the limiter doesn't really protect it unless it has a >150W rating. In this example, SPL falls ~11.66dB between 300Hz and 4.4kHz, or ~ +18.34dB = ~54.22W required, so probably won't blow it. Crank it up 3dB more though, and while it's still not all that loud at a typical listening distance, it's demanding ~108.2W. Not many tweeters can take this much overdrive repeatedly. Movie/many music recordings get around this by limiting the peaks to +20dB, so folks like me that have very efficient systems need an expander to uncompress them.
Anyway, good luck with the project!
GM
Thanks GM.
I knew that the dynamic range of CD was big but had no idea it was that dramatic! I always thought my tweeters were copping more than 10W even though I never did any calculations to try and work it out.
Now I just need to redo my cabinet design (since my plans from 12 months ago were completely different) and maybe I can make a start 🙂
Regards,
Tony.
I knew that the dynamic range of CD was big but had no idea it was that dramatic! I always thought my tweeters were copping more than 10W even though I never did any calculations to try and work it out.
Now I just need to redo my cabinet design (since my plans from 12 months ago were completely different) and maybe I can make a start 🙂
Regards,
Tony.
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