This is where the compression is the highest and causes the dip in excursion (around 45Hz). That means that the system suppresses the excursion while the driver 'fights' it (enforced by the coupling of several TH's in your stack). The bad ‘luck’ is that the Fs (the driver’s own resonance) of the 3015lf, is also around 45Hz which makes the driver run into partial movements. The cracks will line up the pattern in the picture I showed. So again, this is not over excursion but a good example of partial movements that ruined your drivers.
Nope, TH’s are 1/4WL tapped pipes/horns. The -3dB point you often find around 1/3WL for a single TH’s (with the best balance for the highest efficiency). This depends on the relation between path length and mouth size. Small correction, I stated earlier 12dB slope @ 40Hz but that should be 45Hz for the SS15.
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I see no reason for the 45Hz pistonic resonance to coincide with the partial movement problems. Could you explain further?
And I'd've thought that a 18" driver would suffer more from higher compression ratios, and several smaller drivers should be used.
An externally hosted image should be here but it was not working when we last tested it.
http://www.b-52pro.com/Products/LXCompressionEmpty.html
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Hi!
Looking at: Mms BL
3015LF 93.4g 17T-M
15TBX100 163g 25.5T-M demodulating rings
Is the stiffer cone of the B&C better for TH?
SB1000 drivers always damage the cones near the "V" apex where the preasure is higher; so do we take special care to avoid this points?
Trying different loudspeakers in THs we notice how a loudspeaker will remain with less excursion;The PRO factories have always that OEM drivers that remain quieter (re excursion) despite using same Pe.
Could verify this in a TH12 and how the sound of a bass guitar comes out without some colorations around 40/50 Hz.
So I learned that how it plays with good SPL and not how much SPL it delivers is better perhaps to my ears.
I've to try djk's PPSL to compare...
Regards,
Looking at: Mms BL
3015LF 93.4g 17T-M
15TBX100 163g 25.5T-M demodulating rings
Is the stiffer cone of the B&C better for TH?
SB1000 drivers always damage the cones near the "V" apex where the preasure is higher; so do we take special care to avoid this points?
Trying different loudspeakers in THs we notice how a loudspeaker will remain with less excursion;The PRO factories have always that OEM drivers that remain quieter (re excursion) despite using same Pe.
Could verify this in a TH12 and how the sound of a bass guitar comes out without some colorations around 40/50 Hz.
So I learned that how it plays with good SPL and not how much SPL it delivers is better perhaps to my ears.
I've to try djk's PPSL to compare...
Regards,
The QSC PL380 has lots of peak power, it's a great sub amp.
Hard clipped into 8 ohms it could (and no doubt did) deliver upwards of 2500 watts per speaker.
As has been pointed out, turning the amp's input down has nothing to do with maximum output. Turn the amp input down 6 dB, and the mixer up 6 dB, the amp puts out exactly the same level.
By the way, we speak in terms of dB regarding sound, half gain is -3dB, probably not what you meant when you wrote "At half gain".
Set your system's gain structure and the crossover limiters properly, you should have no problem.
Check the excursion while driving the subs with pink noise, simply put a white dot on the cone with White Out or a silver Sharpie, persistence of vision makes it easy to see the peak to peak movement.
Measure the P to P movement, divide it by two. If the excursion exceeds the speaker's Xmax when the mixer is cranked up with the amp wide open, clamp your limiter down tighter.
Reducing amp gain can improve signal to noise ratio, but there is always the chance some little fingers will turn the amp all the way up, and tear/burn up cones, which is why most sound providers always set limiters with the amp's volumes set wide open, unless the amps are locked away from meddling fingers.
Art Welter
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`yup maybe a smaller hole in the middle would even out the pressure of the cone.
you used 18 mm would and x/limit is 17 mm,so just a shelf with a hole or oval in the middle on top off the speaker baffle should help.
and as sugested a brickwall limiter.
to measure excursion ,put a white dot on the cone,and just eyeball guestimate it when playing lows,you can set your limiter this way
4pyros you mentioned you are using a Behringer Crossover.
Assuming that it is the DCX2496 - I have not seen much info on line about using the clip limiters. For many amplifiers the clip limit is around the minus 15 to 20 db level. I see that the QSC PL380 has selectable sensitivity settings - and the volume controls can be locked off to prevent tampering. It also has a built in switchable clip limiter.
http://www.qscaudio.com/pdfs/Specifications/PowerLight3_spec.pdf
You could increase the headroom by switching down the sensitivity of the amp, but it depends on the sensitivity of all of your amplifiers and speakers. You will need to adjust the gain for each frequency band to get an even frequency response, preferably with the volume controls on all of the amps in the failsafe flat out position.
The brick-wall limiters are audible, and produce a noise as they kick in, but once operating you can input an increasing sine wave into the input and see a constant limited output as checked on an oscilloscope.
In my rig setup, I started with a dummy load, and a scope on the amplifier output, and fed an increasing sine wave into the input at a frequency within the pass band of the output to be tested. When amplifier clipping was detected I set the limiters to kick in at just below that level.
The settings were then used as the basis for more practical testing with the rig at full levels.
In you case you have way more power than your Eminence 3015 speakers can handle.
So Art Welters practical method of checking the X-max of the actual drivers in the cabs is ideal.
Regards
Martin
Assuming that it is the DCX2496 - I have not seen much info on line about using the clip limiters. For many amplifiers the clip limit is around the minus 15 to 20 db level. I see that the QSC PL380 has selectable sensitivity settings - and the volume controls can be locked off to prevent tampering. It also has a built in switchable clip limiter.
http://www.qscaudio.com/pdfs/Specifications/PowerLight3_spec.pdf
You could increase the headroom by switching down the sensitivity of the amp, but it depends on the sensitivity of all of your amplifiers and speakers. You will need to adjust the gain for each frequency band to get an even frequency response, preferably with the volume controls on all of the amps in the failsafe flat out position.
The brick-wall limiters are audible, and produce a noise as they kick in, but once operating you can input an increasing sine wave into the input and see a constant limited output as checked on an oscilloscope.
In my rig setup, I started with a dummy load, and a scope on the amplifier output, and fed an increasing sine wave into the input at a frequency within the pass band of the output to be tested. When amplifier clipping was detected I set the limiters to kick in at just below that level.
The settings were then used as the basis for more practical testing with the rig at full levels.
In you case you have way more power than your Eminence 3015 speakers can handle.
So Art Welters practical method of checking the X-max of the actual drivers in the cabs is ideal.
Regards
Martin
This sounds like a good, practical method. I like it.
Note that you'll need a BIG dummy load at these powers. I've even used those little oil filled radiators (space heaters) for this - they can take the power.Note 2: Wear ear plugs and ear muffs if you are going to check the x-max live. The SPL can be tremendous. Protect your ears.
Thank you all for your help thus far. I am learning alot.
But still no one has expressed an opinon in regards to my TH design Questoin.
I dont understand if part of the cones were damaged do to the lack of mecanical dampening at the begining of the horn (No Tapper) and only that part of the cone went into resonice or if that part of the speaker was damaged do to the lack of electrical dampining and to much presser in that area.
All this leading to my burning questoin, Can a change in the throat area help prevent this. Only because I made the speaker plate removeble and changes to the throat can eazy be done if it will help.
Thanks Andy
But still no one has expressed an opinon in regards to my TH design Questoin.
I dont understand if part of the cones were damaged do to the lack of mecanical dampening at the begining of the horn (No Tapper) and only that part of the cone went into resonice or if that part of the speaker was damaged do to the lack of electrical dampining and to much presser in that area.
All this leading to my burning questoin, Can a change in the throat area help prevent this. Only because I made the speaker plate removeble and changes to the throat can eazy be done if it will help.
Thanks Andy
Andy it's difficult to explain in another language but i'll try again. The horn path length is frequency related. That means every frequency has its own spot in the horn. The driver has a certain diameter and therefore covers a wider range than just one frequency. While one half of the cone is suppressed by the system (45Hz) the other half falls into the region that covers less suppression (40Hz) and where excursion rises fast. That means two opposite forces at the same time since music signals cover a wide range in the frequency band. The problem is that this falls together with the resonance of the driver in free space, its Fs (around 42Hz), its own resonance frequency. That means the mechanical structure of the cone is the weakest at its own resonance which deforms the cone by the partial movements.
You probably don't need to change anything as long you keep your power under control. In case you need more SPL go for another design with more capable drivers.
You probably don't need to change anything as long you keep your power under control. In case you need more SPL go for another design with more capable drivers.
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can you post picture of your speaker plate? just wondering if there was something physical that the cone could have hit?
I agree with Djim:
"You probably don't need to change anything as long you keep your power under control. In case you need more SPL go for another design with more capable drivers. "
My tests using various cones in my Keystone tapped horn told me that the flexible Eminence 4015LF could not hold up to the pressures presented at full power (it distorted so badly I did not even bother measuring it other than frequency response at lower power level), while the Lab 12 and BC18SW115 could handle full rated power and still sound good.
The 3015LF cone is even more flexible than a 4015LF, so limiting (as jbell has always suggested for the SS15) is a must when using big power amps that are easily capable of driving the speaker well past Xmax into kinksville.
Remember, your amp is capable of around 2 horsepower per speaker, when you think how much "kick" a horse has, it is amazing a paper cone can handle even a fraction of that power.
Art Welter
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