Powersoft Digam 5000 on T48-3015LF

Is this amp OK?
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thijs666
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Re: Powersoft Digam 5000 on T48-3015LF

#16 Post by thijs666 »

Grant Bunter wrote:Did Xmax and impedance give you your answer, or were you looking for something else?
I'm not sure I understand you correctly, but no. More specific:
Xmax: 60V limits driver to Xmax or Xmech? If Xmax, then there could be room for more voltage (short term, as in musical peaks) without damaging the speaker.

Impedance: I assume you mean thermal limits after dividing square voltage by impedance? Then 60V equals 450W continuous, while 900W peak is allowed, so there's also room for a little extra.
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

Gregory East
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Re: Powersoft Digam 5000 on T48-3015LF

#17 Post by Gregory East »

I believe going over xmax doesn't translate into significantly more volume, but that isn't a reason to limit. If the limit didn't matter why would there be a limit? Yoda not giving it up easy lately.
BAT10, Bad Auto Tuba. Reverse folded TAT to fit JBL 1014D, 350W driver, voltage limit unknown.

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thijs666
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Re: Powersoft Digam 5000 on T48-3015LF: No limiter needed?

#18 Post by thijs666 »

No, Yoda not giving it up easily :lol: .

About exceeding Xmax not translating into more volume: I wouldn't have started this thread (and the measurement) if I didn't notice a significant increase in volume and 'cleanness' of the sound, especially in the kick :cowboy: . And now I wonder how safe it is to use the Digam without an external limiter, since its built-in limiter works a little different then a normal limiter... (see the screenshots of the scope measurements).
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

Grant Bunter
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Re: Powersoft Digam 5000 on T48-3015LF: No limiter needed?

#19 Post by Grant Bunter »

thijs666 wrote:No, Yoda not giving it up easily :lol: .

About exceeding Xmax not translating into more volume: I wouldn't have started this thread (and the measurement) if I didn't notice a significant increase in volume and 'cleanness' of the sound, especially in the kick :cowboy: . And now I wonder how safe it is to use the Digam without an external limiter, since its built-in limiter works a little different then a normal limiter... (see the screenshots of the scope measurements).
It's not safe to rely on the the amps limiter at all. My understanding is the limiter on your amp isn't a brick wall limiter as you may find in say the Crown xti series. It a protective mechanism for the amp, rather than the cabs attached to it.
If you have a DCX sitting there, use it to limit :)

Maybe I didn't make it quite clear,
It's not singularly Xmax, nor impedance. It's a combination of both that are the top 2 criteria for setting voltage limits. Xmax is a constant for a given driver, impedance is not constant with the driver in use. There are other factors as well, ( I imagine, in this case, 1 may be driver response in a given horn design, based on modelling software) but that is beyond my knowledge base.

You've mentioned the 900W peak a few times.
I'm not a speaker designer, so I can't comment on how any given company decides they want xyz TS parameters. I don't know that the 900W peak may exist in certain situations, such as "loaded in a direct radiator cab tuned to xHz", but that same peak may exceed the voltage limit that prevents driver failure in a horn loaded cab with blah blah blah mouth size etc.

That's where the "it's not about watts, it's about voltage" comes from I guess.
I'm not sure if there is a safety factor involved in arriving at a voltage setting.
If a voltage limit is set, in the case of your T48, by the cab's designer, then it would seem that you can't go over that voltage (even for brief periods of time due to peaks) without expecting driver failure.

If you need more volume, the rule of thumb seems to be, for good reason, "don't turn it up, build more cabs"...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

SirNickity
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Re: Powersoft Digam 5000 on T48-3015LF

#20 Post by SirNickity »

IIUC, this isn't about trying to "push it" any further, it's about safety margins. We know the amp isn't a brick-wall. It's incapable of sustained output over the safe limit of the driver, but it will peak beyond the safe limit. (Right?)

So the question is (again, if I'm following) -- with a 3015, what is actually damaged by over-excursion? Does the voice coil former start slapping the back of the motor? Does the surround rip? What's the failure mode of this particular driver? And, knowing it won't be subject to this abuse for extended periods (as would be the case of someone trying to get 3dB more sound throughout the night with too few cabs) before the "limiter" kicks in on the amp, will the driver take a little beating above and beyond this voltage limit for those few crucial miliseconds, or will it immediately fly out of the basket at 60.1V?

Unfortunately I don't know, myself. But, I know folks around here have reconed these things and have a little experience with how and when they break.

I would personally treat that limit as an instant-death figure, and protect accordingly. But if nothing else, it would be nice to know just for kicks.

Gregory East
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Re: Powersoft Digam 5000 on T48-3015LF

#21 Post by Gregory East »

SirNickity wrote:I would personally treat that limit as an instant-death figure, and protect accordingly. But if nothing else, it would be nice to know just for kicks.
And me.

Nice post Nick.
BAT10, Bad Auto Tuba. Reverse folded TAT to fit JBL 1014D, 350W driver, voltage limit unknown.

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thijs666
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Re: Powersoft Digam 5000 on T48-3015LF: No limiter needed?

#22 Post by thijs666 »

Grant Bunter wrote:It's not safe to rely on the the amps limiter at all. My understanding is the limiter on your amp isn't a brick wall limiter as you may find in say the Crown xti series. It a protective mechanism for the amp, rather than the cabs attached to it.
Agreed. It's more of a marketing term :wall: .
Grant Bunter wrote:If you have a DCX sitting there, use it to limit :)
I did, until I noticed this amps rather particular way of limiting.
Grant Bunter wrote:It's not singularly Xmax, nor impedance. It's a combination of both that are the top 2 criteria for setting voltage limits. Xmax is a constant for a given driver, impedance is not constant with the driver in use. There are other factors as well, ( I imagine, in this case, 1 may be driver response in a given horn design, based on modelling software) but that is beyond my knowledge base.
Check :wink: . Check out my impedance plot of the T48:

Image
Grant Bunter wrote:If a voltage limit is set, in the case of your T48, by the cab's designer, then it would seem that you can't go over that voltage (even for brief periods of time due to peaks) without expecting driver failure.
And that's what I'd like to know: what happens if you exceed the 60V threshold short term (which is not that big a deal, I think; only perhaps a risk of heating up the motor structure a little more)? Does the voice coil leave its lineair field of operation? Or does Xmech (or Xlim) get exceeded, resulting on all kinds of damage? Does the cone tear due to too much strain/pressure?
I agree the safe road is to limit at 60V, but out of interest -and of course because I acquired a new amp with a little odd limiting system- I would like to know what limit's the 3015LF to 60V?
SirNickity wrote:IIUC, this isn't about trying to "push it" any further, it's about safety margins. We know the amp isn't a brick-wall. It's incapable of sustained output over the safe limit of the driver, but it will peak beyond the safe limit. (Right?)
Correct!
SirNickity wrote:So the question is (again, if I'm following) -- with a 3015, what is actually damaged by over-excursion?
What I meant was: "What is actually happening past 60V?"
SirNickity wrote:And, knowing it won't be subject to this abuse for extended periods (as would be the case of someone trying to get 3dB more sound throughout the night with too few cabs) before the "limiter" kicks in on the amp, will the driver take a little beating above and beyond this voltage limit for those few crucial miliseconds, or will it immediately fly out of the basket at 60.1V?
You hit the spot! 8)
SirNickity wrote:I would personally treat that limit as an instant-death figure, and protect accordingly.
I don't expect it to be that critical, but if you're not behind the knobs and faders, it would be a wise thing to set the limits in concrete :!:

I feel more comfortable knowing the DCX2496 brick-limits to 60V. But knowing what sets this limit would make me feel more comfortable (or 'in control', you could say) using the Digam5000s internal limiter system, which I prefer since the latter sounds more natural!
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

Ryan A
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Re: Powersoft Digam 5000 on T48-3015LF

#23 Post by Ryan A »

It sounds like you're wanting someone to say you can exceed 60V. Its already been established, so why try and change it? From my understanding, the limit in these cabs is usually related to overexcursion and mechanical stress on the driver. Power compression will also probably set in severely above 60V (where most of the power added above 60 goes to generating heat rather than useable sound). I'm sure its not an "instant death" figure because Bill should have put at least a few volts of safety margin in there. But if you can afford another $250 speaker then by all means exceed the voltage to your heart's content, and let us know what you found out.

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Re: Powersoft Digam 5000 on T48-3015LF

#24 Post by thijs666 »

ryan222h wrote:It sounds like you're wanting someone to say you can exceed 60V. Its already been established, so why try and change it? From my understanding, the limit in these cabs is usually related to overexcursion and mechanical stress on the driver. Power compression will also probably set in severely above 60V (where most of the power added above 60 goes to generating heat rather than useable sound). I'm sure its not an "instant death" figure because Bill should have put at least a few volts of safety margin in there. But if you can afford another $250 speaker then by all means exceed the voltage to your heart's content, and let us know what you found out.
What I would like to hear of course is that I can safely use the built in 'limiter' from the amp :mrgreen: . I am not trying to get someone to say it's safe to go over 60V, only to get back to them when I broke a driver and blaming it on them :slap: .
I'm trying to find out what factor limits the 3015LF to 60V. If you say it's overexcursion then I'd like to ask: is that over-linear-excursion or over-mechanical-excursion? The latter obviously resulting in damage.
Yes, of course power compression sets in heavily above and even below 60V, but my ears tell me there's more juice in my 3015LF/T48 'limited' with the amps circuitry than there is with the DCX limiter set at 60V brick wall. Again, the amps limiter sounding more 'natural' and with a louder kick than when using the DCX limiter... (of course my tests were very short, as I don't have money to spend as water to buy recone kits; actually, the €5 DVM I used to keep an eye on the voltage didn't show any voltages above 65V, but to be fair, it's not capable of showing peak values; its refresh rate is about 0.5 seconds).

...and I must admit, it all goes wrong when dubstep is to be played, as can be seen on the measurements I posted. It doesn't sound bad, but the SPL drop is really audible when that compressor kicks down the voltage :chainsaw: .
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

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Re: Powersoft Digam 5000 on T48-3015LF

#25 Post by Ryan A »

It should really be pounding at 60V. If you are bothered by the limiter kicking in at that high of a voltage, then you probably need more cabs. One thing you don't want to do with pro cabs is exceed or come close to exceeding your maximum cab output. In pro sound, having some headroom is important.

There could be other factors in your limiter that are causing the kicks to be muted too quickly, like the attack and release times (which I'm not sure can be adjusted with the DCX).

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Re: Powersoft Digam 5000 on T48-3015LF

#26 Post by thijs666 »

ryan222h wrote:It should really be pounding at 60V.
It is! 8)
ryan222h wrote:If you are bothered by the limiter kicking in at that high of a voltage, then you probably need more cabs. One thing you don't want to do with pro cabs is exceed or come close to exceeding your maximum cab output. In pro sound, having some headroom is important.
Very valid point :slap: .
ryan222h wrote:There could be other factors in your limiter that are causing the kicks to be muted too quickly, like the attack and release times (which I'm not sure can be adjusted with the DCX).
I don't think the kicks are muted too quickly, don't get me wrong. The DCX has a brick wall limiter with only the threshold and release time to be adjusted. So no short peaks are passed. The Digam's limiter does pass those peaks, that's definitely sounding more musical, but this also means peak voltages above 60V. But after just a few seconds a gain reduction circuit limits continuous sine waves to about 30~35V, as can be seen in the measurements I posted.
What I was hoping to find out by starting this thread is whether (a) (very) short peak(s) above 60V will result in instant damage :noob:. In other words: what is the limiting factor here? Cone tear? Damage to the voice coil/spider/surround/etc by overexcursion?
But you said it: it's better to have some headroom for safety. Too bad, I hoped to be able to raise the T48 to another level :loler: . My ears say it sounded like I had about 2~3dB of extra headroom (which equals to about double the power, as you all know) without any signs of strain whatsoever. 'Too bad' you can't hear the speaker distort/complain... :clap: :mrgreen: .
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

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Re: Powersoft Digam 5000 on T48-3015LF

#27 Post by Grant Bunter »

thijs666 wrote: What I was hoping to find out by starting this thread is whether (a) (very) short peak(s) above 60V will result in instant damage :noob:. In other words: what is the limiting factor here? Cone tear? Damage to the voice coil/spider/surround/etc by over excursion?
Same old same old. If any of the "consequences" you mention occur, your gig could end up blown as well.

My experience with driver failure is from lots of direct radiator cabs via my mate who is a certified Jaybee re-coner.
The most common driver failures are:
1. Cone damage Lowest level is tear to highest level total shred. I include surround in cone damage because it's an integral part of the cone.
2. Voice coil burnout.
Spider damage is rare (Unless the driver catches on fire). As is magnet movement leading to misalignment (this is usually caused physically, as in a drop, however some brands of driver bolt the magnet to the frame and if not secured adequately to prevent loosening through use, then that can be a cause as well).

From what I've seen here so far, the more common driver failure in Bills designs is tearing.
That may suggest over excursion is the cause, as generally, voltage has been exceeded. This is a little anecdotal as some of the driver failures have occurred in cabs that generally aren't limited, or cabs that should have been limited but were not.

In order to work out where the failure will occur, I guess you would need to quantify the amplitude of the peak above 60V. Even if brief, higher peaks (say 10% or 66V) will probably bring the driver undone. Does 1 or 2 volts higher become a problem? No idea. Personally, for my cabs, I don't want to find out, either in theory or reality.

As Ryan 222H says, if you want more, you need more cabs.
Why try to squeeze an extra (maybe) 2-3dB from what you have (which is roughly equivalent to 1 cab), with a possible consequence of driver failure, when you could build 2 extra cabs and add 6dB?

The problem I see with trying to squeeze more voltage is this:
Say you go "right, I'll squeeze 2 extra volts to get an average increase of (say) 2 dB".
But you don't brick wall limit, so you still hit peaks above the 2V extra. Maybe 3-5 volts.
Your 60 volts suddenly becomes 65-7V, even for brief peaks.
All of a sudden what was boom tah boom boom tah becomes tah....tah....tah...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Re: Powersoft Digam 5000 on T48-3015LF

#28 Post by SirNickity »

Grant Bunter wrote:The problem I see with trying to squeeze more voltage is this:
Say you go "right, I'll squeeze 2 extra volts to get an average increase of (say) 2 dB".
Sure, but that's not at all the point of this. I know that's usually why someone will ask, but his amp isn't going to let that happen long-term even if he tried. The limiting circuitry built-in to his amp is not a brick wall, it's a bungee cord. He has the means to brick-wall limit, but is just asking -- for practical application (hard limiters trade quality of sound for safety) and just plain curiosity -- is a bungee cord limiter sufficient?

More to the point, if it isn't sufficient, and the driver is destined to fail in short order, what fails? Not a guess, or a lecture about "don't do that" -- we know it's against the rules, and that it "might" or "will" cause damage. That's crystal clear. It's just a simple question, for those of us that are inclined to follow best practices because they are sound and reasonable, but still wonder "what if...?"

Someone has neglected the rules and paid the price. I don't think OP (nor I) has to or wants to repeat that mistake. That would be careless and wasteful. We're just curious what the inbuilt safety margins are, and what precisely happened when they were exceeded. I certainly wondered, when I had the choice to limit at 50.2v, or 48v. (I chose 48v -- who's going to know the difference anyway? But could I have used 50.2 with no worries? I don't know. Hence my interest here.)

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Re: Powersoft Digam 5000 on T48-3015LF

#29 Post by thijs666 »

Grant Bunter wrote:From what I've seen here so far, the more common driver failure in Bills designs is tearing. That may suggest over excursion is the cause, as generally, voltage has been exceeded.
I apologize for discussing this so extensive. I'm a nitpicker who's just trying to learn :P .
If overexcursion is to blame, overexcursion being driving the cone beyond Xmech, and limiting at 60V prevents that, it may suggest that the coil already left the linear magnetic field of operation and is already playing in its non-linear area where Xmax < cone travel < Xmech before the voltage reaches 60V, meaning power compression has already set in quite severe even before hitting the 60V limit, right? In this case it would be safe to say it's mandatory to limit at 60V. So far it's obvious :bash: .

But if one were to assume that the 60V limit is set according to Xmax and NOT Xmech, which I believe would be the right parameter to specify the maximum allowable voltage by, one could argue there's a little safety margin built in, namely from 9.6 mm of cone excursion (Xmax) to 17 mm (Xmech or Xlim). Right?

So this lead me to think about that 60V limit: If it is Xmax that dictates 60V, then in my opinion, the cone being strong enough to withstand the high air pressure occurring in the horn, it would be safe to say musical peaks above 60V are allowable, as long as thermal heating of the coil and magnet structure stay in the safe zone. I.e. the coil, surround or spider would not be damaged if excursion stayed < 17 mm. Thermally the drivers spec sheet allows for this (450Wrms (~60V) and 900W Peak (~85V) (EIA 426A noise source)).
But if it is Xmech (Xlim) that dictates the 60V (give or take a few safety-volts), than there's simply no headroom left and 60V is the brick wall beyond which the magic smoke is released from the coil.
Grant Bunter wrote:Why try to squeeze an extra (maybe) 2-3dB from what you have (which is roughly equivalent to 1 cab), with a possible consequence of driver failure, when you could build 2 extra cabs and add 6dB?
Practical as well as musical: using the amps limiter would offer a little more headroom and a cleaner sound (while still limiting continuous RMS power). Other than that, it triggered my thoughts on the limiting factor, as I've been trying to explain.

At this point I think only Bill (or anyone who has the correct software and horn model of the T48) can help out...

Awaiting the :horse: .

P.S., I must say I like to discuss this kind of things on a forum like this, where contributions make sense and not just bash the OP or any other comments :clap: .
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

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Re: Powersoft Digam 5000 on T48-3015LF

#30 Post by thijs666 »

SirNickity wrote:Sure, but that's not at all the point of this. I know that's usually why someone will ask, but his amp isn't going to let that happen long-term even if he tried. The limiting circuitry built-in to his amp is not a brick wall, it's a bungee cord. He has the means to brick-wall limit, but is just asking -- for practical application (hard limiters trade quality of sound for safety) and just plain curiosity -- is a bungee cord limiter sufficient?

More to the point, if it isn't sufficient, and the driver is destined to fail in short order, what fails? Not a guess, or a lecture about "don't do that" -- we know it's against the rules, and that it "might" or "will" cause damage. That's crystal clear. It's just a simple question, for those of us that are inclined to follow best practices because they are sound and reasonable, but still wonder "what if...?"

Someone has neglected the rules and paid the price. I don't think OP (nor I) has to or wants to repeat that mistake. That would be careless and wasteful. We're just curious what the inbuilt safety margins are, and what precisely happened when they were exceeded. I certainly wondered, when I had the choice to limit at 50.2v, or 48v. (I chose 48v -- who's going to know the difference anyway? But could I have used 50.2 with no worries? I don't know. Hence my interest here.)
Been typing too slow during my previous post :oops: .
But you're right, that's what it boils down to in the end: is a bungee cord limiter :D sufficient? (but I wouldn't mind a little elaboration on the why).
BF cabs built to date:
2x T48 21" 3015LF; 1x T48 24" 2xBP102; 1x DR250 2510 loaded, cross firing; 4x DR200 Beta 8, melded array; 1x TT HL-10c; 2x WH Beta 8, melded 'array'; 3x AT 15" Tang Band W8-740P; 1x AT 15" JBL GTO1014

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