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21'' HOG SCOOP desing help

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turbo7 View Drop Down
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    Posted: 25 January 2018 at 8:56am
of course, agree with you both,

thats why i was referring to nonlinear parameters...

TSP change with heat ! TSP are based on small signal at Fs... Still, i have done a lot of measurements of frequency response and it is really close to the simulation. I use Ajhorn, Hornresp, Akabak. Of course, only at low power levels, measurements are accurate.

BUT: in real world, even with high power levels, depending on crest factor, the coils STAY COOL. If we have a bassdrum impulse f.ex. with 1kw input, coil will not heat up ! 

When we look at the heating up of a coil, qes will rise and everything else will change.

I would never stick V-18 1200 in a small chamber.


Edited by turbo7 - 25 January 2018 at 8:57am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tv00 Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2018 at 10:16pm
Whow, there's a like button in there.
You're so right, these driver specs annoys me a bit, that's why u always gotta try too! I sim first (cheaper & easier) well for the rcf mb15n401 I had in turbobass they simmed best, sounded best (blindtest) & measured best. BUT I never made the best peak performance test :-)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2018 at 2:09pm
Originally posted by levyte357- levyte357- wrote:

Originally posted by turbo7 turbo7 wrote:

Most of the time sims are very accurate,


EDIT:With regards to Scoops, Sorry, I have to disagree with this.

The displacement sims maybe OK, but if you sim a Void V18-1200, in a number of small chamber Scoop designs, it will produce plots saying all is fine and dandy.

Try it in reality, and it sounds crap.

Put the same driver in Medium chamber Scoop/Mini Scoop, with matched throat, and uber smooth notes.

Idenitified/Demonstrated this, 11x years at a Scoop test.  Think I was the first person in London to demo a V18-1200, the pic on PAP site, was the driver sitting on my dining table!!!

Anyway, all I'm saying is, grounded understanding of driver T/S parms, is better method of matching Scoop chambers/throats, to certain driver.

Even though widely available drivers, may have inaccurate T/S, compared to drivers custom made for Large PA firms.




People have to understand that the T/S parameters are a fit to a relatively simple lumped model of a loudspeaker resonating electrically and mechanically. They are only valid for SMALL signals. SMALL!!! And they assume that the modeled system behaves in a linear manner.

T/S never have, and never will be able to predict the behavior of a large signal. They tell you nothing about the drivers non-linear behaviour under large signals. They tell you nothing about the behavior of your proposed cabinet's airflow under large driver excursion.

For large signals the T/S are just a guideline of what you might hypothetically be able to expect, if all is perfect.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 24 January 2018 at 11:35am
Originally posted by turbo7 turbo7 wrote:

Most of the time sims are very accurate,


EDIT:With regards to Scoops, Sorry, I have to disagree with this.

The displacement sims maybe OK, but if you sim a Void V18-1200, in a number of small chamber Scoop designs, it will produce plots saying all is fine and dandy.

Try it in reality, and it sounds crap.

Put the same driver in Medium chamber Scoop/Mini Scoop, with matched throat, and uber smooth notes.

Idenitified/Demonstrated this, 11x years at a Scoop test.  Think I was the first person in London to demo a V18-1200, the pic on PAP site, was the driver sitting on my dining table!!!

Anyway, all I'm saying is, grounded understanding of driver T/S parms, is better method of matching Scoop chambers/throats, to certain driver.

Even though widely available drivers, may have inaccurate T/S, compared to drivers custom made for Large PA firms.




Edited by levyte357- - 24 January 2018 at 12:21pm
Global Depopulation - Alive and Killing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote turbo7 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 4:47pm
To achieve the response i posted on page 8, the BC requires eq ( to get flat response with low qes high BL drivers it is a must ) that draws more power. I have simulated both with 1000W. The PD2150 did not need any EQ to achieve the plotted response and any EQ would have driven the cone out of xmax. Have a look at the "driver power" picture.

Edit: An Re= 5 Ohm f. ex. means, that this driver will draw more current than an 5,52 Ohm PD2150  and will heat up more because of that.



Does someone know what kind of coil winding PD uses ? I do not think its a 4-layer coil ?! Inside outside winding ? Plays a part of the cooling process, also. The whole motor and magnet structure is important to the cooling effect of the coil.



nice one genOme. Here is some literature.

https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/Harman_Int'l/AES-Other_Publications/LS_Heat_Dissipation-Thermal_Compression.pdf

Interesting thoughts regarding long Al coils in there !

https://link.springer.com/article/10.1007/BF00870404

mathematical description



What to take account in general, Neodymium loses 3% of B in field forever, everytime they are getting very hot ! Do it 10 times and you have got a serious problem there ! Driver probably not useful anymore.


Some more to read !

https://books.google.de/books?id=n2XaBwAAQBAJ&pg=PA53&lpg=PA53&dq=crumax+355+neodym&source=bl&ots=qELSZVQx9I&sig=-hK3BfYZuVjVpIQszvMiTJ5hglI&hl=de&sa=X&ved=0ahUKEwjHkrrkxOzYAhUQ56QKHZBZDGkQ6AEIKzAA#v=onepage&q=crumax%20355%20neodym&f=false

PAGE 53


Edit: I have just calculated the coil surface area of DS115 and PD2150.

2*pi*r*h = 2*pi*(0,116/2)*40 = 14,57 = DS115
"                          0,152/2)*30 =  14,32 = PD2150

So we see, even it is a 4,5" vs 6" coil,  the 4,5" coil has a larger surface area and therefore the coil runs cooler, AND it is made from Al which is heating up slower than CU. But for sure, this does mean not too much. The larger cone area can be worse in heat dissipation or vice versa. The other motor parts need to be considered, too.

Real world experience is, Al voice coils can be tricky once they heat up because they also do not cool down anymore and this provoces failure. Cry



Edited by turbo7 - 22 January 2018 at 10:24pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 4:04pm
Right factors are contradictory.
B&C wins:
Air cooling gaps: 1 type vs 3 types
Cone movement: shorter vs longer
PD wins:
Gap height: 15mm vs 14mm
Voice coil: 6" vs 4,5"
Thermal capacity: 32kg vs 12kg overall weight.
Voice coil material: copper vs aluminium

What do you mean with power consumption?
That PD has RMS 1kW and B&C 1700W? Than looking at technologies is pointless and we could get manufacturers power compression values but they wont ilustrate the enclosure diffrences.
Also B&C has higher efficiency so it will generate less heat at same input power.

Edited by gen0me - 22 January 2018 at 4:22pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote turbo7 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 2:48pm
its 4,5" Al vs 6" Cu coil, depends also on the height of the top plate and how much heat it takes off, excursion and cooling system in general plays a part. The 18" we have simmed here consumes more power so it will have more PC. This is only estimated - hard to calculate.

Edit: Of course we have Re=5 Ohm and Re= 5,52 Ohm for the 2150. That alone makes a difference in power consumption when run off the same amplifier.


Edited by turbo7 - 22 January 2018 at 8:44pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 1:53pm
Originally posted by Tonskulus Tonskulus wrote:

X1's are prone for driver failures, according to rumors.. 

Every bandpass will be comparing to tapped horn. Due to excursion.
Btw shouldnt power compression be lower on 18" than on 21" if both are within their xmax? 18" will move more so has a better cooling of a voice coil.
If you can interpret horn resp and have comparison to designs in real world you can predict its sound. But you need impulse response
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Post Options Post Options   Thanks (0) Thanks(0)   Quote turbo7 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 1:01pm
PC = Powercompression, but yes, also due to less power consumption :-)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tv00 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 12:44pm
PC=Power Consumption? :-)
I agree to both, I always do sims first, but at sims will also show things start happening when full powered & hitting xmax, add to that real life powercompression & other factors, yet I've also seen cabs dropping lower in real life than sims :-)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote turbo7 Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 12:35pm
I have built and sold around 100x18" scoops so far, 5 different designs, many different drivers. i have always made my prototypes according to sims with different software and of course a lot relies on the cooling system and BL behaviour how a scoop "sounds" and which SPL it produces. Nonlinear parameters ! Still, i see so many people talking and talking - i make a step to my cnc and just cut a prototype...Wink

In reality, the PD2150 will be close to the output of the 18DS115, due to way less PC.  

Most of the time sims are very accurate, of course there is a lot more to it, but gets one in the right direction.

I dont take sims as the holy grail ! But my experience with all bespoken scoop drivers is always the same. I am always right, i was right years ago with the 9600 ( i built the FIRST scoop with it )the 9600 was mashed down by the "keyboard warriors", took a few years for them to realise that their PD and turbomax game has changed. 

For given Volume, a scoop like cabinet with PD2150 is just an average design. But with nice sound characteristics !Check it in reality - if it is not enough go for stronger drivers..




Edited by turbo7 - 22 January 2018 at 12:43pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2018 at 11:21am
Originally posted by levyte357- levyte357- wrote:

I know a few sound system crews, who bought cabs, based on sims and 1W/1M charts, and demos of 1x cab in workshop, where sim/plot promised response flat down to 30Hz, from 1x cab.

Then in reality, 4x cabs in a stack failed to hit below 50hz, at high power.
Trying to extract more, resulted in driver failure.

So keep your sims and 1W/1M charts, I'll use my "ears", to compare cab combinations, when at gigs.

For my personal testing, I'll use Sig gens/Music with spectrum analysers, to estimate cab usable sub range..

Wink

X1's are prone for driver failures, according to rumors.. 

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