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Old 24th April 2011, 12:15 AM   #1011
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by Dave NonZero View Post
In Tb46s post #997 I think, the graphs show the comparison between the 18sound and the 3015lf. It's a few db down at 60 but has a bit more extension. I'll just have to build one and test it I suppose.
Before you test it you need to look at a few things first. The SS15 is designed for a driver with a relative low BL driver. When you are going to use a high BL driver in such design it may show acceptable SPL predictions but you also need to pay attention to Group Delay.
In case of an optimised TH for low BL drivers you will often see a peak in group delay at max excursion point when you fit them with a high BL driver. For a cheap driver it may be acceptable but high BL drivers are often expensive. So would you like to use an expensive driver, such as the 18Sound, in a non optimised cab?
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Old 28th April 2011, 08:49 AM   #1012
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Quote:
Originally Posted by CRESCENDO View Post
...while exceeding xmax by 3mm, no? I believe you have to reduce input power to 200W to bring the displacement to the rated/published xmax (which in turn brings down SPL quite a bit...).

If all of the sub-$200 3015LF's go bye-bye, I think the next best bet (response wise) would be the RCF L15P200AK 15" Woofer at $259/ea or even better, the 4 ohm variant -- IF you can find it in the states.
Quote:
Originally Posted by jbell View Post
run the hornresp for the kappa pro 15lf... it runs lower xmax while producing within a db of the same sound. It stays within xmax at 63v
Sooo, turns out I had a different spec sheet for the Kappa Pro 15LF-2 than the one I just dwnloaded...

BUT, I show xmax (6.7mm) being exceeded at 59Hz when using 63v (9.74mm)... Do I have my enclosure specs off or am I missing something else?...
Attached Images
File Type: jpg IN SS15 Kappa Pro-15LF-2 soho54's corner.jpg (99.0 KB, 676 views)
File Type: jpg DIS SS15 Kappa Pro-15LF-2 soho54's corner excd x@59Hz 450W.jpg (83.5 KB, 671 views)
File Type: jpg Kappa Pro-15LF-2.jpg (241.2 KB, 669 views)
File Type: jpg Kappa Pro-15LF2.jpg (243.3 KB, 647 views)
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Old 28th April 2011, 04:58 PM   #1013
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by CRESCENDO View Post
Sooo, turns out I had a different spec sheet for the Kappa Pro 15LF-2 than the one I just dwnloaded...

BUT, I show xmax (6.7mm) being exceeded at 59Hz when using 63v (9.74mm)... Do I have my enclosure specs off or am I missing something else?...
You seem to use the old specs of the driver that show better Thiele-Small parameters.

The Kappa Pro-15LF-2 at 53 volt has a theoretical HornResp excursion of 10,5mm. The reality is this drivers suffers from at least 3dB pwr/dyn compression at Xmax. This means you will need twice the power to reach Xmax in reality.

Xmax theoretical = 40V at 6,12Ohm = 265Watt
Xmax theoretical -3dB pwr/dyn compression = 530Watt

Like I said at LEAST 3dB so powering this driver to its 600 watts continues power rating is absolutely NO problem!

That's why I said people are way to much concentrating on theoretical Xmax while they don't seem (or want?) to understand the impact of power/dynamic compression. Although I never work with Eminence the 3dB seems to be the (lowest) value I get from other users.
As far as I know only RCF and 18Sound include pwr compression data with their drivers.

Last edited by Djim; 28th April 2011 at 05:07 PM.
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Old 28th April 2011, 06:37 PM   #1014
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by Djim View Post
The Kappa Pro-15LF-2 at 53 volt has a theoretical HornResp excursion of 10,5mm.
Sorry, should be 63V for 10,5mm
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Old 28th April 2011, 09:39 PM   #1015
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Oh, wow. Great to know - thank you! (off to do research on how to calculate pwr/dyn compression for all my previously-poor-performing drivers now)
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Old 28th April 2011, 09:57 PM   #1016
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by CRESCENDO View Post
Oh, wow. Great to know - thank you! (off to do research on how to calculate pwr/dyn compression for all my previously-poor-performing drivers now)
I'm afraid it doesn't work that easy. Every type of driver has different pwr/dyn comp levels. Also the design of the cab influence this point. In case of the SS15 where its 1/3 wavelength is above the Fs of the driver in free space, the excursion behaves just like under normal circumstances and therefore pwr/dyn comp levels are very similar to basreflex (or 6th order designs if you want to be more precise). If your TH's 1/3WL is much below the Fs of the loudspeaker in free space, the pwr comp levels will be lower as max excursion will be reached with much less power.

Power compression is coupled to power input of the driver.
Dynamic compression is coupled to the physical excursion of the driver.

The problem is every Brand uses their own method of calculating Xmax and since they are often not coupled to distortion or pwr comp figures it is difficult to predict these levels. That's why I stated my info the "at least 3dB for 3015lf" is based on information from 3th parties. That power and dynamic compression is important is also the reason why some less high Xmax drivers can perform much better in reality. Therefore using Xmax and calculating max excursion as absolute variables will not give accurate results and can be far from reality.


Last edited by Djim; 28th April 2011 at 10:08 PM.
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Old 28th April 2011, 10:13 PM   #1017
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by CRESCENDO View Post
I think the next best bet (response wise) would be the RCF L15P200AK 15" Woofer at $259/ea
That's why I would like to see a direct comparison between the 3015lf and the old RCF classic L15P200AK. Both driver have similar specs when it comes to Xmax and Xlim but it wouldn't surprise me to see the RCF outperforms the 3015lf in max SPL (and not by just a couple dB's or sound ).

Last edited by Djim; 28th April 2011 at 10:15 PM.
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Old 29th April 2011, 08:07 PM   #1018
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Quote:
Originally Posted by Djim View Post
In case of the SS15 where its 1/3 wavelength is above the Fs of the driver in free space, the excursion behaves just like under normal circumstances and therefore pwr/dyn comp levels are very similar to basreflex (or 6th order designs if you want to be more precise). If your TH's 1/3WL is much below the Fs of the loudspeaker in free space, the pwr comp levels will be lower as max excursion will be reached with much less power.
So, since the L15P200AK's Fs is even lower than the 3015LF's, does this suggest its pwr comp levels will be higher and xmax will take much more power to reach?

Quote:
Originally Posted by Djim View Post
That's why I would like to see a direct comparison between the 3015lf and the old RCF classic L15P200AK. Both driver have similar specs when it comes to Xmax and Xlim but it wouldn't surprise me to see the RCF outperforms the 3015lf in max SPL (and not by just a couple dB's or sound ).
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Old 29th April 2011, 09:36 PM   #1019
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In the UK the Eminence 3015lf is currently retailing at about £137
As an alternative I think that the Precision Devices 15" Neo. PDN15BR40 looks to be a good match. It retails at approx £158, is rated at 700W AES, & has a X max of 10.5mm. Maybe more importantly it has a 4" voice coil compared with the Eminence 3".
As usual no figures for thermal compression.
The only quoted thermal compression figures I can find on Precision Devices site are for the PD1850 18" (1.6db at 800W) and the PD1851 (1.7db at 1000W)
The low thermal compression of the PD 18" drivers is no doubt helped by the 5" voice coils.
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Old 30th April 2011, 12:41 AM   #1020
Djim is offline Djim  Netherlands
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Crescendo, I have to apologise for my fuzzy explanation. Besides the language barrier and between all kinds of work, it still difficult to explain in a few words but Iíll try.When people (including myself) talk about power compression it is not always clear what part of the pwr comp. they are referring too:

1.) Thermal power compression: which is the result of electrical values. More power input means more temp rise (which leads to increase of resistance and such)

2.) Dynamic power compression: which is the result of physical values. The higher the excursion becomes the higher the dynamic power compression values become.

When a driver is forced to go below its own Fs excursion will (dramatically) rise as frequency drops. When the driver Fs is higher than the Fs of the system, the Xmax will be reached with less power. But the confusion started when I stated
Quote:
Originally Posted by Djim View Post
If your TH's 1/3WL is much below the Fs of the loudspeaker in free space, the pwr comp levels will be lower as max excursion will be reached with much less power.
Instead I should have stated: If your TH's 1/3WL is much below the Fs of the loudspeaker in free space, the thermal pwr comp levels will be lower as max excursion will be reached with much less power. The dynamic compression figures will be higher as max excursion will be reached with less power.

Now back to your question;
Quote:
Originally Posted by CRESCENDO View Post
So, since the L15P200AK's Fs is even lower than the 3015LF's, does this suggest its pwr comp levels will be higher and xmax will take much more power to reach?
No, I expect the L15P200AK with its lower Fs will have less thermal power compression then the 3015lf at the same power in a SS15. Besides power compression I do have my doubts about the 3015lf Xmax data as given by Eminence. Nobody seems to know how Eminence today calculates their Xmax any longer.What I do know is what people show me in their measurements and these give me reasons to believe that the total power compression figures are higher then 3dB at Xmax.

Therefore I would like to see a side by side comparison of an SS15 loaded with 3015lf and L15P200AK.

Hopefully this makes more sense and is less confusing
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