THAM15 - a compact 15" tapped horn - Page 32 - diyAudio
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Old 18th February 2014, 01:37 AM   #311
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by Dominik H View Post
But with a 25Hz 12db high pass, nearly 3db will be cut at 30Hz, so the speaker works in safe area. -3db = half the power. With 70V at 30Hz it still will be safe. Better would be a 35hz high pass with 24db, but this is not integrated in the plate amp I want to use. With the plate amp I could drive to subs.
Hi Dominik,

You will need a 24dB/oct @ 36Hz or 12dB/oct @ 43Hz, for the original Tham15. Max excursion will be reached @ 68,61V in theory for your driver.
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Old 18th February 2014, 05:52 AM   #312
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There is a key statement here, and it came from Djim, and it is "in theory".

The music signal is far more complex and diverse to be determined with any grater certainty in simulations, the simulation shows the correct state in theory, hence the term simulation, and i have no reason to doubt them.

It is an old disussion, and it keeps coming back to the fact that real world results do not correspond to that shown in simulations with regards to excursion in real world usage.

Or what about the person firmly beliving that the xmax was reached at 500W, that was what the sims said, and math is never wrong (correct, it is not, but our interpretation of it might be) or the person feeding 1300W (93 V) into a B&C 15PS100 with great results during a whole season, all in the same design, THAM15, and with simillar drivers.

Take the excusrion simulation results for what they are, a mathematical theoretical representation, and by all means, if you use your speakers in theory then that's what you will get, otherwise I would not worry to much about it, alternativly choose a more suitable driver.
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Old 18th February 2014, 08:22 AM   #313
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Originally Posted by Djim View Post
Hi Dominik,

You will need a 24dB/oct @ 36Hz or 12dB/oct @ 43Hz, for the original Tham15. Max excursion will be reached @ 68,61V in theory for your driver.
Yes, I should use a filter like mentioned above.
But the plate amp has a fixed filter, and all I want to be sure is that the coil doesnīt hit metal. Excursion one way is over all 19mm. I do not bother if this is Xmax or Xlim.

I know that the excursion calculation ist only in theory.
With power compression an other losses there should not be any problem with the driver (BC 15NA100) I want to use. Thatīs all the math tells me.

After I build the cabinet I will test it to the limits of the amp, and if there is any excursion problem at any frequency I will change the amplification. But I want to try at first the plate amp I already have, because it can drive two Subs. Iīm using the same plate amp already for two 3015LF in Reflex loaded cabinet and have no excursion issus.

The single Tham15 should replace two nearly 10 year old D.A.S. Audio SUB18A.
Less space, less weigth, (I bougth the version made of MDF, 45kg), and nearly the same output.
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Old 18th February 2014, 08:36 AM   #314
djk is offline djk
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Consider 40hz and 80hz tones mixed 1:1 with a drive level of 80V.

The low tone will require 40V of the drive, the upper tone the other 40V.

The woofer will travel X at the low tone, and 1/4X on the high tone.

If we call X 8mm, the total excursion would be 10mm.

If all 80V went in on the low tone the excursion would be 2X.

Unless playing sine tones, excursion shouldn't be a problem. Even the 'music' that sounds like swept sine tones has strong harmonic content. A low E played on a Fender P bass has a second harmonic that is over 6dB higher than the fundamental (have seen 9dB).

This is just a 'theory', but it does seen to fit the facts.
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Last edited by djk; 18th February 2014 at 08:39 AM.
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Old 18th February 2014, 10:13 AM   #315
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This sub will be used only 8 days a year.
Therefore the driver can be driven near to itīs mechanical limits. Knowing that spl will not increase much and the sound will not get better with more excursion.
The only thing that I really care is that the driver can handle full power without the coil hitting the plate, that is what I will with swept sine wave test after building the cabinet.
If the sexcursion will be near simulation than everything is ok. If I mesure more excursion I have to change the amp and highpass filter.

I managed only to wreck one driver a few years ago when I changed amping from a Mackie M1400 to a Behringer EP2500 and trustet the 30Hz highpass written in the manual.
After I took out the destroyed driver , I measured the filter and found out that the highpass settings produced a 5 db peak at 32Hz, which made the coil hit the plate.
Since there I always double check everything.
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Old 15th June 2014, 10:47 AM   #316
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does anyone have a real or rough weight estimate for one of theses? Is it lift-able on your own?

If it is manageable I plan to load a pair with B&C 15SW115!

Last edited by reminence; 15th June 2014 at 11:05 AM.
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Old 15th June 2014, 10:55 AM   #317
jsk is offline jsk
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I have tham15's with both ferrite and neo drivers. Both are one man lifts although neo drivers are much easier especially on stairs.
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Old 15th June 2014, 11:17 AM   #318
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Originally Posted by jsk View Post
I have tham15's with both ferrite and neo drivers. Both are one man lifts although neo drivers are much easier especially on stairs.
And with that, I will order some drivers
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Old 15th June 2014, 11:19 AM   #319
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Originally Posted by reminence View Post
does anyone have a real or rough weight estimate for one of theses? Is it lift-able on your own?

If it is manageable I plan to load a pair with B&C 15SW115!
It will be in the range of 40-50 kg (90-110lbs), depending of driver and wood used.
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Old 15th June 2014, 12:00 PM   #320
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Hmm, not as light as I would like. I wonder if thinner wood with more bracing would work. Or a slim version loaded with a 12.
35kg is a rough target like a tham12 with 10hz more extension.

Last edited by reminence; 15th June 2014 at 12:05 PM.
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