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Old 30th January 2013, 12:50 AM   #91
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Quote:
Originally Posted by Xoc1 View Post
The Tham 12 is tiny.
On Martinsons blog the Tham12 is shown with a sim of over 88 litres
This is despite the actual internal volume being 74.3 litres without any bracing or driver!
The path length is also shorter than shown on the blog.
With the PD 12SB 30 I would expect 98db at 75hz in a 2pi sim
Have not unfolded the MTH30 yet!
Regards
Xoc1
Ah, that might explain the difference. I haven't seen any measurements of actual THAM12 builds, only variations on the design similar to what I've discussed.
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Old 30th January 2013, 01:13 AM   #92
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by Xoc1 View Post
On Martinsons blog the Tham12 is shown with a sim of over 88 litres. This is despite the actual internal volume being 74.3 litres without any bracing or driver! The path length is also shorter than shown on the blog.
With the PD 12SB 30 I would expect 98db at 75hz in a 2pi sim.
Hi Xoc1,

I agree with your model. Based on measurements of the Tham12 I found on another forum I made a re-model. The measurement was done with a 18Sound 12LW1400 driver which I used to re-model it.

Click the image to open in full size.



If you use the input of the old version of the PD.12SB30:

Click the image to open in full size.



And for the newer version of the PD.12SB30;

Click the image to open in full size.

Last edited by Djim; 30th January 2013 at 01:16 AM.
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Old 30th January 2013, 02:13 AM   #93
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by tb46 View Post
Would the cone correction (throat correction) be applicable to the Tham series of THs?
Hi Oliver,

Now I have re-modelled the Tham12 I can show, by decreasing S2 (Cone-Volume-Correction), how it improves the dip.

For those (some Swedish members ) who assume that cone-volume-correction adds significant compression to the system, please take a good look at the pressure and velocity models! Like the model shows, cone-volume-correction has no significant effect on pressure while it only increases velocity! In my view, this also shows why Danley 'gets away' with his V-stub without adding too much compression.

Click the image to open in full size.

Last edited by Djim; 30th January 2013 at 02:19 AM.
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Old 30th January 2013, 05:23 AM   #94
Chaps is offline Chaps  Denmark
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Join Date: Nov 2010
Quote:
Originally Posted by Xoc1 View Post
The Tham 12 is tiny.
On Martinsons blog the Tham12 is shown with a sim of over 88 litres
This is despite the actual internal volume being 74.3 litres without any bracing or driver!
The path length is also shorter than shown on the blog.
With the PD 12SB 30 I would expect 98db at 75hz in a 2pi sim
Have not unfolded the MTH30 yet!
Regards
Xoc1
As i am not (yet) i hornresp user, can you explain to me why you are simming with Eg: 2.35 opposed to Eg: 2.83? Isn't this the applied voltage?
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Old 30th January 2013, 05:55 AM   #95
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Quote:
Originally Posted by Chaps View Post
As i am not (yet) i hornresp user, can you explain to me why you are simming with Eg: 2.35 opposed to Eg: 2.83? Isn't this the applied voltage?
Hi Chaps,

Perhaps Xoc1 wanted 1 watt into a nominal load impedance of 5.49 ohms (the value specified for Re) rather than into the standard 8 ohms.

Kind regards,

David
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Old 30th January 2013, 06:13 AM   #96
Chaps is offline Chaps  Denmark
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Quote:
Originally Posted by David McBean View Post
Hi Chaps,

Perhaps Xoc1 wanted 1 watt into a nominal load impedance of 5.49 ohms (the value specified for Re) rather than into the standard 8 ohms.

Kind regards,

David
Ahh i see.
Maybe i have to read a bit about the difference af nominal/minimum impedance and Re.
Just thought people always simmed with 2.83V on a (nominal) 8 ohm speaker.
Will the sim be more "real-world" when using Re?

Last edited by Chaps; 30th January 2013 at 06:16 AM.
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Old 30th January 2013, 07:09 AM   #97
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Quote:
Originally Posted by Chaps View Post
Will the sim be more "real-world" when using Re?
Hi Chaps,

All it means is that for whatever reason, the simulation has been done using a constant input voltage of 2.35 volts rather than 2.83 volts. The SPL and diaphragm displacement values will be marginally less than those achieved using 2.83 volts, but this is the only impact on the results. Xoc1 may perhaps care to comment on the reason for using 2.35 volts rather than the generally accepted standard of 2.83 volts (which delivers 1 watt into an 8 ohm load).

Kind regards,

David
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Last edited by David McBean; 30th January 2013 at 07:20 AM.
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Old 30th January 2013, 10:16 AM   #98
Xoc1 is offline Xoc1  United Kingdom
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Quote:
Originally Posted by David McBean View Post
Hi Chaps,

All it means is that for whatever reason, the simulation has been done using a constant input voltage of 2.35 volts rather than 2.83 volts. The SPL and diaphragm displacement values will be marginally less than those achieved using 2.83 volts, but this is the only impact on the results. Xoc1 may perhaps care to comment on the reason for using 2.35 volts rather than the generally accepted standard of 2.83 volts (which delivers 1 watt into an 8 ohm load).

Kind regards,

David
Technically this is what is known as a late night session cockup
Regards Xoc1
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Old 30th January 2013, 10:32 AM   #99
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Join Date: Nov 2007
Quote:
Originally Posted by Djim View Post
Hi Oliver,

Now I have re-modelled the Tham12 I can show, by decreasing S2 (Cone-Volume-Correction), how it improves the dip.

For those (some Swedish members ) who assume that cone-volume-correction adds significant compression to the system, please take a good look at the pressure and velocity models! Like the model shows, cone-volume-correction has no significant effect on pressure while it only increases velocity! In my view, this also shows why Danley 'gets away' with his V-stub without adding too much compression.

Click the image to open in full size.
That sim'd FR suggests that the mouth isn't large enough.
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Old 30th January 2013, 10:42 AM   #100
Chaps is offline Chaps  Denmark
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Quote:
Originally Posted by Xoc1 View Post
Technically this is what is known as a late night session cockup
Regards Xoc1
That makes good sense to me
Guessing that will make it go around 1.5dB up from the approx. 98dBs (from your sim)
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