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Old 28th December 2011, 07:10 AM   #2501
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Hi amjulio,

Quote:
Originally Posted by amjulio View Post
ripple shouldn´t increase when output power is increased
You have assumed that the acoustical output power is increased by a constant K watts, independent of frequency. Because the load is a complex impedance (it has resistive and reactive components that both change with frequency) the acoustical output power varies considerably with frequency - even though the electrical input power is a constant 1 watt (in your example).

For the normal constant voltage SPL response, the acoustical output power also varies with frequency - but by a different amount to that obtained when the Maximum SPL tool is used.

This is why the ripple amplitude changes.

Quote:
Originally Posted by amjulio View Post
I wonder if your last remark explain ripple increment.
It was intended to support my earlier comments in the post, yes.

Quote:
Originally Posted by amjulio View Post
What is SPL Maximun for?. Because normal power amplifiers have constant voltage outputs. So the normal output of Hornresp models better reality I think. Am I wrong?
The Maximum SPL tool shows the overall performance envelope of the loudspeaker when limited by either the driver rated thermal input power Pmax or the diaphragm linear mean-to-peak displacement Xmax. You are correct in thinking that the standard constant voltage SPL response provides a more realistic prediction of how the loudspeaker will perform in practice under normal conditions.

Kind regards,

David
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Old 28th December 2011, 09:52 AM   #2502
amjulio is offline amjulio  Argentina
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Thanks Dave.

It's clear now for me: costant electrical power on variable (with frequency) efficiency implies variable SPL. Makes sense.

I think I have finished the design of the underground horn for my new house
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Old 29th December 2011, 03:54 AM   #2503
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Quote:
Originally Posted by amjulio View Post
I think I have finished the design of the underground horn for my new house
Hi amjulio,

It's magnífico :-).

Kind regards,

David
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Old 29th December 2011, 04:23 AM   #2504
amjulio is offline amjulio  Argentina
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Quote:
Originally Posted by David McBean View Post
Hi amjulio,

It's magnífico :-).

Kind regards,

David
18.000cm2 horn will "emerge" in a corner through a 1,8m2 wire mesh triangle

Click the image to open in full size.
iron mesh
the triangle in the corner will be covered with this mesh.

I got decent results with ML-8P150 MID-BASS8"PROFESIONAL (Bl = 13,58 Tm) and also with
Click the image to open in full size.

B-6K BASS6"KEVLAR (Bl=11,35 Tm)


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Old 29th December 2011, 04:39 AM   #2505
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Quote:
Originally Posted by amjulio View Post
18.000cm2 horn will "emerge" in a corner through a 1,8m2 wire mesh triangle

Click the image to open in full size.
iron mesh
the triangle in the corner will be covered with this mesh.

I got decent results with ML-8P150 MID-BASS8"PROFESIONAL (Bl = 13,58 Tm) and also with
Click the image to open in full size.

B-6K BASS6"KEVLAR (Bl=11,35 Tm)


It doesn't matter if you use a front loaded horn, a back loaded horn, a bandpass subwoofer, a sealed box, a vented box or a tapped horn:

At low frequency, maximum output is limited by displacement.

That's why I'd strongly discourage you from building such a complex enclosure for an 8" woofer. You'll be severely limited by displacement.

I'm using a pair of twelves in a 350lb tapped horn, and it's working pretty well. At these output levels the enclosure stiffness becomes a big factor.
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Old 29th December 2011, 05:13 AM   #2506
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Quote:
Originally Posted by Patrick Bateman View Post
At low frequency, maximum output is limited by displacement.
Unless, of course, the horn is adequately sized to act as an acoustic transformer, in which case power may become the limit instead.
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Old 29th December 2011, 05:28 AM   #2507
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Quote:
Originally Posted by 454Casull View Post
Unless, of course, the horn is adequately sized to act as an acoustic transformer, in which case power may become the limit instead.
amjulio's woofer has 3mm of xmax :

B-6K | GB-AUDIO

Click the image to open in full size.
IMHO, investing the time and expense in building such an elaborate horn will yield substandard results. Horn's can't work miracles. To make bass, you need displacement. 3mm won't cut it.
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Old 29th December 2011, 10:31 AM   #2508
Kolbrek is offline Kolbrek  Norway
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Quote:
Originally Posted by Patrick Bateman View Post
IMHO, investing the time and expense in building such an elaborate horn will yield substandard results. Horn's can't work miracles. To make bass, you need displacement. 3mm won't cut it.
Patrick: by substandard results, do you mean because of the elaborate horn, or because of the driver?

amjulio: I would say that if you put that much work into building a horn subwoofer, you really owe yourself to drive it with a high quality woofer that can provide enough volume displacement. 3mm can work if the diaphragm area is large enough, but an 8" driver is too small for subwoofer use, even with a horn.

I have built horn subwoofer using single 10", 15" and double 12". Use 15" or (double) 12", 10" is too small. Maybe one of the long-throw woofers could work, but I would rather go for smaller displacement and larger area.

Regards,
Bjørn
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Old 29th December 2011, 02:46 PM   #2509
amjulio is offline amjulio  Argentina
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Default area needed

I agree: we need to move volume to get the SPL we want. The lower frecuency we want our SPL the more volumen we have to move.

I made my math.

An educated guess (see below) tells me I'd got divorce if I pretend more than 70 fon in my house. 70 fon at 25 Hz implies SPL < 90 dB (see fons.gif).

I'm getting more than 110 dB (SPL.png) with Xmax = 1,84 mm (diplacement.png)

Simulating with option SPL maximun @ P=1W =constant frecuency limit is 23Hz (see displacement @ SPL Maximum.png). Go beyond driver limits implies to feed Eg = 4,7575 V to get 114 dB of SPL, but 114 dB of SPL is close to the pain limit!!!.

So, it seems design is more robust than my ear and 54 dB more resistant than my marital status
An educated guess on complaints.

From Beranek, Acustics, Fig 13.22 I adopt noise rating D (mild complaints) to E (strong compliants).
From Fig. 13.23 we see maximun SPL @ 20-75 Hz band for D rating is 74 dB and for E is SPL = 77 dB i.e. 50..60 fon. I adopt loudeness = 70 fon
Attached Images
File Type: gif fons.gif (84.2 KB, 28 views)
File Type: png SPL.png (5.4 KB, 38 views)
File Type: png displacement.png (5.6 KB, 36 views)
File Type: png displacement @ SPL Maximum.png (13.1 KB, 31 views)
Attached Files
File Type: txt ml-8p150.txt (455 Bytes, 5 views)
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Old 29th December 2011, 03:29 PM   #2510
AndrewT is online now AndrewT  Scotland
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Note that at 100 to 110dB that the phon to spl are nearly equal and nearly constant over the whole audio range from 20Hz to 1000Hz.

If you can achieve a peak 110dB SPL target, then that same target applies to all frequencies <=1kHz.

That 110dB target would allow average listening levels of 80dB to 100dB depending on music type and not clip any signals <110dB

For most well recorded music an average level of 90dB is very loud.
I often listen at average levels around 70dB.
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Last edited by AndrewT; 29th December 2011 at 03:32 PM.
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