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Multi-Way Conventional loudspeakers with crossovers

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Old 23rd February 2004, 08:46 AM   #21
Bricolo is offline Bricolo  France
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Quote:
Originally posted by maartentje
Okay i will scan every thing about it i think tommorow its ready to post it, i will post it on my website.

again sorry for my english

Hi Marteen,

I can't access to your website ("Directory Listing Denied"), is this normal?
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Old 23rd February 2004, 08:46 AM   #22
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Location: 77.38E, 12.58N
Yes Vivek...Sorry i missed ur first post...!
I bought it from corrson..!
Any specific reason why u ask...?

Ajju
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Old 23rd February 2004, 10:17 AM   #23
Vivek is offline Vivek  India
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No, nothing in particular. Are the P17's the one for about 3500 rupees from Shiva because I saw a couple of woofers and I dont remember the model numbers. And tell me how they sound because I bought a pair of TC18WG49 (Rs. 1575 each).
Did you listen to the floorstanders he has built? He was also saying that there were several people interested in starting a DIY audio club here in Bangalore.
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Old 23rd February 2004, 04:58 PM   #24
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ya the same ones...!!
i dint get a chance to listen to his system..but he has agreed to an appointment..so let me c..!
he was not in town...so I personally collected the drivers from his place..!

ajju
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Old 23rd February 2004, 05:19 PM   #25
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Quote:
I'd say you *must* replace the load resistance with a better model so you see the results on the computer rather than in the real thing... You can ignore the RML component, and the others can be calculated from the T/S parameters.
Svante,

Please correct me if i am wrong...Looking at the equivalent circuit...we have..

Re = Dc resistance of voice coil. -> 5.8 ohms
Le = Inductance of voice coil -> .55mH
Bl = force factor...6.5
cms =
to get cms from vas is this equation correct.(if memory remains)?
vas/(1.4 * 10^5 * sd^2)
in that case...
with vas = 34.7L and sd = 136cm^2
is cms = 1.34 * 10^-6

Mms = 14g

Rms = hw to get this...
can i get it from terms like Qms, mms and Fo

Could some one tell me the formulas or pointers to them on the web please...!!

Thanks
ajju
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Old 23rd February 2004, 06:31 PM   #26
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by ajju
Sreten :


Interesting thought. Will explore the possibility..

Couple of questions...
1) If i have to re-tune the port how easy is it going to be.
2) Since the weight of the speaker is off axis i need to lower the
centre of gravity of the whole unit or provide a large base.
I had thought of putting a sandfill as indicated in the diagram...
How do i manage that if i were to use the centre of the base
as a part of the flare port.

ajju
1) I'm not too sure about, the main effect of exploiting the
flare I believe is that the port will sustain a higher velocity
before "chuffing", so you can use a smaller port.

2)
a) you can move the circular stand to below the C of G.
b) if the stand is rigididly fixed can't see the difference.
c) the circular stand is attached to an internal section that is not
the cabinet base.
The cabinet base has a single port surrounding the circular stand.
You can add sand in the base around the port as before.
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Old 23rd February 2004, 06:44 PM   #27
sreten is offline sreten  United Kingdom
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I'll also point out you can't use a circuit simulator and electrical
models of drivers for crossover design with accurate results.

The reason for this is drivers do not add acoustically the
same way they do electrically in the crossover region.

See Linkwitz/Riley crossover alignments for further details,
and electrical targets to achieve flat acoustic results.

They also ignore the acoustic effects of the mounting of the driver.

With your suggested design diffraction effects must be considered.

sreten.
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Old 23rd February 2004, 06:59 PM   #28
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yes Sreten, I agree with you...
this is just a simple start...will be building up step by step...
taking inputs from all fronts....improving by incorporating necessary corrections and ofcourse by the ear...!
but only thing is time is a bit scarce now..so the progress is a bit slow...

btw...what is your opinion on the structure....
my main worry is ...will it start behaving like a massloaded TL at some mid bass freq, instead of the BR i'm intending...
in that case it is likely to generate some nasty peaks...!
so a bit confused now..!

ajju.
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Old 23rd February 2004, 07:38 PM   #29
Svante is offline Svante  Sweden
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Quote:
Originally posted by ajju


Svante,

Please correct me if i am wrong...Looking at the equivalent circuit...we have..

Re = Dc resistance of voice coil. -> 5.8 ohms
Le = Inductance of voice coil -> .55mH
Bl = force factor...6.5
cms =
to get cms from vas is this equation correct.(if memory remains)?
vas/(1.4 * 10^5 * sd^2)
in that case...
with vas = 34.7L and sd = 136cm^2
is cms = 1.34 * 10^-6

Mms = 14g

Rms = hw to get this...
can i get it from terms like Qms, mms and Fo

Could some one tell me the formulas or pointers to them on the web please...!!

Thanks
ajju
The formula for Cms os OK, but you have to enter volume in cubic metres and area in square metres. Then you end up with Cms=1.3e-3 m/N Check: This would lead to an fs of the driver of 1/(2*pi*sqrt(1.3e-3*14e-3))=37.3 Hz, is that right?

Also, since Qms=ws*Mms/Rms, Rms=2*pi*fs*Mms/Qms. Assuming a Qms of, say 5, this would mean that Rms is 0.66 Ns/m, and that Bl^2/Rms=6.5^2 / 0.66=64 ohm.

Quote:
Originally posted by sreten
I'll also point out you can't use a circuit simulator and electrical
models of drivers for crossover design with accurate results.

The reason for this is drivers do not add acoustically the
same way they do electrically in the crossover region.

See Linkwitz/Riley crossover alignments for further details,
and electrical targets to achieve flat acoustic results.

They also ignore the acoustic effects of the mounting of the driver.

With your suggested design diffraction effects must be considered.

sreten.
Well, *some* sort of circuit simulator must be used, right? In what way do you mean that the drivers don't add the same way as in the electrical world? Are you talking about a delay between the woofer/tweeter? And of course, the baffle step will not be seen in this simulation. Is there anything more that I don't know of?
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Old 23rd February 2004, 08:08 PM   #30
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Svante
Well, *some* sort of circuit simulator must be used, right? In what way do you mean that the drivers don't add the same way as in the electrical world? Are you talking about a delay between the woofer/tweeter? And of course, the baffle step will not be seen in this simulation. Is there anything more that I don't know of?
True, the good simulators add acoustic modifiers
to what is essentially a circuit simulator.

Basically the +3dB efficiency step you get with two drivers
operating together. Consideration of this phenomena led
to the Linkwitz / Riley alignments, which form no part of
classical filter theory alignments.

Simply put, 2nd and 4th order L/R alignments c/o at - 6dB
rather than the classical -3bB point. This compensates for
the parrallel efficiency increase mentioned above.
(There are no odd order L/R alignments)

sreten.
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