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Multi-Way Conventional loudspeakers with crossovers

Help me out to find values for my cross-over and attenuation circuit.
Help me out to find values for my cross-over and attenuation circuit.
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Old 11th February 2013, 05:20 PM   #1
krafty is offline krafty  Brazil
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Default Help me out to find values for my cross-over and attenuation circuit.

I will be building a new small loudspeaker system with two drivers:

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Car speaker (Mid range):
Size: 4"
Imp: 4 Ohms
Power (RMS): 50 W
SPL: 86 (dB/2.83 V/m)
Freq. Resp. 100 up to 8.000 Hz


Click the image to open in full size.
Tweeter:
Size: 2.5"
Imp: 4 Ohms
Sensitivity (2,83V a 1M): 108dB max. (0dB = 20ÁPa);
Max. Voltage (Pink Noise): 13V rms;
Power (RMS): 40 to 100W
Freq. Resp. 5KHz to 20 KHz;
Sound Dispersion: 90░.

Currently I don┤t have the time to search or dig out the values to find out if I need a sealed or ported enclosure. So I decided to go with the sealed enclosure. This after seeing this video: Ported vs. Sealed - Detailed Comparison - YouTube
Apart from that, I don't have more specs than the ones I listed above, from the drivers; to research and construct the parameters table for these drivers. If anyone is have got those and would be willing to test them using some kind of software, I would appreciate.

Box enclosure is:
Height 224mm
Width 160mm
Depth 160mm
MDF 9mm

Question 1:
I am told that the tweeter overlaps into the mid-range from 5kHz to 8kHz.
Being that the two of the drivers are 4 Ohms, which would be the ideal frequency split for the crossover, considering the split to respect the octaves?

Question 2:
I am also told that the tweeter is 22dB louder than this mid-range and that I need to construct a driver attenuation for the tweeter. Considering that the tweeter will handle no more than full 30W RMS from the amplifier, what value for maximum power should I apply in the calculation of this attenuation circuit?

Question 3:
Will I need this enclosure to be definitely ported because of the heat dissipation from the attenuator?

NB: This is really a small project for a computer speaker. I don't plan to have all the meticulous details done nor expect it to be perfect professional. Just want some basic help to not make any gross mistake.
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Old 11th February 2013, 08:30 PM   #2
tvrgeek is offline tvrgeek  United States
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If you don't have the time to do your homework, we don't have the time to help much.

Just throw them in a box, put an L-Pad on the tweeter and a first order (single cap about 16uF) on the tweeter and be done with it. Sound will come out of them so they will be a success. Google L-Pad, and Google first order crossover calculator. You can't design a ported box without the T/S parameters anyway. So you will be lucky to get 200 Hz out of them. Your mistake when you picked a car midrange.

Skip the You-Tube and do your homework. You will get further faster and a lot more help here.
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Old 11th February 2013, 09:12 PM   #3
krafty is offline krafty  Brazil
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I didn't buy these car speakers. They've been given to me, and I don't feel like trashing them. The setup is to replace cheapo multimedia computer speakers, so I believe it will be better sounding than those.

You also didn't answer which frequency I should go for the crossover split, which would be fairly easy to tell with someone familiar with this. Let alone the resistor issue that is also an easy thing to nail down.

I asked specific questions. I didn't ask how I setup the perfect box.

Last edited by krafty; 11th February 2013 at 09:18 PM.
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Old 11th February 2013, 09:56 PM   #4
tvrgeek is offline tvrgeek  United States
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16uF is about 2500 Hz. Ideal? Heck no, but to find the "idea" takes considerable measurement and testing. What I gave you was safe. Yes, the L-pad is easy. You can look it up as easy as I can. Quicker than asking about it here.

Your specific questions are not well enough based for specific answers. For what you want, I provided all the guidance you need.
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Old 11th February 2013, 11:04 PM   #5
krafty is offline krafty  Brazil
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I did calculations and 6000Hz/12dB is the appropriate cut.

I have the parameters for the mid range now:

Name: 4HTS400

Fs = 115,1 Hz
Qms = 3,652
Vas = 0,99 liters
Cms = 0,221 mm/N
Mms = 8,66 g
Rms = 1,715 kg/s
Xmax = 2, mm
Xmech = 3, mm
P-Dia = 85, mm
Sd = 56,19 sq.cm
P-Vd = 0,0112 liters
Qes = 0,745
Re = 3,51 ohms
Z = 4,461 ohms
BL = 5,43 Tm
Pe = 50, watts
Qts = 0,618
no = 0,195 %
1-W SPL = 84,9 dB
2.83-V SPL = 88,68 dB

Is this enough to find out about box size, enclosure type?
Do I need the same parameters for the tweeter?
I am using an application called WinISD to enter these parameters, but a couple of them are still missing...

It is said that the EBP is found by doing fs/Qes which is 155 in my case - ported enclosure.... Would that be right?
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Old 11th February 2013, 11:30 PM   #6
picowallspeaker is offline picowallspeaker  Italy
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I've always read that you can trade extension for efficiency, but this is not the case! by looking at the first data, the resonant frequency, it tells you ( also the application suggests...100 up to 8 KHz ) that there isn't much to trade below 100 Hz So the application won't be much multi-media but just
some-media...it means that the lower tones & harmonics would be just truncated . So 16uF ....I guess even lower values to not 'meet& shake hands'
to tweeter's resonant frequency and a massive attenuation with L-pad.
First experiments can be done with just the baffle and without the box
Your mind will fill the...empty spaces
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Old 11th February 2013, 11:38 PM   #7
PeteMcK is offline PeteMcK
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Location: Western Sydney
the tweeter looks like a piezo....
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 11th February 2013, 11:42 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

Stick them in a sealed stuffed box of about 2 to 3 litres.
(4 litres tuned to 40Hz is an option for EQing.)

I'd lose the attitude you know anything about x/o design,
you don't, and your not asking any of the right questions.

Fortunately you can EQ in a PC to your hearts content.
No chance is that tweeter 108dB/2.83V/1m, but it
will likely need L-padding back down to the midbass.

L-pad and first order series crossover at a guess 4KHz
will give you something you can EQ with the computer.

rgds, sreten.
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Old 12th February 2013, 01:45 AM   #9
krafty is offline krafty  Brazil
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Quote:
the tweeter looks like a piezo....
Yes, it is a piezo.

Quote:
Stick them in a sealed stuffed box of about 2 to 3 litres.
(4 litres tuned to 40Hz is an option for EQing.)
The box is about that size. 224mm (h) x 160mm (w) x 160mm (d).
Now that I know that the EBP is 154 (fs/Qes), shouldn't the ported enclosure be your recommendation in here or am I missing something?

Quote:
I'd lose the attitude you know anything about x/o design,
you don't, and your not asking any of the right questions.
I apologize. I will try to ask the right questions.

Quote:
Fortunately you can EQ in a PC to your hearts content.
No chance is that tweeter 108dB/2.83V/1m, but it
will likely need L-padding back down to the midbass.
Yes, I have EQs available. Why do you say that no chance that tweeter is that value, have you got any guess on what real value is? Only measurable with software?

Quote:
L-pad and first order series crossover at a guess 4KHz
will give you something you can EQ with the computer.
This 4kHz you mean for the crossover split?

Thanks for the answer.

Last edited by krafty; 12th February 2013 at 01:56 AM.
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Old 12th February 2013, 02:55 AM   #10
PeteMcK is offline PeteMcK
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better have a look here, pizeos are dealt with differently:
Frugal-phile | Piezo Tweeter Crossovers | J Risch
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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