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Old 22nd August 2015, 12:11 AM   #1
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Default My first crossover

Hi,

I've read, and read, and... well, yes read a lot about DIY crossovers.
Finally I reached my solution.

I just need some advice and/or recommendations to change anything that I'm not doing right.
Here you have all the data and the diagram (in attach) I'm using to build my crossover:

TWEETER - MONACOR DT99:
Impedance (Z) 8Ω
Resonant frequency (fs) 1,500Hz
Max. frequency range fx-18,000Hz
Rec. crossover freq. (12dB) 2,500Hz
Music power 80WMAX
Power rating 40WRMS
SPL (1W/1m) 93dB

WOOFER: DAYTON
DC160-8 6-1/2" Classic Woofer 8 Ohm
Nominal Diameter 6.50"
Power Handling (RMS) 50 watts
Power Handling (max) 100 watts
Impedance 8 ohms
Sensitivity 88 dB @ 1W/1m
Frequency Response 30 - 4,000 Hz
Voice Coil Diameter 35 mm
DC Resistance (Re) 6.7 ohms
Voice Coil Inductance (Le) 2.34 mH
Resonant Frequency (Fs) 34.3 Hz
Mechanical Q (Qms) 3.47
Electromagnetic Q (Qes) 0.36
Total Q (Qts) 0.33

Many thanks in advance for any advice.

Ben
Attached Images
File Type: png 2500_MONACOR_V2.png (34.7 KB, 238 views)
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Old 22nd August 2015, 04:06 PM   #2
tusker is offline tusker  Kenya
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Quote:
Originally Posted by Ben Martin View Post
I just need some advice and/or recommendations to change anything that I'm not doing right.
Here you have all the data and the diagram (in attach) I'm using to build my crossover:
There are some questions: On what ground did you choose those drivers? What enclosure do you intend to build? How did you come up with the values of the attenuator circuit? Have you made any simulations? Do you have measuring equipment? Without the latter, you will hardly be able to design a proper crossover.
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Old 22nd August 2015, 04:56 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

Its a general disaster area. That calculator is totally real world wrong.

With that bass unit build this :https://sites.google.com/site/undefinition/classix-ii

rgds, sreten.

At the price you can't go wrong with : http://gr-research.com/x-lsclassickit.aspx
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Last edited by sreten; 22nd August 2015 at 05:24 PM.
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Old 22nd August 2015, 05:20 PM   #4
tusker is offline tusker  Kenya
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Hi,

I made a quick and dirty simulation in 10 l (0.35 cuft) vented enclosure tuned to 42 Hz it does not look too good, to say the least.

First simulation is without crossover, second with your crossover. At first glance I would say, those drivers do not fit together very well and the crossover erm needs some improvements.

If this is your very first DIY project, I'd suggest you build a proven design before you start designing your own speakers.
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File Type: png without_XO.png (15.2 KB, 209 views)
File Type: png with_XO.png (15.0 KB, 209 views)
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Old 22nd August 2015, 10:16 PM   #5
jReave is offline jReave  Canada
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And that looks to be the case without baffle step loss included!!
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Old 22nd August 2015, 10:29 PM   #6
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Why don't you just increase the tweeter attenuation to 5dB since the treble is 93dB and the bass is 88dB? C and R on the woofer circuit [the zobel network] do nothing useful and could be left off. With more thought I would leave them in as the bass seems a high inductance and the impedance will be rising at 2500Hz

Last edited by bigbottom; 22nd August 2015 at 10:47 PM. Reason: Thinking more
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Old 22nd August 2015, 10:55 PM   #7
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If you want to leave C and R off, then put the value of the woofer impedance at 2500Hz from a datasheet, into the calculator and use those values for the woofer filter. The tweeter stays at the existing 8ohms components
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Old 22nd August 2015, 11:59 PM   #8
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Hi,

At risk of being left field, the best crossover is not to have one.

The DC160-8 should be run without a crossover and then you just match the DT-99 to intersect its frequency response.

If we work on 4 kHz at 80 dB and roll the DT-99 off to match 4kHz at 80 dB the combined output is then +3 dB at 4kHz.

If we now scale the DT-99 frequency response up using a first order crossover, for 80 dB at 4 kHz the DT-99 has to be -14dB.

Using 6 dB per octave the -9 dB point is 8 kHz and the -3dB point is 16 kHz, requiring a 1.1 uF capacitor, since the impedance looks to be 9 ohms. Easiest to use a 1uF capacitor as a nearest fit.

You now have a response that is 83 dB/W +/- 3dB from 45 Hz to 8 kHz and then a slightly rising treble to 92 dB/W at 16 kHz, which you can loose by listening slightly off axis.

Use a film 1uF capacitor and by pass it with a 0.01 uF Polypropylene Cap.

Almost no crossover.

Use a sealed box and play with the stuffing for best vocals, use radio or speech rather than singing, as your hearing is tuned to spoken voices.

Don't forget to use twisted cable inside the cabinet of at least 42/0.2mm.

Should be blinding, have fun.
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Old 23rd August 2015, 12:45 AM   #9
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Woa... impressive.

Many thanks to all of you for the fantastic input.
Ok, I'm going to start by answering some questions.

I did base my cabinets on the "Classix II" by Paul Carmody.
I made them taller (like you can see in the attached images) but the cabinet inside volume/liters were absolutely respected and I used the vent port suggested by the author (It is tuned to 40 Hz, which means you'll need a 1.5" dia vent, approximately 4" long.)

Why did I choose these drivers?
Because I had them from a previous buy (to replace old 6 1/2" speakers) and the DT99 where offered.

I also bought two "DC28F-8" Silk Dome Tweeter 8 Ohm

PRODUCT SPECIFICATIONS
Speaker Type Tweeter
Nominal Diameter 1.125"
Power Handling (RMS) 50 watts
Power Handling (max) 100 watts
Impedance 8 ohms
Sensitivity 89 dB @ 1W/1m
Frequency Response 1,300 - 20,000 Hz
Voice Coil Diameter 29 mm
DC Resistance (Re) 5.5 ohms
Voice Coil Inductance (Le) 0.09 mH
Resonant Frequency (Fs) 637.2 Hz
Mechanical Q (Qms) 0.82
Electromagnetic Q (Qes) 0.90
Total Q (Qts) 0.43
Surface Area Of Cone (Sd) 6.6 cm

So, that's why I ended up with four "DC160-8" and two "DT99" and more two "DC28F-8" twitters.
Lots of drivers to let them get dust in the shelf.

This lead me to assemble two different pairs of speakers. (see cabinet photos)
For one pair, I used two "DC160" and two "DC28F-8" twitters.
To this one, I assembled a specific crossovers based on the schematics by
Dennis Murphy "http://murphyblaster.com/content.php?f=main.html".
(See attached crossover schematics and photos)

Unfortunately, I must have done something wrong because the tweeters were almost inaudible with these crossovers.
I then decided to removed the L-Pad (R1+R2) and I could hear all the high frequencies back, but something stills sounding very wrong.
I even switch the tweeter polarity to check the inverted phase issue but to no avail. Well, it seems I really need to review it all. (start from fresh).

So, I decided to try new crossovers for the other speakers pair.
The one that uses the "DC160" and the "DT99" drivers.
That's why I used the free calculators available on-line but judging by your opinions, it seems I'm not going very far this way, either.

I don't have any software to test the drivers because I wouldn't know how to.
I downloaded this spread-sheet "http://audio.claub.net/software/jbabgy/PCD.html", but I must confess, I feel like a donkey looking to a palace. I wouldn't know where to start.

With all your input (that I truly appreciate) I feel even more lost, to the point where I'm considering to setup the most simple solution. Instead of a 2nd order -12dB per octave crossover, I guess I need to start by testing the most basic 1st order Butterworth. unless some of you (good souls) decided to help to design something that works for these drivers configuration.
Attached Images
File Type: png Crossover diagram by Ben.png (11.0 KB, 176 views)
File Type: png Crossover.png (794.5 KB, 176 views)
File Type: jpg DSC_0076.jpg (72.5 KB, 49 views)
File Type: jpg DSCF_0046.jpg (150.4 KB, 43 views)
Attached Files
File Type: pdf My speakers based on Classix II.pdf (134.7 KB, 7 views)
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Old 23rd August 2015, 08:48 AM   #10
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I think arturo has a reasonable idea about just high pass filtering the tweeter, but if the tweeter is 93dB versus about 85dB I think you could still use an attenuator [R1 and R2 in the calculator] You are right that you usually reverse the wiring to either bass or treble with a 2nd order, but you need to try it both ways, because the drivers are not flat at xover. That xover calculator is just a standard textbook filter and looks fine to me, perhaps with the switched tweeter polarity to avoid a notch.

If you do try that calculator, I was wrong with what I said - you have to keep C and R because the woofer is an ugly high inductance. Thats the trouble with guesstimating..
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