crossover frequency feedback request for 2-way components (Focal ISS 165) - Car Audio | DiyMobileAudio.com | Car Stereo Forum

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Old 08-14-2019   #1
 
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Default crossover frequency feedback request for 2-way components (Focal ISS 165)

QUESTIONS:
1) What crossover frequencies are folks using for car audio 2-way component systems in an active setup using 1-inch tweeters and 6-1/2 inch drivers? Are you high pass filtering the tweeter at about 2 kHz?

2) What slopes are you using for the different drivers? Would this be appropriate:
A) -18 dB/oct LPF for the subwoofer with a cutoff frequency of 80 Hz
B) -12 dB/oct BPF for the 6-1/2 inch drivers, 80 Hz to 2 kHz
C) -12 dB/oct for the tweeters at 2 kHz?


I bought a pair of Focal ISS 165 component speakers on sale. The crossover is integrated into the speaker wire, but I plan to use the drivers in an active crossover configuration. I removed the heat shrink from the speaker wire to obtain the RC values:

R = 4.7 Ohms

C = 3.3 micro-F


The corresponding cutoff frequency for these values should be fc = 10 kHz.


I have been out of audio for some time, but I am used to home audio 2-way speakers having a cross over frequency around 2 kHz, not 10 kHz.


I have reached out to Focal but they have not responded. I have also posted these questions on a vehicle specific site, but they are probably more appropriate for this audio specific site.

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Old 08-14-2019   #2
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Default Re: crossover frequency feedback request for 2-way components (Focal ISS 165)

You did something wrong. No 6.5 midbass is going to play nicely up to 10k nevermind a tweeter starting there. That tweeter will likely play fine down to 3000 at a good volume. A 6.5 starts beaming at like 2700hz. I would start at 4k playing at the volume you like lowering the crossover point by 100 until it sounds like crap. Start at 2000 with the 6.5 and go up. Hopefully they meet.

I almost always end up with LR 24 db crossovers. 18 for sub to mid bass sometimes. I mess with them but that almost always sounds best to me in 3 way setups.
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Old 08-14-2019   #3
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Default Re: crossover frequency feedback request for 2-way components (Focal ISS 165)

24db LR at 2500hz

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Old 08-14-2019   #4
 
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Default

I've had passives with a crossover that high on the tweeters and like 2000 on the midbass. I think it was a 6db slope. I think they did it that way cause the tweeters were really effecient and it ended up being acoustically crossed at 3200. It was a cheap effective way to make the 2 drivers work together.

I realized this when I first went active. I opened up and drew a schematic of the crossovers and tried to mimic them, I was really confused like you are.

I ended up finding on the manufacturer's site that they were crossed at 3200 so I went from there.

Try and find some specs on the drivers your using. Even if you can only find fs that's a start.
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Old 08-14-2019   #5
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Default Re: crossover frequency feedback request for 2-way components (Focal ISS 165)

The stock 3.5" 8 ohm dash speakers in the basic Ram truck system are crossed at something like 10-11k with a simple cap at 6db slope if memory serves. All has to do with how the speakers come together in the middle.

As for crossovers in a 2-way front it depends. A lot of small format car audio tweeters can't play much below 4k crossed steep without getting nasty. Others do fine at 2500hz and even 2000hz. For slopes use 24db Linkwitz Riley for all of them at least to start with. When testing at high volume as suggested above make sure the tweeter is louder than you would ever listen to it with really demanding music like heavy metal. I honestly wouldn't go much lower than 3500 24db slope. You'll probably end up with a gap in the crossovers like mid at 2800 and tweet at 3300 for example. Do you have measurement software? If so measure the response of the tweeter with the crossover first to see where it lands.

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Old 08-15-2019   #6
 
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Default Re: crossover frequency feedback request for 2-way components (Focal ISS 165)

Thanks for the responses.


I quadruple checked the resistor color code ......... and then just assumed that I became color blind in the previous hour of my life, so I found a volt meter and measured the resistor ....... 4.7 Ohms.


I quadruple checked my math too ...... but came up with the same answer all four times ......... fc=1/(2*pi*R*C) = 1/(2*pi*4.7*3.3E-06) = 10 kHz taking into account significant digits. The crossover only has one resistor, and one capacitor, so it should be a first order filter [-6 dB/oct].


I found a Focal data sheet for the 6-1/2 inch midrange, but nothing for the tweeter. It provides two frequency response curves ....... perhaps the second one is off-axis [but there is no legend]. No polar plots are provided. It is about -13 dB at 10 kHz.


I do not have the appropriate tools to do proper frequency response measurements of the drivers.


I will play around as suggested and we shall see what happens. I am probably a couple of weeks out from implementation - still waiting on a few items to be delivered.

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Old 08-15-2019   #7
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Default Re: crossover frequency feedback request for 2-way components (Focal ISS 165)

Quote:
Originally Posted by diymobileaudio997 View Post
Thanks for the responses.


I quadruple checked the resistor color code ......... and then just assumed that I became color blind in the previous hour of my life, so I found a volt meter and measured the resistor ....... 4.7 Ohms.


I quadruple checked my math too ...... but came up with the same answer all four times ......... fc=1/(2*pi*R*C) = 1/(2*pi*4.7*3.3E-06) = 10 kHz taking into account significant digits. The crossover only has one resistor, and one capacitor, so it should be a first order filter [-6 dB/oct].


I found a Focal data sheet for the 6-1/2 inch midrange, but nothing for the tweeter. It provides two frequency response curves ....... perhaps the second one is off-axis [but there is no legend]. No polar plots are provided. It is about -13 dB at 10 kHz.


I do not have the appropriate tools to do proper frequency response measurements of the drivers.


I will play around as suggested and we shall see what happens. I am probably a couple of weeks out from implementation - still waiting on a few items to be delivered.
You said the crossover has a resistor, and a capacitor? When you measured the resistance, was that just the tweeter, or was that the tweeter and the resistor? If that resistor is in series with the tweeter, you need to add that to the resistance of the tweeter. An 8ohm tweeter wired to that same capacitor will have a hpf of 6khz, which is a lot more reasonable than 10khz, which makes me think the resistor in the crossover is wired in series with the tweeter.

I guess I'm not clear as to whether or not you used the tweeter impedance and resistor to calculate the crossover frequency, or just one or the other.

Last edited by gijoe; 08-15-2019 at 01:15 PM..
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Old 08-22-2019   #8
 
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Default Re: crossover frequency feedback request for 2-way components (Focal ISS 165)

UPDATE:

I have taken a different path in the short term as their is recent talk of replacing the car.


The short term solution was to replace both door 6x9's, with some 6-1/2's that I already had. The driver's door 6x9 was blown, so I replaced both sides. The Helix setup remained the same as far as driver distances, cutoff frequencies, slopes, etc. I took some audio measurements with the included Helix software, but I need to do that again as I got rushed.


I also replaced the head unit to add Apple Car Play.


If the vehicle is replaced, the plan would be to install the Focal's in the new ride and I can use the feedback provided here. Thanks again for everyone's input.

---
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