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Old 8th September 2011, 06:58 AM   #1
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Question Low pass filter?

Hey guys,

I'm a novice when it comes to this stuff. I'm trying to determine exactly what is the best route to go about this. I want to add a little more bass fill in the rear deck and have decided to go with some Kicker CVT65 2ohm subs to replace my 6x9 coaxials. My car has a Bose system with amps in both front doors and an amp power the rear deck coaxial speakers.

Now since this amp is designed to power speakers, wouldn't it be full range?
How would i go about reducing high frequencies so that it's mainly lower range for sub function? I see alot of high pass filters sold via crutchfield/sonicelectronix but i can't seem to find something for my situation.


-David
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Old 8th September 2011, 07:40 AM   #2
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Hi David
The easiest way is to run an inductor made for speakers - usually available at electronic shops from the amp to the speaker ie a series connection. You will find it will then allow bass frequencies to work better
suggest you study some two way crossover designs such as old AR schematics ancient but they work well. To roll frequencies off, isn't quite the point although it can be done with a parallel cap but then creates problems for amplifiers that see a parallel cap as a capacitive load, think instead of making the driver you have, function as it is intended. See: AR-4x Schematic | The Classic Speaker Pages

Cheers / Chris
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Old 8th September 2011, 08:55 AM   #3
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Quote:
Originally Posted by Chris Daly View Post
Hi David
The easiest way is to run an inductor made for speakers - usually available at electronic shops from the amp to the speaker ie a series connection. You will find it will then allow bass frequencies to work better
suggest you study some two way crossover designs such as old AR schematics ancient but they work well. To roll frequencies off, isn't quite the point although it can be done with a parallel cap but then creates problems for amplifiers that see a parallel cap as a capacitive load, think instead of making the driver you have, function as it is intended. See: AR-4x Schematic | The Classic Speaker Pages

Cheers / Chris
So something like this would work?
Audiobahn ASX02J 2-Way Passive Crossovers - Sonic Electronix

I've spent the last two hours looking around for lowpass crossovers and I can't find one for 2 ohm.
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Old 8th September 2011, 12:44 PM   #4
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Yes, now under the plastic cover of the Audiobahn you will find more than likely an inductor, maybe what is called a Zobel network if audiobahn have done their homework as it helps the amp drive the speaker and a series cap and maybe another inductor.

In the late 1960's the BBC bless their tweeters created a flurry of activity to satisfy their remote recording vans with a speaker called the LS 3/5a. Suddenly 10 or more manufacturers were concentrating on this tiny speaker and in the process designing extremely good crossover networks to perfectly match the speaker. The BBC also very much liked Quad's ESL57 but it was a bit big for their vans. So getting to the point of your 6.5 inch driver matching it to the right crossover is a matter of understanding a little about what a crossover actually does. As you can see from the AR schematic a simple inductor leading into the bass driver is doing most of the work- now view the speaker as a membrane moving backwards and forwards - to those low bass notes, it is creating quite a load for the amp - but the inductor in the crossover greatly assists the amp and the speaker to do their task.
so yes the little audiobahn crossover will probably do the trick, and get you a much better sound. You could also investigate crossover networks from slightly bigger speakers where the components can allow for higher wattage. 2 ohms is a fairly difficult load for the majority of amps - however what is being calculated by the manufacturer is efficiency and a broad understanding that a 6.5 inch speaker can only do so much. a 1.5 ohm series 10 watt resistor although reducing power slightly can save expensive amp repairs Hope this helps / chris
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Old 8th September 2011, 02:38 PM   #5
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Many subwoofers have no ability to produce high frequencies so a crossover may not be necessary. Have you connected them directly to see if there was too much high frequency output?
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Old 8th September 2011, 03:02 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

No it won't work well, thats a mid treble c/o. What you need is a typical
car subwoofer passive c/o :
AVSL Group : Product : 900.582UK
http://www.dfbtrade.co.uk/products/U...d-900.582.html
if you only want to beef up the low bass end. You can tune
the low pass somewhat by removing / using the capacitor.

Of course you can low pass the signal to the rear amplifier quite easily,
and far cheaper, with a series resistor and parallel capacitor on the
two inputs, say 10Kohms and adjust the caps value to taste, ~ 100nF.

rgds, sreten.
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Last edited by sreten; 8th September 2011 at 03:07 PM.
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Old 8th September 2011, 09:41 PM   #7
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honestly unless there is something wrong with your bose equipment i would leave it all intact. bose is a nice product and in my opinion replacing bose speakers with kicker is a definate downgrade.

a while back a guy in a new dodge truck with an oem infinity audio system came in the shop and wanted me to pull all the infinity equipment and replace it with kenwood/pioneer stuff. 2 days later he was back wanting his oem infinity system.

take a look at kicker prices and compare it to bose prices see a difference.

if you want more low end add a bass tube or something simple and keep all the bose.
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Old 8th September 2011, 11:17 PM   #8
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I will continue looking and studying inductors and i will probably end up testing it to see what is the best way. Thank you all for your help, I appreciated it.

Quote:
Originally Posted by Perry Babin View Post
Many subwoofers have no ability to produce high frequencies so a crossover may not be necessary. Have you connected them directly to see if there was too much high frequency output?
I have not as I am at the mere stage of deciding what to do. I just assumed that if the amp is designed to power full range speakers and connecting it to a sub would make the sub try to play full range. I will try it out when i do decide to pull the trigger.

Quote:
Originally Posted by bdgf2004 View Post
honestly unless there is something wrong with your bose equipment i would leave it all intact. bose is a nice product and in my opinion replacing bose speakers with kicker is a definate downgrade.

a while back a guy in a new dodge truck with an oem infinity audio system came in the shop and wanted me to pull all the infinity equipment and replace it with kenwood/pioneer stuff. 2 days later he was back wanting his oem infinity system.

take a look at kicker prices and compare it to bose prices see a difference.

if you want more low end add a bass tube or something simple and keep all the bose.
From what I have seen, most Bose systems I have seen are pretty nice. For some reason when they designed the system for the RX8 they left alot to be desired. The bass is muddy from the 8.5" driver in the door, rear speakers are lacking and the tweeters were designed to fill more mids than highs which is weird.

Last edited by wind dance; 8th September 2011 at 11:22 PM.
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Old 13th September 2011, 02:38 PM   #9
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Quote:
Originally Posted by bdgf2004 View Post
honestly unless there is something wrong with your bose equipment i would leave it all intact. bose is a nice product and in my opinion replacing bose speakers with kicker is a definate downgrade.

a while back a guy in a new dodge truck with an oem infinity audio system came in the shop and wanted me to pull all the infinity equipment and replace it with kenwood/pioneer stuff. 2 days later he was back wanting his oem infinity system.

take a look at kicker prices and compare it to bose prices see a difference.

if you want more low end add a bass tube or something simple and keep all the bose.
b(l)ose ain't anything special at home and certainly not in car-they're a marketing exercise for the car manufacturer (look at the new Fender VWs-that's right an instrument manufacturer now make Hi-Fi systems for cars FFS!!!)

Just because Bose cost more it doesn't mean it's any better-again look at Bose's marketing-you think it's cheap to get all those full page adds in lifestyle mags?

Honestly, and really not trying to cause offense, if you think:
"bose is a nice product and in my opinion replacing bose speakers with kicker is a definate downgrade"
and you installed Kenwood/Pioneer upgrade over factory infinity system and had a guy wanting his money back you are in the wrong business

OP, to calculate coil values use this link:
Passive Crossovers, Capacitor and Coil Calculator

It would be handy to know some other specs on your drivers (Fs and QTS) and what frequency you want them crossed at. I'd also check the original speaker's impedence-if 4ohm then the amp won't like a 2ohm load so you'd be back to the drawing board anyway. (not a bad thing as if you're going IB in the rear deck of the car-the bigger the driver the better-even if the hole is still 6x9 shaped a 12" will fire through it and offer better IB output)
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