acur8ly

iTrader: (1)

I installed some kenwood x speakers in the doors, I was told to put bass blockers on them. Standing out of the car listening to it it sounds incredible. Get in the car and all the hights overpower you in front. Anyone else have them? I am thinking of removing them

Nihilistan

If you lose the base blockers, your small front speakers are going to distort at high volume... even worse, you can hang a voice-coil and watch it fry (not likely unless you're driving it extremely hard).

You have a few options:
-Take em off and keep volume down (that's no fun)
-Adjust the treble on the head-unit
-If the tweeters are adjustable, point them at something other than your head... highs are extremely directional.
-If there's not already, put diffuser over the tweeter (perforated metal works well)
-You can install a power resistor (maybe ~.25 ohm 1W) in series with the tweeters (assuming they are 2 or 3-ways)... this will just attenuate the highs
-You can replace the bass-blockers with a band-pass filter and roll-off some of those highs. Then again, you could just mod the bass-blockers to do the same thing... pretty straightforward, 2 parts max. Write me if you're interested. If the other options don't work, this will.

-- Nihil

acur8ly

iTrader: (1)

Thanks for your answer. I am interested in the mod of the bass blockers. Is it something thats hard to do?

Nihilistan

Nah, it's not difficult from an electrical point of view. Assuming you have a soldering iron it should be easy. Only thing I don't know about are size constraints you have on the installation... is there a little room around the base blocker the extra parts could fit in?

-- Nihil

acur8ly

iTrader: (1)

yes there is room but how big of a part are u talking about?
I do have a soldering iron

Nihilistan

First off, I'm writing this for someone I assume knows nothing more than how to solder and take apart the car. Sorry if it's too basic for ya.

Here are some instructions for the mod... it's quite easy and doesn't require any destruction of the bassblocker you already have. I can't post pictures here so I'll try to get by using words. PM me w/ your email for schematics and some plots.

What you'll need (should be able to get everything from local radio shack or electronics store):
-Your bass blocker (doesn't matter what frequency)
-Your speakers (assumes 4 ohm here)
-a 10 uH inductor (that's micro-Henries) - these are also called chokes -also equal to .01 milli-Henries (.01 mH) - Ask the clerk about power rating but anything wound with 26 gauge or less wire is way more than ample.
-some wirewound power resistors (from 1 to 10 ohms) Please read below for POWER RATINGS
-solder
-soldering iron
-electrical tape

You can make the inductor yourself if they don't have the proper value. Just buy some electric motor wire (has enamel on it) and follow the directions on these pages:

http://retro.co.za/audio/xover.html
http://www.colomar.com/Shavano/inductor_info.html

Basically, this adds an attenuation circuit which will slowly dampen any frequencies above 1kHz. Depending on how harsh your tweets are, you may need more or less attenuation, so I suggest getting a handful of power resistors (they're damn cheap anyway).

First you need to figure out how much attenuation you want. Here's a quick table to give you an idea of what kind of high-frequency response you'll get with different resistor values (note this is for 4 ohm speakers):

Resistor Frequency Response (in dB)
Value 1k 2k 4k 8k 10k 15k 20k
.25 0 -.10 -.25 -.42 -.46 -.49 -.50
.5 0 -.06 -.22 -.54 -.65 -.81 -.89
1 0 -.03 -.14 -.45 -.64 -1.00 -1.28
2 0 -.02 -.08 -.31 -.46 -.87 -1.31
4 0 -.01 -.05 -.20 -.30 -.62 -1.04
8 0 -.01 -.03 -.13 -.21 -.44 -.76

A quick dB to percentage approximation table:
-.125 dB = 98% (of max volume)
-.25 dB = 97%
-.5 dB = 94%
-.75 dB = 91%
-1 dB = 89%
-3 dB = 70%
-6 dB = 50%

As you can see, the higher the resistance, the flatter the response through the midrange and the sharper the rolloff at high frequencies. Decreasing the resistance will make the filter act more and more linear. I'd recommend starting with a 8 Ohm resistor and working your way down until you are happy with the sound.

After you've chosen your resistor value, calculate the minimum required power rating. For this calculation:
P = amplifier Power (in Watts into 4 ohm load)
R = the resistor value you chose (in ohms)

power rating = (P^2) / (R^2 + 8R + 16)

Make sure you do not go under this value!!! Otherwise, the resistor could burn up and then you're screwed (cause it's in your freaking car). As a measure of safety, you should have at least double this figure. For example, if you have a 25 watt amp and chose a 8 ohm resistor:

power rating = 25^2/(8^2 + 8*8 + 16) = 4.35 Watts. You must go with at LEAST a 5 Watter, but would try to get a 10W. So for this example, I'd be looking for a 8 ohm 10 W resistor. Also, make sure the resistor is WIREWOUND. Non-wirewound resistors often require heatsinking to make them handle any power at all. You obviously can't do that here!

Quick note, if you can't find the value you need with high enough power rating, buy two resistors that are double the resistance you need and wire them side-by-side. This will be about the same as having the resistance you needed but twice the power rating of the individual resistors.

In the example, I could substitute two 16 ohm 5 Watt resistors for each single 8 ohm 10 watt one.

To make this handy chingas, simply place the resistor(s) and the inductor side by side and solder the leads together (so they're wired in parallel).

Installation is very straightforward. You actually don't have to touch the bass-blockers. Simply clip one of the speaker wires and solder this chingas inbetween (as if you were going to install another bass-blocker).

So now you have something like:
To amp <---wire---> Your Chingas here <---wire---> Bass blocker <--- To Speaker

Throw a little electrical tape over the connections and test it. If you still think the highs are too harsh, then adjust the resistor value. You can obviously use values for the resistors other than what's listed in the table, and the response will be somewhere between close values.

Once you're happy, double check to make sure you have solid solder joints then wrap everything in electrical tape and put everything back together.

Hope this helps!

-- Nihil

DISCLAIMER: If you don't know what the F you're doing, ask someone that has electrical experience. They will be able to do this in their sleep.

98_2.5_TL

If you don't have room in your doors for a simple bass blocker, then I'm black.


(and I'm not)


they're really easy to do.

CJITTY

I got bass blockers on my car...made the speakers sound much better!