Bass Blockers

as most know i recently fitted new rockford speakers in my glanza, however with the fronts been so small they cant take any bass what so ever. whats the best way if running all speakers off the head unit to stop the bass getting to the fronts, inline bass blockers or something more substantual like a din sized graphic equalizer

Jim

Are they stock fronts? if so you wont gain from anything more than bass blockers. You can make your own actually for just a few of your pounds..

Bass Blockers are capacitors. You need to source a non-polarized cap at the right value (measured in micro farads) for what you need to filter.

At 4-Ohms (most standard car audio is 4 Ohm), a 200 micro farad cap will produce a 6dB/octave high pass filter at 200-Hz. Every time you half the value, you double the frequency:

200 mF = 200 Hz
100 mF = 400 Hz
50 mF = 800 Hz
25 mF = 1600 Hz
12 mF = 3300 Hz
6 mF = 6500

These are approximate. So for tweeters (4-Ohm) you need something between 4 and 10 mF (4.7 is common). Mid-ranges use something around 40-100 mF. The larger the voltage rating on the cap, the more power it can handle.

Maplin is your best bet buddy, they have a massive selection.

Dave.

no mate they aint stock fronts they are rockford P142 speakers

2way coaxial, im guessing ill just to stop and frequency below about 500Hz getting through

Jim

just run a quick simulation and a bode plot, this is the sort of frequency responce i want from the fronts



Jim

PureEvilDevelopments wrote:

just run a quick simulation and a bode plot, this is the sort of frequency responce i want from the fronts

Jim

Have to ask Jim, why go to these lengths to plot the filter you want for the fronts if you're just running coaxials and 6x9's off a head unit? Would have thought a first order passive filter like a bass blocker would fine for this application.

Dave.

it is just a bass blocker i want lol but when i looked at a high pass filter on my program thats the circuit it gave me lol

Jim

You could build a second order filter if you wanted sharper attenuation, just need to add a resister and arrange them correctly. You could build one on bread board easily enough and shrink wrap it, the easiest to build looks like the diagram below, but there are lots of different configurations all with pro's and con's..


ed ^image not showing on black backroud, it is there, right click and you can grab it.

..it's overkill though. I'm running a 12" sub at 35hz up to 75hz and then two 8" midbase subs running from 75hz up to around 150hz (comps take over from here as this is just above the frequency where stereo imaging starts to be distinguishable from omni-directional lower frequencies and i want the stage in the front). In this situation the filters are essential to ensure the speakers don't both try to produce the same frequency above -3dB as due to different speaker sizes, positions and attitudes it would almost certainly lead to sound cancellation. For this application i am running second order butterworth filters and with a little tweaking it should run ok.

On a system running full range at the back already, any missing (filtered) frequencies at the front would likely be hidden by reflections from the rear speakers - especially if there is little in the way of front stage. If you run a set of speakers up to a certain frequency, then a different set past that frequency - that is when sharp filter curves are important.. but this then runs into the world of expensive signal processors.

fountain of knowledge you are Dave

Jim

Huhhhhhhh......what the......!!!! (Mr.G shakes head and shuffles off into the land of the blissfully unaware)......
Clever stuff guys........but rocket science and witchcraft to me.........
Dave you should head the ICE section on here.......powerfull with the force you are......

Im with you Andy on this. I would say im pretty good at understanding even the most complicated things, even algebra, but this stuff is so technical i can't get my claws into to even start understanding. props to you fellas.

Too right Tom..........we come from the era of Decca Dancette's and Radiograms...............