Printer Friendly Forum Posts - crossovers or caps for stock stereo

Hello, Im starting a build in the wifes car. Her stock speakers are blown because the kids listen to rap/hip-hop loud and they want a lot of boom, so they put the bass all the way up. Im installing some infinity 5x7's now, and amp&subs later. What type / frequency of caps can i use to keep the kids from blowing the new speakers till i can afford a good amp & subs? Any advice is greatly appreciated, thank you.

I thought series resistors to limit output power?? (Rather than roll off?)

I learned recently that increasing output impedance did not cause amps to overheat... (LOL!!! A great lesson - taught by a pro!)

But I am assuming excessive power/drive is the problem.
And that a fire isn't.

Ooops again?

Sorry cvame - ignore my reply.

A resistor will cut the power. The problem with a resistor is the heat that it will have to dissapate in order to limit the power to the speaker. It will get hot, really hot. As you stated, it could get fire hot

Here's what you do: install the new speakers and tell the kids that if they blow the new ones out before you can add more gear, that you will see that the perp never gets the key to your cars again. Ever. So take it easy with that volume knob, kids.

Kids... !

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

I am an old school installer. I say, do it right the first time. But since you are not going to then you should purchase 100uf capacitors. Capacitors limit the frequency. Otherwise called BassBlockers.

Most capacitors are directional. Just install them inline at the positive of each speaker lead as close to the speaker as possible.

NEVER use resistors. This will change the impedance and cause your finals in your radio to get damaged

Interesting....

topinstaller200 wrote:

NEVER use resistors. This will change the impedance and cause your finals in your radio to get damaged

That's what I thought until corrected a while ago.
AFAIK, I was wrong - increased speaker impedance will NOT cause output damage (ie, overheating). I then realised I was thinking of old school amps, transmitters etc.
What type of amplifiers are damaged?

topinstaller200 wrote:

Most capacitors are directional. Just install them inline at the positive of each speaker lead as close to the speaker as possible

An audio (speaker) inline capacitor should be non-directional (DC biasing excluded).
If using electrolytics (eh, 100uF), then bipolars should be used.

Or am I misunderstanding and showing my age yet again? (Especially since I like Steve's answer best!!?)

Wow, thanks for all the advice guys. I really appreciate it.

@ stevdart - you hit the nail on the head, lol.

The wifes car is a 2002 ford windstar with stock stereo, and now has infinity 5x7 2ways. I went to the local stereo shop and they told me to put these little 'bass blockers" on the positive wire to each. they have these numbers on them - " A66, 66MFD, 100WV" and "NP 85C B12". Are these the right things to use?

I put them on two speakers and it took all the bass out, just mids & highs. Are they safe? I do not plan on ever putting an amp to these speakers, just to the sub later.

Kids! ROFL!

Make sure the stereo can handle the impedance of the new speakers (if I recall, Infinity makes both 2 and 4ohm models).

Keep the bass down.

Keep the volume down.

No sort- of crossover is needed so long as the 3 previous pieces of advice are followed. The only kind- of 'bass blocker' that is needed is common sense. There is no way that factory stereo can overpower them. Ever.

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DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001

use non-polarized capacitor 100uF.

@ jmelton - I wish i could make sure they keep the bass down, but im hardly in the car and when they're with momma, they adjust the bass then (hard headed) Anyways, the stock stereo wont mess up these infinity's? They are 60rms, and im sure that factory deck isnt putting out much more then 20rms if that, right?

@ nismo- so are the caps i got not good?

Thanks a million guys, i really appreciate it.

Nismo used the correct term (non-polarised - I said "bipolarised" ... get what sort of people I deal with...)

Speaker signals are AC hence there is no + or - polarity as in "DC".
Standard electrolytic caps are polar - they have a + and a - end.
Non-polarised are designed for AC signals (& preempting technoheads... "with insufficient DC offset").

Your polarised caps are not suitable for speaker signals.

@ old spark - wow thank you very much for your reply. Unfortunately, what you said is way over my head when it comes to this stuff....my bad. So the "bass blockers" i bought at the stereo shop are not good? Where can i get the ones you recommend or what do you advise i specifically ask for at the stereo shop? (Im beginning think maybe glueing the bass adjustment knob in place on the stereo might be an easier fix ..lol.)

Thank you

Im sorry "old spark', i just noticed nismos previous post. So start looking for a "non-polarized capacitor 100uf"?

I'm just saying it <whatever> capacitor(s) was/were advised, they need to be non-polar. (And Nismo agrees.)

The advice to connect capacitor + to speaker + is misleading, irrelevant, wrong...
Hence "non-polar" caps of whatever size others have suggested...

But if others repeat that <whatever> is acceptable, I won't argue...

I copy, make sure any caps installed are "non-polarized". I assume the "A66 66MFD 100WV, NP 85c B12" that i have are polarized?

Thanks again Old Spark

Here are some links so you can get to know capacitors a little. You are looking for a cap that is designed to be used in a crossover function.

https://www.parts-express.com/non-polorized-electrolytic-capacitors.cfm

https://www.parts-express.com/crossover-capacitor-index.cfm

https://www.tedss.com/list/capacitors.asp

https://www.tedss.com/list/capacitors.asp?capacitance=100uF

https://www.the12volt.com/caraudio/cross.asp#hp

In your post above, the term " NP 85c B12 " refers to a non-polarized cap by the use of the NP in its name. In the " A66 66MFD 100WV ", the 66MFD is read as 66 micro farads and is aka 66 uF. And, anything you buy that has the name "bass blocker" is intended to be used with AC audio and would be non-polarized. You just match the impedance (eg 4 ohms) of the cap to the speaker.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Thank you very much for the links Steve, ive been up all night on the internet trying to research a better understanding of capacitors.

I called the local radio shack, they have some 100uf, 50v 's. What is the audible effect difference between a 100uf and a 66uf? The 66uf's i have blocked alot of bass, id like to let more mid bass pass through if i could.

Thank you

https://www.the12volt.com/caraudio/cross.asp

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Radio Shack sells nothing larger than a 10 mic in a non-polarized configuration. I have seen many 50 volt caps exploded on tweeters on coaxial speakers. I have never seen an exploded 100 volt device.

Thanks for the link.

The 100v spec is well worth mentioning as the difference in cost is negligible.

I never go to RS for small parts, either drive to a Frys or Vetco, or order online from Parts Express which I'm really happy about.

These guys know their stuff and will reply to emails and take phone calls.

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I know just enough to be dangerous. VERY dangerous.

Thanks for the advice "i am an idiot", you got that right about the "shack". I went there and asked about the 50v cap. The pumplefaced kid (no offense to pumplefaced kids elsewhere) was clueless about my questions and obviously didnt care. Then the "manager" acted like he knew about them before telling me that "you dont put caps on car stereos".... So im gonna order them online. But before i do, does anyone know what the difference in sound is between the 100uf and the 66uf that i have now?