What is the effect of a speaker capacitor?

[Jovie]

Its my understanding that a tweeter cap filters low frequencies for the speakers protection.If this is correct,all woofers (main speakers) on a boombox produce full range sound.The tweeters are there merely to assist the main drivers so a boombox can produce full ,sharp highs without their compromise.Of course,different capacitors can have different ratings.Given this,I'm wondering what would be the effect on the sound if I replaced caps with different ratings?More signal could only mean reaching down into the midrange.This could only result in a boombox producing more overall sound if I understand things correctly.

Am I getting this?If more mids were sent to the tweeters,could it potentially "brighten" up the sound of a box?What are typical cap ratings used in boomboxes?Which values send more sound to the tweeters?Also,what other effects might this have on the sound?I love bright,noisy sounding boxes so I'm considering such a modification.

 

[Fatdog]

I've wondered the same things, Jovie. Maybe they are used as a sort of "crossover"? I bet Frizzle would know about this. Where are you, Freddie?

 

[oldskool69]

I offer the linky below as it sums it up quite well...(And saves me an assload of typing! ):

http://www.members.shaw.ca/LoudspeakerBuilder.ca/crossover.html

 

[MasterBlaster84]

Great link Oldy.

That means full frequency to the woofer and only highs to the tweeter (Low Frequency filtering determined by the rating of the capacitor).

 

[Fatdog]

Very nice link, oldskeezy.

 

[Superduper]

Bottom line is that capacitors block DC (direct current) but passes AC (alternating current). Audio output is AC. The frequency of the signal passed is determined by the value of the capacitor. By changing the value, you can alter the frequency of the signal passed to the tweeters. For obvious reasons, be careful when experimenting since the tweeter is quite prone to damage from too much low frequencies. If you do want to experiment a bit, remember to use bipolar capacitors and NOT the standard polarized electrolytics. They look much the same except that some manufacturers color them differently to make them more easily identifiable. Polarized capacitors will have a polarity marking, usually (-) negative but I've also seen them marked for pos (+) polarity too.

 

[Jovie]

Thanks all for your very informative input Now to address the rest of my query,what will be the affect to the sound if more is sent to the tweeters.Will tweeters handling more of the midrange cause this range to be produced any differently? My imagination and supposition tells me that a tweeter reaching farther down into the mids would give a more forward (what I like to call "brighter" ) sound.Of course moving the 1k slider to the top will also create a similar effect.I'm just wanting to know if a cap change might also affect the sound in this way if I refit a box without an equalizer.I hope you guys understand what I'm getting at as sound,unfortunately,is very subjective.

 

[Superduper]

The question is how much of the dymanic range your tweeters can handle. Factory engineers probably calculated the high pass capacitors to match up well with the factory tweeters. Certainly, the full range of the spectrum is already being sent to the woofer. Most boombox woofers are pretty much full range drivers anyhow. The tweeters are added to "beef" up the highs and add more sparkle. The results to the reproduced sound when shifting some midrange duties to the tweeters can probably only be known by experimentation since each driver (including the type of tweeter such as a piezo or cone type, whether it's shrouded, has a horn lens attached, or just open) all makes a difference. My guess is that unless you change the tweeters to something else, the factory caps are tailored to the factory tweeters and adding more midrange might not necessarily be helpful.

 

[Jovie]

This was the issue prompting my original post.I've had a Lasonic LPC-990 with unsatisfactory highs for some time.There is only one shop in town that will even touch an old boomer.They are OK for deck work,general check overs,cleaning,etc. but not so much for anything more involved such as mods.

I took the 990 into the shop to see what was the problem.He told me that the tweeters were working OK.Having previously heard a very basic description of the affect of caps on tweeters,I told him to change the caps to see if he could brighten up the sound for me.After he had done this,he told me that he could hear a difference.A family member in the area picked up the box from the shop.When i was finally able to test it out,it sounded pretty much as it did when I had dropped it off for service.

Then I decided on a plan "B".A long time friend has recently learned to solder as he has gotten into repair of old video game consoles.I took the box to him last night to see what he could do.We opened the speakers to see what had been done at the shop.We saw rather large caps soldered in with a value of "8". The tweeters were barely dripping out sound.He then found some "4.7" rated caps to replace these replacements.There was a big difference! The music was no longer compressed sounding.It was like a veil was removed and the output brightened up considerably.This box now sounds pretty amazing.It always had good bass but it was really needing a lively top end.Now,I can imagine this sounds as the factory intended.

This made we wonder what were the ratings on the original factory caps.Calling the shop,I was told the originals had been thrown out.He was able to tell me that he used a set with about double the originals ratings.Perhaps he just doesn't understand sound that well.As proven by my experimentation,he had modified the caps by going the wrong direction!

I'm really just learning all of this.It would seem that a cap with a lower value lets a wider spectrum of frequencies get to the tweeters.I decided to open my beater MacDonald Instruments box which has to be one of the brightest and loudest boxes on the planet! Its tweeters are rated at 4 ohm (as are my 990s) but the cap value is even lower at "3.3".This "in your face" sound is what I so miss in some classic era boxes.It works really great for rock!From what I've been able to figure,that old sound was the result of more power,equalization favoring the mids,and caps of lower ratings.

Now I have another question.If caps go bad,will the tweeters output decrease severely or would it simply stop altogether?I'm thinking I went to the shop with around "4.7"s factory issues that went bad,was given very restrictive "8"s which mimicked damaged "4.7"s,and I by chance ended up putting back a correct,or nearly so,value of "4.7".I'd appreciate a comment from anyone patient enough to read all of this...

 

[Superduper]

Jovie. Panasonics, JVC, et almost universally use 3.3uf high-pass caps for the tweeter circuits and Sanyo, Sharps almost universally use 4.7uf caps. I don't know what the original caps were in your Lasonic but I would venture to guess that either one will probably work for you. Deviating further from these 2 values probably isn't all that advisable.

The effects on the audio signal passed from the varying value of the high pass caps will also vary depending upon the impedance of the tweeer driver.

Also, I should say make absolutely certain that you are using bi-polar capacitors and not polarized electrolytics. Like I said before, polarized will have either a negative or positive marking for one of it's leads.