Use of capacitor across the leads of stock Taiwan Cobra 148 GTL speaker?

[Pioneer621]

I also find it hard to believe a 0.001uf capacitor would have any effect on audio across speaker wire. That cap is used for keeping RF off, or at least minimizing RF on the speaker / wires / audio circuit, not shunting audio treble frequencies. I would transplant the capacitor to the new speaker to keep it working as intended.

I guess it is technically a hi-cut filter if you count cutting 27mhz as the hi-cut frequency.

Out of curiosity I looked up a capacitor impedance calculator. a 0.001uf is 53,000 ohms at 3khz, where at 27Mhz it is 5.8 ohms. There are other variables to how it is going to actually function in circuit, but it gives an idea of how little that value effects the audio spectrum.

I don’t have any radio gear hooked up anymore since moving, all packed in closet / basement with no plan to set it back up, or I’d do a test and record the audio. Anyway, just seen the thread and thought that's just an RF bypass cap when looking at the OP's photo, so figured I'd add my 2 cents worth since there seems to be varying opinion on it. In a production radio like a 148, a tone control / audio hi-cut would be implemented at the audio amplifier input, not at the speaker. Just my thoughts on this.

 

[nomadradio]

Just my thoughts on this.

Dead on, sir.

73

 

[Handy Andy]

I guess it is technically a hi-cut filter if you count cutting 27mhz as the hi-cut frequency.

​

Out of curiosity I looked up a capacitor impedance calculator. a 0.001uf is 53,000 ohms at 3khz, where at 27Mhz it is 5.8 ohms. There are other variables to how it is going to actually function in circuit, but it gives an idea of how little that value effects the audio spectrum.

Oh how nice it is when someone comes along and answers the question​

"Out of the mouth of Babes..." Ps 8:2

Just replaced an old Taiwan Cobra 148 GTL's speaker that was getting raspy sounding at low volumes with a brand new Workman SA-350 3.5" replacement speaker, did the trick. The old speaker has a small cap across the terminals, (see attached) and the new one doesn't.

Ok, everyone thinks this is an RF issue - and yes, you can say it is - but don't forget what happens when RF mixes in audio somewhere - where it shouldn't. Damage can occur.

It's as simple to remember too - Ohms law and how an impedance like a coil a speaker has - can also induce a problematic issue of impedance. Connect the wrong type of speaker in a crossover - you'll lose both the equipment and speaker eventually - so by answering the RF question using an ohmic result - it is why the "intangibles" of life out on the road or in any environment - the issues of speaker construction and it's ability to withstand abuse so it's SERVICE life can be extended - comes into focus.

Not everything made of fibrous paper and plastic lasts forever nor does the means of it's thin-line construction and short throw of coil - constructed and chosen to save space inside the spyder cage and the clamshell case for the rest of the radio - for clearance - let alone it's power capacity and rating

The Cap works better versus using a resistor - as to increase the service life of the speaker by lessening the changes of high-tone/frequency altering the "color" of the sound reproduced.

"Can't See The Forest Through The Trees..."​

You guys need to get out more...

 

[Shadetree Mechanic]

Oh how nice it is when someone comes along and answers the question​

"Out of the mouth of Babes..." Ps 8:2



Ok, everyone thinks this is an RF issue - and yes, you can say it is - but don't forget what happens when RF mixes in audio somewhere - where it shouldn't. Damage can occur.

It's as simple to remember too - Ohms law and how an impedance like a coil a speaker has - can also induce a problematic issue of impedance. Connect the wrong type of speaker in a crossover - you'll lose both the equipment and speaker eventually - so by answering the RF question using an ohmic result - it is why the "intangibles" of life out on the road or in any environment - the issues of speaker construction and it's ability to withstand abuse so it's SERVICE life can be extended - comes into focus.

Not everything made of fibrous paper and plastic lasts forever nor does the means of it's thin-line construction and short throw of coil - constructed and chosen to save space inside the spyder cage and the clamshell case for the rest of the radio - for clearance - let alone it's power capacity and rating

The Cap works better versus using a resistor - as to increase the service life of the speaker by lessening the changes of high-tone/frequency altering the "color" of the sound reproduced.

View attachment 48379
"Can't See The Forest Through The Trees..."​

You guys need to get out more...

Thanks for painting the picture!

 

[Shadetree Mechanic]

I also find it hard to believe a 0.001uf capacitor would have any effect on audio across speaker wire. That cap is used for keeping RF off, or at least minimizing RF on the speaker / wires / audio circuit, not shunting audio treble frequencies. I would transplant the capacitor to the new speaker to keep it working as intended.

I guess it is technically a hi-cut filter if you count cutting 27mhz as the hi-cut frequency.

Out of curiosity I looked up a capacitor impedance calculator. a 0.001uf is 53,000 ohms at 3khz, where at 27Mhz it is 5.8 ohms. There are other variables to how it is going to actually function in circuit, but it gives an idea of how little that value effects the audio spectrum.

I don’t have any radio gear hooked up anymore since moving, all packed in closet / basement with no plan to set it back up, or I’d do a test and record the audio. Anyway, just seen the thread and thought that's just an RF bypass cap when looking at the OP's photo, so figured I'd add my 2 cents worth since there seems to be varying opinion on it. In a production radio like a 148, a tone control / audio hi-cut would be implemented at the audio amplifier input, not at the speaker. Just my thoughts on this.

Great explanation, thanks!

 

[codecxbox]

not a RF tech, mostly audio stuff..
This remembers of those nasty Class H Technics amps, that blew non crossover speakers like nothing, welcome to copper coil smoke..those ICs were supposed to open in-chip diodes, but what I saw was 56 volts DC at the speaker connectors..