The shocking "inside story" from a speaker driver replacement of a "boom box"

[sdasgupta]

Folks, I recently had to open up the speaker-cabinets (if I may call them that) of my old Sony boombox to replace the blown mid-bass drivers. What I found inside really surprised me - the drivers were really puny! Anyway, let me lay out the story in proper sequence.

I have this old Sony CFD 550 "boom box" which I had bought more than 20 years ago while in the US.
This is how it looks (photo from the net)


It had been lying around unused (the tape belts are broken and the CD lens does not work anymore) and a few weeks back, I decided to use the speakers from this setup with my NAD C350 amp which was lying around, as my computer audio setup. I was not looking for great sound, just some background music while I worked. So, I connected the speakers to my NAD, and used a Centrance Dacport to connect my laptop to the amp.

I had just started enjoying the music and tried cranking the volume up a bit, when suddenly, the speakers went silent. Or rather, only the small tweeters could be heard, but not the mid-bass drivers. I guessed I had blown the drivers. I had known this could happen because I was sure the speakers were not designed to handle the 50W+ that the NAD could put out. OK, time to replace the drivers.

So I brought out the heavy artillery...



And started opening up the speakers boxes....

Now, this is how the boxes look close-up. Note the "Megabass" branding...



And then, on opening up the rear-panel and exposing the drivers - what a shock!


A 2.5 W driver !! What was Sony thinking? A "Megabass" "boom box" with a 2.5 W driver? I had no words... No wonder my NAD had killed the drivers on both channels! And note that these were 3.5 ohms, meaning the output would have been higher.

And no cross-overs either! This setup is worse than some of the old transistor-radios I had opened up back in the days.

And look at the cone, how do you expect any bass, forget "megabass" out of this cone?


Anyways, time to replace these, what do I use? Remember, I just wanted some decent music, so instead of going for some expensive drivers, I decided to use cheap car stereo components.
Went out and got these


The packaging claims these go up to 190W! I am sure that is a little overboard, but with these, I am reasonably safe, as I do not intend to go to loud in this setup.

Here is how the driver looks after opening the package - 30W nominal, 4 ohms, good enough..


And here is how the speakers look after the install..


And then, I set up the ASIO4all driver on foobar2000 to start enjoying bit-perfect sound through the system. The drivers are not great, obviously. The bass is not much better. But it is good enough for my background listening needs.

 

[mpw]

A misprint. There shouldn't have been a decimal point at all. !

 

[hifitoaster]

Some years back, tried to fry a BPL boom box speaker with a MOSFET 50 w amp, it didn't give up after 25m of playback at loud volumes. Plus they sounded much more nice when connected to that amp. But my aim was only to see if smoke and fire comes and I gave up at the end. Anyone remember old dumb boom box from BPL? Model number was cw111, since I was a child it was there at the home and I happen to memorize the model number printed on the panel seeing it every day. now looking back I am sure it was one of the worst things money could buy.

 

[reubensm]

Its the old story - PMPO vs RMS. Back in the day, Philips, BPL, Videocon, etc launched powerhouses and boom boxes claiming 5000 watts PMPO and stuff like that. Though it was a case of openly misleading people, since references were not available, most fell for it

 

[sdasgupta]

True. And BTW forgot to mention one thing - the fake bass-ports at the bottom! The enclosures are neither airtight nor do they have any insulation foam. They are just plastic boxes. Marketing and design folks had a great time while fooling customers with the PMPO, Megabass and bass port gimmicks, I guess. But there was one from Philips called the "Powerhouse" I guess, that did have some thump. Listened to one back in 1992 at a friend's place. He was blasting it at high volumes to show off, and what a muddy bass that was. Yes, things around the system (and the system itself) were jumping around, but you couldn't have called it "music" by a long shot.

<"Some years back, tried to fry a BPL boom box speaker ..."> Yes, I do remember them. But I believe all India-made music systems were sturdier than these fancy Japanese ones. Small BPL tape recorders went much louder than my Sony boombox, and when I was in college, I remember removing the full-range driver from my "Santosh" tape recorder and using it in a "matka" system (anyone has experience with those? ) with a local 80+80 W rated amplifier kit, and played it a typical hostel room volumes. It did duty for 2 years without any complaints. So these Indian systems did have pretty sturdy drivers in my opinion, though sound sophistication was pretty low. They did mid-ranges well and could go loud - and that's all you needed in those days.

 

[abhinaba]

I remember removing the full-range driver from my "Santosh" tape recorder and using it in a "matk

Yes our old matka sub woofer