My NATIONAL RX-A2 ** Project Better BASS!

[Cpl-Chronic]

Hey boombox bastiges!!

What's crackin? I decided to tackle another legend of the 14" & higher club....The mighty RX-A2 is a loud powerhouse of a blaster that can burn through 10 D-Cell(s) in about 20 minutes. Some swear they get a solid 30 watts a side even though it rates at 15 per side RMS I believe.

The only drawback is the woofers that favor raw SPL's(volume) at the cost of bass & warmth or what some call presence. I wanted to fix that, same as I did on the RX-A5 which I tend to think is a success & another sleeper power-hammer waiting for the right speakers.

So I bought these goldwood premium woofers & tried to fit them in & they just barely squeeze into the tight cabinets by literally 1mm. I still have the originals in perfect condition too. Check out the difference between the 2...

https://www.youtube.com/watch?v=eccGht1Un_8

 

[Lasonic TRC-920]

This is a radio that can certainly stand for a woofer upgrade. LOUD AS HELL Already, but at the time they were made, they hadn't reached a full understanding on how to get that power to the ground.

This project is gonna me a HAMMER!

 

[Reli]

Nice.

Yeah, the A2 was made to be like a public broadcasting system, like for a marching band conductor or something........So low-volume bass wasn't a priority

That being said, it's got crystal-clear sound and great build quality.

 

[mellymelsr]

Wow! That really sounds good.

 

[Cpl-Chronic]

Thanx guys!! The new woofers are very efficient, 90db/1w/1m/1KHz & the unit is still very loud, very powerful & sounds very good now. The only glitch is that when listening at low volume I get a hissing scratchy noise in the left channel but when you press play, RR or FF, it goes away completely. If you have loud music, it goes away completely....

Not sure what it is...

 

[Lasonic TRC-920]

I have very limited exposure to these boxes, but if you wanted too, by it's very design and the way the speakers are stored, couldn't you make new speaker enclosures and still have them stow away with the factory mounts? This way you could make larger sealed speakers with ports or what ever you wanted.

 

[Reli]

Part of the problem is the speakers mount against the back of the wood panel. You could get more space my mounting them against the front instead.

I seem to recall mine didn't even have any fiber insulation inside. The plastic shell is nice and thick, but would sound better with proper fill & sealing.

 

[floyd]

This setup will pound with some proper horn tweeters.these will compensate for the loss in sensitivity from the woofers.

 

[Cpl-Chronic]

This setup will pound with some proper horn tweeters.these will compensate for the loss in sensitivity from the woofers.

Well, managed to dismantle the A2 main unit & fixed the 'L' speaker jack that had a bad solder joint. The hissing still plagues the left channel unless I engage 'Play' on the deck, then it's quiet again...If anyone know how to fix this, let me know...

Now, I have to sort out some rattles & add some rattle trap deadmat & some fill, seal leaky screw holes etc. in the speaker cabinets. Also, have to change out the crossover caps(4.7uF) to 6.7uF values to bring the mids out more. This will address the issue JVC floyd mentioned about having horn tweeters. The old tweeters were matched to a paper cone woofer which goes higher in the midrange than the new woofers.

Pics coming soon...

Cheers,
Cpl

 

[Cpl-Chronic]

OK. Added Deadmat Rattle Trap sound deadener. I also experimented with venting the magnet's center hole to the outside through the rear of each cabinet. I used an old cologne cap & cut the cylyndrical portion of the cap in 2 pieces & filed them to the proper heigth & epoxied them to the magnets of the speakers, directly over each vent hole....see pic below...

Once the epoxy set, I drilled & filed a round hole in the rear of each cabinet to mate with my homemade coupler & used Rattle Trap deadmat material on the inside of the cabinet, around the hole to act as seal around the edge of the palstic riser.(see pic below)

More to come.....

Cpl

 

[Cpl-Chronic]

I didn't have any 6.7uF caps so I used 3x 2.2uF polyester film capacitors, wired in paralell, to make a 6.6uF crossover. It sounds very good, very clean mid/highs...especially for a 1st order crossover on a portable mixer from the early 80's...

Here, you can see the deadmat & insulation I used in each cabinet to deaden any relfections & smooth out the repsonse of the cabinet to the woofer.

Here it is, all put back together & booming hard......

I think the sound is 100% better than yesterday, after the deadmat, insulation & rear venting tube....
Videos coming soon...

Cpl

 

[floyd]

venting those cabinets was the way to go, nice work !.

 

[Reli]

The vent doesn't make a whistling sound or anything like that?

 

[Cpl-Chronic]

The vent doesn't make a whistling sound or anything like that?

Hey! No, the cabinet is still airtight & the air from the center of the voice-coil is vented directly to the outside, instead of into the cabinet space. The difference in sound is HUGE!! Bass is extended & clean now...

In this pic you can see all the way down the vent to the screen that protects the voice-coil from dirt & dust, which is about 2" down into the magnet of the woofers.....

Video coming shortly....stay tuned...

Cpl

 

[Lasonic TRC-920]

The vent doesn't make a whistling sound or anything like that?

Hey! No, the cabinet is still airtight & the air from the center of the voice-coil is vented directly to the outside, instead of into the cabinet space. The difference in sound is HUGE!! Bass is extended & clean now...

In this pic you can see all the way down the vent to the screen that protects the voice-coil from dirt & dust, which is about 2" down into the magnet of the woofers.....

Video coming shortly....stay tuned...

Cpl

Whoa, that's a cool idea, crazy how the new speak dimensions allowed this to happen. Total factory look with bruiser output!

 

[Cpl-Chronic]

Ok, after adding the better caps, venting the magnets & adding the blanket insulation/rattle-trap materials, she rocks & has more midrange presence too!!

https://www.youtube.com/watch?v=7Ltq_DGyaAY

I'll post some more with some different music soon.

more to come...

Cheers,

Cpl

 

[Cpl-Chronic]

1st up....my favourite test......BASS!!! This jam is insane off the charts & the camera only gets a part of the cavernous tremours coming out of this monster!!! I bet this thing burns through 10 D's in 10 minutes the way it's modded now... :frankenstein:

This thing is a fuk'n hammer....

Video coming in about an hour.....


cpl

 

[Cpl-Chronic]

!! WARNING !! HEAVY BASS ENVIRONMENT! Use a good pair of HD headphones or a full range sound system or you will miss the bottom octaves on this recording. At one point I walk around to show how far the bass carries through the house. Remember, this is a video of a boombox playing this song....

https://www.youtube.com/watch?v=pUNfUDzQSr8


Cpl

 

[Cpl-Chronic]

Ok, time for the Master Blaster...

https://www.youtube.com/watch?v=TJfBS1wvq-E


Cpl

 

[Cpl-Chronic]

I might post a video of both modded A series portable studios, the A-2 & A-5 for a kick! Talk about 2 heavy hittin' back breakers. You can barely call them portable audio, let alone boomboxes.

Stay tuned...

Cpl