Passive Radiator

[MusicStudent1]

Those small bass amps were never meant to produce solid low end. They are made to provide a little volume for your bedroom practice sessions. You are not likely to find one that is a tone monster. I built a lot of those little buggers in my 10 years at St. Louis Music (Crate and Ampeg). Even the little Ampeg amps really don't sound all that great. They are limited by size and power.

Bass frequencies require air movement, and that requires power. Even if you use the chassis to power a larger cabinet, while the tone will definitely get fatter, you still won't have enough power to move the air necessary to get solid fundamental tones at any kind of volume.

No way - you built Crate amps?! I have very fond memories of Crate. For me, they were very ‘80s. They were in all the guitar shops, they were pretty loud (good for playing Quiet Riot songs with, lol) and they were fairly inexpensive.

You are correct about everything you stated. This will just be a low cost project for practice and maybe recording.

Last year, I built a wired stereo enclosure for my iPad out of a $20.00 wine box and used two $4.00 speakers and a $20.00 amp. I plugged in my iPad and played some subwoofer bass demos...you wouldn’t believe the bass response. Too loud, and the voice coils will burn out but at a low volume, the bass is ridiculous. The box is sealed and the little 4” speakers don’t move that much but somehow the bass is there! (Just not very loud).

That little project sort of inspired me. Heck, I could just plug my bass into it and see how it sounds, come to think of it but I’d rather make the next one a tad bigger and power it with my bass amp.

[PJSprog]

No way - you built Crate amps?! I have very fond memories of Crate. For me, they were very ‘80s. They were in all the guitar shops, they were pretty loud (good for playing Quiet Riot songs with, lol) and they were fairly inexpensive.

Yeah, it was a fun time in my life. I started out working on the assembly line in the CAT Department (Chassis Assembly & Testing). We put the assembled pc boards, transformers, and wiring together in the chassis, and tested them. Spent some time making wire harnesses and testing and grading tubes. I eventually became a packer, then a sound tester (coolest job on the planet, getting paid to sit in a sound booth testing amps all day), and then line leader / electronics tester / technician. The last four year there I was in Quality Assurance.

Most of the Crate line of stuff was indeed inexpensive. It was from the start geared towards the beginners market. Those little 15w GX-15 combos? We made in the neighborhood of 25,000 of those things a year. Some of the latter days tube amps were not as inexpensive, though, like the Blue Voodoo series or the Vintage Club series. The VC-5212 combo is still my favorite Crate amp, and I still have a VC-120H head ... which I no longer use since I bought a Helix.

When we closed that facility, the last thing we ran on the production line was a limited reissue of the original CR-1 combos ... the ones that looked like an actual crate. I tried to get my hands on one, but they were all made for the sales staff and certain retailers who'd been with us from the beginning. It was pretty neat to build and test those.

Lots of great memories from that place. It closed in 2003, but a bunch of us still get together every year and have a little reunion. Good people who had fun making music equipment.

[MusicStudent1]

Lots of great memories from that place. It closed in 2003, but a bunch of us still get together every year and have a little reunion. Good people who had fun making music equipment.

Thanks for your post! You can tell the group the next time you’re together that I was a huge fan of Crate amps. I was just a kid and was trading stuff, changing guitars, etc, etc. I regret trading in my Crate gear.

One guy I played with in the 1980s had one of those combo amps and it sounded great to me. I think it was a 20 watt amp but it could’ve been a 15. We played some simple Ramones songs together, he was using a Gibson single cutawaygguitar called “The Paul” with the Crate. His tone was outstanding.

I sometimes think in the quest to get the perfect sound, perfect guitar, etc. we don’t realize we had it right all along!

[fender3x]

I would stay away from passive radiators. My understanding is that they do essentially the same thing as the port on a reflex cab. They are not necessarily any louder or better. I agree with Jim that there is a fair amount of science that goes into designing a good bass cab--which is not to say that every cab out there is a good one....

If you are building it's a good idea to "tune" your cab to the speaker you will be putting into it. There are a number of calculators for this on the internet, such as the one below.

http://www.mh-audio.nl/Calculators/R...alculator.html

I haven't done it for a while, but there is also some free software you to help you design dimensions. I can look for it if you are interested.

I think Simon is right that there there isn't necessarily much difference between the woofer in a PA and a woofer in a bass cab. Lots of Eminence speakers are used in both. That said, if you are bulding a cab you want to get one with published specs so you can tune your cab to the speaker you want to use.

Another thing to watch out for is that small and cheap speakers may have (a) a low power rating, and (b) too short "excursion" (a.k.a xmax--the distance the voice coil can travel to move the cone) for bass.

Think of it this way. Bass sound waves are much bigger than guitar sound waves. To produce the low E on a bass you have to move a lot more air than you do for a low E on a guitar. All things being equal a small cone will move less air than a big one. Higher Xmax will help a bit since it will allow the cone to move farther. Exceed the Xmax by turning up the volume too high, and the voice coil can jump out of it's spider or housing. That's never happened too me, but what has is a melted down voice coil. This happens because speakers have a maximum volume that they can produce. However when the speaker reaches that point, I might still want more volume--more power to a speaker that has reached it's maximum volume results in heat rather than sound...and, in my experience, also a bad smell then silence.