Quote:
Originally Posted by coreyL
hmm i think its the combination of having no crossover and needing to be polyfilled in that case. the tweeters are much more effecient than the woofer and make it almost ear piercing when turned up high, the bass isnt as much as i would like. to solve this: i'm thinking i should polyfill it, make a crossover and make a porthole, yourthoughts?
|
Polyfil is cheap and can't hurt. Just buy some and stick it in there, I'd never build a speaker without at least polyfil inside. PE also has more expensive stuff that's meant for the inside of speakers, but I'd say it's not worth it for your experiment (unless the drivers are really good).
Quote:
Originally Posted by pioneerisloud
1) A crossover is only going to cure at the crossover point. You'll need 2 crossovers, a high pass for the tweeter, and a low pass for the woofer. These can be bought at partsexpress.com in the "speaker building" section. Or you can look up the values and build one yourself from the12volt.com. High pass is easy, as its just a capacitor inline with the positive. A low pass is considerably more difficult, I'd suggest you buy those for your first build.
2) Polyfill only makes the speakers think the enclosure is bigger, and prevents vibrations of the box. With small drivers, that's not an issue. Until you get a 12" subwoofer running 1000w RMS to it, you won't need to worry with 3/4" MDF. Again, the crossovers will help, but they won't help your bass response any. You either have the box built wrong, or your drivers just suck at bass.
3) Portholes? You're essentially going to just cut holes in your enclosure? That's not a port. You would essentially be turning the speakers into free air. This is probably part of the reason already why you have such lacking bass response (you said you have holes in the back). If you're going to go ported, you need to do it CORRECTLY by using software to determine the proper lengths and widths of the ports, or you should go sealed.
|
I'd agree sealed is safer. Stick to that if you don't know the specs of the woofer.
A crossover is more than just a single capacitor...that's the bare minimum since it's a pretty shallow slope (6dB per octave). Second order is a coil in parallel and a cap in series IIRC, and you keep adding components from there (in a certain configuration obviously).
I don't see how a low pass filter is any more complicated, first order is just a single inductor (coil) in series with the woofer
. Coils can be expensive though.
Quote:
Originally Posted by coreyL
heh, it would be nice if i rally knew for sure what model of speakers these are. looks like im going sealed for the time being. i need to get some furniture grade plywood. are you sure partsexpress has quality pre built crossovers?
|
Yes, just keep them sealed for now. You could just get those, or spend a little while with a xover calculator and buy the components yourself. Don't bother with expensive caps or massive coils right now, it's kind of a stab in the dark anyway, so there's no point in wasting money on an overkill crossover.
Quote:
Originally Posted by pioneerisloud
So measure them with your multimeter. I assume you have a multimeter if you're building speakers and crossovers.
|
Quote:
Originally Posted by coreyL
i didnt even know my multimeter could measure ohms. should i measure it while playing music is will it measure fine with nothing playing?
ive been whinging it pretty much the entire time lol. ill upload some pics of what ive got so far in a bit.
|
Unplug the speaker completely. Then use the multimeter to measure across the two connections on the speaker. Switch it to one of the lower settings. The multimeter only measures DC resistance (Re). That will give you an idea of the impedance, but most likely it will be below it. For example if it measures 7.32ohms it's most likely an 8 ohm driver.
Just a side note, when you set the multimeter to the ohmmeter section, it sends out a small current through the lead and then measures resistance by how much current/voltage is actually received at the other lead. So if you touch it to a live wire or speaker when using the ohmmeter you could damage it.
Quote:
Originally Posted by FearSC549
Corey, your speaker enclosures does not have a single bracing, which explains the resonance/vibration. Add some bracing inside to decrease vibration.
|
Honestly, you don't need that unless the enclosures are extremely poorly built. In that case I'd tell you to take them apart and cut the pieces over again anyway.
Quote:
Originally Posted by coreyL
couple questions. im in the process of my first bookshelf build. they sound like they are resonating but they are made completely of MDF. is this because it isnt completely finished and i have 2 small holes in the back of the bookshelves in which i will fix soon, or because i havent polyfilled them yet?
also whats the best way to go about making a simple crossover? i plan to make the 6.5 inch polk drivers cross over at 3000 htz to the tweeters somehow.
one more thing is, i know veneering this will be extremely hard, so im thinking ill get 1/4 inch cherry furniture grade plywood and stain/poly it. cutting the 45 degree angles will suck. i dont even know if the tablesaw at my house can do that. i might have to use a router.
|
'resonating' is extremely vague. What are you hearing? Really loud midrange peak, bloated bass peak...
TBH you need some damping material inside. I also highly recommend the foam gasket tape on partsexpress for sealing the gap between the driver and enclosure (baffle). Are the enclosures sealed up fairly well?
If you're still lacking bass the drivers may need a ported enclosure, but like many of us have said is pretty hard to get right without knowing the
thiele/small parameters. If you go too high you'll get one note of bass, if you go too low it might not do much of anything.
Last thing, you NEED a crossover on the tweeter. Any significant amount of bass getting to the tweeter could fry the voice coil. Even if it's only a single capacitor at first. You shouldn't be using a tweeter without a cap on it (use a crossover calculator to find a rough value, usually 2+ kHz). For permanent use, consider a second order (-12dB per octave) where you intend on crossing it over (read around on the12volt like pioneerisloud suggested).
Honestly, there is a ton of information you need to know about speaker building at first and it can be kind of overwhelming, but don't let that discourage you. Just be a nerd like me and spend hours reading about it
.
