Need Help with DIY home theater speakers

Nebuchadnazzar · May 24, 2006

I'm trying to build a set of 2 speakers, they are 2 way using a 7" woofer and tweater. They are sealed speakers.
Woofer: http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-364
Tweater: http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=275-070

I built an enclosure out of 3/4" MDF, which is about 8.5" x 8.5" x 16" internally. The problem is i'm not getting alot of bass, the low end seems really quiet compared to the mid and high frequencies.
I did a frequency sweep and by ear it sounds like the volume gets lower as the sound goes lower than 400Hz.
I'm wondering if the problem is the enclosure size. If the box size is the problem what size box should a speaker like this be in?
The boxes are internally padded with eggcrate foam and i'm using a basic 2nd order 2000Hz cross over (which i put together).
I am using an old Marantz 2240B reciever which i think is good for 40 watts per channel. My dad thinks the problem is the reciever, but i think it's the enclosure size.

I have a 2ohm resistor (10W) in line with the tweater to drop it's sound level down to that of the woofer's.
When I crank the bass through equalizers (and the bass knob on the reciever) it can do some serious thumping, so i know it's capable of some hefty bass.

Korndog · May 24, 2006

i've heard lots of good things about the dayton rs and bass, but its really better to go with a vented alignment with that speaker to get the bass. most of the articles i've read on the dayton rs recommend crossing at lower freq though, like when i was considering it, i was gonna go 1.4khz with a 4th order crossover to avoid the cone breakup, but it should still sound pretty good.

Nebuchadnazzar · May 24, 2006

Thanks for replying so fast, The speakers do sound nice even though i'm listening in mono right now. I'll get the second enclosure done by this weekend and i'll post some pics.
After listening to 'em more, they are starting to grow on me. I'm thinking in the future i may get a seperate subwoofer to fill out the low, but that won't be for a while.

Korndog · May 24, 2006

would u consider making a vented box? it'll make a big difference in the low end, unless you're low on space :-/

i donno, space hasn't been an issue for me (except in my car, can't go beyond 5cuft dammit)

shard · May 24, 2006

Korndog said:
would u consider making a vented box? it'll make a big difference in the low end, unless you're low on space
i donno, space hasn't been an issue for me (except in my car, can't go beyond 5cuft dammit)

Turn the whole car into a box, use the trunk, back seat, and passenger seat. And say amen to yourself.

Nebuchadnazzar · May 25, 2006

I could make these vented boxes, but i'm not too sure how. I'm fairly new to this so i wouldn't know what diameter, length or material to use.
Space isn't an issue, these speakers will just sit on my desk.
Does it matter where the vent is, like just above and to the side of the woofer?

shard · May 25, 2006

Actualy, you can just put the port out the back, about level with the tweeter.

Nebuchadnazzar · May 25, 2006

Hmm i found WinISD and i put in the woofer, i noticed that i get a nice responce with 0.75" length and 0.81" vent diameter. I'd assume that all i'd have to do is drill a hole 0.81" in the back of the speaker? Or would it be better to get some PVC piping and make a 5.65" long and 1.85" diameter vent?

Korndog · May 25, 2006

you'd want to go with a pvc pipe and make sure its wide enough to avoid port noise. a 2" pvc pipe should be okey, you can put it in the back or the front or up or down. Hell, i've even put vents on the front and speaker on the top, its all good.
btw winISD is a great prog, r u using pro or beta?

Nebuchadnazzar · May 25, 2006

I'm using the pro alpha version

Nebuchadnazzar · May 25, 2006

Ok so i drilled a 1 inch hole in the back and it definitely sounds different. I managed to find some 1.5" PVC tubing so i'll try that later.

Edit: I'm trying to figure out what Tuning Frequency means, but i'm having a little trouble. With the hole in the back, i have a 9KHz Tuning Freq. That seems really high from what i've read, but i have no idea what it is or where it should be.

2nd Edit: MY bad i was looking at 1st port resonance value in the vent tab on WinISD, does this value matter at all?

Korndog · May 25, 2006

you want to set the port freq which keeps the responce flat. with that speaker winISD recommends 40hz in a .722cuft box.
from the measurements u posted it, ur box is .669cuft, which is fine 1.5 pipe would create lot of port noise though.. you can put TWO of them and that would solve the problem, but they would have to be 7.45" long each. that would tune it to 41hz which would get u a lot of low end.

its a bad idea to just make holes in ur box and play the speaker, probably won't do anything because u only have 40w, but its not a good idea..

Nebuchadnazzar · May 25, 2006

I could get some 2" PVC tubing, if that will decrease the port noise. It would need to be 6.3" long, which is fine and will give the 41Hz tune you suggested.
Unfortunately where the hole is now, i won't be able to put in a 7.45" pipe in because the tweater on the other side. I'll want to keep it to 1 port.

Korndog · May 25, 2006

2 is fine, i was just trying to match with what you had.
you'll also want to make sure theres atleast an 1" worth of clearance on the other side of the port (inside the box)

Nebuchadnazzar · May 27, 2006

Hi i put a 2" port in the back and it sounds good, i'm keeping the volume low until the onkyo (SR503) reciever i ordered arrives. With the marantz reciever i heard a bit of crackling at high volume and i jumped to turn it down.

Here's some pics of the speakers:
This is the first one, finished

Here's a pic of the port sticking out the back of the speaker

The second speaker should be done tomorrow, here it is under construction

Korndog · May 28, 2006

wow, great job on teh wood work
yea, you don't want to push the amp to clipping, even if its low power, it can damage the tweeter and maybe even the woofer.

denz_1 · May 28, 2006

Crackling? Probably not enough power to drive them correctly
I would try with some propper baffeling insteed of egg cartons eh

Nebuchadnazzar · May 28, 2006

denz_1 said:
I would try with some propper baffeling insteed of egg cartons eh

Well it's not eggcrate carton, like cardboard. It's actually a foam the resembles an egg crate shape.
It's like this:

Korndog · May 28, 2006

that rubber foam stuff works pretty well on getting rid of the backwaves that cause a little bit of distortion in the speaker. if you really want to make a difference though, you should get some polyfill which might help getting more bass.

Nebuchadnazzar · May 30, 2006

I finished the second speaker, and the new reciever arrived. The speakers sound great and they have no problem with high volume. The bass sounds good too but i upped it a bit through the reciever, the bass really kicks in at higher volumes.
Thanks for your help guys.

Need Help with DIY home theater speakers

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