Help with my first disastrous speaker build

[Minyeko]

I just finished my first speaker-building project, knowing nearly nothing about what would be involved. I attempted to build the larger, ported version of the Encore described at partsexpress. They seemed fine to my untrained ear, but a friend pointed out that they sound like loudspeakers in a closet. I've tried them at the friend’s house with a different amp and room acoustics, with the same results. After double-checking the Crossover, I purchased an SPL meter to measure their response:

It appears that there is distortion over the entire tweeter range. I built my own cabinets according to the design. Are the drivers destroyed? Does any one know where I should start in troubleshooting? Any suggestions would be appreciated.

[planet10]

If you'd used the PE box i could point to that as paty of the problem... when someone describes a box as from a closet (or i use the term cuppy as in talking with your hands cupped over your mouth).

From experience the PE rectangular box sounds like this -- it really needs extra bracing to be considered useable. If you tried to emulkate it as close as possible you probably need more bracing.

You also need to play with damping,

Your response looks quite a bit different than the one posted on PE. Also distortion. Double-check the wiring of the XO, and the phase of the tweeters. Make sure you measure eac h box in the same place -- preferrably outside away from any obstructions.

It is possible that you got some bad parts, but you i'd rule out the other stuff.

[Lynn Olson]

I'm a little suspicious of that notch filter on the woofer. Try disconnecting it and auditioning with pink-noise - listen to one speaker at a time and ask yourself, is it better with the filter in-circuit or not? Try the same thing with the tweeter phase - listening to one speaker at a time, what sounds most natural, the most like a waterfall or a shower?

The huge and broad dip indicates real trouble in the crossover - incorrect wiring, reverse-phase tweeter, or just plain incorrect design.

When a design is in real trouble, listen and measure the drivers one at a time. Does the woofer (with crossover connected) sound and measure as it should? Does the tweeter (by itself) measure as it should? The distorted sound at HF points to possible miswiring in the tweeter crossover - inductor to ground is not connected, or worse, cross-connected to a point in the woofer crossover.

[BHTX]

Originally posted by Minyeko
I purchased an SPL meter to measure their response:

I might question that meter that was used for measurement as well.

[wigginjs]

I would really, really take a look at the crossover carefully. Maybe get someone else to look it over for you as well. Check the phase on both drivers and make sure it's correct. Also, when you measure both speakers together your SPL is lower than one individually? Check the phase of each total speaker respective to the other?

[JLC7]

I might question that meter that was used for measurement as well.

I have to agree. That's the first thing I would check. Chances are you didn't put a lot of money into the SPL meter. I know for a fact that the one they sell at Radio Shack is only good for a few octaves. Everything outside of that frequency range is way off. That might explain why the measurements look so bad.

[Cloth Ears]

Hey Minyeko!

The above advice is all good. One thing to remember, you have 2 working (if not so well) speakers. And you may be able to rescue them. For a first build that is not too bad. So, do not be dis-heartened. I am sure you will be able to fix these somewhat (but your first pair may never be perfect). And all the problems and errors encountered here are experience for your next pair (and there will be a next pair).

Good Luck!

[Minyeko]

Thanks for the great advice! I was under the impression that phase (leads being switched, and the wave being pi/2 out of of phase) was only significant for the woofers, becuase destructive interference occurs over a larger region for larger wavelengths. I tested phase with pink noise (which would be audible in the 'center of the monitor' and inverted pink noise (which would be sound like it's coming from the sides.)

How can you test the phase of a tweeter?

I am using the $50 Radio shack SPL meter. If I can make time today I intend to test response with a microphone and sweep of sine waves.

I've checked the XO several times and it's the same as the PE schematic. Should I consider purchasing a commercial crossover?

[JLC7]

Oh heck no, don't purchase a stock crossover. Don't even think about it.

That radio shack meter is definitely way off. I had one for a few days and did some comparisons. It's no where near accurate.

Chances are your crossover is probably wired ok. Depending on what your friend is used to or how much he knows, they might sound like they're in a closet compared to what he's used to, and that might be something even worse.

Get some proper measurements to confirm problems before you do anything else. It's a good investment to get some proper measurement equipment. You just can't trust your ears to tell you exactly what's going on, especially without any prior experience.