Latest speaker project

[jcaut]

Here are a few pictures of some more speakers I'm finishing up. As much as I'd like to take credit for the design, it's not mine. This is a design by LouC, http://www.lonesaguaro.com/speakers/, that he calls the Azurite, and I followed his design pretty closely. The write-up is on his site, under "Archives". The drivers are PE buyout Vifa BC11 JBL woofers, 12 Ohm, combined with a 3/4" Audax neo tweeter. The two 12 Ohm drivers in parallel result in a fairly receiver-friendly impedance, and pretty decent sensitivity.

What I CAN take credit for is the nice enclosure. I must say that these are going to end up looking nicer than any speakers I've built so far. The pictures really don't do them justice. (Actually I'm noticing that the pictures really make those exposed screws that are (until I glue them) holding the front baffles on really stand out. They don't look bad in person and I was planning on leaving them like that. I may end up changing it.) Maybe I am getting better at this after all! They're covered in walnut veneer, with a very light cherry stain and three coats of wipe-on poly. Seeing how the big terminal cup and port were going to require cutting out a substantial hole, I just used black vinyl for the backs. I think it ended up looking real nice.

I haven't had the pair playing together yet, but listening to one speaker, I'm really impressed. For the money in parts (<$50 per speaker), I think they're going to be VERY nice. I wish I had bought more of those woofers while they were available. The crossover is a relatively simple one, and Lou did a good job on it.

I'll report more on the sound when I can listen to them both at the same time.

[gatemplin]

Looks great Jason. I've heard really good things about the Audax tweeters. I agree that those look like they will be VERY good for the price.

[VR3]

those look absolutely awesome! The dark finish is great!

[VR3]

What type of truck liner did you use? brand? spray or roll? thanks

[jcaut]

Thanks!

The baffle finish is Duplicolor bed liner, from a spray can. I always shoot them with semi-flat black Krylon first, so that it only takes a light coating of the truck bed liner to acheive coverage. I usually apply two light coats, waiting about five minutes in between. Another thing I've discovered is that it's best to do both of them side-by-side, at the same time. Otherwise they don't always come out looking the same. The truck bed liner has quite a different look to it, depending on how heavy it's applied.

Jason

[anonymouse]

Very nice work.

[RuSsMaN]

Looking good Jason. Still interested in buying one of your creations, just say the word.

I wish you lived closer, I've got more drivers than I will EVER do anything with. Do I have to host another gathering, to get you down here to pick them up?

Cheers,
Russ

[dorokusai]

Excellent.

[Mazeroth]

I used almost the same drivers in my line arrays, but mine were the 6 ohm Vifa JBL buyouts. They're acutally the Logic brand that Vifa makes. VERY good performance for the price.

Nice work on the cabinets as well. Keep up the good work!

[heiney9]

Man those look sch...weet. I wish I could do some wood working. I've always wanted to build my own pair of speaks. I just don't have the patience it would take to create something like that.

Nice job

H9

[jcaut]

Thanks for all the compliments!

I put the other one together and they do indeed sound very good. The midrange is really sweet and the little Audax tweeter sounds better than I would have imagined that it could-- I've not had much luck using those little neo-motor tweeters in designs of my own, but it sounds great here. Bass is respectable for a pair of 4" drivers, though it's not particularly deep (F3 is predicted to be about 62Hz). It can sound a little one-notey: I'm still adjusting the amount of damping material in the cabs and that may ultimately be the key to that issue.

Russ-

If I can ever come up with something of my own design that I'm convinced sounds respectable... I owe you one anyway. If it was just a little closer, I'd be down there. It's hard enough for me to just get out of town these days.
_____
May have a little problem with these: You know I mentioned "receiver-friendly" above. Well, as I always do after I get a speaker 'about' finished, I hooked it up to my impedance jig, just to double check that I don't have anything wired incorrectly in the crossover. I wasn't too concerned with the impedance, since this was someone else's design. But once I ran it, I was a little surprised to see it dip to 2.9 Ohms at around 5Khz. The impedance phase is kinda screwy, too. That's certainly a little lower than I would have liked to see, and may NOT be receiver-friendly. I've been driving them with a 4.0t Carver during my preliminary listening and it's probably not an issue for that amp. I'm going to investigate a little further.. There's a shunt cap across the tweeter to tame an upper end rise in the response. That may need to be altered.

[jcaut]

I set my stuff up and took some quick-n-dirty measurements of these things. Although I'm not sure my accuracy is real good, they measure pretty flat. That rise on the upper end shows up to some extent in all my measurements, so I think it has something to do with my mic calibration.

I made some changes to the crossover and measured the response and impedance again. The one dip around 5K is one thing, but what was really bothering me is that roll off in impedance at the high end. Especially with the impedance phase at -75 degrees that could be tough on an amp, as it is a highly capacitive low impedance load. The crossover has a 4.7uF cap shunted across the tweeter that's supposed to help tame the rising response of the tweeter. To me, though, the cap seems like a bad idea because as the frequency goes up, that cap's impedance approaches zero, and it acts like a short. Removing it completely mucked up the response, so I tried just putting a resistor in series with it. That provides a little safety margin.

The red line in the picture is the predicted response, after my modification. The blue line is the actual response I measured, before I changed anything. The new impedance curve is below. I can't really tell that it altered the sound.

Jason

[VR3]

Looks very good...

Didnt you buy some 6.5" midbasses a while back? What are u going to do with them?

[jcaut]

You mean the DT ones I asked you about? I ended up not getting them: The guy was trying to double his money on shipping, so I passed. That, and I've got more drivers than I'll ever get around to using already. I would have liked to have them, but it was going to end up being more than twice what I know he paid for them, and it just kinda rubbed me the wrong way.