[Jeff Meininger]

Here's the different resistance schemes I tried:

1. Straight L-pad placed last. Caused phase to dip below -60 just above the crossover point. Only way I could get rid of this phase dip is to use 0dB of baffle-step. Confusing... not sure why this happens. L-pads are widely used AFAIK.

2. Straight L-pad placed first. I don't think you're supposed to do this. Resistive load is seen across entire frequency spectrum.

3. Big honkin series resistor placed first. Could be used to attenuate the tweeter, but I found the extra resistors helpful for the following reasons:

A. In the MTM network, I use the second (last) resistor to flatten out the high end of the tweeter response.

B. In the MT network, I used the first series resistor for partial attenuation, and the traditional L-pad at the end for the rest of it. L-pad alone caused phase problems. Initial series resistor alone put the tweeter impedance into the stratosphere, and I'm not sure how high is too high.

Are 10W resistors okay for all of this stuff?

I think my biggest head-scratcher is why I can't really bring down the impedance peak at the crossover point on the MT design. Looking at other people's DIY XO screenshots, I see that their XO hump is rarely twice as tall as their woofer/box peak.

[Hank Frankenberg]

Jeff, I admire your jumping into the xover experimentation area - keep going. I just saw your latest design, and there do seem to be quite a few components. Maybe Scott H or Mark H could give you a tip. Anyway, build the xovers on a piece of pegboard (ala the NorthCreek method), keep them outside your cabs for now and tweak away.

BTW, folks, I was at Jeff's last night and he is definitely hooked on DIY. His garage is as covered with MDF dust and scrap as Jonathan's. Cabinets and parts in the living room like you'd never know he's married. He has a rare, tolerant, understanding wife.

[Jeff Meininger]

If Mark, Scott, Jonathan, or anyone else can give me any pointers as to how I could have worked up a 4th order L-R crossover with similar (or better!) looking results for less money or with fewer components, I'd be thrilled! I was fully expecting to get spanked for newbie / first-timer mistakes, so bring on the punishment. I can take it. I want to learn.

I gotta put the XOs in the cabs because I only have one set of binding posts per speaker. Oh well... the woofers are very easy to remove. I used PE hurricane nuts and machine screws rather than wood screws. One of my hurricane nuts came loose, but that's my fault for drilling the hole off center and then "fixing" it by drilling it into an oval shape. The rest of them seem to be really tight, but I bought some extra "inserts" at Breed and Co, anyway. (Thanks for that tip, Jonathan!)

Darlene is very tolerant and understanding when it comes to the mess. She really wants good speakers as badly as I do. (I don't think she'd be quite as happy with piles of dirty clothes or other non-A/V-improvement related messes, though.) She actually encourages me to do these HT improvements, despite the impact on the living-room livability. You might have noticed that the couch is blocking passage from the kitchen into the living room. We looked at a seating position that would have allowed more traffic, and she preferred the seating position that puts us at the right distance from the screen and in the center. We removed the ceiling fan (and best light source) to install the projector. The projector, by the way, sticks out like a sore thumb hanging down from the vaulted ceiling to near forehead-smacking level. I'll cover the exposed wires on the wall and on the rod with plastic conduit sometime, but for now it looks pretty ugly. The HT layout is really pretty offensive as a living room layout, but she didn't think twice. She'd rather compromise the living room aspect of the living room than compromise the HT. That said, I don't think we'll be painting the walls flat black or installing first-order reflection absorbers anytime soon.

[Jonathan DA]

Dude, you HAVE TO get absorbers!

I was playing with your xo files last night a bit and I got a nice LR 4th order slope on the woofer with only two components. I'm headed out of town for a few days, but I'll play with it some more next week. Maybe we can cook up version 1.1 for you in a week or two. In the meantime, your current xo design isn't all that expensive (relatively speaking of course) so I would have no problems building it. 10W is a little low on the resistors, I'd bump it up to 20 or 30 just to be safe.

[Jeff Meininger]

2 components on the MT or the MTM? My MT crossover design uses just 2 components (L and C) for the woofer for a 4th order LR slope.

I could do that on the MTM as well, but only at the expense of a lousy phase line in the impedance window or other side effects.

Where can I get 20+ watt non-inductive resistors? I can't find any at PE, Zalytron, Madisound, or Speaker City. 12W seems to be the max. Or is it okay to use Sand Cast resistors in the signal path? I keep reading that sand cast resistors are a no-no, but I fall prey to a lot of voodoo because I'm a newbie.

Edit: Bantam Electronics doesn't have non-inductive resistors, either.

[Jonathan DA]

Parallel multiple resistors to up the power handling.

[Mark Hayenga]

The 25w wirewounds at Madisound are fine. Audiophiles will cringe but I've used them a lot. They're not inductive enough to make a noticeable difference in the audio band. Remember the MDT-37 / 6.5 HDS two-ways I had in my bedroom? 25w wirewounds in those.

I should probably bother to measure the actual inductance sometime...

[Jeff Meininger]

First MTM crossover initial impressions: wow. SO much better than our previous speakers in A/B comparison. It's just stupid how much better they are. I'll have a movie night sometime so that those of you more difficult to impress will be able to tell me where I can improve. I haven't listened to very much material yet... just about 30 minutes of random selections.

Vinyl covering impressions: I like it. It was pretty easy to do and the results look better than I expected. No, it's not going to fool anyone into thinking it's real wood veneer. But it's nice for the price. I screwed up trimming a few of the edges so there are a few spots that are a bit wiggly, but you have to be looking for them. I also got greedy with the utility knife and cut a couple gouges into the vinyl (and sometimes MDF), so those are more obvious. I filled them in with black marker, but they're still noticable. I think this stuff would be even better if the grain texture they pressed into it was more random. When you get glare off the side, you can see that the rather small pattern just repeats over and over again.

Soldering is a lot easier when you're doing it correctly. Thanks for the tips, Jonathan.

Here are some pictures from the weekend...

5 naked boxes

Here's another view. (picture)

5 Crossovers - thanks for the pegboard tip, Hank.


An MTM covered in vinyl



I also found a use for some of that MDF in the scrap pile. I (finally) built a box for my sub amp. It will be hidden behind furniture, so that's why the vent holes are still primer white. I mainly just wanted a test subject for the truck bedliner spray so that I'll know how it works when it comes time to do my speaker stands. Sub amp box picture.

[Hank Frankenberg]

Jeff: good-looking, er...vinyl Seriously, youv'e leapt into speaker design with more enthusiasm than I've ever witnessed, and your work is very good. Forge ahead, man.

[Jonathan DA]

That's a good looking speaker Jeff, great job. I can't wait to hear them.

[Nils Luehrmann]

Jeff,
WOW! I have been so busy I haven't had much of a chance to follow this thread, but I must say your efforts are quite remarkable and even encourage me to consider speaker building when I can finally find the time. Very nice work, and I can't wait to hear them when you are finished!