[Nils Luehrmann]

Colin wrote:

Quote:

My movie screen is FINALLY finished and up on the wall!!!

CONGRATS!!! (and the seating looks very comfortable, can't wait for the demo!)

[Jeff Meininger]

My next DIY project has begun. I'm rolling my own MTM tower speakers. After changing my mind on drivers at least ten thousand times, I ordered some PE buyout Vifa drivers (PSB OEM I think). I placed the order shortly after deciding against MTMs as a first project. Heh.

Haven't picked the tweeter yet. I'll probably use the Vifa PL tweeter.

Anyway, I'll keep y'all posted.

[Jeff Meininger]

The big brown toy truck just dropped 'em off.

Here's a picture of all ten: Vifa TC18WG-35-09 woofers

I had so many choices... I was all set on doing a 1-woofer 2-way with the Peerless HDS that Mark Hayenga uses. I really liked the sound when I heard his, and I also liked the cut-side frame. I wanted to spend less money and have more efficiency, though. The pickins are slim when it comes to cut-side woofers, but I think these should work out well and be a great value.

They are apparently the woofers used in the PSB Stratus Bronze tower speakers. I'll be doing a 2-way MTM, though, rather than 2.5-way.

[Hank Frankenberg]

Jeff, I assume you know how much effort is required to design a speaker system, the heart of which is the crossover. Are you getting some expert help? No offense intended, just want to make sure you have a good experience with the results. Are you going to build five towers?

[Jonathan DA]

I haven't worked with the -35 version of those drivers, but I have experimented with the -49 version. Assuming the 35's use the same motor, then you'll probably be using a sealed box alignment. Watch the power handling in the low end, they tend exceed xmax fairly quickly. As long as you're crossing over to a sub with at least a 2nd order highpass on the sats around 80Hz you'll be able to crank it as loud as you want. The TC woofers are a high quality woofer for the price, I'm sure you'll like the smooth sound they can produce.

What is meant by a "2.5-way" design? Would that be two identical woofers covering different frequency ranges?

[Jeff Meininger]

Hank: I'm definitely aware of the steep learning curve and amount of effort required. Since the sub project, I've learned a lot already by reading huge amounts of material online. I certainly have much more to learn, and that's really why I want to design my own rather than build a kit I want to do the hard design work myself. More than that, I want to KNOW how to do it, and be able to do it again. The engineering process behind it interests me as much as actually ending up with some great speakers.

As for expert help, I have you guys. Mark has offered to help me get measurements once I'm ready. After that, I'll take the response files, plug them into LspCAD, and start modeling crossovers. Once I actually put a crossover together, I'll bring 'em to a meet and have you guys critique them. I won't mind being sent back to the drawing board.

I was planning to build 5 towers, but I think I'm actually going to build 3 MTMs for the front (with the center tower standing up like the left and right) and some 2-ways for the surrounds. I got to thinking, and I realized that MTM surrounds elevated ~3 feet above the audience might be a bad idea due to the narrow vertical dispersion pattern. I'll probably shoot for 2-ways with a slightly down-pointing phase lobe. This will leave me with enough leftover woofers to go 7.1 someday. Or 6.1 with a floorstanding MTM rear center.

[Jeff Meininger]

Jonathan: these have an EBP of 61.5, so I guess they're in the "can go either way" category, leaning towards sealed. I haven't decided on sealed vs. vented yet. I don't have LspCAD yet, and I've just been messing around with WinISD to look at response curves. LspCAD provides much more useful info with the excursion graph.

The EBP and the PE site ("a great sealed-box woofer") indicate good sealed performance, and the woofer's intended application (PSB Stratus Bronze) indicates good vented performance. If I go vented, I'll make sure it's a very well damped alignment. I might try both... I'm in no rush to have a finished set of speakers.

Mark says you've worked with the D27 tweeter and you didn't think it was that great. I'm considering going with the PL27TG-35 tweeter; I've read reports that it is smoother than the D27. Have you ever used/heard it?

EDIT: Yes, they will be crossed over at 80Hz to an EBS Shiva with my Onkyo SR500, which SURELY uses a second order or higher slope. Right?

[Jeff Meininger]

Colin: A 2.5 way is a normal 2-way with the addition of a second woofer to handle the baffle-step compensation. In other words, one woofer's response runs all the way up to cross over with the tweeter, and the other woofer only goes up to around 500Hz (or whatever is required due to the woofers response and baffle width).

Baffle-step compensation is required since lower frequency wavelengths "wrap around" the baffle. In other words, the woofers energy is spent radiating into 360 degrees rather than 180, speaking 2-dimensionally.

I'm not quite sure how this would apply to dipoles like your Maggies. You'd get more bass response pushing a monopole speaker against a wall since the wall would act kinda like a baffle, but pushing your maggies against the wall would cause the backwave to cancel out the bass.

[Jonathan DA]

Yeah, I wasn't overly impressed with the D27's, they always sounded a little harsh and sibilant no matter what I tried. The sibilance could have been a diffraction issue, but I think the harshness was inherent to the tweeter. I preferred the sound of the D25AG. Contrary to stereotype I actually find the D25's aluminum dome to sound smoother than the soft dome of the D27. I haven't tried the PL27. If you're interested in giving the D27's a shot I have some I'd let go cheap, maybe you'll have better luck with them than I did.

In general I prefer Morel tweeters over Vifas. You might want to give the MDT-20 a shot. I don't have any personal experience with it, but based on past experience with Morel I'll wager it will sound better than an equivalently priced Vifa. Pure speculation however.

[Hank Frankenberg]

Pssst...Jeff buddy...wanna buy some cone dope?

[Jeff Meininger]

Hank: I would, but I spent all my money on LsdCAD.