finished construction of mini voigt pipes

michael_w

They're not beautiful but they're done. All they need now is a finish. I started these out at school and then finished them at home in the last couple days.

They use a 3" Audax HT080M0, which I had received as a gift at the last northwest audio meet. The cabinets are made from 3/4" mdf and are about 0.2 cubic feet with a single port at the bottom. According to the graphs from winISD and Unibox they are ±3dB down to about 89hz. I did the internal wiring with 12awg twisted home depot special at just under 30 cents a foot (the same stuff I use as regular speaker wire for my LSi7's). I cheaped out on the binding posts and used some crap radio shack ones because I didn't want to have to order anything right now and had them lying around but eventually I'll order something better for them. Also, the top half of the cabinet is stuffed with polyfill.

What do they sound like you might ask? Well for a 3" driver I was expecting them to lack bass and be a little on the excessive treble side but I was wrong. In fact they're pretty much the opposite of that. They dig deep enough to listen to without a sub (very unexpected) but lack a little oomph on the vocals. Since it is only a three inch driver doing all the work the vocals seem to blend in too much and don't seperate themselves enough. The drivers can go high enough in certain passages but it isn't as pronounced as desirable. Imaging and vocals can be improved by moving closer to the ground (or sitting on it) since the drivers fall short of ear level by about eight inches.

I first ran these on some Steely Dan and they seemed to like that kind of music. After spinning a few discs it became very apparent that they're not big on rock. They just can't handle it and still sound good... they much prefer the softer and slower types of music.

Will these replace my LSi7's or come close to what they're capable of? Of course not, but it was a fun experiment to try a new and unusual design with such a small driver. Right now they're running off my NAD C352 and seem to be very power hungry and inefficient.

Edit: after listening to these for a while I've noticed it sounds almost like they have a blanket in front of them. A sort of muddled midrange and pulled back highs. I'm going to try and fix this by not feeding them a full range signal anymore and moving them over to a receiver where I can cross them over around 100Hz to a sub. I might also try and put them on a concrete paver to see how it changes things.

ohskigod

are you sure that audax driver is truly full range? might be the reason for the highs problem.

cool looking project dude either way

michael_w

Yeah they're full range but could probably sound better with a tweeter.

Specs on the driver:
Power handling 20 watts RMS, 30 watts max
Voice coil diamer 1"
Voice coil inductance: 21 mH
Impedance: 8 ohms
DC resistance: 5.9 ohms
Frequency response: 80 - 18,000 Hz
Magnet weight: 4 oz.
Fs: 80 Hz
SPL: 86 dB 1W/1m
VAS: 067 cu ft.
QMS: 2.48
QES: .79
QTS: .60
XMAX: 1.5mm
Net wt: .75lb

I'm thinking they should clean up a lot once I cross them over at around 100 or possibly even 150 hz.

Thanks!

ohskigod

give it a shot, what could it hurt.

unc2701

You might want to angle them up a bit so they're pointed right at your ears (less off-axis) and maybe add a zobel network to take care of that rising impedance.

Take a look at the response- these aren't very flat, so you're gonna have a hard time getting an even response- especially with the rolloff starting around 1.5k.

Crossing them over will defeat the point of the voight pipe...

RuSsMaN

Yeah, a Zobel will smooth it out a bit.

A friend of mine that built some full size Voights added a rear firing supertweeter padded down 10db and passed around 12K - helped with the spaciousness of the top end, and increased efficiency while still maintaining the 'full range' (crossoverless) aspect of the main driver.

steveinaz

Cool project.

michael_w

Thanks for the tips. I will have to read a bit and possibly add matching / zobel network.

I'm in the process of playing with them on a low end panasonic receiver (sa-he75) and have noticed that crossing them over only seems to help with certain bass heavy music. It degrades the majority of normal music since they can handle it but when I put them against something like Gorillaz it becomes overwhelming for them and only then does crossing them over help any.

I'll see if I can get my laptop up and running, then post a frequency sweep to see how bad the response actually is

BTW I've been listening to these sitting on the floor (which I usually do when I'm working on my computer) so my ears are pretty much perfectly level with the drivers.

michael_w

Just did some tests with RoomEQ Wizard. The graph kind of speaks for itself... very very choppy. Just above 300hz to 400hz is a big dip and the rest of it looks pretty bad. I manually went through the frequencies and I could actually hear when they would just drop out... it would just go quiet(er). I'm impressed they made it into the 50's before rolling off quickly but overall a little dissapointed. Looks like I have some work to do!

unc2701

Did you have both speakers playing when you did the freq sweep? If so, do it again w/ just one speaker... Also, do a sweep off the port- put a "couch cushion fort" around the port so the mic only picks up what it's putting out. You might need more stuffing.

michael_w

That makes a bit more sense. I'll try it again later tonight with only one. Should I still measure from the listening position or just 1m?

unc2701

1m for the higher frequency stuff you're concerned with. I'm thinking all that jaggedness could be a comb filtering effect from having both speakers playing exactly the same signal. For the bottom end, you should back it off to the listening position so you get the effect of the port and any room gain.

If you can't get your drivers to smooth out, you should look into the Fostex FE103's... You'll have to make the mounting hole bigger, but their quarterwave Fs should be close enough to use your enclosures... I think they're like $25-$30 each from Madisound. People have had a lot of success w/ those.

michael_w

So I measured just a single one and it looks a hell of a lot better. The graph is much smoother (albeit still pretty unstable). It's got a two dips, one below 200 hz and one surround 300hz, that I need to do something about but other than that they're starting to turn out okay. After a couple hours of break in time they seem to be emerging from a muddy hole. The vocals have finally started to show up and the curtain has been lifted from them. The graph was produced with an spl meter on a tripod at roughly a meter (didn't bother measuring or anything).

I also got a pair of tweeters from the audio meet today and might add them to the back, but I'll be leaving that until they break in more.

RuSsMaN

Atta boy.

Let me know where / how I can place an order. When you're ready that is.

michael_w

Wow my first Russman 'Atta boy'. :cool:

There's something to be said for a crossoverless design. You really do gain a whole lot even though you have to fiddle and accept some drawbacks. I got the chance to hear other full range designs on tubes (some crazy sapphire monoblocks that retail for something like 7k us?) and I was blown away what they could do.

Today was also the first time I've ever heard a tube amp. One was a diy three watt one and the other was that sapphire one. The big rig we were listening to random speakers on was amazing. It could take any speaker we threw at it and produce insane results. I gained a whole lot of appreciation for having good electronics behind your speakers. It makes me rethink the whole order of priority in a system.

The three watt amp sounded nice but having so little headroom had me craving just a tad more. It would hit it's limits just slightly before the music got loud enough to become truely involving and dynamic. Maybe with a smaller room and more efficient speakers it would be better suited.

I'm listening the the new speaks right now on a sonic impact t-amp and my pocket pc as a source (because I just finished breaking my friggin cdp) and they are amazing me more and more. I can't belive the bass and imaging I'm getting out of a three inch driver...

I have a little tweaking to do, but for now I'm happy. The LSi7's will be unhooked for a while at this rate

unc2701

Yep that looks a lot better. Keep us updated.