Tweaking Voigt Pipes (need advice)

[michael_w]

As some of you may remember a couple months ago I finished up some mini voigt pipes that sit about three and a half feet tall and use a single three inch full range Audax HT080M0 driver. So far I'm enjoying these speakers with their smooth highs, subtle bass presence and sweet midrange. I would like to do any tweaking (or anything major) before I paint them.

With all the sweet luxuries that come along with a full range speaker I'm still lacking something. These little three inchers lack punch and impact. I have noticed some music sounds amazing on them, while other music just doesn't do it for me. I threw in Michael Bublé's cd and played the song 'Fever' and was just astonished at what these little things could do. Next cd was Dido - No Angel and then then dissapointment set in. It just simply didn't have the midbass that really makes it envolving. The highs were great and they image very very well but overall they just didn't cut it.

Now to the question ~ Am I just asking too much of a three inch speaker or is there some tweak I can do to try and get them to have more impact and become an involving speaker?


Okay feel free to skip this part as it's just more background information that might help.

The enclosures measure out to about 0.2 cubic feet, ported at the bottom and were built to be tuned in the area of around 80 to 90Hz. As I've graphed them in room they roll off ±3dB around 55Hz but have nulls at 180-190Hz and 280-320Hz. Maybe these nulls are hurting more than I had expected. The top half of the speaker is stuffed with a decent amount of polyfill.

I'll try to graph them again tonight to see what's changed in the last while. Maybe I can push them against the wall some more.

FWIW they're running off a NAD integrated amp (c352) and a crap toshibia cd player. I've tried them with and without my sub. The sub helps with the overall presence and soundstage but it doesn't add enough of that impact I'm looking for.

[RuSsMaN]

The only thing you can do with the nulls is try a zobel (if kicking efficiency down a notch is OK). A rear-firing ambient tweeter is always an option for that spatial touch. Add a powered sub (even a cheapie) to get you down to 40Hz, if you don't get presence, you need a different FR driver.

Full range is cool, what it does, it does well. I've owned a TON of FR designs - but none (even Lowther) can touch a proper 2-way. Sins of omission can be a bitch.

Cheers,
Russ

[michael_w]

Would a zobel network affect the midrange enough or does it just focus on the highs and just slightly change the midrange? I suppose it depends on the impedence curve of the audax driver?

I've thought of the idea of using a tweeter in the back and have the materials to do it but once these broke in I had a change of mind and don't think they need it. At the moment the highs are not something I'm worried about too much.

I've got the diy atlas 15 filling in the lows and if it comes down to it and the pipes branch off to their own system I have a cheapo Athena Sub 8 lying around not doing anything. They're decent enough without a sub, but I hate hearing a well known song and noticing low notes that simply aren't there anymore.

Thanks for the tips Russ. I'll have to try and look into using a zobel network again and see if it'll tickle my fancy. They're not the most efficient speakers at the moment, but it's not like I'm suffering. Even off a t-amp I can push them to decent levels.

[RuSsMaN]

Sonic T? There is a small 140 pF cap that is shunted across the outputs. Replace it with a Sonicap (slightly larger value I don't recall offhand), makes a TON of difference in that amp.

Bottom line, you have a properly tuned enclosure, and the electronics buttoned up - it simply may or may not be the driver for your application.

Cheers,
Russ

[unc2701]

I second everything Russman has to say. 3" driver, not much you can do about that. I'd spend a little more time trying to nail down the sub integration- you're not just going to get the 40-80 hz octave without one. One thing you can try before you finish the pipes- I think it was Brines or the quarterwave.com guy found that TL's that go to a point (ie voight pipes) are not an ideal configuration. Try cutting a block to fit in the top of your pipe so that the minimal depth is like 1"- just get it up there good enough that it doesn't rattle and see what it does for your response. I'll look for that page...

[michael_w]

Alright thanks for all the suggestions. I'll probably just go ahead and paint them sometime in the next little bit. The zobel network can be done afterwards and won't affect the paint ;)

The tops are actually already squared off. From the inside there is about 2" of flat part (2" deep, 4" wide). Sorry for the terrible pictures. The camera hates taking photos indoors.




Little off topic but here are some pics of the half assed stands I made at school. I was bored and threw them together in about 20 minutes. Since the it is 19½" to the center of the drivers I figured it'd be better to have them angled back slightly to aim them at ear level. I lucked out and found the perfect angle. Now I don't have to sit on the floor to listen to them!



I'll have to look into adding new caps to the sonic impact t-amp if it really does make that much of a difference ;)

Thanks again for the tips!

[steveinaz]

Cool speaks Mike. Single full-range drivers have always drawn my interest.

[roystr]

im a huge fan of full rangers,mostly because i cant read a schamatic :-)

i can say im more than happy with my FR's.

they simply can not do everything. that said,you say your mids are weak. on mine,the mids are the best part,the tweets are a bit weak as is the lowest bass. nature of the beast. i can say,,id build another pair in a second. but they arent for hard,loud rock. least mine arent. but for classical and acoustic music,,they are some of the best ive ever heard. the clarity/accuracy(to me) is just rite.
blend the sub in and maybe ad the tweet in the rear as mentioned.
good luck,
roy

[mhardy6647]

They sound awfully small; about half of a typical TQWT (e.g, Abbeys)... are they folded?

Have you fiddled with the stuffing?

You might want to try a BSC (baffle step correction) network, but I don't use one with my TQWT's. You might like it, if you're not using fleapower amplification.

[unc2701]

They sound awfully small; about half of a typical TQWT (e.g, Abbeys)... are they folded?

Abby's use a Fostex driver with a Fs around 50hz- these are more like 80hz (IIRC), so the quarterwave is a bit shorter.

[michael_w]

I can't quite remember where I got the forumula but I used this:
(1100/fs)/4

The fs of the driver is 90Hz so it worked out to be 3.056 feet tall so they should be about the right size. If I hadn't used a 3" driver I doubt I'd even have room to put them because they'd be so tall.

I started off with using the little audax's mostly because I was looking for a cheap way to get into the diy side of audio. The drivers were given to me so all I've had to fork out for this project so far is about $15.

I'll have to check out the baffle step correction and see if it's what I'm looking for. I also haven't really played with stuffing too much. Now that I look back on these, I belive I was supposed to mount the driver a little higher. I read it should be about a third the way down from the top? It's a little more centered than that, but I guess with mine being so short it's only a matter of about two or three inches.

The midrange is great but the upper bass lacks some. That's where most of the impact of music comes from and coincidently that's also where the two nulls are in these speakers... I think full range speakers are more suited for those who listen to that certain style of music. Classical, instrumental and maybe soft rock is what they do best. Move to something like Tool and these little things sound pretty crappy (when compared to other speakers).

So far this has been a great way to learn more about building speakers and a perfect opportunity to explore more options in the realm of audio.

Thanks,
Michael

[roystr]

"I also haven't really played with stuffing too much"

from what i remember reading about those loudspeakers,,you kinda have to putz with the fill untill you get it right.

good luck,
~R~