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I made a pair of Voigt pipes and

I was using them with a pair of Fostex Sigma 208s. The sound was fast, but a tad lean. I later found out that the Voigt cabinets themselves, because of their narrow fronts, tend to eliminate some lower frequency extension of any fullrange driver used. This was something I found out while writing back and forth with TWL, another member who has a Voigt pipe with Lowther EX-3 or 4 drivers. He found a way of remediating this.

Before you go to his thread, I think I understand why the speaker and its narrow front baffle eliminated some lower frequency. If you think of the fullrange driver as the beginning of a ripple, in order for it to expand exponentially, you will need a large area. Think the image of a pond. Nevertheless, because the Voigt pipes are narrow, as the sound waves propagate, their ripples tend to become cut off, expecially towards the sides of the cabinet, I think this is what causes the loss of lower frequencies.

Tom Lyons, AKA:TWL, came out with an ingenious solution. He added "wings" to the sides of his cabinets, if the front was 12", he added 12" wings to each side, that are hinged with some piano hinges. They can be in a plane with the front baffle or angled backwards, depending of the effect that was needed. For what it seems to be, his system must sound glorious.

I myself, cannibalized the Voigt pipes and have placed the Fostex in a folded horn cabinet, a Zhorn that Tom Zuworsky made for me...because I wanted some lows. On top of that, I added a powered subwoofer for even a more pronounced lower end.

I am happy with the sound I get now.

The Voigt pipes, with the winged mods should not be hard to make. It took me about a day to get the pieces cut. You need some room to manouver the sides and the front...if you have the space and one helper, I think you can make them for about $450, with ply and drivers included. They do sound dynamic, better than a 3.5 K commercial pair of speakers that I still have around.

PS: With the winged mods, I am sure that the Voigts will sound explosive by themselves.
bemopti123
cdc
1,412 posts
 
Sean, I think you're ready for the big time. I vote to kick out Sam Tellig and have "Sean's Space" instead.
I would think adding wings would make a speaker sound more boxy. Maybe I'm wrong and have a lot of conflicting listening experiences but the Revel F30, with a wide front baffle, sounded very boxy. B&W Nautilus doesn't but maybe that's due to the curved cabinet as much as the narrow front baffle.
But then again Audio Physic Virgo's are so hung up on a narrow front baffle they are willing to put the woofers on the side which seems like a very BAD idea to me. Maybe it's for looks more than sound?
DynAudio Contour (?) 2-way monitors sounded incredibly boxy IMO. OTOH I had Ascend Acoustics CBM-170 which has a wide front baffle and I just could not hear any (or any significant) difference between them and my "tweeter on top" Nautilus 804. But then again, the Nautilus is nice because the tweeter on top makes a smaller cabinet which looks nicer and resonates less.
The most interesting demonstration of reducing boxiness was at the Paradigm dealer. He went up the line from Atoms to Titus (?) etc and each notch up the sound became more open and spacious. Despite the Atoms being the smallest speaker of the bunch.
Then again B&W claims the "drivers hung in space" design is the ultimate design. What Hi-Fi? said the floorstanding B&W CDM-7 came closest to the sound of their CDM-1 standmount than any other mfg'r floorstander vs. standmount. They said they added range way more than compensated for the slight resonance from the larger cabinet and that it was very rare for a floorstanding speaker to be able to do this. Something to do with cabinet design they said.
A local dealer actually had a speaker guy from CA stop by with his 3 way consisting of drivers mounted in those white plastic tubes you can get from Home Depot. The tubes were located but some type of wire framework. I guess they sounded really good. But $5,000 for 3 drivers and some plastic tubing? Whoa, I don't think so.
So if you want to approach a confusing issue, at least to me, what makes a speaker sound boxy? I don't think the baffle width or cabinet size has the effect that some mfg'rs like Audio Physic would lead us to believe.
gregm
3,021 posts
 
Cdc sez:
what makes a speaker sound boxy
Usually a resonant peak @ 250-300Hz. The wood resonates giving a "honky" hue to the sound.

Virgo- I respectfully disagree that putting the woof on the side is that bad an idea. What Joacheim is doing is keeping the front baffle narrow (to help imaging) and, for low frequencies that CANNOT be easily located by our ears (i.e. there's no imaging), he uses the side baffle that is WIDER, placing the woof close to the floor (i.e. reducing baffle-step loss AND hoping for some floor boost).

Whether we like the result, is another matter:), but it makes sense!
Cheers
cdc
1,412 posts
 
Sure, if the Virgo's woofers cross over at about 30hz. But I doubt they do. Stereophile said in their 1995 Virgo review:
"So it's probable that the peakiness between 200hz and 300hz is due to some kind of internal standing wave phenonmenon."
Maybe your theory is true but the Virgo's did not sound boxy to me.
I would like to compare Virgo side by side with Nautilus 802 and hear if their is any difference between side vs. front mount. I like both speakers but side by side comparison would be best way to detect differences.
sean
6,229 posts
 
Side mounting a woofer should be done ONLY if the crossover point is quite low and the crossover slope is relatively steep. If such an approach is taken, bass distortion becomes less apparent and the benefits of a narrower baffle can be taken advantage of. Having said that, higher crossover points with shallower slopes will introduce more problems than they will solve with a design like this.

As a side note, i've seen quite a few designs using side-firing woofers that are mounted quite high in the cabinet. This in itself creates multiple problems and should be avoided. One of the biggest and most noticeable problems with such a design has to do with speaker placement & obtaining smooth frequency response / even tonal balance. Placement becomes much easier with such a design as the woofer is kept closer to the floor. Then again, if the woofer isn't really just a woofer and is being used to reproduce the lower midrange or above, mounting the woofer closer to the floor will introduce further problems. Such a design is a major compromise and should be avoided.

There are MANY factors to look at when designing a speaker. Those interested in building / buying speakers that actually work with room acoustics rather than fight them should do some reading about the Allison Effect ( named after Roy Allison ). The research that Roy and several others did back in the late 60's / early 70's is very interesting and worthwhile reading. Sean
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