The Igloo Project...curved Open Baffle For Visatons - diyAudio
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Old 10th September 2006, 08:15 PM   #1
foniton is offline foniton  Spain
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Join Date: Mar 2004
Location: spain
Default The Igloo Project...curved Open Baffle For Visatons

Hi everybody.

This is my fourth ob project (after BEYMA 8 AGN, CIARE CH250 and SUPRAVOX 215 sig bic). Because space restrictions I sold the supravoxes some time ago.

I´ve seen the NoBox project on Visaton´s web and I like the concept but not the complex crossover.

This project was reviewed by Dick Olsher on Enjoy the Music with good overall impressions but complaints about treble quality and grainy textures. Could anyone experienced with Visaton drivers comment about this?
Any comments or suggestions about the IGLOO project (or Visaton drivers on ob)?

Any information would be very much appreciated.
Sorry for my poor english.
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Old 10th September 2006, 09:11 PM   #2
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Nothing wrong with your English; it's a heck of a lot better than my Spanish (or any other language come to that) What a great looking project! I hope it's going to be painted white?

Dunno about the grainy texture bit -a thousand Dark Star owners the world over would probably choose to disagree (although they don't use the XO or additional bass driver as they've found they don't need it). I gather the treble improves by a frightening magnitude with Dave (Planet10)'s phase-plugs. Mr Dark Star Dan Mason frequents the forum so I'm sure he'll be able to contribue a few words of wisdom & experience to the debate re the B200 on OB. If there are problems with the NoBox, I'd look to the XO and the optional impedence linearising (what a name!) network which strikes me as being somewhat over complicated for a passive setup -I'd go for digital XO and correction over passive if you want to use to additional bass driver.

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Old 11th September 2006, 04:32 PM   #3
foniton is offline foniton  Spain
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Join Date: Mar 2004
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Many thanks, Scott, for your comments.
Of course, the Igloo It´s going to be painted white.

My intention with this curved ob project is to preserve real dipole radiation as much as possible with a relatively not too large panel (just in the limit of excessive diffraction) and enough bass extension. I have tried more reasonable sized -60x120 cms- rectangular panels in the past (at the time I owned the Supravox 215 sig bic) with mixed and, in the long term, disappointing results: excellent detail and imagining but a very thin presentation without enough foundation for anything different to very light-bass acoustic music.

Believe me, I´m not a bass freak. Whit the exception of Spendor BCIII’s (with twelve inch bass drivers), I never owned speakers with real bass drivers (Rogers Ls3/5a, ATC scm-10 actives and passives, etc). I mainly listen jazz and chamber music but I also love other musical genres like 60´s soul, 60´s garage-rock, 70´s funk, rock steady...
So, I need bass to get the full picture. And, at this point, you sadly have to deal with...Horror! “Required size versus frecuency” chart!

Although this chart is merely indicative, because don´t say nothing about floor and walls reflections influence, I must admit It´s basically right... You need a really big panel to get dipole bass.

I have tried big panels (240w x120h) with the Supravoxes, resulting in a bidimensional “wall of sound”. You easily get too much “one note” bass. Not oppressive bass, just omnipresent bass... and omnipresent mids... and omnipresent “everything”. Try to imagine female voices the size of a good proportioned wardrobe.
Maybe it´s a problem of excessive diffraction or any other reason, I don´t know.
Comments, experiences or explanations of this matter are welcome!

So, there must be something in between.

One of the proposed routes to solve the “too-big-panel” problem have been mixing dipole panels (for mid and highs) with closed or vented boxes (for bass).
I didn´t try myself but I didn´t have good experiences with hybrid equipment in the past (like electroestatic panels with electrodynamic woofers). May be It´s very difficult to integrate so different radiation patterns.
Dick Olsher´s “basszilla” is a good example of the hybrid route.
Any comments or experiences about this project are welcome!

Dick Olsher´s NoBox review (describing Visaton´s possibles treble faults)...

I´ve seen on different forums people using Visaton B200´s on open-baffle or semi-dipole variations without any bass augmenter. May be the IGLOO can work this way. I´m anxious to know...

P.D: Scott: Planet 10´s phase plugs are on my shooping list, but I´m a bit reticent about digital EQ. I also think the problem with treble quality and grainy textures (as described by Olsher´s review) could be mainly due to the complex crossover.

Best Regards.
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Old 11th September 2006, 04:58 PM   #4
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Excellent. White curved OBs, hopefully with the lines of the ice-bricks drawn on...

Basszilla is an odd one. Lots of people love it. I'm not 100% convinced, though I imagine it's far better than a lot of speakers, and many owners swear by it. It's a pretty good compromise, but I'd tred carefully until I found out where the crossover point is.

For me, the kill zone of dipole is actually in the LF (ironic because that's the place it's hardest to get!) stretching to the midrange because it dramatically reduces the influence of the room on the sound (huge reduction in energy expended on activating room-modes -see Linkwitz for more). I never did see the point of these dipole designs intended to take advantage of floor or rear wall reflections, as you're throwing away a lot of the benefits of going OB in the first place. It's only in the sub-bass (which I class as being below 40Hz) that monople begins to reassert it's authority IMO.

Digital EQ or active crossovers do have some major benefits -they're far better than the old type, and allow you to boost the LF up without damaging the rest of the range. Ever heard of a Linkwitz Orion or BD Design Quasar owner unhappy with the sound quality? So much smaller baffles can be used, with deeper bass, of better quality. They don't do anything to the rest of the range remember. Far better this than trying to do it with passive components with all their thermal issues, and their crippling of the sensitivity. I'm certain this is why the Visation got some dodgy comments about midrange & treble quality -I don't really buy into the 'passive components have a sound' idea, but I do believe that improperly applied, they can cause problems.

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Old 12th September 2006, 07:56 PM   #5
foniton is offline foniton  Spain
diyAudio Member
Join Date: Mar 2004
Location: spain
Hi everybody.

Thanks for your comments, Scott.
It´s a pity you have to buy the BassZilla kit plans to get full information (like crossover point, etc). Anyway, it´s for sure these are very respectable loudspeakers.
What isn´t clear for me is Olsher´s argumentation about the useful range of dipole radiation. It sounds like he is trying to justify the facts “a posteriori”.
If you read the NoBox review
about the “monopole-vs-dipole-bass” topic, it´s easy to get no conclusion at all, unless you consider conclusive the following words: “ thing is certain: a dipole woofer is bound to sound different relative to that of a box speaker”.
How much different? Is the key thing here.

“Using a full-range driver as a dipole radiator on an open baffle allows the backside of the driver to add 3 dB of additional midrange energy to the speaker's off-axis response and results in a better midrange balance at the listening seat”
“ OB design, in my book, is first and foremost about the midrange”.

Nothing to complain, Mr. Olsher, but I don´t think this is the main reason to mix monopole and dipole concepts in the same design. Dipole bass means big size, much more than monopole bass, and I understand it´s not practical for everyone, but I don´t see the necesity of confuse things with technical arguments. Things could be much clear if you explain what´s wrong with dipole bass.
But, what is a total mistery to me is how a proponent of mixing open baffles with closed or vented boxes can say... “The OB made its first appearance in the radio receivers of the 1920s, mainly for reasons of convenience and cost. The baffle was typically folded back to form a five-sided box with an open back. Unfortunately, this represents the worst possible OB design, as its primary advantage — lack of cavity resonances - is negated”.
Comments about this matter are welcome.

I find much more serious the Linkwitz approach. He doesn´t try to sweeten practical arguments with technical issues. He just propose practical designs with good technical background. I don´t like the complexity of the whole thing but I must say it´s an excellent proposition of a reasonable sized open baffle speaker.

About the Quasar design, I must confess it´s aesthetically very attractive but for me the old Quasar MKI is more convincing and deserve more attention. The more complex approach (crossover, multiple amps, equalization, etc) of the new Quasar makes it a very different animal...too oriented to sell multiple expensive parts.

Best Regards.
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