[Oktyabr]

Hi!

I'm hoping matevana might reply to this one, but if anyone else feels they can contribute I'd be happy to hear your suggestions!

I've read probably every single post having to do with any of the Hestia builds.  They look quite intriguing to say the least.  Personally I'm most fond of open baffle on a budget and I've considered building the original Hestias (or a variant) to sit on top of my existing GW 18" H-frames...  For the last few years I've been quite happy with a simple H-Frame and a full range driver on top, per MJK's recipe, but recent experimentation has made me wonder about multiple drivers on top instead and perhaps it's time to add passive (hopefully inexpensive) crossovers to my experimentation as well, just for something new.  But enough about me...

Why I'm really posting is because close friends have heard my DIY system numerous times and commented with great acclaim.  I feel as if there is hope that I may one day start a small circle of local DIY'ers with the simplicity of basic OB construction being particularly inviting to the otherwise un-initiated.  THEN they see the mass of wires, multiple amps, I answer a couple of questions concerning active crossovers (miniDSP in particular) and I notice most slowly withdraw their enthusiasm.  So then, what I need is a great sounding OB that can be powered with a single amp and no extra EQ or DSP involved, for the sake of simplicity.  It should reach all ten octaves fairly smoothly, without the addition of a dedicated, separately powered subwoofer.  Most importantly it should be relatively cheap to build from readily available parts.  I know, I know, this is a lofty goal that may be difficult to reach.  But it made me wonder...  MJK published work on a H-Frame variant with passive XO...  how much more difficult could it be to get a similar system built using multiple drivers on top, ala the original Hestia and kin?

matevana, surely you have explored this possibility?  Is there the potential for an H-frame enhanced (or otherwise 10 octave capable) version that can be fed with a single two channel amp?  Or does the point of purchasing the extra crossover components make a powered plate amp the better solution, all else being equal?  I've been particularly intrigued by how you seem to simplify your designs, through driver selection, etc. to reduce the crossover component count to a simple minimum?  I like this design philosophy. 

[matevana]

It's certainly possible to design a three (or more) way system using nothing but passive components. MJK documented this back in 2007 in his paper 'Designing a passive 2-way open baffle speaker system'. You can extrapolate from this his basic tenets of (1) selecting a bass driver that is much more sensitive than the others with high-ish total Q, (2) viewing the drivers, baffle and crossover as a single system, and (3) selecting an appropriate low pass model, and then applying all this to a more complex 3 way design. Doing this however, may limit your driver selection possibilities and make it more difficult to wind up with a homogeneous collection of drivers.

For this reason I have found it easier to concentrate on building an upper section with two or three drivers of comparable sensitivity and a separate lower section powered by a plate (or other) amp. This approach will also allow you to consider more plentiful woofer options, with mid to low Qts and higher excursion. The downside, as you mention, is the need for bi-amplification. Don’t think of this as making the system more complicated necessarily, as by doing so you will have eliminated a level of complexity in the passive crossover design.

I am a big fan of passive crossover components in the critical mid range and upper frequencies, where other types of crossovers may have a detrimental effect (to my ears). This is somewhat less evident at lower frequencies so DSP or active analog crossovers tend to do well here. Plate amplifiers typically make use of the latter, although a new crop of plate amps made by Hypex, Dayton and others now employ DSP as well.

If you decide to move forward with a design, I would be glad to assist with driver and crossover suggestions.

[Oktyabr]

Thanks for the reply!

I understand the reasons for active XO/DSP and multiple amps but my friends turn away from it.  Passive XO is more familiar, less intimidating for them, I think.  The reason I asked is because if anyone can find a reasonable combination of components (including drivers) for such a version, that will work well with each other, I would think that would be you matevana.  You seem quite meticulous in the selection and matching. 

My current system is built upon MJK's work on OB speakers.  A few years ago I considered building the passive version of his 2-way, H-frame system but frankly the passive XO components were more expensive than a mini-DSP and I already had multiple amps on hand.  Further, as I use a full range driver that literally had no documentation in OB use, experiments in active were likely needed to even reach an ideal passive solution, and I've just remained active since.

In a nutshell, I guess what I would like to know is have you explored the potential for a fully passive Hestia variant?  If so what bottom drivers and XO look like good candidates to you?  I've thought about building just the passive end of a Hestia and combining it with a single, conventional powered sub as a possible offering to those I know are skittish around the idea of a more complex, active system, at least as way to help them get their feet wet, but thought perhaps you might have a full passive system in mind you could recommend?

[matevana]

A new woofer on the market made by Morel and designed for and sold by Pure Audio Project seems like it might be a candidate for an all passive OB system. The Morel model number is PAP1075 and the specs can be found here: https://drive.google.com/file/d/0B36Kyv2xZFCtYWhmVjA0a0M4Z1U/view?pli=1  A Qts of 1.14 in a high quality woofer that Morel is known for should be ideal in a system with little or no additional EQ.

Pure Audio Project sells these drivers separately for the DIY crowd. I also like their modern update to the Eminence Alphas, if you are considering a larger woofer. Personally I prefer the faster action of the smaller/lighter 10" woofer.

Ed

[JohnR]

I guess I (were I the OP) would start with building MJK's passive design and seeing how that worked out.

The other option would be to tell your friends to just accept that multiple amps and a few extra cables are just part of the deal if they want the same thing in their own place - ??

[bentconvert]

Here is a passive OB design from the diy audio site http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project.html

I think there are a couple designs there if you go through all 133 pages

[Oktyabr]

Here is a passive OB design from the diy audio site http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project.html

I think there are a couple designs there if you go through all 133 pages

Thanks bentconvert!  I forgot all about the Manzanitas!  I've actually read that thread a few times (all of it); it's just been a few years.  That might be a doable "entry" project.  Cheap, quick to build, simple XO, should be OK with the typical AV receiver...