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Discussion Starter · #1 ·
I've been looking around doing some research on some full range open baffle speakers. These will be for music only and I may end up putting them on my pc for listening to lossless audio but even if I don't they will be for light use. No high spl's. I'm wanting to do this more for experimenting more than anything. Single driver, no crossover, open baffle so no enclosure resonances or other colorations, cheap, simple to make, easy all around.


I do want to do it decently right. I don't want to buy a closeout $2 driver and hope it works. From the looking around I've done I will have to have a driver with a QTS higher than .5 and at least a couple or more mm of excursion. I'll only want these to respond down to 60 hz maximum and 120 hz minimum. I figure I can build a cheap small sub to work below that.


Fostex or seas drivers look the way to go. The fostex drivers are a little over $100 each and have a high sensitivity of 96 or 97 db/w.


Thoughts? I'm a big researcher so I will probably spend the next month or more looking into this before I cut a hole in a board.
 

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The guys on DIY audio are all over this stuff. Audio nirvana drivers are commonly used in OB. Might get pricey though. The Mark Audio stuff is about the only Full Range stuff I like. Not sure they make good OB candidates though.
 

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Quote:
Originally Posted by brandonnash /forum/post/20853787


Thoughts? I'm a big researcher so I will probably spend the next month or more looking into this before I cut a hole in a board.

To date I've not heard any OB designs I've liked (dynamic, electrostatic), and missed the chance on the w/e past to hear another set that might change my mind.


Martin King has a couple of well written articles on his www.quarter-wave.com site using Fostex and Eminence A15 that you should read.


I'd also suggest trying to hear some first if you can: you may love 'em, you may hate 'em.
 

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Quote:
Originally Posted by brandonnash /forum/post/20853787


I've been looking around doing some research on some full range open baffle speakers. These will be for music only and I may end up putting them on my pc for listening to lossless audio but even if I don't they will be for light use. No high spl's. I'm wanting to do this more for experimenting more than anything. Single driver, no crossover, open baffle so no enclosure resonances or other colorations, cheap, simple to make, easy all around.


I do want to do it decently right.

That'll take at least a 2-way (to reach 100Hz) and either low sensitivity (accept 80dB/2.83V/1 meter) with expensive passive components or line-level compensation for dipole roll-off.


Otherwise you end up with a multi-lobed polar response mess that doesn't sound natural or good even when running $40,000 a pair field coil Feastrex drivers.

Quote:
Thoughts? I'm a big researcher so I will probably spend the next month or more looking into this before I cut a hole in a board.

Build something like Linkwitz's PMT1. Note the narrow baffle, low cross-over to the dome tweeter, and passive line-level shelving filter.

http://www.linkwitzlab.com/proto.htm
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by tuxedocivic /forum/post/0


The guys on DIY audio are all over this stuff. Audio nirvana drivers are commonly used in OB. Might get pricey though. The Mark Audio stuff is about the only Full Range stuff I like. Not sure they make good OB candidates though.

Yeah I saw some of the stuff on diyaudio. Just thought I would try on here first. Get some discussion going here that's unusual. Kind of like before the tht and dts-10 there was no horn talk at all.

Quote:
Originally Posted by A9X-308 /forum/post/0


To date I've not heard any OB designs I've liked (dynamic, electrostatic), and missed the chance on the w/e past to hear another set that might change my mind.


Martin King has a couple of well written articles on his www.quarter-wave.com site using Fostex and Eminence A15 that you should read.


I'd also suggest trying to hear some first if you can: you may love 'em, you may hate 'em.

I'd love to hear some. No one around me has any. That's the experimentation part. I figure if I don't like the sound I can sell the speaker or just the drivers. Or try to keep them for a full range back loaded horn. I'll have a look at that link.
 

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John Kreshovshy's www.musicanddesign.com has a ton of other useful articles. He's the designer of the NaO O/B range.
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by Drew Eckhardt /forum/post/0



That'll take at least a 2-way (to reach 100Hz) and either low sensitivity (accept 80dB/2.83V/1 meter) with expensive passive components or line-level compensation for dipole roll-off.


Otherwise you end up with a multi-lobed polar response mess that doesn't sound natural or good even when running $40,000 a pair field coil Feastrex drivers.


Build something like Linkwitz's PMT1. Note the narrow baffle, low cross-over to the dome tweeter, and passive line-level shelving filter.

http://www.linkwitzlab.com/proto.htm

How would I have a polar response mess? I don't know why that's the only reason I'm asking. It would seem that (without seeing an impedance graph) the response overall would be prett linear and placement or acoustic treatments should be key in defeating any dipole reflections from walls. Like I said, I don't know and this is just for trying out more than anything. I'm not looking for an end all speaker system, but if there is potential I'll further experiment.


One of the designs that at least in theory looks good is on www.decware.com . The zen open baffle. It uses a hollow chamber to resonate lower frequencies much like blowing across the top of a coke bottle. That to me sounds at first like it shouldn't work (single frequency resonance) but he says the interior design acts nearly like a horn and catches a more broad band. Not sure how much I believe that but I guess if justin beiber, however you spell his name, can make a career singing horrible music to 8 year olds then anything is possible. Problem with his design is it uses his driver exlusively. The driver is odd looking. Has some either huge magnet or odd attachment to the frame that makes it about 3x as deep.
 

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Quote:
Originally Posted by brandonnash /forum/post/20854189


Get some discussion going here that's unusual.

In that case, GREAT! These boards could use some variety. So I'll add.


I just heard some OBs on saturday. Can't say what the drivers were now. Heard a lot of speakers that day of the full range variety. Probably about 15 sets of full range all from the same designer of these OBs. And well, they weren't good. They had a huge baffle made of plexi. They were run wide open without any filtering. They were interesting.


That's only one example. Just for the sake of discussion. Like I said, I heard a lot of stuff that day. For the money, the CSS EL70 wins hands down over and over. I listened to Alpairs, Fostex, Tang Bands, of all sizes and enclosure types. Some were better, barely, but for the money... A number of people walked away buying the EL70s. Just not sure how suited they are to OB. They make crazy bass for a 4" though. I bought a pair to put on my desktop.


Here's my measurement of the EL70 when I borrowed a pair a while ago:


Spliced at 350hz nearfield in ported enclosure
 

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Discussion Starter · #9 ·
I wish someone would have a hifi show closer to TN. I'd like to be able to hear dozens of different designs in one day. All I can get here close to that is a ht/car audio shop. They have some high end stuff, but its all dynamic or electrostatics or klipsch reference lines. Nice stuff, but all pretty much run of the mill stuff.


The idea of the full range open baffle is what gets me. I'll post some links in a few that have some open baffle designs that look promising, but very very few I have seen anywhere incorporate full range drivers along with them.


I'm running horn loaded on all 5.1 channels now and really enjoy the extra dynamics, but if there's an easy way to diy a bit of extra resolution out of a recording I want to try it.
 

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I love OB, but cannot stand fullrange, single driver setups most of the time. How's your HF hearing? Many of these drivers exhibit some type or rising HF response that annoys my ears terribly. The supposed benefits of no xover don't seem trump the tradeoffs.


When I was building these, I tried MANY drivers for mids, hoping to find something suitable for a wide range mid and had several "full range" drivers on hand. All sounded tonally imbalanced even after EQ.
 

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Quote:
Originally Posted by brandonnash /forum/post/20854300


How would I have a polar response mess? I don't know why that's the only reason I'm asking.

Acoustic dipoles have a nice cosine-alpha polar response (-3dB at 45 degrees, -6dB at 60 degrees, -12dB at 75 degrees, etc.) with 4.8dB of directivity through about .25 v/D Hz with v the speed of sound and D the path length separation which approximately equals baffle width on rectangular baffles.


Above that point the response broadens (reaching a 6dB on-axis peak at .5v/D Hz) and breaks down into a multi-lobed pattern approaching the dipole's first on axis null at v/D Hz.


At .17 v/D the dipole's output matches a monopole's at the same excursion.


Solving for a domestically friendly foot wide baffle we find this occurs at 192Hz.


The "simple" solution is to use a wider baffle, with a two foot wide baffle pushing that point down to 96Hz.


That produces a first dipole null at 565 Hz which is not the sort of thing you want to hear in the midrange.


The right solution is to use narrow baffles, boost the drivers' low ends electronically to get more bandwidth in fewer ways, and cross-them over to the next higher frequency driver before the polar response deteriorates.


You get more wiggle room where the drivers are close to baffle width and are becoming directional on their own.


You want to read Siegfried Linkwitz's web site

http://www.linkwitzlab.com/models.htm#A
http://www.linkwitzlab.com


(note the flower-shaped polar response at the first null) and John Krevosky's

http://www.musicanddesign.com


where he puts the upper limit of dipole usability somewhere between d/w (d path length separation, w wave length) = .5 and d/w = 1.

Quote:
It would seem that (without seeing an impedance graph) the response overall would be prett linear and placement or acoustic treatments should be key in defeating any dipole reflections from walls. Like I said, I don't know and this is just for trying out more than anything. I'm not looking for an end all speaker system, but if there is potential I'll further experiment.

I rank every open baffle speaker I've heard with an acoustically large baffle somewhere between bad and mediocre. As much as I like Nelson Pass (he's a great lecturer, really supportive of the DIY community, and does fine things with analog electronics) I include his big baffles (Bob?) in this category even when fitted with the $40,000 Feastrex field coil drivers run both full-range and crossed to dipole sub-woofers.


If you want to use full-range drivers, try narrow back-loaded horns. That can net subjectively great, natural sounding results (especially with the smaller drivers) and some bass.


If you want to build dipoles (I built/own Orions, have heard v4, and listened to other similar speakers - all have been "excellent" or better) accept acoustically narrow baffles, multiple drivers, and low-frequency equalization.


I speculate that my subjective impressions come from what's going on with polar response (narrow baffle = excellent, acoustically large = bad; same driver in a box without the dipole issues = better; hearing of other speakers with more uniform polar response)
 

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Discussion Starter · #13 ·

Quote:
Originally Posted by Drew Eckhardt /forum/post/0



Acoustic dipoles have a nice cosine-alpha polar response (-3dB at 45 degrees, -6dB at 60 degrees, -12dB at 75 degrees, etc.) with 4.8dB of directivity through about .25 v/D Hz with v the speed of sound and D the path length separation which approximately equals baffle width on rectangular baffles.


Above that point the response broadens (reaching a 6dB on-axis peak at .5v/D Hz) and breaks down into a multi-lobed pattern approaching the dipole's first on axis null at v/D Hz.


At .17 v/D the dipole's output matches a monopole's at the same excursion.


Solving for a domestically friendly foot wide baffle we find this occurs at 192Hz.


The "simple" solution is to use a wider baffle, with a two foot wide baffle pushing that point down to 96Hz.


That produces a first dipole null at 565 Hz which is not the sort of thing you want to hear in the midrange.


The right solution is to use narrow baffles, boost the drivers' low ends electronically to get more bandwidth in fewer ways, and cross-them over to the next higher frequency driver before the polar response deteriorates.


You get more wiggle room where the drivers are close to baffle width and are becoming directional on their own.


You want to read Siegfried Linkwitz's web site

http://www.linkwitzlab.com/models.htm#A
http://www.linkwitzlab.com


(note the flower-shaped polar response at the first null) and John Krevosky's

http://www.musicanddesign.com


where he puts the upper limit of dipole usability somewhere between d/w (d path length separation, w wave length) = .5 and d/w = 1.


I rank every open baffle speaker I've heard with an acoustically large baffle somewhere between bad and mediocre. As much as I like Nelson Pass (he's a great lecturer, really supportive of the DIY community, and does fine things with analog electronics) I include his big baffles (Bob?) in this category even when fitted with the $40,000 Feastrex field coil drivers run both full-range and crossed to dipole sub-woofers.


If you want to use full-range drivers, try narrow back-loaded horns. That can net subjectively great, natural sounding results (especially with the smaller drivers) and some bass.


If you want to build dipoles (I built/own Orions, have heard v4, and listened to other similar speakers - all have been "excellent" or better) accept acoustically narrow baffles, multiple drivers, and low-frequency equalization.


I speculate that my subjective impressions come from what's going on with polar response (narrow baffle = excellent, acoustically large = bad; same driver in a box without the dipole issues = better; hearing of other speakers with more uniform polar response)

Would the same hold true for on axis and nearfield? And also do you have the same response in half space? Just trying to understand a bit more and if all the polar response anamolies are induced by room reaction or not. But overall a full range AND open baffle won't work too well but individually they're at least decent.
 

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Quote:
Originally Posted by brandonnash /forum/post/20855607


Would the same hold true for on axis and nearfield?

You still have the on-axis alternating pattern of nulls and +6dB peaks until the drivers become acoustically large with increased directivity and less sound wrapping around the baffle where it interferes destructively.


It's unclear how much of the problems are coming from on-axis response ripples, how much total power response helps mask that, how much disparity between on and off-axis hurt, and how that would change as you move into the near field where things your brain might identify as reflections have more delay and attenuation.

Quote:
And also do you have the same response in half space? Just trying to understand a bit more and if all the polar response anamolies are induced by room reaction or not.

In half-space you have an infinite baffle which is obviously free from issues that exist with front/rear wave interaction.

Quote:
But overall a full range AND open baffle won't work too well but individually they're at least decent.

Right.
 

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Discussion Starter · #15 ·
Thanks for the replies Drew. I think I'll decide on a decent set of full range drivers that will work ultimately in a rear loaded horn and may try them out first in a makeshift baffle just to see what happens. Won't hurt much or cost much to find out and I like learning and being proved wrong because from then on I won't be



Any suggestions on a starting point for a nice full range driver? I've been looking over on parts express and the dayton reference 8" has caught my eye. I love that the dayton as well as the fostex are so sensitive. Their power handling is not great but would be enough to seemingly reach 105-110 db so for my normal listening distortion should be rather low.


EDIT: Now looking at the specs I don't think any of those full range will work. Q is too low but the xmax may be enough to work with. ???? maybe.
 

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I agree with the comment about full rangers sounding shouty. The fostex have this. I think some full range lovers interpret this as enhanced detail. So for suggestions I'll repeat my impressions of the Mark Audio stuff and the CSS EL70. They're extending, and reasonably flat. Having said that, they're inefficient
And I doubt they OB worthy. But, theyre the only FR drivers I'd actually pay for.


The Dayton looks great, but look at the FR curve. You'll need some strong filtering.
 

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Discussion Starter · #18 ·
Never heard those but have heard their in walls once and I was very surprised that in walls could sound that good. I wouldn't have them (extremely expensive!) But if they can do that with in walls I bet the could figure out some dipoles.
 

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They're also not full range OB, nor dipole.
 

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I want to go with totally open speakers no baffle either. How would this compare with open baffle speakers? I guess what I'm trying to say is what benefit does open baffle vs baffless present!
 
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