Easiest Dipole to build. In Arvo Pärt MkIII Tall Vein.

[intelonetwo]

I'd like to build another pair of speakers before the summer comes. In the past I've built a tapered quarter length speaker, a transmission line speaker with adire audio drivers, and some other bookshelf speakers.

This go around I'd like to build a speaker I can hang onto for awhile. For this project, I need a dipole design, easy woodworking (circular saw, jig saw, sander, and screwdriver are all I got), and full range (I will be using one or two 12" subwoofers, however).

Since I have NO soldering skills, all crossover functions must be done via electronics (Beheringer Active EQ, etc), I have ample amplification channels.

I happen to like the Arvo Pärt MkIII Tall (type 3) version with the large angled baffles. Are these as simple to build and sound good as they look. That may be a silly question, I do realize, but I think JonMarsh have already figured out all of the rough spots and cured them.

Any suggestions?

Thanks.

[JonMarsh]

The current evolution of that train of thought and work (including test baffles, driver testing, etc.) is the Arvo Isiris project, a relatively current thread.

Concept starting like this,






First test baffle,











But new LF drivers and new waveguides and HF drivers in route or already here for evaluation in the next few weeks, time available. No changes anticipated in the midrange driver choice.

I have the possibility of raising the LF sensitivity quite a bit for a single passive crossover system. Not that that precludes going active, but if all the drivers are in the 92-23 dB/watt sensitivity range or higher, is there really a point? (soldering is not to hard to do, and I'm considering if this works out as well as I hope, offering packaged crossover assemblies).

Don't really want to talk more about it yet than what's already posted in the Isiris thread. For reference, the current working height of the test baffles is 48". I even bought a new integrated for voicing the speakers as they get close to completion. Of course, that might just be an excuse to upgrade my secondary system- it does VERY well driving Modula MTM's.

[intelonetwo]

Jon,
From a visual standpoint The Arvo Isiris is stunning. I'd would like to hear how it sounds with my Sunfire Sig.

The dipole design has been on my radar for quite some time now since it allows a modest builder to build and design it with few woodworking tools.

The active portion and subsequent eqing are all doable, but the packaged x-over would be nice to have available, as it would be a cheaper (albeit less tweakable) alternative. I'd be interested in exploring this option instead of the active x-over.

[Mazeroth]

Jon,

What method did you use when cutting out the driver cuts for the rear brace? The reason I ask is because they look very well cut! I couldn't see myself drawing something that nice with a pencil and taking the trusty old jig saw to it. ;x(

[JonMarsh]

Ask ThomasW about this- I am "good" with a jig saw- in my 20's I used to build folded horns and Altec A7 Klones with nothing more than a jig saw. Good as in 1/16 to 1/32" good. Then, the cuts are finished with a 1/4" roundover on both sides of the MDF laminated to the BB ply.

Regarding drawing it, that's what compasses or port tubes are for- to get the nice curves in pencil. Just a little planning- nothing much compared with the trouble of doing the CAD drawing.

[JonMarsh]

Jon,
From a visual standpoint The Arvo Isiris is stunning. I'd would like to hear how it sounds with my Sunfire Sig.

The dipole design has been on my radar for quite some time now since it allows a modest builder to build and design it with few woodworking tools.

The active portion and subsequent eqing are all doable, but the packaged x-over would be nice to have available, as it would be a cheaper (albeit less tweakable) alternative. I'd be interested in exploring this option instead of the active x-over.

With passives it's possible to "plan" for some tweaking; I'm considering the possibility of having a BBC Dip Switch (pun intended) so that for those not liking the way close miked stuff sounds on a "flat" speaker they can get the more distant, more "polite" perspective. Might be good for a lot of commercially recorded CD's. With the controlled dispersion this system should have, I'm less convinced that an overall HF level control is needed, since the whole point is reducing the interaction with the room. But who knows, maybe that, too, though probably only 2 or three positions.

~Jon

[clearwaterms]

Are there any other simple dipoles out there, smaller designs or other simple low cost, preferably passive designs?

[intelonetwo]

clearwaterms:
Design of Dipole are simple when compared to a box speaker of similar performance, but he complexity of electronics to use, etc are much more of an issue.

Jon,
Having a HF control for to minimize room interaction is less of a concern for me since in this case, advance have been made in room eq technology. It is possible to make the speaker as minimal as possible, then use electronics to account for some of the nasties up high and in the middle, as well as the low end.

How are the drivers and speaker panels cut out? Reading the previous post, did I read it right, your only using a circular saw, and jig saw, with router to cut out the holes, and roundover the edges? That would make me feel good as these are the only tools I have.

Jon do you have some plans so that could start to look at them for preparation of wood purchasing and begining cutting? What material are you using and in what way ie. how are you sandwiching the the woods and what type and size of woods are you using?

[JonMarsh]

For the Isiris, I've only been using a circular saw with guide clamps (Porter Cable 423 MAG with Oldham 60 tooth ultra finishing carbide blades),




a half inch shaft router with jasper jig to cut the through holes and a rabbeting bit to cut the rim recess. (my favorite is the Hitachi 12V, but my DW621 DeWalt is dedicated to the Jasper Jig).

The inside cuts on the back brace are done with a Bosch saber saw with Bosch blades (if you don't have a Bosch saw, at least get there fine wood finish blades, a special outside blade cut pattern and sharp as heck). The base and back in the proto are sandwiched BB play with 1/4" HDF glued to each side, 1/4" rounde over for the inside and outside edges of back brace and base. the full intended base design isn't implemented. The back braces and base were ripped on the table saw, but there's no reason that can be done with the circular saw.

The "upscale" version of these may use some manufactured or synthetic sheet material; this is in investigation right now. The more bang for the buck oriented one would use laminated HDF for the front baffle, as all the earlier Arvo Part have. Back brace and brace are laminated from 20 mm BB ply at the core and 1/4" HDF on each side.

Design and layout is done using EDGE simulator to optimize baffle shape and driver position; it's easily as complicated as doing a box speaker, though there's no worrying about ports or stuff, obviously.

Until the final driver choices are done, it's premature to talk about wood purchasing, except the raw stuff. You can get the 1/4" HDF in 2' X 4' sheets at the big Orange box store, but BB ply may take a little hunting around depending on where you are; I get mine from Rockler. I go through a lot of Tiebond II laminated up the baffle panels, using 2"X2" angle iron to keep stuff straight, and I find a bathroom squeegee is the easist/cheapest tool for spreading Titebond quickly and easily.

For mounting drivers on HDF I use threaded steel inserts from Rockler in the baffle, and stainless steel button head screws. 8/32" for midrange, 10/24 for the woofers.

I need to order a pair of RS390HF to test soon for the "budget" version, but may have to delay that a little bit because of business travel in February. The other batch of drivers are coming in tomorrow according to UPS.

[LoudandClear]

Are there any other simple dipoles out there, smaller designs or other simple low cost, preferably passive designs?

Yep. Go Full Range Driver. The Visaton B200 is one of the most popular single driver dipoles right now. There is tons of info on AC (search "Darkstar") and DIYAudio on this driver in dipole configuration.

Here's a post with where I took mine:

Dual Visaton B200's on Corkboards

Excellent performance for the dollar. I've got the dipole bug now and the Isiris is very high on my list for my next "real" project.

Good luck

[clearwaterms]

okay,

in a dipole the idea (the way I understood it) was to give you a room full of sound, that very filling experience. How does that effect the surround sound experience? where you want some localization to be able to get the effect of the explosion behind you or the vocals from within the boundaries of the screen. I am sorry if this question is unclear.

I understand that the concept of a quality speaker is it's ability to disappear and present the music as accurately as possible. and the concept of imaging is to be able to locate the instruments as if the band was in front of you, and not a pair of speakers. And I have been told that dipoles do that better then a lot of other speakers because of the fact that they don't interact with rooms as much as other speakers. If you were to use dipoles as your HT speakers (people use Magnepans and Martin Logans, which are a variation of dipole, right?) does that effect the localization that you want in a room?

[JonMarsh]

I dont' see the idea behind a dipole as being what you describe- in fact, the major advantage of a dipole is that it has much more limited dispersion than a conventional speaker (figure 8 versus speherical), and it reduces the excitation of room modal responses considerably compared with a monopole source. There are other benefits, such as not having a midrange driver backwave immediately reflected back through the cone as may occur in a poorly designed enclosure. Also, with good design, the on axis response and off axis repsonse should track much more closely (better balanced power response). in general, a well designed dipole will have a much better sense of bass pitch definition and detail and articulation, may have a smoother more timbrally balanced midrange, and reproduce aspects of the recording acoustic more clearly, and more prominently over the playback room acoustic.

If you were to use dipoles as your HT speakers (people use Magnepans and Martin Logans, which are a variation of dipole, right?) does that effect the localization that you want in a room?[QUOTE]

Not really sure what you mean about this. You don't ever want the speaker coming from the box; localization is always about the balance of audio between multiple speaker sources (two or more).

A well executed dipole system, IME, will better reproduce the sound stage creating in the mixing studio for the movie, just as it better recreates an album "sound stage". This could apply to rear channels, too.

The conventional HT wisdom of the rear speakers being OK as much smaller speakers with different dispersion patterns than the mains is rather suspect; it's not just my opinion, but also that of some fairly heavyweight experts, such as the staff of Widescreen review magazine. A full surround dipole system would not be cheap or easy to implement, but it would probably sound rather good.

Just my opinion. I'm more a 3.1 kind of guy, anyway, at this time, due to space limitiations.

[clearwaterms]

I dont' see the idea behind a dipole as being what you describe- in fact, the major advantage of a dipole is that it has much more limited dispersion than a conventional speaker (figure 8 versus speherical), and it reduces the excitation of room modal responses considerably compared with a monopole source. There are other benefits, such as not having a midrange driver backwave immediately reflected back through the cone as may occur in a poorly designed enclosure. Also, with good design, the on axis response and off axis repsonse should track much more closely (better balanced power response). in general, a well designed dipole will have a much better sense of bass pitch definition and detail and articulation, may have a smoother more timbrally balanced midrange, and reproduce aspects of the recording acoustic more clearly, and more prominently over the playback room acoustic.

If you were to use dipoles as your HT speakers (people use Magnepans and Martin Logans, which are a variation of dipole, right?) does that effect the localization that you want in a room?

Not really sure what you mean about this. You don't ever want the speaker coming from the box; localization is always about the balance of audio between multiple speaker sources (two or more).

A well executed dipole system, IME, will better reproduce the sound stage creating in the mixing studio for the movie, just as it better recreates an album "sound stage". This could apply to rear channels, too.

The conventional HT wisdom of the rear speakers being OK as much smaller speakers with different dispersion patterns than the mains is rather suspect; it's not just my opinion, but also that of some fairly heavyweight experts, such as the staff of Widescreen review magazine. A full surround dipole system would not be cheap or easy to implement, but it would probably sound rather good.

Just my opinion. I'm more a 3.1 kind of guy, anyway, at this time, due to space limitiations.

Jon,

thank you for clearing that up. I was obviously very misinformed about dipoles. Thank you again.

[intelonetwo]

I believe the drive to make rear speakers more acceptable to the signficant other has all but sterilzed the rear speaker. I too believe that the center and rears should be of the exact design, size as the mains ran in full range. No crossover filters. Only the subwoofer operating the LFE channel, and low end fill is so choosen by the user.

I've heard the best surround system use this setup and it was a beautiful thing. Now to throw dipoles in the mix, llike et's say a 7.1 Arvo Isiris system, well that I believe would be a tremendously fulfilling system to own and listen to.

[clearwaterms]

I believe the drive to make rear speakers more acceptable to the signficant other has all but sterilzed the rear speaker. I too believe that the center and rears should be of the exact design, size as the mains ran in full range. No crossover filters. Only the subwoofer operating the LFE channel, and low end fill is so choosen by the user.

I've heard the best surround system use this setup and it was a beautiful thing. Now to throw dipoles in the mix, llike et's say a 7.1 Arvo Isiris system, well that I believe would be a tremendously fulfilling system to own and listen to.

just out of curiosity, how do you put a full tower design as a center channel? short of a projection screen with a accostically transparent screen

[Ecir38]

7.1 Arvo Isiris system, well that I believe would be a tremendously fulfilling system to own and listen to.

Now this would be awesome.

[JonMarsh]

just out of curiosity, how do you put a full tower design as a center channel? short of a projection screen with a accostically transparent screen

we've done a lay down center channel dipole design once, and the other alternative is what you'd call phantom center channel. I've run my older Arvo's in that mode, and the experience was very satisfying- the improvement in ambient sound retrieval gave some movie soundtracks an amazing sense of depth, something usually rather lacking.

Personally, I don't like perf screens, particularly not for HD sources or digital projectors, but I know they manage to pull it off pretty well at some movie theaters, like our local DLP Cinema systems, which really look great and sound pretty good. IMAX is another example. I think the issues is the relative size of the sceen versus the perf hole size and the minum detail size; scaled up works OK, scaled down maybe not so good. To each his own.

BTW, the straight side of the Arvo Isirs goes towards the inside... and one of the things I will be trying these with is my NEC 10PG projector and HD-DVD. TureHD sound tracks sound awesome, if you've never heard one before!

~Jon

[clearwaterms]

we've done a lay down center channel dipole design once, and the other alternative is what you'd call phantom center channel. I've run my older Arvo's in that mode, and the experience was very satisfying- the improvement in ambient sound retrieval gave some movie soundtracks an amazing sense of depth, something usually rather lacking.

Personally, I don't like perf screens, particularly not for HD sources or digital projectors, but I know they manage to pull it off pretty well at some movie theaters, like our local DLP Cinema systems, which really look great and sound pretty good. IMAX is another example. I think the issues is the relative size of the sceen versus the perf hole size and the minum detail size; scaled up works OK, scaled down maybe not so good. To each his own.

BTW, the straight side of the Arvo Isirs goes towards the inside... and one of the things I will be trying these with is my NEC 10PG projector and HD-DVD. TureHD sound tracks sound awesome, if you've never heard one before!

~Jon

i can't say that I have had the pleasure of hearing TrueHD.

[JonMarsh]

It's on the new hi rez DVD formats- HD-DVD and is theoretically supported on Blu Ray, but few or no releases with it. Because the player specs are still a bit fluid in Blu-Ray, most disks have been released with straight PCM tracks for the audio.

[Dennis H]

Perf screens are so 20th century. For DIYers the SMX woven material is the hot acoustically transparent setup. Good sound, good picture, gain a bit over 1.

For those who don't know, SandmanX over at AVS went looking for the ultimate material, got samples from lots of woven blind fabric makers, and ended up having a custom run done with finer threads. Now he sells the stuff. It isn't exactly cheap but it's much cheaper than a Clearpix and reportedly performs better. Alan Gouger, the owner of AVS, is using it for his huge curved screen so that's a pretty good recommendation.

http://www.smxscreen.com/

[LoudandClear]

If you were to use dipoles as your HT speakers (people use Magnepans and Martin Logans, which are a variation of dipole, right?) does that effect the localization that you want in a room?

The other thing to keep in minds with many dipole panel speakers and dipole full range speakers (ie Visaton, Fostex) is the beaming effect of the higher frequencies leading to a very narrow "sweet spot". Off-Axis listenting can sometimes be muted which may not be very impressive to some if you are have a good size group watching.

[Ecir38]

TrueHD sound tracks sound awesome, if you've never heard one before!
~Jon

I thought you would explain this as "music from out of space". You have to see the Direct TV HD commercial to understand this :B .

http://www.youtube.com/watch?v=uwiw7cxyvys

[JonMarsh]

Setup is would be important- some distance from viewers, and some toe-in. Generally dynamic driver dipoles will have about a 90 degree wide window, which is up to 45 degrees off axis. It's not hard to configure for a fairly good size listening area; a conventional monopole will be about 120 degree included angle, except at high frequencies, because of fall off that far off axis.

In other developing news, the other set of HF drivers arrived today, along with the DDS ENG-1 waveguides and Ciare 18" Neodymium magnet woofers. On the frame it's got lettering saying "Magneisum", which is a little surprising, but then the 18" driver with 4" VC is only 6.2 kG, about 14 lB. Not much more than the Aurasound 12's.

The DDS waveguides make up for that, as they're made from real fiberglass, quite strong (nothing like the MCM), and fit the driver perfectly. They seem to have a profile a bit like what I can see in the SP Tech speakers, but with a smaller mouth diameter on the "straight" portion and a gentler transistion to the baffle plane. Interesting.

Was hoping to do some measurements this evening, but installing Vista with Boot Camp on my Mac Pro laptop took a little more time to sort out some driver issues, but we're good to go, and posting from Vista right now as a test. It's just so I can run LspCAD and MathCAD and Altium Designer on this laptop.

Well, gotta work out- see you guys later!

[Beau]

Jon, I can get hold of a pair of brand new Beyma cp-380m compression drivers and DDS waveguides at a good price, I know you are still in the process of testing but do you have any idea if these would be a suitable candidate for Hf duties?

[JonMarsh]

The published data in a TD-250 horn looks pretty good...



But without testing it's hard to know how they'll look in the DDS ENG-1. This looks like a driver a little more oriented to the lower frequency range, with response rolling off above 18 kHz, instead of ~25 kHz like the less expensive BMS 4540. It's also a polyester diaphragm driver, like the BMS4540.

But possibly quite usable, especially if you get a friendly price. At MSRP I don't see the value compared with the BMS driver.

One of the problematic issues with compression drivers and passive crossovers is the interaction of the impedance curve with filters and Lpads, and from the PDF download from Beyma on this driver, it has a number of resonances to deal with - but they may also be a function of the TD250 horn it's tested on. This is a common issue that the horn loading in the bottom end of the range affects the Z curve. Not sure how easy or hard it will be to compensate for in a DDS waveguide.

I looked at a LOT of HF compression drivers online over the weekend, including 18 Sound, all the BMS drivers, some of the Beyma drivers, etc. Since the DDS-1 is available both in threaded and plate mount versions, there's some flexibility about what could be used if that winds up being the choice for the waveguide. (I'm leaning that way for now, in spite of the size of it). And I appreciate inputs about possible drivers from anyone- will have to look closely at data sheets, because I really can't afford to buy and try every possible candidate.