Sound stage diffences of monopole / dipole systems at different frequencies

[MarzZ]

I simply would like to know the pros and cons for dipole/monopole systems at the low, mid and high frequencies.

I'll start with what I have researched so far:

dipole bass

pros: more accurate and articulate sound stage.

cons: cannot reproduce frequencies below 30-40hz well. Placement is more difficult. Not as efficient and usually requires active crossover and eq.

monopole bass

Pros: sealed box = accurate, with spl tradeoff compared to vented designs.

cons: potential box coloration.

dipole mids

pros: ?

cons: ?

monopole mids

pros: higher efficiency

cons: box coloration

dipole highs

pros: potentially deeper sound stage

cons: detracts from accurate stereo imaging due to more reflections?

[CLS]

Those descriptions are far too generalized.

First of all, I'm done with ordinary boxed speakers, but that's only for myself. Many intelligent people out there can make very good ones... I can't.

As an OB lover, I'd like to point out that there're several mistakes:

1. OB bass can do deep bass, at least usable high 20's ~ low 30's is not a difficult target.
2. Placement of OB bass is not difficult at all. Away from the wall is preferable but not essential.
3. Actively xover'ed (and driven) is not a con, it's essential to a good overall performance, no matter boxed or OB.
4. Others are more to the directivity and power response issues, I'd leave those to other experts.

[Borat]

monopole sounds like it is exactly where it actually is.

a focused source such as ESL panel can sound like it's anywhere in the room.

this makes monopole less interesting but more predictable.

as far as low frequencies - that is totally room dependent.

the only thing i can say with certainty is that you want multiple sealed boxes from about 40 hz and down.

[StigErik]

I have a disagree a little bit with Borat here. Dipole bass is to my experience a lot less room dependant, and its in-room frequency is a lot more predictable. In my own room (which is quite good), monopole speakers always require some room correction to measure flat, and to sound good. My dipoles dont, not at all.

I also found that my current dipoles sound great over almost the entire room, which certainly is far from what most monopoles will do. If you pay attention to the off-axis response, they will sound great virtually anywhere in the room. To achieve this, you will have to operate all drivers below the dipole peak. The consequence is lower efficiency, and dipole compensation EQ is required for all drivers.

Dipole bass below 40 Hz is cetainly possible, but will require multiple and/or large diameter drivers.

I would say that the cons of all boxed speakers are; box colorations; inferior power reponse / off-axis response and very bad room integration. After my own little open baffle experiment, I was shocked by how much better a proper dipole can sound. There is no turning back to boxed speakers for me either!

[iggy111]

What drivers did you guys use for your OB/dipoles? Is it possible to construct a good dipole from existing boxed speaker drivers (eg Tannoy Eyris 3)? Sorry if this is too off topic

[Drew Eckhardt]

Originally Posted by iggy111

What drivers did you guys use for your OB/dipoles? Is it possible to construct a good dipole from existing boxed speaker drivers (eg Tannoy Eyris 3)? Sorry if this is too off topic

Probably not.

1) At lower frequencies (compared to baffle size; wave lengths of .17 v/D with v the speed of sound at 1130 feet/second and D the path length difference between front and back waves) it takes a lot more displacement (The Linkwitz Orions use nearly 2X the displacement of a monopole at 80Hz and 4X at 40Hz; although built as a 2-way with the same baffle width the numbers would be more like 4X and 8X) to reach the same SPL levels you get with a conventional speaker.

Polar response constraints limit baffle and mid-range driver size so you need a 3-way and perhaps an extra beefy tweeter to meet the larger mid-range.

2) The drivers need to be free of aerodynamic and mechanical noises

Reading Siegfried's web site

http://www.linkwitzlab.com

and John Krevosky's web site

http://www.musicanddesign.com/

would be a great starting point.

I've had a set of Linkwitz Orions in my main system since 2003
http://www.linkwitzlab.com/orion_challenge.htm

Provided that you can live with the cabinet size and placement constraints. I don't think you want anything else for the bass down to 40-50Hz - the difference is remarkable when you aren't coupling as strongly to the height and width modes. In the mid-range on up a wave guide may be a better alternative but a boxed speaker is not.

Room placement is non-critical compared to conventional speakers or planar speakers (which cease to approximate dipoles as they become acoustically large at high frequencies or cross to a box woofer in the lower mid-range as with many hybrids)

[Drew Eckhardt]

Originally Posted by StigErik

I also found that my current dipoles sound great over almost the entire room, which certainly is far from what most monopoles will do. If you pay attention to the off-axis response, they will sound great virtually anywhere in the room. To achieve this, you will have to operate all drivers below the dipole peak. The consequence is lower efficiency, and dipole compensation EQ is required for all drivers.

Most "monopoles" aren't, having at least the power/polar response dip as they transition to a broad-dispersion tweeter a significant distance from their midrange.

Better monopole approximations (Linkwitz Pluto, with a 6" mid-bass crossed to a 1.6" mid-tweeter on a 2" baffle a few inches away at 1Khz) retain the same timbre regardless of where you park yourself although imaging collapses into the nearer speaker sooner than more directive speakers and they don't retain the same transparency as far into the room.

[MarzZ]

Ok I will be more specific for what I am thinking of putting together.

I love the sound of newform research monopole line source ribbons for the the upper frequencies, say 5khz and up. I think some of the added benefit is that their vertical dispersion is very narrow and reduce reflections from the ceiling and floor.

I heard some martin logans and really was impressed with the midrange resolution, especially the sound of a trumpet. These are obviously dipole planars and wonder about integrating them with the ribbons since they share the vertical dispersion restrictions.

I have not heard dipole bass before and I am curious. I want the ability for high spl accurate/fast mid bass. I'm a bass player and this part is very important as well. The best bass I have heard so far was in the Genelec room at cedia a number of years ago.

I have the lower frequencies covered (80hz and below) with a sealed 18" from bag end, which I will double in the future.

What are your opinions? Does this sound like a good project? I would rather learn from other's mistakes if possible. I'm pretty sure I am going to have to triamp and go active with crossovers (DCX2496).