The Totem of Tone, an active 3-way dipole and active subwoofer

[manninen]

If i some day do outside measurements i borrow an forklift from ORO-contractors.

ps. damn that AE top plate is THICK!

 

[gainphile]

This is a very COOL project!!

 

[Gerrit Boers]

This is a very COOL project!!

Thank you
While searching for information and inspiration I also visited your blog and studied your designs, thank you for making all this information available.


regards,

Gerrit

 

[Eldam]

Hi Geritt,

Cool design !

What was your trade offs to put two 10" instead one 12" but comming from the Professional world (strong motor & good Xmax) ?

Regards

Eldam

 

[Gerrit Boers]

Hi Geritt,

Cool design !

What was your trade offs to put two 10" instead one 12" but comming from the Professional world (strong motor & good Xmax) ?

Regards

Eldam

Thank you
Purely the width of the driver for the dipole behaviour and aesthetic reasons. Coming from the Linkwitz Orion I knew that 2 10" would be more than enough for my situation. As I mentioned earlier it was my intention to build something better AND smaller than the Orions. If my living room would be 10m x 10m I'd put a 21" on the floor, 10" or 8" above it and the Neo10 and ribbon above that (or something like that).
The only possible change I can see now is adding another amplifier and apply separate filtering for the lower and upper driver so that only the upper driver goes up to 400Hz.

regards,

Gerrit

 

[Eldam]

I understand now : you wisch was the minimal width for going in the low end. I believed it was more about polar patern of the 10" in relation to the Neo 10 just above...

Thank you Geritt.

 

[manninen]

Might be that 21" and 10" runs out of juice same time. i have 18" and 15" and 15" has plenty of left when 18" gives all it has.

but yea, neo10. im trying to get four of them at the moment

 

[Gerrit Boers]

I understand now : you wisch was the minimal width for going in the low end. I believed it was more about polar patern of the 10" in relation to the Neo 10 just above...

Thank you Geritt.

The polar pattern is an important part of the consideration and a 12" will not have as good a polar pattern at 400Hz as a 10". I hope that the 10" polar matches with the Neo10 but that remains to be seen as I cannot perform those measurements at home in any meaningful way.


regards,

Gerrit

 

[Juhazi]

As per my experience dipole pattern is quite tricky to get right with (especially two) cone drivers.

The drivers' magnets and frames will do nasty things - directivity gets ragged way before the dipole peak at 45-60¤ and specially at 120¤ and more. Because of that usable range will be limited but 400Hz should be ok for double 10".

This will happen with every size of drivers, that's why planar dipoles are superior in the very critical 1-6kHz range. Bass (perception) is not so sensitive to uneven radiation and frequency response wiggles.

Below is Edge simulation of nude 12" and double 10" in 40x60cm frame on-axis response where you can see dipole loss, peak and null. Notice the difference in peaks not nulls!

 

[manninen]

Magnety-thing Juhazi mentioned this AT 10" looks like worst possible, but is it really issue under 200hz?

Most def if motor is silent it goes over looks

 

[Juhazi]

Below is Edge simulation of nude 12" and double 10" in 40x60cm frame on-axis response where you can see dipole loss, peak and null. Notice the difference in peaks not nulls!

I forgot to say that problems with far off-axis and rear radiation appear at and above the dipole peak. That is why as a rule of thumb I recommend lowpassing rather deeply right after dipole peak, which usually means 1 octave before dipole null.

 

[keyser]

Keyser, thanks for the informative reply.

A ground-plane measurement on these no baffle (or worse yet, suspended driver) dipole speakers looks to be practically impossible... and how would you even begin to do horizontal off-axis measurements?

Why impossible? Just put the speaker and the microphone on the floor, tilt the speaker so that it is aimed right at the microphone.

An externally hosted image should be here but it was not working when we last tested it.

For the midrange and high frequencies you get the free-field, full sphere response. For the bass it's a different story. Under normal operating conditions, the ground in a way is a part of the loudspeaker.
At low frequencies the woofers always radiate into a half sphere, gradually shifting to more like full sphere at higher frequencies. You have to take that into account.

Doing off-axis measurements indeed is quite a hassle with the ground-plane method.

Putting the speaker and mic up on a stand looks like the better technique, even if it requires some engineering. The higher the better, but what is high enough for decent resolution for crossover design at, say, 300Hz? And what are your thoughts about mic distance?

One thing to consider is that if you were to lift a speaker such as the Totem of Tone high into the air, there will be diffraction at the bottom of the enclosure. This would not happen under normal conditions, if the speakers stands on the floor. For loudspeakers that are designed to be mounted on a stand, this of course is not an issue.

An externally hosted image should be here but it was not working when we last tested it.

They actually should have tilted the speaker towards the mic.

You always want better frequency resolution. If you know the drivers are well-behaved and there are no significant box-resonances, you can get away with a relatively low frequency resolution, because you already know there aren't going to be serious narrow peaks or dips. Personally even under those conditions I would aim for at least 20 ms for the woofer, a little less for the midrange.

 

[Eldam]

As per my experience dipole pattern is quite tricky to get right with (especially two) cone drivers.

The drivers' magnets and frames will do nasty things - directivity gets ragged way before the dipole peak at 45-60¤ and specially at 120¤ and more. Because of that usable range will be limited but 400Hz should be ok for double 10".

This will happen with every size of drivers, that's why planar dipoles are superior in the very critical 1-6kHz range. Bass (perception) is not so sensitive to uneven radiation and frequency response wiggles.

Below is Edge simulation of nude 12" and double 10" in 40x60cm frame on-axis response where you can see dipole loss, peak and null. Notice the difference in peaks not nulls!

Thanks Juha for the simulation.

Is there any influence of the Qts in this mid-bass range (say100-200hz to 800 hz) ?

Looking ar Oliver's pdf it seems 8",10",12" give close results and above 200 hz & below 1000 hz. Yes same big dipoll null after... not sure how to deal with that, I thought to a circular 5"... as the Neo8 asks also so eq in its low end on OB or infinite bafle (B&G datasheet) !

Do the two 10" so bad if XO before 1000 hz ? (dipoll nule is no more a trouble... at least below 1000 Hz!). I believe I understant more the Gradient bafle of the original design and its little circular U-Frame (it is short but at least it seems a U-Frame with holes à la cardioid !).

@ Gerritt,

Hi : you should like this one also in 25 cm specs : http://www.lamaisonduhautparleur.com/hp/PHL/Pdf/SP3020.pdf ! though uglier in relation to yours 25 !

 

[Juhazi]

Thanks Juha for the simulation.

Is there any influence of the Qts in this mid-bass range (say100-200hz to 800 hz) ?

Looking ar Oliver's pdf it seems 8",10",12" give close results and above 200 hz & below 1000 hz. Yes same big dipoll null after... not sure how to deal with that, I thought to a circular 5"... as the Neo8 asks also so eq in its low end on OB or infinite bafle (B&G datasheet) !

Do the two 10" so bad if XO before 1000 hz ? (dipoll nule is no more a trouble... at least below 1000 Hz!). I believe I understant more the Gradient bafle of the original design and its little circular U-Frame (it is short but at least it seems a U-Frame with holes à la cardioid !).

I can't say anything about Qts meaning but it is weaker effect than acoustic dipole loss.

Dipole null is handled by not letting it appear in the passpand, set xo low enough.

Gradient Helsinki has a sandwich/cookie cardioid baffle. Basically it prevents backside radiation and pushes it to the sides. On-axis radiation keeps the dipole dip and peak (shifts a little) but null almost disappears. The change in total radiated power is small compared to dipole, but you should not place the speaker near a side wall. I actually made a prototype for my Ainos, but decided to stay with classic dipole.

An externally hosted image should be here but it was not working when we last tested it.

 

[Eldam]

I agree that "Look" is important and not only for WAF, The Graidient is one of the rare good looking speaker (ah oh the u-frame was in fact a sealed cookie with holes for cardioid radiation !), like a lot also the waveguid for the treble like the glass to make the design even lighter to the eye ! In another completly another look , I like also very much the Vivids.... and the Anthony Gallo Ref. 3 !

I find Gerrit made also a very good looking speaker ! The sandwich thick bafle is awsome. I'm not against paralepiped enclosure : my speaker :Mon Système.. : Photos d'installations (not mine which is black veneer but exactly the same model; photo is a capture I did from a french site) Mon Système.. : Photos d'installations : they are a little totemique as well with the passive mid filter in aluminium on front of the cone

 

[ScottG]

Peoples subjective opinions on how a driver sounds are completely pointless and irrelevant.

I'm sure there are more than a few that would find relevance.


All drivers seem to sound a bit different IMO - even when equalized, even at the lower-end of the spectrum. Still, most sound more similar than different given similar parameters and similar loading - especially as you move an octave below the driver's loss in directivity.

I'm like you though, my thought is that the AT is deficient on measured performance considering the price (..in fact I'd expect something near-miraculous for that much). Still, I wouldn't call it a bad driver given the elevated input level with those measurements. The consistency does bother me though - and that's even if it was a relatively inexpensive driver, let alone a driver this costly. Hopefully Gerrit got a better group of drivers.


Still, one of the most impressive designs I've seen in quite a while.


-oh yeah, which drivers would I choose if in this configuration?

TIW 250 XS - 8 Ohm

 

[Eldam]

Oups I saw the PHL I linked have a too much high Fs in the Goritt's Totem dipole configuration : 18 db roll off at 50 hz is a little short as the 4 mm Xmax for bass EQ ! But I liked the 30 g Mms and the coated paper is the same the ancient Audax Aerogel (precise and neutral tones !)

The Visaton Scott linked have a much better Fs ... with the surround you have a quasi H frame .



I never saw any AE speakers in Europe in a webshop !

lok at this one, it's a12" but the spec are... good, and also the voice coil inductance is low (saw elswhere it was an important factor to an easier low end with a dipole ?!) : http://www.beyma.com/getpdf.php?pid=12MC500 : a little more distorsed than the Juhazi's, but close specs ! Ah not thegood look of the AE and the ones of Gerrit, here the Beyma will waste the good looking of the Totem ! At least a too much high FS ! Only good as a upper dipole mid-bass à la Aino Gradient !

 

[WrineX]

So, was it worth the effort? Yes, definitely yes! I’ve been listening to this system for over 6 months now and I haven’t yet detected anything problematic, as far as I’m concerned it is a blameless loudspeaker. The nearly constant horizontal directivity and perfect dipole symmetry (at least above 400Hz) results in an exceptionally focused and stable stereo image. Because the system is so narrow at the top it also does not stand in the way of it’s own back-wave reflection, I think this is very important for a dipole. A wide baffle will cast a shadow so to speak which will make it possible for your auditory system to (more easily) detect its position.
Yes, the system is horribly inefficient but the amplifiers and power supplies are all very efficient so the total power consumption in rest is just above 100W which is not bad for a system with a peak power of well over 3kW. The enormous peak power capability does provides horn like dynamics and ease of presentation. The operating temperature is somewhere between 30 and 40 degrees Celsius depending on output power. The system is very, very quiet, you have to press your ear against the Neo10 to be able to hear a faint noise. No hum, no clicks, no pop or crackle. The system is also free of any mechanical noise (humming or whistling).

So where’s the catch? Well, it won’t do an orchestra at full concert level despite the enormous amount of power available. The maximum SPL I measured on the my listening couch (3m distance, with acceptable distortion) was about 103dB which is more than enough for me and it also is enough for SMPTE RP 200, 83dBSPL average at the listening position with 20dB headroom (83dBSPL = -20dBFS). The limited vertical dispersion requires a minimum listening distance of 3m for proper integration of low,mid and high frequencies and sufficient high frequency dispersion. The system is certainly not child or pet proof and I would expect the WAF to be close to 0. And then there’s the cost, this particular implementation with the AT drivers and Ncore amps is very expensive but even with other amps and drivers this kind of system will never be cheap.


To evaluate the quality of the stereo imaging I came up with the following setup:

View attachment 500316

A little winter audio scene in my backyard. On the left on the table is a mechanical metronome, the little pond has three little waterfalls and what you don’t see is the freeway in the background. The freeway is behind 200m of trees and running parallel to the stereo axis resulting in a diffuse sound ‘carpet’ filling the stereo image. The two cardioid microphones are amplified using a simple Mackie mixer. I tried several methods, the picture shows NOS, and found that X/Y works best with the dipoles. The quality of the reproduction is quite stunning, especially the way the diffuse background noise is rendered. The metronome is rendered with pinpoint accuracy, it sounds as if you could walk over and grab it. The little waterfalls are also very realistic, just ‘there’.

As you might imagine I’m very happy with this system, it does everything that I hoped for and then some. It has definitely convinced me of the importance of constant directivity, and in the case of dipoles of dipole symmetry. The fact that the measurement results are all very good and can all be presented without any smoothing applied also gives me piece of mind, I no longer feel the need to listen for defects in the reproduction, now I just listen to the music.
I hope this short report results in more people paying attention to the directivity of loudspeakers whether it be dipoles, omnipoles, cardioids or waveguides/horns, it really is worth the effort. Maybe the ‘directivity plot’ should be renamed to ‘spatial distortion plot’. Spatial distortion has a nice ring to it and the term more accurately describes what’s going on; irregular directivity will distort the stereo space (image).


regards,

Gerrit

probeer eens wat binauraal opnames. tuurlijk beste op koptelefoon maar ook ziek goed op dipoles. heb er nog wel een aantal mocht je voor de grap eens het verschil willen horen. (misschien al ervaring mee)

 

[NiToNi]

Very nice project - thanks for sharing!

Re CtC on ribbons and planars, somebody said that as opposed to cones, you can measure from the edge rather than the center since these membrane radiate an equal amount of sound from any point of their surface area at all frequencies...

 

[ErikdeBest]

Hi Gerrit,

I do have a pair of the NEO10 and I am working on something similar as you - and I do thank you a lot for the curves!

I do have a question. Can you tell a bit more about the EQ applied to these speakers, specially to the NEO10? A 6dB shelving low pass between 400 and 2khz(?).

many thanks and best regards,
Erik