12" tannoy paper coax and box type. Karlsonator or...?.

[freddi]

MMJ has been developing a "Karlflex" around a 12" speaker (with lower Q than those Tannoy) and has made observations with akabak

http://www.diyaudio.com/forums/subw...-simple-build-series-tuned-6th-order-133.html

hey GregB - re:X15 - for a 12" seems that might work better if squashed from the sides back to K12 width while retaining roughly 2 cubic feet rear chamber , 1 cubic foot front chamber. Simplify the reflector.

 

[xrk971]

As soon as I get some time on Akabak computer I will try to model a K with this Tannoy. Give me a few days.

 

[xrk971]

Sim of Tannoy 12 in Karlsonator

Based on the following T/S parameters that I got for this driver:

| Tannoy 12 in paper cone with Qts=0.50 
  Sd=531.0cm2 
  fs=57Hz
  Mms=75.0g
  Qms=8.065
  Qes=0.573 
  Re=5.128ohm 
  Le=0.38mH 
  Vas=36.8L

The optimal size of the Karlsonator is close to a standard 12in Karlsonator per GregB's design. In fact, you could use it as drawn and it would work very nicely with about 44Hz f3. However, if you want a little more bass extension and a flatter response, scale the height by 13/12x (taller) and the width by 11/12x (narrower) and you will get this for SPL vs frequency - good for about 95dB sensitivity with an f3 of 41Hz:

Here is predicted cone displacement - nice how it is well controlled and no runaway excursion:

Here is predicted impedance:

I hope this helps and you make it.

 

[noviygera]

below was posted to wrong thread

(this is a re-post of an incorrectly placed post in response to original thread)

Xrk971,

thank you! I assume this is the link to Karsonator you're referring to.

questions: What causes the freq response squiggle around 150hz? Is there a way to flatten it and is a problem?
Does the karlson opening of the front chamber work as a hybrid of horn and ported box?

I will probably go with original plan and not make taller/narrower box unless it will help to remove that squiggle around 150hz.

regards,
Herman

 

[freddi]

I'd also like to hear from X on vent cancellation effects in Karlson and Karlsonator

a big vent reflex can have a dip too

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

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

 

[xrk971]

The reality of the cancellation dip may be different and in general not as deep as the simulation. The sim is a 1 dimensional lumped element model. The front chamber and aperture will have 3d effects. It will need to be modeled with ABEC3 or Comsol Multiphysics to capture that properly. The bass extension and level though is pretty accurate. To get 95dB at 2.83v and 45Hz means no BSC is needed with this design. That is a very sensitive bass generator.

 

[Bare]

Sooo that's all based on an sketchy TS measure of QTS of 0.5
Odd that given that Most All Tannoy Dc's QTs. are in the 0.2 ~ 0.28 area.
Either those are really poor DC versions or the info is Wrong.
Pick one.

 

[xrk971]

Sooo that's all based on an sketchy TS measure of QTS of 0.5
Odd that given that Most All Tannoy Dc's QTs. are in the 0.2 ~ 0.28 area.
Either those are really poor DC versions or the info is Wrong.
Pick one.

You forget the third and most likely option is that the Qts is indeed 0.5 as measured with the Dayton Woofer Tester in earlier post. The impedance plot is shown clearly there - it's obvious that the peak is not broad. Just because Qts value changes doesn't mean it's wrong based on what manufacturer specs say. Magnets get old, Qts goes up.

 

[freddi]

what was the original free air resonance spec for that Tannoy? (his are around 60) -I've had too many old speakers stiffen, raising fs and qts

 

[planet10]

Sooo that's all based on an sketchy TS measure of QTS of 0.5
Odd that given that Most All Tannoy Dc's QTs. are in the 0.2 ~ 0.28 area.

You forget the third and most likely option is that the Qts is indeed 0.5 as measured with the Dayton Woofer Tester in earlier post.

It is more likely that XRKs budget T/S measurement kit is taking the numbers from a different part of the curve than the factory does (a very typical situation). One has to remember that T/S are not scalars but curves.

It is also possible that the Qt is really that high because alnico ages. As the magnet strength decreases the Q goes up.

That said the 50+ year old 12" DC golds (the only DC Tannoy i have measured) came out with a Qt = 0.21 (using S+L Woofer Tester 2).

The box we built turned out pretty well using those numbers.

I personally would never use a Dayton Woofer Testers numbers to design a loudspeaker enclosure.

dave

 

[noviygera]

Tannoy T/S parameters were also measured here and Qt is 0.538

image_zpse645eceb.jpg Photo by dan_clements1 | Photobucket

 

[planet10]

Tannoy does not publish T/S data, but do specifiy an 84 litre vented box that reachs 60 Hz F3, 50 Hz F10.

http://www.audiologic.uk/product_extra_files/cms12tdc.pdf

dave

 

[noviygera]

Yes, this is the exact driver I am using. And it sound quite promising on an open baffle.

 

[Bare]

It is more likely that XRKs budget T/S measurement kit is taking the numbers from a different part of the curve than the factory does (a very typical situation). One has to remember that T/S are not scalars but curves.

It is also possible that the Qt is really that high because alnico ages. As the magnet strength decreases the Q goes up.

That said the 50+ year old 12" DC golds (the only DC Tannoy i have measured) came out with a Qt = 0.21 (using S+L Woofer Tester 2).

The box we built turned out pretty well using those numbers.

I personally would never use a Dayton Woofer Testers numbers to design a loudspeaker enclosure.

dave

Few points:
Alnico does NOT age /lose Flux.. period.
Surprised by that statement tho..for shame, mate
Do yer own research but it's True.
Also this is NOT an Alnico driver just some low cost Ferrite motored Gizmo (Note tho, that Ferrite Measurably loses Flux over time ..10 years and it's quantifiable) destined for background noises (ceiling fer Gawd's sake) use.
Not to say that ferrite motored Tannoy DC's are not good.
Most are breathtaking when well mounted and powered.
But NOT this one.. it was never intended to be.
Buy Cheap.. Buy twice.
Agreed tho.. TS specs are Sketchy.. at best.
Boxes really ONLY affect Tannoy DC's (likely a helluvalot of other Drivers too.. but that's a Digression) At below 200hz, arguably 100hz

Other small point is:
Why would one even consider fitting a DC to a Karlson type Box.. for Mechanical frequency control?? Really !!?
When A DC has exquisite Designed in Control... even with a cost constrained one.

Open Baffle ? This just gets better and better. No thrift shop in your Neighborhood?

 

[planet10]

Alnico does NOT age /lose Flux..

As long as you don't get it too hot, bang it too much, or store near other magnets.

Companies offer services to remag alnico that has lost magnetic strength -- i have had quite a few alnico magnets that were quite severely degraded.

Also this is NOT an Alnico driver just some low cost Ferrite motored destined to be/for background (ceiling) uses.

True, at the time of my comment i did not realize that.

dave

 

[Bare]

Yesss We've ALL heard the Nonsense.
But Most of it is Urban Myth.
More than enough info about to quickly refute it though.. Google does have uses.
Yess Early Altecs and JBL's did occaisionally suffer Magnet degradation. But those were often Teeny Slugs in a Metal Frame assemblies. A few High grade drivers were more generously equipped.. these are Highly Prized nowadays for reason.
Alnico wasn't free so the Minimum Metal possible was used... a few did get damaged but not as many as Folklore suggests. Check with Great Plains Audio
A Tannoy used ~15 Lb Castings. NOT easily Messed.. at least by Amp power.
Which would vaporise the VC ..Loooong before affecting Mag Flux in any meaninginful / permanent way
Lotsa firms "sell' remags ..needed or not.. but then lotsa firms sell Penis enlargement creams as well
Neither makes it necessary or even clever.
Caveat emptor in spades.
Yess a Hammer, repeatedly applied with brute force and ignorance.. can.. mess Cobalt mag 'domains'.. wouldn't do much good for the driver either.. at which point mag flux loss would be 'irrelevant'.. dontcha think??

 

[xrk971]

Alnico does NOT age /lose Flux.. period.

This is an incorrect statement. Alnico is an older low coercivity magnet and can lose magnetism by being placed too close to an opposing field, being exposed to mechanical shock or heat.

Newer rare earth ceramic high coercivity magnets like NdFeB ("Neo") are much more powerful and don't lose their strength as easily. Heat can still destroy them but not being near other magnets.

 

[xrk971]

I personally would never use a Dayton Woofer Testers numbers to design a loudspeaker enclosure.

Just you. Thousands of others use WT3 and DATS and design speakers with their measurements just fine. DATS works fine for me and for many other people I know.

 

[noviygera]

I did not give up

Just a quick update. One mock up box made per plans. Sounds promising. Next step is to do proper bracing and damping.

 

[freddi]

very nice looking - I only had damping in the stub and floor -a bit more might be good. What's the wing thickness? - I've watched pretty well braced Baltic birch wings deflect on K's and klam but the Ks didn't have the vent area of a Karlsonator - some struts should help on the mockup. What kind of plywood is that?