Understanding the Visaton Topas

[Tyimo]

Hi!
I would like to ask the TML experts about the Visaton Topas speaker.

"... The lower 35 Hz limit is remarkably low for a 10 cm woofer. This is achieved by fine-tuning the cabinet in the borderline area between vented bass and transmission line....."

- How could I model/simulate the Visaton Topas speaker with MJK's Mathcad worksheet?
-Could somebody give me explanation how does this box works? (Is it more bassreflex or TML? The vent lenght is included in the TML lenght? How is it tuned? etc. )

Technical Data of the driver:
Rated power: 40 Watt
Maximum power: 60 Watt
Nominal impedance: 8 Ohm
Frequency response (-10 dB): fu - 20000 Hz
(fu: Lower cut-off frequency depending on cabinet) .
Mean sound pressure level: 86 dB (1W/1m)86 dB (1W/1m)
Maximum cone displacement:: 4,5 mm
Resonance frequency fs: 62 Hz
Magnetic induction: 1,2 Tesla
Magnetic flux: 300 µ Weber
Height of front pole-plate: 4 mm
Voice coil diameter: 20 mm
Height of winding: 8,5 mm
Cutout diameter: 101 mm
Net weight: 1,05 kg
D.C. resistance Rdc: 6,0 Ohm
Mechanical Q factor Qms: 7,05
Electrical Q factor Qes: 0,40
Total Q factor Qts: 0,38
Equivalent volume Vas: 6,92 l
Effective piston area Sd: 54 cm2
Dynamically moved mass Mms: 4 g
Force factor Bxl: 4,8 T m
Inductance of the voice coil L: 0,7 mH


Thanks!

Tyimo

[Benny the 2.]

I don't know how to model the Topas with those sheets. But I can tell you, that this speaker is more like a BR- construction.

If you are able to understand just a little bit german, try to have a look at the Visaton board (http://www.visaton.de/vb). If you are willed to register as a member, you may ask your question over there too.

We (I am a member of that board) are very helpfull to write down in english too, although it is mostly german language...

If you decide to build the Topas, you should also ask for informations about "Internal Helmholtz Resonators". Those are recommended, because they help to reduce "standing waves"... (sorry, I don't know the correct word in english...)

Regards, Benny

[Snickers-is]

This is very interesting, but how about the maximum SPL in the bass region?

A BR can easily be calculated by the displacement by the woofer adding upto 6 dB. With a horn the effeciency is calculated by the are of the horn opening. But where will the TL put itself in between?

Or will it be more like a closed box?

Does the shape of it affect the efficiency and response?

[Benny the 2.]

This is very interesting, but how about the maximum SPL in the bass region?

You can't expect a bass orgy from this speaker. Remember, that the only bass is made by the TI 100...
This is a speaker, which is made for "easy listening". Although it really has very good recomendations about the bass region.
I must confess, that I only heard them once...

A BR can easily be calculated by the displacement by the woofer adding upto 6 dB. With a horn the effeciency is calculated by the are of the horn opening. But where will the TL put itself in between?

Please, forget everything about a TL while talking about the Topas...
Yes, I know, Visaton describes these speakers as a "hybrid" of BR and TL, but in fact they are BR with a very special port design.

Or will it be more like a closed box?

Read above...

Does the shape of it affect the efficiency and response?

Sorry, I have no answer...

The Topas is a very neat little speaker, which is able to reproduce music in a very fine way. The heights are crystal clear (MHT 12 is a real HiEnd- speaker) and the bass is truly represented.
Okay, the room gain also plays a great role in this game and you can't expect any wonder from the Topas. But you'll truly be fascinated, if you're into "normal" muic (e. g. no techno, HipHop or Hard Rock).
These speakers have a well- formed virtual "stage", so they are able to sound bigger, as they in fact are.

(No, I'm not getting any money from Visaton to write this. This is the essence of many threads, we had on our board...)

PS: Try to have a look here or here... (sorry, no pics anymore)
PPS: If you are interested in some 3.8 l- bookshelf speakers (the plans, graphs and xover) with MHT 12 and TI 100, feel free to drop me a line...

Regards, Benny

[planet10]

I'd say that box is too tall and narrow to not support a quarter-wave resonance, so it is indeed a TL. It can be modeled using Martin's section model. You have a straight section, followed by a tapered section, then the bend, then the last tapered section. The driver is offset. Have a look at how Martin modeled the bend in his Focal TLs. You may have to do a bit of math (or redraw bits in a CAD program to get the appropriate dimensions at the bend.

It does look like it is probably a way long line for such a driver -- so probably not optimum.

dave

[qwad]

yea , bears a striking resemblance to bob brines peerless pipe design on his home pages no?

[planet10]

Originally posted by qwad
bears a striking resemblance to bob brines peerless pipe design on his home pages no?

The way the terminus is done yes... Bob's are out the back thou -- no reason you couldn't do that here too.

dave

[qwad]

a moot point, but correct nevertheless, though it shouldnt really matter so much in bobs case I think the benefit is the distance from the front so any out of band rear radiation will be attenuated more effectively plus as it would be nearer to a rear wall it would benefit bass more, no? cheers pussycat

[planet10]

Originally posted by qwad
I think the benefit is the distance from the front so any out of band rear radiation will be attenuated more effectively plus as it would be nearer to a rear wall it would benefit bass more, no?

Agreed....

dave

[Tyimo]

Hi!
Thanks a lot for everybody the answers!!!

Benny: I know the Visaton site and plans etc., but I wanted to "design" a box in this way like the Topas. I would not build the original one because the low 80 dB sensitivity and high driver costs! But anyway, thanks for the infos!

Dave: thanks too!!
-another questions: how I have to plan or calculate a port, wich hasn't got paralel sides like the Topas?
-if my port's mouth area is = 1 SD, should I calculate the port lenght inclueded to the total TML wave lenght? For example: 90 cm box lenght + 37 cm port lenght = 127 cm total wave lenght?
Greets:

Tyimo