Kappelmeister speakers - Transmission Line

Hi..

Anyone had experience in building these speakers? Have redesigned it and would very much like to know about the theory of using the distance between the open port and the driver as part of the length of the transmission line.

Need to get this right before building the cabs, it SOUNDS like it is a valid principle, but if not, will be wasting a lot of time and materials..

Are there no transmission line fans out there? The Kappelmeister design states that the length of the transmission line should also include the distance from port to driver, but I have contacted several others about this and opinion seems to be divided 50/50..

Anyone curious or not heard about the Kappelmeister, it is a full range driver based transmission line enclosure, have built a pair for a friend several years ago and they sounded amazing, really stunning considering the total cost, including drivers was £56!

I have been tweaking the design for years and am now ready to build my own pair.. Happy to share the redesign if anyone is interested.

Steve...

 

I've made several transmission lines.....using the booklet by larry d sharp

I assume your doing a straight kappelmeister rather than a tappered pipe ?

your trying to get a 3/4 wavelength from driver to port using the stuffing density to effective length the short pipe, to get the correct phase at the port. With the correct phase the driver output is reinforced by the port output ie in phase.

When you measure the TL length you need to measure from the centre of the drive unit to the centre of the port.

from v capels book I make that a length of 93 inches [7.75'] approx....

I'm assuming that the driver is going to have a resonant freq about 50 hz an unstuffed pipe would need to be pipe would need to be 203 inches long....hence the need for the extensive stuffing. most authorities suggest a figure of 0.5 lbs /cub ft. The TL pipe having a volume of about 1 cu ft [ 21 x 93]/1728 = 1.1 [1728 cu inches in a cubic foot]...actually half a pound of stuffing is quite large ....capel himself suggests that stuffing need to be enthusiastic reading between the lines especially round the bends.....the down side is that you reduce the effecience...and output at the port.

Getting back to your original question ....you say you've modded the design and with out that info I can help you further.

if you want to chat over the design pm me

 

Hi Zanash...

Thanks for the reply, I am aware of the issue with stuffing the pipe, especially at the various harmonic points... If you are certain about the pipe length NOT including the distance between port, I would take your word for it. V Capel insists that it is as this distance is very much an issue with placing the driver and port in phase...
Have done a loose design in acad, could email the file to you if you are able to read it, or could convert it to pdf if that is better..

Steve

 

Hi Tenson..

This is the original design of the Kappelmeister.. Some fundamental flaws that I have corrected are the reflection caused by the back of the driver being so close to the face of a panel, also the port is at the bottom and to the rear which lets the floor absorb too much of the emitted sound wave.

V. Capel, the original designer of this enclosure states that the transmission line should also include the distance, in a straight line, from the port to the driver. In his design, this meant about 3 feet, which meant the pipe itself would be 3 feet less in length than the calculation for 1/4 wavelength would suggest.

As I had mentioned, I have built these speakers before for a friend. I was, at the time, spending a small fortune on Audio Note equipment for myself and saw this as a little 'low tech' project. Really was amazed that they sounded better than my own speakers, especially as the drivers were TV speakers!!

Have now redesigned the enclosures to incorporate Fostex FE 207e full range drivers and have been dying to get this project under way.. Have an Acad to pdf converter but it does not seem to work! Will try some other software to see if I can post the redesign..

Steve..

 

Sorry Tenson..

I seem to have exceeded my limit for pictures and cant get the Kappelmeister design onto this posting! If you have email address will happily send it to you.. Mine is [email protected]

 

tenson has asked the same question that I was going to .....

so you have created an enclosure for the driver rather than it sat in the side of the pipe ?

you still need to know the distance the sound has to travel .....and how that equates to the acoustic distance ....

if you have done the above ...you will have a throat the length of the pipe is measure between throat and port. Thats the start of the port if its a tube. If its a hole in the baffle then its the centre point.

Effectively rotating the vent from the base to the back should not have any effect on the length measurement .....

I agree that full range speakers can sound very good ...just goes to show what the cross over takes away.

 

steve sent me the plans of the speaker ....

the main driver fires back ward into the pipe that then folds down the back of the cabinet then works its way forward and up then down under the driver to vent at the front bottom ...pic speaks a thousand words.

the design seems fine ....I'd have contoured the 180 and 90 deg turns to curves rather than reflections but hay what do I know.

 

Hi Zanash..

Thanks for the time you have spent on this for me, I am convinced now NOT to include the distance between port and driver in the transmission line length. Can now complete my calculations and get on with it!

Would like to add a comment about the right angle and u-bends in the transmission line. I have chosen glazed tiles set at 45 degrees that are backed by concrete as the most effective way of bouncing the audio around the bends. Concrete is 10 times more effective as wood at doing this, the glazed tiles increase this effectiveness (heard the sound bounce around in a swimming pool?), also they add a nice bit of weight to the enclosures.

Long time ago, heard a pair of speakers entirely made out of concrete... Fabulous sound, not so easy to lug around tho..!

Steve..

 

the trouble is .....

thats what you don't want to do in my opinion !

you want a smooth propogation of the wave down the column..with it transiting corners without phase changes due to reflextions ...its not a reflex speaker or infinite baffle where the sound has to rattle round the internal dimensions to dissipate ...profiles and bends are easy enough to make

just my two pence worth !

apart from that disparity everything seems fine

 

yes ...but why not get as right as you can to start with ...the other thing that occured to me was that a throat could be made behind the driver ...this would effectively collect the driver output and then fire it down the line [not a description of what actually happens] from a clean appature ..

are we trying to get a standing wave in the pipe or radiate from the port or even both .....brain seems to have packed up this morning !

 

Building the Kapellmeisters is covered in detail in the book An Introduction to Loudspeakers and Enclosure Design by V Capel - ISBN 0859342018.

I bought a copy of this book years ago from Maplins for £3.99. I think it's now out of print, I've seen secondhand copies going on eBay.

 

That could have been written by me! Have had the book since 1994 and built a pair of Kappelmeisters exactly to the books design, including the Altai TV speaker drivers.. Was utterly gob smacked at the sound as was everyone else that heard them, unfortunately I had built them for someone else..
This time round I am using a vastly upgraded full range driver (Fostex 207e) and has tweaked the enclosure to get around a few design flaws...
Just waiting for the MDF to be delivered...

Steve..

 

and mine has a price of £2.95 and a reprint date of '94..

But as you would have seen if you had read the thread ...steve is not building a stock set neither in design nor the drivers. So really this should be considered a new design and should to save any obvious further confusion be called by a different name ...

As kappel is....

a municipality in the district of Olten in the canton of Solothurn in Switzerland.

perhaps we could call it

hölzernerkastenmeister thats woodchester in German with a liberty

or jagdmeister for hunt master

or leidmeister for song master ....

you can have great fun with babel fish

 

Or how about 'The World's Best Loudspeaker'?