Transmission Line with Kappa Perfect??

[haraldo]

Whether you go sealed or ported depends on the parameters of the driver you are working with. A sealed enclosure will have an F3 somewhat above Fs, but roll off will be 12db per octave. However with sealed to get good output at 20 Hz some Eq is going to be required, and that raises the specter of thermal compression.

The ported enclosure can have F3 very close to Fs. I agree there will be some phase and time delay problems below Fb, but I think these are not highly objectionable. You can tune a ported enclosure so the bass does not splash all over the place. The other problem with ported enclosures is that the driver rapidly decouples below F3 so you can easily bottom the driver without a subsonic filter. So it is swings and roundabouts.

I personally favor the TL for the most natural bass, however TLs with F3 down in the low 20 Hz range occupy significant real estate. The support is broad however, and roll of 12 db per octave. I have found that TLs with F3 in the neighborhood of 25 Hz really give you bass you can feel without advertising it, and touch lightly until there is serious program in that range.
Once people experience bass from a TL they seldom go back to anything else. Dual lines tuned 1/2 octave apart give nice smooth natural bass over 2 1/2 octaves. I'm not sure why, but they just don't boom at all. It is smooth deep even and effortless. So many of my friends notice that.

Nowhere in the formula for deriving F3 is the diameter of the driver relevant directly. However larger cones tend to be heavier, so you have a heavier weight on the spring so to speak. However you can make the spring less stiff and accomplish the same thing. The vintage JW driver, had a four inch tractrix aluminum cone that weighed only six grams. The suspension was unique in that the cone and voice coil were suspended under slung on three long beryllium cantilevers. This JW module was capable of quite astonishing bass reach.

Anybody done TL sub designs with Kappa Perfect drivers?

 

[TLS Guy]

Anybody done TL sub designs with Kappa Perfect drivers?[/QUOTE

I'm working on one right now. When the busy fall work is over I will finalize it. I can tell you it takes two drivers per sub, because of pipe length it is only way you can align the driver VAS with Vp.

 

[haraldo]

Can't wait to hear more about this, sounds pretty interesting... that's an understatement....

 

[haraldo]

Do you have any (preliminary) design info on these?

 

[TLS Guy]

Do you have any (preliminary) design info on these?

Yes I do. The info is at Benedict. I'm at our Eagan home today preparing to fly to Orlando today. I have the design parameters, but I have done no constructional details. I can tell you Lp, Vp, Fp, F3 taper, stuffing density and the two driver positions when I get back. I can also give you the internal dimensions of the enclosure. The details of this are not on my computer, as the types of aperiodic lines I favor, you have to work out the old fashioned way.

I can tell you the enclosure is large and would have to work as a piece of furniture. It certainly would be doable however, as lines are long and relatively slim. The are not cuboid structures!

If I forget, remind me next week.

 

[haraldo]

Hey, just checked your rig again, you really like those Seas Excel drivers, are they really that good? How do you manage with the really adverse cone breakup of the magnesium cones?

 

[TLS Guy]

Hey, just checked your rig again, you really like those Seas Excel drivers, are they really that good? How do you manage with the really adverse cone breakup of the magnesium cones?

Hi Heraldo. Just arrived in Orlando.

Yes, those magnesium alloy cones, like all rigid cones have a sharp break up mode to say the least of it. The bass drivers operate too low to excite the break up mode. However the mids have a nasty break up mode at 4 KHz, that has to be notched out in the crossover.

Rigid cones are in, however I'm for ever skeptical it is the right approach.

I think Ted Jordan has it right, in that you have to design for controlled decoupling of the cone with increasing frequency. I was heavily involved with the Jordan Watts driver and was to a large degree responsible for the MK 3. They are full range drivers and sound wonderful, with surprising bass. However they are power limited.

I'm very pleased with the SEAS EXCEL drivers, and can make them perform very well.

 

[TLS Guy]

Do you have any (preliminary) design info on these?

Ok Haraldo, here is the info you asked for: -

A TL of the after the configuration of Bailey, Fried and Wright, would require two Kappa perfect VQ drivers with mid Q insert. The total volume of the pipe Vp would need to be 6.5 cubic feet, with a line length, Lpt, of 11 3/4 feet. There would need to be a 3:1 reverse taper, with the closed end having the highest cross sectional area. The point where the two driver chassis abut should be four feet from the closed end. The polyfill packing density should be around 0.8 lb/cu.ft.

That would give an F3 of 25 Hz. However the system is non resonant and rolls off 12 db/octave rather than 24db per octave so there would be more low bass. The cones would be supported up 75 Hz by the port rather than the narrow range of the port of a reflex enclosure.

Now the packing density needs to be checked by the impedance curve. You need to pack to the point where you get one impedance hump not two, so it looks like the curve of a sealed enclosure. Then you know the system is truly non resonant.

This gives you the idea of the configuration of a reverse tapered line with off set drivers.

Now you can brace a TL with vertical braces along the line of the pipe, but you can not brace across the pipe. Don't chop the pipe up too much, that will also stop the pipe working. Despite the stuffing there is considerable air flow at the port. Since there is an anti node of air displacement at the port, I usually end the fill three to four inches above the port, and never have fill protrude from the port. Here is a photo showing a longitudinal brace.

If you want you can put some Rockwool right behind the drivers, but don't use too much or you will kill the pipe. Just use enough to absorb the back wave.

The enclosure I'm working up has internal dimensions of 80.5 X 20.75 X 14 inches. External dimensions 83.5 X 23.75 X 17 inches.

So the unit needs to be a coffee table, or a structure similar to the one I have below my TV already, although this is not an enclosure.

I'm thinking of doing it that way in my Eagan town home.

 

[haraldo]

Thank you very much for such a comprehensive description of this project, and to be honest I find this very interesting indeed , there's just a few things I wonder about.

• How to get to the correct density if you don't have instrumentation to measure impedance curve, or is there no way around this?

• I'm a bit bothered by the fact that it's not possible to have any kind of braces across the TL, how do you make sure the cabinet is not too live?
  wouldn't this easily represent an issue if X-over is anything but very very low?

These are really really big sub's, especially if a stereo set of sub's is needed

-H

 

[TLS Guy]

Thank you very much for such a comprehensive description of this project, and to be honest I find this very interesting indeed , there's just a few things I wonder about.

• How to get to the correct density if you don't have instrumentation to measure impedance curve, or is there no way around this?

• I'm a bit bothered by the fact that it's not possible to have any kind of braces across the TL, how do you make sure the cabinet is not too live?
  wouldn't this easily represent an issue if X-over is anything but very very low?

These are really really big sub's, especially if a stereo set of sub's is needed

-H

Yes they are big subs! However a kappa 12 VQ needs over 3 cu.ft. So an enclosure with two drivers at around 6 cu.ft. is not that out of line.

I think one sub would be plenty. I have spent a lot of time over the years with pipe organ builders. Pipe organ builders are aware of a phenomenon they call encircling. Now organ builders are not usually steeped in science, they learn form the generation that went before, and have a body of experience.

What they mean by encircling is the ability of pipes to fill a space uniformly, so that the sound pressure level does not decrease by the square of the distance from the source.

An electric organ with speakers is loud up close, but it rapidly gets quieter as you move back down the church. A pipe organ conversely pretty much uniformly fills the space. I think this is an area requiring more study. Any how I notice the same phenomenon with TLs.

Now the speakers in this sub will be a significant distance from the port, making two points of bass radiation. I would predict it will fill even a large room very uniformly. The two drivers paralleled will raise sensitivity 6db, and the line output will boost output at least 4 db from 25 to 75 Hz, for a total gain of 10db over one driver, in reflex or sealed enclosure. I find my bass amps never break a sweat.

Now if the line is stuffed properly the system Qt will be around 0.55. So the system will be critically damped. The bass is therefore very tight and does not boom or splash all over the place.

As far as bracing, I and others have not found it a problem. Remember the internal panels themselves provide a lot of bracing. The pressure is only high at the closed end, where there is an anti node of pressure and an node of displacement. At the open end it is reversed. So there is progressive loss of pressure change as you move down the pipe. In reflex and sealed enclosures, high pressure swings are uniform through out the enclosure.

As far as measuring impedance, if you don't have sophisticated equipment, you can put a resistor in series with the speaker, and measure the voltage across the resistor, then you can work out voltage and current at the speaker and therefore impedance. You can use a test tone disc if you don't have an oscillator. You need to keep the drive voltage from the amp constant. That way you can plot the impedance curve of the speaker.

 

[haraldo]

Looking at all the different designs based on Kappa Perfect drivers around here, I wonder why any sane person would want to go for a retail product....

My issue now.... I have a set of speakers that I use every now and then, an old pair of Duntech PCL 15's... some of the ugliest speakers out there, they are horribly inefficient, there's absolutely no bass, and they cannot play loud, not much output below 70Hz, sound like crap if they get too much bass power... but their sound and the way they present the music is absolutely truly magical

They are screaming for sub's to relieve them from the bass... These speakers probably need X-over around 100Hz And that probably also means stereo sub's because of this very high x-over
Do you believe these subs can be crossed as high as this? Or I have even considered to make an additional set of bass drivers to fit in between the sub's and the PCL-15's because of their poor bass capabilities.

In general, however I'm using a pair of Meadowlark Kestrel2 T-Lines that go much much lower..... and I'm having no issues with power and dynamics, they seem to be happier the louder I play

I thought for a long time doing one of these Kappa perfect designs, but I'm still in the process of a full 100% rehabilitation of a house, and right now there's just too much DIY...

And honestly, I don't think, when it comes to bass, that there's anything that can match a genuinely properly designed T-Line. So this is a very interesting design

It will be very interesting indeed to hear from you when you have this thing playing
Guess it will be hard to find something that can match this sub, even at exceedingly high price levels?
Considering comparisons with retail products, where do you think these subwoofers will fit in, say compared to Velodyne DD15, DD18 or others......?

-Harald

 

[TLS Guy]

Looking at all the different designs based on Kappa Perfect drivers around here, I wonder why any sane person would want to go for a retail product....

My issue now.... I have a set of speakers that I use every now and then, an old pair of Duntech PCL 15's... some of the ugliest speakers out there, they are horribly inefficient, there's absolutely no bass, and they cannot play loud, not much output below 70Hz, sound like crap if they get too much bass power... but their sound and the way they present the music is absolutely truly magical

They are screaming for sub's to relieve them from the bass... These speakers probably need X-over around 100Hz And that probably also means stereo sub's because of this very high x-over
Do you believe these subs can be crossed as high as this? Or I have even considered to make an additional set of bass drivers to fit in between the sub's and the PCL-15's because of their poor bass capabilities.

In general, however I'm using a pair of Meadowlark Kestrel2 T-Lines that go much much lower..... and I'm having no issues with power and dynamics, they seem to be happier the louder I play

I thought for a long time doing one of these Kappa perfect designs, but I'm still in the process of a full 100% rehabilitation of a house, and right now there's just too much DIY...

And honestly, I don't think, when it comes to bass, that there's anything that can match a genuinely properly designed T-Line. So this is a very interesting design

It will be very interesting indeed to hear from you when you have this thing playing
Guess it will be hard to find something that can match this sub, even at exceedingly high price levels?
Considering comparisons with retail products, where do you think these subwoofers will fit in, say compared to Velodyne DD15, DD18 or others......?

-Harald

Sorry I nearly forgot to reply two you. I think you could crossover at 100 Hz. There are no port resonance issues with a TL.

I agree the bass from a good TL is special. As far as comparing it to a commercial product that is difficult. All I know is that when I hear commercial products, they are not even close to the realism of the bottom end of my units. I'm yet to hear one I would swap.

I don't know when I will start this project. The economy is uncertain at the moment, and now I'm on fixed income, I don't want to have to dip into long term savings for this project here. However I would like to get stated sometime this winter.

What I would really like to do, is get the funds together to design center and mains using ICE amp class D modules with active crossovers in the speakers. That seems like an interesting worthwhile project. The Kappa TL sub would be the bottom end. This would be a significant R & D project first.

 

[haraldo]

I don't know when I will start this project. The economy is uncertain at the moment, and now I'm on fixed income, I don't want to have to dip into long term savings for this project here. However I would like to get stated sometime this winter.

What I would really like to do, is get the funds together to design center and mains using ICE amp class D modules with active crossovers in the speakers. That seems like an interesting worthwhile project. The Kappa TL sub would be the bottom end. This would be a significant R & D project first.

Thx )))

Ever thought about Hypex Class D modules, Channel Islands Audio uses Hypex modues in their class D designs, claims are they are better than ICE, I don't know about that.... but there are many commercial products based on this technology.

Claims is that the response of the inherent low-pass filter is not dependent on load, something that's certainly the case with ICE technology.... at least something to consider for tweeter amps....

What I know is that hypex sell modules at prices that don't look too bad, specced up to 700W @ 4 ohm

http://www.hypex.nl/main.htm

http://www.hypex.nl/technology.htm

 

[haraldo]

So I just checked prices on the hypex webshop, and ex freight... of course
Prices from dutch factory direct webshop

Excuse the poor formatting, found no easy way to make a table of this

Hypex 180Watt High Grade Class D Amp
UcD180HG - 105 € - $139
UcD Supply HG Mono - 100 € - $133
Transformer TR400 - 50 € - $66
Total - 255 € - $338

Hypex 400Watt High Grade Class D Amp
UcD400HG - 150 € - $199
UcD Supply HG Mono - 100 € - $133
Transformer TR400 - 70 € - $93
Total - 320 € - $425

Hypex 700Watt High Grade Class D Amp
UcD700HG with HxR - 320 € - $425
UcD700 Power Supply - 225 € - $299
Transformer TR700 - 95 € - $126
Total - 640 € - $849

some connectors, cables and cabinet extra of course

They provide different versions of amplifier modules and power supplies, all of these are the highest quality available that they have

Quite interesting compared to price profiles of retail Class D amplifiers...

-H

 

[TLS Guy]

So I just checked prices on the hypex webshop, and ex freight... of course
Prices from dutch factory direct webshop

Excuse the poor formatting, found no easy way to make a table of this

Hypex 180Watt High Grade Class D Amp
UcD180HG - 105 € - $139
UcD Supply HG Mono - 100 € - $133
Transformer TR400 - 50 € - $66
Total - 255 € - $338

Hypex 400Watt High Grade Class D Amp
UcD400HG - 150 € - $199
UcD Supply HG Mono - 100 € - $133
Transformer TR400 - 70 € - $93
Total - 320 € - $425

Hypex 700Watt High Grade Class D Amp
UcD700HG with HxR - 320 € - $425
UcD700 Power Supply - 225 € - $299
Transformer TR700 - 95 € - $126
Total - 640 € - $849

some connectors, cables and cabinet extra of course

They provide different versions of amplifier modules and power supplies, all of these are the highest quality available that they have

Quite interesting compared to price profiles of retail Class D amplifiers...

-H

Yes, Hypex are high on the list for consideration, as are Tripath.

Hypex appear to be the most favored for powering studio monitors, and are most favpred by the DIY community.

 

[haraldo]

Yes, Hypex are high on the list for consideration, as are Tripath.

Hypex appear to be the most favored for powering studio monitors, and are most favpred by the DIY community.

So what are the criteria you look for in the Class D amps?

 

[TLS Guy]

So what are the criteria you look for in the Class D amps?

Well for most purposes, satisfactory performance over a reasonable impedance range. The next criteria, is freedom from power line RF modulation. Most use switching computer power supplies.

Having them cheap and small is also an attraction.

For use in a speaker with usually an amp per driver, as long as the amp is comfortable with the load of the driver it is powering that is satisfactory.

I think you could make good cheap amps round the Sanyo IC class D amps, with low part count. These chip sets are very cheap.

Making good passive crossovers is now very expensive. I think making better speakers with active crossovers, and class D amps using the Sanyo class D ICE amp chip sets would be very competitive price wise. I think it would be a much better product.

I think the biggest sales resistance will be the fact that so many customers have buried standard loudspeaker cables in their walls, and never took the trouble to run them in conduit.

 

[haraldo]

I'd really like to try a Lyngdorf Milennium Mk IV at home
Incredibly expensive!!! and well, outragous design in many ways, but way way way cool amplifier, and if it performs as well as it looks (but I want it in black!)

a S/N ratio of 113dB, and a volume control that's not in the signal path, many things different from the mainstream, but I think it works.....

Never listened to Milennium, but auditioned Lyngdorf TDAI 2200 with B&W 802d, and that's the only time I ever enjoyed listening to B&W ever

 

[Guiria]

Not to derail your amp discussion but what type of power requirements are needed for a TL such as the Kappa TL design you discuss in this thread? I would assume the efficiency of such a design is similar to ported and you would not need tons of power to drive the Kappa's.

Yeah, 300th post!

 

[haraldo]

Not to derail your amp discussion but what type of power requirements are needed for a TL such as the Kappa TL design you discuss in this thread? I would assume the efficiency of such a design is similar to ported and you would not need tons of power to drive the Kappa's.

Yeah, 300th post!

If you look to the DIY sections of this forum there's also a whole bunch of interesting threads on kappa Perfect builds, Avaserfi has provided also a lot of info on some designs, he recommends the Behringer EP 2500 Poweramp which is sth like 2 * 1200 watt, and well you can also bridge these amps (to 2400 W @ 4 ohm)

http://www.behringer.com/EP2500/index.cfm?lang=ENG

and the amplifier is not so expensive too

Looks like these drivers are so tough that they can take whatever you put into them. I'm not sure how the TL loading changes this but it looks like its literally impossible to overload these drivers.

I'm not sure what TLS Guy thinks on powering of these sub's but I'm sure you will hear about this too.....

Other members in this forum suggests that properly designed subwoofers based on Kappa Perfect 12VQ will match, or even better any commercial designs in the market, at any price.....