Martin J King Classic transmission line question

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oon_the_kid

oon_the_kid

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Joined 2008
#1
Hi,

I have a question I was wondering if anybody could help me to answer on classic transmission line based on Martin J King's alignment tables.

In page 4, he described a way to calculate the requirement for S0 which is the size of the entrance to the pipe. What is the consequences of not building it not following the specs published. For example the calculation shows I need a woofer area much bigger than the woofer. What if I just choose an area the same size as the woofer. Would that be a proble.

Thanks.

Oon
 
#3
Well, I would very much to keep my transmission line as small as possible, having a big S0 does not help.

I would also pretty much like to fit it on a PVC pipe which is about the same diameter as the speaker driver. Based on some calculations I tried the S0 can sometimes as much 3 times Sd. So I wanted to see what are the compromises if I don't use such a bug S0.

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#5
I did. And I have seen quite a few designs. And I have tried quite a few simple experiments and the tuning frequency doesn't seem to be affected by Baffle area or pipe diameter. So I wanted to know what does the parameter on front Baffle surface area impact. Maybe Q, or freq response or what else?

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#6
The tuning frequency is determined by the length. Just want to check your terminology, the baffle is the board that the driver is mounted in, not it's diameter, most of the examples I've seen of PVC pipe TL's don't have a baffle as such
 
#7
Yes that is correct and in the alignment table it is the closed side of the pipe. There is a recommended area for the closed side of the pipe based on the example given in his paper and it can sometimes be much bigger than the area of the speaker driver itself.

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#8
Yes, there are other examples of the tapering of the line, and some are not tapered at all. Since you want to proceed with the PVC pipe idea I suggest you focus on that and don't rely too heavily on what is just one of many options
 
#9
Actually this is calculation for a straight line. Not a tapered one. If you look at page 13, under item 3). The area for the closed side of the line needs to 2.872 × the area of the speaker driver. However I suspect most people don't usually do this part of the calculation. Only calculating the length...

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#12
Don't have access to my charts, etc., to post numbers, plot responses, but whether a cab alignment is sealed, BR, TL, horn, it takes 'x' amount of volume [Vb] to make 'y' amounts of bass based on the driver's specs, ergo make it smaller and the bass rolls off at a higher frequency; so make it any size you want/need, but understand that bass output will be less than predicted and the amount of damping to smooth it out will increase, which in turn will roll off even more of the [mid] bass.

Not many 'free lunches' in sound system design.

GM
 
#13
GM said:
Don't have access to my charts, etc., to post numbers, plot responses, but whether a cab alignment is sealed, BR, TL, horn, it takes 'x' amount of volume [Vb] to make 'y' amounts of bass based on the driver's specs, ergo make it smaller and the bass rolls off at a higher frequency; so make it any size you want/need, but understand that bass output will be less than predicted and the amount of damping to smooth it out will increase, which in turn will roll off even more of the [mid] bass.

Not many 'free lunches' in sound system design.

GM
Click to expand...
Hi GM,

I would appreciate it if you could have a look at those charts in your free time. I am sure there would be some impact on the bass performance. I would just like to find out what is the impact and what the compromises to sound quality...

Thanks,

Oon

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#14
Didn't get much answer to this question. Maybe let me try rephrase this so it might be more applicable. Did anyone get much trouble building a transmission line where the crossectional area of the line is comparable or maybe even slightly smaller than the speaker diaphragm area?

Does that cause any unwanted effects?

Thanks again in advance..

Oon
 
#15
I am an old Rule of Thumb TL builder, meaning I was active in the 70s and 80s when the Bailey line was the standard. My version was tapered so SO was 2x SD, which is a minimum CSA to house an ordinary driver, reducing to 1/2 SD at the terminus. In those days it was believed that internal damping lowered the tuning of the pipe but now the taper, or a smaller vent at the end of the line, is what does the trick. So I was building a 1:1 line. A LOT has been learned since then.
These days I have resorted to EQ and closed box since xmax has quadrupled along with cheap power.
Gotten lazy in my old age...
 
#18
oon_the_kid said:
Hi GM,

I would appreciate it if you could have a look at those charts in your free time. I am sure there would be some impact on the bass performance. I would just like to find out what is the impact and what the compromises to sound quality...

Thanks,

Oon

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Click to expand...

Greets!

???

You will have to sim them in Hornresp or Leonard Audio's software. Sound quality [SQ] per se isn't affected, just less [mid] bass.

GM
 
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