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DIY ?uestion

Greetings people,
     What are the arguments, pro and con, for transmission line speakers that: have channels with parallel walls, and those that progressively get wider, as in a horn?  I want to do a build with plans that show parallel walls, where I can alter them to create an ever widening channel within the same size container.  I am a newbie in this area of DIY speakers, and am sure there are opposing views.
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audiokinesis
1,872 posts
 

@trelja ,  Thank you very much!!

I would love to see plans for the D and C, and the C's crossover!!

Yeah the series crossover is a strange beast at first glance!  Instead of blocking the lows from reaching the tweeter and the highs from reaching the woofer, the lows go AROUND the tweeter and the highs go AROUND the woofer.  So the specific filtering for each driver is actually in PARALLEL with that driver, but the components are all inter-dependent so it's really all one big filter instead of a highpass filter + a lowpass filter.

My recollection from experimenting with series crossovers many years ago is that you need to start out with drivers that have a smooth response with equal overlap on both sides of the crossover frequency.  I used a Hiquphon tweeter, probably tried several midwoofers but don't remember which ones. I got better results (to my ears) with parallel crossovers using filters that had some electrical asymmetry, so I don't think my midwoofers were a good match for the Hiquphons. I do remember adjusting the L & C ratio but thought that was just varying the amount of ovelap in the crossover region and didn't realize it was varying the slope as well. I didn't have decent measuring equipment back then (in my amateur days).

Some pretty serious EQ is needed for my constant-directivity horns, as without a crossover their response trends roughly -6 dB per octave from about 1.5 kHz on up.  (This is true both on-axis and off-axis, unlike with direct radiators, so when we fix the on-axis response we have also fixed the off-axis response - which imo is a very good thing).  So in this case an electrically asymmetrical crossover is needed to achieve approximate acoustic symmetry, and I don't think that can be done with a series crossover because the filter is one inter-dependent thing instead of being separate lowpass and highpass sections, but I'll take another look.

Did Bud have designs where he went for time coherence (first order crossovers + lining up the arrival times?) 

Can you tell me anything about the Qts range Bud preferred? 

By any chance, will you be at RMAF this year?

Thanks again!

Duke

salectric
683 posts
 
Thank you Trelja and Duke for sharing the TL info and the stories about Bud.  i agree completely with Trelja’s description of the sound of TL bass compared to vented or sealed cabinets.  I also agree with Duke’s description of the dip in response caused by out-of-phase cancellation.  The foam damping inside the TL helps to reduce the severity of the dip but it’s hard to ignore it once heard.

I built a number of TL woofer systems in my younger days including the Fried H.  The most successful was a Fried O cabinet with a KEF B139 woofer and a Fried H satellite on top.  My brother still has this system and it continues to sound very nice some 35 years after I built it.  I also have several lengthy typed letters from Bud responding to my inquiries about his speakers.  He impressed me as a true gentleman.
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