# Dipole/Bipole Transmission Line



## villain3g

I've got four Dayton RS 100-4's. I want to use them in a pair of bipole/dipole transmission lines tuned to 80hz. Im also going to attempt to laminate plywood to achieve a curved line. I have some questions: 

Can two drivers occupy the same t-line? 

Should they be wired bipole, dipole, or switchable? 

Does the second driver's Sd affect the line length or cross section area?

Would curving the line be superior to the traditional folded line? 

Attached is an un-proportional sketch... In the picture you can see a brace incorporated into one of the laminates to lock in the drivers.

I'm still in the brainstorming stage, any input is appreciated. The goal is to have them done by Christmas... We'll see

Specifications: * Power handling: 30 watts RMS/45 watts max * VCdia: 1" * Le: .67 mH * Impedance: 4 ohms * Re: 3.0 ohms * Frequency range: 80-20,000 Hz * Fs: 80 Hz * SPL: 87.2 dB 2.83V/1m, 84.2 dB 1W/1m * Vas: .07 cu. ft. * Qms: 3.10 * Qes: .57 * Qts: .48 * Xmax: 4mm * Sd: 37.4 cm2


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## Anthony

Sadly, I am not even close to a transmission line expert. But as a woodworker, I am really intrigued by this idea. I hope you get some design answers, because I'd really like to see pics of these completed! 

The only place I know of that has transmission line info is quarter-wave.com


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## villain3g

yea, I've checked out quarter-wave and also Frugal-horn.com. Laminating the plywood will enable me to construct a very thick and dead enclosure. But, its really the concept of eliminating the crossover that is most appealing to me.


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## Lobotomy^

Interesting concept. You are second one I come across planning on to do speaker cabinets from laminated plywood. Me being the first. :whistling: I will follow you progress.

I'm trying to build Nosov's Ortho cabinets for my small full range elements. Still working on it. At the moment I'm trying to figure out how to make reliable gluing between plywood and acryl sides. Unfortunately only information I have on cabinet is from this finnish site.









More pictures in my gallery at DVD-plaza (finnish forum) I hope it motivates you to continue on your project.


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## Anthony

My first thought would be clear epoxy and metal pins. The pins would do most of the work and the epoxy would seal it without gunking things up.


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## villain3g

interesting interpretation. Maybe I described it wrong. The plan is to cut out six patterns of the shape in the picture and stack each 3/4" plywood shapes side-by-side.


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## Lobotomy^

Misunderstanding might be my bad. Anyways, nice curved transmission lines or horns can be made like I do mines. Making bending mold is only hard thing.

PS. I might try metal pins along with epoxy. First thing that came to my mind too. One friend just insists that epoxy won't stick to acryl. He couldn't give any reason for that, though.


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## Chester

if you have two speakers in different points in the transmission line 'line', I would presume you could model the speaker as 3 individual transmission lines, or maybe 2 transmission lines and a passive radiator, so there would be the interaction between the speaker at the 'typical transmission line spot', then there is the interaction between the second speaker and the open end, then there is also the interaction between the second speaker and the other speaker... I would think the sum of these responses would be your actual output... it is going to be a bit hairy to model  especially if you are not crossing over the speakers... if you do cross them over (and ones plays lower and the other higher) I would think, for the most part (except at the crossover frequency) the 'other speaker' could be seen as a passive radiator...


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## villain3g

Maybe I'll just build them and have a driver one fifth from the closed end, the other one third from the closed end, and vary the amount of fill at the ends and in between, trial and error?


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## Chester

I guess... Not sure of a good system to figure out that stuff...


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## villain3g

Made some headway on the speakers over the past two days. The New York snow storm gave me the push I needed to get started. Ive got them assembled and running, just need to finish them. My first impression was "WOW, There is acutally some bass coming out of these." After the initial shock, I was dissapointed with the upper frequency range. I havent tuned the line yet. I imagine some dampening will clear that up some. Attached are some pictures of the construction process.


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## Lobotomy^

I like curved version of tansmission line. Makes it look a little like ant nest.


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## Anthony

Great work. I love the look of them. Depending on what you don't like about the drivers, you may need to apply a shaping filter on them to knock down a cone breakup mode (scratchy shrill static-y sound), tame a resonance peak, baffle step compensation, etc.. Not a crossover, but it might tune in your response more if you can't get it all from port tuning. The nice thing is that these filters are usually only 2 or 3 parts.

Keep us posted!


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## JCD

First, I hate you.. anoyone that can pull off that design deserves to be hated. :doh:
Second, I have no idea how the design works, but I like the way it looks. :nerd:
Third, have you tried placing the speaker in different places? For example, I would have thought a di-pole like that would need more space behind it. :huh:
Fourth, where are the REW graphs? addle:


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## hm-moreart

Hello,
1. large for the used air volume
2. some measurements?
3 bass?

my solution were a small bipol double horn
the Kornett


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## hm-moreart

inside Kornett



and the best Imp i ever seen by horns


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## F1 fan

Great work on those cabinets.:TThe laminated plywood is remaniscent of the mega buck Magico line of speakers.


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## villain3g

what measurement equipment do you recommend? Anything cheap but accurate?


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## Anthony

Easiest would be Room EQ Wizard on this site (REW for short). Go to the REW forums and there are a lot of recommendations. A $50 microphone, $50 mixer board, and some cables and the computer you already have. A bit more for nicer or calibrated mics, and if you use a laptop, you may need an external soundcard. Lots of good info in those forums.


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## JCD

As as been mentioned by Anthony, testing equipment isn't too expensive
A common microphone is the ECM8000 which can be found for $50 all over the web. The only caveat is that it needs a microphone cable connection (XLR) on the sound card to attach it to.
REW is free for the download
And then find a sound card (external for laptops) that has a microphone connection (XLR). M-audio has a several that get good reviews.


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## villain3g

Great, thanks! I'll check it out. I'd also like to measure my quasi-line arrays and my father's ESS Heils.


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## villain3g

I stained using Minwax red oak and put on five coats of clear gloss. I would've kept the wood a little brighter but these are a gift for my brother and he has red oak. The brass screws on the side look great against the dark wood. I've got three inexpensive chair glides instead of spikes because the room they are going in has hardwood floors.


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## Paul P

Nice work









So how do they sound ?

I've never heard a transmission line speaker... your drivers look awfully small.

Paul P


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## Anthony

I use the ECM8000 and the M-Audio Mobile pre and a laptop. That's perfect for REW measurements on the go. The phantom power for the microphone can be provided by the laptop battery if need-be (no power cords). You have gain knobs on the sound-card, so there is a little volume/level/gain fiddling with each component to get the input levels and sound level right for measuring. Once you've done it a few times, though, it is pretty intuitive.

They look great!


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## villain3g

Today I compared these speakers to the ESSs in the picture. Renaissance music with harpsichord seemed to not compete with the crisp treble of the Heil driver. But the speakers seem to excel with vocal jazz and other "small" music platforms. My impression is that they out perform the heils in this format. The vocal performer seems to come forward of the sound-stage while the ESSs appear to be a broad but still two dimensional. I believe this is due to an excess of midrange. This isn't necessarily a bad thing but it does limit style of music.


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## StereoClarity

I have made a pair of similar style (in concept) speakers with similar sized drivers. The EL70's from CSS were used in a Bipole configuration with a tuned vent. The design I chose was the Thirlmere design found on page 6 of the following link. I get response down to about 45hz.
http://homepage.mac.com/planet10/CSS/EL70/Lake-District-maps-080909.pdf

I'm happy to see people getting into full range drivers and finding that bass is actually attainable!


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## villain3g

I've made some measurements using a radio shack spl meter and REW. The receiver I used it the Denon avr-1709. It has audyssey and I made measurements with and without using it. As was expected, there was a hump in the midrange from 1k to 3k. What wasn't expected was an elevated plateau from 40 to 80hz. This is quite impressive seeing as how the drivers response drops under 100hz. I guess the transmission line ans a success? The first image is the frequency response without Audyssey.


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## robbo266317

That's a nice response. Have you thought about adding a tweeter? or does it sound alright as is?
You could use a simple 1st order filter ie one cap and one coil.


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## villain3g

Can some electronic device or filter be constructed to flatten out the response to match the audyssey response?


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## villain3g

Is this what I'm looking for? I got this calculator from http://www.diyaudioandvideo.com/


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## StereoClarity

Is the second graph without the EQ? The second graph looks pretty good. What type of room/setup and how did you measure?


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## villain3g

the second graph was taken while using the Audyssey function on my receiver. I used REW, my laptop soundcard, and a radio shack digital SPL meter.


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## Anthony

Those would be worth a shot and are easy to try.

The Radio Shack SPL meter is not very accurate at the high end of the spectrum or the very low. It can be corrected, but these are generic correction files. I would hesitate to make major changes based on what it measures.

However, those parallel notch filters look right and are easy to wire up, so try one, listen, measure, and see what you think.


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## hm-moreart

Hello villain3g,

listen without the filter,
the second filter is a joke,
or you never test and listen to such a sound killer.

sorry,
what a measurement?
is any impedanz available?


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## speedie

your hand drafted concept shows twin drivers? why did you omit them in the finished version 
just curious 
ps hope that the snow has stopped


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## villain3g

There are actually two drivers in theses. One is facing diagonally up in the rear. Check out the pictures on the first page. And about the notch filter. I was able to flatten out the response by moving the speaker placement a little.


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