Transmission Line Speaker Build using Alpair 7.3 speakers, first build. - diyAudio
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Old 17th March 2017, 11:17 PM   #1
vishalk is offline vishalk  United Kingdom
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Default Transmission Line Speaker Build using Alpair 7.3 speakers, first build.

Hi All, thought i would share my work so far! Ill write more later on to accompany the pictures on here, but these should give you a good idea of what i have been up to!


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Old 18th March 2017, 03:18 PM   #2
zacster is offline zacster  United States
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Wow, very nice. I'd really be curious about how they sound. I have a pair of 7.3 in the FH cabinet, but my build wasn't so great so I'm thinking of something else for them.

So, did you create a router template for the cutout and do the layers individually?
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Old 18th March 2017, 04:18 PM   #3
xrk971 is offline xrk971  United States
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Was this designed for the A7.3 driver or was it borrowed from the commercial one for a Fostex I have seen somewhere on a Japanese website?

Last edited by xrk971; 18th March 2017 at 04:24 PM.
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Old 18th March 2017, 05:04 PM   #4
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Pretty adventurous for a first build, well done
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Old 19th March 2017, 12:41 PM   #5
vishalk is offline vishalk  United Kingdom
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Quote:
Originally Posted by zacster View Post
Wow, very nice. I'd really be curious about how they sound. I have a pair of 7.3 in the FH cabinet, but my build wasn't so great so I'm thinking of something else for them.

So, did you create a router template for the cutout and do the layers individually?
Hi Zacster, these were made on a CNC router by a gentleman in France called Christian Pop, yes each part was cut and then layered. All i had to do was glue and clamp them.

Ill post the results of the frequency response and testing i got from REW with my mini dsp mic.

But presently they sound wonderful and surprisingly the bass is clean and present!
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Old 19th March 2017, 12:47 PM   #6
vishalk is offline vishalk  United Kingdom
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Quote:
Originally Posted by xrk971 View Post
Was this designed for the A7.3 driver or was it borrowed from the commercial one for a Fostex I have seen somewhere on a Japanese website?

Hi xrk971

These were designed around using the Alpair 7.3, Parameters were Qts 0.4-0.6 and Fs between 70 - 80hz.

I've always wanted to try this type of design as i have built a few normal bass reflex boxes. I also wanted them to be efficient as i am using a valve amplifier with only 3.5w of power.

Not only that with the use of CNC routers makes this type of build possible and easier to construct. I was very impressed by the build, obviously it needed some work but that's the fun of it.
Attached Images
File Type: jpg speakertl.jpg (640.1 KB, 69 views)
File Type: jpg speakertl2.jpg (826.3 KB, 72 views)

Last edited by vishalk; 19th March 2017 at 12:51 PM.
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Old 19th March 2017, 10:54 PM   #7
vishalk is offline vishalk  United Kingdom
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Default REW speaker testing

In order for me to really know how these speakers sound i wanted to do some loudspeaker measurements.

I didn't want to spend a great deal of money so with some research i invested in the mini dsp UMIK-1 and the brilliant free software REW (Room EQ Wizard)

https://www.minidsp.com/applications...r-measurements

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I used a DAC Modi from Schiit Audio connected to a class D amplifier.

What i wanted to see was how different types of wadding and also placement of wadding had an effect on the characteristics of the loudspeaker.

I did this until i got the sound i liked and the response i though was better (based on the SPL and phase).



The first measurement is just the loudspeaker in the box with no wadding.

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This next screenshot is with wadding compared to without


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This screenshot is a mixture of all the different waddings.


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Any advice or tips would be most welcome!
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Old 20th March 2017, 02:31 AM   #8
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It's fun to take measurements right in front of the speaker and see how they work.

But, ultimately, you'll want to place them in your room, put the mic at the listening position and level, and measure from there.

Playing with speaker position, you'll probably see that huge 10k shelf disappear.
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Old 20th March 2017, 03:06 AM   #9
chrisb is offline chrisb  Canada
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Perceval - while I think you're right about the measurement set up as shown being problematic, what I'd be far more concerned about is the crazy almost 30dB spike centering at 200Hz - which is almost exactly the wavelength of the 1.7m noted as length of the line.

Something very similar to vishalk's measurement is seen in MA's published graphs - although the to not quit the same extreme, and FWIW it should be noted that the latter extend to 40Kz

I've used this driver in literally dozens of enclosures from 6liter sealed ( great for desk-top, but they deserve better IMO)Woden Maeshowe, Pensil, Frugelhorn, several MarKens, custom FASTs, etc. They are definitely capable of much better low frequency response than that shown in the measurements here.
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Last edited by chrisb; 20th March 2017 at 03:14 AM.
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Old 20th March 2017, 03:24 AM   #10
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True.

There's something fishy happening between 160 and 260Hz.
Phase inversion?

Plus, it's a free fall drop below 100Hz... I have a few 4" drivers in MLTL and they can reach 50Hz easily.
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