Midsummer  
Saturday, June 26, 2010, 15:35
Posted by Anders
Midsummer is upon us, and what better opportunity is there to give the new members of my DIY family a proper outdoor test in a true 2PI (half space) environment.

Seeing as the neighbors was away, and it being a day worth celebrating, the acceptance for noise pollution would be slightly higher then usual.



There is no chance, i remember thinking, that these minute 6,5" loaded tapped horns could offer up any kind of solid low end under these conditions, at best it will be noticeable, but beyond that probably nothing.

Outdoor "free field" environments are particularly demanding on the low end, and the lower midrange, it all has to do with the directivity of the frequencies reproduced, the higher the directivity is, the greater the free field efficiency will be, it will no longer rely on walls for support, as is the case indoors.



As it turned out I actually ended up lowering them down to a mere +6dB over the satellites to get a good balance going, when crossed over at 200Hz they gave the small system a warm, full bodied sound with a good low end thumph with no hint of being out of it's element.

It goes without saying that the SPL's was modest, yet still well enough for most garden events, easily overpowering the occasional traffic noise leaving you to hear only the music.

I have no good explanation for how this works, but it seems that the TH principle does have something going for it directivity wise, what and how exactly i can not say.

I'm very pleased with the results.
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DIY GBG 2010 
Sunday, June 13, 2010, 13:26
Posted by Anders
hififorum.nu 's yearly do-it-yourself audio event took place in gothenburg this weekend, this time in Chalmers facilities in Johanneberg.

The lineup was somewhat thiner the previous years, but there was some really nice contributions, and there was a lot of curious visitors which is always nice.

Here's an example of mixing old and new technologies in a nice but potentially harmful way (hence the sign) :



This integrated ipod tube amplifier (above) was used with these small fullrange speakers that sounded alot bigger then they would have you belive :



Another example shows outstanding craftsmanship, unique styling and striking sound, this is DIY at it's finest :



Others put less focus on exclusive materials in favour of the engineering solutions, the results sounded a lot better then the pictures may lead you to think :





We also had some testing equipment on hand for those wanting to give their homemade electronics a tuneup :



My own contribution :



The biggest highlight of these meetings is the chance to see all my friends in this community, some of which i only meet once a year.
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The small TH race 
Sunday, April 11, 2010, 17:59
Posted by Anders
Today I got a visit from my friends in the audio-nerd community, Johannes and Joakim and they had each brought along one of their own design solutions in the small tapped horn segment.



Each one of these have different priorities and preferences as it comes to the bass they produce.

The two larger ones are of the constant area or tapped "pipe" family, that is to say they do not expand area-wise along the length of the path.



The middle sized of these had the most low end thump, but came up a bit short in the attack area, this makes it perhaps more suited as a good movie sub rather then for reproducing hard hitting rock'n'roll.

This was a deliberate move made by the designer Johannes, the 8" Tangband driver used in this sub is difficult (to say the least) to even get working in a TH, the choice of driver was not his but he made it work fine anyway.

The largest model was put together and specified by Joakim, the design however is Johannes, this one can best be described as a nice compromise between depth and attack, equipped with a 6,5" driver from seas it reaches down to 30Hz with ease and can certainly impress when it comes to SPL and thump.

The last and smallest was my own, which was the most rock'n'roll of them all, but lacking in the depth area compared to the others, it integrated more easily with the top speakers and offered the most upper end punch.

The small size made it sound lighter then the others, and as we later found out it weighs only half of the next one up, 10Kg's.

They all managed to put out amazing SPL for their size and drivers, mine topped at 119dB at the mouth, and the others was right around there as well, it translates roughly to about 110dB at a distance of one meter, and remeber, we are talking about 6,5" drivers here.



This is nothing short of impressive and comparable to much larger drivers if using conventional surface mounted designs.

All in all it was a happy and not to serious (at all) learning experience for all involved.

More about the "race" (pictures, measurements etc.) can be found here (swedish hififorum thread) :

http://www.hififorum.nu/forum/topic.asp?TOPIC_ID=79615


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a smaller sub realized 
Tuesday, March 30, 2010, 17:26
Posted by Anders


There it is, one of the new smaller subs, small is indeed a correct way to describe them, but this is true only for the eye.



I could not-not take this picture, it does not look half bad, and the funny thing is that it works soundwise as well, but it is not the way they are intended to be used



A picture with of the bigger siblings as a size comparison, and the bigger one is considered small (for a 15" 2kW PA sub).



Our living room at the moment, it will be sorted out, later... :)

The result is very pleasing indeed, the sound is solid and has a nice weight to it, the TH-sound characteristic is present, that is tight controlled and organic, very nice.

The frequency extension (see below) is sufficient for both music and movies, the usable in room response is roughly 30-120Hz without being to resonant, this makes it a good companion for my AudioPro Image 12 satelite speakers.





The plans for these subs are yours for the taking, go forth and build !
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A smaller sub proposal 
Saturday, February 20, 2010, 13:00
Posted by Anders
Another loudspeaker project, this time a much smaller 6.5" based version, but still it relies on the same tapped horn principles as the larger 15" version posted earlier in this blog.

On a side note I'm happy to announce that the 15" bigger brother design was built in Australia, Brazil, France, 2x USA (NYC and other) Macedonia and Sweden, and perhaps (probably) even more places that i do not know about yet.

Now it's time for a more domestic friendly version on the same theme, hopefully this, the baby version, will make for a small and easy weekend DIY project for those of you seeking to build a small sub for the computer or home theater system without upsetting the balance and harmony of the household.

This design has not been built to date, but the results of the design phase seems good enough to post for others to take part of.

Here's what it looks like as a 3D CAD representation :

(click the images to enlarge them)



Please note that the size of this sub is only 47x44x20.4 cm, yet it holds a 2,4 meter long horn path inside.

This is achieved by using 12mm thick plywood, and cleaver tweaking of the inner layout, the small surfaces also allows for a design entirely without inner brace panels.

Front view :


Section A-A from front view :


And then we have the Hornresp simulation input data :


The driver is the 6,5" Audes 40W65-8 that seemed to to the best job in the simulation of this very compact design, but there might be others out there that work just as well (as we found out with the 15" bigger brother).

The simulated SPL/frequency graphs below are made with several different placements in a room in mind, the input level in the simulations are 2.83 Volts or roughly 1W.

When placed in a corner :


When placed by a wall :


When placed in the middle of a room :


The intended range of this sub is 40-110 Hz but as we have seen before, the lower end range may extend further then that of the simulation by approx. 10Hz, this has been the case in many builds before, so with a little luck this small sub may reach down to 30Hz in room response.

The prefered driver for this design is the above simulated Audes 40W68 (previously known as 40W65-8), but I have looked at some other drivers that might work with this design as well.

The Seas H1224 L18RNX/P (corner):


The Seas H1215 CA18RNX (corner) :


The Peerless HDS PPB 830874 (corner) :


The Silver Flute W17RC38-08 (corner) :


18sound 6ND430 (along a wall) :


Beyma 6P200Nd (along a wall) :


If you want to build it please keep in mind that the mounting of the driver may pose a challenge but there are several ways to cope with this, either pre-mount it, or drill four holes on the cone facing outer piece large enough to fit the shaft of a screw driver, then mount the driver using nuts held in place by hand though the horn mouth, you'll figure it out.

Good luck with the build, please let me know what you think.

Br // Anders Martinsson
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