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Old 22nd April 2010, 02:13 AM   #21
CLS is offline CLS  Taiwan
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Hi Peter,

Great jobs in making all these cabinets, especially this Opus One, just WOW!

And it's also great to see a speaker builder nearby (small island, after all ) showing up here Please keep posting. We all love to see photos of woodworks

I noticed you've used both MDF and plywood in making this horn, are there any particular purposes? I might think of speading the intrinsic resonances of the materials themselves. How did you plan and decide which be applied to where? The back chamber alone has these two materials and they are (sort of) asymmetric! That's very bold!

As to the horn loading, I think this is a corner horn and should be pushed into a corner (as possible). The two side openings should meet the walls in a very close distance and the walls (and floor) form the last section of the horn - like a K-horn or other corner horns. And this should be the reason of the angle of the 2 side walls, which is obvious less than 90 degree - to make some room both sides when located at an ordinary 90 degree corner.

I think the actual size of the terminus (distance to wall) and the angle are crucial to the last section of horn flare. A corner horn which is not placed right at the corner would make the actual horn shorter and mouth (abruptly) bigger, which is not a good thing in loading the LF.

Have been playing with a famous simulation tool - Hornresp, I've found a corner horn which leaves the corner would certainly have less SPL in LF and probably more ragged response. A few experiences with K-horn reveal similar results, so please try to locate your horn into the corner as possible, and you'll surely have some differences. I'd expect deeper, louder, and even smoother bass

CLS
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Old 22nd April 2010, 02:19 AM   #22
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Default Lowther Opus one model B

Quote:
Originally Posted by Andrewbee View Post
Hello Peter,

Please keep posting about your project.
I have been planning for about 1 year now to build a pair of Lowther Horns, either the TP1 ISIS or the OPUS like you but have been told that the designs from Lowther on the CD are inaccurate which you are also saying. I may still order the cd anyway and measure and cut as I go along if I ever decide which ones to build.

Congratulations on your project.

Andrew
Dear Andrew,

I am glad of your interesting and response in this project.

I think you don't need to worry about the design. The drawing of Opus one model B has no big problem, just some minor errors. Cutting and assembly of the panels don’t need to be very accurate, but should be as accurate as possible you can do. Mating tightly would be more important. I cut the panels as accurate as possible and still found many edges need to be scraped out a little. That is not the fault of the design inaccurate, but because of the accumulation of the inaccuracy from the pre-drawing, cutting and assembly. Cutting the panels a little more than the designed dimensions, about 0.5-1 mm, will allow the assembly work easier.

I also struggled in the selection of big cabinet, Audiovector, Tp1, and Opus one . Finally, I select Opus one model B, mainly because I want to experiment that a pair of well-designed speaker can be placed into corners. Some local audiophile told me that it is stupid to put loudspeakers into the corners; the bass will be blurred; except that you have ear problems. Another reason is that I want to test the performance of the strongest driver PM4A. Opus one B is very suitable for PM4A.

Remember that parallel panels inside the cabinet, parallel panels on the horn mouth, and paralls between cabinets and outside walls will result different kind of resonances. A little resonance maybe good to the sound. But the corner which physically enhances those resonances seems to be harmful, especially to the bass.

My 2 cents idea for your reference.
__________________
My DIYs: Lowther Academy, Acousta 115, Opus one B; Jordan VTL JX92s; Jericho Horn with Fostex FE206, SOZ, BOSOZ, Zen Lite, V8 & V9

Last edited by Peter Huang; 22nd April 2010 at 02:22 AM.
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Old 22nd April 2010, 05:55 AM   #23
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Default Lowther Opus one model B

Quote:
Originally Posted by CLS View Post
Hi Peter,

Great jobs in making all these cabinets, especially this Opus One, just WOW!

And it's also great to see a speaker builder nearby (small island, after all ) showing up here Please keep posting. We all love to see photos of woodworks

I noticed you've used both MDF and plywood in making this horn, are there any particular purposes? I might think of speading the intrinsic resonances of the materials themselves. How did you plan and decide which be applied to where? The back chamber alone has these two materials and they are (sort of) asymmetric! That's very bold!

As to the horn loading, I think this is a corner horn and should be pushed into a corner (as possible). The two side openings should meet the walls in a very close distance and the walls (and floor) form the last section of the horn - like a K-horn or other corner horns. And this should be the reason of the angle of the 2 side walls, which is obvious less than 90 degree - to make some room both sides when located at an ordinary 90 degree corner.

I think the actual size of the terminus (distance to wall) and the angle are crucial to the last section of horn flare. A corner horn which is not placed right at the corner would make the actual horn shorter and mouth (abruptly) bigger, which is not a good thing in loading the LF.

Have been playing with a famous simulation tool - Hornresp, I've found a corner horn which leaves the corner would certainly have less SPL in LF and probably more ragged response. A few experiences with K-horn reveal similar results, so please try to locate your horn into the corner as possible, and you'll surely have some differences. I'd expect deeper, louder, and even smoother bass

CLS
I use both MDF and plywood together just because I want to completely use all materials up.

Originally I plan to use MDF for all panels. However, I can’t find large enough MDF panels for the side panels in local woodshops, so that I use plywood instead. I try to make use of remains of plywood. Almost panels are made of MDF.

Checking all lowther cabinets designs, I found that Audiovector uses plywood, Acousta 115 uses blockboards, TP1 could use plywood Or MDF, and Opus one uses MDF. So, I judged that both MDF and plywood are good materials for horn.

I heard that the type and origins of woods are very important to horn build. Even somebody said they have listened that their horn made of birch plywood imported from northern Europe, 10 times more expensive, has better performance than the plywood or MDF from Southeast Asia. I always doubt that and wonder whether it is worthy. I think that the horn is designed to transmit the sound wave in a path from the throat to the mouth and resonant in the path should be as little as possible. Since the resonant or sound reflex in a well designed horn is very minor, any kind of material, if tough enough, could be used. The physical principle of horn is different from the ones of bass reflex cabinet. I think that the design of horn is much more important than the material selection. Also, the path dimensions of folded horn have many errors than theoretical one.

I highly appreciate that someone can offer a physical explanation or objective measurement to proof above issue.

Dear CLS, thanks a lot for your advice on horn placement. I have already put the horn getting into the corner. I will experiment the sound difference of different distance and angle against the room wall.

Best Regards,
__________________
My DIYs: Lowther Academy, Acousta 115, Opus one B; Jordan VTL JX92s; Jericho Horn with Fostex FE206, SOZ, BOSOZ, Zen Lite, V8 & V9
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Old 22nd April 2010, 07:02 AM   #24
hm is offline hm  Europe
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Hello,
a bass horn is always to short and to small,
so the flare rate and length is most important,
and the material,
my experience shows birch multiplex 18 mm (10 cross layers)
in combination with softfiber the first m and the press chamber
will reduce colloration at the upper horn frequency range.

look my HP, with mesurements and compair it to other horn responces.

BTW: did someone a measurement from the OPUS and a IMP,
IMHO the OPUS is much to large for the result,
look my ALPHORN with SCHALMEI, SAXOPHON, RDH20
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Old 22nd April 2010, 02:21 PM   #25
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Hi, Dear hm

Thanks for your offer the experience of combination materials used in compression chamber.
You are genius for horn design. Horn-Sat + Alphorn looks very impressive.

Best Regards,
__________________
My DIYs: Lowther Academy, Acousta 115, Opus one B; Jordan VTL JX92s; Jericho Horn with Fostex FE206, SOZ, BOSOZ, Zen Lite, V8 & V9
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Old 23rd April 2010, 12:41 AM   #26
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Quote:
Originally Posted by hm View Post
Hello,
my experience shows birch multiplex 18 mm (10 cross layers)
in combination with softfiber the first m and the press chamber
will reduce colloration at the upper horn frequency range.
Lowther uses the Bicor idea to reduce resonant or coloration for Opus one by adding a throat in the compression chamber. The area of added throat is about 1/3 of horn throat. There is no need to add damping material in the compression chamber for Opus one.
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My DIYs: Lowther Academy, Acousta 115, Opus one B; Jordan VTL JX92s; Jericho Horn with Fostex FE206, SOZ, BOSOZ, Zen Lite, V8 & V9
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Old 23rd April 2010, 06:56 AM   #27
hm is offline hm  Europe
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Hello,
bicor effect: make a IMP with and without the Bicor effect
than you will see where it work,
IMHO it has nothing to do with colorations over ~200 Hz.
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Old 23rd April 2010, 02:18 PM   #28
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Dear HM,
I don't understand what you mean.
Would you please write them by German?
I could try to translate in my way.
What is the definition of IMP?
Danke.
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My DIYs: Lowther Academy, Acousta 115, Opus one B; Jordan VTL JX92s; Jericho Horn with Fostex FE206, SOZ, BOSOZ, Zen Lite, V8 & V9
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Old 23rd April 2010, 02:32 PM   #29
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Default Lowther Opus One model B

When the build progress so far neared to the ending, I found there are more questions than answer.

The compression chamber has second upper throat which called Bicor devised by Lowther. The lower throat matches a pair of divided panels to gradually expand the horn contour; however, the upper throat doesn’t connect to any dividing panel. Even there is a big empty space around the compression chamber connected to the upper throat. Since the area of the upper throat is about 1/3 of the horn throat, physically 1/3 of the sound wave from compression chamber will escape to that buffer space. I wrote an email to Lowther Company asking whether it is a need to add two panels to block that buffer space, and should I add some damping materials into that buffer space. Kindly Lowther quickly replied that there is no need to add any panel and damping material, and “bicor systems should always have a large chamber area before restricting the outlet”.
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My DIYs: Lowther Academy, Acousta 115, Opus one B; Jordan VTL JX92s; Jericho Horn with Fostex FE206, SOZ, BOSOZ, Zen Lite, V8 & V9
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Old 23rd April 2010, 02:40 PM   #30
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Very interesting and complicated build. Nice work.
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