An inexpensive Gedlee/Bouska waveguide/tweeter midbass idea. - diyAudio
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Old 3rd June 2010, 11:19 PM   #1
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Default An inexpensive Gedlee/Bouska waveguide/tweeter midbass idea.

Iíd be using some of Earl Geddes and Jack Bouska ideas and some of my own.

The purpose is to use high quality drivers in cost effective, stiff, virtually noiseless enclosures that donít look too butt ugly. Maybe just functional ugly.

Click the image to open in full size.

Using the 2 B&C drivers and multiple cheap sealed subs is the way Iím going.

Drivers:

B&C DE 250 (Gedlee) I like itís fairly flat FR.

B&C 10PS26 (Gedlee) I like itís fairly flat FR.

10Ē DDS eng 1-90 CD Oblate Spheroid waveguide. Not as good as a Gedlee WG, especially around the driver WG interface. Where the DDS contacts the round enclosure, Iíll trim the DDS to curve around the MDF. Placing some wool or foam to reduce reflections back into the WG and edge diffractions.

Click the image to open in full size.


Foam roundover taped around the DDS WG. Using $1 3Ē diameter swim Noodle for kids.

Sealed enclosure will be a 10Ē sonotube inside a 12Ē sonotube for 10Ē mid/bass driver (Like Bouska photo below). No roundover needed for frequencies used. The air space between sonotubes will have poly fill and should greatly reduce sound from the enclosure to the room. The outer tubes will be wrapped in some type of black or white contact paper to look a little nicer. Maybe just painting it.

Click the image to open in full size.

Enclosure length TBD because I donít know if I want to have it for 100hz or 80hz yet.

Open celled foam filling interior behind mid/bass.

Ends of mid/bass cylinder enclosures to be routered from 1Ē MDF. Xover and 100W Icepower amp to be mounted on the back outside of the rear MDF.

The MDF end caps will not be round like Bouska but have a flat bottom to sit on speaker stands (see rough illustration)

DDS to sit on top of mid/bass enclosure with driver in the open. Mounting hardware TBD. Or use a 10Ē sonotube ( bottom 10% cut off to sit on top of mid/bass tube) on the DDS. Then the speaker would look like a tube on a tube. Maybe use some 30PPI foam in the mouth of the DDS. Maybe not.

Xover to start: around 1,500hz no EQ 1st order (Bouska).

Xover later (maybe): with a Behringer DCX 8th order with EQ. (Bouska).

Perfect? Not a chance. Iíll be lucky to get 75-80% of the sounds Bouska and Geddes get. The pair should cost less than half the price of a Gedlee DIY Nathan kit ($1,000).

Iím sure Iíve left out a few details but itís just an idea for now.

What would you change?
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Old 3rd June 2010, 11:45 PM   #2
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cylinders look great, but could be prone to standing waves inside; a couple of semi-partitions/ braces inside should fix that though
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 4th June 2010, 04:15 AM   #3
gedlee is offline gedlee  United States
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Quote:
Originally Posted by makingmoney View Post
Iíll be lucky to get 75-80% of the sounds Bouska and Geddes get. The pair should cost less than half the price of a Gedlee DIY Nathan kit ($1,000).
True, perhaps, but as with most things in audio that last little bit gets expensive. The new kits now come with a fully assembled, high rigidity, low diffraction, solid polyurethane enclosure ready to paint. So there is a lot of manual labor in the price difference that you are quoting. In the end I don't think that you are saving that much and the performance difference could be greater than what you are hoping for.

Personally, I don't like the idea of flat ends on tubes. I don't see where it saves much cost or labor but adds a lot of downside from an acoustic perspective.

But at any rate good luck - I guess emulation is a highest form of compliment, so thanks.
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Old 4th June 2010, 04:43 PM   #4
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Quote:
Originally Posted by gedlee View Post
Personally, I don't like the idea of flat ends on tubes. I don't see where it saves much cost or labor but adds a lot of downside from an acoustic perspective.
I'll be creating an irregular surface with some wood shapes. perhaps a solid wood cone shape or solid wood half round ball on the inside back surface to diffuse the sound.

Will also use some soft thick rubber to help diffuse the bounce of the back wave. The soft rubber will also be on the back of the B&C driver to help reduce reflections inside.

Some fiberglass or long haired wool will be inside also.

I've all used these things to varying degrees of success for years.

The 2" flat sharp edge front baffle around the 10" driver should not be a diffraction problem when used up to 1500hz. I think at that frequency the sound should start being less omnidirectional. Wavelength at 1500 is around 9" so 2" baffle should not be a problem. But if it is I'll add a 3" foam roundover.

Thanks
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Old 4th June 2010, 06:50 PM   #5
doug20 is offline doug20  United States
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is there a reason you are going with the more expensive DDS waveguide which has a history of being poorly developed over a very, very low cost option like the QSC 10" Waveguide found on the HPR-122i and can be purchased from the QSC online parts site?

You are going to save yourself almost $200 just switching without any real different in SQ.
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Old 4th June 2010, 07:39 PM   #6
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Quote:
Originally Posted by doug20 View Post
is there a reason you are going with the more expensive DDS waveguide which has a history of being poorly developed over a very, very low cost option like the QSC 10" Waveguide found on the HPR-122i and can be purchased from the QSC online parts site?

You are going to save yourself almost $200 just switching without any real different in SQ.
I think DDS quality problems are over. It is CD and OS.

Is the QSC CD and OS?

I can't find any definitive info. Maybe it's a spherical conical shape?

Do you have them and what have you compared them to?
What driver do you use?

Thanks.
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Old 4th June 2010, 08:21 PM   #7
doug20 is offline doug20  United States
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Quote:
Originally Posted by makingmoney View Post
I think DDS quality problems are over. It is CD and OS.

Is the QSC CD and OS?

I can't find any definitive info. Maybe it's a spherical conical shape?

Do you have them and what have you compared them to?
What driver do you use?

Thanks.
That is great to read that the DDS problems are over. Is it easier to order and receive them now then it was too?

QSC is CD, Augerpro as all the measurements. Geddes Harper didnt really measure better in comparison. Also Zilch just did build with them over on PE.

Build and measurements found here..
http://techtalk.parts-express.com/sh...215536&page=15

As for drivers, I have many. (Celestion 1745, 1525. Radian 475b, BMS 4550, 4552. Selenium D220). They all fit the 10" waveguide but Im currently building several speakers with the QSC HPR-152i rectange waveguide instead. Its even a better choice (cheap too).

Are they OS? I think they are exponential, I can not remember though and Im not home to check. I have them and about 5 other waveguide choices.
EDIT:

here is a pic
Click the image to open in full size.

There isnt anything audiably superior to having a OS design. What is important is how the diffraction is minimized.

Im not debating with the DDS being bad, its good as long as the issues of their production have been solved. I didnt know if you knew about the extremely cheap QSC options.

The only question really, is it $180 better then the QSC choice? .

Last edited by doug20; 4th June 2010 at 08:30 PM.
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Old 4th June 2010, 10:10 PM   #8
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Yes I've seen those.
On the next page post#309 are an interesting comparison of the 14"x10" QSC WG and the 10" round QSC 122i. Bigger looks better. But too big for my space.

The QSC at $7 ea is tempting.

The QSC 122i looks like it needs to be xover at 2500-3000 according to Zilch for best results. Not a match for the B&C 10PS26 where 2000 looks tops.

The DDS FR is 1K-18K so I figure 1500 will be doable, maybe it'll be a bit higher.

Currently I have the B&C DE250 on a horn (HFP128? 8"x8") with fairly flat FR. Not much horny sound.
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Old 5th June 2010, 12:55 AM   #9
doug20 is offline doug20  United States
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I think bigger always seems to better, I remember others posting that the bigger the waveguide the lower the XO and the easier it is to match directivity.

Zilch does at 2500Hz Xo because he uses the small 1425 CD which has been XOed above 2KHz. Im pretty sure the DE250 can be XOed at 1500 with the QSC 122i. I will have to measure the BMS4550 with my QSC 122i to double check that.

Anyways, no doubt the DDS is a fine choice. Its good to read they have less issues now with production runs. Where did you order yours?
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Old 5th June 2010, 12:57 AM   #10
djn is offline djn  United States
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Quote:
Originally Posted by gedlee View Post
Personally, I don't like the idea of flat ends on tubes. I don't see where it saves much cost or labor but adds a lot of downside from an acoustic perspective.
Hi Earl, I've thought about that and came up with the idea of using schedule 80 PVC (12") and then capping them with the rounded cap they make for it. The end would not be totally spherical (SP) but rounded enough.
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