Gleden-II Loudspeaker System - in English

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Gleden-II Loudspeaker System - in English

HozzászólásSzerző: pagrus » 2011.04.14. 21:39

This is shortened summary about Gleden-II.
(A more detailed description is available in Hungarian language: http://diyaudio.hu/forum/viewtopic.php?f=21&t=306)

Gleden-II is the extension of Gleden using a bass-woofer in a separate box.
This addition makes it necessary to change the reflex tube of Gleden to a full length Audyn BRT 50-145, thus the group delay and phasing will improve.

Sensitivity: 91 dB @ 2,83 V - optimized for tube / valve amplifiers
Impedance: 5 Ohm

The bass-midrange still does not have any crossover, in fact this is one of the basic ideas beneath this design. Another idea is crossing the tweeter with a 1st order filter, yet another idea is to optimize the crossing of the bass-woofer regarding phase; in this case it is at 420 Hz. The given phase response makes the frequency response linear, and provides suitable bass response due to the phase "mixture" of the speakers providing natural baffle-step compensation. In my room the F3 is at 32 Hz (it depends on placement).
In fact, this kind of construction is not related to these specific drivers, in theory you might use any kind of drivers as long as both of the above 3 ideas are met: for example a Fostex or Sonido mid-range might work as well, although it might be hard to find suitable woofer and tweeter for a some of them.
The upper and lower parts are tuned impedance-wise as well, thus the result is perfect for tube/valve amplifiers.

Gleden-II.jpg
Gleden-II.jpg (142.78 KiB) Megtekintve 8394 alkalommal.

Bass-woofer: Vifa M25WO-49-08
Alternative: Seas CA26RE4X - I have them but they have not been tested in this design yet, so I recommend prototyping it before using. If someone is interested I can lend them for testing.

The inner size of the enclosure is 730 x 280 x 330 mm (net 46 liter) it is made of 18 mm plywood and does not have any bracing.
Total use of materials (because of the 18 mm "legs" and 22 mm upper "wings"):
4 pcs of 770 x 330 mm sheet
4 pcs of 730 x 244 mm sheet
4 pcs of 294 x 244 mm sheet

Originally I used only a 55 mm piece of the larger BRT 68-220 reflex tube, later I switched to a fullsized one (173 mm) due to my room likes the lower tuning more.
( http://www.audionl.hu/oscommerce/catalo ... cts_id=232 )
The center of the tube is located 300 mm away from the lower edge of the front.

The stuffing weighs around 260-270 gram per side.

Sealing:

gleden-II-ragasztas.jpg
gleden-II-ragasztas.jpg (64.05 KiB) Megtekintve 8394 alkalommal.

The phase response might be tuned by changing the depth of the upper cabinet relating to the lower one; it is not recommended to go for the usual linearizaton of the phase, since the whole idea is to utilize the phase more for compensation.
I covered the upper edge of the lower part with a piece of polyfoam:

Gleden-II-fazis-beall.jpg
Gleden-II-fazis-beall.jpg (65.49 KiB) Megtekintve 8394 alkalommal.

Crossover:

Gleden-II-valto.jpg
Gleden-II-valto.jpg (24.45 KiB) Megtekintve 8394 alkalommal.

The impedance response has a bump at 4kHz, this might be lowered with some further tuning in case if it is problematic due to some rather sensitive tube/valve amplifier. I let it as it is as my amplifier is able to handle it:

Gleden-II-impedancia.jpeg
Gleden-II-impedancia.jpeg (82.75 KiB) Megtekintve 8394 alkalommal.
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Gleden-II Loudspeaker System

HozzászólásSzerző: pagrus » 2011.04.14. 21:42

Tuning the bass cabinet lower and stuffing the reflex tube might be a good idea if you want to further improve group-delay, but needs some careful tuning in relation with the actual room-acoustics.
(blue - stuffed reflex tube, purple - closed, red - reflex)

Gleden-II-group-delay.jpg
Gleden-II-group-delay.jpg (34.45 KiB) Megtekintve 8393 alkalommal.

The resulting frequency response shown together with the response of the original Gleden, optimized to my listening room:

Gleden-II-spl.jpg
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Gleden-II Loudspeaker System

HozzászólásSzerző: pagrus » 2011.04.14. 21:44

Some thoughts about tuning the speaker to the actual room acoustics:
My setup looks like this:

hangfal-elrendezes.png
hangfal-elrendezes.png (3.81 KiB) Megtekintve 8393 alkalommal.

The speakers are more than 3 m away from the back of the room, the listening position are 6 m away from the back wall.
The localization of musical instruments are usually placed well in the resulting space around 5-6 or even more meters away that is reminiscent of the feeling of small concert halls.
The following measurement shows the high response in function of distance of the speakers. (The curves are measured 1.5 - 2 - 2.5 - 3 meters away.)
A more natural sound might appear when the speakers 3 meters away are actually modelling the high response of sound sources being 5-6 meters away (as it is in my case). This means 3 m real space and 2-3 m "virtual space". The theoretical correction curves: the 6 dB bass boost of the baffle step compensation combined with the high frequency rolloff of the extra air mass (4,2 dB @ 20 kHz measured in my room):

bs+levego-tavlat.jpg
bs+levego-tavlat.jpg (62.87 KiB) Megtekintve 8393 alkalommal.

These values mostly overestimate the system, so I recommend everyone to find the right values in between. :)
As I suppose, some speaker systems used to build on this feature of the gentle high frequency roll-off, however I have never seen any actual measurement of it. It still might be the result of the same intuitive experience.

While my Gleden might sound fine using 1,8 uF + 100 uH at my place, at Zsolti his Gleden might need 2 uF + 80 uH components plus closer location of the speakers to the walls.
The difference is subtle, and I do not really recognize it as a difference between various high frequency responses, the question is more about the opera singers having a "smooth, natural" voice or not - just like they are singing in my room live - well, not really, but sort of... :)
A hozzászólást 2 alkalommal szerkesztették, utoljára pagrus 2011.04.14. 21:52-kor.
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Re: Gleden-II Loudspeaker System - in English

HozzászólásSzerző: pagrus » 2011.04.14. 21:47

The combined impedance of the lower and upper boxes are rather smooth overall due to the bumps and valleys compensating each other:

Gleden-impedanciak.jpg
Gleden-impedanciak.jpg (58.57 KiB) Megtekintve 8392 alkalommal.

This smooth impedance does not work with multi-amplification, still it might be a good idea to try it for some other benefits. In a bi-amplificated system one amplifier should handle the middle only (without the bass-woofer and the tweeter), the other one should handle the bass woofer joined with the tweeter:

Gleden-II-multiamp.jpg
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