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PostPosted: 12 Jan 2013, 12:06 
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Joined: 08 Jan 2013, 08:39
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Great!


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PostPosted: 21 Jan 2013, 21:13 
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Anyone have a concept of how many bags of fill I need for both speakers.? The come in 1lb bags.


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PostPosted: 22 Jan 2013, 01:09 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I only lined the top chamber with thick Dacron (Tonteen). I stayed well back from the throat (brace).

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


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PostPosted: 24 Mar 2013, 06:38 
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I had a friend test the Fostex today. Firstly there is little to no difference with the grills on or off with my speakers. So leave them on. Also there appears to be a lot of mid range coming from the port. I'm suggesting then that the bottom chamber have a thin lining of absorbing material to reduce this. I have always felt that these speakers have a good bottom end. Not hard to see they extend down to 40Hz where the port is working hard (yellow graph).
Attachment:
Foz 1.jpg


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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


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PostPosted: 28 Mar 2013, 17:22 
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Hi Mark,

Great stuff. I just got a RTA system and can't wait to start measuring speaker response.

For the damping, you could try adding some well teased stuffing in the upper chamber. You can do this though the driver cutout. Did you also get some far field response measurements of the speakers?

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 28 Mar 2013, 18:13 
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Gio: The top is dampened it is just the bottom chamber I feel needs some work. I see if a got a far field measurement.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


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PostPosted: 23 Jul 2014, 08:51 
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Location: Atherton, QLD, Australia
Hi All,

I've decided to build these speakers too. My first worry was if the bass would be sufficient. Well... there is plenty of bass and I'm very happy with it.
But the speakers also seem to be very unforgiven. Some music comes out absolutely brilliant and other music sounds just crappy. And as you would understand by now it is that midrange area. Sometimes it goes shouty and very annoying.
I'm using a 16W s5-electronics tube amp with tone control. The tone control is just not sufficient to get rid of the shoutiness. So at the moment the tone control is set both to centre and I'm using a 10band graphic EQ to get the sound close to what I like. I take out a fair bit around the 1 KHz.

Will a BSC eliminate the use of the EQ? And is the use if an EQ a good idea anyway or is the BSC the preferred solution?

And also some information about my project.
I used 15mm plywood instead of the recommended 18mm. This is because we can not get decent plywood here in the far north. I used marine-ply because it's made of A-grade veneer and looks good at the sides (no holes and other mistakes) So far the construction seems firm enough.

And I usually take more of this online community than I (can) put in so the least I can do is to post some pictures of the building process.
I like working with steel more than wood but since I have a circular handsaw and a router I really like woodwork too.
Here some tips. Please note the the pics of the bass port are from a trial run to test the router jig.

The pics are not in the right order but you'll work it out.
Now I just have to open a new post to show the end results.


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Last edited by Pieter on 23 Jul 2014, 09:13, edited 1 time in total.

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PostPosted: 23 Jul 2014, 09:08 
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Location: Atherton, QLD, Australia
And here the end results of the posted pictures above.

As you can see, you can create an end product without any gaps or sticking out bits and still cut your own ply with just a hand circular-saw.
If there is an uneven part in your build just sand it level before glueing. And with the panels that stick out a bit oversize you can flush router away whats needed.
No one will see those little size differences or slightly bend ply. But if you must leave a gap or something sticks out it looks ugly straight away.

I had fun building this thing. It's just a simple design, and the sound result is very good. (relatively cheap project too!)


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PostPosted: 27 Jul 2014, 10:39 
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Pieter wrote:
But the speakers also seem to be very unforgiven. Some music comes out absolutely brilliant and other music sounds just crappy. And as you would understand by now it is that midrange area. Sometimes it goes shouty and very annoying.
I'm using a 16W s5-electronics tube amp with tone control. The tone control is just not sufficient to get rid of the shoutiness. So at the moment the tone control is set both to centre and I'm using a 10band graphic EQ to get the sound close to what I like. I take out a fair bit around the 1 KHz.

Will a BSC eliminate the use of the EQ? And is the use if an EQ a good idea anyway or is the BSC the preferred solution?

Hi Pieter, your build looks good. Getting the proper balance is tough part. I suggest you start with the room and speaker placement to find the best configuration that requires the least amount of correction. Getting the speakers closer to a rear wall can help. Also, are you toeing in the speakers? Try them about 10 to 30 degrees off-axis.

Correction will help be it from a BSC or an EQ. Which is better is somewhat subjective and a mater of personal taste. The EQ is nice as it is adjustable. Start with the EQ as it will get you there much quicker. Once you get the right level, then you can decide if you want to try a different correction circuit. How much are you turning down with the EQ? Just around 1kHz or from 1kHz and up?

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 02 Aug 2014, 17:26 
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Joined: 24 Nov 2013, 00:50
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Location: Atherton, QLD, Australia
Hi Gio,
Thanks for your reply. I have the speakers off-axis. But that has more to do with the very small sweet spot they seem to have. But that's ok when you listen to music, one sits down at the best spot anyway. I've build a BSC (1mH and 2.35ohm 20Watt) and the speakers are less bi-polar. I think I will leave it like that for some time. You give up on some of the crispness but the moments of the shoutiness and the EQ all over the place are gone.
It's only the midrange I turn down. The base and high comes up a bit.
Before these speakers I had just a crappy pair. One setup for all sorts of music. Now is seems every CD is so differently recorded (or mastered) I need to do some adjusting for personal taste.
However the result is far better in the end.

Regards Pieter


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