Lets see your O.B. speakers....!

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ThePriest

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Re: Lets see your O.B. speakers....!
« Reply #140 on: 6 Nov 2015, 09:14 pm »
Great looking arrays. Any chance we could see some close-ups of the metal finishing? I've played around with chemical patinas and am always curious to see what others have done.

Hi Peter.
I managed to shoot a few pic the other day.









I used acetic acid mixed in sand and spread it over the surface of the (non-stainless) steel.

The Priest

Don_S

Re: Lets see your O.B. speakers....!
« Reply #141 on: 7 Nov 2015, 01:28 am »
Acetic acid and sand.  :thumb: I had never heard of that treatment. What strength acetic acid did you use? 

I have to say I like the results.  The lack of nasty inorganic acids (sulfuric, nitric, or hydrochloric) to dispose of is also a big bonus. 

ThePriest

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Re: Lets see your O.B. speakers....!
« Reply #142 on: 7 Nov 2015, 08:45 am »
I used normal consumer strenght 32% acid, bought in the local super market.
I poured sand on to the steel, acid in the sand, and mixed the two things with a gloved hand.
After two or three days, it had some beautiful orange colours in the top rusted layer (flakes).
Unfortunately, these came off when brushed.
I had to brush the surface to keep it the rust from falling off in doors, and on top of it, I have given it a layer of bees wax.

The Priest

FullRangeMan

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Re: Lets see your O.B. speakers....!
« Reply #143 on: 7 Nov 2015, 10:17 am »
Acetic acid and sand.  :thumb: I had never heard of that treatment. What strength acetic acid did you use? 

I have to say I like the results.  The lack of nasty inorganic acids (sulfuric, nitric, or hydrochloric) to dispose of is also a big bonus.
Acetic acid is also know as vinegar for salad.

ThePriest

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Re: Lets see your O.B. speakers....!
« Reply #144 on: 7 Nov 2015, 02:51 pm »
I don't think "vinegar" I used is suitable for salad  :lol:
But yes, it s basically the same, though I do think the concentrations are different...

The Priest

Don_S

Re: Lets see your O.B. speakers....!
« Reply #145 on: 7 Nov 2015, 03:27 pm »
The Priest,

Did you have to neutralize the acid or just rinse thoroughly.  I would think rinsing would be adequate. 

Did brushing off the rust leave a textured surface?  I can't quite tell from the pictures but the darker spots look like pits.

ThePriest

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Re: Lets see your O.B. speakers....!
« Reply #146 on: 7 Nov 2015, 03:56 pm »
I don't think I neutralized it, the acid was not that strong.
I rinsed it with water and let it dry before I added the bees wax.
The surface is slightly textured, but whether it is pits or 'bubbles' from the rust is difficult to tell.
If they are pits, they are not very deep at least.
Maybe a Braille reader will be able to tell   :D

The Priest

zimmer64

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Re: Lets see your O.B. speakers....!
« Reply #147 on: 8 Nov 2015, 01:48 pm »
Hi guys,

Update from my side. I have added a BG Neo-3. The system is tri-amplified fully active using a Behringer DCX 2496 crossover, two DIY Gainclones for bass and midrange and a DIY Tubelab SSE , a passive DIY preamp and a line driver from Abacus.

The crossover points are:

Low pass 200 Hz, 18dB Butterworth
Band pass 20o Hz – 2000 Hz 18 dB Butterworth
High pass 2000 Hz 24 dB Butterworth
No EQ is used
The midrange is reduced by -5 dB
The tweeter is boosted by 5dB to compensate the tube amps sensitivity difference



The response from the front:


More pictures are in my blog https://zimmer64.wordpress.com/2015/11/08/bg-neo3-betsy-eminence-alpha-15-a-mk-iii/.

Regards

Michael

Guy 13

Re: Lets see your O.B. speakers....!
« Reply #148 on: 8 Nov 2015, 01:53 pm »

Tanks Micheal for the link to your blog,
I had a good look at your set up.
Nice place you've got,
are you an artist painter ?
Are you planning some acoustic treatment in a near future ?

Guy 13

zimmer64

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Re: Lets see your O.B. speakers....!
« Reply #149 on: 8 Nov 2015, 01:58 pm »
Tanks Micheal for the link to your blog,
I had a good look at your set up.
Nice place you've got,
are you an artist painter ?
Are you planning some acoustic treatment in a near future ?

Guy 13

My wife is an artist painter. It's her atelier, so acoustic treatment will not be done :-(

Guy 13

Re: Lets see your O.B. speakers....!
« Reply #150 on: 8 Nov 2015, 02:01 pm »
My wife is an artist painter. It's her atelier, so acoustic treatment will not be done :-(

Hi again.
It's too bad that there's no chance to have any acoustic treatment
in there, because you have good speakers and they deserve better room.
Thanks for posting.

Guy 13

frperdurabo

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Re: Lets see your O.B. speakers....!
« Reply #151 on: 24 Nov 2015, 11:37 pm »


My current system, two AE Dipole 15 woofers in offset H frames and a Lowther PM2C on an OB. Biamped with 200 W per channel solid state amps and a dBx Driverack PA active crossover.

Do you run any EQ on the Lowther? 

Early B.

Re: Lets see your O.B. speakers....!
« Reply #152 on: 25 Nov 2015, 01:31 am »
Here's what you don't see very often -- OB monitors:




mresseguie

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Re: Lets see your O.B. speakers....!
« Reply #153 on: 25 Nov 2015, 03:51 am »
Open question(s) to OB fans:

Can any driver, be it a tweeter, midrange, or woofer, be used in an open baffle design? If the answer is no, what factors determine a driver's suitability?

P.S. to Early B.:

I have often wondered about whether an OB monitor were feasible. Thanks!

Michael

Early B.

Re: Lets see your O.B. speakers....!
« Reply #154 on: 25 Nov 2015, 03:56 am »
P.S. to Early B.:

I have often wondered about whether an OB monitor were feasible. Thanks!

Totally feasible!!!  Of course, you'll need subs to mate with them. I literally waited a few years for someone to design a pair of OB monitors, and Hawthorne Audio along with Danny Richie came through in a huge way.

frperdurabo

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Re: Lets see your O.B. speakers....!
« Reply #155 on: 25 Nov 2015, 04:09 am »
Open question(s) to OB fans:

Can any driver, be it a tweeter, midrange, or woofer, be used in an open baffle design? If the answer is no, what factors determine a driver's suitability?

P.S. to Early B.:

I have often wondered about whether an OB monitor were feasible. Thanks!

Michael

If you're using a passive crossover, the woofer should have high (>.7) Qt - which is why the Eminence Alpha 15a is used so often.

You can use whatever you want for the midrange and tweeter; but if the tweeter isn't open-backed, that will effects your radiation pattern.  (Which can be bad or good - it really depends on your goals - but probably explains why so many designs use wide /full range drivers)

The woofer should be at least 10db more efficient than the other drivers, to compensate for baffle step loss.

If you're using active crossover/digital eq, pretty much any drivers can be made to work.  Just make sure your woofer has enough xmax and power handling.

I can't recommend Martin King's quarterwave.org site enough - his articles are well written and the MathCad worksheets are phenomenal.

Once you have the bass sorted (ie, your woofer is efficient enough, or you're using multiple woofs) then normal speaker design goals apply: low distortion, flat frequency response, smooth off-axis response (a big weakness of designs that use wide band drivers, alas), etc etc.

If you have the space, dipoles are wonderful.  I like Magnapans, but they need lots of amp.  I like Quad ESL 57s, too, but they're also hard to drive, and don't play loud.  I just built Martin King's Fostex Fe103/Eminence Alpha 15a project, and like a lot of what it does (I need to make a few changes to it after the holidays before rendering a more definitive verdict). 

If you've never done one before, I recommend doing a project that someone has debugged, and that's technically sound - either one of Martin King's, or the Manzanita or ... (senior moment ... there's another one AC)

bladesmith

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Re: Lets see your O.B. speakers....!
« Reply #156 on: 25 Nov 2015, 04:46 am »
Here's what you don't see very often -- OB monitors:




Have any more pics, they look interesting..

Early B.

Re: Lets see your O.B. speakers....!
« Reply #157 on: 25 Nov 2015, 04:49 am »

ThePriest

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Re: Lets see your O.B. speakers....!
« Reply #158 on: 25 Nov 2015, 07:48 am »
If you've never done one before, I recommend doing a project that someone has debugged, and that's technically sound - either one of Martin King's, or the Manzanita or ... (senior moment ... there's another one AC)

Perhaps Matevanas Hestia OB projects?

/The Priest

bdp24

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Re: Lets see your O.B. speakers....!
« Reply #159 on: 25 Nov 2015, 10:00 am »
If you're using a passive crossover, the woofer should have high (>.7) Qt - which is why the Eminence Alpha 15a is used so often.

You can use whatever you want for the midrange and tweeter; but if the tweeter isn't open-backed, that will effects your radiation pattern.  (Which can be bad or good - it really depends on your goals - but probably explains why so many designs use wide /full range drivers)

The woofer should be at least 10db more efficient than the other drivers, to compensate for baffle step loss.

If you're using active crossover/digital eq, pretty much any drivers can be made to work.  Just make sure your woofer has enough xmax and power handling.

I can't recommend Martin King's quarterwave.org site enough - his articles are well written and the MathCad worksheets are phenomenal.

Once you have the bass sorted (ie, your woofer is efficient enough, or you're using multiple woofs) then normal speaker design goals apply: low distortion, flat frequency response, smooth off-axis response (a big weakness of designs that use wide band drivers, alas), etc etc.

If you have the space, dipoles are wonderful.  I like Magnapans, but they need lots of amp.  I like Quad ESL 57s, too, but they're also hard to drive, and don't play loud.  I just built Martin King's Fostex Fe103/Eminence Alpha 15a project, and like a lot of what it does (I need to make a few changes to it after the holidays before rendering a more definitive verdict). 

If you've never done one before, I recommend doing a project that someone has debugged, and that's technically sound - either one of Martin King's, or the Manzanita or ... (senior moment ... there's another one AC)

An alternative to Maggies is the Eminent Technology LFT-8b. It is also a magnetic-planar dipole (above the 1st order 180Hz x/o frequency, below which a sealed 8" cone woofer provides bass), but needs less power and is more tube amp friendly, both a result of being an 8ohm load rather than the Maggie 4ohm. It is also different from the Maggie in being a push-pull design, with magnets on both sides of the diaphragm. And Danny Richie's OB/Dipole sub can easily be substituted for the ET woofer (or used as a woofer for Quads), for a full-range OB/Dipole loudspeaker at an affordable price.