MY own OB speaker project

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Nick
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Re: MY own OB speaker project

Post by Nick » Mon Nov 06, 2017 11:43 am

I would guestimate, that the OB's I have, suffer from the response and problems of the FE167E, but I have got used to those, so it doesn’t worry me, the Monacore is I think probably a better solution and more neutral, and not so directional. I thing the Beta 15 in the much bigger baffle with large side wings gives a better bass extension, and by doing that, I would say probably better bass qualities.
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Re: MY own OB speaker project

Post by IslandPink » Mon Nov 06, 2017 11:44 am

Fair enough.
Have you ( Colin ) got a link to the horns ? - I've only seen a picture. Would be interested to know the expansion frequency.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: MY own OB speaker project

Post by MJK » Mon Nov 06, 2017 11:59 am

The low fs and relatively low Qts of the 15" woofers being used is going to make it difficult to get a flat extended bass response. The baffle is rolling off the low end below 100-200 Hz at 6 dB/octave combining with the woofer rolling off due to the Qts, the lower you go in frequency the more the bass output will be down. You are going to need a well designed crossover and a lot of boost/EQ to get decent deep bass output even with a larger OB width, I faced the same issues with my AE Dipole 15 woofers. Have you simulated the design to see what is going on with the bass and what crossover and EQ you need to apply?
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Re: MY own OB speaker project

Post by chris661 » Mon Nov 06, 2017 12:09 pm

FWIW, when I tried an OB with a low-Q 15", I needed 27dB of boost to get flat to 25Hz. Fs was around 40Hz. Lots of excursion needed, but it was some of the best bass I've heard anywhere. Likely because the room wasn't being excited as a monopole would.

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Re: MY own OB speaker project

Post by Toppsy » Mon Nov 06, 2017 12:48 pm

IslandPink wrote:
Mon Nov 06, 2017 11:44 am
Fair enough.
Have you ( Colin ) got a link to the horns ? - I've only seen a picture. Would be interested to know the expansion frequency.
http://www.monacor.co.uk/categories/hor ... nr/128420/

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Re: MY own OB speaker project

Post by The Stratmangler » Mon Nov 06, 2017 4:32 pm

I'm a bit late to the party, but first off, thanks Colin for arranging the get together - it was great to see everyone, and a good time was had by all.
Special thanks to the catering dept. (Lynne) too - despite having other arrangements and being elsewhere she had prepared sustenance for the troops in advance, which more than hit the spot.

I rather enjoyed the way that further improvement was wrought from the coaxial driver variant of the OB.
Sometimes the glaringly obvious gets overlooked, and Nick identified one area that might be improved on immediately, and that was to reduce the effects of rear reflection on the coaxial mid/bass driver by simply pulling the baffles away from the rear wall.
Pulling them forward did indeed clean the mids up.

The next bit entailed improvising side panel extensions, to try and improve the bass response of the 15" drivers, and it's surprising what can be accomplished by positioning LP sleeves in strategic places.

Lots of music was played and enjoyed, and it was only when a piece with a Mark Tree https://en.wikipedia.org/wiki/Mark_tree in it, that thoughts turned to the upper end of the tweeter response.
Colin's Fostex supertweeters were pressed into action, and integrated into the speaker array.
Once levels had been properly sorted out there was much more music played, and enjoyed by all. I'm talking full CDs being played.

The strongest point of the coaxial driver is its ability to bring detail to things in a mix that have always been there, but are generally masked to a greater or lesser extent by other speakers.
This was brought right home with a couple of tracks from the Bob Marley & The Wailers "Legend" CD.
"No Woman, No Cry" is a live recording, and there is a heightened sense of being there in the audience.
You hear the murmuring of people around, and their singing before the singers on stage begin.
The female backing singers, “I Three” were only two on this recording, and their close part harmonies at the start were very apparent, and very ably rendered.
Another song, “One Love/People Get Ready” has a piano in the intro, but it’s so well defined that you can hear it to be a cheap upright of the type most of us probably grew up hearing, in pubs, schools and church halls, one of the wooden framed pianos that have that “not quite there”, slightly discordant and slightly woolly quality to them.

The thing is the coaxial drivers have, to my ears, a very special cohesion and capability to them.
Much more good music was played, usually full albums, from start to end.

When one of the supertweeters fell off the top of the baffle (well, they were only held on with BluTack), it, and its partner were removed, and things still gelled.
As has been said, the supertweeters were the icing on the cake, and the remainder of the listening that night was without them.

For me, the OBs in this guise sound excellent, and they just play music in a very capable, involving and rhythmical manner.
They go down deep, and reach up high, and nothing stands out as being glaringly wrong in between.

I like ‘em a lot, but there is a downside for me. They’re too bloody big to live with in a tiny terraced house.

I'll post up a bit later about the compression tweeter experiments later.
Chris :happy3:

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Re: MY own OB speaker project

Post by Andrew » Tue Nov 07, 2017 8:25 pm

Everything everyone else said +1, except to add my thanks to Colin (and Lynne) for hosting an excellent weekend.

Those co-axial drivers are every interesting......
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Re: MY own OB speaker project

Post by Toppsy » Sat Nov 11, 2017 9:17 am

Some further minor upgrades with the 3-ways.
Yesterday I drilled holes in the centre baffles and installed the T90A super tweeters. I machined the holes such the tweeters would be gripped in place with 3mm thick 'O' rings. For those that can remember the Sachiko speakers I built for Andrew, Phil machined him some aluminium cover rings for his T90A's for this build. Phil did a most splendid job on these and were the finishing touch to the mounting of the tweeters. Now as it happens Phil machined up 4 cover discs and Andrew has promised to root out the spare pair he has for my baffles.

Image

Image

Image

As has been comments earlier this really is just the icing on the cake and lifts the sound another level. Augments bass a little as well so a win, win modification.

Scott has been away up in the lakes this last week and in conversation with him says there is a way to duplicated the miniDSP filter experiments we did for the horn loaded 2-way, passively. So that's next for these version of the OB's.
CAD drafting of the wider side frames and deeper base are in progress. Just need to find the time to make up the templates and then order the ply and machine them up.

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Re: MY own OB speaker project

Post by Dave the bass » Sat Nov 11, 2017 9:55 am

Phwwwwwwwwwwwoooooooooooaaaaaarrrrrrrrrrrr! Nice team-effort.

Like, plus wun, thumbs up etc etc.
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Re: MY own OB speaker project

Post by Cressy Snr » Sat Nov 11, 2017 10:59 am

An exemplar of shoddiness.
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Re: MY own OB speaker project

Post by IslandPink » Sat Nov 11, 2017 11:39 am

Nice work !
So is that the coax unit in the middle with the tweeter ? Does the HF bit fire through the big dustcap ?
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: MY own OB speaker project

Post by Toppsy » Sat Nov 11, 2017 2:31 pm

IslandPink wrote:
Sat Nov 11, 2017 11:39 am
Nice work !
So is that the coax unit in the middle with the tweeter ? Does the HF bit fire through the big dustcap ?
Yes Mark, and the horn does fire through the large centre dust cap. Monacor don't appear to publish a lot of data regards the design of the units but what they do publish can be found here: http://www.monacor.co.uk/categories/pa- ... nr/102200/.
They also do a 12" version: http://www.monacor.co.uk/categories/12-3/vnr/102240/
and an 8" version: http://www.monacor.co.uk/categories/pa- ... nr/102110/, but I have not heard any these so cannot comment on them though it would appear from the spec sheet they all use the same compression horn driver.

You're most welcome to pop over and have a listen when you fell well enough from your stomach bug issue. I can easily separate the coax driver from the super tweeter and bass drivers so you here the coax on it own on the baffles.

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Re: MY own OB speaker project

Post by Toppsy » Sat Nov 11, 2017 7:55 pm

Toppsy wrote:
Sat Nov 11, 2017 2:31 pm

You're most welcome to pop over and have a listen when you fell well enough from your stomach bug issue. I can easily separate the coax driver from the super tweeter and bass drivers so you here the coax on it own on the baffles.
The invite to pop over to Topps Towers and have a good listen to these speakers is of course extended to all who perhaps have a passing interest in building some OB's and can't wait until the next Owston meet. Since I am now noted on the Monacor web site as one of their UK dealers I can offer you very good prices on the drivers used in these OB's or any the Monacor products.

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Re: MY own OB speaker project

Post by Ray P » Sat Nov 11, 2017 11:39 pm

Thanks for broadening the offer Colin, I would definitely take you up on it but from Somerset it's a long way so not something to be easily undertaken.

I'm really interested in this project and very tempted but for one problem I perceive; I only have around 1.5watts per channel available from my Transcendent amps!

Let's see how it develops...

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Re: MY own OB speaker project

Post by Andrew » Sun Nov 12, 2017 12:27 pm

Toppsy wrote:
Sat Nov 11, 2017 9:17 am
Some further minor upgrades with the 3-ways.
Yesterday I drilled holes in the centre baffles and installed the T90A super tweeters. I machined the holes such the tweeters would be gripped in place with 3mm thick 'O' rings. For those that can remember the Sachiko speakers I built for Andrew, Phil machined him some aluminium cover rings for his T90A's for this build. Phil did a most splendid job on these and were the finishing touch to the mounting of the tweeters. Now as it happens Phil machined up 4 cover discs and Andrew has promised to root out the spare pair he has for my baffles.
Would send them down so we could all see the finished article, assuming I could find them both, I can only find one so far :(
Analogue, the lost world that lies between 0 and 1.

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