First OB with vintage Seas

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Perhaps you could float the centre baffle board...
Reverse two diagonal drivers as suggested before, for both weight distribution and distortion.
Suspend from top of cabinet and fill gap with soft flexable filler.
 

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zmyrna have you seen OBL11
I have the same 10" drivers as you, and 8" cloth suspension as well as many of those 1.5" cone tweeters. My plan is to build something like the OBL11 but use the 4x 10" instead of the 15" and merge with the xover of BLACKCONES

I built a H-frame for the 10" units and noticed a lot of vibration to my surprise. Spending a thought on the problem it obvious that the pressure differences across the frame is as high as in a closed box ( above high pass) and as much motion induced vibration and this into a structure that has less intrinsic bracing than a box structure. So when I will build the baffle mass and braces will be prominent!
 
Here is the background of my speaker building story and my goals:
I have severe tinnitus and am very sensitive to upper mid and HF distortion / ringing.
Several years ago when I first put my hands on an Oskar Heil Syrinx by chance, it was a big revelation. The dipole AMT tweeter was cleaner, more open and more dynamic than the dome tweeters I have had before.
Since then, the dipole AMT kept growing on me while the shortcomings of the slow 7" woofer became more apparent.
I became convinced that the openness and dynamics need to be extended to mids and bass.
 
@DrBoar
I am so glad to hear that you have the same drivers and plan a similar design.
I really love those blackcones and my initial plan was to build an all blackcone dipole.
10" Seas 25TVs are very well regarded (Dynaco A25). But after having them up and running on a prototype, I think they are not efficient and dynamic enough for my build.
They might bland well if you go active with Eq and combine them with rubber surround mids (as in Nao Note and Orion).
Each 25TV is around 90dB/1w. Two would make 93 and four 96dB/1w. We need 8 per side to reach 99dB/1w. Correct me if I am wrong.
To start with a 90dB woofer on a passive OB is a loosing proposition.
One can get 99dB with just one pro 15" woofer.
Two 15"ers even better: higher eff plus second woofer on top would lift the center of bass higher (closer to mid driver and ear level).
My next prototype will use two cheap 15" pro woofers per side.
At 98dB each, they would make 101dB in series.
It would also make a 4ohm load and add another 3dB in total eff (104dB). Again, correct me if I am wrong.
I also plan to move to U baffle instead of H. Resonant peak of U baffle would be easier to deal with. You pay for the additional freq extension of H baffle by a further reduction in efficiency anyway.
Good that you mentioned OB11. I also plan to use a similar lowpass filter to that of Troels'. Visaton NoBox crossover is another example. I did not know that a 1st and 2nd order filter can be used in tandem until recently. I think it is a very elegant solution to the falling bass response of dipoles. But it requires massive efficiency in a passive bass set up.
 
As I have mentioned earlier, I am becoming more suspicious of high excursion, rubber surround, heavy coned mid or bass drivers (most modern drivers).
I think even a light paper cone becomes too heavy to operate with a rubber surround.

For good dynamics, large diameter and light paper cone with fabric surround is probably the way to go.

Unfortunately large vintage alnico drivers are a few and not easy to find (hence the high price).
 
@ Stig & Silent
I am thinking with soft suspension we run the risk of turning the whole panel into a diaphragm.
I will try mass and dampening first.
Sand or plasticine (think playdough) or both.
Plasticine can be used to both dampen the panels and fill the corners and angles (less parallel surface to resonate).
 
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@ Stig & Silent
I am thinking with soft suspension we run the risk of turning the whole panel into a diaphragm.

Look at the weight ratio between the moving mass of the loudspeakers and the weight of the baffle. If we have a 1:100 ratio, then the baffle - if completely suspended - will move 1/100 of the speaker cone. Or -40 dB. Not a big problem in my opinion.
 
The good thing about the Seas in OBs is that they are quite! If you send a 20 Hz sinus thrugh the Seas unmounted it simply swings back and fourth say +/-3-5mm making no sound. Doing the same with quite a number of drivers will make you listen to strange hummings and buzzing sounds probably from the rear suspension acting up.

I might get hold of four additional seas10" drivers so that I will have 6 per side...

Some years ago I listened to the HFN &RR garage door track on the Audiotronic Megatrend that had 18 KEF B200 8" per speaker in open baffles roughly two meter high and perhaps 0.8 m wide. The sheer power of 36 eight inch drivers slamming was an experience. Something like mating Quad ELS with the impact of Klipsch corner horns.
 
zmyrna: one driver 90db, two in parallel 93db, four in series-parallel 93db also. Series wiring liberates zero gain in efficiency. If anything this makes the case for a single high efficiency woofer much stronger.

These reasons are why i have considered a Mivoc 18, fs 38hz, xmax 4mm, 98db/W. I wanted to ensure i had enough headroom to eq the bass without xmax excursions.

Even better, two 18s in ripole or slot loaded OB, total of four 18s. 101db/W plenty headroom ;)
 
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Ah... two drivers in parallel means +6 dB voltage sensitivity, at the cost of half the impedance. Two drivers in series means no gain in voltage sensitivity, but double the impedance. Four in series-parallel is +6 dB voltage sensitivity and the same impedance as one driver.
 
I ran into a similar problem with woofer sensitivity. 4 woofers wired in serial-parallel is not a good idea for OB. Since I am doing a multichannel-amplified project so I added an extra amp channel. 2 amp channels each driving a pair of speakers wired in parallel will give you a good boost in sensitivity. Of course you need to make sure the amps can handle the lower impedance.
 
After giving it a good rethink,
I am moving towards active.
At least for the bass section.
nanoDIGI from miniDSP should work for me.
It is a 1 digital in, 4 digital out DSP.
Ultimately I can use a nuForce or Wadia power DAC for the upper section,
and my Tact digital amp for the bass.
I will see how the 4x10"s behave in that set up first.
 
Thanks for clarifying series/parallel SPL issue.

@DrBoar
Thank you so much for the measurements. For some reason I was unable to find them on my web searches. 25TVs seem to be less efficient than I have assumed. On the positive side, they have arguably the ideal qts for open baffle. I wonder whether it will be possible to get enough LF dynamics by feeding them enough power. That is what I will try to find out next. Low mms is making me hopeful.

We should start a blackcone fan club.
 
MM OB bass: still not happy

here is another prototype.
3 way active with miniDSP nanodigi.
CO points 250 and 3000, LR4 and EQ.
waveguide experiments on M and T.
MM topology for bass.
moving from 4 way to 3 way was a step backwards.
in an active OB set up like this (similar to SL and JohnK designs) 3 way is not optimum. SL and JohnK think it is because of dispersion problems at the CO point bw M and T.
I suspect there might be another component. narrow M baffle means we need EQ at the lower end of M. and I think EQ at that area might be negatively effecting the upper end of M (1000-3000hz).
in my next prototype I will be crossing the 8" cone to a neo8s around 1k.
another problem area is the resonances in the bass section, even with steep active CO and EQ.
so no wings or h frame in the next project. it will just be 4 10" woofers on a small square baffle. I think those W have enough excursion and the bass will be enough with active and EQ.
 

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I am ready for my next project.
Please help me select one of the following designs (all active CO with miniDSP) :

Option 1
(4 way)
>5000hz B&G Neo3 open baffle
800-5000hz B&G Neo8s open baffle
100-800hz 2x Seas 21TV-EW open baffle
http://vintagehifi.dk/forum/viewtopic.php?f=565&t=2622
<100hz 4x Seas 25TV-EW ripole
http://vintagehifi.dk/forum/viewtopic.php?f=565&t=2609

Option 2
(3 way)
>5000hz B&G Neo3 open baffle
800-5000hz B&G Neo8s open baffle
<800hz GPA 416-8B sealed box
add subs if I move to bigger home

So the basic Q here is which low-mid section would better match the dynamics of planar highs.
I already have all the drivers and amps and the miniDSP (nanodigi).
 
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Here is a graphic representation of the two projects in my mind.

As you see, upper two ways (>800Hz) are identical for both.

The difference is in the low mid-bass.

And the question is, which low mid-bass option would be more dynamic to match the planars.
 

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My vote is for:
Option 2
(3 way)
>5000hz B&G Neo3 open baffle
800-5000hz B&G Neo8s open baffle
<800hz GPA 416-8B sealed box
add subs if I move to bigger home

But put the Neo8 upright, not sideways. If sealed you will need a sub without a doubt. The GPA 416-8B is a low Q driver, so sealed it will have almost no bass. Port it and even then you might need a (very good!) sub.

Deon
 
Deon, thanks for your response.
Planar section of the speaker will be modular and will be optimized later on.
I will experiment on neo8 and neo3 with orientation, foam pads and waveguides.
Let's leave that discussion for now.

The subject of my recent post is matching planars with cone drivers.
I have presented two options:

One is high(ish) xmax drivers on open baffle with equalisation to combat OB cancellation.

Second is high SPL driver in sealed box.

First would be a good match for openness, and second for dynamics probably.

I am considering trying the sealed box option first because it is more straight forward.

I was hoping that I could do without subs because I do not even have the space for them.

(I have a pair of Faital Pro 18" woofers begging to be turned into subs though)

I should run the winISD to see if a bit of bass boost would be enough with the sealed box.
 
Okay,
Here is the latest design.
Crossover points likely 200 and 1000Hz.
Neo8S will have Raal foam pad treatment for vertical dispersion.
Option of adding supertweeter and monopole subs later.
For my little room, I am hoping to have enough bass with DSP dipole correction though.
 

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