First OB with vintage Seas

[djn]

The Eminence 15A sound really really good in "H" frames -- to my ear -- and do not cost that much. Combine those with what you have and I think you would have a strong, open, and detailed system.

[zmyrna]

Okay, this is what I am listening now (see pic).
(Well I am actually listening to Molvaer's Solid Ether)
I used to boxes to increase baffle size and now there is a lot of bass, everything seems balanced. It is lovely actually. I have this brace in the middle of the open baffle in the back and because of that there is a bit of resonance.
I have been thinking about way forward:
1. adding subs won't be practical; i am short of space
2. because i am using 4 woofers the cones hardly move: there is potential to get more out of them
3. i am still liking the idea of using a very low 1st order on the woofers to flatten the rising open baffle bass response (as in Manzanitas and OB project on Supravox website)
So here is my plan:
Instead of current 8" woofers I will use the 10 inchers which I already have (4 on each side). On a flat baffle 4x10" would be too high. So I am thinking of an M frame (MM in this case). And most importantly I will try to go active on the woofers. With the low crossover the main problem is SPL. And going active can solve this without adding new problems (such as wings and resonance).
I think the woofers can be pushed much further in this set up.
I am looking into Behringer Inuke DSP pro digital amps for this purpose. If only I can figure out how to integrate volume control.
Thoughts? Does anyone have experience with Inuke DSPs?
BTW I was sceptical on OB bass after the first impression but I am loving what I am hearing right now. OB shines on vocals too.

[Pano]

Glad to see you got it sorted! More baffle area sure does help. Side wings help, too.

I just saw th Berhinger amps at trade show, but have no idea how they work. How much DSP do they have?

[zmyrna]

Okay here is the next step.
I will keep the mids and up as it is: open baffle.
And put the woofers in a separate closed box.
I will chop the woofer section of the open baffles and they will sit on top of the bass box isolated by sorbothane feet.
Bass section will be using two 10" vintage SEAS woofers per side.
At 8ohm each and wired parallel, it will be a 4ohm load.
This should give about 96db efficiency in the bass region, hopefully.
Bass box will be with no vents and about 3 1/3 cubic feet of internal volume.
I am thinking of lining the interior with wool carpet, and the walls except the front baffle will be filled with sand and supported by a single brace in the middle.
Front baffle will be 2 layers of 18mm plywood.
Rest of the walls will be a sandwich of 18mm mdf, 15mm sand, and 9mm mdf.
I bought the wood and sand last weekend and am ready to roll with my jigsaw.
Any comments before I start?
*yes, I wish I had a router...

[Jack Caldwell]

Originally Posted by djn

The Eminence 15A sound really really good in "H" frames -- to my ear -- and do not cost that much. Combine those with what you have and I think you would have a strong, open, and detailed system.

Also in just plain Open Baffle. Have a look at what can be done with the Eminence and the DaytonPS220.... granted, I'm extensively using DSP and using some very complex combinations of filters to effect Timbral Correction on the system, but this gives an idea of what can be achieved.

[zmyrna]

Here is my latest experiment:
An H-frame with 4 Seas alnico 10"ers (same woofer used in the legendary Dynaco A25). Low passed 2nd order with 10mH and 100uF.
Lets first talk about the bass.
It is still somewhat weak. But very clean too. My biggest complaint: lack of dynamics compared to mids.
At higher volumes bass becomes visceral - you start feeling it in your body - which is very promising to stick to OB. Dynamics improve a bit too.
For next step to improve bass dynamics, what should I do?
- keep current driver set up and switch to active CO/biamp on bass section
- or keep passive and switch to 2 15" pro audio woofers (high eff, cloth surround + light paper cone)

Now more info on the upper section:
3 way with
Seas 8"
Seas 4"
B&G Neo3 PDR
Cross over is a very old 3 way Seas board (2000/5000) to be updated later on

[zmyrna]

it is not clear on the picture but the upper section is fully open baffle too.
Bubble wrap in between for isolation. H-frame do indeed rattle a lot in spite of bracing.

[Rudolf]

Probably you haven't fully exploited the potential of that H frame yet. Before investing in another set of drivers you should biamp your dipole, but keep the passive crossover for the H frame. Reverse two of the woofers (diagonally) on the baffle, looking at their baskets. And put massive vertical and horizontal bracing between the drivers to stabilize the baffle and the frame walls. The bracing you show in your picture doesn't deserve its name .
Put a MASSIVE weight on top of the H frame to keep it from moving back and forth. I think about one or two 40x40 cm concrete slabs.

Rudolf

[zmyrna]

Thank you Rudolf.
There is more robust bracing in the back actually
But adding mass is very good idea.
Sand, concrete or plasticine I am thinking.
Buying a new amp would cost me more than new PA drivers though.
I am thinking of buying the drivers for one side to test first.
These Chinese drivers are very cheap here:
SoundLab :: SoundLAB 15" Black High Quality 400 W Bass Speaker (8 Ohm) 35.39 IN STOCK (18 Oct 2012)
Two of those per side should be more efficient than the current set up.
I have a suspicion that rubber surround drivers can never be as dynamic as fabric ones.

[StigErik]

An other trick is to suspend the box/h-frame. Either by hanging it by wires from the ceiling, or use a very soft suspension between the floor and the box. I use small tire tubes with light air pressure, it works very well.

The point is to lower the pendulum resonance frequency of the box itself. The lower it get, the less will the box move.