[MJK]

I'm just getting MJKs worksheet for the H frame and OB combination.

Rudolf,

How are you getting the worksheet?

Martin

[Rudolf]

Rudolf,
How are you getting the worksheet?

Martin,
by sending you the money, of course! Should arrive next week. My PayPal account gets filled up over the weekend. Did I use "just getting" in a wrong way?

Rudolf

[jhm731]

Rudolf-

Thanks for the fast reply.

I'm going to take some measurements tonight.

Dan

[MJK]

Did I use "just getting" in a wrong way?

No, I just wanted to understand what you meant. I continue to have problems with some shady DIY users.

Martin

[evozero]

Hi Rudolf,
The curved red line was what i meant for the curved side panels. I am going to use them to be the side of the H frames as well. This will save wood, for each speaker i will only need;
2 x side panel
1 x front baffle
1 x beta 15" square baffle
1 x H frame top
1 x H frame bottom.

The parts are ordered, i bought the closest  component values i could.
the only differences were the Jantzen Inductance: 1.50 mH,  DC Resistance .67 and one resister is 4.5Ohm.
Ok i am off to the garden, get the saw out!
Cheers
Ian

[MJK]

Ian,

My advice would be not to mount the OB at the front of the H frame. It will work better mounted above the woofer driver about half way back on the H frame.

Martin

[evozero]

Hi All,
I have been busy,take a look...


This allowed me to try out the narrow front baffle, without hacking up the existing baffles.
The outcome is the Dipole effect is much more obvious, before the wall reflections were being stopped by the wide baffles.
So narrow baffles it is!
Martin, would you please elaborate on the baffle position. I was taking / stealing the layout ideas used by GR research super v or v2 models, I think aesthetically speaking, my wife is much more inclined accept a clean front baffle.
She asked me if the Beta could be mounted on the ply front baffle as it is now, I said I would ask the forum if I am allowed and get back too her 
Could I put the beta frame on the back without compromising bass too much?
Thanks
Ian

[MJK]

Martin, would you please elaborate on the baffle position. I was taking / stealing the layout ideas used by GR research super v or v2 models, I think aesthetically speaking, my wife is much more inclined accept a clean front baffle.
She asked me if the Beta could be mounted on the ply front baffle as it is now, I said I would ask the forum if I am allowed and get back too her 
Could I put the beta frame on the back without compromising bass too much?

Ian,

I don't post on this forum any more. But I will try to answer your questions and then move on. I still post occasionally at DIYaudio or more frequently on my own Yahoo group (linked from my web site).

The biggest challenge with dipole speakers is achieving enough bass output to match the midrange or full range driver's SPL/w/m. This is paticularly true of passive crossover OB systems.  When you move the OB with the AN driver to the front of the H frame, you are pulling it closer to the listener then the Beta driver in the H frame. The apparent efficiency of the AN driver will rise relative to the bass output from the Beta. That is the biggest problem I would be concerned about.

If you want the AN and Beta drivers on the front of your dipole speaker you might consider using a U frame on the back of the Beta, this will allow a single baffle concept. There are a couple of dipole articles and two dipole speaker designs on my site that might help you since thay are similar to your concept.

Martin

[Rudolf]

Martin,
both drivers have their own amplifier, so differences in the output would be no major problem. Would you have concerns regarding the symmetry of the FR OB relative to the front/back terminal of the H frame? How about reversing the Beta 15 in the H frame? This would bring the front pole plates of both drivers nearer together than the conventional approach. Look for the numbers, not the distance in the drawing:



Rudolf

[jtwrace]

Rudolf

How do your speakers sound?  They are very intriguing.  Which model is the overall performer?

[THWO]

Interesting project. Keep going - and us informed...

[Rudolf]

Hi Ian,
any progress, decisions, questions? Or are you just waiting for the PE parts to arrive?

Rudolf

[evozero]

Hi All Rudolf,
Sorry for not getting back too you, work and real life keep getting in the way!
My wife gave me her input, she likes the idea of having the front baffle as the single piece of birch ply with the beta mounted OB below. Also likes the baffle slightly raised off the floor so they look like they are floating slightly.
That's why i asked about the U frame. But I have ordered the PE parts,as you suggested.
Would a U frame with GR style side panels be possible with the values ordered, if not i will go a head with the H frame?
Might be a compromise for the wife?
Thanks Again
Ian

[Rudolf]

Hi Ian,
no prob with real life getting in the way. I just wasn't sure, whether MJKs posting had brought action to a halt.

When I saw your opening post, I knew that looks would be an issue. I really like the decor on those baffles. So I am prepared to look at things with aesthetics in mind. But first to the filter parts: As long as you keep the 40 cm width down to - at least - the center of the AN (I prefer the bottom), the values don't change. If the Beta is mounted on the OB, a U frame or H frame has a minor impact only. And raising the baffle up to 5 cm (max) from the floor would be no issue either IMHO. 10 cm might be critical though.

There are three options to discuss:
1. you may mount both drivers on a plain OB. No problem for the AN, but the Beta 15 will be really bass shy. It needs to be EQed quite a lot and will run out of excursion at anything but modest levels.

2. U frame. Should work as well or even better than a H frame at half the depth - if done right. To do it right means to put some damping into the U frame. And that's were I can't be of any help. I haven't done U frames and I'm under the impression that it is difficult to do that damping right without measurement control.
For a U frame you would need to get some better qualified help - possibly from Martins Yahoo forum?

3. H frame. With both drivers driven by separate amps I see no problem to match them. My personal experience with 3 different H-frame-plus-OB configurations did not suggest any problem when moving the OB to the front of the H frame.
Obviously the H frame will need some sort of opening in the plywood baffle. But you can cover that opening with any sort of air permeable cloth you like. You can even make it a circular hole in the plywood baffle with the size of the Beta 15 instead of a square. Same applies to the U frame btw.

Last not least those side panels: I believe you are thinking along the lines of the Super-V. If you could refrain from starting the panels at the baffle top and limit their top end to the height of the AN center, I could live with it.

Tell me what SWMBO thinks about it. 

Rudolf

[Danny Richie]

Sorry, I am a little late coming to this thread.

I have been there done that already with all of this stuff and know what you are up against. If I would have caught this thread earlier I would might have saved you some trail and error lessons. Sorry...

I also have measured and tested it big brother the Super 12 in open baffle application. So I have a good idea of what you are up against there.

First off, get your baffle size down as small as possible. The surface reflections of a wide baffle will kill your imaging and any transparency aspects of the sound stage. All will sound as if it is playing from the baffle forward.

If you need to, turn your lower woofer sideways so that it doesn't add baffle width.

Try something like this:



Also, I would highly advise against a U shaped frame. Most utilize them with no bracing at all. Then the panel size is such that they flex and resonant wildly. At least the H frame breaks the panels down to half their size. That helps a lot, but can still be a problem. Even a friend of mines Orion's allowed a LOT of low frequency coloration due to panel flexing and resonating. I used 1.25" thick side panels on the Super-V and it still needed to be lines with No Rez to kill the resonances completely and provide a solid bass response.

Another thing that I saw in this thread that was a red flag was this compensation network for the Super 8.



Do NOT use a resistor at the front of the network allowing a full range signal to pass through it. With very little power on it at all, it will burn up in smoke and flames.

[evozero]

Hi All,
A really big thank you to Danny for the input. I think it is very impressive that you share your knowledge with us, makes your kits very attractive to potential customers. I am one of those. If in the UK we didn't get get beaten over the head with tax, import duty, weak pound and shipping i would have just ordered a V2 kit. All the issues ironed out, a happy chap i would be.
For now I just want to get the best from these drivers and try and keep the wife happy, not easy.
Rudolf's idea of using cloth to cover the h frame is a great one, don't know why it didn't occur to me?
SWMBO will be pleased 
Back to the speakers, so if i understand thing correctly i should aim for a H frame for the Beta, and a small baffle for the AN using the side panels to hold the AN baffle at the correct height. But the side panels only reaching up to the centre of the AN max. 
Did you find the rounded top baffle made a difference with the AN drivers?
The crossover for the AN is just the cap followed by the resistor, and i think Rudolf meant keep this configuration and add the other components?
I have never heard of No Rez, can you buy it in the UK?
Thanks for now, i am hoping to to do some sketch up and post back soon.
Ian

[Danny Richie]

Did you find the rounded top baffle made a difference with the AN drivers?

It gives less surface reflections.

The crossover for the AN is just the cap followed by the resistor, and i think Rudolf meant keep this configuration and add the other components?

In that case then the resistor might survive.

You might also want to drop out that 47uF cap that by-passes the other resistor and the inductor. That will just let the top end shoot up. It already has a naturally rising response in the top end that you'll have to tame.

No Rez damping material: http://www.gr-research.com/index.asp?PageAction=VIEWPROD&ProdID=103

[Rudolf]

Danny,
this thread began as an effort to get rid of the laaarge panel you can see in post #1. What we have arrived at is certainly not the best you can do with the AN Super 8, but a reasonable compromise which hoped to keep the original baffle cut-outs in use.
Things have changed - when do we ever really land at the exact destination, where we headed to at the start - but within the constraints of the Beta 15 and a normal plate amp I have no better solution to offer.



You see simulations for the on axis response of the proposed H frame and OB combination. They are made with the worksheets of MJK (top) and with Boxsim (bottom). Boxsim can't do H frames - I tried a reasonably large OB instead. For the dotted line I omitted all filter components except the 4.6 Ohm resistor. So you can see what I tried to achieve with the filter.
I know that my sims don't care for the rising response above 1 kHz, but I would compensate for that by listening off axis.

Rudolf

[jhm731]

Sorry, I am a little late coming to this thread.

I also have measured and tested it big brother the Super 12 in open baffle application. So I have a good idea of what you are up against there.

First off, get your baffle size down as small as possible. The surface reflections of a wide baffle will kill your imaging and any transparency aspects of the sound stage. All will sound as if it is playing from the baffle forward.

Danny-

Spoke to your friend Mr.Dicks, and he says just the opposite about baffle size.

He says if the baffle is too narrow, there will be wrap around cancelation.

Here's a quote from him on OBs:

"In my opinion, one of our Audio Nirvanas, in an open baffle, is like putting a Ferrari engine in a Ford pickup truck."

Are there cabinet plans for OB in your picture?

Dan

[Danny Richie]

I know that my sims don't care for the rising response above 1 kHz, but I would compensate for that by listening off axis.

I tried the same with the Super 12, but that top end is extremely hot. And it made the overall in room response overly bright as well.

He says if the baffle is too narrow, there will be wrap around cancelation.

That is a good thing. The real effect of the narrow baffle is that it won't play as low. If you have a low frequency driver right under it then who cares? The surface reflections of a wide baffle is a much bigger issue.

Are there cabinet plans for OB in your picture?

Soon.