[irishpatrick33]

I have read a bunch of stuff on open baffles.

But I have not gotten a defiinitive idea as to whether or not EQ is required?

I am going to run a single full range driver on open baffle for each channel. I will either be using Visaton B200, Moth Audio driver, or EJ Jordan JX95S.

So is EQ required? Opinions? Pros cons?

[gainphile2]

Hi Patrick,

There is always going to be a dipole peak at midrange. This is around 4-6db and is very substantial. Without notch EQ the speakers will sound shouty.

The other EQ would be the bass rolloff compensation. This can be overcome with wings etc.

[markC]

Baffle step compensation and notch filter for the B200 IME. But, even with the notch I couldn't handle the top end.
So I cut it off at the knees with a cross over and let a tweeter handle above 2100 Hz. Now I like. aa Been running them this way for about a year now.

[Poindexter]

Gainphile, would you care to elaborate / explain about the 'dipole peak at midrange'?  I am unfamiliar with this effect.

Mahalo,

Poinz

[ttan98]

Try this site, J. K. explains it very well here:

http://www.musicanddesign.com/HybridDesign.html

note that it applies to 2 or more ways OB speakers.

[gainphile2]

That's a good site indeed, more practical than SL's

This is the long explanation, basically when you put a driver on OB, aside from obvious cancellations, there are summation as well. The 1st summation ("dipole peak") is usually the one we want to equalise.

http://linkwitzlab.com/models.htm#A

I found that this peak which is around 400-700Hz is very sensitive to hearing.

[Telstar]

My simulations tell me that the dipole peak depends also on the baffle size.

In your drivers list I will surely add the Hemp fr8/fr8c and raising the budget, the Supravox 215 signature bicone.

[gainphile2]

That's true. With my 5" Vifa the baffle peak is at around 700Hz with narrow baffle (19cm) and 500Hz with larger one (30cm).

Apparently this peak can be tamed by placing the driver off-center, but with the cost of poor off-axis response. Has anyone done measurement of MJK design (on and off-axis?)

[Telstar]

That's true. With my 5" Vifa the baffle peak is at around 700Hz with narrow baffle (19cm) and 500Hz with larger one (30cm).

Apparently this peak can be tamed by placing the driver off-center, but with the cost of poor off-axis response. Has anyone done measurement of MJK design (on and off-axis?)

I play extensively with edge and it is not only the width but also the baffle height ABOVE the driver that matters alot.
The point is: is EDGE baffle simulation accurate enough in this matter?
I'm asking because I got very good results with 8" drivers put in a narrow baffles (but not as narrow as yours, and considering wings). I tried 25, 30 and 35cm and both gave interesting results, with a specific W/H ratio.

One example with the FR8C in a 25x115cm baffle (height is VERY important, as i said), driver centered at 85cm from the bottom, 30cm from the top. Distance from the top is also very important, depending on the baffle width and driver size. Mic at 1,8m which is my listening distance.


As you can see, a wider and shorter baffle (40x95cm) it's not that much better. Make it even larger and there's a peak around 1200hz.

[irishpatrick33]

Well that is very disappointing. Needing an equalizer is pretty much a deal breaker for me.

I just wonder whether you guys have a tremendous ear and en EQ wouldn't be needed on somebpody like myself.

[Rudolf]

I play extensively with edge and it is not only the width but also the baffle height ABOVE the driver that matters alot.

Telstar,
it´s not really width or height that matters, but the wide and even distribution of the driver distances to the baffle edges. JohnK explains it in http://www.musicanddesign.com/Equivalent_Baffles.html.
You don´t need to understand all the math there. Just imagine to measure the distance from the driver center to the baffle edge every 1° of 360°. If all distances are equal, the driver is in the center of a circular baffle. The dipole peak (and dips) will be very pronounced. If the distances are spread over a wide range (the wider, the better), the dipole peak will be ironed out (on axis). 
There is a second aspect too: The distances should be evenly distributed. Not one half very short and one half very long, but all values in between too. Personally I achieve this for a full range application by cutting the baffle directly above the driver and adjusting the baffle width for the intended bass support.

The point is: is EDGE baffle simulation accurate enough in this matter?

AFAIK all simulation programs use the same edge diffraction algorithm by Backman. Just go to http://www.linkwitzlab.com/diffraction.htm and simulate his examples with EDGE. I found the results pretty convincing.

Rudolf

[Telstar]

Telstar,
it´s not really width or height that matters, but the wide and even distribution of the driver distances to the baffle edges.

Yes, that's what I meant and thanks for putting it with the right words.

JohnK explains it in http://www.musicanddesign.com/Equivalent_Baffles.html.
You don´t need to understand all the math there. Just imagine to measure the distance from the driver center to the baffle edge every 1° of 360°. If all distances are equal, the driver is in the center of a circular baffle. The dipole peak (and dips) will be very pronounced. If the distances are spread over a wide range (the wider, the better), the dipole peak will be ironed out (on axis). 

I read it again and now I understood a bit more

There is a second aspect too: The distances should be evenly distributed. Not one half very short and one half very long, but all values in between too. Personally I achieve this for a full range application by cutting the baffle directly above the driver and adjusting the baffle width for the intended bass support.

I think most OB designers do like you. But others put a hefty lenght above the driver (es. phy-hp OB).
But... besides off-axis response, if u look at the above graphs, to get a pretty smooth (albeit bit bumped) midrange from a bigger baffle (second graph), I had to off-set from center the driver.
You would suggest me to go for the centered version, instead, wouldnt you?

[mcgsxr]

There are a lot of folks around here with great ears that do use EQ, no doubt about it.

I have been using b200 Visatons run without any EQ or other passive components for years now.

I tried a cap and coil on trial from a generous AC'r here, but it did not float my boat.

The design of my baffles has differing distances to all sides from the offset driver.

I use an active crossover to carve out the 125Hz and down to my digital amp, and on to the helper 12 inch woofers.

The visaton sees 125Hz and up, pure and unadulterated.

I will admit that there is better treble out there, but I will also admit that 95% of the time I don't miss it.

It comes down the how musical it is in the current implementation, and that most of my music does not involve tons of treble energy.  On music that does have it, I can tell it is mising, but most of the time that does not, for me, detract from the musical presentation of the system.

I will continue to say that amp synergy is critical, especially when running full range.

There are tons of routes to audio Nirvana!

[ebag4]

Hi Mark, What active crossover are you using, was it the Reckhorn unit?  I don't see it listed in your system.

Thanks,
Ed

[mcgsxr]

It is the Reckhorn, yes.

I don't list it, because it gets too difficult to fit into a phrased description in my signature. 

I might ditch my existing sub amp (Bash300), and the Reckhorn Xover, and move to an all in 1 unit from Reckhorn...

[ebag4]

I was looking at their F1 unit.  Too bad it doesn't allow stereo subs, that would make it useful for FRs that need to be crossed higher where the bass is more directional.

Looking at their A-402 unit, that would fit the bill perfectly if it had stereo bass outputs.

Best,
Ed

[mcgsxr]

Agree about the stereo subs, but for me in my room, I don't find it an issue.

http://www.creativesound.ca/details.php?model=A401 - appears to be a nice solution, and one that runs at 2ohm for subs is nice.

I am currently using the F1, with a BASH300 amp.  It is good, but the BASH amp does not have an ability to cut out the built in Xover, so I sometimes worry about what is happening there.

My ears tell me it is OK, but my brain sometimes gets in the way!

Plus, as a user of mono subs (2, but looking to 4 in the future), the 2ohm capability would prove useful.

The price is certainly right for the 400 series Reckhorn goodies, and Bob at CSS has been great to deal with in the past.

[scorpion]

Irishpatrick33,

Look at the new Wild Burro FR Betsy and the Open Baffle proposed for them: http://www.wildburroaudio.com/speakers.php for a cheap try.
You wont be ruined and if you place the Betsys 32" up the midbaffle they will be flat down to 60 Hz and go a little lower without EQ.  The published FR-graph
is similar to that of  Visaton B200. There is a thread about them over at diy-audio where you could pick up some tweaking advice: http://www.diyaudio.com/forums/showthread.php?s=&threadid=139935&perpage=25&pagenumber=1 .
If you go this way please let us know your impressions.

/Erling

[Telstar]

Agree about the stereo subs, but for me in my room, I don't find it an issue.

I plan to use the Reckhorn and a separate stereo amp for the woofers.
Why not the 400? Because I'm afraid of it not having a soft start and therefore blowing my home fuse.
B1 + an Alesis ra300 cost about the same as the reckhorn 400...

The price is certainly right for the 400 series Reckhorn goodies, and Bob at CSS has been great to deal with in the past.

is the a402 stereo btw?
More feedback on these products would be useful to have

[scorpion]

We mustn't exaggerate the effect of the dipol bump. Mostly it will be 1-2 dB for a good designed baffle and in a frequency range (upper bass/lower midrange) where it will not be specially noticed in listening to music. It can also be used for crossover tuning as amply showed by MJK and a bit by myself in different designs.
It is another thing with broad peaks and valleys in the 1 to 3 kHz fundamental tone range which will give character to the sound of the whole speaker.

As I have shown sometime earlier Reckhorn F1 is easily (at least in theory) adapted to two channel bass output. Just look at the schema:



/Erling