Fertin project - calling all open baffle experts

[bcherry]

OK, Dice45 recommended making this an open discussion. I agree; here it is;

Fertin 20cm field coils installed in open baffles 120cm x 60cm x 5cm thick.

Voices are sublime, never heard anything like it. Midbass to treble has cracking dynamics. Very smooth response with none of the peakiness I've experienced with Lxxxxxxr.

But no bass below ~150hz. Any suggestions on open baffle placement/management/size? I'd be happy with 60-70hz with sound this clean.

BTW, speakers haven't been run in more than 2 hrs.

Cheers to all,
Brian

 

[Peter Daniel]

How did you get them?

 

[bcherry]

How did you get them?

TO, my old hometown! Any snow flying yet?

Got them from Fertin. Is that what you wanted to know?
Shipped by Airborne Express in a nice plywood box.

Brian

 

[Peter Daniel]

No snow yet and that what I wanted to know. I am seriously thinking about getting them too. How much were they?

And what exactly do you want to know?

 

[Steve Eddy]

Midbass to treble has cracking dynamics.

Usually when I think of things cracking, it's not good. But it seems you're using "cracking" in a positive sense. Am I correct?

I've been eyeballing the Fertins for a while now but there's such scant discussion about them so I want to make sure that what little I'm reading I'm interpreting correctly.

But no bass below ~150hz. Any suggestions on open baffle placement/management/size? I'd be happy with 60-70hz with sound this clean.

Your baffle seems a bit small to expect much in the way of bass. Also, how much current are you running through the field coil? That directly effects the driver's Q and would also have rammifications as far as bass response goes.

se

 

[Peter Daniel]

The dimension is 17'x18'x10'. Woofer is Focal Audiom 15'. I'm using electronic crossover at 100Hz. In room freq.response is -3dB at 25 Hz. However, I'm also using another 12' woofer on top with slightly smaller enclosure. My point is that the size of a baffle doesn't really have to be big. No frequency correction was required.

 

[Steve Eddy]

The dimension is 17'x18'x10'. Woofer is Focal Audiom 15'. I'm using electronic crossover at 100Hz. In room freq.response is -3dB at 25 Hz. However, I'm also using another 12' woofer on top with slightly smaller enclosure. My point is that the size of a baffle doesn't really have to be big. No frequency correction was required.

The effective baffle size is larger than your dimensions would suggest seeing as it's a folded baffle. It's effective size is more akin to a flat baffle measuring 37" x 38". Hell, slap one more side on it and it's infinitely large.

se

 

[planet10]

baffles 120cm x 60cm
....But no bass below ~150hz. Any suggestions on open baffle placement/management/size? I'd be happy with 60-70hz with sound this clean.

Actually i'm surprised you are getting that low with such a small baffle. If you are getting 150 Hz, doubling the dimensions of the baffle should give you 75 Hz. Keep in mind that the narrow dimensions is the dominant one in determining how low you go.

dave

 

[bcherry]

Re: Re: Fertin project - calling all open baffle experts

Usually when I think of things cracking, it's not good. But it seems you're using "cracking" in a positive sense. Am I correct?





Your baffle seems a bit small to expect much in the way of bass. Also, how much current are you running through the field coil? That directly effects the driver's Q and would also have rammifications as far as bass response goes.
se

'cracking', just like Wallace and Grommit. Yes, good, very good.

My mistake on baffle size: 80cm x 200cm

10V shows about 1.2A. Higher or lower doesn't make a whole lot of difference at this point.

Played another 4 hrs and the sound is getting even better.

Brian

 

[bcherry]

Re: Re: Fertin project - calling all open baffle experts

Actually i'm surprised you are getting that low with such a small baffle. If you are getting 150 Hz, doubling the dimensions of the baffle should give you 75 Hz. Keep in mind that the narrow dimensions is the dominant one in determining how low you go.

dave

Sorry, 'tis 80cm x 200cm
My mistake.

Brian

 

[bcherry]

The effective baffle size is larger than your dimensions would suggest seeing as it's a folded baffle. It's effective size is more akin to a flat baffle measuring 37" x 38". Hell, slap one more side on it and it's infinitely large.

se

OK, so extrapolating here: If I extend the top/bottom/sides 30cm 90deg towards the back wall, then I could expect a little more bass heft with no downside? Given the 60 x 200cm baffle, how much would I have to extend from the edges to get down to a clean 70hz?

How about placement for open baffles? They image like crazy no matter where I stand off axis. So far placement seems to have more affect on R-L channel balance. The golden ratio system doesn't seem to work.

Brian

 

[planet10]

OK, so extrapolating here: If I extend the top/bottom/sides 30cm 90deg towards the back wall, then I could expect a little more bass heft with no downside?

The downside is that the cavity caused by the sides causes a tincan resonance. Unequal length sides helps.

dave

 

[Peter Daniel]

It all depends on aesthetics. I wanted my open baffle speakers to look nice and not too big (or rathe wide ), that's why folded enclosure for woofer. The baffles are sloped so less resonances I hope. I also think that sloped pedestal has something to do with the bass response (took it from Wilson WAMMs), because although I'm not using any low frequency correction circuits, the response is down to 25Hz without a problem. Open baffle produces the best bass you can get.

A friend of mine wa so impressed with the look of mine design, that he took out the drivers of his cheap 3 way system and built enclosure similar to mine, placing his drivers there. He said that they sounded way better.

 

[roddyama]

Peter,

“My point is that the size of a baffle doesn't really have to be big. No frequency correction was required.”

I sure you’re getting the bass you say you’re getting, I just don’t see how you’re avoiding the cancellation below 100Hz.

One of the problems in trying to analyze a speaker’s bass output is that the wavelengths are so long that you can’t ignore the room interaction. In the final analysis, the placement of the woofer in relation to room boundaries will always have to be considered. This is even more true with an open back system.

Rodd Yamas***a

 

[Peter Daniel]

And this is what matters. The speakers would probably not produce much below 100Hz in different invironment, but I design them for my room and I'm quite happy with their response there. Should I ask for more, or complicate things when it's not needed?

I also have to point out than since their creation in 1996 I used them in 3 different rooms and results (or measurements) were always similar.

 

[dice45]

baffle size and bass

All,

before i started my open baffle thing (i also have a pair of Fertin FLB20EX) i tried out several speakers in open baffle mode and alway got results much more pleasant and open and detailed to my ears compared to enclosure operation. I also got way more bass than i expected. Subjectively. This is self-delusion. The brain reconstructs the base wave from the harmonics.

I talked to several acquaintants who had tried out open baffle, all seconded this opinion. Measured: there is not much below 100Hz for an open baffle of, say, 160cm wide, 200 cm high.
Subjective perception is quite another matter. One of my buddies finally built an open baffle woofer, EQed and going down to 25Hz. Now this is bass, he reported, before this was a fake.

And this is what i do with my Fertins: i have them in a folded open baffle of 100cm width (effective width is more) and 175cm height. Part of this baffle is an open-baffle subwoofer having two Beyma 18"ers mounted; this subwoofer is the pedestal on which the Fertin's open baffle is mounted. The subwoofer pedestal has a baffle inside which is 25° tilted against level and carrying the 2 woofers. The two woofers are fed by a 100W AKSA amp having the necessary EQ at the input.
The Fertin is fed by a tiny PP tube amp.

One warning: the Fertin has to be mounted by it's magnet, oops, fieldcoil motor. The basket it too weak to carry the huge motor.

Fertin sonics:
Break-in time is considerable. But already from the start the Fertin was by far the best FR driver i ever heard. They are simply seductive.
Highly Recommmended. Who trusts me on the MKVs should trust me on the Fertins. I rate the Fertins as i rate my Koetsu Urushi phono cartridge:
.. i must be starving before i sell it.

 

[bcherry]

The downside is that the cavity caused by the sides causes a tincan resonance. Unequal length sides helps.

dave

So what if I tilt the baffles back 5 degrees but mount the drivers so they are canted 5 degrees so they're still firing straight into the room?

Brian

 

[bcherry]

Re: baffle size and bass

All,


One warning: the Fertin has to be mounted by it's magnet, oops, fieldcoil motor. The basket it too weak to carry the huge motor.

.. i must be starving before i sell it.

Really? Thanks for the tip, but the basket segments are thick steel and the whole unit is 8 kg. The basket doesn't seem overstressed. Is that based on the German dealer's experiences? Do you have a picture of the mounting you used?

Brian

 

[Peter Daniel]

Re: Re: baffle size and bass

Do you have a picture of the mounting you used?

You'll find a good example of it here: http://www.linkwitzlab.com/m_panel.htm

Linkwitz is one of the recent pioneers of open baffle speakers.

 

[Peter Daniel]

So what if I tilt the baffles back 5 degrees but mount the drivers so they are canted 5 degrees so they're still firing straight into the room?

Are you talking about woofers here? (and not Fertins)