Fertin project - calling all open baffle experts

[bcherry]

Originally posted by Peter Daniel


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

Just Fertins. Firing straight at the listener, but mounted so the baffle can be tilted back 5 degrees, creating a little time 'misalignment' havoc at the back. Would it kill the 'tin-can' effect?

Brian

[Peter Daniel]

I had the impression, that you wanted to use Fertins with woofers. In that case you use Fertins in a flat open baffle board (or with a little curve like I did) and then you don't have to worry about tincan resonances.

Sloped bafffle can be used for woofers, because here you want to fold it to extend its size, but I don't think that you have to be worried about 5 deg. angle. Grand Utopia has both woofers' baffles at the angle for a reason.

Check Linkwitz site http://www.linkwitzlab.com for great info on open baffles projects, as well crossovers and woofers response correction circuits. Although for my taste, they are too much complicated.

[bcherry]

Originally posted by Peter Daniel
I had the impression, that you wanted to use Fertins with woofers. In that case you use Fertins in a flat open baffle board (or with a little curve like I did) and then you don't have to worry about tincan resonances.

Thanks for the link.

I hope to avoid the headaches of trying to integrate the Fertin with another driver. Always found it can never be seamless and throws away the strengths of a FR driver.

What about treatment of the wall behind the Baffle? Egg crates, acoustic foam etc?

Brian

[Peter Daniel]

Originally posted by bcherry



What about treatment of the wall behind the Baffle? Egg crates, acoustic foam etc?

You can find some info here RPG Diffusor's "BAD Panel", what do you DIYers think?

and here
Tube traps ?

I didn't use any of it yet.

[dice45]

Brian,

Originally posted by bcherry
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?

no, i have no pic and if i had, i would not post it. at the moment my Fertins are strapped on a move box made from corrugated cardboard and filled with my vinyl back copies. On top of the move box is a piece of plywood.

The speaker is carrying the baffle by its basket. The baffle also is corrugated cardboard and weighs less than 0.5kg.

This setup was meant to test the speaker and to have it collect burn-in time. When i did it, i knew i would not have my wooden baffle ready soon. Now it sounds so terrific! Outperforming any speaker i had before. Okok, low end is really slender if present. I feel not urged to change this setup for the moment; as soon as i can i will build the wooden thing.
I have CAD pixes of the wooden thing attached.

To the motor mount:
yes, my experiences are partially based
on the German dealer's findings. But also on my engineering judgement: my speakers have a basket consisting of a turned rim to which spokes made from bent sheetmetal are glued. The other ends of the basket spokes are screwed to the motor's pole plate, this joint i feel fine with. But the 6 glued joints between spokes and rim are under permanent static stress by the motor weight and dynamic stress by the vibrations of the baffle. The stress inserted into the glueing joints is peeling stress and dynamic; both concerns me.

Therefore i decided to mount the driver y the motor and mount the basket stress-free and only airtight into the baffle. See pix.

[bcherry]

Originally posted by dice45
Brian,
I have CAD pixes of the wooden thing attached.
To the motor mount:
yes, my experiences are partially based
on the German dealer's findings. But also on my engineering judgement: my speakers have a basket consisting of a turned rim to which spokes made from bent sheetmetal are glued. The other ends of the basket spokes are screwed to the motor's pole plate, this joint i feel fine with. But the 6 glued joints between spokes and rim are under permanent static stress by the motor weight and dynamic stress by the vibrations of the baffle. The stress inserted into the glueing joints is peeling stress and dynamic; both concerns me.
Therefore i decided to mount the driver y the motor and mount the basket stress-free and only airtight into the baffle. See pix.

Nice pictures! Looks like you'll get stompin' bass with that setup.

With the threaded hole in the back of the drivers for a mounting bolt, it won't be that difficult to support the drivers from the back.

Today I taped some 20cm wings to one side of the the baffle and got more low-end. A bit more and I think I can live with it. Never had speakers that image like this; I can walk the distance from one speaker to the other and still get imaging outside the speakers. I found that tilting them back projects a much taller image. They play so clean so effortlessly in their range that I found myself turning the volume too loud. Was getting a little clipping from my 45 pp on peaks so I measured with the SPL and found it shooting over 100db. I normally listen in the mid 90's.

I'll be increasing the size of the baffle to 220cm tall x 80cm wide with 20cm wings on both sides.

If that doesn't do it, then I'll put them in a TP1! What do you think of that? I'll have to choose between Xover complexities or box colourations. I'm leaning toward a box, if necessary.

Brian

[dice45]

Brian,

caveat:
the Fertins are not meant and not suitable to work in a backloaded horn (if you mean the Lowther TP1). The driver is not completely airtight from diaphragm frontside to backside (which is a must for a horndriver). It will whistle thru the air gap!

Then:
from my listening experiences with the Fertins, i definitely would prefer XO complexities to boxy colorations. They eat up transparence and detail and that fancy tone colour distincability.
My hint: biamp and have filters inside the amps. As-if-active

Another thing,
The Fertin has a comparatively high Q_ts unlike the Lowthers. Perfectly suited for vented and closed enclosure, for open baffle, for TL. But not for horns, they like low Q_ts. BTW, do you really like the low end delay a backloaded horn produces? PRaT is gone to the dogs, compared with open baffle.

To your baffle size:
i was informed that not the rope polygon counts but that the real width and height of the baffle also is the effective one. I do not have the formula at hand but if you find it on the web, use the real width of the baffle to calculate f_-3dB.

To acoustic damping of the rear wall:
I always had diffusors (bookselves not filled completely make great diffusors) and absorbers behind my listening chair and on one side wall only. I never treated the walls behind and around the speakers. Always preferred it that way.

[bcherry]

Originally posted by dice45
caveat:
the Fertins are not meant and not suitable to work in a backloaded horn (if you mean the Lowther TP1). The driver is not completely airtight from diaphragm frontside to backside (which is a must for a horndriver). It will whistle thru the air gap!
[/B]

Too bad! I had read about someone putting them in BD horns with good results but I guess no back pressure with such a high cutoff.

Then:
from my listening experiences with the Fertins, i definitely would prefer XO complexities to boxy colorations. They eat up transparence and detail and that fancy tone colour distincability.
My hint: biamp and have filters inside the amps. As-if-active
[/B]

Well, no experience with the Fertins but years ago I tried in vain to blend fast panel speakers and Strathearn ribbons with woofers and always spoiled the sound. Tried both active/passive but could always hear the crossover point and what's below.

The Fertin has a comparatively high Q_ts unlike the Lowthers. Perfectly suited for vented and closed enclosure, for open baffle, for TL. But not for horns, they like low Q_ts. BTW, do you really like the low end delay a backloaded horn produces? PRaT is gone to the dogs, compared with open baffle.
[/B]

Well of the horn enclosures (with Lowther) I like TP1 best; most dynamic. But it's making tradeoffs for sure. Panel/open baffle are in a different class and are so seamless, I'm loathe to interrupt that with more drivers. I'll wait to hear your reports when your finished (ha!).

To acoustic damping of the rear wall:
I always had diffusors (bookselves not filled completely make great diffusors) and absorbers behind my listening chair and on one side wall only. I never treated the walls behind and around the speakers. Always preferred it that way. [/B]

:

With dipoles, I'm just thinking of trapping that back wave.

Thanks for all the good input.

Brian

[bbaker6212]

Please, please, please, keep the Fertin comments comming. There are way too few opinions/comments to be found about them. And they're too darn expensive to buy without a high degree of faith that they will sound as good some are reporting.

Some comparisons to how various (hopefully well known) songs sound vs. other high quality speakers would help.

ie, what speakers did you used to have, and how do the Fertins better them?

[bcherry]

Originally posted by bbaker6212
Please, please, please, keep the Fertin comments comming. There are way too few opinions/comments to be found about them. And they're too darn expensive to buy without a high degree of faith that they will sound as good some are reporting.

Well, I can update you with this after 50 hrs of playing: This is the most seamless coherent sound I've heard. Also, they are starting to bloom in the bass. The 'voice in the room' spooky presence is starting to spread to other areas higher and lower than the human voice. Just starting to hear some impact in the bass. Got to get one of those frequency test CD's to find out where we are. Going through some past emails from the manufacturer it was recommended to set the PS to 10V for open baffle to give a better balance, and 12V when used in a box to pitch up the highs a bit. At 10V I don't notice that much difference in efficiency (getting about 4w from PP 45's) but the balance is better. I was playing a Kodo drum record to give the driver a workout and noticed a lot more bass detail (skin notes, trills) that I never heard before.
Next week new baffles coming with larger area.

Could this kind of speaker be made in 12"?

Brian