Creativity is back...

...and testing the very first prototype for a range of new open panel systems with optional "fitting" open panel subwoofer for people who need more and deeper bass.
Expect similar looking and different sized solutions utilising Feastrex, Lowther, Fostex, Visaton and more... :yes:

To test this basic panel design I am trying out the Hemp FR8C at first which measures very well balanced except for somewhat too much energy around 3kHz which comes from the driver itself.

[image]

L=0,22mH - C=12,2uF - R=12ohm

To keep that energy below the "surface" I designed a notch filter to cure that problem...see circuit drawing which can be used regardless the enclosure build for these drivers.

The test panel I have here is made too ugly to show to the public :blush: but as soon as I have made a few better looking panels for more serious tests then I will put some pictures up here.

Here is a drawing showing the initial design for the upcoming series...

[image]

Looks even better in reality... any comments? :whistle:

Bert

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BD-Design - Only the Best!

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FR8C Notch

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Bert,

... yes, it is! As always, the best solution is a simple solution! The panel looks attractive, better than just a flat panel.

How about the lower frequencies? At what frequency a subwoofer is necessary? In the past I heard the Quasar One and was stunned by its performance. Is this new project sounding even better, or just different?

Keep up the good work! :wink:

Best regards,

Frank

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Hi Frank,

The panel looks attractive, better than just a flat panel.

I couldn't agree more on that...and besides the looks it has several other advantages over just a boring flat panel which will make it perform even better:

smoother dispersion (vertically and horizontally)
less diffraction problems
more rigid construction
nicely spread resonance pattern

How about the lower frequencies? At what frequency a subwoofer is necessary?

This depends on the used panel, there will be several sizes and that determines the need. The biggest one does not need a sub (unless you need more power in the deeper bass) but the smaller ones (think about lowest frequencies 50-80Hz) could use one...

Keep up the good work! :wink:

Thanks,

Bert

--
BD-Design - Only the Best!

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Hi Bert,

I had to register at last
How much db attenuation this filter correspond to? I'm going to simulate it with my test PC. This'll help me evaluate the Hemps as well.

Also, what is your opinion about "passive" filtering BEFORE the power amp? I would add a highpass filter at the same time in that case.
But I need to measure the drivers first and I havent received my Eathworks mic yet. My ears tells me of a rolloff between 200 and 250hz on flat baffles of 35cm width.

Also, the layout looks nice and I'm pretty sure that it measures better than a flat baffle. It should also be possible to integreate a ripole (4x32 cm vertical opening in my case) for the woofer in the bottom part making it less angled.

Regards,
Guido

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Welcome Guido,

How much db attenuation this filter correspond to? I'm going to simulate it with my test PC. This'll help me evaluate the Hemps as well.

About 3dB if I recall correctly.

Also, what is your opinion about "passive" filtering BEFORE the power amp? I would add a highpass filter at the same time in that case.

I am using this principle all the time and for many years too...

But I need to measure the drivers first and I havent received my Eathworks mic yet. My ears tells me of a rolloff between 200 and 250hz on flat baffles of 35cm width.

Could be, I do not have a 35cm wide panel.

Also, the layout looks nice and I'm pretty sure that it measures better than a flat baffle. It should also be possible to integreate a ripole (4x32 cm vertical opening in my case) for the woofer in the bottom part making it less angled.

Thanks for the kind words but do you really think that a ripole would work well?

I never liked enclosed woofers with their cavity resonances "peaking" nicely in the crossover range...unless you use them as subwoofer or having a steep crossover at least one octave below the first cavity resonance.

Or am I mixing things up here?

Bert

--
BD-Design - Only the Best!

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Thanks, Bert.

Also, the layout looks nice and I'm pretty sure that it measures better than a flat baffle. It should also be possible to integreate a ripole (4x32 cm vertical opening in my case) for the woofer in the bottom part making it less angled.

Thanks for the kind words but do you really think that a ripole would work well?

I dont know until I try
I have close wall placement (max 60cm), so a classic front facing dipole (with help from u-frame) would have some problems of the backwave null.
An alternative is to put the woofers sideway, but that can sound worse than the Ripoles. Agian i need to experiment in my setup and in my room.
I have never liked speakers with side woofers. My guts tell me that the ripole will be better, so I'm starting with that.

I never liked enclosed woofers with their cavity resonances "peaking" nicely in the crossover range...unless you use them as subwoofer or having a steep crossover at least one octave below the first cavity resonance.

Or am I mixing things up here?

I have never liked BR and closed woofers too.

No, you are right. But the ripoles that Rudolf designed for me have resonance at 300hz and i will cross around 200. Yeah, the filters will be steep and for sure in digital. If they can work well, your enclosure design could be my definitive one

/Guido

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Guido,

No, you are right. But the ripoles that Rudolf designed for me have resonance at 300hz and i will cross around 200. Yeah, the filters will be steep and for sure in digital. If they can work well, your enclosure design could be my definitive one

Keep me posted about those and soon enough the first real panels should be ready...

Bert

--
BD-Design - Only the Best!

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Guido,

No, you are right. But the ripoles that Rudolf designed for me have resonance at 300hz and i will cross around 200. Yeah, the filters will be steep and for sure in digital. If they can work well, your enclosure design could be my definitive one

Keep me posted about those and soon enough the first real panels should be ready...

Bert

As said in the other thread i ditched the Ripole option, but i'm still considering the 2x10" in a setup like the Diamonds.

I dont remember when i updated you on my Hemps, anyway, in the current baffles (20mm plywood, simulated trapezoid shape), they behave much better than my ears would tell me.
I did some measurements and more are to be done. So far, they are pretty smooth!
the aNoyance in the voice range must be only energy storage. i dont know exactly how this hapens but i know for sure now that is something that i hate.
Also i hate non linear distortions, in particular the ones that raise dramatically playing louder. My woofers are able to sustain way more power than the Hemps. I think this is a problem of most fullranges, esp. the ones with low Xmax.

Correct me if i'm wrong, but i think that the cause is the bicone, which is just paper and therefore limits the hemp benefits to <2k. Way too low. Anyway, they go really high. the rolloff starts at 17.5k and is smooth. figures, i reduced other 2db at 20k, which helps with my current source that is not state of the art.

Still thinking of replacements, not much in a hurry. Researching and planning. I know i'll stick with dipole and a widerange of some kind, with or without a (passive) tweeter on top. Heils are currently my favourites.

Anyway, I'm gathering experience. I need more and more auditions before finding "my way".

Cheers,
Guido

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L=0,22mH - C=12,2uF - R=12ohm

Btw, a guy on an italian forum where I have my hemps building log, gave me a doubt. He asked for confirm of the values used above. He thinks that the inductor and cap are switched.

Can you confirm that the values above are correct?

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He thinks that the inductor and cap are switched.

If you would exchange the values then the notch will be useless... :swoon:

Bert

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BD-Design - Only the Best!

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any news on you OB ?

i would love to see some photos of the prototype

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Hi Siepi,

any news on you OB ?

i would love to see some photos of the prototype

Sorry but it takes longer to build a decent and reliable prototype as it turned out to be far more difficult to make one of wood.... (each panel is angled in all its dimensions!)

I decided to go the full route as the tested version already worked out very well giving me more than enough faith to have them CNC made (making the CAD drawings, cutting prototypes and then decide for the final version).

This work is outsourced which takes a bit more time but I think I will have some decent first prototypes to show in a few weeks.

Going the CNC-route anyhow (I would like to offer complete DIY packages with wood included as option) it would be wasting time making them by hand my own at first and then throw them away a bit later...

Bert

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BD-Design - Only the Best!

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