4x 15" Need your support for bent sub baffle project

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McLanz

McLanz

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Joined 2006
#1
Hello guys,

at home I have a fullrange system const of a 50's alnico + paper tweeter which I managed to play wonderful but I miss the lower bands.

My friend got the same but has a well designed Ripol bass system with two 12" special drivers per Ripol box. The system is tuned to just reproduce the very low tones. He cuts it at 40-50Hz sometimes a bit higher but not higher than 80Hz. The bass extension gives a wonderful realism and musical floor. The Ripol is fast enough to cope with the speed of the old light paper alnicos.
The only problem is the bass system is quite expensive with amp its sold by a German company (sorry I forget the name) for around 3000 Euro (near the same in dollars)


So here I 'am: start thinking how I could realize a near similar system - which goes low and fast enough. I thought about the following (below) and I'd like to ask you if this could work and if you may have experience with such not so complete new arrangements.

I thought of two Eminence 15" speaker in a open baffle. Its fast for sure - its a lot of membrane surface giving a good impact and the lower regions are surely comprised but since they are two per side makes 4 in total the compromise in lower frequency should be tolerable,
I do not want to have 2 meter high towers or baffles! Therefore I designed these bent polygons instead. One side with on bass faces to the listener the other to the back of my living room. Is this acoustically feasible ? Will I get some side effect since both woofers stray against each others?

Please apologize my silly sketch 😛...but I think it's clear what I want to do.


Please let me know if this could work similar to a straight open baffle. I think it looks quite pretty in comparison.


Jochen
 

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#10
The "performance balance" from the W-frame dipole baffle topology is difficult to beat, especially with a front facing push-pull loaded slot. Typical W-frame slot area is 0.5*Sd or larger. Typical Riple slot area is 0.25*Sd or smaller.

Made popular by Linkwitz, it has the advantages of:
1) reduced vibration from counter-force topology;
2) reduced harmonic distortion from cone-magnet(front-rear) cancelation topology;
3) increased dynamics from push-pull front slot loading;
4) lower high SPL distortion when compared to Ripole(high speaker-speaker air pressures in narrow ripole slot affects motor linearity);
5) reduced height topology;

and has the limitations of:
1) physically wide topology;
2) limited high frequency(100Hz ideal, 200Hz limit) performance due to slot resonances;
3) bland appearance... compared to sculptured flat baffles;
4) less deep bass than Ripole ... if used without equalization

Stacking one front_slot W-frame on top of one rear_slot W-frames offers counter slot symmetry which can further reduce distortion. Most designers favor using one pair of larger diameter woofers with a front facing push-pull slot loading, OR stacking W-frames with all front facing slot loading.

The narrower H-frame baffle with 10" or 12" woofers is more popular.... thin is sexy... two front-rear stacked woofers in one H-frame is a popular balance of (form * function * appearance). Just pump in equalized high power!
 

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#11
Hi LineSource, thanks for the info ! How deep can I expect without equalisation?

Background is that the Ripols of my already mentioned uncle with near identical set run quite deep and it seems to me that this adds again realism to music. I won't mind getting this without EQ to be honest.


I built one Ripol prototype and I also agree with you that distortion and pressure effects can be heard. Also the driver choice is delicate in regards to suspension and vent noises. The drivers need to be well constructed.


A) What about the speaker requirements of Dipoles? Generally "Medium" or "high"
B) How fast appear dipoles when connected with ultra light paper full range speakers.

Regards
 
#13
Some Updates: I will start go out and do listening tests of the Bastanis Mandala & and Axel Ridthalers Ripol creations.

I've found out that Robert Bastani lives quite next to me 🙂 I heard so much about his creations but never figured out that I can just visit him shortly...
I curious to see how his special dipol with 15" or 18" sounds. According to a first contacts via Email they are quite deep by nature which is on of my goals.

Then I've had a phone call with Axel Ridhtaler, the inventor of the Ripol design. Nice person ! He offered me support in designing a Ripol to my cost restrictions. His approach is to tightly match the Ripol design to the front speaker. He has 10", 12" etc...and depending on the cut off frequency he chooses one.
He is located in Karlsruhe - two hours of driving - so in June I look forward for a visit.
I report back my impressions. He currently uses Voxativ fullrange and a Electrostat speaker.

PS: I see for the used Madalas in Berlin....may wait first.
 
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