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Old 15th June 2017, 09:48 PM   #1
Mayuri is online now Mayuri  Finland
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Default ET Build: Ripole sub & SS 10F/8424 Sphere

Hello all! I am planning a new loudspeaker pair for my home use on my small listening room. Hopefully you can give feedback on what to improve on my plan. All crossover duty will be handled by MiniDSP 2x4 HD. The woofers will be driven with TDA8932s, one per unit. The full range drivers will be driven by NAD 912 amplifier. My listening levels are not very high, so they should manage. Listening height is almost exact 1 meter. Measurements of drivers:

ScanSpeak 10F/8424
Peerless SLS 12

The current plan is to have a pair of Ripole subwoofers producing the 20-250Hz bandwidth. They will have 2x Peerless SLS-12 woofers in them per unit as per the original Ripole plan (attachment 1 & 2). They will be on 20cm legs to adjust the listening height. Nothing special with this, it's a well-proven design good for combating room modes. I am thinking of using 21-25mm BB plywood for the construction, should be very solid to push the internal resonances way up past the operating bandwidth.

From the back of each Ripole sub leaves an axe handle which 38cm upwards from the top of the subwoofer connects to an IKEA Blanda Sphere which houses the ScanSpeak 10F/8424, which will handle rest of the range from (200-300Hz upwards). This is pushing the capabilities of the driver a bit, but I'm fairly certain it will manage. The CTC distance between the drivers would be 58cm, which stays inside 1/2 wavelength of crossover frequency. The sphere itself will be made of the 20cm diameter Blanda Matt bowls, which would mean that the lowest point of the bowl will be 28cm from the Ripole surface and the top 48cm. Center of the SS driver will be 38cm from the surface. They bowls would after damping and bracing equate to around 1,5l internal volume enclosure (attachments 3 & 4). This would mean a critically damped enclosure of quite low Q.

Bushmeister has a good description about the advantages of spherical enclosures in his thread: Great Balls of Prestige

The 10F will attach to the enclosure with a bolt and nut, having a 3mm Sorbothane gasket between the enclosure-driver and enclosure-nut. I will break all solid connections between driver and enclosure to minimize vibration transfer between them along with dampening the sphere properly.

Last but not least, a somewhat to-scale drawing of the total system (attachment 5). First time my wife saw them she commented that they remind her of ET, which I kinda agree to
Attached Images
File Type: jpg 008.JPG (132.1 KB, 226 views)
File Type: png Rippole.png (64.5 KB, 226 views)
File Type: jpg 20160926_104944.jpg (325.3 KB, 227 views)
File Type: jpg SS10F-15dl.jpg (210.0 KB, 219 views)
File Type: jpg 09WMtyj.jpg (84.8 KB, 216 views)

Last edited by Mayuri; 18th June 2017 at 12:20 PM.
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Old 15th June 2017, 10:11 PM   #2
Face is offline Face  United States
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You'll experience the dipole peak pushing the woofers past 200hz. The 10F will be excursion and thermal limited at 200hz as well. If you listen at low listening levels, you might be ok.
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Old 15th June 2017, 10:16 PM   #3
Mayuri is online now Mayuri  Finland
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I have the MiniDSP which can handle the crossovers, dipole peak for sub, baffle step correction for 10F, room correction and time alignment. The little box really saves me a lot of headache compared to running that all with analogue components
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Old 18th June 2017, 09:30 PM   #4
Mayuri is online now Mayuri  Finland
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I've been thinking about the Ripole + full range integration lately. The full range has to go quite low to fill the operating bandwidth. Other drivers I own are

Woofers:
Peerless 830868
Peerless 830869
Seas W15LY001 (would have to buy this)

Tweeters:
B&G NEO3 PDR with the faceplate
ScanSpeak D2010/851300

Would these make a better choice? I'd have to go from full active to half-active, as I plan on running the crossover from dipole to rest of the system with miniDSP. The woofer would go to 9l or 18l enclosure if I stack two 28cm blanda spheres.

Last edited by Mayuri; 18th June 2017 at 09:49 PM.
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Old 18th June 2017, 09:55 PM   #5
Face is offline Face  United States
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Plenty of options with that selection of drivers. What comprises or changes are you willing to make to your cabinets?
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Old 18th June 2017, 10:11 PM   #6
Mayuri is online now Mayuri  Finland
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I'm mainly looking for better room integration with the Ripole subwoofers. My current setup is Peerless SLS-12 in 70l closed box with SS 10F. It is otherwise fine but in my listening space there is a huge 70Hz null. Very hard to fight against the room modes, must adapt.

The things that I am set on:
1) Ripole or similar subwoofer which helps with room modes (I already got 5pcs of Peerless SLS 12 woofers.
2) IKEA Blanda Bowls for speaker cabinets. I am convinced the sphere is the optimal shape for speaker enclosure (maybe ovoid is better but very hard to DIY). The bowls have 12cm/20cm/28cm outside diameters with 1 cm material thickness.
3) MiniDSP for crossover and time alignment, EQ, etc. between Ripole and rest of the system.

I have nothing aside from the drivers and MiniDSP bought yet, so pretty much full freedom. My listening space is the biggest problem, only a 3,5 x 3m room, very small.
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Old 19th June 2017, 07:23 AM   #7
Calvin is offline Calvin  Germany
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Hi,

running the dipole sub up to 250Hz is certainly ambitious
In the Sim You can just detect the chamber resonance as a small wobble in the amplitude response ~280Hz.
Even when You notch out the peak perfectly the resonance may still be audible due to its longer decay.
Id suggest to xover at not higher than 200Hz.

In early 2004 I built a very similar concept I called Drops, featuring the Vifa 10BGS119/8.
I used it combined with a single Ripole made from two 8" Peerless drivers (one of Axels original designs under the label of AudioElevation).

I put the Vifas in a small flower vase I bought in a 1€-shop (whereelse could one find such a ugly blue vase anyway?).
Trimmed the opening with a grinder to slush-fit the Vifa basket and milled a hole for the cabling into the bottom and a hole into the side for mounting purposes ... so much for convenience.
The Vifa showed a much smoother amplitude response than mounted to a flat baffle (compare to HobbyHiFi project PicoLino, 4/2001).
It still required a soft notch in the upper midrange to linearize the response ... as almost all FR do.
As the volume of the vase was so small itd resulted in too high fb and Qtb, I used a large series Cap.
A series cap of appropriate value functions similar to a BR-port.
It equalizes the high Qtb-peak and shifts up the amplitude response below fb.
That way the Vifa could be linearized down to nearly 80Hz in a 1L cabinet and 470F Cap.
I could have used a active crossover equalizer instead, but I just wanted to try the passive series cap thing anyway.
The bottom of the Vase got closed by a black plastic dome ... originally a egg cup with a opening so that a cable would fit through (the thick Neutrik cables ... which looked a bit weird considering how small the Vase was .... it rather looked like ... well ... ahm ... a sperm.
Mounted it on a stainless steel rod and a concrete garden plate in the shape of a footprint (only 5€ a pcs).
I dont recall where I crossed the subwoofer but I think it was somewhere around 150Hz.

Sonically the combination of this little fullranger and the dipole woofer astounded everybody who gave it a listen.
Of couse the dynamic limits only allowed rather soft -but mostly sufficient and certainly more than one would have expected- volume levels .... but within this limit it played very neutral, focused and with great staging.
The tiny subwoofer reached down to almost unbelievable 25Hz.
It completed Drops in a way that the combination sounded like a true big system.

I assume Your project will lead to very similar results.
The 12" Peerless will allow for more authority in the lowest registers ... and the FR will rather be the dynamically limiting part here.
You may equalize the FR either with a series cap or with the DSP to reach down to ~150-180Hz .... using 4th order Filters could reduce problems of both, the FR at its lower end and the dipole woofer at its upper end.

Attached are pics of Drops ... not fully completed.
The holding hand just gives an idea how small those thingies really were.

jauu
Calvin
Attached Images
File Type: jpg Drops 3klein.jpg (36.9 KB, 58 views)
File Type: jpg Drops 9klein.jpg (58.8 KB, 46 views)
File Type: jpg Drops klein.jpg (19.3 KB, 40 views)
File Type: jpg 66KLEIN.JPG (16.0 KB, 37 views)

Last edited by Calvin; 19th June 2017 at 07:28 AM.
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Old 19th June 2017, 03:20 PM   #8
Mayuri is online now Mayuri  Finland
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Thanks for the advice Calvin, was hoping you'd comment on the plan as you are probably have the most knowledge about Ripole in these forums.

It sounds like a massive overkill to have 4x Peerless SLS 12 in a small room, or 2 Ripole subs, but I guess you can't go wrong with futureproofing for a bigger listening space These speakers will be strictly for music use, although I might listen to a movie soundtrack every now and then. I got a separate HT setup on my living room.
Do you think I should go with the Ripole plan on my first post or something modified? I contacted my local carpenter, he only has 21mm BB plywood in stock, but that will quite likely suffice. I'll construct and finish the cabinets myself, just want to get the pieces pre-cut

I am currently aiming for 200Hz crossover point at per your advice. I will specify the overall crossovers with in-room measurements, I'm aiming for either 4th order Linkwitz-Riley or Harsch crossover slopes. Harsch would be nice for the phase accuracy, but it puts more stress on the full range as it's only 2nd order high-pass.

Anyhow, looking at the measurements on the 10F, it seems that the 2nd order distortion climbs up almost linearly under 800Hz, whilst 3rd order distortion and 5th order distortion begin rising at around 200Hz. I guess 200Hz is around bare minimum what I'd want to cross this driver.
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Old 19th June 2017, 04:39 PM   #9
Calvin is offline Calvin  Germany
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Hi,


i don't actually know what I could comment more on the concept .... I like it and obviously did quite similar.
With one wooder for each channel the xover can generally be chosen a few Hz higher than with just a single woofer.
With appr. 4-5 times the membrane area compared to the Drops system your woofers allows for much greater dynamic reserves (with nearly the same lower bandwidth limit).
The small FR will very probabely limit first.
Q: is the FR already set, or could there be other options?
I'm thinking for example of those Seas 14cm and 17cm Coax drivers, that may be built into quite small spheres also.

jauu
Calvin
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Old 19th June 2017, 05:11 PM   #10
Mayuri is online now Mayuri  Finland
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I already own the FR driver. Other choices are the drivers I listed in my earlier post. I prefer to use drivers I already own or can get second-hand for cheaper prices

I personally don't like coax drivers. I can't put my finger on it, but I have never liked their sound. I've heard both expensive (Genelec studio monitors) and cheap (car stuff) coaxial drivers, but I always prefer the non-coax versions.

As of currently, I think I'll build Ripole + Blanda FR spheres on, but I'll make the joint so I can change the spheres later if needed. So Ripole + axe handle will form the bass-stand for the speaker

Question: From the plan, are the drivers surface mounted to the middle chamber? If I surface mount them, should I make front chamber wider?

Last edited by Mayuri; 19th June 2017 at 05:35 PM.
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