Ripole build - dual 18" Hawthorne Audio drivers

gooberdude · « **Reply #60 on:** 1 Sep 2011, 11:21 pm »

That's a great idea!!!

Lets brand Darrel H when he visits.

Bob in St. Louis · « **Reply #61 on:** 2 Sep 2011, 12:20 am »

Matt, I think he's got some martial arts in his history. I ain't brandin' shit.

Bob

gooberdude · « **Reply #62 on:** 2 Sep 2011, 04:22 am »

True, Darrell is a bad-ass.

the bbq brand is still the best idea.

Are the new drivers gonna work??

Bob in St. Louis · « **Reply #63 on:** 2 Sep 2011, 12:56 pm »

Why don't you come over here and find out.

Not sure yet Matt. I'm an hour or so away from heading into the workshop to do some measuring and test fitting. I'm sure I can get them to work, it's just more a matter of whether I'll be adding material or removing it. At first glance, the new ones look shorter and fatter. The magnets are much larger in diameter.

But seriously, I'll be home for the next four days piddling around the house, so if you're free, come on over. Send me a PM and I'll give you my address.

Bob

JohnR · « **Reply #64 on:** 2 Sep 2011, 11:42 pm »

Hm, that sucks. Nobody tested the drivers first?

Bob in St. Louis · « **Reply #65 on:** 4 Sep 2011, 03:01 pm »

Quote from: JohnR on 2 Sep 2011, 11:42 pm

Hm, that sucks. Nobody tested the drivers first?

Yea...well....umm.....

As it turns out, these drivers have the ability to rattle the entire house when mounted in open baffle.
Put them back in RiPole, and it all goes to Hell.

As I was disassembling the unit in my room, I was placing the "layers" off to the side. When I had it in apart I noticed the drivers were looking pretty majestic sitting on the carpet standing upright, like that was their intent.

Seemed like a good idea at the time to wire them up and see what they sound like. Why not?
As it turns out, the sound GREAT and can get VERY loud without distortion.

But put back in RiPole, I have to turn them up so loud to get any output, that they're bottoming out. With all volume/gain/setting untouched, the output from them is considerably more in OB than RiPole.

Bob

Russell Dawkins · « **Reply #66 on:** 4 Sep 2011, 04:52 pm »

Bob, did you check the polarity of the original drivers with a battery to make sure all is correct there?

I guess you know that you can touch an AA battery (for example) to the terminals to ensure the cone moves the same direction on each, with the + applied to the positive speaker terminal.

The bottoming makes it sound like the drivers were wired in opposite polarity and cancelling each other when mounted.

I say this because you mentioned they were handmade prototypes.

Bob in St. Louis · « **Reply #67 on:** 4 Sep 2011, 05:26 pm »

Thanks for posting Russell.

Good point, I did not check the polarity of the drivers.
I did, however reverse the polarity to the top driver and played the track again (same results).
Next, I put the top driver 'back' electrically, then reversed polarity to the bottom driver (same results) and finally, put the bottom 'back', and reverse polarity to the entire enclosure thereby making them "pull against each other" so to speak.
The results were the same every time, using very low volume and nothing below (iirc) 40Hz.

So in essence, by process of elimination, I ruled out the driver being built incorrectly....best I can tell.

Bob

zobsky · « **Reply #68 on:** 4 Sep 2011, 05:35 pm »

I've been saying Ripoles suck for a while now, on diyaudio, having failed twice at getting reasonable sound from them

. They went low in my experiments, but at atrocious efficiency and were accordingly easy to bottom out. More power to you if you prove me wrong. Otherwise, live and learn.

I'm not sure of the T/S specs for the drivers you chose, but if they are high Qts, I vaguely recall that the drivers originally suggested for ripoles were of moderately low Qts. Didn't make a difference either way in my experiments with various drivers, though (one experiment with Pyle PPA15 drivers with Qts of 0.7, IIRC and the other experiment with a conventional subwoofer driver i.e adire shiva 12").

If the drivers are high Qts and you want another idea for these (4 ? ) units, try a pair of dual OB, or dual driver W-style baffles (a-la Linkwitz).

Russell Dawkins · « **Reply #69 on:** 4 Sep 2011, 07:41 pm »

Quote from: zobsky on 4 Sep 2011, 05:35 pm

I've been saying Ripoles suck for a while now, on diyaudio, having failed twice at getting reasonable sound from them . They went low in my experiments, but at atrocious efficiency and were accordingly easy to bottom out. More power to you if you prove me wrong. Otherwise, live and learn.

I've never tried a ripole, but I'm surprised Nelson Pass's experiment works so well, since it looks like a ripole with a baffle. Maybe the baffle makes all the difference?
http://www.enjoythemusic.com/diy/0911/slot_loaded_open_baffle_speaker.htm

zobsky · « **Reply #70 on:** 5 Sep 2011, 08:49 am »

Quote from: Russell Dawkins on 4 Sep 2011, 07:41 pm

I've never tried a ripole, but I'm surprised Nelson Pass's experiment works so well, since it looks like a ripole with a baffle. Maybe the baffle makes all the difference?
http://www.enjoythemusic.com/diy/0911/slot_loaded_open_baffle_speaker.htm

Close, but not quite

Let's consider the BMC (blow motion concept) arrangement where drivers face each other and move towards and away from each other in unison and compare the equivalent dipole , ripole and "pass" slot loaded open baffle.

1. In the case of the dipole, the cavity dimensions are significantly larger compared to the woofer surface area and don't offer any mass loading to the driver motion. Bass is generated via front/rear path differences due to the baffle.
2. In the case of the ripole, the cavity dimensions are smaller compared to the woofer surface area (I think about 1/3 of Sd, or thereabouts) thereby loading the woofers on both the front and the rear). Additionally, since ripoles are so small, they fail to fully utilize front/rear path differences to generate bass via the baffle effect.
3. The "pass" slot mass loads the front of the driver (like a ripole) and also acts as a diffraction slot at higher frequencies . However, there isn't any load on the rear of the driver. At least, that's how I understand it. I can't comment any further on performance since I've never built one before.

Once again, I'm hoping I'm wrong and the OP manages to succeed with this project.

JohnR · « **Reply #71 on:** 5 Sep 2011, 08:55 am »

This is very mysterious and confusing. Bob - wouldn't take long to do the battery check would it?

neobop · « **Reply #72 on:** 5 Sep 2011, 01:15 pm »

I'm surprised that no one mentioned isobaric loading. All these configurations look like variations or evolutions. The isobaric gives you lower fs and cabinet volume is effectively doubled, or you need half the cabinet size. You sacrifice 3dB efficiency in a traditional sealed or reflex cabinet. I'm guessing that you need just the right driver for these more open type of loading schemes.

http://en.wikipedia.org/wiki/Isobaric_speakers

If you look at the link on page 1 of this thread, you'll see the efficiency is 80dB.
http://www.lautsprechershop.de/hifi/ripol_en.htm

I have no experience with them but it looks like a Ripole is appropriate only with a separate amp. Obviously being able to play below fs won't always work out. Professional drivers tend to be very efficient at the expense of deep bass response. If you get a fairly efficient sub driver with low fs it might be awesome.
neo

Big Red Machine · « **Reply #73 on:** 5 Sep 2011, 01:26 pm »

Bob, nice work. I love a good challenge but never had the cajones to try something like this.

mcgsxr · « **Reply #74 on:** 5 Sep 2011, 02:57 pm »

I have built many isobaric subs, and unless space is a concern, I would go with a standard sealed or ported box. As noted, isobaric 1/2's the space, but also adjusts efficiency down...

JohnR · « **Reply #75 on:** 5 Sep 2011, 10:13 pm »

It's not isobaric and has no resemblance to one at all...

face · « **Reply #76 on:** 6 Sep 2011, 04:14 am »

Do you have the T&S parameters from either driver?

Did you take any measurements?

From what I've read, Ripoles need a large x-max, Qts @ .5, and a FS of around 30hz or higher.

Bob in St. Louis · « **Reply #77 on:** 6 Sep 2011, 02:25 pm »

Face - >> THESE << are the replacement drivers, the spec sheet is there. I've got the T/S specs on the original driver written down at home, and don't have them with me. Since they're prototype drivers, that information may be a secret anyway, not sure.

Bob

Edited link....

face · « **Reply #78 on:** 6 Sep 2011, 02:32 pm »

The drivers in that link look like they *should work*, maybe there's an issue with design of the enclosure or the T&S parameters aren't accurate.

Bob in St. Louis · « **Reply #79 on:** 6 Sep 2011, 02:41 pm »

The drivers I linked to are the new replacement drivers purchased due to the prototype drivers being "blown". I've not mounted or hooked up the Eminence drivers since there's a remote chance they'll get sent back.

Bob