Charlie's Ripole Subs

[CharlieM]

Hello All,
I'm almost done building my new Ripole subs and I want to thank everyone here for posting such helpful info for us newbies. My new subs use (4) Peerless SLS 12's and will be powered by a Carver TFM-42. I completed the boxes today but I still have to decide on what kind of crossover and EQ'ing I will need to buy.

Here are some pics:
Jazzman's DIY Electrostatic Loudspeaker Page: Ripole subs are underway

In hindsight, I wish I had waited a while and learned more about Ripoles before starting the build, as I have since received much good advice for optimizing their performance but I was already too far along in the build to take full advantage of it. Still, the chambers and openings do meet the minimums recommended in one of Rudolf's threads so I am hopeful and confident that these subs will sound pretty good if I get the crossover and EQ'ing right. I could use some help with that, though.

My main speakers are hybrid electrostats with 10" transmission line bass. I would appreciate any advice on choosing a crossover, slope and EQ'ing to best blend my new subs with my main speakers. Thanks everyone!

[jacq.]

Hello CharlieM,
My understanding of a Ripole sub system is when they are used passively, I never really got fantastic results doing so, but with eq that's another ball game. Since you do have an amp for driving them why not investigate with the use of a MiniDSP, I doubt you would regret it. Look for the users manual on the web site. And of course do visit with LinkwitzLab and Music and Design.

Jacq.

[CharlieM]

Originally Posted by jacq.

Hello CharlieM,
My understanding of a Ripole sub system is when they are used passively, I never really got fantastic results doing so, but with eq that's another ball game. Since you do have an amp for driving them why not investigate with the use of a MiniDSP, I doubt you would regret it. Look for the users manual on the web site. And of course do visit with LinkwitzLab and Music and Design.

Jacq.

Thanks for the tip on the Mini-- but I've already drove off the cliff and ordered a Behringer DCX2496. With all that fancy ****, maybe I won't be needing a passive notch filter anyway.

[OllBoll]

Hello there,

Me wants to abuse your new knowledge

What parts in your drawing were sub-optimal? How would one modify it to perform optimally?

I'm interested in building my own but since I haven't yet found a complete drawing said to work optimally and only general directions I fear I too will make mistakes... which is why I ask you now

And when I'm already asking... is there a recommended power amp wattage for one of these ripole boxes? I'm wondering wherever I should get a 180W Class D module or get the 400W module. It's to be used only as a subwoofer, crossed at about 40-80 hz.

Thanks in advance,
Olle

[kenpeter]

What difference will 180 vs 400 make?
Either is going to bottom out xmax while
bass delivered to the room is nonexistent.

I have a friend who skillfully and correctly
built one with very high hopes against all
common sense and well intentioned advice.
Sorry, laws of physics are stacked against.
Nearly silent until the coil hits...

[CharlieM]

Originally Posted by OllBoll

Hello there,

Me wants to abuse your new knowledge

What parts in your drawing were sub-optimal? How would one modify it to perform optimally?

I'm interested in building my own but since I haven't yet found a complete drawing said to work optimally and only general directions I fear I too will make mistakes... which is why I ask you now

And when I'm already asking... is there a recommended power amp wattage for one of these ripole boxes? I'm wondering wherever I should get a 180W Class D module or get the 400W module. It's to be used only as a subwoofer, crossed at about 40-80 hz.

Thanks in advance,
Olle

Hi Olle,
I'm certainly no expert on Ripoles but there are others on the forum who are very knowledgeable about them. That said, let me explain what I meant when I said that my box design was not quite opimal (I didn't mean they don't sound good, BTW):

Ripoles with 12" woofers generate a rather strong chamber resonance that starts well below 200 hz and peaks somewhere between 200 and 300 hz.
A very smart guy on here the forum (who knows how to mathematically model Ripoles) read one of my earlier posts and was good enough to send me a fully modeled set of box dimensions with the corresponding passive EQ and notch filter components/values to exactly tame the chamber resonance and yield an essentially flat response from 20-200 hz. This setup would have allowed me to play the subs into the midbass region, if desired and would also have yielded somewhat better efficiency than my design.

As it was, I had already cut the wood and was halfway through the build at that time and I didn't want to scrap that work and start over so I decided to live with what I had. Anyway, I had followed the generic guidelines at least and I would be using them as pure subs (below 50hz) with a sharp cutoff slope so I didn't hurt myself too much.

These subs have a very clean sound and play incredibly low. As with all dipoles, the woofers will bottom out when they reach the limits of x-max and they only about 25% as efficient as conventional subs-- so you need a lot of cone area to play loud. As for their sonic character: The bass notes just seem to come from nowhere on the attack and recede to nowhere on the decay with none of the booming that I was accustomed to hearing from my other (sealed) subs. That said, they are dipoles so they can't pressurize the room with the kind of chest thumping bass you get from sealed or ported subs. So if you're looking for quantity, Ripoles aren't the best choice--better for jazz than loud rock or theater sound effects, I would say.

I like the sound of these subs though. As is characteristic of dipole bass, it's what you don't hear (box and room resonances) that makes them appealing.

Check your mailbox later today, I have something for you.

[OllBoll]

Thanks!

Since I hate loud listening low volume wouldn't be a problem =)

Personally I'm going to use an miniDSP so EQing wouldn't be a problem for me, but now I'm split between if I should do a PHOENIX Dipole woofer with the Peerless XLS or dual Ripoles with the SLS... They didn't just *happen* to tell you if one of these are superior to the other?

If I've understood correctly the Ripole has even less output volume than the PHOENIX Dipole, but plays even deeper bass or have I missed something?

The grateful Olle =)

[Calvin]

Hi,

just a few remarks to the Ripole´s.
A Ripole genuinly includes the passive correction network. Without it it´s no Ripole but a small sized folded Dipole.
Efficiency is often misunderstood or used in an incorrect way. As a follow Dipoles are said to have low efficiency. But that is not the whole case.
The dipole does not exite the room below the lowest room mode as a global distributing bass would, so it doesn´t profit from the room gain. It also suffers from acoustic phase cancellation. So one would truely expect less SPL at very low frequencies.
But if one compares efficiencies one needs to keep in mind the circumstances. A dipole benefits from the SPL of its backside. So above a certain frequency break point the dipole surpasses CB- and BR-loaded boxes. For typical subwoofer dimensions this break point is located somewhere between 50Hz and 80Hz. So if You´re using the dipole only as bass, keeping it off of the subwoofer-range below 50Hz it plays on par with CBs and BRs.
What else is usually not taken into account is the size of the dipole. A CB or BR (if a BR of such small size would be possible anyhow) of same size and under usage of a same sized driver would need heavy equalization and would yield a low efficiency also. You can trade size against efficiency. So a smaller sized system must be lower in efficiency.
If I compare a dipole of a size that may even be smaller than the drivers shipping cartonage, I need to compare it against a CB or BR of equal size.

There are five major differences between the Phoenix dipole and the Ripole.
1) Size:
Obviously the Phoenix builds considerably larger than the Ripole and relys on electronic equalizing. The Ripole features a passive correction network and may in some cases need a bit of additional bassboost.

2) Acoustic results:
The smaller sized chambers of a Ripole lead to a drop in the drivers freeair-resonance. Depending on the drivers parameters and the chambers dimensions a drop of more than 10Hz is possible. Also the Qts increases slightly to the final Qtb value. The Phoenix shows hardly any drop of Fs and rise of Qt. The values nearly remain the same as under freeair condidtion.
Using similar drivers as in the Phoenix the Ripole may achieve a lower bandwidth limit. Due to the smaller chambers the cavity resonance exhibits a stronger peak, which is cancelled out by the passive correction network.

3) Driver Parameters:
The drivers of the Phoenix exhibit a low freeair resonance Fs and feature a low Quality-factor Qts. A low Fs is wishful since the built-in resonance Fb remains the same as the freeair value Fs.
A low Qts value is not at all wishful in a dipole, since we want a built-in value Qtb of around 0.7. The driver in itself is vastly overdampened. This asks for considerable electrical equalization (high-Q). This in response asks for a rather special equalizer like the Linkwitz-Transform, combined with a Subsonic-filter. Together with the low Fs (soft suspension) this may quickly push the driver into the overload state. Afaik there are XLS-versions with higher and more convenient Qts values (car-audio range) that I would prefer over the low QTs versions.
Drivers for Ripoles on the other hand feature slightly elevated Fs and higher Qt values. This is due to the demand that Fb be not much lower than 20Hz in any case and the cabinet- and(!) EQ-network related drop from Fs to the final Fb. A low-Fs driver would exhibt a too low and counter productive Fb in a Ripole.
It utilizes drivers with Qts around 0.5 that show best impulse behaviour and need low values of bassboost if any. The lower value of bassboost may be implemented with a simple HP-Filter of 2nd order (Subsonic-Filter) which is often a built-in feature of Subwoofer-amplifiers.

4) Cost:
The XLS drivers are better equipped using a cast basket and improved motor system instead of the pressed steel of the SLSs. They feature increased excursion capability. A nice feature of the SLS is that the suspension system exhibits a strong decrease in compliance just above the linear excursion limit. This helps to keep the driver safe when driven hard and beyond the range where the voicecoil exhibits good control. You can really push them and push them hard without destroying them.
The XLS cost more than twice that of the SLS. I´d prefer a pair of SLSs in a Ripole over a single XLS in a Phoenix at roughly the same cost in any case.

5) Looks:
Since the drivers are rather hidden inside the cabinet, the better looks of the XLS drivers won´t come through. It´s the cabinet design which is responsible of most of the optical impression. The Ripole beeing considerably smaller, which looks more pleasing and smarter to many people. WAF of the Ripole is quite high due to its small size and it not looking like a loudspeaker on first glance.

To answer Your Q which one is superior....well, it depends on what You want and what You are willing to pay for. Sonic differences are rather small compared to the improvements already gained by a dipole against BR and alikes and they are easily swamped by the positioning in the room etc. The cost-benefit- and cost-value-ratio certainly speaks in favour of the SLS-Ripole.

jauu
Calvin

[OllBoll]

Yay for lots of info!

Since I've read that these subwoofers also seem perform good when crossed higher I've thought about not only using as a subwoofer but building stero woofers and thus wondered how high the Ripole/Dipole magic works, up to how high in hz it is superior in SQ to conventional BR, I asked in Bipole woofers, until how high hz are they awesome? but lets take this exact Ripole as reference.

And if I cross them higher, does this somehow saturate the drivers and affect the SPL performance of 20-40 hz or do I just need to feed them more watts?

The Phoenix woofer also has a general recommendation of VA / Vrms for the driving power amp, what amp specs would be recommended for a single dual SLS Ripole woofer? ( With a flat frequency response from 20 hz up to crossed hz )

Thanks
Olle

[Calvin]

Hi,

the upper bandwidth limit is basically related to the size of the cabinet and as such the size of the drivers. Smaller drivers allow for higher upper bandwidth limit, but even with 7"ers I´d not opt for higher than 300Hz and not more than 200Hz for 12"ers. The problem is that the chamber resonance that peaks somewhere between 200Hz and 350Hz is of elevated Q-factor, meaning a slow decay. While it is possible to linearize the amplitude response so that the peak is flattened out, the long decay still remains and remains audible -at least to my ears.
I prefer a direct radiating dipole above ~100Hz and that´s the reason why my ESL-systems feature direct radiating A-style dipole basses.

If done right a dipole bass doesn´t need much power. Somewhere between 50-100W should be more than sufficient. Just take care of the reduced impedance of the paralleled drivers. The correction network may reduce the impedance a bit more. With 8Ohm nominal driver impedance You may end up slightly below 3Ohms. So the amp should work stable into low impedance loads. Some guys claim they needed much more powerful amps, but I assume that they simply made something wrong.

jauu
Calvin