Supplemental subwoofer

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silvershadelynx

Member
Joined 2016
#1
Hi,

I built my own pair of electrostatic panels and they measure about 200 cm x 68 cm. (see topic: https://www.diyaudio.com/forums/planars-and-exotics/357561-stats-model-4-a.html)

I've read about some electrostatic panel users who supplement them with a magnetic subwoofer, Like Jazzman who uses a ripole subwoofer: Jazzman's DIY Electrostatic Loudspeaker Page: Ripole Subwoofers:

I'm wondering if in my case it makes sense to build a set of these ripole subwoofers? The initial idea of my stats was to make them rather big in order to get enough low frequency range. And even though I'm quite satisfied with their low range performance, compared to my boxed speakers they lack a little puch.

Any idea if it would make sense to built such a (ripole) subwoofer, as my stats are already quite big panels?
 
#3
silvershadelynx said:
Hi,

I built my own pair of electrostatic panels and they measure about 200 cm x 68 cm. (see topic: My new stats, model #4)

I've read about some electrostatic panel users who supplement them with a magnetic subwoofer, Like Jazzman who uses a ripole subwoofer: Jazzman's DIY Electrostatic Loudspeaker Page: Ripole Subwoofers:

I'm wondering if in my case it makes sense to build a set of these ripole subwoofers? The initial idea of my stats was to make them rather big in order to get enough low frequency range. And even though I'm quite satisfied with their low range performance, compared to my boxed speakers they lack a little puch.

Any idea if it would make sense to built such a (ripole) subwoofer, as my stats are already quite big panels?
Click to expand...

I’ve grown to love my Ripole subs, but I hesitate to recommend them to others, because not everyone agrees with me, or appreciates what they don’t do (that wasn't a typo).

If you browse the subwoofer forum, you will find some praising their clean, non-boomy sound, and others condemning them for poor inefficiency and lack of chest thumping impact.

I chose to build a pair of Ripole subs for my system because they are compact, and I had heard that they don’t excite room modes to the extent that conventional subs often do. And they blend perfectly with my new Jazzman MkIII hybrid ESLs, which also use a Peerless SLS woofer.

In my case; I have the mid-bass woofers in the MkIII's chopped off, and the Ripoles coming in at 65Hz, using the 24db/octave LR filter in my DBX Driverack Venu 360 crossover.

Some might consider these weaknesses:
1) Ripoles, like other dipole subs, have the woofers in free air, so it doesn’t take a lot of power to bottom them out at X-max.

2) There is a rather loud chamber resonance that peaks at around 250Hz (peak frequency varies with woofer & chamber size). Since I’m crossing the Ripoles in at a very low 65Hz using a steep filter; the chamber resonance is not excited and it isn’t an issue for me. If I wanted to play them up high, near the resonance frequency though, I could tamp down the resonance by overlaying a parametric EQ.

I will share my Ripole sub drawings with anyone who wants them.

Charlie (Jazzman)
 
#4
Thanks for your extensive reply Charlie! As I'm still curious, I think I will just try to build 1 subwoofer first and maybe later a second one. I can imagine I want to cross it over to my stat panels at lower than 65 Hz.

I think I will use your drawings from your website to build a first prototype in MDF, just to see if I like the sound.

Is the Peerless SLS-315 the same driver model you used for your subwoofer?
 
#6
Currently I'm building a rough test model. I was wondering how important it is to seal the small gap between magnet and box? (I have a very small gap (+about 0.5 millimeters))

Why not put an extra sheet against both sides of the 'box' where the magnets are?
 
#7
I don't think a gap that small between the magnet and cutout, in an open-ended cavity, will matter much at all.

Mine has a 1/16" gap designed in for clearance; which although I sealed with a foam rubber gasket. I don't think it would have mattered if I had left the gap open.
 
#9
Hi, 1 subwoofer is finished, and tested. They don't add colour to the music like my boxed transmission-line 2 way speakers do, which is a positive thing. They have an easier job making low frequencies than the 6,5 inch mid-woofer in my TL boxed speaker. (I used my DSP to correct frequency response)

They are a positive addition to my full-range esl's, but after combining them with my much smaller els's (an old diy model which measures only 20x100 cm diaphragm dimensions), crossing over at 100 Hz, 48 dB/oct, this seems to be a very nice combination! Deep bass and clear mids and highs...

So to conclude, it was really worth the effort! They (ripole + small esl-panels) definitely sound better (cleaner / more open) than my TL boxed speakers.

So I will order another set of these woofers to build a pair of them!

Another question (to Charlie): I read on your website about dimensioning Ripoles:

"Area of front chamber opening should be 1/3 to 1/4 of woofers’ piston area (SD). For woofers having more than 10mm X-max, use 1/3 SD minimum.For woofers with 10mm or less X-max, chamber area can be 1/4 SD."

After calculating front and back area of Ripole Sub version 3 (link here), it seems your design is a bit off? (although to me it sounds impressive):

front area: 3 5/8 inch * 14 1/8 inch = 51 ^2 inch
SD=81 ^2 inch
front area is 51 / 81 = 63% of SD => can be 25% (38% off)

rear area: 3 5/16 * 14 1/8 * 2 (openings) = 94 ^2 inch
SD=81 ^2 inch
rear area is 94 / 81 = 115% => should be 50% to 100% SD (15% off)

Assumed that my calculations are correct (?), the front area shows the largest deviation. Did I forget / miscalculate something, or is there a reason why front area is much bigger than the rule states?
 
#10
Actually; I had already cut the wood details for my Ripoles when I discovered those guidelines you referenced. BTW; those guidelines were originally posted by Rudolf in the DIY Audio subwoofer forum. Rather than starting over; I opted to assemble the pieces I had already cut, and it worked out OK.

I took the liberty of re-posting Rudolf's guidelines in the Ripole writeup on my blog page.

I also built a second, wider center section, which would make the front chamber opening meet the guideline. However; the first one I built works just fine and it looks better aesthetically, so I continue to use it.

In any case; glad you like the results of your build!

Charlie
 
#13
CharlieM said:
I also built a second, wider center section, which would make the front chamber opening meet the guideline.
Click to expand...

Thanks for your reply! I still don't get it 100%... If I'm correct you write that the front chamber can be wider rather than narrower / smaller, but I would think, according to the 'rule' of 1/4 SD, it should be smaller?

Just to be sure:

SD = 81 ^2 inch
1/4 * 81 = 20 ^2 inch (suggested area for front-chamber for this woofer)
20 (front-chamber area) / 14.125 (height of front chamber) = 1.4 (width of front chamber)

This suggests that the front chamber can be much narrower than your design? (1.4 instead of 3 5/8 inches)?

I hope my question makes sense and I didn't make any errors...
 
#15
...thanks again for your reply. That makes sense, in that case I made an error in my calculations.

To summarize: should I take 1/4 (in case of Xmax < 10mm) of 2*SD for front opening?

In that case your numbers are closer to these guidelines:

front area: 3 5/8 inch * 14 1/8 inch = 51 ^2 inch
SD=81 ^2 inch
front area is 51 / 2*81 = 31% of SD => can be 25% (6% off)

Would you think this calculation for the front chamber is correct?
 
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