Most powerfull 15cm Scan Speak revelator based driver

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Hi Fellows DIY'ers :), autumn is here and having some more free time, I thought it would be nice share some interesting(I hope so) data for DIY'ers.
Have you ever wondered how lets say.. Bethoven's 5 symphony or Queen"We will rock you" would sound throught small monitors(~10liters) in realistic(enought) SPL levels? By saying realistic I mean REALY realistic. I believe here would be guys not only who wondered but also who tried. And of course failed. At its best. At worst there is more fun- In past have received for repair exclusive and quite expensive (as monitors) Sonus faber Amator Mk2, System Audio Sa2k speakers where coil was smashed or burned. I asked why owners do that- most say- "I listend to energetic music and with inreased level I get more sound wawes energizing room ,more musical involvement up to the poisnt when sound started sound muddy and sudently sound stopped" Usualy theese guys do not listen "mumbo jumbo" electronic music but rather clasical orchestras,operas and other complex recordings.

As an audiophile I have listened to some small speakers which are considered one of the "biggest" sounding monitors (like Sonus faber Auditor M, Proac Tablete, System Audio sa2k) with eficienty ~84 they play nice up to ~93-95db/3.5-4meter at their best. if we want to feel sound notes vibrating crank input power more than ~80-100w and then...

as an speaker designer I know what has happens. but what wonders me most that theese people do not go logical way- to get bigger speakers. they jut want ~10liters 5inch 2 way.I do not know exact reasons it could basicaly anything (astethic,compactness, subjective quality form smaller driver) during one coversation on phone I said " I know I know but.. OK -just be carefull with your wishes" :devilr:

In short- on special order I decided to build small,compact monitor speakers(no more then 10liter internal) with no more than 5 inch driver which CAN KILL anyhing in its class and two class above ,but NOT to KILL themselves (as it hapened to owners of theese small speakers)

Money was not a concern on this project, but I already knew that there will not be in market 5 inch driver which can do what i want. there is some bigger drivers like Adire extremis 6.8 , but it require bigger box and still it wont handle big power due 40mm VC and its midrange quality nowhere to smooth scan speak 15w midrange

Unfortunatley neither Scan speak or Seas did not agree to produce this kind driver for me. not posible automaticaly to their designed drivers baskets/cones combo.. So only thing which is left was DIY. I have builded/assembled some drivers in the past but never so small size.

I wanted -

1)no less than 150W REAL input power. most 5inch have 40-60w. no matter what datasheet says ,we can not cheat physic(yes I know.. but liquid cooled woofers in no- go, because of excursion and hermetic). So I needed bigger coil,as eficienty would be no more than ~83db at its best( bigger VC weights bigger) and to maintain eficienty as much as possible I decided to go with 2 layers coil instead 4.

2)no less than 20mm nominal peak to peak excursion. it may sound crazy as most 5 drivers have 6-10mm peak to peak linear excursion untill VC leaves magnetic field. my only wories was how to imlpmement this excursion is single small spider and limited spider diameter.

3) and absolute nessesary vented box-with power like this and excursion like this I did not wanted tiny "kick drum"..

I didnt wanted enlarge basket,or spider -just wanted drive to look like ordinary 5 inch from outside. and to fit in 5 inch box. I knewed that I am going to trouble , mostly mechanical problem- how to having so much vc lenght esnure enought mechanical excursion from 15w rubber and spider as well as fact that i would need reduce driver CMS at least by 200%. otherwise motor will smash cone in outgoing excursion at higher input levels (~>100w) Another problem is that motor nominal excursion is slighty bigger then bigest posible mechanical excursion of 15w structure. that sounds like 1200HP engine mount on stock ww beetle. auch!...

so even knowong that some will fail I decided to build 4 prototypes(one- version C actualy for fun only) -

1)version A-stock scan speak 15w frame,cone,surround,spider is original but hardened. VC 50mm from scan sepak 26w revelator, magnet from scan sepak 26w revelator

2) version B-stock scan speak 15w frame,cone,surround,spider sourced from Focal . VC from scan sepak 26w revelator, magnet OEM Scan speak (built to specifications- 1.5mm larger hole- for 50mm but 4 layers coils.

3) version C-stock scan speak 15w frame,cone,surround,spider sourced from Focal . VC from scan sepak 23w4557 subwoofer, magnet from scan speak 23w

4)version D-stock scan speak 15w frame,cone,surround,spider is original. VC 42mm from scan sepak 18w4545 clasic, magnet from scan sepak 18w4545

actualy cones was sliced wood fiber ,not sliced paper, but astill scan speak made.

Version 4 was safiest shot to drivers mechanical structure as the only thing I change its VC diameter, and magnet. unfortunatley after measurements and testings i didnt finded any SIGNIFICANT improvement on power handling (~+30w) until coil started to heat and resitance went up. eficienty reduced by 0,8db. it sounded better but not so much that would be trouble worth

versions A/B/C needed reworked structure as 26 and 23w had extended cooper rings (SD sytem) and tiny cone would hit in inward at max excursion at same spider level. I lifted basket from magnet by 4mm(5mm for C version) refixed with longer srews and things went better.

coils formers from 26 was need extended by 8mm to fit 15w.i used kapton 50mm VC frmer from peerles xxls subs. glued with ultra strong an light loctite glue.

It took some time to 50mm coils to cone and reworks spiders, srew news holes in magnets but we may pass this chapter.

Assembling. there was no questions about mechanical "fixed" centering only "live"- no spider behaviuor is ideal and live centering is the only way to go with excursion like theese on such small spiders. my "insurance" was version B (with extra space in gap) which i belive could be centered and VC do not scrach at maximum excursions. but to my surpsise both 26w coil versions was centered good. I used Technicoll 2 components epothermic reaction glues.1min time which actualy 5-6mins- more than enought to solder wires and prepare generator. most important last 30seconds when glue starts to get hot and it glues strongly. in theese 30seconds I need test in variuos frequencies (10-70hz) and whats important in this case- at extreme excursions.
version C centered also well but i wasnt able to to test it at max excursion(physical drivers contruction limits)
I used lightest glues not not add extra weight to driver(it already have much weightier coil than usual)

first measurements wasnt a surpsise as a reference i used 15w4531 driver (all prototypes also 4ohms) it have eficienty of ~85db( sensitivity nearly 88db) .
version A was 82db, B 80.6db, C 81.4db D was 83.8db of course frequency response after 3 khz sharply roll of,comparing with stock. but in lower midrange it was basicaly the same form A version.

now excursions - A and B versions have 18mm linear excursion peak to peak, while maximum is so so 24mm C version had 24mm nominal excursion, maximal excursion was also 24mm- as expected too long coil for 15 spider/surround structure.

MMs was A- 19g, B-19g, C- 23g, D- 14g
Fs was also on the high side varying from 45-to 65hz depending on spiders stifness I used. on some frequencies spider noises can be heard at extreme levels. one of the driver just started to moove during air-free test!

so I fitted Smart with 1400hp engine, what's next?.. of course music test! I mountened them all in 10 liter ported to 48Hz box builded from 33mm MDf. Port tube was chosed 74mm.
I decided to conect not SE class a monoblock but icepower 1000 module.theese have better control and so much power than amp will never go to clip before drivers. I putted some midbass based music maked 4 type swicher and low pass at 300hz to heard anomalies better.I found on hand .It was Tina Turner & Barry White - In Your Wildest Dreams. started from level level ~20w. same -as stock 15w . 40w-same as stock. 60w-seems ABC plays cleaner, 70 w ABC plays MUCH cleaner, while stock 15w VC leaves gap- it can be heard very easy as "emty sound" or "blurping? 100w ABC plays clean, 15w vc scrathing and jumping out of gap, 110w- 15w stock coil jumped out of gap and coil is bented. one warrior is lost-15w stock is out of game. 120w-still damn clean!. 130w still clean! 150w- hear some small noise from A, but stil all overal clean . 160 W- starting to hear mechanical kicks at both extremes(need stiffer spiders, but considering how much time music will be listened at theese input power it snot best solution) but still not a sign of VC leaving gap! sudenly i noticed that my studio door and its knob vibrates. and that is from single tiny 5 inch driver!.. I choose A as best driver, as B eficienty was too low and not much benefit with careful centring. version C was not considered as sucesfull- to benefit fully from 23w4557 motor 95cm2 cone should be fitted with much wider basket and much wider spider and surorund. 18w revelator with some basket mods could handle this excursion .but not 15w.. . and i wanted to stay with 5inch

test 2 was performed later with finiched xover in stereo now I listend not only electronic bass but also opera, chamber music, I picked very dynamic passages and for the first time I could hear such small speakers play so CLEAN at very high levels with no compression.and diferenciens was not in the bass range only but mainly in opera vocals -dybnamic sounded not compressed. midrange clarity is sligtly diferent from stock 15w- it less boring on vocals -more grip, while stock 15w more "calm"
technicaly speakers perform as almost 2x 15w but still subjectively have some better grip and atack transient. I turned up lights. It was first time when I heard pink floyd's dark side of the moon "brick in wall I" and qeen "we will rock you" trought 5 inches and felt quite trong air pressure wawes reached my chest. and after light on there was small inocent tiny speakers . one moment I almost understood desire for that kind of speakers.. just for one moment..

ataching midfield measurement aligned to 1w/m input(not 2.83v) of succesful A driver. also photo of driver A vs scan speak 15w.

Hope you enjoy this reading. I definatley would not say "do not try this at home" :) -feel free to ask any aditional details if you want. good luck in projects!


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Very cool work! Yes it must be a small speaker and playing loud.

Had you gone for a 6.5" (16.5cm) you might have just one of mine. It will do 108dB on any day in its 3/4"MDF cabinet of 7"x10"x16" tall.

Really like what you have done. Shows clearly there are other solutions and ways to get from "here' to somewhere useful. So many are rigidly stuck in their paradigm they would declare this impossible. BRAVO to you!


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Wow, really good work! That looks like a lot of effort to do, surely this type of driver has some place in the commercial market, its merits have been proven here.

You know what I'd really like to see? A midrange unit (high fs, ~100Hz) with 50mm voice coil, about 5" diameter, shorting rings (generally low distortion motor), high efficiency (over 90db/w/m), a hard cone meterial and a neodynium motor to allow a very well vented rear side.

Nothing seems to tick all the boxes! I expect the high fs and efficiency is hard with a heavy 50mm coil, but to get really great dynamics it seems necessary.
Very cool work, You can clearly see the effects of the large coil on inductance (as seen in the top end response and certainly on the efficiency, but that's neither here nor there for your task (max output in small cab/driver format). Very impressive indeed. I do wonder how long the adhesives will hold up, you'll have serious thermal buildup if you're leaning on that (meaning- sustained high input power) in a tiny little box. A lot of us go for high efficiency and minimum heat, this is essentially 100% the opposite.

Proper DIY FTW!
Wow, really good work! That looks like a lot of effort to do, surely this type of driver has some place in the commercial market, its merits have been proven here.

You know what I'd really like to see? A midrange unit (high fs, ~100Hz) with 50mm voice coil, about 5" diameter, shorting rings (generally low distortion motor), high efficiency (over 90db/w/m), a hard cone meterial and a neodynium motor to allow a very well vented rear side.

Nothing seems to tick all the boxes! I expect the high fs and efficiency is hard with a heavy 50mm coil, but to get really great dynamics it seems necessary.

thanks for kind words, this driver still is compromise -last mm of boths extremes excursions is degraded and original idea can be imprroved with double position spiders and special surround. but frame should be designed from scratch then..

well 5 inch with 50mm coil and 90db eficienty is tought thing. but almost posible.I have some 5.5inch midranges 52mm coil with 94 to 99db/2.83v/m sensitivity in operating range(4ohm also) they use audiotechnology motors and cones. but designs like this need steep high pass filters(nominal excusrison is only 2mm peak to peak)

if use aluminium wire on former and make 2mm p-p excursion it could be posible. I also belive there is such OEM designs.

but 5inch midwoofer I builded is diferent story- it have one clear benefits have absolytely high WAF factor :) - fits in 8-10liter box and can play efortlesly at seriuos levels. if going bigger I would go for 2x15w or 1x18w but in 8.7 liter and port with 85mm (74mm was too small)this actual speaker in listening tests outperformed (when input more than 80-100w) jm lab Diablo(double sized and having 6.5inch and very clever designed IMHO driver) and some 2way floorstanders with 8 inch seas driver. but 150-300w of clean power is a must for theese babies. again there is hamlets questions- either speaker big or amplifier big :) fortunately amps are much smaller, and such speaker with class b or d amps can be elegant and powerfull solution. at least i wouldnt mind if that kind of well.. litle bit odd driver and conseption :) would be available from manufacturers.
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Neodymium magnet and passive radiator in total could make significant volume reduction in cabinets below 10l. If you're into this level of fabrication maybe you could get a heatsink from the woofer to ambient without a fluid loop (I don't not understand your "hermetic" comment). Just using an aluminum cone on the passive could be all you need. With all that excursion there's going to be a lot of forced air whether you like it or not. At this level of fabrication you may as well make the passive radiator yourself. Instead of loading the cone at the center do away with all the cone flexure and distribute the mass In it. It should be so strong that it may as well be flat. Make it out of two dissimilar metals with a high damping glue between them. Of course aluminum shoud be one of them. (This technique is used in most modern HDD package noise control.) Thermal conductivity of the glue is not very important. Too much surface area. Good luck tuning. It might not be right on the first shot but it seems like you know how to get there from here.
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Hi Andrew, thanks for the hint.
However inspite being very big fan of Passive radiator implementation(my personal sepakers low frequency modules covering 20-55hz range cosist of 16x scan speak 23w4557 subs each in 27liters with 16x scan speak 23w0 passive radiators) I see few problems here in SMALL2ways project-

1)Passive radiator would not rise drivers power handling.Most critical part for speakers VC overheat is surface area. ventilating,heat transfer and other being only second much more insignificant factors. Its best to start improovements in problem where they starts- in VC area.

2)passive radiator will not add any aditional linear excursion. it can be done only physicaly. it will change drivers behaviuor at excursion versus ported of course but thats another story.

3)passive radiator will take some extra internal space,block internal air flow(comapring with ported) and still will not be as high in level as simple port(if we usse normal mass radiators of course) I would say passive resonator (tuned LOW) have benefit to add more lowest frequency range response but port have better SPL level(considering surface area of driver/resonator)

4) Yes with radiator it would be posible to make some 18cm which would work well in 8-10liter but originaly idea would lost there- 18cm need wider front bafle and speakers starts to be bulky. 15cm enables to have very WAF friendly "cuties"

5th element- my notebook was dead at that time, but i did some 2/3/4 discortions tests on other pc where i had "simple champion" :) or something like this software. if memory serves me well modified driver didnt "shinned" in 3.7-4khz very much area comparing to stock.. but as working range was 2khz i didnt pay any seriuos attention to that..
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