Another try on raal omnis according to dlneubec's contrappesos

[tubepit]

hello ht-guys
i'm pit from germany and start this thread for building a clone of raal's smaller omnis the ones dlneubec had a try on.
first let me say a few words to my person. my main profession is guitar teaching ( i've been studying classical guitar at the conservatory nürnberg ). added to that i'm also building guitars classicals western and also electro guitars. since long i'm a diyer from repairing my car to building a cnc-router.
to speaker building i'm quite new. what i've already built is an open baffle speaker using two 12"speaker fullrange and on top a beyma bullet tweeter cp22 separated by a condenser only just built on an afternoon and screwed together. but that's also the way it sounds like that means for to make it sound good i have to work on some crossover. what i like from the current state is the dry and punchy bass without boomyness. but this alone doesn't make it a good speaker ;-)

not too long ago my brother was asking me whether i want to build a speaker system for him. cos i'm reading on speaker building forums since long ( and this ht-guide is one that i really do appreciate ) i could make a few suggestions and the raal omnis is the one he has choosen.
what can be found on the net about this speakers i've mostly read. especially dlneubec's thread about his contrappesos i've already been reading a few times. i've to say this is very well documented by dan !! thanks for sharing your experience. it's also very appreciable that aleksandar the designer of this speaker is chiming in and telling the ideas he had when he designed the speaker and what one has to care about to not change his design. again i have to say thank you aleksandar for sharing your knowledge with the diy-community !!

in the following i'll describe the actual state of affairs :

i've already bought the wideband speakers that will be used for the midband and if you follow the link you can have a look at it :

http://www.spectrumaudio.de/breit/tangband/tangbandW3871A.html

looks like these are quite well build and i'll cut the surrounding of them down to 80 mm diameter 'cos the stainless steel tubes they will be fit into have the same diameter. i'll work the same way dan did and cut those tubes into three pieces so it's easier to fit the tweeter. into the middle tube a slot will be laser cut and maybe also the holes for holding the tweeter.
for the tweeter i want to use a ribbon tweeter but the fostex tweeter raal suggested is hard to find at least here in europe and if you're able to find it it's very expensive ( think it's sold for around 130 euro a piece ).
i've found a few others that probably could be used instead of the fostex but i don't know exactly what specs they have to fulfill. it's clear they may not be too large that one can fit them inside the tubes. but the other specs ? maybe somebody can tell me something about that ?

these i've found :

http://www.ebay.com/itm/Monacor-High...-/231266835977

( they are affordable at 109euro a pair. can be used upward from at least 4khz or higher and spl is 90 db )

another good candidate :

http://www.oaudio.de/Lautsprecher-Chassis/OmnesAudio/Baendchen-Hochtoener/OmnesAudio-Baendchen-Hochtoener-RT-3-5H.html

( nearly the same price but higher spl round 95 db. the horn i'd screw off and the cube at the backside i think contains the transformer and can also be screwed off then it's possible to fit them inside the tubes )

does somebody know whether magnetostats can also be used in this application ? maybe something like this :

http://www.monacor.de/produkte/lautsprechertechnik/hi-fi-hochtoener/baendchen/rbt-95sq/

( from their size they could be easily fit into the tubes. spl is quite high 98db and price is also 50 euro )

no matter what will be used and fit inside the tube the ribbon will be distanced at least 15 to 20 mm from the slot of the tube. i know that raal mentioned that it'd be an advantage to keep the slot quite narrow ( also the slot of the spacing of the two tubes ). it would be quite easy to rout a plastic piece on my cnc that connects the tweeter to the tube slot but i dont know how this "channel" should be sized or which curvature it should follow ? maybe somebody has an idea how this should be done ?

dan also used some foam pads on top and at the bottom between the tubes to form kind of a waveguide or horn. would be quite easy to cnc-rout something like that but i don't know which curvature it should follow to work best as a horn or waveguide. in the end it will look similar to a jbl 2344a-biradial-horn.

i want to build the woofer the same way dan/aleksandar did. let's say a tube with a diameter of 300 mm and a woofer on both ends. when i toy around with winisd with a closed box ( with 60 to 80 liters ) i will get down not deeper than 50 to 60 hz. i think with a vented box i could reach deeper but a closed box design has the advantage to sound less boomy if i'm right ? probably i'm not useing winisd correct i don't know. how deep could i reach in the best case ?

crossover will be active with the behringer ultra drive pro dcx2496 so i can toy around with different x-over frequencies and different filters.
okay i will have to use six poweramps to drive the speakers but if i'd use a gainclone design it won't be so expensive. probably something like this :

http://www.ebay.com/itm/6-X-100W-Cla...item51c3d45601

as far as i'm informed 'til now it's not unproblematic to manage the volume control with the behringer device. it would be best to put the control between behringer output and the gainclone but with volume potis it won't be practical. does anybody know a possibility how to manage this otherwise. probably i can do it electronically with a sort of volume ic ?

this is how far my design ideas have grown. don't know whether my decisions are correct and hope there are knowledgeable guys in this community who can and also want to give me a little help on this project or tell me if i'm right or where i'm wrong.

thanks in advance for giving me some support.

best regards

pit

[JonMarsh]

Hello Pit! I'm still on the road, bringing that weird Yamaha GTS1000 home, but I'll take a real close look at this soon this coming week and get back to you! There's just been so much going on lately... at least, it's not boring! :W

[tubepit]

Hello Jon,
wow, this yamaha really looks like a weird bike! never seen something like a single sided swingarm to manage steering. is it easy to ride ? i had a look on the map( i'm an geographic idiot )and it looks like picking it up in seattle and riding home is a ride down the westcoast. do you take the direct route or do you ride down the coast ? looks like riding down the coast would be a joy ride ?
being on the map i had a closer look at Livermore. are those lakes nearby the results of gravel extraction? in the first moment it came into my mind that this could be one of those fracking areas !
gladly it doesn't look like that !! not too long ago by accident i've been watching a movie on youtube named "gasland". uuh, man, i got sick from watching this movie. after 10 minutes or so i was wondering "do i really want to see this or want to know what they ( they means those energie companies and the govt that stands behind them ) are doing ?". nevertheless i've been watching 'til the end of the movie. as a result i felt like beaten in the guts. and i've to say this doesn't happen too often ! did you ever watch this "gasland"-movie ? it's a documentation a guy who was offered such a contact for doing fracking on his land has made it. before that i knew this technology is existing but not much about it. one thing is for sure: you will find me in the streets when they want to do this in europe !!! sorry for this digression it's not the theme here but those lakes brought it back into my mind. ( but if you haven't watched this docu you should ).
okay, back to the roots äh, no, the issue of this thread :
it's a pity besides you nobody seems to be interested in this thread or on giving me some explanation/answer or at least a hint in the right direction ? is it written in the wrong way ? sorry for such a stupid question but this is the first time i ever opened such a thread and maybe there a some secret rules one has to follow ?!
nevertheless i'm hard tensioned ( this is a german expression maybe not possible to say so in english ? ;-) on your remarks concerning my questions !!
i also want to encourage everyone to chime in and give his or her two cents !!
all the best

pit

[CraigJ]

Hi Pit,

Sorry that you haven't received the response you were hoping for. I had hoped that Dan would respond, but I don't think he is as active in the diy speaker forums as he use to be. Also, if I remember correctly, Dan didn't get many responses to his omni designs either. Perhaps some of it is too foreign for most of us?

That being said, in the original thread, I had asked Aleksandar to join our conversation and was surprised by how open he was about his design. Although I didn't document the system like Dan did, I did make a system based on Aleksandar's design, or my interpretation of it for the midrange, and had very nice results. The one big issue I had was not knowing how to accurately measuring an omni system in a room setting.

Oh, I also couldn't get some of your links to work. Good luck and I'm sure Jon will chime in when he returns with his new toy.





Be careful, you'll end up making something like this;

[tubepit]

Hello Craig,
thanks for your reply. when i was reading dan's thread i've already noticed that you also had a try on the raals. good to hear that the result is pleasing.
concerned to the links in my first post : I've already edited them last night and if i click them today they seem to work.only the one to the behringer device doesn't work but i think you know it.
what sort of tweeter did you use in your design. i'll surely want to build it like aleksandar and mount it inside the tube fireing into a narrow slot. as i understand your writing in dan's thread you did it the same way ? did you fit something like a waveguide to bridge the gap towards the slot inside the tube ? what size is your slot ?
i've already written that it would be no problem for me to cnc-rout a waveguide or horn part the keeps the distance between the tubes and is forming a double sided horn comparable to two jbl 2344a-biradial-horn back to back. do you know which curvature it should follow and how let's say deep it should me made ?
for the mids now you can click on the link in my first post and have a look at. i think they would do the job.
the fostex ribbon tweeter mentioned by aleksandar is a little expensive. so which requirements the ribbons have to meet ( spl and freq.range )and would one of those from the hopefully now working links fit in or which one would be preferable ?
if i understood correctly as woofers you're using pe RSS315HF-4s in connection with that sonotubes ? how deep do your woofers reach ? if i want to reach down to 50-40 hz and play around with winisp it looks like this would be impossible with a closed box design ( is this correct or do i probably not use the prog correct ? ) ? more easily i do get down that deep in a vented design but the way i see it it would destroy the advantage of a closed dipol box to not excite the room modes that strong ( if my assumption is right ? ) ? can i say it's a dipol if both woofers at the same time are moving outwards and vice versa ?
do you think it's necessary to invest in such expensive woofers than yours ? the speakers will mostly have to play at normal listening level i've to say. when i remember correctly dan said his speakers don't reech that deep but he isn't missing those deepest frequenzies ?
'cos of the picture in your post : couldn't you resist to build those large raals and if you couldn't do they sound good ?
in dan's thread you've posted a picture of a big raal ribbon so you do own a pair of those ? i would not be able to invest in a pair but i think they could be quite easity be diyed ? the most difficult parts would be the ribbons but you can buy them as exchange parts at a low price of 70,-$ i've seen. okay at dampening of the back chamber would need some testing but i think this problem can be solved. maybe the dimensions and size of the front slot is quite important but this can be estimated from pictures or if you own those you probably could measure it.
regarded to aleksandar : i also was quite surprised by his open talking 'bout his design. that's really appreciable !!

okay enough for the moment i have to go on my duty ( is it possible to say so in englisch ? also i hope my english is not too bad ;-)and start teaching guitar.

questions, questions, questions flooding thru the mind of a speaker building newbie ;-)
i'd be glad if you and maybe also others can give me some answers or insights at those issues.

all the best

pit

[CraigJ]

Hi Pit,

I don't have a lot of time, but I'll try to answer some of your questions. I made my mid-range pvc sections the length that Aleksandar recommended for closer driver spacing and crossed over to a BG Neo3 PDRW. The Neo3 had all slots but the center slot covered, including the back, and was placed between the two pvc sections. So instead of inside the can, the tweeter was placed between the cans and the distance between the side of the can and the actual planar element was adjusted per Aleksandar's suggestions (or so I tried). I assumed, right of wrongly, that the can pointing towards the center of the room still acted like a waveguide, as Aleksandar commented.

This project for me was really more about what do omnis sound like, than lets get the most accurate (insert your own term) sound out of the system. I have a very bright sounding room with 3 walls of glass, only a big leather couch and throw rug over hardwood floors are sound absorbers. For the price of pvc and two 12" sonotubes I was able to test whether I like the sound of omni speakers in my room. I did spend hours with a mic and Fuzzemeasure removing the bumps and dips in the frequency response. As mentioned, the hardest part for me was determining at what distance, or distances, to measure the speakers since so much of the sound is coming from the room.

The RSS315HF's were replaced by a pair of Aura NS12s because I felt the NS12s were able to play higher in frequency and did better in the smaller sonotube. Regarding the woofer choice, I believe Dan used an inexpensive woofer and was satisfied with it. I just try and recycle what I have on hand so as not to accumulate too many extra drivers, which is one of the benefits of a digital crossover. Oh, and I never could get the big Raal ribbon into the small pvc tube.

Perhaps an email to Aleksandar will get a response?

Craig
Ps. I only made one big Raal clone. It sounded very good for mono, but was way too big for a pair in my room, not to mention extremely top heavy when made out of mdf.

[tubepit]

sorry i did a double post. the following one is what i expected to post

[tubepit]

Hello Craig
sorry for my late reply and thanks for yours. so my speculation that you have the big raal ribbon tweeter seems to be true ? did you already take it apart and have had a look inside ? i think it won't be that complex to build a clone and buy the original replacement ribbons ? damping the back chamber has to be done to suppress resonances and okay a diy-transformer would be a challenging task. i think in a diy ribbon tweeter the heavy stuff is to make a good ribbon but there can't go anything wrong when using replacement ribbons.
related to the big raal omnis you've built they would also be too large for my brother or myself.

the tweeter design of the small raals in your case is different then raal's if i'am right. if back wave and front wave of your design are compared then i'd say they are out of phase one is going positive and the other negativ ? if waves travel around the tubes and meet they do cancel out each other ?
i want to do it aleksander's way and mount a ribbon or a planar ( don't know if such can be used ? ) inside one tube and let it fire thru a narrow slot into the space between the tubes so that back and front wave are in phase like aleksander has explained.

hey what about all you knowledgeable guys here on htguide does nobody want to chime in and give me a reply related to the questions in my first post ??

have i done something wrong the way i write my post ? maybe i have disregarded some secret rules that have to be obeyed ? if this has been the case please tell me it's not been my intension to be ignorant or appear as a knowitall !!
isn't such a forum the place to ask questions and expect to receive answers or hints or where you are taught to find answers by yourself ? okay it's clear that it takes some effort to write a reply and i'm a newbie in speaker building ( although i've read already a lot ) but ask me something about guitar building and i'll tell you what i know.
i'm quite sure that here are knowledgeable people who can give me answers.
when i have opened this thread i hoped and i'am still hoping to receive some reply from anybody.

let me say it in frank zappa's words :

so i'm watching and i'am waiting
hoping for the best . . ........ ;-)

greetings from germany

pit

[CraigJ]

Pit,

Don't take the lack of responses personally, you have done absolutely nothing wrong. If you search "omni" in the Mission Impossible DIY section, you will see that Dan also received very few responses to his questions and also asked what he was doing wrong. My best guess to your question is no one, other than Dan, is that familiar with actually designing and building omni speakers at the HT Guide forum. Again, if my memory is correct, Dan was very much on his own with omni designs and just forged ahead with his ideas.

If I were to start over, I would look for an inexpensive used pair of the Fountek ribbons that Aleksander recommended and try to put them in the "can".

Good luck, and please don't stop trying to ask questions as someone much more knowledgable than me will eventually answer.

Craig

[---k---]

Yep. You've done nothing wrong. I'm watching, because I always like reading about the unusual builds. Unfortunately, I go nothing to add at this point.

[tubepit]

Hello Ryan,
thanks for your reply and respectively get me convinced that i didn't do anything wrong ;-)

as i already have mentioned besides i've been a gearhead since long i'm a total newbie in speaker building.
related to a few of my questions ( that probably look stupid but i'm a newbie ) i think some of the questions itself are not that exotic the whole project is ?!
for instance if you lock at the woofer section :
maybe it's impossible in this constellation to target for a frequency respons reaching down to 50 hz ? can anybody tell me how deep this constellation probably could reach let's say by using two 12" woofer working in phase and a boxed volume from 45 to 57 liter ( that means a sonotube that is 60 to 80 centimeters long ) ? what are the parameters of the woofers i have to look at ?

plaing around with winisd using a mivoc aw 3000 woofer in a vented design the frequenzy plot looks like this :



same woofers in closed box :



both boxes with a volume of 47liters. obviously the vented version reaches deeper but am i wright that a vented design sounds more boomy ?
are all these problems no problems when i'm using the behringer ultra drive pro dcx2496 and with it's help i'll be able to equalize the signal according to what i'm looking for ? okay there are a few borders that have to be obeyed. i think there has to be taken care of xmax of the woofers.

if we look at the tweeter :
besides that i have to manage to mount it inside one of the mid-tubes what spl do they have to produce ?
the drivers i'm using for the mids are Tangband W3-871B. they have a spl of 88 db. by using for of them how high should be spl of the tweeter ?

another question adressed to those who use the behringer ultra drive pro dcx2496 :
i found out that it's not possible to adjust the volume at the output of this device. the possibility would be to adjust the input volume but this lowers signal quality. would it be possible to adjust the output with the help of something like lightspeed attenuator ? it's a circuit that makes use of leds in conjunctin with ldrs as a substitude for volume pots.
somethig like this ( the pic is taken from a thread at diyaudio related to this circuit ) :


here you find more about it :

http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

maybe somebody is able to give me answers to these quite "unexotic" questons ?

nice times and all the best

pit

[tubepit]

sorry guys
i have to find out how to upload pictures from my computer to this thread. in my last post the frequency plots of winisp and pic of the circuit for the lightspeed attenuator are missing.

greetz

pit

[kevinm]

I'm with Ryan, can't help - but definitely watching

[tubepit]

Hi Kevin,

thanks for your reply. i have to go to this site and find out how it works as mentioned earlier this is the first time i opened a thread at a forum therefor i'm not aquainted with those things. but i will learn it. til now i couldn't find the time.

hav'a nice time.

greetz

pit

[JonMarsh]

This is a lot to digest but I'm working on it...

Note, just an observation, when you take someone else's design and try to change a lot of things in it (with driver selection and the like) then you essentially have a new design.

think about this, many people build MTM's, but if you change the drivers, you have to re-measure everything and develop a specific crossover for that set of drivers. This includes handling the differences that may exist in the actual driver time delay offset, which affects the phase in the crossover region.

Do you have a measurement system and some experience using it? This will be essential for the path you're currently taking, if you don't just build an existing design "note for note". With an Omni design, this may be even more of a challenge because you need to make good acoustical driver alignment at the crossover regions in all directions- this isn't a trivial issue, particularly for higher crossover points.

My thought about measurement is that in room you can get some useful data in the lower midrange and upwards, by using a short gate to screen out the room early reflections. I would suggest building a turntable such as the two I have, so that the speaker can be put on the turntable (like a Lazy Suzan, we call it) and rotated while the measurement position stays fixed.

I'm in the data collection and analysis mode on your questions and references for today... :W

Keep in mind, as you define the right development protocols, you will learn how to research and answer your own questions....


Alles in Ordnung!

(that simple phrase above is a stark example of why Google Translate works rather poorly, as it doesn't capture nuance of cultural meaning, and mistranslates this by simplifying for an American perspective...)

[tubepit]

Hello Jon,
thanks for your reply. right what you're telling about changing an existing design. makes it change to a new design.
i already sent a mail to aleksandar ( 'cos i want to follow his design ) who could name the important specs for the ribbon tweeter. unfortunately received no answer until today.

my son has a calibrated microphone and also an usb-soundcard so one can measure using a laptop. surely i have to become aquainted with using such a system.

also i don't have the knowledge that is necessary for a correct crossover design but going activ and the use of the behringer device would be much easier than designing a passiv crossover ?
at least this is the conclusion from my readings related to crossover design.
but i have to decide which ribbon tweeter has to be bought or which woofers will fit such a design before i can start the buiding process whereupon i can start measuring ?!
therefore i have to find out the specs that have to be fulfilled by the tweeter and woofer.
those specs surely are dependent on the mids that i've already bought ( probably too early ?! ).

how deep do the woofers have to reach ? based on the e6-string of the guitar being around 82 hz and bass guitar goes an octave deeper we end up at 41hz ( taking into account that nowadays a bass often has a deep b-string we have to reach down to 30 hz ). i even don't know if it's possible to reach that deep with such a design ( two 12"woofer inside 300mm sonictube and a boxed volume from 45 to 57 liter ) or if it is necessary ?

i also have to know how high the spl-level of four of the mids i already have will be or don't know how the spls have to be summed up ? i think two of them will be twice as lound as one and four of them will be three times louder as one ( because of our hearing behaves logarithmic if i'm right ) ? the needed spl of the woofers and the ribbon depend on that.
on the other hand the behringer device can damp them down to whatever is needed ?!

after fitting tweeters are determined a solution has to be found how to connect them to the slot ? even before that i have to decide the dimension of the slot they fire into (or out of the tubes ) and probably this is dependent on the distance the tubes have? size of the tubes will be diameter 80mm and the hight will be 135mm ( this is what aleksandar mentioned in dan's thread )
i think these are the questions have to be answered before i can order the other chassis and start building.

meanwhile let me say thanks a lot for your attending to my questions !!

what was the englich phrase that google translated with "alles in ordnung" ?

was it : all right ?

i'm not using google for translation in spite i'm using "dict.cc" that has stored a lot of idioms.
but i don't know whether this site can translate whole sentences ?

so i'm keen on your answers !

hav'a good time


pit

[JonMarsh]

Still digesting this and working when I can offline- I'm very busy at work, and weekend time has been limited

[tubepit]

Hello Jon
there's no need to hurry ! i know how time is slipping away one flinching and the weekend is already past. it's nice to know you chewing my questions and that earlier or later you'll try to give me some answers or give me insights so that i'll probably by myself be able to solve some of those questions.

am i wrong that it should be possible to ad also pictures to a post ? searching the forum help leads to nothing. okay i can post a link to pictures uploaded to a pic server. in this reply-window when i'm pushing the "ad a picture-button" a window opens that's asking for an url from where the pic has to be uploaded. isn't it possible to load up pictures from my computer ?
okay it would be pleasing probably you or maybe someone else can explain whether it's possible and if so how i have to proceed. thanks in advance.
okay as i mentioned in the beginning no need to hurry 'cos besides being greedy for speaker building i have a lot of "pressing affairs" that have to be done.
have a good time.

best greetings from franken

pit

[JonMarsh]

Well, this Christmas break is the right time for me to be spitting out some answers soon.

As to posting pictures, there are a couple of ways, depending on whether you have hosting externally (like my Photo-bucket account) or if you need to upload to the HT Guide servers. In the latter case, you need to hit the "Go Advanced" button below, then scroll downwards to manage attachments, which brings up a window where you should click on the button on the upper right saying "Add Files", and select the file by browsing to it, then upload, and use the insert inline button to create the callout for it.




I host my own graphics on a photo bucket account, and just use the "Direct" URL from photo bucket, then click on the picture icon in the middle tool bar above (that's the one just to the left of the video icon, which looks like two frames of film image, in the third icon collection from the right), paste in the copied URL from Photo-bucket (or whom ever you use for online images) and voila!





Yes, that's a box with 12 of the ZA14 in it- I'm running a bit amuck with some ideas for this inexpensive driver. (inexpensive in the USA, as far as I know, only sold here at Madisound).

[tubepit]

hello jon,
not too difficult to post pictures and thanks for your explanation. i was really searching in the faqs for an explanation but couldn't find anything about posting pictures !
okay i just wanted to say thanks 'cos at this very moment i'm about to leave and meet some friends to celebrate new year's.

all the best for the new year !!

here in germany one would say : einen guten rutsch in's 2015 !

( translated word by word : a good slide into 2015 ;- )

also to all the other members here on ht-guide : happy new year !

best regards

pit