After reading through numerous pages of the thread about box colouration, it got me to thinking that perhaps OB is not a half-finished speaker after all.
To be perfectly honest I really don't know the first thing about them, and I would like to experiment with them before I go to the trouble of building BR boxes.
The speaker I have are ScanSpeak 12MU-4371T00 (4 of) and 12MU-8731T00 (6 of) midrange, and some RAAL 140-15D AM tweeters.
I read in the other thread that a low Qts is not a good thing for OB and being that both the 4 and 8 ohm speakers are low (.24 & .29 respectively) I was wonder if they could still be used.
To be perfectly honest I really don't know the first thing about them, and I would like to experiment with them before I go to the trouble of building BR boxes.
The speaker I have are ScanSpeak 12MU-4371T00 (4 of) and 12MU-8731T00 (6 of) midrange, and some RAAL 140-15D AM tweeters.
I read in the other thread that a low Qts is not a good thing for OB and being that both the 4 and 8 ohm speakers are low (.24 & .29 respectively) I was wonder if they could still be used.
I used to dismiss OB's as novelties.... until I tried it out myself, and since then I've never looked back. 🙂
Your 12MU's are usable as midranges, from 500 to 1500/2000 Hz is my recommendation.
You will need some serious woofers in addition, lets say at least a 15".
I also recommend using a dipole tweeter. Your RAAL is not.
And before you begin: get some more amps and a decent digital active crossover. OB's are not trivial when it comes to crossover and EQ, and going active you can do things that are impossible with a passive filter.
Your 12MU's are usable as midranges, from 500 to 1500/2000 Hz is my recommendation.
You will need some serious woofers in addition, lets say at least a 15".
I also recommend using a dipole tweeter. Your RAAL is not.
And before you begin: get some more amps and a decent digital active crossover. OB's are not trivial when it comes to crossover and EQ, and going active you can do things that are impossible with a passive filter.
Already have a Ground Sound DCN28 so well and truely sorted on the digital X-Over front, amp I have semi covered with more to come.
Will the monopole tweeter work or is it a deal breaker?
Will the monopole tweeter work or is it a deal breaker?
Good, you have the right tools there.
Monopole tweeter will work (you will get sound...), but the speaker will be half dipole and half monopole, with different polar patterns on each side of the XO frequency. In my opinion not the best solution.
Good dipole tweeters are few. The only ones are either planars (B&G Neo3) or AMT's (Mundorf, Beyma, and a few more). RAAL do have a dipole ribbon tweeter if I'm not mistaking.
You should also read Rudolf's paper on dipoles. Too bad its only in German, but use Google Translate to help you. It was an eye-opener for me, especially the part on Constant Directivity (Dipole mit konstanter Richtwirkung).
Offene Schallwand (OB)
Go to Downloads
Monopole tweeter will work (you will get sound...), but the speaker will be half dipole and half monopole, with different polar patterns on each side of the XO frequency. In my opinion not the best solution.
Good dipole tweeters are few. The only ones are either planars (B&G Neo3) or AMT's (Mundorf, Beyma, and a few more). RAAL do have a dipole ribbon tweeter if I'm not mistaking.
You should also read Rudolf's paper on dipoles. Too bad its only in German, but use Google Translate to help you. It was an eye-opener for me, especially the part on Constant Directivity (Dipole mit konstanter Richtwirkung).
Offene Schallwand (OB)
Go to Downloads
Thanks I will look at that when I'm not half asleep (5am here and been up all night) ok so it look like it might be worth giving it a go.
One thing the RAAL is 95dB and the 12MU8731 is 87.2dB I was planning on running them in parrallel making it a 4 ohm load.
The 4ohm speaker has a sensitivity of 90dB I was figuring running two in parallel should give me ~96dB?
Being that the dipole drives both sides what would that work out to?
One thing the RAAL is 95dB and the 12MU8731 is 87.2dB I was planning on running them in parrallel making it a 4 ohm load.
The 4ohm speaker has a sensitivity of 90dB I was figuring running two in parallel should give me ~96dB?
Being that the dipole drives both sides what would that work out to?
silent,
for OB you will need big woofers, either 15" pro woofer, or 10-12" subwoofer with lots of xmax, as u will need them when EQ or do the Linkwitz transform.
cheers
henry
for OB you will need big woofers, either 15" pro woofer, or 10-12" subwoofer with lots of xmax, as u will need them when EQ or do the Linkwitz transform.
cheers
henry
Thanks Henry from what I am seeing the basic design kills the bass to a certain degree, it seem logical it might need some reinforcing. I have a few different long throw drivers kicking around.
Can anyone advise if I still need the two mid drivers to lift to the same SPL of the tweeter?
I have both 4ohm and 8ohm drivers available.
Can anyone advise if I still need the two mid drivers to lift to the same SPL of the tweeter?
I have both 4ohm and 8ohm drivers available.
Since you have active XO, that really does not matter. Simply adjust the levels in your XO.
well silent, the good thing about OB, you dont need to spend much $$$ for experimental baffles.
you can always try to parallel the 8ohm and do MTM, see if you like it. generally it will increase SPL and lower distortion, but it maybe abit too far for the CTC on RAAL 140 as it may be less desirable dispersion.
as you are doing multich, i dont see any reason not to try few arrangements, and see what the tradeoffs are.
ive used 2x15 (eminence beta & alpha15 mix) + Beyma 12cx coax. they are good for movies and music, it may not have the refined response like hifi drivers, but they are truly dynamic.
i will use raal 70-10 for MTM, but havent found the CNC guy yet, as i got no tools here.
the succesful OB design reference is the ORION, u can see that SL didnt use high Q woofer, as he eq'ed it with his Linkwitz Transform. he loads the woofer in H-frame, and the latest one with stacked upwards H-frame style, which i think to lower the distortion due to the cancellation.
cheers
henry
you can always try to parallel the 8ohm and do MTM, see if you like it. generally it will increase SPL and lower distortion, but it maybe abit too far for the CTC on RAAL 140 as it may be less desirable dispersion.
as you are doing multich, i dont see any reason not to try few arrangements, and see what the tradeoffs are.
ive used 2x15 (eminence beta & alpha15 mix) + Beyma 12cx coax. they are good for movies and music, it may not have the refined response like hifi drivers, but they are truly dynamic.
i will use raal 70-10 for MTM, but havent found the CNC guy yet, as i got no tools here.
the succesful OB design reference is the ORION, u can see that SL didnt use high Q woofer, as he eq'ed it with his Linkwitz Transform. he loads the woofer in H-frame, and the latest one with stacked upwards H-frame style, which i think to lower the distortion due to the cancellation.
cheers
henry
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i agree with stigerik, although there will be alot of attenuation for the tweeters.
btw, stigerik got one of the best OB (prob the best) on the forum 😀
cheers
henry
btw, stigerik got one of the best OB (prob the best) on the forum 😀
cheers
henry
I already have quite a few of the midrange 6 * 8ohm for 3 front speakers and 4 * 4 ohm for the rear four channels, so it isn't going to hurt to try it as an MTM first, as you say the baffle is hardly going to be a piece of art compared to what I have already been experimenting with.
For bass I am considering Focal Axiom 13 WX
For bass I am considering Focal Axiom 13 WX
I experimented a lot with OB's, think I build more than 20 different speakers. It was a lot of fun by the way... 🙂
I didnt like MTM, found it sounded and measured better with the two mids close to each other, and run in push-pull, like this. And no baffle...
Tweeter is a Mundorf AMT2340 without front plate.
I didnt like MTM, found it sounded and measured better with the two mids close to each other, and run in push-pull, like this. And no baffle...
An externally hosted image should be here but it was not working when we last tested it.
Tweeter is a Mundorf AMT2340 without front plate.
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ok, if you are doing multich, please keep in mind the OB needs at least 60cm from the backwall and sidewalls. they need room to breathe.
long time ago peter daniel use focal woofer with faraday ring, i think it was audiom in his U-frame OB.
where will you buy those focal axiom?
cheers
henry
long time ago peter daniel use focal woofer with faraday ring, i think it was audiom in his U-frame OB.
where will you buy those focal axiom?
cheers
henry
as you can see, stigerik been thru alot of versions of his ultimate OB 😀
prob ORIONs is the middle ground between ultimate sound and WAF 🙂
cheers
henry
prob ORIONs is the middle ground between ultimate sound and WAF 🙂
cheers
henry
Yeah, I build a lot of OB's using 5" and 8" Excel drivers, and Mundorf and Beyma AMT's. And in the end I ditched the whole concept, and went for a B&G RD-75 ribbon instead ....
Don't have to worry about WAF too much as I probably have the most understanding women on the planet. As long as I'm happy she will pretty much go along with it.
StigErik the SS illuminator are dead sexy from the back so push pull might be quite ok if done that way. Any particular reason for that arrangement, or is it purely just the measurement?
StigErik the SS illuminator are dead sexy from the back so push pull might be quite ok if done that way. Any particular reason for that arrangement, or is it purely just the measurement?
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There is one good reason for doing push pull with both woofers and midranges, and that is distortion reduction. Odd order harmonics are reduced with a factor up to 10 because of phase cancellation of the distortion products between the drivers.
By accident I had made the basic English version unaccessible for the last weeks. It is now available again. 🙂
The German version is extended - including more measurements. But if someone reads the English first, he will have no trouble "upgrading" to the German extensions.
Rudolf
hi rudolf,
would you please provide us the link to your english version?
very much appreciated for your work.
cheers
henry
would you please provide us the link to your english version?
very much appreciated for your work.
cheers
henry
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