MJAO G 098 - The Anagram - Crossover revision

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scorpion

MJAO G 098 - The Anagram - Crossover revision
« on: 4 Mar 2009, 06:49 pm »
From time to time there has been some discussions of the JAMO dipoldesign R 909 (now there is also a R 907 along the same line): http://www.jamo.dk/Default.aspx?ID=5966&M=Shop&PID=17139&ProductID=17649. In particularl I remember one thread here from spring 2007 where MJK and myself were contributing: http://www.audiocircle.com/index.php?topic=41297.msg368661#msg368661 . I think this was the first time that MJK was hinting at what is now his famous passive OB-design with the Eminence Alpha 15s and the Fostex FE 103 E: http://www.audiocircle.com/index.php?topic=41297.msg368661#msg368661 , which he published in September the same year: http://www.quarter-wave.com/OBs/OB_Design.pdf . I went on designing the 'Volks-OB' put forward also inte automn 2007: http://www.audiocircle.com/index.php?topic=46951.0 .

However the thought of a 3-way passive OB-design along the JAMO lines never left my head, so here I now present one. I would like to see how far one could come with a JAMO like 3-way dipole speaker although on a budget. The choice should be made from units possibly performing at a high level but not taken from the most prestigous and expensive brands.

First I would like to introduce my partner 'Grizzla' to you. She pointed me to the anagramatical subject line by voicing her 'mjao' every day when something is at issue or just for company. She has contributed also with the letter 'G' in the name. Here you see her carefully examining some of the crossover components:



The beginning was of course with simulation with MJK's Math Cad software. In this case with 2 Alpha 15s and the Monacor MS-100CHQ on a baffle with the same measures as the prototype presented below. Crossover were set with 12 dB/octave with LR characteristics at 200 Hz and 280 Hz. result was like this:



This seemed promising enough to go further with a test baffle, which looks like this:



It is an MDF baffle which measures 110/120 cm x 40 cm (44"/48" x 16"). Lowest Eminence Alpha15 is placed centered 22.5 cm (9") up from the bottom to give place for the small legs (shelf holders, two of the same at the back). The upper woofer is then placed as close as possible to the lower bass unit. Then the MS-100CHQ is placed 92.5 cms (37") up and 12.5 cm (5") in from the smallest side. Finally the tweeter is put on the baffle close to the midrange unit. The picture is of the left hand speaker , the right hand one is a mirror copy.

Units:

For bass produced by a narrow baffle I would consider the Eminenca Alpha15s as mandatory given the current market supply. They will give powerful, tight and transient true response to you. Those who describe the Alphas as sloppy and too high Qts speakers are simply wrong.

The midrange is supplied by the Monacor MS-100CHQ. My first encounter with this speaker was in a thread of German Audiodiskussion late 2005 titled (in translation) 'Fullranger bis 13 cms if you were free to choose'. Frank Kuhl of Monacor there put forward both the MS-100CHQ and the SP-130X/8 as possible alternatives. Later I bought a pair of both. The MS-100HQS were no fullrangers, so they were laying around til now. But the SP-130X/8 were put to good use in the 'Volks-OB'. For this design I however remembered the Monacor claims, so I decided to give it a try. I didn't regret. The link to Monacor is here: http://www.monacor.de/typo3/index.php?id=56&L=1&act=8&act_sub=23&artid=5258&spr=EN&typ=u . By some puzzeling thoughts these speakers are placed in the Monacor Carpower range. Given their response and build quality they should also be among the Hi-Fi units. MS-100CHQ is built in Germany by the same factory that also build the well known ETON speakers.

Among tweeters I chosed between Monacor units RBT-95 and DT-28N. RBT-95 is a magnetostat ribbon speaker ( http://www.monacor.de/typo3/index.php?id=75&L=1&act=8&act_sub=25&artid=6467&spr=EN&typ=u ) and DT-28N is an neodymium tweeter ( http://www.monacor.de/typo3/index.php?id=75&L=1&act=8&act_sub=25&artid=3573&spr=EN&typ=u ). My final desicion was in favour of the DT-28N which I thought presented the most pleasent sound. The square cut out you see in the baffle was for the RBT-95 units.

Crossover:

I had difficulties getting a balanced crossover between the bass and midrange using  a 12 dB/octave filter.I was a bit puzzeld by that. So I decided along the KISS guidelines and tested 6 dB/octave crossover slopes. I stayed with them. All bits suddenly seem to fall in place, this is the filter:



which resulted in this (in my livingroom) frequency response:



All in all you see here a +- 3.5 dB difference over all the frequency range.

Sound:

This by a margin is the best OB-speaker I have constructed  so far. It outperforms the 'Volks-OB' in direct comparison. The B200s will not touch this mid-tweeter combo in performance. I have in fact stopped listening for faults in this speaker, just enjoying it. By the way it runs Lynn Olsen's speaker teaser: Mussorgsky's Picures at an Exhibition, orchestral version, with the Minneapolis Symphony Orchestra in full colours. Diana Krall's 'Live in Paris' comes over more 'live' than I ever heard it yet portraying the band beautifully ambient and my constant meter Manger's: 'Musik wir von einem anderen Stern' sounds like never before.

/Erling
« Last Edit: 4 Nov 2009, 03:48 pm by scorpion »

Rudolf

Re: MJAO G 098 - The Anagram
« Reply #1 on: 4 Mar 2009, 07:53 pm »
Erling,

your crossover looks EXTREMELY frugal for a 3-way. Getting such a response from three drivers and three filter components is almost unbelievable. I notice that you not even need to adjust for the efficiencies of the different drivers. It´s simply amazing.  :thumb:

Rudolf :notworthy:

MJK

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Re: MJAO G 098 - The Anagram
« Reply #2 on: 4 Mar 2009, 07:56 pm »
Erling,

Very nice!

My four Alpha 15A's are sitting boxed in the basement. I have a pair of the Aurum Cantus ribbon tweeters in boxes behind the couch. I have a few Lowthers I could use for a mid range in a three way set-up also behind the couch, or I could buy a decent mid range driver. I am very tempted to start a three way OB design tonight based on your posting.

Aaaaaagggggggghhhhhhhhh, but I have something else I am working on that I promised myself I would finish this time.

I really like the idea of a three way passive OB, your design is motivating/distracting me.

Again, very nice!

Martin

freddyi

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Re: MJAO G 098 - The Anagram
« Reply #3 on: 4 Mar 2009, 07:57 pm »
hi Scorpion - - that's a terrific report, test-build and measured result (-and Grizzla is beautiful) - I don't have MJK's simulator - sometimes with 1st order highpass there can be excursion peaking but apparently didn't happen in this case -- does your Monacor MS-100CHQ move much under big orchestral (or loud drum) passages?  would larger midrange have worse result on vocals?  which software other than MJK's sheets are good for helping with passive crossover?  Best, Freddy

ttan98

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Re: MJAO G 098 - The Anagram
« Reply #4 on: 4 Mar 2009, 10:44 pm »
Congras, especially when your current speakers out-performs the previous one, that is what DIY speakers is all about.

I always prefer a mid and tweeter combo to a full-ranger. Currently I am consider trying out the Eminence 8" with a ribbon tweeter similar what G. Pimm is using, he uses a simple x-over.The combo is very cost effective. A good quality mid-ranger is very hard to beat.

Cheers.

fergs1

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Re: MJAO G 098 - The Anagram
« Reply #5 on: 4 Mar 2009, 11:15 pm »
greetings Erling, haven't been here for a goodwhile but looking at your post this morning piqued my interest. What  is the overall efficiancy of the complete speaker.I must admit I am thinking of another solution to the b200 (it always seems like one of those relationships where you argue all the time but the sex is great and finally you feel like you can forgo some of the excitment for a more relaxed union). Must look into if anyone does monacar in Oz. Erling have you heard from our friend Nigel?I wonder how he is?
    Thanks for sharing your project here, I can feel my tools in the shed getting nervous :D

                                                                   peace and goodwill  fergs

panomaniac

Re: MJAO G 098 - The Anagram
« Reply #6 on: 5 Mar 2009, 01:45 am »
What a simple rig - bravo!  The right choice of drivers goes a long way.  Looks like you chose well.  :thumb:

At first I could not understand how you could use only 2mH on the bass, especially on a narrow baffle like that.  But I did some calculating and found that the 2 Alphas in parallel should be be right at 100dB/2.83V before OB losses..  Your mid is at about 91dB/2.83V.  That 9dB difference is just about right!  Makes up for the OB losses. Guessing the bass to mid crossover is at about 400Hz.  What do you think?

Not quite sure where the tweeter comes in, but you seem to be crossing it at 4KHz.

Nice work.  Certainly a very simple, straightforward design.

Kludden

Re: MJAO G 098 - The Anagram
« Reply #7 on: 5 Mar 2009, 08:53 am »
Hi Scorpion!
At least. Now you have done it.
Looks nice. Now I have to buy 2 more Alphas to make me a new Volks-OB. :D
Regards
Kludden

Bonzite51

Re: MJAO G 098 - The Anagram
« Reply #8 on: 5 Mar 2009, 01:40 pm »
Hi, Erling,

Congratulations!
You have done this very well especially with ARTA response confirmation.
I bought some 1,0 mH inductors for Alphas, also I am playing with some attenuation for Ciare
(just some kind of "Lpad" 7-8 Ohms parallel to Ciare)
Here is some pictures:
http://www.audiocircle.com/image.php?id=18599
Unfortunately I can not insert images right in the text?!

Janis

freddyi

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Re: MJAO G 098 - The Anagram
« Reply #9 on: 5 Mar 2009, 04:39 pm »
hi Janis - is that CH250? - if so I like those - what's your crossover (if used) and attenuation pad?

scorpion

Re: MJAO G 098 - The Anagram
« Reply #10 on: 5 Mar 2009, 09:12 pm »
Thank you all for the kind words !

Some things missing in the text and also asked for.

Frequency response is for the right hand speaker in the stereoseat 2.5 m from the speaker on midrange axis.
Sensititvity is a solid 95 dB at 1 m give or take some dBs over the audiorange as reflected in the frequency measurement. I adjusted the level to be 2 volts at 2 kHz over the midrange (about 1 watt) to perform sensitivity analysis. MDF is 19 mm thick (3/4").

Crossover components I have used here is from the Danish firm FreQuence: http://www.frequence-shop.dk/ . Capacitors are from their PCA range and coils are wire wound 1.2 mm adjusted with ferrit core. I measured the coils to 1.85 mH and capacitors values are 82 uF resp 4.7 uF. Prices are quite resonable and quality high. I suppose that quality components from Parts Express like ERSE coils and Dayton caps would give good results. A ferrit core coil with 1.2 - 1.4 mm wire with low internal resistanse should more than well cope with powers actual here and stay linear. For capacitors Obbligato from Diy-HiFI Supply (http://www.diyhifisupply.com/ ) are also favorites. Bass lowpass is calculated to 300 Hz and mid HP to 500 Hz approximately, effectively it will be like Pano's 400 Hz suggestion. But the Alphas will not fall of as fast as theoretically determined. Their performance is reflected in the measurement. They start falling at 300 but from 900 to 1600 they will stay level only about 12 dB below the midrange then they fall off rapidly. So they will contribute a bit more than presumed. The tweeters start at 5000 Hz. I experimented with some different cap values and settled for 4.7 uF giving the reported response. The mid falls off a bit lower than the published response curve would suggest at least the units I have. A good on-line crossover calculator is the Aj Design Crossover calculator here: http://www.ajdesigner.com/index.htm .

Rudolf, I guess I have been lucky in unit choice. In fact the Alphas have gained more than 3 dBs during run in. At first I had to take down the mid-tweeter combo.
I exercised the Alphas at 30 and 40 Hz in the beginning but only with my little Trend T-amp and that power was obviously not enough.

Martin, I think many look forward to a passive 3-way OB design by you. I will look into putting DT-28s also on the back for a true dipole design. This one follows the JAMO approach.

fergs, I haven't hear from Nigel for a long time. He said he would look inte new baffles for the B200s. I hope he is well.

freddyi, I have to rig up my SS NAD to stress the speakers more than the Trends can do. I'll come back with an answer to you. Regarding unit size I think all will depend on chassis characteristics. Larger units will probably start beaming a bit lower than the 4" unit. These speakers produce a reasonable Stereo over my 2.5 m listening sofa, but the stereoseat is absolutely best.

I estimate component cost for a pair of these speakers to ca 500 US$, excluding European VAT rate and transportation cost. One European supplier with competive pricing that will ship world wide is BMM audio & electronics: http://www.bmm-electronics.com/intro.asp .

/Erling


Bonzite51

Re: MJAO G 098 - The Anagram
« Reply #11 on: 6 Mar 2009, 06:38 am »
hi Janis - is that CH250? - if so I like those - what's your crossover (if used) and attenuation pad?

Yes it is CH250, regarding crossover just 1,0 mH for Alpha and some attenuation for CH250.

Please let me know how you insert picture into text?

Regards,
Janis

scorpion

Re: MJAO G 098 - The Anagram
« Reply #12 on: 6 Mar 2009, 07:18 pm »
freddyi,

I owe you an answer with regard to midrange performance for the full symphony orchestra and heavy bassdrum. My Trend T-amp distorts when getting too high in SPL so I have tested with the NAD. 100-105  dB full symphony orchestra barely moves the cone. I tested with Beethoven 5th and there is no stressed sound.
Test with low kontrabass and bassdrum transients at the same SPL levels move the cone but I don't think over the 1.5 mm X-max and above all the delivery is effortless. The mid should also be able to take power according to specs. I tested with the Manger record, kontrabass with Renaud Garcia-Fons: Ghazali and drumpassages from the same record The O-zone Percussion Group: Jazz Variations. These selections spann a sound spectrum from the real low up to a bit high.
I am quite impressed, myself.

/Erling

panomaniac

Re: MJAO G 098 - The Anagram
« Reply #13 on: 6 Mar 2009, 08:12 pm »
Alphas will not fall of as fast as theoretically determined. <snip> They start falling at 300 but from 900 to 1600 they will stay level only about 12 dB below the midrange then they fall off rapidly. So they will contribute a bit more than presumed.

That makes sense given their published FR and the fact of the rising response on OB.  I've been wondering if the Alphas and the Monocors are not phase cancelling a bit thru that range.  It might explain the broad midrange dip seen in your FR plot.
That should give the speaker a pleasent, laid back sound.

-Richard-

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Re: MJAO G 098 - The Anagram
« Reply #14 on: 7 Mar 2009, 05:50 pm »
Hi Erling ~

Your design is a triumph of understanding of how to bring together drivers in perfect "passive" concert together. It looks really great as well... form following function at its best!!! The thin tailored look of your Open Baffle's helps to make your design even more appealing.

Congratulations!!!!!

I will need time to study the information you were so kind to share with all of us... but I can see myself trying a version of your excellent design sometime in the future.

Thanks so much Erling, for sharing the wonderful results of your clear penetrating thinking with us.

Warmest Regards ~ Richard


jkelly

Re: MJAO G 098 - The Anagram
« Reply #15 on: 7 Mar 2009, 10:25 pm »
I am in on this too.

I am done with the CS2 clones and will put a new plate in the top section
for the two drivers.



Jeff

-Richard-

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Re: MJAO G 098 - The Anagram
« Reply #16 on: 8 Mar 2009, 03:52 am »
Hi Erling ~

I realize that listening to music with different speaker/amps/media is a terribly personal experience... and asking anyone to explain what they think they are hearing is fraught with dangers on all sides... but I wonder if you could go into the differences, in a bit more detail, to what you are hearing with your new 3-way Open Baffle driver arrangement, compared with your "Volks-OB" that uses the B200's.

For example... after reading with excitement how successfully you have integrated the 2 Alpha 15A's (hooked-together in parallel) with what appears to be the 3,1/2" Monacor MS-100CHQ... I listened a bit more intently to my own simple single Alpha 15A hooked in parallel to a single B200 and began to wonder how a much a smaller but dedicated midrange driver like the MS-100CHQ might sound in the magical area of the midrange compared to an 8" driver... especially given its relatively low sensitivity (90db).

What aroused my curiosity was remembering that I once had a 4" boxed full-range (?) single driver speaker that I played with for a few months... I found the sound less fleshed-out then a comparable 8" full-range driver and it seemed to me that the size of the driver may have played a part in this sense of a smaller musical space. On the other hand the smaller driver was faster than the 8" driver and there was more "detail" reproduced. I also realize that ones musical appetites may also play a part in the all-over equation.

Of course that experience has nothing to do with your present OB design... I am not extrapolating here... simply very interested if you could describe the differences you hear between your 3-way OB and your previous "Volks-OB"... especially your impressions of the mid-range.

Thanks in advance for any help you could give us here, Erling. Like many other Open Baffle enthusiasts on AC that have found your new 3-way design incredibly intriguing, I am hungering for more of your personal impressions.

Warmest Regards ~ Richard

jkelly

Re: MJAO G 098 - The Anagram
« Reply #17 on: 8 Mar 2009, 02:21 pm »
Scorpion,

I am having some trouble finding the MS-100CHQ listed
on the BMM site - I am awaiting a reply from them, but
are you able to find them on the site?

EDIT - thanks - Drivers are ordered.

Jeff
« Last Edit: 15 Mar 2009, 01:27 pm by jkelly »

PB

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Re: MJAO G 098 - The Anagram
« Reply #18 on: 8 Mar 2009, 03:06 pm »
Hi,
Try this link and choose convenient country....

http://www.monacor.de/typo3/index.php?id=99&L=1&act=7&act_sub=99&logged_in=

Peter

freddyi

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Re: MJAO G 098 - The Anagram
« Reply #19 on: 8 Mar 2009, 04:10 pm »
thank you very much Scorpion