[scorpion]

I promised Richard to try to compare B200 to my new MJAO G 098 speaker. I brought up the B200 baffles from the cellar and started a job which in the end resulted in the B200 sounding better at my place than ever before.

This is what I worked with:



B200s on my old baffle and Eminence Alphas on the MJAO baffle. Let me also present frequency measurement of both speakers. First the B200 fullrange (2.5 m distance on axis):



then Eminence Alpha15 fullrange (same mic placement):



I arranged so I listened to the speakers in mono switching with the balance control of my NAD preamp both speakers connected to the NAD 216 power amp.

Although this comparison has been going on at intervals the last three days I'll keep the story short.

1st: B200 fullrange alone vs MJAO, no match. B200 thin, a bit darker and at the same time sounding the annoying peak at about 3 kHz.

2nd: B200 + one Alpha15, same result and one Alpha don't really match the sensitivity of B200. So we will need 2 Alphas.

Now I tried combinations of how to passively integrate two Alphas with the B200 as simple as possible to actually mimic Richard's setup and at the same time having a measurable result that showed correlation to what was heard.

I finally reached a setup with the Alphas LP via a 4.7 mH coil and the B200s treated with a notch filter consisting of a 0.14 mH coil and a 16 uF capacitor in parallel connected to B200 like this:



which resulted in this freaquency measurement of the combination:



OK, I thought, I am home. Rulerstraight response and the bothering peak diminished and above all moved out of the fundamental tone range.

So to the listening: Again no match. The MJAO ruled supreme. The Alpha/B200 combination sounded dark and 'flat' in comparison. Is the MJAO really this good ?
I arranged also the once famous BSC-circuit, 1mH coil and 10 ohm resistor, instead of the notch filter but the result was the same and I really was worried about what I was to write about all this when I went to bed last night.

This was really nagging me when I got the idea to test active instead of passive notching. So I brought out my 31-band 1/3 octave old analogical equalizer, put it in the component chain (haven't used it for years) set the 3.15 kHz fader to the bottom. No other correction was done, just mimicing the notchfilter with the equalizer taking down the 3.15 kHz band 12 dB. I measured Alpha15/B200 response again:



That still looked very good but what was the sound like. Totally different. The passive correction components had literally 'killed' the B200. Now active it was showing its full potential and the MJAO really had a challenging opponent.

The tonal character of these two speakers are so similar that one must be astonished. You usually could hear a clear difference between speakers even if it is a small one. But here it was really difficult. Perhaphs is this dependent on the Alphas influencing their sound in a similar manner with both. And the sound is very neutral, balanced and tonally pleasing. I venture to say this even though I might be biased.

It is hard to listen for differences in mono when speakers are sounding so alike as is the case here. I would say the the B200 is just a little bit darker than the MS-100CHQ if looking on the midrange and than perhaps could be said to reproduce the register fuller. But the MS-100CHQ then counters by a little bit better definition giving voices and instruments a 'better' body. However nuances discovered in mono listening were very very small and I could not decide definitely on which I liked best. I could easily live with both combinations and stay happy.

But there is a winner and it is the MJAO because of its stereo performance. It will build a 3-dimensional stage that B200 will not really match.
This comes from an ability to reproduce ambience in a way I don't think I have heard before. Some records border to earphone quality. The B200 is certainly not bad as a stereo performer, it just that the MS-100CHQ has special qualities in this respect. It may come from the small edge in detail, definition and separation.
But as I said, I am biased.

Moral: B200 owners may perhaps be able to get more out of their speakers as shown here, both by bass complement (the Alphas is a very good way to go) and by some active tuning that should straighten out the response that bit which will do all the difference.

/Erling

[opnly bafld]

Thanks for sharing Erling!

I have a feeling if higher order x-os were necessary on your 3 ways your preference would have swung back to the wideranger.

Lin

[ttan98]

Hi,

I like to suggest if you want to experiment is use you B200 and a tweeter, the rational is that I believe the mid range of B200 is very good and use your current tweeter or better still a high quality tweeter, perhaps ribbon to complement it. Also B200 would have better power response than the small mid-range you are using.

Just a suggestion you may like to consider.

Cheers.

[Rudolf]

Erling,

thank you for a very interesting comparison indeed. I need to step back a bit to come to my question, so please excuse:

Bernd Timmermanns (BT), the mastermind behind the German DIY loudspeaker magazine HobbyHifi, is famous for designing all his loudspeakers for ruler flat response on axis and (as wide as possible) at 30° off axis. For BT “ruler flat” will mean inside a 3 dB corridor for 0.1-10 kHz measured under unechoic conditions.
Every second year BT is demonstrating his latest designs at a national loudspeaker DIY show (Gelsenkirchen). More than a few visitors to those shows have commented how equal all his designs were WRT tonality when played side by side in the same room – even if there was a 10x price difference between them. There would be clear and even large differences in resolution, imaging, distortion etc., but tonality would be almost the same.

Now coming to my original question:
Do you feel that this would apply to your comparison too – that the tonality of both systems would be equal if really equalized to the same frequency response? Or did you feel that equalizing with that active electronic device had another “quality” than EQ with a passive notch filter?

[Victor]

"Moral: B200 owners may perhaps be able to get more out of their speakers as shown here, both by bass complement (the Alphas is a very good way to go) and by some active tuning that should straighten out the response that bit which will do all the difference.


Currently I am working on a new project with 2 Alpha 15's, a B200 and a Philips RSQ 8P Tweeter. Initial results are  impressive. The B200 is a very good speaker with a fantastic dynamic and open midrange but needs to be equalised active for best results. The tweeter added is the cream of the cake.
The setup is fully active at this moment, using a DCX 2496, but I am working on a passive crossover.
I will keep you updated

[panomaniac]

Nice work Erling!  Thanks for the post and all the details.

You have found out that a passive notch filter is hard to do.   They take a lot of tweaking to get right.  Active is often so much easier, at least for most of us.

Thanks again for the adventure in Open Baffle.   If you ever get a chance to try the B200 rig with a tweeter, I, like many others, would love to know what you find.

Cheers!

[-Richard-]

Hi Erling ~

Thank you for a very impressive, highly disciplined, sensitive and thorough comparison, alternating between the B200's performance using the 2-Alpha bass augmentation arrangement, and your MJAO baffle using the MS-100CHQ.

I thought it especially interesting that you applied a very creative approach to using EQ... alternating between using a passive filter approach, and then switching to an active EQ approach with the B200's... an in-depth exploration indeed!!!

Deborah's 4 year-old Apple tower computer suddenly failed to acknowledge any "outside" media... external hard-drives and even the internal CD ROM disk player. The expense of repairing it made the purchased of a new 15" AppleBook Pro a more attractive solution... a clever intelligently-designed light-weight substitute for the huge, heavy tower model that is frightfully heavy to carry.

I also purchased 2 Airport Express transformers with it... so I could send an internet radio signal to my OB setup. It works like a dream. But my reason for mentioning this is that Apple has a built-in Equalizer as part of its itunes software.

It is great fun... and quite educational... I can play with the equalizer and hear how augmenting different frequency gamuts affects the particular music we are listening to. It actually allows me to work with the B200's as a kind of very simple EQ device. Along with supporting the particular instrumental combinations of whatever music we are listening to, I can also compensate for rises or peaks in the performance of the B200's. Not the last word in EQ resolution, this simple Equalizer does give me a chance to hear what an active EQ could bring to the B200's potential performance.

I am certain, Erling, that your description of your new MJAO baffle as being able to "...build a 3-dimensional stage that B200 will not really match. This comes from an ability to reproduce ambience in a way I don't think I have heard before. Some records border to earphone quality," will undoubtedly inspire many AC Open Baffle enthusiasts to try your wonderfully intriguing design. After all... that is precisely what we hunger for in our Open Baffle experience!!!! That 3-dimensional "alive" "in the room" experience that brings music to life and energizes it.

I think the use of a tweeter that has good synergy with the Alpha, B200 combination, might help to bring out at least some of that uncanny "resolution" you are experiencing with the MJAO baffle.

It seems the B200's do not like too much passive filtering... as I recall that was the consensus of much of the experimentation in the early days of our work with it. It seems to kill its performance which your present work confirms.

So please accept my deepest thanks, Erling, for your kindness, thoughtfullness and help in doing the hard work of comparison and careful listening that led directly to your current fascinating insights... we all at AC deeply appreciate your excellent work!!!!!!

With Warmest Regards ~ Richard

[AK]

scorpion, no wonder that your MJAO sounds better than B200
In my experience paper driver with diameter 6in and bigger should not be used above ~800-1khz
no matter what kind of cone treatment you do, they just don't sound good above that frequency.
have you thought about trying to make your MJAO's four way, using your simple crossover approach, which I like.
I'd try these approximate points
alphas Fo-200hz
visaton 200-600hz (looks like enough space for it on baffle)
and above 600hz monacor mid and tweeter.

[scorpion]

B200 and tweeter should be tested some time, would be interesting. 4 way passive I think would be difficult with this simple crossover. The reason will be the Alphas which are quite insensitive to crossover frequency if crossed only at 6 dB/octave. They will influence sound quite a bit up in the register. 4 way active with steep cut would be another story.

Richard,
I think my findings are in line with yours when asking the question and comparing an 8" and a 4". The Eminence and B200 is quite a formidable combo by any means. The Alphas give a wonderful complement actually enhancing the sound. At first when you reported your findings I was sceptical, but you were right. With the active filter in place I actually liked the B200 running fullrange best. I tried to highpass it with capacitor values ranging from 70 uF to 150 uF but that also took away character from the sound. so both speakers contribute a lot to what we actually hear.

Rudolf,

I went through another round with the B200s to compare the different settings I arrived at. I rank them like this.

1. Active notch - 12 dB at 3.15 kHz 1/3rd oct passband, Q about 4.
2. Simple BSC - LR filter, 1mH - 10 ohm.
3. Passive notch-filter 0.14 mH - 16 uF or B200 just fullrange.

No filter altered the SPL level in comparison among them. The filters were compared in mono to a combination where Alphas were LP with 4.7 mH and B200 running fullrange. I used Leonard Cohen's 'I'm your man' for the evaluation to get a reference which mainly would stay well below the affected frequencies.

Every filter did alter the sonic character more or less. The active filter the least and the BSC-filter a little more. I would choose the active notch as the best for myself.  The third rankings are the worst. I wouldn't go with any of them.

Let me state that I don't really like B200 fullrange on its own. It is overly bright in the sensitive 2-4 kHz region and at times almost cracking/blaring and this goes also for the Alpha - B200 set unequalized for what I hear.

I would consider my passive notch quite mild given the coil value. It shouldn't dig so deep or broad, yet it altered sound character the most. The sound went
much darker and lost dynamics. I wish I had documented my steps a little more scientifically then I would have been able to give a more precise answer to your question. But my gut feeling is that the passive notchfilter affects the B200 more than it should, would it just be altering the responsecurve. I used high quality components for the filter, copper foil inductor and MKP quality capacitors so they in themselves should not really influence the result.

This really interesting question is worth more investigation. But it should be done by someone with very good resources.

BT is certainly the World Champ of Notch Filters but on the German scene also Klang & Ton nowadays seem to apply them to any small response hump.

/Erling

[markC]

Very cool that you took the time for these experiments Erling.
I personally use the b200 with a BSC of .68 mH and 6.8R. Then a zobel consisting of 13uf and 6.2R. It does take some "life" out of the driver, but oh so smooth... I also cross it over to a Visiton tweet @ 2Khz. I only want up to the mid range from the B200, 'cause that's what sounds sweet to me. I futzed with the top end of it for over 6 mos. and couldn't be satisfied  with it so added the tweet.
I bring in the bottom end with a pair of infinite baffle 15" subs. These are driven with a 350W plate amp.

[scorpion]

Mark,

Yes I remember the good old times when we 'spiced' the BSC. I should test the B200 - tweeter combo obviously. 

Regarding the passive notch filter I should perhaps make a comment since Pano brings up a very good point.

A notch filter is not very hard to calculate but very hard to get right doing exactly what you want it to do.

Calculations follows this formula:  freq = 1/(2*pi*sqr(C*L)) which after some manipulation could be written freq = 5033/sqr(C*L) where C is measured in uF and L in mH. Here you will find appropiate C and L combinations to apply. Now the higher the L value the bigger notch effect both in magnitude and bandwidth. The bandwidth and magnitude can be adjusted by inserting a resistor in parallel to the coil and capacitor. In reality you will not know which L and C combination to choose so a trial and error process will decide what combination of C and L (and possibly R) values which are the best. You really need to be able to measure response during this process.

For my experiment I started with 1 mH coil value and 2.2 uF capacitor and worked down the scale eventually arriving at 0.14 mH and 16 uF when I was pleased with the measured frequency response. The notch doing its job.

/Erling

[Vix]

Mark,

Could you please provide some more details about the crossover between Visaton B200 and the tweeter?
Which tweet did you use? Also, is B200 run fullrange or is it hi-passed with a cap?

Sorry for too many questions at once..

Thanks,

Vix

[markC]

I'm using the Visaton G25FFL. x-over is 3rd order with l-pad to knock down the tweet and a bsc/notch filter to tame a bit of a peak. I run the B200's full range up to the x-over. My room isn't too large, (12 x 21 x 7.5), and I don't listen too loud, (usually 85dbish). If room was larger and higher listening levels were required, I'd high-pass the B200 as it could'nt handle the power in the bottom end.
I could dig up my schematic and post it if you like.

Mark

[Vix]

I could dig up my schematic and post it if you like.

Mark

Hi Mark,

I'd appreciate it if you could post a schematic. Basically, I'm trying to keep an open mind when it comes to open baffle speakers, and try all sorts of combination, although some of them "shouldn't work  ". At the moment I am running a single Beta 15 with Graham's T-bass, low passed at around 150 Hz, 6db/oct, and B200, hi-passed via 60 uF cap, and a notch consisting of 0.68 mH inductor bypassed by around 6 ohm resistor, and a zobel 8uF+5.6 ohm resistor. B200 has a dustcap removed and a "homebrew" phase plug (wine bottle cork cap).
Even though I am a fullrange fan, I am not so sure if I like the sound of any 8" fullrange speaker. B200 is a love-hate relationship, there are some things this speaker does very well, but the "rest" that it doesn't do that well, become very irritating.

And so I thought, why not try to squeeze the best out  of that speaker, and use it in a conventional two-way arrangement with the tweeter. This may be a fullrange heresy, but if it works...

Thanks,

Vix

[markC]

Here's a pic to tide you over until I find the schematic.