[Graham Maynard]

Hi Mark,

It is so easy to study the amplitude response of X or Y filter, but seeing on a page or screen cannot correlate with what is heard.
I cannot explain more than stated, and my time must be shared.

As you say - it is not possible to avoid phase or time issues, so we must be careful they do not become distracting.

For example I feel that fullrange drivers ought not be electrically compensated (BSC) for a phenomenon not caused by themselves (baffle size/shape), and that a second or more drivers should be used on the same baffle (or in the same cabinet) to compensate for radiation changes with frequency which are caused by that baffle (or cabinet).

Any 'crossover' on that second driver would not directly change the main driver response, though we must then ensure that its augmentation does not cause unnecessary interference or become separately identifiable due to audible crossover circuit component induced 'Q' effects which act within their own independent time frames.  Low slope = low 'Q', which you mention.

Of course the second driver does introduces phase change too, but it can be filtered/directed so as to not interfere with the recognisable direct path of the full/wide range radiation we initially 'hear'.

I am so far using only 6dB slopes on drivers which don't respond badly (eg raised breakup SPL) beyond the ranges used here, and I am using the step-up transformer, inductor and capacitor to change (boost and cut) with minimum phase change around driver Fs before using a single series choke, whereas other conventional crossover arrangements use 12dB/oct or more ahead of the LF driver, which leads to increased electrical phase/timing problems where low/main driver SPLs must be arranged to cross over.  That increased phase difference then leads to a lack of natural sounding 'blend' of LF with main driver output.

Hi Mr C.

Offset on a large or non-symmetrical baffle like yours the B200 can be surprisingly good with lovely tonality, but only as long as its input is not too heavily bass modulated.
Hence the size of this project - which was not initially intended - but is worthwhile.
The B200 also goes high in frequency, like a tweeter, though here I am attempting to further improve coherence and reduce hf beaming.

Cheers ........ Graham.

[Mr Content]

Hi Graham, I would like to hear your opinions of your multi driver baffle. I went muti driver with baffles 1 thru 8, but liked the coherency of the B200 ny its'self, so baffles 8 thru 12 were designed around the single driver layout.  I then designed subs to meet the b200 around 160hz, using Vifa 10 woofers in a pushpull isobarick configeration. The subs sit 800mm behind the baffles and intergrate seemlessly. Anyway I like to watch other peoples journy with the B200, I find it a very good wideband driver. I will re read your mods to the driver, but I have not seen the need to add a tweeter to my baffles yet. Good work though, and keep going.

Mr C

[fergs1]

Hey Nigel, good to see you around.I hope all is well with you and your lovely family. Give us a bell and let me know haw you are
                                  peace and goodwill     chris a.k.a fergs

[Graham Maynard]

Hi Mr C,

Good that you are 'content'.  Not yet there myself though.

The single B200/woofer could not do it for me though because I like to have plenty of linearity reserve.  I note you are using your's above the range where it can distort harmonically

I'm sure your sub is loud, low and clean. I already have a sealed enclosure 15" Rockford trouser flapper for 50Hz and down, but then it gets heard several doors away, which is not arising with dipole radiation.  Still don't think I am flat as low as Bruno's Ripole, though my sound is well integrated.

So I'm seeing what the T-bass circuit can achieve without me having to use additional amplifiers.

Slow but sure ....... Graham.

[Mr Content]

Hi Chris, yep still around the traps, we will have to catch up

Mr C

[Mr Content]

Hi Mr C,

Good that you are 'content'.  Not yet there myself though.

The single B200/woofer could not do it for me though because I like to have plenty of linearity reserve.  I note you are using your's above the range where it can distort harmonically

I'm sure your sub is loud, low and clean. I already have a sealed enclosure 15" Rockford trouser flapper for 50Hz and down, but then it gets heard several doors away, which is not arising with dipole radiation.  Still don't think I am flat as low as Bruno's Ripole, though my sound is well integrated.

So I'm seeing what the T-bass circuit can achieve without me having to use additional amplifiers.

Slow but sure ....... Graham.

Yea, slow but is the way to go for sure. I made sure i was happy with each improvment before I moved on to the next. Have you thought of magnet mounting the b200. improves clearity heaps.


Mr C

[Graham Maynard]

Magnet mounting suggestion is noted.
I've already observed baffle vibration and baffle 'sound' so more to do there too.  (Help !)

I did try a 100uH choke in series with the B200 and the very direct SS amplifier connection - slightly too much inductance. 
60uH was much better at taking out very high end 'tsz', probably like the output inductance of a high quality tube amplifier.

So what causes this 'tsz' ? 
Amplifier interaction, or the magnet-voice coil circuit ?
Some cable companies claim to cure it.
Some refuse to use SS.
Sebastien the PHY manufacturer compares it to an electromagnetic phenomenon.
Bud, the originator of EnABL techniques, recommends a LS connected electron pool, whilst some connect a driver chassis to the LS feeder ground.

I've still much to learn, and so much to check out !

Cheers ........ Graham.

[Mr Content]

Hi Graham, baffle vibration is not good. As you have probably already noticed, it smears the image, caused by energy coming off the baffle at the wrong time. I use 40mm baffle laminated with 3 different material, with a steel frame behind. I have come to the conclusion that the baffle must be as inert as you can make it. The Tsz you are hearing if a function of a few things. But cables will help as will tubes. I have NOT had problems with any Tsz, and believe that correct mounting in a good baffle my also help this. I have also tried and dismissed any circiut on the driver, hearing more bad than good from these. Grounding the driver is a good idea, and I do that to mine.
Good on you for having a go, and giving it a chance, some have dismissed this driver without enough effort, and lost a chance to hear something special.


Mr C

[panomaniac]

Hey!
A couple of questions for mr. c

You say above that you bring the sub in to meet the B200 at 160Hz.
How big a baffle do you use to get the B200 down that low?

Magnet mount - how are you doing it?  I understand the idea, but...
Just how decoupled is the driver from the baffle?  Is it just touching - are there leaks? (do they matter?)

Thanks!

[Mr Content]

Panomaniac Here is how I did my mounting The driver intersects the baffle with a 6mm rubber gasket. I will post some measurment of the baffle later. Bear in mind the baffle has been tweaked thru a series of 12 main baffles and lots and lots of test baffles.

Mr C

[Graham Maynard]

Hi Mr C.

NEAT !........ Graham.

[panomaniac]

Neat indeed!   Nice work, too.

I'll have some questions later, after work.

[Graham Maynard]

Hi Mr C,

Looks like you are also taming the B200's high frequency response by using a 'filter' - the grille cloth.

Cheers ......... Graham.

[Mr Content]

Hi Mr C,

Looks like you are also taming the B200's high frequency response by using a 'filter' - the grille cloth.

Cheers ......... Graham.

Hi Graham, yes the grill cloth does tend to knock the top off the high's, but for serious listening  It removes easily. What amp and cables are you useing.


Mr C

[Mr Content]

Hi Graham, I have just read the thread again, and I can see your design approach. I have never tried the passive route, going bi, and tri amped, and doing a lot of filtering in the digital domain. Sorry if I seem to have taken over your thread, I was just excited by your enthusiam. Hope the info on the magnet mount is usefull, and I will let you get back on topic. Sorry


Mr C

[Graham Maynard]

Hi Mr C.

You are not taking over at all.  Your OB ideas and experience are most welcome.

I have not had opportunity to do more, other than let my son hear the latest with the large transformer and some slight adjustments.

Running flat with a single amplifier I did not realise how loud it can go whilst remaining clear, until I realised I could not hear him speaking to me from only 3ft away.

He now says it is very, very good, very clear, and that the bass is unbelievable for just being a free edged panel.  He no longer thinks it needs a sub, and says I should start building the other channel straight away.
Still too much to get sorted before building copies though.

I no longer have any qualms about OB bass.  Room radiation is excellent and widespread, deep and dynamic and without any enclosure related overhang, yet it does not shake other room doors further down the hallway the same way that conventional exit pressurising boxed loudspeakers always do !

I am very pleased with this.  There might be better 15"ers available, but these Beymas (£82ea at Blue Aran; Fane 10" £20 ditto) are doing a fine job.  Also, being low Q types with cloth edge means that there are no driver resonance related peaks as tones or notes slide downwards, which is exactly what I wanted.

Do I wish to try any different drivers ? 
Most definitely not.  They all work well within their chosen ranges.
Baffle shape or positioning ? 
Nothing more than slightly rounding off the top corners and sloping at the top right.

Cheers ........ Graham.

[Mr Content]

Thanks Graham, you are very gracious. When you make your next baffle, try adding a roundover on the edge, infact on my next baffle,(I have had my current ones in use for about 14 months), I will be adding a a 180 degree 65mm roundover. In part I want to make the front side of the baffle wider than the rear of the baffle. I think this will help even more with cancellation issues.

Mr C

[scorpion]

Hi Graham,

I have a dumb question: Will blacksprayed foam fingers work ? Or is it both absorption and redirection ? 

/Erling

[Graham Maynard]

Hi Mr C.

I have already thought of rounding the baffle edge - and i know from the past it literally takes an edge off the sound.

There is something else I have in mind too - more foam in the form of pipe lagging which is generally grey in colour along / over unrounded edges.
Different sizes are available and I intend to try several options using that lagging foam.

Hi Erling.

That's what Mic Jagger wanted to be done, however the foam is both absorbing and dispersing.  I fancy a coat of paint would make it into more of a hard reflector, so would not recommend that. 

However, it would be possible to have fine wires concealed and coming through the baffle into the foam to lighting blue LEDs which will beam through towards the centre from the flat sealed ends.

Cheers ........ Graham.

[scorpion]

May be Jagger whould need a transformer too, I see the point and it is as I suspected.

/Erling