B200 and Eminence Alpha-15A report ~

painkiller · « **Reply #80 on:** 11 May 2008, 03:05 pm »

Quote from: ttan98 on 11 May 2008, 01:45 pm

Quote from: painkiller on 11 May 2008, 01:25 pm

......Kind of like Bastani's directly coupled wideband and tweeter with series resistor?

should read tweeter with series capacitor...

Sorry. I got it messed up. Corrected it now.

Graham Maynard · « **Reply #81 on:** 12 May 2008, 09:46 am »

Hi painkiller,

The B200 already goes quite high, but it is not coherent and the HF beaming can lead to HF reproduction sounding a little dry/harsh.

I do not have shelves full of moden tweeters to try with the B200, besides, few of them would be sensitive enough. Piezos sometimes work surprisingly well at HF, though these cannot be assumed to do so equally with all amplifiers due to their capacitive nature.

My personal choice for HF augmentation with the B200 is the cheap and cheerful Eminence APT without any horn; it has sufficient efficiency above 15kHz to be useful.

With a 22 ohm damping resistor connected across the APT terminals and no more than a simple series feed capacitor it can smooth the B200 harshness and recover a liquidity of reproduction which might not even be known to be missing until the APT is disconnected. The effect is very subtle, and although the APT output is barely noticeable on its own compared to the B200, it is most worthwhile.

The series capacitor might be anything between 0.22uF and about 0.5uF according to personal preference, so I would suggest purchasing 1x 0.1uF and 2x 0.22uF per side in order see which combined value sounds 'best'.

The most important aspect when adding a tweeter is time aligning the driver dustcaps. When simple crossover circuitry is being used they must all be at the same distance from the listening position.
With the APT this means that its horn opening must be level with the front chassis edge moulding of the B200; just 1/4" back/forwards and the reproduction will not be improved, and the inaccuracy of time aligment cannot then be compensated for by adjusting component values or reversing tweeter phase.

This is why a plain surface mounted cone or dome tweeter will not help the B200, no matter how perfect or expensive that tweeter might be !

The correct position for the APT means that its pointed phase plug will protrude beyond the baffle, and there will be HF diffraction too. This is normally unwanted, but when used with the B200 it improves off-axis HF reproducion as well (if not the beaming).

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

iON · « **Reply #82 on:** 12 May 2008, 02:03 pm »

Dmason, thank you for your lengty reply!

That active TT10 + IB15 sounds like a good recipe! Btw, You know that AE speakers have a 15" specialized for dipole use as well? Cant seem to find it on the home page but I know they posted info about it in some forums.

Regarding Tone Tobby, I think they're cool to deal with, when I mailed them about shipping to Sweden I got a quick response that it shouldn't be a problem. Thats good news, since the dollar is so low I think buying stuff from over seas can be justified

. Btw, have you used the 8 och 16 ohm version of the tubby?

iON · « **Reply #83 on:** 12 May 2008, 02:14 pm »

This is the one I was referring to in the previous post:
http://web.archive.org/web/20040307231755/lambdacoustics.com/drivers/DIPOLE15.html

Some info:
http://www.aespeakers.com/phpbb2/viewtopic.php?f=3&t=892

painkiller · « **Reply #84 on:** 13 May 2008, 02:10 pm »

I'm sorry for being unclear. I was actually talking about a tweeter for the Tone Tubby driver, but I guess that's way off topic. Maybe we should move the discussion to a separate thread as there seems to be some interest for this TT AlNiCo driver.

Maxdd_nj · « **Reply #85 on:** 30 Jun 2008, 05:07 pm »

Back to B200 & Alpha-15A combo...

Has anyone compared the Jantzen c-coil toroidal to their copper foil inductors in this set up?
Jantzen advertises the c-coil inductor as "specially engineered for bass, sub-woofer..."

Dmason · « **Reply #86 on:** 30 Jun 2008, 05:54 pm »

Sorry iON, I didnt notice your post/query..

I sampled the 8 Ohm Tone Tubby 10, but I would think that the 16 Ohm version paired with a small 16 Ohm tweeter of some sort, and a tube amp with 16 ohm taps would be pretty hard to beat. Either way, they are insane sounding speakers. John Harrison invented something special in these things. Makes me wonder what the 15 inch SuperBoy bass speakers would be like, the Alnico 10 on top of that, and some little horn tweeter, or ribbon. I believe the 10 inch to be superior for a mains driver of hemp, and it reaches nice and high.

Probably something like the AE 15 would be the idea candidate; those guys know what they are doing and are synonymous with super high quality stuff.

scorpion · « **Reply #87 on:** 30 Jun 2008, 10:14 pm »

I simulated TT 10" Alnico 8 ohms on an 40 x 20 " baffle with MJK's worksheet. It was placed 34" high and 8" in from the side.
This is the result:

Pretty impressive !

/Erling

JeffB · « **Reply #88 on:** 1 Jul 2008, 12:45 am »

Hi Scorpion,

Could you generate the same graph for this driver?
http://www.shredmuzic.com/product_p/813-018.htm

scorpion · « **Reply #89 on:** 1 Jul 2008, 06:22 pm »

I would recommend everyone interested to use MJK's MathCad worksheet. The fee is only nominal and you can do with the free MathCad version.
It is real fun ! I did the Tone Tubby simulation because I thought that this was of some general interest as discussions of these Alnico units have been hot lately.

However, Jeff here is the simulation of the Warrior 10, same placement as TT above:

/Erling

scorpion · « **Reply #90 on:** 3 Jul 2008, 09:39 am »

Mistakingly put here, should be and is in the 'New insights ......' thread.

I measured the Alpha15 fullrange in my 'Volks-OB' mic at 1 m distance and 90 cm (36") above floor in my livingroom. This is the result:

Quite astonishing, nothing of the cone breakup. In fact it is quite pleasant to listen to fullrange. The fundamentals are well reproduced. So revision is called for !
I think Richard might have a very good case when complementing the B200 with the Alpha going higher. As Martin said, you should never rule anything out beforehand.

/Erling

androuski · « **Reply #91 on:** 6 Jul 2008, 08:48 pm »

Hello,
and what about dispersion in full range listening ?

This is my first post here, I'm also thinking to make an OB design, but a 15" driver won't have WAF agreement, so I need a 12" one, and a cheap one just as alpha 15. Do you think this 12" driver could perform well in OB design ? It looks like a 12" tony tube driver, not the alnico one ; here it is :

http://www.toutlehautparleur.com/fane-pro/fane-sovereign-12125-p-2371.html

Scorpion, would you mind to simulate it ?
Thanks

scorpion · « **Reply #92 on:** 7 Jul 2008, 11:06 am »

androuski,

See my answer to Jeff above. MJK's software for simulation, obviously the best there is, can be obtained for personal use for very little money. Recommended ! : http://www.quarter-wave.com/ . It shouldn't be misused as a lot of work definitely has gone into the worksheets.

A software like Xlbaffle can also be used for simus, certainly not as accurate, but available free: http://www.exdreamnet.de/download/Xlbaffle.xls .

The Alpha15 is listenable fullrange but I would not recommend its use as such, there are much better. But Richard's use of it as a complement to B200 might just hit the nail.

All the best,
/Erling

tubamark · « **Reply #93 on:** 7 Jul 2008, 07:10 pm »

Quote from: scorpion on 3 Jul 2008, 09:39 am

Mistakingly put here, should be and is in the 'New insights ......' thread.

I measured the Alpha15 fullrange in my 'Volks-OB' mic at 1 m distance and 90 cm (36") above floor in my livingroom. This is the result:

Quite astonishing, nothing of the cone breakup. In fact it is quite pleasant to listen to fullrange. . . . <snip>

Seems too good to be true! Any chance you did (or could) measure it for us at a more typical listening distance - say 2.5 meters?
As measured above, we're getting the response at ~45 deg off-axis . . . I'm curious what might appear when listening from a typical listening distance, which puts the ears only ~10-15 deg off-axis (for a vertical baffle), and nearly on-axis for a tilted baffle. Also, baffle effects are not fully developed at 1 meter.

Keeping my credit card in my wallet just a little longer

,
-- Mark

DerrO · « **Reply #94 on:** 7 Jul 2008, 07:58 pm »

Just completed my version of the Visaton B200/ Eminence Alpha.

Baffle is 20" x 40" x 1.5" with a 7 degree slope.

I appreciate that the baffle my be a little less wide than some are using, but in order to have it domestically acceptable, I went with as wide as I could to have it fit the room and be domestically acceptable. So far it has only been running for a day, and have tried 1,2,3 mH on the Alpha, but at this time it actually sounds better with no inductor and run fullrange. There is however some ever so slight "honkiness" and I suspect that this is due to the Alpha being run too high.... so lots more to do, but will wait until they have been run in a bit more.

.

.

.The overall sound and tonal balance is super, however, but there is a distinct lack of bass in my 12' x 17' room and I have listened with both SS and tube and it is only with some bass boost, courtesy of tone controls(yikes!) .....then I can get it very well balanced with the bass boost. I guess that this is to be expected, though it is not quite the impression that I have got from reading through these threads.... must read them all again however! I dont think that the baffle being just a few inches wider would make much difference in the bass in real terms.... unless someone can tell me otherwise

In retrospect, I was thinking of using two Alphas per channel and decided that one would enough - seems that my gut instinct would probably have been a better route to take.... hey, but at least I am half way there now.

Any comments good or bad would be appreciated

Derro

MJK · « **Reply #95 on:** 7 Jul 2008, 08:27 pm »

Hi DerrO,

Beautiful looking baffles, really an eye catcher in the room. I think the width is just fine.

I think you might have given up a little bit of bass by mounting the Alpha 15A that high on the baffle. The bass driver should be mounted as close to the bottom of the baffle as possible to maximize any help from the floor refection. That may or may not have made enough of a difference, the B200 may be just a little too efficient to get away with only one Alpha 15A if you are using a passive crossover.

Martin

DerrO · « **Reply #96 on:** 7 Jul 2008, 09:11 pm »

Hello MJK,

Thanks very much for the input and you have just confirmed the two things that I feel i did wrong - namely, too high a position of the Alpha and also using just one with passive as you say. It is the comment that I didnt want to hear - but the truth always hurts!

Actually, when I first tried the Alphas when I got them, I did just put them on the floor and was quite amazed with the bass and I feel that I have less bass now with them in baffles than when I initially tried them on the floor - with NO baffle at all!!!!!!! - go figure!!

SO I guess that it is now l need to try again doing what you said. Oh well, at least the Alphas are cheap..... the time end effort making another pair of baffles, is not! Still, it will keep me off the streets!!!!

Thanks..... but ... in the immortal words - "I'LL be back!"

DerrO

jkelly · « **Reply #97 on:** 7 Jul 2008, 09:50 pm »

I am using the 4.7 mh coils:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=255-648

and doubled up Walmart white extension cord cables!

Jeff

scorpion · « **Reply #98 on:** 7 Jul 2008, 10:18 pm »

DerrO,

Beautiful baffles ! I think that 6" wings might do the trick. Just try with two cardboard sides at the back and see what happens. Then we have the rising B200 response and the perceived bass-loss is presumably a function of this phenomenon also. My first try with the wings in place would be to let the B200 run fullrange and put 3 mH in series with the Alpha and 10 uF across it or just a 1.6 mH inductor in series and see how that is liked. It is probably not optimal but a good start.

/Erling

DerrO · « **Reply #99 on:** 7 Jul 2008, 10:54 pm »

Hi Sccorpion,

Thanks for the kind comments. Yes, I will try side wings - though that is something I did want to avoid - but worth a try. I have no objection about using two Alphas, or spending the money on them but I just dont fancy doing the woodwork all over again! I have the inductor and cap you suggest and will also give that a try.... still dosnt tackle the rising response of the B200 though does it?!?!?! Any suggestions on that?

Thanks for your input.

Derro