[Mijknarf]

I just thought I'd drop a line to contribute my OB project.  I've owned these about 6 months and after trialing several baffle dimensions, filters and amping, I've settled on this design. 

I'm bi-amping the units using the two RCA outs on my preamp.  The Visaton runs full range with no filter, the Eminence runs with a 9.5mH coil.  I use a 2A3 SET amp for the Visaton and a SS 150 watt amp for the Eminence.  I do use a bit of EQ in my J.River playback software.  I cut the bass about 3dB under 170Hz and boost the treble 4dB over 6kHz.  I find the integration very smooth. 

My previous speakers were a pair of Bob Brines MLTL using a Lowther DX3.  I loved them for ~3 years, but just needed more foundation to my music below the ~500Hz point to support the low end in my music, these do it nicely.  Thanks for looking.

[THWO]

.
Congratulation!
Nice front finish. Did you insert a separate ring around the woofer front? Looks very carefully made and is a good contrast.

Enjoy your new speakers,
Till

[Mijknarf]

Thanks for the comments.

The baffle is 1.5" thick Baltic birch with cherry veneer on the front.  The Eminence drivers are rear mounted.  I used a 3/4" radius bit to round over the front of the driver's opening.  You're seeing the color difference between the cherry and birch ply.

Jim

[THWO]

.
Well done.

Till

[Mr. Oczka]

Your speakers are absolutely beautiful!  Just curious,  what kind of music do you listen to with them?  I am a novice as far as speaker building goes.  I really like the look of the open baffle panels and think a set of them would look really cool in my family room.  I'm sure my wife won't agree with me, but I'll cross that bridge if and when I get there.  Anyway, the majority of the music I listen to is pop, classic rock.  Would a set of these work in that setting?  Thanks for any and all advise.  Tom

[Mijknarf]

By asking me if they'll "work" in your setting is impossible for me to answer because of room, amplification and taste in music.  I listen mostly to trio jazz, blues and chamber classical, nothing with a heavy bass line, like rock and some pop has.  While I'm getting a very substantial low end that fills the room I don't get "chest compression bass" that comes from major air movement which I think is needed with rock music.  There is a difference between 40 Hz double bass and 40Hz electric rock bass and drum kit.  Perhaps the addition of a powered sub or two may do the trick, but others would be better equipped to direct you on that front.  Strictly from my experience, I'd keep investigating.  Many thanks for your kind words.

[nickd]

Those are Sweet!

If you want to get a little more bass punch you might invest in air core inductors in-place of the Iron core. The Iron core slug tends to zap a little dynamic out of the bass IMO.

[THWO]

.
Might inserting a second woofer be an option in case there is space enough?

That´s what I did (2x Alpha 15A and Ciare CH250):



Hope I did not highjack your thread with this pic.

Till

[Mijknarf]

Till,

Rest easy, no hijacking considered.  Very nice speakers you have there.

Regarding bass output, perhaps I have mislead with previous comments.  My bass output is fine, in fact I cut my lower octaves via the EQ in J.River so it doesn't overpower.  However, the bass does not move the air in ways that a powered sub would.  The movement of the Alpha diaphragm (as you know) is quite small vs. a sub, so I don't have the chest compression impact that is required (imho) for classic rock. 

Does that make sense?

Jim

[THWO]

Well, two membranes do not need to produce "more" (in sence of louder) bass, but may be the significantly larger total surface may be "nice to have".

Other vague idea: Did you take measurements? May be a little accentuation in the 50-60 Hz area might give a bit more punch? - If you drive the woofers passively, as it looks from the pictures, it may be a bit difficult, though...

Btw, at which frequency do you cross over? Mine are crossed at 120 Hz and driven by sub amps.

Till

[Mijknarf]

Till,

I'm driving the woofers with a separate solid state stereo amplifer (150 watts).  I'm using a a simple coil on the woofers to cut them off around 250Hz (from my readings here on similar systems). 

Please tell me more about your sub amps.  I assume you're using two, one per channel?  How are you driving them?

Thanks,
Jim

[THWO]

.
You are right, I am using two Hypex DS 2.0. The woofers are connected parallely. I cut them off at max. = 120 Hz (the only little disadvantage of the Hypexes as I would have preferred a higher optional cutoff). A have a gain of an estimated 3-4 dB at about 50 Hz (on the scale; in reality at about 40 Hz, then dropoff). Probably, one modul would do as the cutoff is fairly low, but I happened to have two, so I use them. They can be driven either by cinch or by speaker cable. Quite some choice of settings. Seem ok to me.

You may find more information here (the DS 2.0 is number three in the list):
http://www.lautsprechershop.de/index_hifi_en.htm

The width of the baffle at the bottom is 41 cm (16.1 inch) and at the top 54 cm (21.4 inch). No wings on the sides, so the wooofer seem to welcome some additional support in the low frequencies.

I feel that open baffle woofers (and fullrange systems even more) don´t "honor" wings. It may support the lower fs but seems to blurr reproduction especialle in the more sensitive full range band.


Till

Edit:  Sorry, when checking out the link I saw that it doesn´t lead directly to the moduls. Please go down to "amplifiers" (just below the third photo) and then hit "active moduls"....

[THWO]

.
During progress of my OB-project, the Ciare CH 250 have changed quite a bit, the center cone has vanished and is replaced by two additional tweeters (one in front as a semi-coax and one on the back side to still go dipole):







Takeover is at approx 3 KHz (passively). Frequency response is far better now. Since some aweful peaks between 600 Hz and 1 KHz were eliminated, the overall curve is quite ok now. Sound has improved drastically, compared with the previous status of full range.

Funny enough, I don´t need the previously mentioned additional gain at about 50 Hz anymore. A gain (at any bass frequency) actually does not seem to have any supportive (positive) effect anymore, it even blurrs reproduction a bit. So this gain function has been set to zero now.

I will check now whether the Alphas and the mid-treble setup are about equally loud when all are driven passively. In this case I might not need the sub amps anymore.

Regards
Till