[JoshK]

I wanted to know people's experience with making an H less deep, which will lessen the "D" and thus move the dipole loss corner up higher.  I am willing to trade the low end to try to move the higher end upwards.  I wanted to know if lessening the depth of the H would possibly also shift the resonance upwards as well, or whether it was strictly based on the dimensions between the side walls. 

Josh,
there is only one source of resonance in a H frame and - yes - those quarter wavelength resonances will shift upwards with lessening the depth of the H. There are no resonances based on the dimensions between the side walls.
Widening or narrowing the H-frame will alter the effective depth "D" of the H frame to some degree, but it will not introduce a separate resonance.

Thanks.  I have to say that at first that isn't intuitive.  I was thinking it was standing waves between the parrallel walls.  Guess that shows what I know about wave propagation. 

[chakija]

That's strange.  Do they otherwise look the same?

Yes, they do look the same apart of those tiny details on magnet...
I still haven't tried to compare with my "old" silver alpha but will do today.

[chakija]

Well, it took a little more time to compare these drivers but finally i did that and results were as i expected.
Alpha with black sticker had (as already confirmed  ) less shouting sound in mid, but low end were with less differences.
This could be because of dust cap. After i reviewed drivers little more careful i noticed that dust cap material is different or at least coating is... 
On B. it is smoother, more stiffer and it produce different sound on finger flop   
I returned both drivers and i expect refund from my dealer.
One thing i have to make clear! These are my insights and i don't expect that everyone has same results because of differences in every loudspeaker, and every person different sound  perception.
In any case, i would be greatly thankful to anyone who could report any findings relative my conclusions  .



Now, as i read interesting Richards insight again, first i hooked up monacor sp130x which scorpion uses in his Volk's OB running FR with Alpha on 6.7mH .
Comparing to my oval alnico FR, monacor gives more laid back sound with less dynamics but with fuller sound and smoother transitions. Also, sound staging seems smaller than with alnico. Another + was improved bass because of monacor's lower sensitivity. I liked what i heard...
Than i hooked oval again but Alpha FR. Gain was obvious and i got that full, smooth sound that i liked with monacor, but with rich dynamics, transparency and space.
Only thing that i miss now is that bass that i had...
 
 

[Vix]

Only thing that i miss now is that bass that i had...
 
 

Are you using Graham's T-bass?  Try it...

[scorpion]

Hi chakija,

Glad you liked the Monacor 130/X8s, for their price it's a bargain. You should read the DIY Emerald Physics thread, there might be some hints for you. Otherwise why not take down the Alnicos some dBs by a resistor, to see if you like also a more balanced sound.

/Erling

[chakija]

Hi scorpion,
I tried adding a resistor in line with alnicos and was not satisfied. It brings in a audible difference, but to worse, killing most of magic of clean, airy and dynamic sound that one had without resistor. Also, bass although more present, doesn't seems to integrate very well in this setup.
Yesterday i spent whole day listening different combination of monacor,alpha,and oval, and finally i decided to try playing FR's alone. Monacor's alone do not sound good at all, but Oval Iskra... huh, i must say that this speakers surprised me again.
With only a 10x15'' 5mm frame that they were attached to, and then just screwed on baffle in most irregular way ( drek is dangling like shark's tail  ), this little ones played bass far beyond my prospects.
Ofc. there were no signs of low bass notes, but mid and say >90Hz bass was just amazing. Also, there is dryness more present in sound followed with demonic imaging and clean sound that filled my room. When i returned alpha's again, i noticed that it gave the sound fullness and shape, but with loss of that dynamic and cleanness in overall sound...
I will definitely try alnico FR alone in proper IB.

Now another crazy idea  aa
I have 2 more almost same oval alnico speakers (same basket,magnets,cones but from a different manufacturers). I wonder if i could put these 2 on new baffle and use one alnico as a bass helper (this is if one doesn't have enough low end on IB). It is 4oms rated so it will give lower bass crossing point with inductor i am currently using. Also, with Graham's circuit i think it would work wonders ; only limiting factor is low excursion though...
One thing that bothers me in sound of alnicos is that mid beams maybe little louder than it should...would those foam fingers that Graham did with B200 help ?

[chakija]

Are you using Graham's T-bass?  Try it...

Hi Vix,

I will definitely try it in either combination  .

[scorpion]

chakija,

This will be a great excersise. Go on !
In the meanwhile I have to say that I am now going to build many new designs with a lot of different loudspeakers involved, including Greencones round and oval, but also very different speaker choise from the beginning. But everything will be based on an H-baffle with 2 Alpha15s for about 92 dB effeciency down to 30 Hz.

/Erling