sim for ancient Iskra 8" FR (HELP!!)

[Zen Mod]

I have old MJK's free Mathcad sheets , but I can't do nothing sane with them for this driver ........ probably because sensitivity is too high?

anyway - here is what I have of T/S parameters :

Fs 57 Hz
Qms 10,36
Vas 167 L
Cms 1,373
Mms 2,77 gr
Rms 0,19 kg/s
Sd 292,5cm^2
Spl 103,3db/W/m
Qes 0,537
Re 3,4E
Le 0,217mH
Qts 0,51
Z 4E
Bl 3,563
Pe 10W


TIA!

 

[GM]

No, it's specs look quite nice for a variety of alignments, but 'big' is the operative word here, so what's the largest acceptable bulk/dimensions as it will dictate the usable F3.

For instance, a max flat MLTL alignment is going to be around 362 L/41 Hz F3/46 Hz Fb if driven with a typical SS amp, so a high output impedance will either put a hump in the LF response or require a larger cab.

BTW, does it have a model name and/or number?


GM

 

[Zen Mod]

tnx GM

feel free to count on lowish output impedance of amp ;

stickers probably fell off back of magnets few decades ago ........

 

[GM]

OK, then assuming 0.8 ohms for a 4 ohm tap, raising Qts to 0.623, making a max flat alignment ~701 L. This will dictate such a large vent that you might as well make a proper TL and accept the probable excessive mids/HF damping.

I imagine this is much too large though and smaller MLTLs I simmed would probably sound fine in-room, but the sims don't 'paint' the pretty 'picture' folks want to see, so here's a 'pretty' golden ration BR of the aforementioned ~362 L you can place on stands to get the driver up to the desired height and the ~ +3 dB mid-bass hump due to the assumed 0.8 ohms output impedance should give it that vintage bass 'warmth' typical of its era:

L = 45.4275"
CSA = 287.97"^2 (recommend 28" W x 17.4275" D)
zdriver = 21"
zport = 38.7275"
dport = 12" (28.274"^2)
Lport = 0.75"
density = 0.2 lbs/ft^3 (typically line the top, one wall and back with 1" thick acoustic fiberglass insulation or similar)

All dims inside (i.d.) and approximate and up to a point, retuning the vent can adjust for a different output impedance, so I recommend a removable port baffle in case you need to use a different port area.

GM

 

[Zen Mod]

tnx GM

oh Boy , that's certainly Voice of the Theater area ...
big ugly cab with huge opening ......

I imagine that any sort of IB will do the job , dependent of room positioning ....

in any case - tnx again for help , puzzle solved .

here is old sim I made with JBL Speakershop , years ago ;

I just guessed Xmax of 2mm

 

[GM]

You're welcome!

Yeah, and the extra loading of a MLTL only increased the vent's area. Oh well either cover with a grill like Altec did with the later A7s or vent it out the bottom since it needs a stand.

A golden oldie! Someone sent me this program back in '94, but it got corrupted somehow and doesn't work anymore.

Oops! Forgot the 'pretty picture' :

GM

 

[Zen Mod]

.....
A golden oldie! Someone sent me this program back in '94, but it got corrupted somehow and doesn't work anymore.

......

you need that golden oldie , even just for sentimental reasons ?

 

[GM]

Funny you should mention it, I'm mostly ignorant about computers, but got curious yesterday and Googled/downloaded the missing file or whatever you call it and then it said it needed another one, and another, etc. until six of them later it finally booted up.

Unfortunately, it now displays a black plot on a charcoal gray field, so can't see it clearly enough to be usable, but I don't have the HELP files and haven't been able to find out how to change it.......... Plus I'm curious why it doesn't display like it use to.

GM

 

[Zen Mod]

Funny you should mention it, I'm mostly ignorant about computers, but got curious yesterday and Googled/downloaded the missing file or whatever you call it and then it said it needed another one, and another, etc. until six of them later it finally booted up.

Unfortunately, it now displays a black plot on a charcoal gray field, so can't see it clearly enough to be usable, but I don't have the HELP files and haven't been able to find out how to change it.......... Plus I'm curious why it doesn't display like it use to.

GM

shoot me with your e-mail at >choky@neobee.net<