Building Two way speakers with Ahuja 12" and Compression driver

[Naveenbnc]

Your current setup with Ahuja extended range is a kind of dipole with horn loading from the rear. If you are willing, just reverse the mounting of the drivers so that they face inside the box and also place the boxes on the reverse, that is, now the drivers with open rear, mounted on the baffles on the back of the box, will be facing the room. Something like this:

View attachment 30258

Keep them away from rear and side walls and play the same movie tracks and see what difference it makes now and compares in sound, to your present mounting.

I did not ever play extended range drivers like this but only bass drivers and it supersedes everything in bass I have build so far, including the TL subwoofers. It becomes a horn loaded dipole bass and has concert level reproduction. Your drivers have decent 45 Hz Fs, so they might do very well. Just for fun, try it if you wish.

Now that Ahuja are a bit dominating, i have to add a second sub soon. If this idea works with bass, i don't mind building my next sub this way .

 

[Naveenbnc]

Place a cement brick inside at the base. Mine had 2 bricks inside and sometimes I sat on the box !!!! (Its sounded way better, though nothing to do with me...... Ha Ha....in case you may ask me to come and sit on yours !!!! )

 

[Naveenbnc]

Place a cement brick inside at the base. Mine had 2 bricks inside and sometimes I sat on the box !!!! (Its sounded way better, though nothing to do with me...... Ha Ha....in case you may ask me to come and sit on yours !!!! )

Hi Yogibear.... just for fun, I would like to try your suggestion with IWAI 12" Subwoofer driver.
Please see the attached pic.
Can you suggest an approximate size of the box please .... I can share TS parameters if required.
(i learned some basics on sealed and bass reflex enclosures, but don't know how if it changes with your idea)

 

[Naveenbnc]

Can i make the box, same size as the ported sub designed for this driver ?? Just a guess

 

[Naveenbnc]

Naveen, pl share TSP just for the idea though it’s a kind of hunch based design but still I can suggest the dimensions better.

Thank you


IWAI 12" 200W 4ohms
"Title: Measured Parameters"
"Method: Mass-loaded (112.220 grams)"
"DCR mode: Measure (-0.30 ohms)"
"Area (Sd): 522.79 sq cm"
"QC-limits file: "
"Last setup file: C:\MLS2000\SPO4K.SET modified "
"Series resistance: 75.00 ohms"
"Stimulus level: 1.00 volts"
"SPLref reference impedance: 8 ohms"
"Large units (volume = liters, mass = grams)"
2.064 "RMSE-free Ohms"
31.680 "Fs Hz"
3.553 "Re Ohms[dc]"
39.439 "Res Ohms"
2.808 "Qms "
0.253 "Qes "
0.232 "Qts "
0.857 "L1 mH"
1.968 "L2 mH"
18.786 "R2 Ohms"
2.255 "RMSE-load Ohms"
113.367 "Vas(Sd) liters"
85.457 "Mms grams"
295.332 "Cms �M/Newton"
15.456 "Bl Tesla-M"
96.891 "SPLref(Sd) dB "
0.556 "Rub-index "
Xmax +/-7mm

 

[Naveenbnc]

 

[Naveenbnc]

Done !!
Il see if I can find a driver with Qts above 0.5

However, since the box is not complex, il just give it a try without high expectations.

In fact my Ahuja driver has a Qts of 0.72. But its Xmax is low, only 2.5mm. So it may not do a good job for a Sub.

 

[Naveenbnc]

Hi yogibear.....
By any chance, can you suggest any 12" sub driver with Qts above 0.5 ....

(This Iwai sub is excellent for its price around 4 to 5k) At this moment I can not experiment with expensive drivers. If you have any driver in mind that come around similar price, let me know please.....il get it

 

[Naveenbnc]

Sure ....thank you i will try that.
Even i do have the same understanding.
Bigger cone with greater xmax will move more air. At 60% volume my Iwai sub moves wildly that I start worrying about going any higher. And I can barely see any movement in Ahuja drivers.

As you said....other specs may mean a lot !!!
Thanks for the info

 

[Naveenbnc]

Don't worry too much of Xmax. if you already have that Iwai sub 12", no harm in trying.

Else buying a 12" high Qts driver will be better. You need to search Faital pro even Beyma etc. Qts above 0.5 and Fs around 30-35Hz will be just fine.

As far as Xmax is concerned, some rely too much on it, I rather look for specs like dB rating, Fs, and worry less about Xmax if the cone size is 14-15" or larger. Little or no cone movement but high dB drivers with large cone areas excel over their smaller peers with huge Xmax. This is valid with Horns and OB designs. Ported or sealed is different story.

Just experiment with any woofer 12" you have, with reasonable specs to do low bass duty.

just out of curiosity i checked. Beyma has around 15 models in 12" subs.
Out of which only 2 drivers have a Qts near to 0.5
The rest are all in the range of 0.35 or less.
Faitalpro doesn't have any 12" driver with a Qts near to 0.5

Il try with my existing Iwai driver for sure.

 

[diyaudio]

Choose a driver that meets your sensitivity and xmax requirements. Get Fs down and increase Qts by adding mass.

 

[diyaudio]

See AS15-X200 from Ahuja

 

[Naveenbnc]

See AS15-X200 from Ahuja

I saw this one but couldn't dare to work with 15" because they are huge for my room.

It has excellent sensitivity, and other parameters are also nice.
But Fs is only 45Hz.

And you are suggesting we can bring the Fs down and increase the Qts by adding weight. (Please correct me if I'm wrong)

Qts is already 0.54.... Hope there won't be any negative effects if it increases further.

 

[Naveenbnc]

It’s a huge call looking for 12” or above high Qts drivers with high dB and low Fs. Else OB would have been around in abundance with great fan following.

Ahuja might have one. But it’s 15” I think.

Particularly with Ahuja drivers, I could not judge which drivers are suitable as subwoofers and which drivers are suited for pa speakers. (May be I have to get more expertise with reading specs)

But the price is so affordable that I can just give it a shot whether it works or not. Il try it !!

 

[Naveenbnc]

 

[Naveenbnc]

I successfully experimented with Qts 0.68 and Fs 39 Hz 15” driver and in the same horn dipole open box and it shattered my 32hz Miller & Kriesel subs (two of them vs One ) in every aspect of bass reproduction. So you may want to try that Ahuja driver.

Now I cant resist without trying !!!

The reason I could never convince myself that Ahuja can be a good sub is ....
Most of them don't have Fs below 45Hz..... and Xmax is below 2.5 (my earlier understanding)

From the above table it looks like my "existing" DX12 F200 itself can be good to experiment with a Qts 0.72 (But Fs is 50Hz)
And @diyaudio suggested AS15 X200 is a good bet with 45Fs

So Il try with my existing DX12 F200, Iwai, and also AS15 X200

 

[venki7744]

I dunno how one can lower Fs of a Driver but adding an inductor ( in case of passive network) increases the Qts a bit.

Easier way to lower FS/ increase qts is by adding mass to the cone. You can simulate this with winisd.

 

[Naveenbnc]

That's great to know !!
What do you stick generally ???

For temporary experiment, i would stick carpenters tape (easily removable) on all four sides uniformly/symmetrically.

On the tape, we can stick some mass like....silicon sealant, glue mixed with saw dust and made as a paste, etc etc .... Any thing similar, that can be applied as thin layers.

When we are very sure on how much mass to be added, and if we want to add permanently, then we can think of different materials ... Like thin strips of rubber (cycle tube etc etc )

But that's my idea....any better ideas ???

 

[Naveenbnc]

Somehow I don’t like to play with driver cone, surround or even magnet / motor assembly to change its specs. In my opinion if you are doing it then your choice of the driver is wrong for the job.

Absolutely agree with you. I m not mentally prepared to tamper with driver. That is the reason I didn't even attempt to add a phase plug earlier, when I realized a narrow HF dispersion. I simply thaught lets build other speakers with different drivers.

 

[diyaudio]

Technically there is no need to change the Qts or Fs of the driver, withing reasonable variation any decent Qts or Fs can be used. However you started with a target Qts and Fs in mind and hence the replies. Also do note, ading mass changes the sensitivity of driver, which has to be factored in the crossover design.

OB/Dipole is xmax hungry, if the driver has sufficient xmax then the most important requirement is met. Now, lets see Fs and Qts, these two will give you a flat or peaking or over damped (drooping) frequency response. Eq can easily correct the frequency response.

First implement your crossover on PC with a sound card ie active setup. Lots of parameters can be changed on PC in a jiffy. Measure and apply EQ to get a flat response then make active analog or dsp based crossover.