Unsure about this design (twin vented sub for HT). Please help me! :) (1 Viewer)

[Greg Monfort]

Not really an equal, but if it performs as well as its specs imply, it looks like a viable alternative to a Tempest. Really though, just based on sims, the two 12" look like a better deal in a typical room with some gain if their price is right, though the cab is somewhat larger.

GM

 

[Javier_Huerta]

Hi Greg! Thank you very much for your help!
I decided to do DIY right, and guess what? I bought a pair of the 15" drivers! The simulation of those drivers was enough to help me make up my mind about what I really wanted for my new home theater (which I want to be the ultimate in term of bass dynamics and accuracy). The simulation actually showed a pair of the 15"'s would *outperform* 4 units of the 12"'s!
As for the amp, I found this one on Radio Shack. It seems it's a very, very good deal. I wonder why I haven't seen it mentioned before:

Continuous Output Power:
Stereo at 1 kHz: .......................... 125 Watts x 2 (8 Ohms)
Stereo at 1 kHz: .......................... 175 Watts x 2 (4 Ohms)
Bridged at 20 Hz to 20 kHz: ................... 250 Watts (8 Ohms)
Bridged at 1 kHz: ............................. 350 Watts (8 Ohms)
Total Harmonic Distortion: .............................. 0.1% at 80 Watts
Frequency Response (10 Hz - 50 kHz): ............................ +/- 3 dB

Since I will use the subwoofer output of my amp, I don't need an external crossover to run it. I guess 350 watts RMS total at 4 ohms will be more than enough for the drivers.
Anyway, I think I'm all set now. Do you have any links where I could learn more about speaker building, Qs, box tuning, etc.? I don't want to be too much of a bother

 

[Javier_Huerta]

Funny thing happened.
The store cancelled my order because I could have got free shipping, yet I forgot to order it. So I'm back to square one. I can buy any subwoofer I want to now.
I need some help here, please . I've seen the simulations. The 12" perform almost as good as the 15". Is there a specific reason why I should go with the 15" drivers? Their specs are a lot better, yet when I simulate them both come almost as equals.
Can I go the 12" route and use the saved money to buy a decent amp? Do you think the sub will sound good, based on the numbers?
Thank you very much for your help.

 

[Javier_Huerta]

Edit - double post

 

[Greg Monfort]

>I need some help here, please . I've seen the simulations. The 12" perform almost as good as the 15". Is there a specific reason why I should go with the 15" drivers? Their specs are a lot better, yet when I simulate them both come almost as equals.
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If the specs are accurate, the sims tell the tale for a given level of construction/materials quality.
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>Can I go the 12" route and use the saved money to buy a decent amp? Do you think the sub will sound good, based on the numbers?
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I've already given my opinion.
Can't really comment on the amp since there's not enough info. For sub duty I recommend a prosound amp. What brands are available down there?
GM

 

[Manuel Delaflor]

Hello Javier!
I haven't visited the DIY forum in quite a while, anyway, I hope is not to late to help.

Anyway, I'm tired of looking for a semi-decent driver around here.

Talk about that to me! I initiated that thread because of that, and the CV's were the only "descent" drivers I could find. That was before I knew that my brother (who lives in USA) was coming to Mexico. Of course, I abandoned my CV plans and immediately ordered a Tempest!
Back to your options I think you will be ok with the CV's, the will not reach the same level of SPL nor dig as deep in the lower end, but for HT they will give you a nice punch from 30Hz and up.
Let me know if you want to buy a Tempest, apparently you can order one by mail and you will have a 50% chance of not paying taxes. I think I have that info somewhere.
To bad I arrived this late to the thread, I want to sell my Part Express amp and buy a Margules dedicated sub amp instead! And you were a perfect candidate.

 

[Javier_Huerta]

Manuel: You got a PM. We might work something out about that Parts Express amp
BTW, I found a bug in WinISD Pro! That's the reason I was so confused. Apparently, when you start to overlap various simulations, the program automatically assigns all the drivers the same sensibility.
What was happening was that I was simulating my response curves for both drivers and suddenly, the program started telling me that the twin HED-12 would hit as hard as the twin 154s. Which is simply not true. One simulation done under WinISD (not the Pro version) showed me that the twin 154's have around 8 dB more SPL under any wattage! So even a single 154 will outperform the twin HED-12's, which is exactly what I was thinking about.
Thank you all for your help. I guess I'll e-mail the writer of WinISD Pro to tell him about the bug.
Javier (still undecided about what to build).

 

[Javier_Huerta]

I think I have hit jackpot. Maybe this is the winning design I need.

I already made up my mind about getting a pair of the Cerwin Vega 154 subs. The extra sensitivity is just too much to ignore (6 dB!). The 12" would need 3 times the power in order to equal the SPL of the 15's, and the 15's can handle more than twice the power of each 12". So I'll end up with a terrific, long term sub.

The box will be a 400 liter one. I still haven't decided the tuning frequency. I'm playing around with either 19 or 20 Hz. Both frequencies have a nice downward slope, similar to that of the Adire EBS box. The thing is, when tuned at 20, I get a sudden change of slope at exactly F3, which I think is no good thing. When I tune it at 19, I lose some frequency response. Any recommendations?

As for the rest of the specs, the thing will behave very similarly to a Tempest, (especially in GD), BUT it'll have a tremendous advantage: it has 6 dB more of sensitivity, which means I'll end up with a sub that won't go down as deep, but will definitely blow the house to pieces.

As soon as I decide the tuning frequency, I'm all set. Thank you all very much for your help. It has been greatly appreciated.

 

[Manuel Delaflor]

Javier
Im digging old posts, as you probably imagine I wonder what happened to your plans on the Cerwin-Vega Vega 154?

 

[Javier_Huerta]

Hola!!!

There are no more CV-154's in México that I know of - I searched everywhere! The distributor told me that since C-V had changed hands, they had problems with suppliers.

All I could find was the HED family. Which is sad, since the 154 looked like a *very* powerful alternative. It couldn't go as low as the 12's, but it had more sensitivity. And Xmax, and swept volume...

 

[Manuel Delaflor]

Sad news!
Im thinking again in those HED12's I want to make another sub, this time for my HT. I know you are making an enclosure for your Tempest, what do you plan to do with all those HED's???
I found them at 784 pesos and I can pay them 12 months without interests! But even then I don't like to buy things that wont work... Did you ever tested just one, or two, in a vented design?

 

[Javier_Huerta]

Are you still interested on selling the PE amp? We could make a trade

 

[Manuel Delaflor]

I still need to think about the Margules sub amplifier, besides I will try to find a place that allow me to test the driver before I decide to keep it... that's why I asked you about your tests. Does it really have the XMAX they say it have? Did you tested it in a vented box?