Need help with sub design

[pjpoes]

I have a sub box that is 1.75 cubic feet made from 1" mdf. I bought it from a local builder a while back, and never used it. I want to turn it into a subwoofer now that I have the time and resources. The box was never cut for a woofer, just assembled in a basic manner, and finished in black gloss paint.

My thoughts were a 12" woofer, and at that size, I thought probably sealed, but I am just not sure if thats what is best. My other thoughts were with passive radiators. I know how to design a sealed setup ok, but I am not sure about a passive radiator setup. Also, though I have software, I have not mastered it yet and dont trust the numbers i get. I was wondering if anyone could run some numbers with their software and let me know if my speaker choices would work, and in which setup, sealed or PR. Also, if PR, what do I need to tune the PR's too. Thanks, I will really appreciate this.

My first idea is using the DAYTON RSS315HF-4 12" HIGH FIDELITY SUBWOOFER.
http://www.partsexpress.com/pe/showd...number=295-464

My second choice is the TC Sounds sub from O Audio,
http://www.oaudio.com/TC2_PLUS.html

My third idea is the Custom Audio Solutions AV12
http://yellow.mynethost.com/~bv12636...02e8cf523658fb

For passive radiators, I have the option of the CAS from the above link, the Dayton PR's, and the Peerless passive radiators.

My question besides what works in my box, is what people think would be a best choice for my purpose. I have listened to a Titanic sealed subwoofer and felt that it created a lot of deep bass, but lacked finesse, and seemed high in distortion. It was in a proper box, so I really feel it was probably just an issue with the woofer design. The Refrence Subs from Dayton I have not heard, but I hear are a copy of the Peerless XLS subs, and offer similar low distortion. Hearing this, I wonder if such a choice would give me the best sound, at the expense of some output. The other two choices seem like great values, the O audio and TC Sounds woofers, but I am unsure of what category they will fall into. With such extreme amounts of excursion, can they possibly sound as good as a Peerless XLS or possibly the Dayton Refrence subwoofers. I do believe that my priority is going to be in quality over quantity. I also would like my inroom response to go down to 20hz atleast. I am hoping for output in the neighborhood of about 105-115 decibles, which will match my main speakers well. Any help and suggestions would be great.

Oh yes, and for an amp, I am thinking of the 0 audio Bash amp, but I am also considering going with a much more expensive option. A Behringer PA amp, which seems like a good deal, and then using it with a crossover I made once, and in either scenerio, I am thinking of buying the sub woofer optimizer electronic room eq from Speaker City. Other idea's I had was to use the Linkwitz cuircit or ELF cuircit with a sealed box, but again, I am limited to my 1.75 cubic foot box. Let me know what you think, I will greatly appreciate this.

[pjpoes]

Using WinISD, which is the software I currently have to use, I found that the Custom Audio Solutions was the only one that would work in a ported box of 1.75 cubic feet acceptably. Can anyone confirm that to be true. Also, can anyone let me know what passive radiator setup would work best in such a box? Tuning, Size, etc.

I decided to add this bit because I figured that what I asked in the first post is really a lot, and I should try and get some of this myself, and just rely on you guys to steer me in the right direction. First, because I need to learn to use the software, and second, because I am sure most of you dont want to be bothered doing other peoples projects for them. If anyone knows of a Passive Radiator primer or software calculator, I would appreciate that, and possibly be able to use that.

[simon5]

WinISD Pro works well with Passive Radiator boxes. You could also use UniBox.

Your box is 1.75 cu.ft internal net? Or 1.75 cu.ft external?

Yes, the Acoustic Elegance driver is one of the best in that small box if you want to use a passive radiator. I would tune it between 20 and 25 Hz, depending on what do you want.

[pjpoes]

My only concern with the Acoustic Elegence driver is I hear from some how long it takes this guy to send out the drivers. I have been told he has never stiffed anyone, but that he sometimes takes quite a long time. However, the Acoustic Elegence Driver does seem to work in a wide range of boxes well. Oh and its 1.75 cubic feet internal dimensions. Its actually closer to 1.8 cubes.

I'm not dead set on the Passive Radiator design yet, to be honost. I am still trying to figure things out. I designed a sub on Winisd Pro using a Linkwitz transform cuircit, a single 12" Dayton Refrence sub, and a little bit of equing, and had the model flat from about its 19hz FS to my cut-off. I have been intrested in that sort of design as well. The Passive radiator will probably be more efficient, but with 500-1000 watts of power, I am not real concerned.

[BAM]

The AE Speakers driver (AV12) is in stock at AE Speakers, and John (AE Speakers proprietor) remarks that lead times are very low on getting in-stock drivers shipped out. A lot of the trouble John has been having on filling orders was WRT the Lambda Series drivers which have to be built-to-order by hand. The Lambda series has a wide variety of configurations, necessitating the build-to-order process. The AV series just has one configuration for each size of driver, so it is reasonable to have a large stock of the woofers on hand. I have an AV12 and I can tell you it is a much beefier driver than any of the Dayton RS drivers. It isn't spec'ed to handle the 700 watts of the HO version of the Dayton RS driver, but some have had success with that much power on an AV12 woofer. The AE Speakers ratings are relatively conservative. At any rate, that much amplifier power is expensive, and the AV series from AE Speakers has a longer linear excursion, so it would have even higher output before significant distortion. I have never found the limits of my AV12 in a 3 cubic foot box with two AE Speakers 15" 1400g passive radiators, powered by a Parts Express 500w amplifier. The AV12 also does well in mid-sized sealed boxes too. Ask Paul Spencer. I'd recommend the AE Speakers option, and since the AV series is on sale for lower introductory prices, you should jump on this.

[pjpoes]

That sounds good, how about Sound Quality. I had heard that a great deal of these long excursion drivers, even the Brahma for instance, had fairly high rated distortion compared with the Peerless XLS, which I believe the RS to be a copy of. That was my other concern. I fully expected the driver from AE to be a heavier duty driver, and I knew it was more efficient and probably better built, but it doesn't offer the shorting rings and other features to lower distortion.

Whats the advantage of two passive radiators over one, can it be used as effectivly with one, or will it need greater mass then? I should probably try modeling this before I ask, to be honost, I think I did and it modeled well with one passive radiator. Anyway, let me know some more details, I would be intrested.

[simon5]

It's true that it doesn't have shorting rings, but the distortion is quite low I'm sure. I'd expect it to be at least equal with the RS line IMHO.

[pjpoes]

Ok well I have a few more questions, to check what I am seeing.

I first modeled the AV15 and was not as happy with what I saw, it was peaky I thought, typical of the response I see from store bought subs. I may not know what I'm doing with this software, but I was having trouble getting the right passive radiator setup with that. I then switched to the 12" version, the AV12, which is what I meant to model anyway. I only mention this becuase, as I said before, I feel that I am still learning this software, and may be doing certain things wrong.

I let it pick the ideal box, and it came up with 1.85 cubic feet for a passive radiator setup, and again had a sort of mound or hill like response. I increased the size to 3 cubic feet to see how that looked, and the low end was raised, it also improved the my FS. I am not sure how important this is, but I am trying to achieve a system response with an FS in the 20hz range. Currently I have it setup with 2-15" passive radiators and I am debating between the 1400gram and 1050 gram model. Both model well in differen ways. I probably will go with the 1050 gram model with about 1100-1150 grams of weight on it. I also modeled the 700 gram model with 1000 grams on it, and it also models well, it gives the least peak in the 50hz range.

I also have a Butterworth lowpass filter at about 85hz and a parametric eq set at 20hz with a Q of 1 and 2.5 decibles of gain, this gave me an FS of 16hz. The reason I did the eq was that most amps now a days has a single eq band, so I figured I would try it. First, does anyone know if the eq will cause problems with excursion. I didn't see any in my model, but its just a model, so who knows. Anyway, how does all that sound, am I going about this the right way. Will increasing the box size screw something up I didn't notice.

[simon5]

If you use WinISD Pro, it can't calculate the optimum box parameters for a passive radiator box, you need to tweak by hand.

If the passive radiator excursion doesn't go over Xmax over 15 Hz and the same thing for the driver, then you're probably ok since the simulator take into account the filters.

Check the graphs and look for overexcursion.

I'll try to model a bit later to help you.

EDIT: Forgot to add the "passive radiator box" bit of information, WinISD Pro can calculate the other boxes correctly.

[BAM]

Actually, I talked with John about this, and when the original AV12 was being developed, TC Sounds tried coating the pole piece in copper but it actually increased the Le! That is why it has been left bare. If you want copper, order a Lambda PC12 with the copper faraday motor, and then be prepared to wait...

As far as the bass quality I'm getting now from my AV12, distortion isn't even audible. When I really crank it up, I still don't ever exceed Xmax, and so the THD remains inaudible. When I built my AV12 passive radiator box, I built it from the recommended 3 cubic-foot and 1400g passive radiator design on the web site. This thing moves a lot of air, and it's fun to watch it transfer the load to the passives at the really low notes (~30-20 Hz). I have pulled the passive radiators to the extent of their suspension travel in this cabinet. I have never bottomed the driver. It is amazing what this enclosure design can do, and it can crank out the lows at any volume I care to listen at.