[spanish68]

I will like to compare the efficiency of the same sub in two different enclosures. Lets say you have a AE AV15X driver in a sealed 4cf box and then decide to use the same driver in a 8cf PR/ported box. Lets say you are using 1,300 watts to power the sub.

My question is, what will be the efficiency of the sealed vs the PR/ported box? Will the bigger box be 3db's more efficient? Also, how will the power of the amp play into the equation? The sealed box might use the amp's full power through the frequency range (within xmax), while the PR/ported box, due to its efficiency might not take the full amp's power in the low-bass without going past its xmax.

So you lower the amp's gain to produce, say, 650 watts to keep the sub within its xmax at the low bass and use a high pass filter below its tuning. You will gain low-bass vs the sealed box but will loose headroom in the mid-bass due to the low tune of the sub and the fact that you're not using the amp's full rated power, right? Correct me if I'm wrong.

 

[Mike P.]

Lets say you have a AE AV15X driver in a sealed 4cf box and then decide to use the same driver in a 8cf PR/ported box.

How the AE AV15X will perform in 4 cu.ft. sealed or 8 cu.ft. ported will depend on the subs parameters. WinISD will give you a ball park idea on the performance comparing the 2 cabinets.

 

[Moonfly]

I figured I would throw up an example of what WinISD can do, I have done nothing to try alter these, just ran with the default parameters the programme has selected and dialled in 1300watts. It does show however, the kind of differences you can expect to see between the designs. You can obviously tweak these to your hearts content. Box size for the sealed sub came in at around 75 litres.

 

[spanish68]

Moonfly, thanks for those graphs. Interesting the fact that the ported box sub goes past its rated xmax from the low 20hz to high 30hz with a high peak of 28 xmax (5 xmax more than the sub's rated xmax), which would make the sub distort more at those frequencies or even bottom out the driver. The sealed seems to handle that power better until the mid 20hz area and below.

It seems to me that the AV15X sealed would work well (within its rated xmax) with around 1,000 watts in a small sealed box. The ported box looks to work well with around 700-800 watts (within its rated xmax), is my guess. A high pass filter around 18hz should cover the sub below its tuning. On the other hand, the flat frequency response of the ported sub sure looks good.

The reason I asked is because I went from a 4.5cf sealed to a 8cf PR box with the AV15X tuned at 15.5hz, (I needed it to cover my big room), powered with 1,300 watts. On a couple of heavy low bass scenes the sub made a clanking noise (bottomed out). On the other hand, my previous sub, TC 3k handled those scenes without any issue (its rated at 30 xmax). I have ED EQ2 which has two bands and a high pass filter. I had the filter around 14hz and the ED LT1300 amp's gain at 12. Should I just reduce the amp's gain to produce a little less power, say around 9-10 on the amp's gain? Also, being that the EQ2 is only 12db/octave (I thought it was 24db/octave), should I set it to around 20hz or so? Finally, I had the sub at 75db with the rest of the speakers (2-3db's hot), should I just set it flat, say 72-73db's?

With a ported/PR sub that is twice the size of a sealed box (same sub being used), how much more efficient will the big box be compared to the small one? I also will like to post some pics of my 8cf PR sub build but it won't take my pictures (resolution too high). How do I show the pictures at a lower resolution? What do I need to do? Thanks again.

 

[Moonfly]

Moonfly, thanks for those graphs. Interesting the fact that the ported box sub goes past its rated xmax from the low 20hz to high 30hz with a high peak of 28 xmax (5 xmax more than the sub's rated xmax), which would make the sub distort more at those frequencies or even bottom out the driver. The sealed seems to handle that power better until the mid 20hz area and below.

The sealed subs seems to handle the power better, in reality it doesnt. Think about it, the driver doesnt move as much for a given amount of power. This is because of the air suspension inside the sealed box thats resists the driver. Less movement = less air moved = harder to go lower. On the plus side, it can help protect your driver as you noticed.

It seems to me that the AV15X sealed would work well (within its rated xmax) with around 1,000 watts in a small sealed box. The ported box looks to work well with around 700-800 watts (within its rated xmax), is my guess. A high pass filter around 18hz should cover the sub below its tuning. On the other hand, the flat frequency response of the ported sub sure looks good.

The driver is rated to 1000 watts handling so while it will take a little more, thats about the limit the VC can handle. Like youve spotted, it works well within a sealed enclosure. The beauty of sealed subs is that they roll off smoothly which is why they give a flatter response and reportedly a smoother sound if you agree with what some say. It does make them a little easier to integrate. With the ported subs, the port boosts output above the natural roll off of the sealed response to keep it fairly level right up to the tune point of the port, it then just drops back to where it would be with the sealed subs response pretty quickly. The difficult bit with ported subs is making sure port air speed doesnt get to high.

The reason I asked is because I went from a 4.5cf sealed to a 8cf PR box with the AV15X tuned at 15.5hz, (I needed it to cover my big room), powered with 1,300 watts. On a couple of heavy low bass scenes the sub made a clanking noise (bottomed out). On the other hand, my previous sub, TC 3k handled those scenes without any issue (its rated at 30 xmax). I have ED EQ2 which has two bands and a high pass filter. I had the filter around 14hz and the ED LT1300 amp's gain at 12. Should I just reduce the amp's gain to produce a little less power, say around 9-10 on the amp's gain? Also, being that the EQ2 is only 12db/octave (I thought it was 24db/octave), should I set it to around 20hz or so? Finally, I had the sub at 75db with the rest of the speakers (2-3db's hot), should I just set it flat, say 72-73db's?

The watts an amp supplies isnt fixed, its dynamic depending on what the your trying to get out of the system. Adjusting the gain level merely balances the levels between speakers, and if you push the volume up enough you could still plough 1300 watts in. If you want to design your sub build to remain within xmax, you need to monitor it in WinISD to see its limit. When you then build your sub it should be mechanically limited to be within its xmax. Of course this will come with a set of performance limitations so its then down to looking at the various design types to see which will deliver what you want.

Applying filters is fine, but dont forget if your cutting frequencies to protect the driver your still cutting those frequencies. If you want them in your content you have to find the design that works best for you.

With a ported/PR sub that is twice the size of a sealed box (same sub being used), how much more efficient will the big box be compared to the small one? I also will like to post some pics of my 8cf PR sub build but it won't take my pictures (resolution too high). How do I show the pictures at a lower resolution? What do I need to do? Thanks again.

Well the ported box is giving an extra 12db at 20hz, which is a of a lot, but the design you go for will ultimately dictate the extra efficiency,and as you noted, in the above projection that extra spl exceeds xmax.

I'll have a look at a good all round ported design now, post it, and see what you think. You should be able to get an idea if you can improve on your original build with that driver or not. Did you have a max box size in mind?

 

[Moonfly]

OK, here is the projection, 3 subs again (including the sealed one for reference), and a couple ported designs, tuned to 20hz, and one larger than other so you can figure in some size ideas. As you can see, the LLT just nudges XmaX (but not xmech), which can be solved with a bit of a tweak if desired. All these subs can be run without any filters for ease of use/build/ and are an example of a design with mechanical limiting applied rather than electronic. All are modelled on the drivers maximum recommended 1000watts. Inputting more will require you paying attention when you apply plenty of volume. Notice how the smaller of the two ported designs incorporates that smoother response you liked the look of in the sealed design, rather than just going for out an out spl at low frequencies.

See what you think.

 

[spanish68]

Moonfly, my enclousure is done. Its a 2100 gram 18" PR with a tuning of 15.5hz in a 7cf enclosure. I added 5-lbs of polyfill which should make the enclosure closer to 8cf or so. The amp is ED LT1300 amp with 1,300 watts and the EQ2. I have both the TC 3K and the AV15X subs which have been tested in that enclosure.

I like the AV15X sub better which has much better SQ than the TC sub. From about 30-40hz and up, it walks away from the TC sub. On the other hand, the TC 3K sub has deeper and better low bass than the AV sub below about 30hz, good in my big room. I have bottomed out the AV sub in a couple of occasions running some heavy deep bass scenes which the TC handled without no problem, probably due to its greater motor and xmax compared to the the AV sub. On the other hand, I think the 1,300 watts is a little too much for the AV15X sub in that PR enclosure.

I was thinking of using the TC 3K sub in the PR enclosure with a crossover in the 40-50hz range to handle the low bass and do a 3cf sealed box for the AV15X sub to run the mid-bass, 40/50hz all the way up to 80/100hz. Since I would place it next to the center channel, maybe I could even get away with a crossover of 120/160hz without localization issues and leave the PR sub in the corner. I already have a ED LT550 plate amp (550 watts) doing nothing which I could use. All I would need is a crossover.
I know the TC 3K sub takes over 2,000 watts in a small sealed box but since its in a big box with more efficiency, the 1,300 watts might be close enough to run it to its full potential. The only thing I worry about is integration issues between the two subs.

I'm going to adjust the amps gain, raise the high pass filter to around 20hz (from 15hz) since the EQ2 is only 12db/octave and run it "flat" (from the current 2-3 db's hot). If I like the results, I might just run the AV15X sub by itself and sell the TC 3K sub. My frequency response with the AV sub is within 6db's from 16hz-100hz in the PR set-up while the TC sub is flat up to about 60hz and then falls off. Any input is appreciated.