Ported or Sealed Mains with a Subwoofer?

[stevem]

I need a little help. I'm planning to build new enclosures for my mains, but this time they are going to be used with subwoofers (for both music and HT), crossing over at 80 Hz. My woofers are 1401ND which will now cover the range from 300 Hz to 80 Hz, handing off to a pair of W1500H below that.

Since I'm now crossing over to a subwoofer, should I use a ported enclosure for the 1400ND, or would a sealed box be better? Does a port contribute anything in this scenario? If I use a ported box I will probably go with a 2.8 cu ft tuned to around 35 Hz. I'm not sure what size to use if it's sealed. I will really appreciate any comments. Thanks!

[Allanvh5150]

I would go with a ported cabinet. Port it as if you are using the 1401's all the way down and then cross them over at 80hz.

[duaneage]

I would use a sealed enclosure for the following reasons:

1. The impedance curve will be simpler and not have a double hump. If you are using a passive crossover this will present few problems.

2. Sealed enclosures are easier to build and tune correctly. Adding fiberglass or solid blocks of wood makes it easy to nail the exact tuning.

3. With a sub you don't need the extra deep bass a vented enclosure brings.

4. Sealed enclosures have superior transient response to vented enclosures.

5. Sealed enclosures can be smaller in most cases, smaller speakers can usually be an advantage.

I didn't check the T/S parameters for your driver but if the Qts is around .35 to .40 it may be better for venting. Above .40 and your looking at a Sealed box driver (generally) that has a higher degree of internal damping in terms of electrical and mechanical Q. A driver with a low Qts of below .30 makes a bad Sealed Box driver since the cutoff will be very high and the box has to be very small to raise the Qcb up to an acceptable minimum of .5 to .707

By contrast a driver with a higher Qts does not require radically shrunken boxes to achieve the desired Q. In your case a system that rolls off naturally around 80 hz with a Qcb of .707 woould be ideal, but I would focus on the Qcb of the system and using filters (passive or active) to achieve the proper rolloff.

[speakerdave]

I've thought about doing the same thing, but I'm not done messing about with my M9500 wannabe's and have not had the time to check out my ideas for using the 1400nd above a subwoofer.

To maintain efficiency, and to be making a box that you know will work in and of itself, I would first try the 2.8 cu ft box as in the upper chamber of the M9500, ported out the back, over a sealed subwoofer.

[stevem]

I would use a sealed enclosure for the following reasons:

1. The impedance curve will be simpler and not have a double hump. If you are using a passive crossover this will present few problems.

2. Sealed enclosures are easier to build and tune correctly. Adding fiberglass or solid blocks of wood makes it easy to nail the exact tuning.

3. With a sub you don't need the extra deep bass a vented enclosure brings.

4. Sealed enclosures have superior transient response to vented enclosures.

5. Sealed enclosures can be smaller in most cases, smaller speakers can usually be an advantage.

I didn't check the T/S parameters for your driver but if the Qts is around .35 to .40 it may be better for venting. Above .40 and your looking at a Sealed box driver (generally) that has a higher degree of internal damping in terms of electrical and mechanical Q. A driver with a low Qts of below .30 makes a bad Sealed Box driver since the cutoff will be very high and the box has to be very small to raise the Qcb up to an acceptable minimum of .5 to .707

By contrast a driver with a higher Qts does not require radically shrunken boxes to achieve the desired Q. In your case a system that rolls off naturally around 80 Hz with a Qcb of .707 woould be ideal, but I would focus on the Qcb of the system and using filters (passive or active) to achieve the proper rolloff.

I checked, and the QTS for the 1400ND is .235. I do have a box program, and it suggests a .835 cu ft sealed enclosure, which is awfully small. Another poster (why did you pull your post?) made some good points, and yes I use a digital crossover and EQ (the BSS FDS 366T) for all the drivers.

In light of the above, should I just stay with a ported box?

[speakerdave]

. . . . I do have a box program, and it suggests a .835 cu ft sealed enclosure . . . .

What frequency do you get from this? I would expect it would have to be stuffed.

. . . . (why did you pull your post?) . . . .

Because I was just sharing my thinking, out loud, and was talking about a lot of stuff I had not tried.

[stevem]

I've thought about doing the same thing, but I'm not done messing about with my M9500 wannabe's and have not had the time to check out my ideas for using the 1400nd above a subwoofer.

To maintain efficiency, and to be making a box that you know will work in and of itself, I would first try the 2.8 cu ft box as in the upper chamber of the M9500, ported out the back, over a sealed subwoofer.

I guess I have a similar set up as the M9500, except it's a tower arrangement with a mid. I was using two 1401NDs per side, with one in a 2.8 cu ft section tuned to 35 Hz, and the other below it in a 4.2 cu ft section tuned to 28 Hz. I don't know if it's my room, but I have always had a problem getting nice smooth bass response out of this system. Prior to that I used these woofers in a single 8 cu foot box tuned to 30 Hz, like the DMS-1. This was way worse, yielding a thumpy kind of response.

The reason for adding the subs, is for Home Theater. I also found that by eliminating the bottom woofer, and using a sub, I get better quality sound. For a while I was using the driver in the 4.2 cu ft box as the sub, and this actually worked out better. Now I'm temporarily using a pair of 2235Hs in 5 cu ft boxes. These will be replaced with the W1500Hs. It does seem to me that the 1401ND makes a really good mid-bass driver. Part of all this is to reduce the size of all these speakers because with HT, the room is getting too crowded!

Why do you suggest a sealed sub? That's another decision I have to make because the W1500H woofer can be used either way. I don't want to put the sub under the mains because the overall height will be too high, so they're going to have to go against the back wall.

[stevem]

[quote=speakerdave;241915]What frequency do you get from this? I would expect it would have to be stuffed.

F3 is 83 Hz. It will slope downward from there at 12 db/octave. Do you think the 1401ND is suitable for use in a sealed enclosure at all?

[speakerdave]

I guess I have a similar set up as the M9500, except it's a tower arrangement with a mid. I was using two 1401NDs per side, with one in a 2.8 cu ft section tuned to 35 Hz, and the other below it in a 4.2 cu ft section tuned to 28 Hz. I don't know if it's my room, but I have always had a problem getting nice smooth bass response out of this system. Prior to that I used these woofers in a single 8 cu foot box tuned to 30 Hz, like the DMS-1. This was way worse, yielding a thumpy kind of response.

The reason for adding the subs, is for Home Theater. I also found that by eliminating the bottom woofer, and using a sub, I get better quality sound. For a while I was using the driver in the 4.2 cu ft box as the sub, and this actually worked out better. Now I'm temporarily using a pair of 2235Hs in 5 cu ft boxes. These will be replaced with the W1500Hs. It does seem to me that the 1401ND makes a really good mid-bass driver. Part of all this is to reduce the size of all these speakers because with HT, the room is getting too crowded!

Why do you suggest a sealed sub? That's another decision I have to make because the W1500H woofer can be used either way. I don't want to put the sub under the mains because the overall height will be too high, so they're going to have to go against the back wall.

The boom/thump may be coming from the room.

The lower woofer as a woofer may have been working to a frequency where you would be getting a floor bounce, whereas, as a sub, it wouldn't do that.

Also, you need to plan, in your compensation, for acoustic coupling. Putting pairs of woofers in different arrangements may couple at different frequencies and require different compensation.

I've heard the DMS-1's, and I thought they are pretty good, but I've heard they are very finicky as to set up.

A ported enclosure is a trade-off in which one of the negatives is lagging phase at the port. When you are handing off to a subwoofer, I think you will have three phases to deal with in the crossover region rather than two. That, and since you do not need the LF extension, why keep a port? Maintaining efficiency would be the only benefit, I think.

What frequency did the box program say you would get with that .6xx box?

[speakerdave]

. . . . F3 is 83 Hz. It will slope downward from there at 12 db/octave . . . .

That looks like the solution you were looking for. I think I would try that.

. . . . Do you think the 1401ND is suitable for use in a sealed enclosure at all?

Yes, if you can get what you want using it that way. I wouldn't put a lot of EQ on it.

[4313B]

I will really appreciate any comments. Thanks!

I would try everything in sealed prototype boxes first. If that didn't do it for me then I would look further into vented boxes. Run the fourteens through a software package and see what sealed volumes yield a Qt of around 0.58 to 0.80. You probably don't want a Qt lower than 0.58 or higher than 0.80 but that's your call.

The W1500H's work really well in sealed boxes, their mechanical structure is specifically designed to withstand the rigors of operating in small sealed boxes. They also work very well in ported boxes. I think I sent you the information on both.

[stevem]

I would try everything in sealed prototype boxes first. If that didn't do it for me then I would look further into vented boxes. Run the fourteens through a software package and see what sealed volumes yield a Qt of around 0.58 to 0.80. You probably don't want a Qt lower than 0.58 or higher than 0.80 but that's your call.

According to my box program, a Qt of .80 is a .497 cu ft (net) Vb, and .58 is a 1.101 cu ft (net) Vb. The program suggests a Qt of .648 with a .835 cu ft (net) Vb. Are these enclosures too small? The program seems to suggest adding .073 cu ft for the driver volume. Does that sound about right for a 14" driver?

The W1500H's work really well in sealed boxes, their mechanical structure is specifically designed to withstand the rigors of operating in small sealed boxes. They also work very well in ported boxes. I think I sent you the information on both.

You did give me the information on both. Thanks again.