[kryptonitewhite]

I am just now starting to research IB, I know my questions are here...but it's going to take days just to get started, and I will be searching... But I'd like to get a few questions answered right away.

What does a general IB FR response curve look like? I have WinISD but IDK if this is even an option.

What are power requirements compared to large sealed and vented enclosures. ( I don't want to list which specific drivers, but I know I will get asked anyway, so be it then... say the Fi 18" IB driver, Maelstrom-X's, Tumults, Avalanches....)

Is it 10X Vas to be a true IB?

How does Di-pole and bi-pole compare?

Any other interesting or important facts? Everything neat and exceptional about IB I'd like to know.

Thanks!

 

[kryptonitewhite]

Also, I was reading this post by Scott in the Welcome thread to Fi. He talks about power required to get full excursion @ 20Hz. What if you are aiming for 10Hz or lower.... do you have to EQ? Or do you give less power, therefor you get full excursion at 10Hz or 8Hz or whatever your number, and you just dont have as much gain at that 20Hz?

Thanks!

Thanks for the welcome

As far as what we can do for the drivers, for the SSD and Q line we have been doing many IB setups. The changes are to the suspension (being softer), the coil (usually customers want a single coil in 2 or 4 Ohm for ease of wiring), and machining the gaps a little wider to adjust the Qts.

For standard HT use, we can soften the suspension a little (since most are setup for car use in the first place) depending on power, enclosure size, and tuning. Use a different dustcap to increase or decrease moving mass vs the standard version. And more recently for the 18" drivers (which seem to be the most popular sellers) use a new cone/compound that decreases moving mass by about 70 grams over the standard cone.

I am currently testing 2 new IB specific subs. First is a 15" with good efficiency, low Fs, 24mm of Xmax (suspension limited), and approx 300W rating (to get to Xmax at 20Hz). The second is a new 18" the uses a smaller, tighter motor than the Q, a 2 layer coil, 30mm of Xmax, lighter new cone, 600W rating (to get to Xmax at 20Hz). Both will have very reasonable price points, and will have special HTS pricing.

I am also doing a few more tweaks to the Q series with a different single 4 Ohm 2 layer copper coil (most of our subs use aluminum coils) that has simialr specs to the standard version, but a lower qts.

We are constantly tinkering and trying new things. When something seems useful, we will post it up. Ill be working on some stickies for the forum over the next few weeks for what HT specific tweaks and subs we have available.

Thanks,
Scott

 

[tenzip]

I'll try to answer a couple of your questions.

On the frequency response, the nearfield response looks a lot like the response as modeled in WinISD Pro with as big a sealed box as it will let you have. The response at your listening position will depend on your room. You can get an idea of what it will look like by putting a box sub where you intend to put the IB opening, and then measuring/listening at your normal LP.

I believe that a "true" IB would need to be approximately 25x Vas, but the difference between 10 and 25x is so small as to be not worth worrying about.

I don't understand your question about Di- and Bi-pole. Are you asking about the difference between manifold and line array mounting?

 

[Mike P.]

What does a general IB FR response curve look like? I have WinISD but IDK if this is even an option.

Model the sub in a sealed box and change the box size to 10 times the Vas.

What are power requirements compared to large sealed and vented enclosures.

It takes less power for a sub to reach its Xmax in a IB configuration compared to sealed and ported.

Is it 10X Vas to be a true IB?

Yes.

How does Di-pole and bi-pole compare?

If I understand di-pole and bi-pole correctly, they will both have less low end output due to cancellation issues.

Any other interesting or important facts? Everything neat and exceptional about IB I'd like to know.

Good points - anyone who has one say it's the best sound.

Not so good points - determining the proper location for the install can be a challenge.

 

[kryptonitewhite]

line array mounting?

Thank you, very informative... and I went back and read the what is an IB thread after my post...bass ackwards...

what is array?

 

[kryptonitewhite]

If I understand di-pole and bi-pole correctly, they will both have less low end output due to cancellation issues.

why would anyone use these then?

 

[thxgoon]

What does a general IB FR response curve look like? I have WinISD but IDK if this is even an option

For IB the response curve of the system will be the same as the response curve of the driver due to the lack of airspring or port assistance. It will have less maximum output than a vented design but the same as a sealed design using the same drivers and will reach that output with less power. EQ will be less necessary than with a sealed design but is a good idea for compensation of room related anomalies.

How does Di-pole and bi-pole compare?

I've never heard of a bi-pole subwoofer design but the definition would be two drivers firing in to the room in the same phase but pointing opposite directions. At the frequencies of subwoofers it would create no difference in sound. You can pretty much orient the drivers anyway you want and they will sound the same. A lot of people like to build their drivers opposite each other in a manifold to reduce resonance in the wall they mount the IB in.

Dipole design for subwoofers is not a good idea. You will gain nothing over an IB but lose a ton of output.

Any other interesting or important facts? Everything neat and exceptional about IB I'd like to know.

Make sure you know where you are putting it is a good location. Once it is installed it's not easy to move. Place a subwoofer in the intended location and take some measurements with REW at your listening position to make sure you are not in a huge null that will suck out all of your bass.

Oh.. and make sure you post your build :bigsmile:

 

[thxgoon]

what is array?

An array is a series of drivers mounted close to each other. Leads to higher sensitivity and high output.

why would anyone use these then?

Dipoles were useful in the days of pro logic for surround sound as they diffused the field and made localization of the speakers less easy. The result was a surround 'field' instead of a mono headphone like surround channel. Today some audiophiles swear by them because the drivers are free to move as they wish without being confined by the air spring in a box. At mid to high frequencies this can work fine and the back wave can add to the ambience of the sound. Because the wavelengths of subwoofer signals are so long, the back wave ends up canceling the front wave and a huge reduction of output is the result.

Bipoles were made popular by Definitive and Mirage for creating more in room ambiance, but in the case of subwoofers the wavelengths are too long to make any difference.