Dipole Bass Recomendations

[outfoxhyperion]

Hi All,
First time posting, so I wasn't really sure where to put this thread but this seemed like a good place. I'm building a pair of speakers and I'm planning on doing some sort of dipole design to make the most of the drivers I've ordered. I'm not tied to any specific design, but the drivers are set. I've included a link to them at the bottom. My biggest goal is to get the cleanest bass I can down to 40 Hz or below. It had been suggested elsewhere that I do a ripol design, but the forum I was asking the question on doesn't seem to have a lot of people with expertise in dipolar designs like this one does. I'm going to use an active crossover with a dedicated amp per side, so power shouldn't be an issue. The biggest limitation for this is footprint, I'd like to limit the footprint to less than 24"x18" if possible. I'm open to any suggestions, so fire away.

Thanks in advance!

Titan 10" Black Glitter Cone Foam Surround Woofer 4 Ohm

[Octavia]

take a look at H frame designs, and don't expect miracles from that driver no matter what you choose to do

[outfoxhyperion]

I had actually initially looked at a design similar to the Hestia H-Bombs for these, but the reason the ripol style was suggested was the mechanical loading of the drivers and the reduced Fs, the mechanical loading being especially important due to the limited xmax of these drivers. That being said, I did a trial with one of these in a simple 24"x24" XPS baffle and they seemed to do alright. I didn't have any kind of low-pass on them though, so it's hard to tell for sure. I should also mention: I do not have a 2 ohm safe amp, so these will have to be in series for each channel.

[CharlieLaub]

In terms of suitability for dipole use the Titan driver has a couple of things going for it and a few against it as well. It has a modestly low Fs of 45 Hz. This will not be very good in a planar baffle. Instead put it in an H-frame. The additional air load will both cause Fs to drop a bit, and Qts will increase a little bit. Teh free-air Qts at 1.06 is favorable for dipole use. On the down side, a 4mm Xmax is rather low for bass duty. A 10" will not move much air - the requirements are more demanding than for e.g. a sealed box. The driver is pretty cheap, so you could make a pretty good 24"x24" H-frame, 24" deep and use FOUR of them. Reverse the mounting direction of 2 of the 4 to get even order harmonics to cancel. Do not expect great performance, e.g. distortion performance, and the TS parameters provided by PE might be way off. These things matter for good sounding bass. What do you expect for $10?

[outfoxhyperion]

Thanks Charlie, that's very useful information. You're right about the PE T/S parameters, they're frequently pretty far off for the buyout drivers, or just missing entirely. I may have failed to specify, but these are going to be the bottom half of a two-way system with DML panels for everything form 200 Hz up. So they're going to be two per channel, in stereo. In that situation for an H-Frame would it still make sense to reverse the mounting direction of one per channel? I've also considered using a more typical Linkwitz W-Frame, would these be suitable for that?

[puppet]

Been thinking about this lately. Maybe an idea for you. You'd need three panels 12"x30" for instance. Mount the drivers on one of the panels near top and bottom. You'd mount them balanced. The other two panels serve as sides to the enclosure. Close off half of the front and back making two chambers, one each side, creating the dipole response. You would cover the top and bottom of each open chamber leaving a section open at the center. You could experiment with how open the center might want to be by trail and error.
The chambers might boost lower end response with that small amount of compression.

[CharlieLaub]

Originally Posted by outfoxhyperion

Thanks Charlie, that's very useful information. You're right about the PE T/S parameters, they're frequently pretty far off for the buyout drivers, or just missing entirely. I may have failed to specify, but these are going to be the bottom half of a two-way system with DML panels for everything form 200 Hz up. So they're going to be two per channel, in stereo. In that situation for an H-Frame would it still make sense to reverse the mounting direction of one per channel? I've also considered using a more typical Linkwitz W-Frame, would these be suitable for that?

A shallow H-frame will work for you, or the W-frame. They are about the same really, with the W-frame having a little better vibration cancellation and slightly reduced line resonance. I would indeed reverse one driver to cancel some distortion products. You can always start with the Titan drivers and then replace them with a higher quality 10", like the Peerless SLS 830668. But of course the driver TS parameters will then be different so the EQ of the low end will have to be adjusted.

[outfoxhyperion]

What are good ballpark sizes for the baffles for these? I'll be able to build and test one of them tomorrow to get an idea of performance. Also, logistically it's better to be able to build these from lumber that's 11.75"x48" or less, as that's the cheapest way for me to buy MDF.

[bentoronto]

There's matching sounds of sub and mains (don't believe in it myself) and then there's matching owners taste.

As much as I like electrostatic dipoles, the cleanest sub sound (short of enormous true corner horns) will be a sealed box and esp since you have no ambition to get to sub-sonic freqs. You only need one, of course.

With a no-box "suspension", your cone will be unconstrained. With a sealed box, it will be constrained and also will have an element of degenerative feedback from the air compression.

Also you can locate the box anywhere and use any shape. But dipoles take some care in location and adjacent furnishings.

B.

[outfoxhyperion]

Well, sealed box was the original plan, but when I did some modeling and had some of the good folks at the PE tech talk forum check my numbers, the required volume to get the kind of performance I was looking for was enormous (like 28 ft3 per driver), and I just don't have that kind of space in my living room. So footprint is one of the big things that drew me to the ripol/W frame in the first place. Plus, the DML panels have kinda gotten me addicted to dipolar bass... I do appreciate the feedback, though. Who knows, if they don't perform like I hope in the W frames or double H's, they may be relegated to replacing the aging Sony bundle bass reflex/amp combo living in my shop.