10" XLS semi-finished

[Dave Jones]

Here's a picture of the 10" XLS subwoofer with 400 gram PR. Sitting on top are the FE107e speakers that we've been discussing here in other threads.

No doubt I will continue to tweak for some time yet, but lemme tell you, these already sound really good.

Tweak update: The baffle step correction circuit is now 2.75 mH and 5 Ohm. Farther away from the wall, more resistance might be needed, but as they stand, 5 seems to work very nicely. I'm trying to locate the microphone preamp to do some measurements.

The sub is overkill for the office. Probably it will go home with the Ariels. Next we are going to build a more modest sub, probably using the Apex Jr 8". Your ideas will be welcome.

[netgeek]

I like it alot! I've been looking for user comments on the XLS series and your's are encouraging. Thanks!

[Dave Jones]

Originally posted by netgeek
I like it alot! I've been looking for user comments on the XLS series and your's are encouraging. Thanks!

I've been listening for a few hours now. I LOVE IT!

If the correction charts for the Radio Shack sound level meter are to be believed, the thing is dead flat in-room down to 20Hz. It uses the Parts Express 250W amp that advertizes 6dB boost at 30Hz, BTW.

Besides music, I'm having fun with the Alan Parson "Sound Check" CD -- howitzers, locomotives, thunderstorms.

[Vikash]

What was the enclosure internal volume? Any pics of the internals?

[BAM]

...shouldn't use bass boost on ported/PR subs, only sealed subs. It's bad for both the drivers and radiators.

[Ron E]

Originally posted by BAM
...shouldn't use bass boost on ported/PR subs, only sealed subs. It's bad for both the drivers and radiators.

It doesn't matter a whole lot if the boost is above the tuning frequency, although preferably the boost is AT the tuning frequency, then you can make a 6th order alignment. The PE boosted amps also cut everything below boost, and thus actually protect the drivers....

[Dave Jones]

Originally posted by Vikash
What was the enclosure internal volume? Any pics of the internals?

I didn't take pictures of the inside. Perhaps I will open it up tonight and take some pics. There's not much to see though. All panels are 1" MDF.

Internal dimensions are 11" W, 24" H, 6.75 D, for a gross internal volume of 1782 in^3 = 1.03 ft^3 = 29 liter.

[What I wanted was a sub that was of a suitable size and shape to serve as a speaker stand for the "bookshelf" size mains.]

From the 29 liters, subtract some unknown amount for the driver, amp, PR, and a shelf brace. The brace is 1" MDF with several circular holes cut in it. I would guess that the effective internal volume is around 24 liters. But then, I've got almost one full panel of Parts Express egg crate foam in it (p.n. 260-516). Perhaps that will increase the effective volume. Maybe I should put some solid filler in it to decrease the internal volume? Maybe I should remove some or all of the foam?

Everyone please understand, I do not claim this is a great design. The only measurements I've done were using a Radio Shack sound level meter and correction table from the internet. The thing is, I studied and asked questions on this BB for months and months. It finally occured to me that I was never going to come up with a design that both suited me, and that no one could find fault with. Before I built this unit, I modeled it using a box size of 26 liters, and smaller sizes down to 21 liters, all using the same 400 gram passive radiator. None of them appeared to be too horrible, so I figured there was some room for error. Just in case, I got an amp with EQ that can be modified if necessary.

I'm quite happy with it right now, but I'm sure someone will point out to me just how badly I've screwed up, and then I'll have to start over. :-)

[Dave Jones]

Originally posted by BAM
...shouldn't use bass boost on ported/PR subs, only sealed subs. It's bad for both the drivers and radiators.

Originally posted by Ron E



It doesn't matter a whole lot if the boost is above the tuning frequency, although preferably the boost is AT the tuning frequency, then you can make a 6th order alignment. The PE boosted amps also cut everything below boost, and thus actually protect the drivers....

The tuning frequency is well below 30Hz - around 20 if memory serves. I am not at all concerned about damaging the driver or PR. Even if there were no subsonic filter, I would not be playing it nearly that loud anyway. XLS stands for "xtra long stroke" doncha know?

[Dave Jones]

Here's what I was going for. The chart below shows SPL down 8 or 9 dB at 30Hz. I figured that with 6dB boost at 30Hz, room gain should lift it enough. Also, I am really only interested in how the low frequencies compare to 70 or 80 Hz, where the sub will be crossed over.

In practice, things seem to have worked out just about right.