[quote author=Bob  link=1145573673/120#134 date=1148058139]

Well Adrian, That seems pretty obvious now that I see it in writing. I'm fairly dissapointed, and embarassed in myself for not realizing that. Several hundred watts at 100hz is much easier than at 25hz. Thanks for the reality check. That's why you received that A- !

Bob [/quote]
rotfl, i've topped my previous scores on all exams this year. i couldn't believe it.
hmm, i never applied anything i learnt in school, except maths

60, Good bass from a couple of used 15"ers outside is different from <20hz in a movie soundtrack though, don't ya think?  I'll never say the HWK doesn't crank. Ever. It'll knock your socks off with a good source for music, no doubt about it. Steve has a helluva design there.

It just won't go low enough, loud enough on movie soundtracks for psycho's like me.

The IB thing was a passing thought/daydream. Not something I had my heart set on.

I do know the difference between a Ferrari and a Yugo, but I've seen too many 'hotrodders' that can build a rod that would keep the Ferrari looking nervously in the mirrors for a fraction the price. (That's where I want to be, I'm just having a hard time getting there.)  :)

Bob

bob...and john,
forgive me for flogging a dead horse but, if bobs drivers are bottoming out, doesnt that mean they have reached the end of their capability, and to get 'more' you either need more drivers or a 'better' driver? bob have you tried just a straight sealed box? apparently the roll of down low is 'best' in a sealed enclosure, also the subs might be able to handle more power? just a thought. personally i would have thought a pair of daytons and 900 watts would be more than adequate for watching a movie? cant imagine what your trying to achieve tyranosaurus rex @ realistic levels would require a 30 ton creature jumping up and down outside your door.i wont comment further, john is way more qualified to asist you than i am. but i do believe some of the 'hype' those beastly subs sure do pack some punch.

Bob's drivers are fine.  The HWK is not a LFE sub.

The HWK design ports at higher frequencies for the CLUB bass its meant to be used for.  Below these frequencies the enclosure does little to curve the driver's movements.  Hence the bottoming out.

Those DD audio subs will nto work for HT, a FS of 32Hz makes them unusable for sub-bass frequencies.

The Rlp subs might work, but again I do not believe in their SQ.

So John is absolutely right in sticking with your series 2 woofers.  They have a low Fs and a decent power handling.  Not that Power is that much these days.  Linear throw is what will determine the viability of any woofer for sub bass frequencies, 2 15s with 12 mm xmax or 24 mm of travel will move plenty of air.

With that said, John is again right in his thinking.  I just differ slightly in that I believe you need to get out of the moding HWK scene and start over.  There are many different options to explore:

~Low Tuned Horns - Although Huge they are my favorite type of Bass
~Transmission Lines - The main objective of these enclosures are as "Bass Enhancing devices."
~Low Tuned Large Boxes (Notice "boxeS"  Stereo subs for better room node excitiation.)


I think Bob really needs to step away from the ISO config though.  HT is all about air movement, ISO halves his capability when compared to 2 seperate 15s.  The only gain being a smaller enclosure and decrease in even order distortion due to suspension non linearities (Which I suspect these daytons have few to begin with).

Responses range from narrow bandwidth to wide bandwidth with typical responses down to 13 HZ on all three models. Box can be built for 8's,10's, 12's, 15's or 18 inch woofers.  Note: The design is for a 15, however the the box can be scaled down (and so the performance) to smaller drivers but you will have to specifically tune anything below the original 15" design.
Using musical instrument woofers (ex. PEAVEY BLACK WIDOW) you get tight full accurate bass from 200 down to 40 HZ. Using subwoofers you get big warm full bass that can on command create Subsonic pressures lower than 20 cycles.  


thats a quote from decwares hwk page. i believe the hwk IS able to produce very serious low bass.how much lower than 13 hz do we want to go?

60, If I understand correctly, drivers (cone travel distance) can be controlled by how much air is allowed in and out of the enclosure.

Playing with airflow restriction is a form of "brakes"/"shocks" for the drivers, changing the max cone travel.

So if this is true, to continue the automotive analogy, it would be like antilock brakes, or traction control. The system allows life to happen "as it will", until it see's something it doesn't like, then it interveens [sp] and reigns it back in just before bad things happen (tires lock up, tires spin, driver/cone bottoms out)

.....or, this could be complete bullshit. Please correct me if I'm wrong.  

Bob

I don't have any means of measuring hz, but this thing is not getting NEAR that low. I've played sweeps a few months ago from 150hz, down to, ummm..... 20?.. 25???
Sweep, or more like 'steps' when one hz at a time. They trailed off badly, almost got QUIET below,.... umm, 40hz? Just about the time things started getting GOOOOODDD.


Bob

(I believe my ears)

I need to run the sweeps again, just for 'grins'.

60,

I appreciate your enthusiasm, but the HWK is not at HT sub.  In the good sounding aligment making use of the big iso chamber, the upper chamber (lowest tuned one) of the 15" version of the normal HWK is tuned to about 45hz.  If you put the driver(s) in the bottom baffle only (unbalanced sounding IME), the top is only tuned to about 35hz.  The alignment definitely allows for extension below port tuning, but none of the driver arrangements are going to give any kind of significant performance in the teens no matter what driver you put in them.  The HWK is for music.

With Bob's current configuration, the big chamber is tuned to about 19hz, and with the magnet in the top chamber and the cap on, it is tuned to about 47hz.  Bob, now that I've put the calculator to it, you should test the SQ and limits like this, call it the HWK-HT.  If you want to try 15hz tuning, you need to add another 10" to that 13.5" port OR you could leave the vent the same and mount the drivers as the top cap (14-16hz tuning).

Bob, if you can make the 6th order bandpass (ports top and bottom) work for you SQ and extension wise, that's probably your best easy thing to do, since the top chamber helps control excursion below tuning better than the ported alignment (driver open to the room).  

Put the top cap back on and try to integrate it with your mains and play some of those LFE tracks.  You may have gotten lucky and be done for now, at least until you build some new mains.