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Taming the HS-24

45K views 401 replies 79 participants last post by  Sibuna 
#1 · (Edited)
Taming the HS24

EDIT: Jump to this post for the start of the final chapter. And straight to this post for the completed pics.
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It's time for a winter project.

I am thinking to replace my 2 sealed 18-D2's with a pair of Nick's HS24's. The target volume is 15 cubic feet per cabinet. I am trying to constrain the width and depth by building upward.

My current design is outlined below, with renders showing the structure of the bracing.

48x26.5x26.5
15.224 cubic ft (before the driver)
190 lbs (before the driver)
Triple 3/4" baffle, with single 3/4" wall elsewhere
All panels braced no less than every 7 inches
Interlocking braces
Rabbet joints all around

Before I start making dust, I want hear some thoughts on the adequacy of the cabinet's mass to tame this beastly driver. In Ricci's review of the driver, he mentioned excessive shaking of his heavy test stand. One other (can't remember where) suggested bolting his cabinet to the floor would be helpful. Sibuna's cabinet showed some tremoring

Give me some feedback.

If I used 1" MDF for the walls, assuming the same external dimensions, that would bring my unloaded weight to 222 lbs. I have access to that material, but I don't want to add the weight if it isn't necessary.

THOUGHTS?



 
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#6 ·
#9 ·
Much of the rocking from the test was the result of the lever created by suspending it that way. It will rock much less in a large cabinet with a lower center of gravity. There will still be vibration, but nothing like the test scenario.
 
#20 ·
Before I start making dust, I want hear some thoughts on the adequacy of the cabinet's mass to tame this beastly driver. In Ricci's review of the driver, he mentioned excessive shaking of his heavy test stand. One other (can't remember where) suggested bolting his cabinet to the floor would be helpful. Sibuna's cabinet showed some tremoring.
Ricci said, "At around 3” peak to peak the driver seemed in little danger and still had some clearance before the cone contacted the spider spacer on the inward portion of stroke. By this point the surround was starting to dimple visibly. An unforeseen issue was that at this much excursion my entire test stand which probably weighs 250-300lbs unloaded was starting to shake violently."

1. 3" peak to peak is past X-Max
2. How much power will you have available?
3. Using two drivers with enough power to get to 3" peak to peak means that most likely you would need to be listening at 6 dB louder than one driver :eek:
4. I bet that 99% of the time your drivers will be under 12mm of excursion
5. Nice renderings :cool:
 
#21 · (Edited)
Reasonable points and questions, Michael.

I will be power limited to start with. I'll be using my NU6K until the need and means align to add more power. With that amp I think I can briefly squeeze out 2.45kW with one channel and 2.05kW with both channels. At 2.45kW, xMax is met at 4.5hz. At 2.05kW it is 3.3hz. With signal chain rolloff I'll probably never get there. But I still think I should be considering the influence of the moving mass on the cabinet.

I know that @Bill Fitzmaurice often talks about using 1/2" ply with intelligent bracing to keep cabinets light and sturdy, but I don't think any amount of bracing will keep a box from shaking if it doesn't have enough mass when using a driver like this. Maybe he will chime in.

I want to plan for someday having another circuit and a clone, even if that isn't in my short term plans. Half the fun for me is in designing the cabinet - and sometimes that means solving problems that beyond reality's horizon. This may be one of those cases.:D
 
#24 ·
I personally couldn't imagine putting it in a box like the OP wants, unless it was with the driver right at the bottom and had an extra 100lbs of mass added somehow..... or it was made out of 1" MDF double sided with ply mounting. pretty much 2 boxes in one if it's gonna sit tall. It would be close to 400lbs with driver lol. But it wouldn't be moving!!!

My FTW 21's are in 24" cubes and are 217lbs per box (with driver), even they, without the other boxes on top, will wiggle around but I didn't want to have too big of a box and they are center mounted, I could imagine the 24" in even double that, not walking across the floor lol
 
#29 ·
Thanks for the feedback, everyone. I have incorporated the center of gravity idea from @notnyt, and the use of the upper baffle space for a design element from @antisuck. That may or may not happen... it would take a lot of machine time to execute that elegantly.

I also beefed up the bracing a little bit more.

Internal volume is now 15.1249
Dry weight increased by 5 lbs from the bracing changes, and another 10 or so from the "ripple" face. Final unloaded weight is 204.5lbs.

Toying with grille options as well.


 
#31 ·
Ripples are way cool, can't wait to see those come to life.

Last time I had to place a DIY sub on a hard surface I placed some space dynamat on the bottom of the cabinet and cut it 1/2 short from the edges so it was not visible. That thin layer of dynamat on the bottom was enough to to keep the cabinet from walking around.
 
#35 · (Edited)
I might be biting off more than I can chew with this, but I've grown the ripples to continue around the sides and top of the box. This is with a 2nd layer of material on all sides except the bottom, at the moment. The rear will just have a flat second layer. This of course will increase mass, and remove the doubts I've had about single wall construction.

This brings the unloaded all-MDF weight to 288 lbs. I might ditch what was originally the outer baffle layer, shaving a little more than 20 lbs off that number.

Each panel will require multiple hours of machining to get to a sandable finish. Executing it properly will take some head scratching I'm sure, but I think it would look very cool if done well. But I reserve the right to scrap the idea altogether if sense gets the better of me. :grin:

The ripples have a constant amplitude - from just under surface level, to 1/2" deep. The plotpoints grow by an arbitrary and steady function of 1.15 the diameter of the previous. All concentric with the driver.

I'm going to order some material to replenish my stock, since this will use most of what I have around. Is the consensus that plywood bracing is preferable over MDF?


 
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