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Four SI HST18's Build

21K views 328 replies 55 participants last post by  EndersShadow 
#1 ·
I made a major speaker upgrade recently and in order to help offset some of the (unexpected) costs, decided to sell my very much loved Seaton SubMersives (4 of them) and try DIY.

While I had 4 SubMersives, 3 is more than adequate (in fact, two are and is what I started with) but my OCDness would not allow the required asymmetrical subwoofer placement. The original room I had the SubMersives in was in a concrete basement. I am now in a converted loft on the 2nd floor so I am limited by my concerns over structural integrity of the room/house on how much woofage I dare put in this space.

A fellow AVSer (CraigJohn) in whose ears I trust and also a SubMersive owner, had heard some DIY subs done by Gorilla88 and in Craig's words, those DIY subs "killed" his SubMersives. At the time, Gorilla88 had, if I recall correctly, 6 or 8 of the SI HT18's running so that is the direction I started in.

To reduce the space requirements of that many cabinets, I then decided to try to find a dual-opposed cabinet utilizing SI HT18's but the availability of those cabinets did not meet my time requirements.

So back to single 18 inch enclosure and have ordered 4 of the flat packs from Parts Express. Given the reduction in the number of cabinets (from the 6 to 8 that Craig heard at Gorilla88's), I have ordered 4 of the SI HST18's (vs HT18's) and will see how they perform vs my needs/wants and previous experience with my SubMersives). If those 4 turn out to fall short, I will just keep adding boxes until I get there. Sound is such a personal preference thing, and while I have received all kinds of opinions, I thought I would start "small" and add as necessary. I am cautiously optimistic that these 4 will do the job. (My room is about 3400cf).

Pieces I need to get up and running:

Drivers: 4 HST18's (D2) on the way

Amps: I have two Peavey 7500's on the way. I plan on running the HST's at 4 ohms so one amp in 4 ohm mode will drive 2 cabinets

DSP: I have a miniDSP in house

Cabinets: 4 On the way

Paint: 2 Gallons of Duratex and 4 rollers are on the way

Glue: Titebond II in house

Clamps: Going to Harbor Freight Tools this weekend (we live in a very small community) to buy a bunch: How long does it take for these cabinets to dry enough so that I can remove the clamps and glue the next cabinet.

Spackle: The folks from Acrytech who make Duratex recommended Ace Hardware Vinyl Spackle so will find an Ace Hardware when we make our trip this weekend.

Connectors: It has been recommended that I use Neutrik speakON connectors. I still need to research this and also determine what kind of connector the amps use.

Lastly, screws/connectors/fasteners for the drivers to connect to the enclosure. It has been recommended to use PE's Hurricane nuts + hex socket screws so I will investigate those as well.

If I have left anything out (a real possibility) I would appreciate any feedback.

I have no doubt that I will eventually get these all constructed (I have about 4 weeks until my 4 SubMersives leave the premises). But most importantly, I am anxious to see what kind of FR I am able to achieve. The FR from my current subs in their current locations is ruler flat being down about 5db at 7hz.



I am looking to meet that AND have the same sound quality/impact.

We shall see.

Thanks
 
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#2 ·
The mounting depth on the HST18 is 11" and if the PE flat pack is spec'ed the same as the 4cf flat pack at DIYSG, you will need to modify the internal bracing to accept the 11" depth of the driver. I would do a dry fit of the box and measure the depth to double check if you have enough clearance. :)
 
#3 ·
Ooops !! It is the exact same product.
 
#6 ·
Titebond II says 30 minutes clamp and 24hrs before loading the joint. Considering the total weight of the enclosure some of the joints will be loaded simply by removing the clamps, so err on the side of caution, but I'd feel safe in unclamping after a few hrs.

I have been using the square metal speakon jacks, but just ordered some of the rounds as well. Looking at the spade terminals on the back and the connections in the jack I would use the square metal ones for this build. They are quite a bit more robust in connection terminals.



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#28 · (Edited)
I have been using the square metal speakon jacks, but just ordered some of the rounds as well. Looking at the spade terminals on the back and the connections in the jack I would use the square metal ones for this build. They are quite a bit more robust in connection terminals.
Yet another "Newbie question" What is the difference between the 2 and 4 pole connector types? A speaker wire has a positive and negative.

Is the wire connection screw on or soldered?
 
#7 ·
Also. I saw someone looking for the correct size screw for the speakons- in irder to get a flush/clean look- you can see in the pics that the M3 bolts I use make the grade, but I am putting a washer and but on the inside which is a bit more work than most would prefer- I just don't like coarse thread screws in MDF. Probably due to so much exploding Walmart/ikea furniture in my younger years.


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#8 ·
Also. I saw someone looking for the correct size screw for the speakons- in irder to get a flush/clean look- you can see in the pics that the M3 bolts I use make the grade, but I am putting a washer and but on the inside which is a bit more work than most would prefer- I just don't like coarse thread screws in MDF. Probably due to so much exploding Walmart/ikea furniture in my younger years.
Do you have a source you can share for those bolts? Those are nice!
 
#12 ·
Yea, audyssey sucks for bass eq. It is a good idea to run all subs on the same output because you can set delays with your dsp and let audyssey or whatever other room correction software tune the subs collectively. I too like to tune the subs before room correction software is run, so that it has less work to do and your sub baseline tune will always be there if you were to ever need to run the room correction software again for whatever reason.
 
#14 ·
"sucks" may be a bit strong but for multiple subs not equal distance from the MLP, it never seems to get it right. The other key issue I have with Audyssey is the sub 20hz output. Audyssey claims it corrects down to 10hz but in my case, I can easily prove the it screws up the bass below 20hz.

Maybe "sucks" is the right word :D
 
#13 ·
4 Boxes delivered today. Note the directions of the arrows. Apparently UPS wasn't sure what an arrow meant !!



Blue tape to see how it all goes together.





Is there any reason that I should not apply glue and then use a brad-nailer to skip the clamping step? I can set the air compressor to set the head just below the surface and the paint I'm using should certainly hide any tiny holes. It sure would save a fair amount of time. I would glue/nail the front piece on but glue only the beveled piece and use weights to hold it in place.
 
#17 ·
...Is there any reason that I should not apply glue and then use a brad-nailer to skip the clamping step? ...
I don't believe nailing tightens the joint as much. I would clamp (to compress the glue and tighten the joint) then nail. Once nailed, move the clamp to another position, repeat.
 
#19 ·
Good luck w/your build. I'm looking forward to pics and your impressions of four of these bad boys.

Also wanted to add that the discussion of Audessey/MiniDSP/how many channels of sub to run is very interesting to me. In a few months I'll be setting up my new HT and using Audessey XT32 for the first time. I already bought a MiniDSP specifically for the subs. Guess I have a bunch of reading to do in advance.

Good luck w/the build!
 
#25 ·
When PE got in the 18" Ultimax I increased the cut out about 1/16" to allow for that woofer and the original RS-18. I think I might have also taken the internal braces back about 1/2" because the Ultimax was deeper than the RS-18.

I'm curious to know if the Stereo Integrity will fit the same box when you remove the black plastic ring from it's frame.



I put those arrow stickers on the box because the thick corner protectors are on the bottom. Whenever I saw pictures posted of flat packs shipped from PE they were somehow always being shipped upside down. Maybe PE takes them off the pallet and flips them over onto the conveyor, I wasn't sure. So I put the arrows on so that PE would put the shipping labels on the top....figuring UPS had to have it face up to scan the labels. I know the shipping companies don't care at all about arrows or 'fragile' stickers. :rolleyes:
 
#26 ·
8 15's vs 4 18's is a bit unfair to the 18's, also the Seaton's have more power/heat handling.
If 4 HST's don't do it, 6 surely will!
Probably only a basshead would care, but this is AVS, so...
 
#27 ·
It may be unfair, but the beauty of doing single cabinets is that I can add them one at a time until I get what I need (want !!). And as I noted previously, I really didn't need 4 SubMersives but only had them (in my previous theater) to provide a symmetrical room (how sick is that?). All other things being equal (they aren't), an 18 has about 1.4 times the radiating area of a 15 so 5 HST's is not quite enough and 6 is too many. I'm thinking that 3 SubMersives would have been enough which means 4 HST's will be very close. But we shall see.

Also, the SubMersive HP amps are 2400 watts for the two drivers and I will be providing about 4000 watts for two drivers. I don't know the efficiency of the modified Eminence drivers that Mark uses.

But, I should know soon enough. And as I have also noted previously, had my room been in a basement instead of on the 2nd floor, I would have ordered 8 HST's. In a basement, there is no such thing as too much woofage!! In a loft, unless one is interested in relocating the theater down one floor, that is not the case!

It has also been suggested to me that the HST is equal to more than one HT in some ways. Who knows!!
 
#29 ·
4-pole has two sets of positive and negative inside the connector. You don't have to use both though. It just gives you that extra flexibility if you need it.

For example: I run a single cable with four wires (instead of two) to my midrange/HF section of my mains. Let's me route those two independent signals through one cable for my active mains. Just one less cable and connection to deal with in an overly complicated setup. :p
 
#30 ·
Thanks. Got it. Do you solder the wire or use a screw terminal or add a spade terminal or .....?
 
#32 ·
Do you remember the specific model?

I REALLY appreciate your help by the way. Thank you so much. Traveling new audio waters without folks like you and many others at AVS would be scary thing!! Thanks again.
 
#37 ·
All ordered. Thanks. Do you use any kind of special screws/bolts to fasten the one that goes on the cabinet?
 
#38 ·
Yet another few questions:

(1) What is the trick to lowering a 70 pound driver into the opening and then being able to rotate it so the holes in the basket line up with the pre-drilled holes/fasteners?

(2) In order to use the HST 18 in this enclosure, I have been led to believe that the rubber gasket that comes on the driver will need to be removed. Given that, and from previous speakers I have built, I was going to use Rope Caulk. I've not used this particular brand but they are all pretty much alike. Is there any reason one can think of why this is a bad idea? If never hardens and while it creates a great seal, does not make it impossible to remove the driver. Any other gasket/sealer recommendations?

(3) Do most folks just screw the driver into the cabinet or use some kind of other fastening technique? Any recommendations?

Thanks again in advance.
 
#42 ·
1) It's a challenge. If you're using threaded inserts (see #3 ) you can put threaded rods in a few of the the inserts and use those rods to guide the driver down. Then unthread the rods and replace them with your mounting screws.

2) Myself, I like to leave the rubber gasket on. I've found it adequately seals the driver to the box if the box has a smooth and reasonably hard finish on the mounting surface. I used rope caulk once before, and will never use it again. It might as well be glue. If you're recessing the driver it will be virtually impossible to get out. I had a surface mounted driver and had to pound a putty knife between the frame and the box and work my way around the driver prying and gradually tilting the driver. With a recessed driver the method I had to resort to for removal would be impossible. Speaker gasket tape from PE or an equivalent would be my suggestion.

3) I like to use some sort of threaded insert in the wood. I've used the barbed inserts from PE and hurricane nuts from PE before. For my next sub build I plan to use these.
 
#40 ·
#44 · (Edited)
If you have to mod the box to the right depth for the driver, it might be worth using a router to make the outer baffle hole a little bigger to fit the gasket. It looks nice and seals nice. I used it to move/lower my ht18 into place. Once close to the screw holes use a screw driver to do the final alignment of the sub to the bolt holes. I used 1/4-20 tnuts as you can see in my build thread in my sig. I tighten with a criss cross pattern like you would a car rim to ensure even pressure and to avoid warping the drivers basket.
 
#48 · (Edited)
I just noticed something odd. on the Flatpack, he distance from the two smaller internal braces to their respective top bottom piece is different: one is about 6 7/8 inches and the other is about 7 3/16 inches. Not that it makes any difference but does anyone know why?

Clamping practice session:



I decided to practice the best way to use the 8 clamps I have. Glad I did, because had I done this on a real deal, the glue would have probably already dried by the time I got it figured out.
 
#60 ·
I have 2 Peavey amps to drive these subs and am looking for a way to auto power on and off but the amps don,'t have 12 volt. Recommendations?
 
#63 ·
I'm going to go with the electromechanical on my next amp or three. I did an SSR inside an iNuke case and thermal pasted it to the chassis but an SSR is really the wrong tool for this job, they're great when you need to switch on and off hundreds or thousands of times a day- think turning a heater coil on and off to stay within a defined range- but we only need to switch once or twice a day, so the mechanical is probably better considering it doesn't reduce output or expend heat. There is just the concern of transient voltage spikes which are easily shunted.

The cool thing is they both work-


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#65 ·
Drilling a perfectly vertical hole is difficiult but mandatory for proper installation of the driver so I found this thing:



Coupled with a clamp, I should be able to get the holes vertical. The plan is to drill a small starter hole by hand in the center of the area marked by using the driver as a template and then using this combination to insure I get the desired results.

 
#67 ·
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