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Discussion Starter · #1 ·
Hi guys,

I've been on here reading this week and have been getting myself wondering about a diy setup versus my current dual PSA xv15's?!?!. I LOVE my current subs.. and I'm rather certain that they are providing me with reference level playback on all but the very lowest frequencies. However, I can help but think a dual sonotube setup with decent 18" drivers and a Behringer ep4000.. might be able to give me more!?!?! I read somewhere two of the si 18's could be compared to a submersive???? I want dual submersive output!!!!!?!! Imax... please let me know what you guys think?!?!? Maybe more expensive drivers drivers and two ep4000's or 4 of the si drivers (2 sealed in each end of the sonotube)... just want to CRUSH my xv15's.... If im going to do it... and i have to do it for less than I've spent on the xv15's for my wife to not kill me....!!!!! Any help is greatly appreciated! !!!!!!!
 

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Discussion Starter · #2 ·
Looking like i can grab the amp for around $350, and two si18" drivers ($450) (22.5mm xmax- claimed 3.5" peak to peak vs my xv15's 2" peak to peak)... rest of the materials included I'm guessing the total would be around $1,000. $500 less than my xv15's.!!!.. which again will help the wife accept the larger enclosure, and "justify" my desire to attempt the project!!!! If I can CRUSH what I already have.... i wouldn't feel so bad letting go of my xv15's.

I wish I knew how to figure out the capabilities of the diy set up... i have some numbers for the past subs to compare to Iiiiffffff that helps?!??!

Anxiously awaiting your replies! !!!
 

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Discussion Starter · #3 ·
Also looking into 2 fi q18's?!?!? Read would like to hear what someone with more experience thinks?!??! Ready to list the xv15's in the classifieds... buy want to have a plan for replacing them before someone snatches them up!!!!!! The q18's look like they want 1500 rms and it doesn't look like the EP2500 will push 1500 watts per channel?!? Yet 600 watts rms into the si ht18 is barely more than the xv15's I already have can handle. Just want to make the right choices.... looks like one xv15 puts out 98 db 2m ground plane @16hz.. so 2 would be barely reaching 115db with room gain ect... I'd imagine with bass management it may ask for 121-123 db at times... !?!? Idk... maybe the xv15's should be enough and I'm ridiculous like my wife thinks? !?!? But if u can get dual triax performance for what use got in these I'd do it in a heartbeat..... just not sure if it's possible without buying 2 ep2500 and 2 sp418... which I will do if you guys think it's worth it.... just not sure where cost to benefit goes to money wasted....
 

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Discussion Starter · #5 ·
I'm still searching and have found what appears to be my best option yet... Although the most expensive. Looks like I can pick up a pair km RLP18'S for $780... + $350 for the amp... The RLP18'S handle 1000 watts rms... and have a a much lower natural fs... than the fi q18's.... I've been reading around 650 liters sonotube tuned to 13hz or so with an 8" port should be pretty sweet!!!! Just want to be sure there will be noticeable difference. .. otherwise it's all for nothing.
 

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Discussion Starter · #6 ·
Please somebody chime in and help me out. I saw Sonnie put together 4 of the si ht18's. I'm thinking this may be my best bet?!??!

Let's say 4 SI HT 18's and a I nuke 6000. Should give me 600 watts rms to each driver... and what appears to be my best bang for the buck. What kind of enclosures should I use? Dual opposed sonotube? Dual sealed boxes (2 drivers each one)? Ported sonotubes???

Please give me some input guys. I know I'm throwing a million things about there... but that's why I'm asking for some help!?!?

I'm definitely ready to go with 2 or 4 si ht18 drivers and an I nuke 6000. Just want to know what you guys think will be the best way to put it together. I'm pretty sure a 4 driver setup is best as I want to absolutely certain I won't wish 8 hadn't sold my xv15's! ?!?! Please help?!?
 

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Discussion Starter · #8 ·
Thanks Mike p I appreciate your response!! I'm really struggling with what I want to run. I'm just now seeing a graph from another thread that a guy has dual RLP18'S modeling at 120db at 10hz (114 for a single) and nearly flat all the way through. The same graph shows the SI HT18 down 23dbs.... which he calculated to be nearly 14 si drivers to equal the same low frequency power of the dual rlps. To me.... that pretty much seals the deal!!!! Dual RLP18'S, one in each front corner powered by I nuke 6000. Just need to figure out the size of the enclosures and porting... and list the xv15's in the classifieds. Any additional help you can provide would be greatly appreciated. .. be it links or what ever you can come up with!!!?!? Thanks again!!
 

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Discussion Starter · #10 ·
Awesome Mike!?!? I really appreciate your help. Just not understanding how they wouldn't perform better. .. higher xmax... power handing...

Post #1032/1033 on the following page.

You will also see the xv15's(single sub) in room response via Josh ricci on same page as an example for someone else's comment. (#1045)

If I can save $200 per driver and accomplish the same task sounds great to me. But I'd really like to see a graph showing two si ht18's achieving 119-20db to actually believe it. Orrrrrrrr if you can explain to me that's just as good... I've just always been one who needs to understand the "why" of it all. I really do appreciate your help!!!!! Guess the others are bored of this kind of stuff!!!!
 

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Discussion Starter · #13 ·
Wooooow! !! Thanks Mike I didn't even realize that was the difference... !!!! The xmax is near 28 mm though in the pic... The SI driver is less xmax than that.... any issues there?!?!? So definitely worth saving the money on the drivers or getting 4 instead of 2. In your honest oponion.... is the extra effort in figuring out the enclosures and money in the 3rd and 4th driver worth it?!?!? Won't that be a bunch of extra headache just for 6 db's -/+?!?! I'm thinking may be better to save the money... keep it less complicated, and have the extra headroom in the amp. What do you think!?!?! The theater room is treated but small, 10' x 12' x 8' with opening on back left (doorway leading to a small room) and a 7' x 7' opening side/back right leading to bigger room. Still less than 2500 total area.

How about specs for a sonotube?!! Ported of course...
 

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Discussion Starter · #14 ·
I've read somewhere a good sonotube recommendation for the fi q18's or ss rlp18... was as follows....

"650 effective liters with an 8" diameter port @ 26" length is ideal. This would require a 28" diameter sonotube @ 71" in height.... (would be a replica of Steve callas own subs)"


being that the response is similar in the graph.. could I use these same specs for my SI HT18 enclosures????? Seems like the upper frequency will be there in spades... The lowest frequencies are the goal... without too much upper frequency loss of course!!!!
 

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Discussion Starter · #16 ·
Excellent!!! Thanks for all your help!!! I've listed the xv15's in the classifieds and already had a little buzz about them... The wife was second guessing me on this decision. Saying the xv15's are plenty.

I just can't help but feel 120db -/+ from the teens throughout the usable range and possibly more will drastically improve the movie experience!!!! Making it all worth it.

I'm fairly confident once I have the proper dimensions figured out, I can build enclosures that won't be too hard on the eyes.... which will make her feel better!!!!

Thanks again Mike!!.... Super nice of you to offer your knowledge, and help!!!! I've seen you all over the forum helping us out!!!!!
 

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The volume size needed is 500 liters tuned to 13 hz. For a sonotube you have 2 options, one is a tube 24" in diameter and the other is a tube 26" in diameter.

With 5" legs the 24" tube will be 82" in over all height and the 26" tube will be 71" in overall height.

Porting would be an 8" diameter sonotube which is sold in slightly different diameters as they are shipped one inside the other. Measure the inside diameter of what you buy and I'll figure out the exact length that you need for your tuning frequency.

An iNuke 6000 would be my choice to power these subs.

Disregard the RLP18 info in the bottom right of the modeling, that was just for the displacement volume needed.

Dimensions for a 24" sonotube:

24.JPG


Dimensions for a 26" sonotube:

26.JPG
 

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Discussion Starter · #18 ·
Hey mike!!! Thanks so much for figuring out those numbers!!!!!.. not my strong point. I'm in the process of selling the xv15's... seems like finding a local buyer may be the issue... not comfortable losing too much money on them... they're good subs. I dialed them in at 80 db each today (85db's combined) just to see what kind of headroom they have in this little room. Xt32 set them at -2 db on my last calibration so I left them alone. I'm guessing this would be running them around 83dbs...8db hott.* only about 1:30 on their gains.... i then put in Pacific rim blu ray reciever @ 0 (ref)... i watched the drivers in the heaviest scenes they were working but still have plenty more left... yachts the heaviest bass movie I own!!!! If im missing something I'd never know it. Yet, I KNOW I'm supposed to be missing 20-25hz and down. Guess I won't know what I'm really missing until I "feel" the difference. I mean if ref us 115, and bass management can ask for 123db total.... i was asking them for potentially db's more than that!?? The drivers were not stressed at all. Working- hard at the heaviest peaks.. but super solid. I knew at every moment they still had more. I know my room is small. 12' x 10'x 8'. But is 130db in room even possible in room with these xv15's?!?!?... or is something waaaaay off with my math. I don't don't have any accurate way if measuring things at the moment.

Thank you for everything!!!! I appreciate your help so much!!! Could I ask one more favor?!? You showed me a graph of a pair of si ht18's in optimal ported inclosures. Is this spl measurnement ground plane? Or projected in room measurements??? what I want to do is figure out what this pair of diy subs will give me spl wise in room vs my xv15's in room. My wife still doesn't understand what I'm trying to do... I'm thinking if can show her the numbers it will be easier for her to understand.... i honestly think it would make me feel better too!! After hearing those xv15's today... it has me wondering if I'm not crazy like my wife has been thinking all along! !!!! Thanks again for your help!!!!

I'll start checking into where I can find the sonotube in the 3 different diameters you listed. 8" is at home depot for sure!! Ideally I'll go for 26" and keep it a bit shorter!!!
 

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As for your db numbers, the only way to tell is to measure with a SPL meter as room gain is dependant on the specific room size. The modelling program I use estimates the SPL at one meter anechoic, to that you would add the effects of room gain which can be substantial.

There is a lot of sub 20 hz information in movies and it takes a lot of excursion to reproduce those frequencies with authority. I personally use a pair of 15's and a pair of 18's in a 15 foot by 26 foot room.
 

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Discussion Starter · #20 ·
I've been searching for local suppliers of the sonotubes and It hasn't been an easy search at all. I'll start calling around tomorrow.... will probably be much easier!!!! I've been reading all about these diy sub builds... and I keep seeing mention of a hpf?? Would this enclosure/driver/porting tune combination require one of these?!?!? Thanks again for sharing your knowledge Mike... i really do appreciate it. I've been non stop reading in all my free time. .. it's just you see soo much conflicting information it's difficult to know what's right and what's wrong.
 
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