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Please help a "Rookie" with his first full blown DIY LFE endeavors (18-21" sealed/dual opposed)

post #1 of 12
Thread Starter 
Hello all,

The blessing of a new baby boy has literally lite a fire under my buttox to work on finishing my dedicated theater room. Before this, I had planned to learn slow and take my time researching and making a decision on a build. Now I feel a much greater urgency to get things going. Although I have built two DTS-10s and am constantly try to read and learn from those in the DIY forum, I would still consider myself a rookie to DIY. I am a sheet metal mechanic who has had some plastics fabrication and machining experience so my handy skills are pretty good.
Some general information about my build and ideas are as follows

Previous subs:
I was running 2 DTS-10s which I built with a single EP4000.
Before that I had 2 AV123 MFW-15s

Room and sub space dimensions:
My room dimensions are approx. 20'L X 12'W X 8'H
My screen wall is built in front of an encove that is 8'W X 7'H giving me an available sub volume area of 96"W X 24"H X 23"D.

I want to essentially match or better the performance of what I was getting out of my DTS-10s to include clarity and output (maybe stable down to 15-18hz). I do not think I am a crazy output freak like some of you maniacs wink.gif I read about. My purposes and motivation for extra power/displacement would be to decrease THD. I feel the output would be there anyways using 4 properly powered drivers.

My ideas:
Given the measurements of the alloted sub space I have, I feel that multiple (4) sealed enclosures or 2 dual opposed enclosures would be best. The first idea of sealed enclosures is pretty straight forward. I think last time I checked, Erics 4cuft flatpack would fit this space fine. The only way I could do dual opposed is to orientate the enclosure deep side facing the viewer (drivers firing at each other and the side wall).

Driver selection:
Dayton 18HO- Very popular choice as of late but there seem to have been arguments as to its sub 20hz performance and output.
Q Would these work better in separate sealed enclosures across the front stage or dual opposed configuration oriented as described above?

SI HT18- Cheapest of the bunch and model similarly to the HO. Configuration and number of drivers would probably be identical to the 18HO.

FTW21- These got put on my list when I read about the preorder pricing and shipping. IIRC, these drivers optimally require approx. a 6cuft enclosure so I would probably only be able to fit 2 in the space I have. I might be able to fit 4 drivers in a dual opposed configuration but I think that would be really stretching it.
Q: My question about using this driver would there be a audible concern trying to build a 6cuft enclosure using this driver with only 23" of depth to work with?
Q: Powered by two EP4000s or a Cervin Vega CV5000 would two FTW21s be plenty in my space.

Final thoughts:
Right now, with the FTW preorder going on, I think I need to get to a decision quickly as far as what driver and configuration would be best for my space. Once again, I am new to this so I apologize for the lack of technicality in my post. Any insight would be greatly appreciated. I will maybe post a pic. of behind my screen wall if that would benefit.

Thanks in advance!!!
post #2 of 12
Id go with 2 dual opposed 18s either the Dayton or the SI, they preform almost the same. Gorilla83 has 4 of them, I heard his system when he only had 2 of them running off the XLS5000 and they put out a stupidly large amount of bass in a space larger then yours.

Its the most economical choice vs the 21s or other 18s and they do play low. some simple EQing and you can get to sub 10Hz pretty eaisily. box size may be close in your space but you could go with 4 single across the front stage as well. the 4 CUFT box mine are in is roughly a 24" cube
post #3 of 12
what makes you think the THD is too high with your current DTS-10's? your room dimensions come out to 1920 cft. Two DTS-10's in that small a room should have zero distortion. unless your mistaking your walls cracking for distortion biggrin.gif
post #4 of 12
+1 you will not beat the THD performance of a horn with what you propose. Scroll down for THD data, and note that the DTS-10 horn is playing 6dB louder with less distortion.

If THD is still an issue for you, there's a lower THD upgrade for the DTS-10's... which is the DTS-10 used above.

The one thing a large sealed array can do well is infrasonics, especially compared with many horns, tuned somewhat high due to size constraints. Not so DTS-10... 14.5Hz native tuning frequency is plenty low, speaking as a sealed sub user.

HAve fun,
post #5 of 12
Thing about horns like the DTS-10 is the huge spike in group delay at certain frequencies. For the DTS-10 it is around 55hz.
I have always theorized that spectral decay and group delay play a significantly larger role in how well people think speakers sound than distortion.
When people say a speaker or a sub sounds "clean", most often they refer to quick decay time.
It is simply a pattern I have noticed from my own experiences so take it for what it is worth.
This is why I personally prefer sealed systems.
post #6 of 12
"I want to essentially match or better the performance of what I was getting out of my DTS-10s..."

1. why not use your dts-10's?
2. check data-bass for dts-10 measurements. add 6db because they are 2m measurements. add 6db because you have two of them. compare with winisd models for 18ho, si18, and ftw21.

seems like you could get 3 ftw21's in there just fine or perhaps 6 18-ho's. both of those model up quite closely and should be in your performance ballpark.

btw, what ignoramous is making arguments about sub 20hz performance from the 18ho?
post #7 of 12
Thread Starter 
Hi guys,

please bear with my post as I am out of my local area and am limited to posting from my phone.

Regarding THD, I was not referring my DTS-10s lacking THD. I was simply putting THD as a priority over output in my space (mainly because it wont take too much to get the output in my smaller room). My DTS-10s performed effortlessly in my space.

LTD-02- I am forced to sell my DTS-10s because I cannot fit them and my mains behind the screen wall. I am sad to see them go!!! Got one left to sell. I am going to forego the source of the sub 20hz argument for credibility reasons. There seem to be more members confident of the Dayton's sub 20hz capabilities.

Would 23" of depth be enough for an FTW21s (actually it would be more like 21" in the cab)

Also, I am assuming that orientating a dual opposed enclosure firing into the side walls would be fine.

The Dayton's really seam like a great value and is the driver I was almost set on until I read about the FTW and ULX18 performance. With that said I wanted to keep the project cost to under 1800.00. I currently have an EP4000 and inuke 3000 so I would either sell them for a single CV5000 or XLS500.

I really do not have an issue going with the cheaper option 4-6 Dayton's in 2-3 dual opposed enclosures if the 2-3 FTWs would provide marginally performance gains.

Would 6 cuft be good for a dual opposed configuration with the Dayton's?
post #8 of 12
two 6-7 cubic foot dual opposed cabinets with four ho's with a cv5000 amplifier is a nice combo. the drivers can be paralleled, 2 per channel, for 1250 theoretical watts each (2500 per channel at 2 ohms). that is enough to push them to their usable xmax which is around 18-20mm or so.

four uxl's in as large of an enclosure as you can fit in there all drivers forward facing, might get you about 3-4db more spl at 10hz (because they have more excursion potential), but more or less the same from 25hz up. but, this option is more money.

two ftw's in about the same total enclosure volume as the daytons and also powered with 5000 watts produce about the same spl (it's almost identical in model), but the drivers are 4 ohms, so can't be wired to get the full 5000 watts out of a cv5000.

blue = 4 x 18ho
red = 4 x uxl
yellow = 2 x ftw21

all with 5kw. all would be fine.

post #9 of 12
is it just me or does the 4 UXL's look like the best option there if going for max ULF? all are very comparable
post #10 of 12
you are probably right. the uxl costs about double the dayton ho's though, so that last 3db at 10hz is pretty expensive.
post #11 of 12
Thread Starter 
thanks LTD-02 for the simulation. Considering 4 ulx's would be almost double the price, the 18ho's seem like the solid choice for me.
Heck, I might even be able to fit a third 6cuft dual opposed enclosure behind my screen wall.

If I am not mistaken, gorilla83 has s detailed build thread using Dayton drivers in a dual opposed configuration. I will try and dig that up from my phone.

last I heard, the daytons were out of stock. I am gonna check tomorrow. More to come. Thanks for the clarification again guys.

post #12 of 12
rillas thread

daytons are out of stock, says they "should" be back 4/23
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AVS › AVS Forum › Audio › DIY Speakers and Subs › Please help a "Rookie" with his first full blown DIY LFE endeavors (18-21" sealed/dual opposed)