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First build - Octo SI 18's with flat packs. - Page 20

post #571 of 816
Thread Starter 
Quote:
Originally Posted by gpmbc View Post

The couch is a big sectional so I have one firing directly into the side of the first seat a few inches away. The other one is more towards where the couch starts to curve. The impact is ridiculous. It actually startled me when watching the Dark Knight Rises, I wasn't prepared for the impact when it hit during one scene in particular. The caps also survived the hulk and httyd. Those both have infrasonics that I thought would cause some bottoming out but no issue. I think being so close it's just not working as hard and being tuned to 15hz. It still sounds/feels good with just the SIs but the nearfield caps are just abusive!

I may have missed it, did you do a build thread? If not can you post pics of your setup or links to where you have already posted it? Sounds awesome.
post #572 of 816
not everything is as it will be but for now this is it. Excuse the wires and mess, it was testing time. The subs are dual opposed btw. I'm not home now but I'll post a pic of the back of the room later.
post #573 of 816
Thread Starter 
Quote:
Originally Posted by gpmbc View Post

not everything is as it will be but for now this is it. Excuse the wires and mess, it was testing time. The subs are dual opposed btw. I'm not home now but I'll post a pic of the back of the room later.

Oh my. So those are sealed dual opposed boxes? How many cu ft are they? That's a triple 12 center and what are the intimidating mains? That whole front wall just says, "I'm gonna kick your ass!"

More questions, how low do the mains go, what crossover level are you using? How did you integrate sealed and ported caps? Any issues there?

I've seen you around for a very long time, but I don't think I've ever seen your room thanks for the pic.
post #574 of 816
Yep, dual opposed about 8.6 cubes for the pair of drivers. The horns are jbl 3731/32 and the midbass is a jbl 2242. I have a third one that's the same but I have to figure some things out. For now the triple 12 is doing fine.

I'm using a Marchand bassis to address the low end of the SIs. Otherwise I just placed the caps AVS adjusted the trim levels thru the receiver and the amp in conjunction with omni mic to see what I'd get. I'm crossing over at 80hz. No problems that I discern with sealed/ported. I've been around for awhile I've posted some pics here and there of my previous room.
post #575 of 816
just a couple of thoughts on the ~100-110hz suckout.

if the speakers are located 1/4 wavelength of a wall, you will get a cancellation. the first obvious boundary is the wall behind the speakers.

at 110hz, 1/4 of a wavelength is about 2.5 feet. any chance the speakers are 2.5 feet from the wall?

second is a possible ceiling reflection. when the sound leaves your speakers some of it goes directly in a line from the speaker to your ear. some of the sound heads up to the ceiling, hits the ceiling half way in between the listening position and the speaker, then heads back down to the listening position. if the total distance of the reflected sound is 1/2 of a wavelength longer than the direct sound, it too will cause a cancellation (because it will arrive 180 degrees out of phase from the direct wave). back of the envelope calculations for a distance to the speakers of 11 feet and a vertical distance to the ceiling of 6 feet gives a total reflected path length of 16.25 feet. so the reflected sound is traveling 5.27 feet longer before getting to the lp. 5.27 feet is 1/2 of a wavelength of a 10.54 foot long wave, which predicts a cancellation at about 107hz.

so you may have two cancellations in the 110hz region. that could really suck. :-)

same thing happens off the floor, but the frequency is much higher.
post #576 of 816
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post #577 of 816
post #578 of 816
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

just a couple of thoughts on the ~100-110hz suckout.

if the speakers are located 1/4 wavelength of a wall, you will get a cancellation. the first obvious boundary is the wall behind the speakers.

at 110hz, 1/4 of a wavelength is about 2.5 feet. any chance the speakers are 2.5 feet from the wall?

second is a possible ceiling reflection. when the sound leaves your speakers some of it goes directly in a line from the speaker to your ear. some of the sound heads up to the ceiling, hits the ceiling half way in between the listening position and the speaker, then heads back down to the listening position. if the total distance of the reflected sound is 1/2 of a wavelength longer than the direct sound, it too will cause a cancellation (because it will arrive 180 degrees out of phase from the direct wave). back of the envelope calculations for a distance to the speakers of 11 feet and a vertical distance to the ceiling of 6 feet gives a total reflected path length of 16.25 feet. so the reflected sound is traveling 5.27 feet longer before getting to the lp. 5.27 feet is 1/2 of a wavelength of a 10.54 foot long wave, which predicts a cancellation at about 107hz.

so you may have two cancellations in the 110hz region. that could really suck. :-)

same thing happens off the floor, but the frequency is much higher.

Thanks for the ideas as to what's causing the dip LTD.

Yeah I thought about the cancellation due to speaker placement and I'm sure that's happening but it's interesting that I get the same exact null around 100 with the speakers off and subs on with a higher crossover set and I got this null regardless of sub position around the room (except for having the mbm right behind my LP).

However, I'm sure some of it could be helped by changing the position of the speakers. Unfortunately I don't really have anywhere to move them, I'm limited with that since my screen is so wide and I want to have subs in the corner. I did make sure that the distance between the speaker drivers is NOT the same distance from the front wall as they are from the side walls, I've read that causes a lot of problems too.

Putting panels on the front wall behind the speakers won't really work since my screen is so wide, but would putting panels on my ceiling at the first reflection points help?
post #579 of 816
Thread Starter 
Well, I killed one of my can lights. I was watching some scenes and I really got crazy on the volume and hot bass during the 3rd Matrix movie scene when the Machine says, "SPEAK". All of a sudden the light shuts off. I assumed it was the bulb but a new bulb won't either. So I assume some wires came loose. I have no experience with this kind of thing, will this be an easy fix? thanks
post #580 of 816
Quote:
Originally Posted by carp View Post

Well, I killed one of my can lights. I was watching some scenes and I really got crazy on the volume and hot bass during the 3rd Matrix movie scene when the Machine says, "SPEAK". All of a sudden the light shuts off. I assumed it was the bulb but a new bulb won't either. So I assume some wires came loose. I have no experience with this kind of thing, will this be an easy fix? thanks

I would say shut that breaker and pull the cans down one by one to see if anything got knocked loose. It sounds like you think it was one in particular, so obviously start with that one.
post #581 of 816
probably shook a connection loose or broke it inside the light.
post #582 of 816
Thread Starter 
I haven't had a chance to mess with the light yet, but I did find the roll off test of my receiver that mr smithers did a few months ago. Looks pretty bad, I'm down 3 db from 30hz to 10hz and then like a rock below that.



Note that it is 2 db increments on the left, not 5.
post #583 of 816
So what you're saying is reference at 10db is not in your immediate future? biggrin.gif
post #584 of 816
Quote:
Originally Posted by carp View Post

I haven't had a chance to mess with the light yet, but I did find the roll off test of my receiver that mr smithers did a few months ago. Looks pretty bad, I'm down 3 db from 30hz to 10hz and then like a rock below that.



Note that it is 2 db increments on the left, not 5.

Why is it the reciever that is rolling off? What AVR is it?
post #585 of 816
Thread Starter 
Quote:
Originally Posted by bass addict View Post

So what you're saying is reference at 10db is not in your immediate future? biggrin.gif

I can do reference at 10hz I'm pretty sure, but I want to be able to go well above that when I'm in the mood. Hell, I better be with this many subs!!
post #586 of 816
Thread Starter 
Quote:
Originally Posted by audiovideoholic View Post

Why is it the reciever that is rolling off? What AVR is it?

I hear that all receivers have some roll off, some worse than others. Keep in mind it's not as bad as the curve looks since it's 2 db increments on the left side of the graph but still it's not good. 3db's down at 10hz I can make up for somewhat but 8 db's down at 5hz I can't do much for which is why right now I'm just focusing on being flat to 10hz.

I am flat to 10hz at reference levels without clipping the amp at all, in fact it breezes through even the tough scenes. If I want to go bass hot over reference though I start to clip on those tough scenes.

My avr is a Pioneer Elite vsx 53.
post #587 of 816
that curve doesnt look bad to me. down 5db from 10 to 5Hz ? nothing boost shouldn't easily be making up for right?
post #588 of 816
Thread Starter 
Quote:
Originally Posted by brian6751 View Post

that curve doesnt look bad to me. down 5db from 10 to 5Hz ? nothing boost shouldn't easily be making up for right?

Yeah but that's just roll off of the receiver itself, nothing else. So you end up fighting the drop off of the drivers freq response, my crappy room down low, and the roll off of the receiver and it's a lot to overcome. I can't get flat to 5hz at reference without going way over 10db boost using the linkwitz transform on the minidsp and I've heard you don't want to go above 10db boost.

So, for now I've given up trying to be flat to 5hz, I'm just sticking with flat to 10hz.

Mrsmithers also tested his receiver and the roll off wasn't nearly as bad, can't remember what he said it was.
post #589 of 816
That rolloff is a perfect f3 at 10hz as it looks. 10dB boost would get you flat to 5hz, and I have gone as high as 15dB boost down low to try and get that. I think you are in good shape really. The amp will squeal until you get another, or a clone. Please believe that. Ive given my SI's every lick of juice ive got from the 14k and they have been just fine. I watched Popa do the same and they just kept chugging, you should be just fine smile.gif
post #590 of 816
Thread Starter 
Cool Brandon, good to know these drivers can take a lot.

However I think my room makes it extra tough to get down to 5hz.


This graph is with 10 db boost using LT and then also some eq pull down centered around 30hz. Notice the increments on the left are 10 db's do I'm down almost 10 db's from 10 hz to 5 hz and that's with the LT.


post #591 of 816
"I've heard you don't want to go above 10db boost."

that is because it eats up a lot of amp, driver, and s/n ratio.

since you have an electronic rolloff (looks like a 1st order bessel protection circuit to me), then you won't be losing any amp or driver, just s/n vs. where it would have been had the protective filter not been there in the first place.




in the picture that you just posted, 5db of that rolloff from 10->5hz is the protective filter.
post #592 of 816
Quote:
Originally Posted by carp View Post

Cool Brandon, good to know these drivers can take a lot.

However I think my room makes it extra tough to get down to 5hz.


This graph is with 10 db boost using LT and then also some eq pull down centered around 30hz. Notice the increments on the left are 10 db's do I'm down almost 10 db's from 10 hz to 5 hz and that's with the LT.



Your amp claims Frequency Response (+/-3.0 dB) 5Hz – 50kHz, so I am guessing ~ -6db at 5 hz.

Your receiver is -8 at 5hz. So just those two together ~ -14db down at 5hz. Add 14 db to your graph at 5 hz and its easy to see how signal chain roll off can add up fast.
post #593 of 816
im wondering though, does it really add up the way we think? is it compounded db for db or is there some kind of overlap/ counteraction?
post #594 of 816
Quote:
Originally Posted by brian6751 View Post

im wondering though, does it really add up the way we think? is it compounded db for db or is there some kind of overlap/ counteraction?

Yes it adds up that way. Its like overlapping hpf's.
post #595 of 816
Quote:
Originally Posted by Luke Kamp View Post

Yes it adds up that way. Its like overlapping hpf's.

well. that sucks..........

now i wont sleep till i measure my avr's response eek.gif
post #596 of 816
Thread Starter 
Quote:
Originally Posted by Luke Kamp View Post

Your amp claims Frequency Response (+/-3.0 dB) 5Hz – 50kHz, so I am guessing ~ -6db at 5 hz.

Your receiver is -8 at 5hz. So just those two together ~ -14db down at 5hz. Add 14 db to your graph at 5 hz and its easy to see how signal chain roll off can add up fast.

Luke I don't get what you are adding together. I see from my receiver roll off graph that I am down 8 db's at 5hz, where does the other 6 come from? From the claimed freq response of the amp? That shouldn't matter since we have the actual response which is 8db's down right?

Either way, yeah that's a lot to overcome. Ha, looks like I have yet another reason to start saving for a new receiver. I've never been a fan of Audyssey but I've never actually had it in my room so maybe I'll like it there. Also, it would be nice to have separate crossover setting options for the speakers as well as more options. Currently I have 50hz, 80hz, 150hz, and 200 hz as my crossover options and all 7 speakers have to be crossed over at the same frequency.

Luke I still want to get you over sometime to see how my room does with some more treatments if you don't mind, maybe this summer.
post #597 of 816
Whatever the amp roll off is will add to the chain before it. I don't know the actually amp response and have not seen it tested and am making some assumptions off of the specs.

Yeah I will bring those panels over when we can get together. I know between school, track, kids, wife's ... summer break would probably be easiest for us to spend a day playing around.

Its up to you if you think the < 10hz is worth the trouble of replacing current receivers and amps. Personally I think more bass treatments and panels or a light cannon for the 158" gray screen would be of higher priority, but different strokes for different folks as they say.smile.gif
post #598 of 816
Hi Carp,

Since I had some of your previously posted FR graphs and L/T info, I thought I'd LYK that you have the same room gain profile all of us (who have posted enough data to extrapolate) have.

Here's a composite with:
a) The measured naked response, give or take a small enough variance.
b) The L/T you described earlier applied to the naked response, give or take some small data points.
c) The AVR roll off.
d) The amp roll off, from manny's spec. (Side note: The amp folks don't cheat like Ilkka, Seaton, Chase, et al. (+/-) 3dB is + (above 0) or minus (below 0) 3dB, not +0/-6dB)
e) The cumulative roll off (less the Mini).
f) The result @ the LP.



Your Room Gain starts at 30 Hz and is approximately +6dB/Octave. That's the same room gain profile, (+/-) 2dB, as My room, Ricci's, MKT's, etc., etc.

My advice: Lose the AVR. wink.gif You have quite a bit invested in a tweakable full BW subwoofer system with headroom to cover it all. Too much to let it be compromised by a non-SW-friendly AVR. smile.gif

Since I only use my HT for MC music and movies and I use tweaks instead of smoothing EQ, I decided to try the new Oppo flagship as a preamp/player and shelf the AVR altogether. My L/T is flat to 2 Hz and the clone-type amps are flat to 3 Hz. That leaves only the roll off of the Oppo. That's not to mention the possibly SQ jump with Oppo's ESS Sabre reference DACs and the playback choices; SACD, DVD-A, etc., etc.

Here's what your result might look like if you opted for such a change:



I've been sayin' it for a long time; signal chain is the culprit that's always mistaken for "my room has lousy room gain".

I'll post back when I get the time. We did measurements of the mains and subs, close mic and at the LP as well as zoomed SpecLab caps with music and movies of the existing signal chain vs the one I just described. Interesting stuff...
post #599 of 816
We need posted roll off specs for every avr manufacturer model stat!!!
post #600 of 816
Informative post bosso. I didn't know about d) and half the time don't know what to think of some specs. I know my dog is happy about the 50kHz. Look forward to seeing more about your system changes and measurements.

I agree brian, a thread with posted roll offs of avrs, eq devices, blu-ray players... would be sweet. So much time is spent on subwoofer extension and graphs when our signal chain can diminish the ULF signal before the driver has a chance.
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