4 dual opposed SSD 15s - Page 6

I have measured my LP and then EQ'd flat. I then measured my other seats and 60hz and below remained very similar and the 60hz and above dropped off a bit on the end seats. I was amazed how everything was pretty flat from seat to seat and all I did was EQ for the main LP. I also measured my 4 corners, front 2 corners(all different directions), and across the front as an array. Let me look for those.

LTD,

If you're gonna write a paper that seriously looks at how to mate sub with room, wouldn't you start by posting the anechoic response of the sub? Yes, you would. It would be ludicrous for me to design my signal shaper without that data.

IOW, can you tell me which part is the room and which part is the subs roll off below 40 Hz? There is a big difference between signal shaping EQ and corrective EQ.

I don't have the time nor the inclination to completely dissect these silly graphs and apparently neither do "peers".

I could easily post a paper showing how to get a flat response across my main 4 seats with a single sub location and no "auto EQ" or extremely heavy-handed post EQ.

Trouble is, it wouldn't say Harman International, so you wouldn't take it seriously.

The posted article is for the naive. It's the classic leading argument and so full of holes it's not worth the time to discuss it. If no "peer" sees that, then I would certainly question who these peers are, if I cared, which I do not. I just dislike this crap being brought to this forum and pasted up as some panacea with no one to question it.

Are we seriously 25 years into a discrete subwoofer channel with a spec of 3-120 Hz and hundreds of titles with effects designed to utilize the entire bandwidth, yet still considering a focus on 20-80 Hz a "paper"???

It's a rhetorical question. I'm not interested in what the 'peers' have to say, that's why I come here. It would be laughable to attempt to have a discussion here that begins with the premise that the area of concern covers 2 octaves.

Can you post the response of this JBL EQ?
What happens below 20 Hz when multiple sub locations and lots of EQ are used?
What are the dimensions and layout of this room?
What does the author consider to be a seat?
Where are these seats located in the room?
What sats, where are they located, what is the crossover point and slopes?
Where's the loopback of the signal shaping EQ?
Does that corrective EQ change sub amp headroom, the noise floor or anything upstream?
"As a side note, this doesn’t have to be expensive as you can use four lower cost subwoofers instead of a single larger subwoofer. No matter how good that one subwoofer, it cannot overcome the problems of room acoustics."
How does this ^^ blatant BS get a free pass?
What smoothing is used for these graphs?
What "calibrated microphones" are used and how were they calibrated?
What is the rest of the measurement chain and where is it's FR posted?

The article should be titled "the importance of FR averaged across all seats from 20-80 Hz when nothing else matters, following Harman placement edicts, using Harman hardware and software and working within the limitations thereof".

Bosso

Yes, Josh, but I've been down this road before. I've posted FRs from every seat, separately and averaged, smoothed and non-smoothed. I've posted FRs during every step of the anechoic vs in-room with signal shaping to bridge them after placement, phase, delay and levels tweaks. I wrote a setup guide based on all of that.

Guess what? No one cares. They seem to prefer to hang on to the Magic Room theory, or that some silly gadget will do all of that for you, as long as you have 4 subwoofers.


I would as well. Or, as I mentioned earlier in the thread, a stack plus a spread across the wall. Or anything real from actual posters' situations, really, anything but this Harman infomercial stuff.

I should head your way and we can spend a day trying the Harman white papers stuff vs whatever else approach and post the results for "peer review".

Bosso

"I should head your way and we can spend a day trying the Harman white papers stuff..."

save the trip. he already confirmed the principle finding that multiple subs located around the room reduce variation in the frequency response.

by the way, i have read your setup guide and thought that it was pretty good.


they are just talking about how it is better to have multiple sources because of mode cancelling. the more sources, the more mode cancelling and the smoother the frequency response all around the room. the question of inquiry in most of their work is how much is audible, how many sources are required, and where to locate them. that is the same thing that you have been testing with your blackbirds...where to put them and how many do need before it gets to be 'good enough'.

Given the paucity of electronics, let alone loudspeakers, that go down to 3Hz, chasing that kind of ULF is really just a game for fetishists.


Because it's not BS. Well, maybe for a single-digit fetishist it is. But for a music lover who wants higher fidelity reproduction, it's sound advice.

I see several people being correct here.

JBL ignores the z-axis for a very simple reason that bosso pointed out: they have no products that would fit the situation. While JBL/Harman does have some of the most complete documentation and information out there, they are still a for-profit enterprise, and don't think that any author's work is not looked at carefully by other JBL folks before it is published.

The theory behind the Welti/Devantier method is sound. Their process has many holes in it, unfortunately. Do you think that 'audience box' started out that small? HELL NO (or at least, probably not). But by making it smaller, they got to report better results.

The theory of the Geddes method is similar. But it also is flawed. Seriously, run a pink noise RTA/Spec Analyzer and wave a mic around to see what your freq response is doing 'in the listening area'? GTFO.

The best way to do a room setup is use some theory to help guide initial placements, then verify with measurement, modify placement/bass trapping/delays/eq/etc, verify again, and continue the iterative process until you reach nirvana or simply say 'good enough'.

All of the 'theories' and 'methods' are complete and total BS unless verified by measurement IN THE LISTENING SPACE IN QUESTION. There is no such thing as an 'average room'.

If you truly had a rectangular room with reflective/absoprtive capability the exact same for all 4 walls, ceiling and floor (what Welti and Devantier assume in their simulations), then eight subs, placed at the 1/4 points in all axes would be ideal. You cancel EVERY odd axial room mode and the first even room mode on every orthogonal axis. Second best would be to give up the 2nd mode cancellation in the z-axis and bury the subs in floor and ceiling at the 1/4 points.

JSS

John,

The distributed sub method can work...I am convinced of that and so are a lot of others...

Dave is contending that there are more ways to skin the cat and that a large vertical stack with drivers placed at various points from floor to ceiling can have a large effect in smoothing the response too and his measurements certainly show that something worth looking at is going on there. If you could have the smooth response but with all of the subwoofage placed vertically in a corner occupying perhaps a 20" square versus in 3 or 4 locations around the room occupying much more floor area that would certainly be worthwhile info to many people IMHO. I just want to see some more people try it in a few different rooms and see what happens. If I had an easy set of subs to try it with I would do it myself. I am going dual opposed soon and the cabs could be configured for stacking logistically but each sub will probably be 240lbs so lifting one on top of the other is a little daunting.



Just clarifying. I occasionally have to ask...Most of the time because I'm secretly hoping that you have some smoothing or EQ in there.


I should be moving into a new place this summer or early fall...That will mean a new room and starting from square one. The perfect time for a bunch investigatory work.

"Dave is contending that there are more ways to skin the cat and that a large vertical stack with drivers placed at various points from floor to ceiling can have a large effect in smoothing the response too and his measurements certainly show that something worth looking at is going on there. If you could have the smooth response but with all of the subwoofage placed vertically in a corner occupying perhaps a 20" square versus in 3 or 4 locations around the room occupying much more floor area that would certainly be worthwhile info to many people IMHO. I just want to see some more people try it in a few different rooms and see what happens. If I had an easy set of subs to try it with I would do it myself. I am going dual opposed soon and the cabs could be configured for stacking logistically but each sub will probably be 240lbs so lifting one on top of the other is a little daunting."

i understand what he is saying and his measurements verify that it works for him in his room in his seat and it may work just as well for some other folks in their room in their seat. like i said previously, this is nothing new though. the infinity irs cab had corner loaded vertical subs, so effectively does every line array.

stacking subs in one corner will reduce the same number of modes in the same way that placing the subs along the front wall/floor will. how it results in smoother frequency response at the listening positions depends on the room dimensions and where you measure.

the jbl/harman guys who looked at this concluded that placing all the subs along one boundary is an inferior approach. geddes concluded the same. i suspect that you concluded the same or you would be running all your subs along your front wall.

So, name these lower cost subs and larger, higher cost sub and let's explore your absurd assertion, shall we? "...it's not BS" doesn't cut it.

Also, please flesh out your "chasing" nonsense. You've worked far harder getting a decent response to 20 Hz than I have "chasing" an accurate presentation of actual content on actual discs from the 21st century.

The fetish here is yours, attempting to dictate to others your own personal version of bandwidth and discs are worthy of pursuit.

Bosso

You don't completely understand what I'm saying.

I'm saying that 20-80 Hz in the sweet spot of any room is easier than the trip to the venue.

You name the room and bring your "lower cost subs" in any quantity I'll be there to expose these silly papers.

It's funny how I can post results in 4 completely different rooms, all with a single subwoofer source and your conclusions is that "it works for you", but these other hacks use a single, gamed room and every other trick in the book and you buy the universal answer theory.

Bosso

I'm serious about it. LMK, and I'll plan the trip.

Bosso

Excuse me, but... well, duh. I'm well aware of what they're saying. You can't escape every sub owner on the commercial side parroting this theory of "multiple subs for smoothing" as a universal law.

Since you won't answer any of my questions (because you can't due to lack of data in these 'papers'), just answer one that you should be able to answer:

Why, if this multi-sub theory is the answer for every room, do they require 20-30dB of corrective EQ after the placement exercise?

Bosso

Can I hitch a ride? actually, you would drive right past me more than likely, so the trip could be broken up at least a shade

"You name the room and bring your "lower cost subs" in any quantity I'll be there to expose these silly papers."

bosso, if you want to blow up all the jbl/harman research, i'm not your target. just write up your work and present it at an aes conference. the whole audio community would be very interested to learn of your findings and how you will expose all the jbl/harman work as 'silly'. there are many aes conferences around the world, just pick one or two and go for it. many of the top minds in the field will be attending and they will appreciate your work. a hit will bring you millions of dollars in sales and/or consulting services. http://www.aes.org/

I will show some different placement measurements.

Here is my current setup with 4 subs going across the front stage. 4 CHT 18.2's, no EQ



Here are 4 CHT 18.2's with two in each front corner



Here was 8 eD sealed subs with 2 in each corner using all 4 corners



Here were the same eD subs all in the front stage with both corner loaded(up and down facing) and going across the middle.



I took these all at different times but all had a crossover engaged and some with mains and some without. You tell me which you think would be best because I would put the subs there again. I do like all the subs hidden behind the screen and can get flat. My next round of subs I can place 4 corners, across the front, and or stacked like an array and take measurements. This will be better as it will be using the same subs, same mic, same level, etc....

Will the orientation matter as long as the drivers go up towards the ceiling in an array?

hey gp, the irs (big vertical stack of 12's) and most all line arrays produce bass across several different heights. as a result, they, like bosso's stack-o-subs, knock out several room modes. bass waves are large relative to cab size, so the effect will be pretty much the same if they are front firing, rear firing, dual opposed, or up and down firing, if they are placed in the same location.

mk, for a typical 80hz crossover point, it shouldn't matter if you fire them up down left right forward or back. sounds like a software code. :-) and by the way mk, your sh_t is a home run. no doubting that.

the cht have a rising frequency response that requires a little knock-down eq. do you happen to have a measure with one cht in each corner in order to round out your measurement set?

I agree, I love the up/down firing stacking method with more displacement in one spot!

Shoot...I was hoping that you would host something. I want to hear your system some time.

I will put a post it note on it and revisit when the time is right.

If placed stacked vertically in the corners, where (IIRC) Bosso has his, the only mode I can see being affected much in a typical 8' ceiling room is the first height at ~71Hz. The vertical stack at say 1/4 width in would also have some affect on the 2nd width, but not much else I'm seeing for typical sub implementations.

Not having a dig as I like Bosso's stack, and have said so before.


Ah, memories. One of my first DIY systems was designed "referencing" these, with a stack of 10" drivers, 4" Fostex WR drivers and domes then DIY ribbons later. Passive too, with with huge parts counts.

Some day this summer, I'll see if anyone wants to head my way and run some <20 Hz exercises, listen to hits, eat, drink and be merry. I think it's long overdue. Problem has been that I've always been building and trying something new.

Looking forward to heading your when when the timing works... for real. Might bring some stuff for you to beat on as well.


Man, I wish you'd post more around here. Your posts are always top notch. Nicked quite a bit from them. Much appreciated.

Bosso

In the link I posted, the Harman stuff is not the interesting part(add subs, eq your way to flatness...simple enough...). The part about Yates supercomputers crunching out ideal sub locations for your specific room...now that is the cat's meow. I wish I had that knowledge for my own oddly shaped HT. I have lugged subs all over my room to try and smooth things out(and yes I have stacked in a corner, to no avail). If someone had measured the dimensions of my room and said "place subs here", it would have been sweet. It would especially be welcome for smoothing across two rows. I could get the front seats perfect at one point, but I had huge suckouts at various frequencies in row 2. Yates work would have been great during the HT build phase.

GP,

Did you save those frd files with easy to remember or descriptive names? Thanks.

James