As I'm going to build some subs using 15" woofers, going from 20 Hz (eq'ed) to 80-100 Hz, I have some questions.....
For pure "cosmetic" look I would like to have the woofers pointing downwards in the cabinet, and I meen that I have heard that you can't point out the source/location for sound below app. 100 Hz due to the human ear...
Are there any disadvantages having the woofers pointing down ????
For pure "cosmetic" look I would like to have the woofers pointing downwards in the cabinet, and I meen that I have heard that you can't point out the source/location for sound below app. 100 Hz due to the human ear...
Are there any disadvantages having the woofers pointing down ????
The suspension needs to be sufficiently stiff for this to work. You lose a little excursion due to gravity. Adire has a paper on determining if a driver is suitable. I think most are ok. You lose a tiny amount of SPL on paper. I just built a small cheap downfiring sub for my parents - you don't have to make a grille, the driver is protected, and it's simple.
hi ACD, i've got an Atlas 12 down firing in a 142.5L Shiva box tuned to 20HZ which has dual flared 4" precision port which seems to sound great! with no port noise problems with music, or HT. i think 5% cone sag is considered the max. which should be allowed from what i have read. i too, like the fact that no grill is required as it's safer, less cost, and less work. good luck with your project! crippledchickenACD said:
ACD said:Bill:
Your point is correct, however will horisontal mounting not also cause problems with the suspension, as the speaker weight will be carried by the upper part of the suspension.....
You can of course then turn your speakers a half turn every year
There is so much more to hold the cone in position with front mounting that I can't imagine problems until decades later.
paulspencer said:
Don't remember the woofer brand. The calcs weren't available then. When put into service, like I said, everything was fine. What sag there was, wasn't much at all. Your'e right about them not being suitable!
After the problem was discovered we designed boxes meant to be flipped over from time to time.
Maybe the problem doesn't exist these days but I think I'll have a hard time believing that.
I'd never set drivers facing down.
Two reasons:
- the obviously stated sag problem (real).
imho, after a bit the suspension will sag significantly.
ever store a woofer face up? I have - the suspension eventually
sinks down toward the gap. Spiders are designed to handle neutral mass, period. Especially true for non MI/stiff edge drivers, like the newer high xmax type.
- more importantly, in my experience, downward firing means that your floor becomes an integral part of the woofer's response. In many cases this is problematic. It certainly yields different results in different room/floor types. AND, the response will vary depending upon the height above said floor, and the floor's covering (concrete, wood, carpet, carpet w/underlayment).
If you really believe that the woofer's position/orientation makes no sonic difference, then why no just face the grille portion to the rear, and no one will see it?
ymmv, as always...
_-_-bear
Two reasons:
- the obviously stated sag problem (real).
imho, after a bit the suspension will sag significantly.
ever store a woofer face up? I have - the suspension eventually
sinks down toward the gap. Spiders are designed to handle neutral mass, period. Especially true for non MI/stiff edge drivers, like the newer high xmax type.
- more importantly, in my experience, downward firing means that your floor becomes an integral part of the woofer's response. In many cases this is problematic. It certainly yields different results in different room/floor types. AND, the response will vary depending upon the height above said floor, and the floor's covering (concrete, wood, carpet, carpet w/underlayment).
If you really believe that the woofer's position/orientation makes no sonic difference, then why no just face the grille portion to the rear, and no one will see it?
ymmv, as always...
_-_-bear
Sorry for the grave digging, but I have a couple of questions relating to down-firing woofers as the packaging advantages are irresistible.
Is there a way to calculate compensation of the response for the effective slot loading between cabinet and floor?
With some amplifiers, it is straitforward to adjust the DC offset. Has anyone thought about compensating for woofer sag in this way? May sound like a silly question, but I have a pair of Peerless woofers which spell out the requirement to only mount them vertically. I can understand why as they have sagged over 1/8th inch during storage face up. They are stored face down at the moment, awaiting an answer to this question...
Is there a way to calculate compensation of the response for the effective slot loading between cabinet and floor?
With some amplifiers, it is straitforward to adjust the DC offset. Has anyone thought about compensating for woofer sag in this way? May sound like a silly question, but I have a pair of Peerless woofers which spell out the requirement to only mount them vertically. I can understand why as they have sagged over 1/8th inch during storage face up. They are stored face down at the moment, awaiting an answer to this question...
Tosh said:
Do you mean that the floor immediately in front of the port opening acting like an extension of the port resulting in a slightly lower tuning freq?
If so, this also applies to the port opening inside the enclosure as well and there are calculations to correct for this.
When I build my twin enclosures, they too will be slot ported (3" x 15") and will be positioned vertically to minimize the effects, plus the port inside will start in the middle of the enclosure, nowhere near the enclosure walls.
And as for forward or downward firing, I prefer forward firing. Maybe it's just me, but I seem to notice a bit more impact and detail from the sub when the driver is facing the listening area.
To me, down firing subs tend to miss out on some of that detail and impact, such as a nice tight punch to the chest or being able to tell the difference between an electric bass and a regular acoustic double string bass. Even with a crossover point of 80Hz @ -24dB per octave, I can still hear the tonal differences of the two.
Downward firing subs like the SVS PB12-ISD/2 I had which was an excellent sub by any standards still sounded a little soft around the edges as far as sharp bass attact and detail was concerned. I guess I'm trying to say that down firing subs seem to sound a tad bit on the "muffled" side to me.
And I would think that cone sag would also slow down the movement of the driver a little too, making it sound not as detailed.
In fact after thinking about it, how many companies do you know of that still make down firing subs? I think the ratio of front firing verses down firing sub these days is rather high. Velodyne, VMPS, Bag End, Paradigm, Definitive Technology, B&W, etc, etc..., all make front firing subs, where as down firing subs go to SVS, HSU and ??? I really can't think of any others at the moment.
chops said:
No, I'm talking about the gap around the perimeter of the enclosure between the edges of the subwoofer cabinet and the floor. For example, if I used bottom-mounted 10" driver in a box with a 12"x12" footprint and 2" long feet, there would be a 2" x (4x12") gap through which the bass would be trying to squeeze (in addition to the floor reflections) changing the response by a slot loading type effect.
I am aware of more commercial subs being vertically mounted (presumably because their drivers didn't pass the under 5% of Xmax sag recommendation), but I would like to exhaust the options of horizontal mounting before I cave in.
I also happen to like the downfiring HSU subs in the cylindrical enclosures. And I believe tight bass comes more from using low distortion woofers (with high bandwidth capability) and well-integrated lower midrange than just the simple arrangement of front firing woofers. But I've heard both good and poor subwoofers with front and bottom mounted drivers, and I understand where you come from.
Firing at the floor also means you will never have canceling frequencies because the distance between subwoofer and floor is too short and any several reflecting, oh wait there will never any thing that serious, it will dissipate in that kind of an enviroment from air pressure. That is one thought I have... However I also presume any down firing subwoofer will be crossovered under 80hz or less, only the frequencies where direction is not important.
Sonically I bet it depends on what type of floor you have.... It is a difficult arguement to claim the floor instantly is part of the acoustical attribute when a subwoofer firing in any direction has wavelengths of sound so long it will hit, vibrate, and resonate off of every thing that does not abosrb it. This of course varies with frequency but unless your room is HUGE... and even then subwoofers have a tendancy to have frequencies develop off of their own box or from the wall behind them which get sent forward and can cancle out the original frequency. Hence down firing is not so bad. I realize all instances I have come up with are not always so, but they do happen.
Sonically I bet it depends on what type of floor you have.... It is a difficult arguement to claim the floor instantly is part of the acoustical attribute when a subwoofer firing in any direction has wavelengths of sound so long it will hit, vibrate, and resonate off of every thing that does not abosrb it. This of course varies with frequency but unless your room is HUGE... and even then subwoofers have a tendancy to have frequencies develop off of their own box or from the wall behind them which get sent forward and can cancle out the original frequency. Hence down firing is not so bad. I realize all instances I have come up with are not always so, but they do happen.
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