Hi guys (& gals?),
I have just finished Lynn Olson's Ariel speakers and have them up and running. They sound grrrreat!!!!
I am now in the process of building Siegried Linkwitz's Thor sub-woofer.
http://www.linkwitzlab.com/thor-intro.htm
I am looking for advice and/or opinions as to the suitability of setting them up as down-firing subs. Specificaly, how far off the ground should the drivers be?
Any comments would be greatly appreciated.
Thanx,
fred p.
I have just finished Lynn Olson's Ariel speakers and have them up and running. They sound grrrreat!!!!
I am now in the process of building Siegried Linkwitz's Thor sub-woofer.
http://www.linkwitzlab.com/thor-intro.htm
I am looking for advice and/or opinions as to the suitability of setting them up as down-firing subs. Specificaly, how far off the ground should the drivers be?
Any comments would be greatly appreciated.
Thanx,
fred p.
This is a big subject and people have there own views!
I always find because ever driver is different they all yield such different results in the same box design.
REL in the UK only make downward firing subwoofers, for the AV market, i think for the best high end sound a forward firing woofer is best for integration into the sound stage.
IMO, plus i dont believe bass is undirectional as ever source point has a path of travel and i can always tell where the bass is coming from
I always find because ever driver is different they all yield such different results in the same box design.
REL in the UK only make downward firing subwoofers, for the AV market, i think for the best high end sound a forward firing woofer is best for integration into the sound stage.
IMO, plus i dont believe bass is undirectional as ever source point has a path of travel and i can always tell where the bass is coming from
Sag
Not every sub is suitable for down firing orientation. Gravity can get nasty with the driver.
Not every sub is suitable for down firing orientation. Gravity can get nasty with the driver.
Re: Sag
Keep going, i want to hear more,
I think gravity can be bad on a cone but its arguable if upward or downw ward firing is better,
flypig said:
Keep going, i want to hear more,
I think gravity can be bad on a cone but its arguable if upward or downw ward firing is better,
You'll have sag issues if facing up or down:
http://www.adireaudio.com/Files/TechPapers/DriverOrientation.pdf
Typically drivers are faced down or out; facing up implies mounting the driver on the top of the cabinet, and that is usually not done for several reasons:
- Worse boundary coupling as compared to bottom mounting
- Harder to physically protect the driver from damage
- Places mass at the top of the cabinet which can be a stability concern
I'd say either look at downfiring or frontfiring; if crossing over fairly low (below ~125 Hz), downfiring is perfectly acceptable, provided your driver can work in that orientation.
Dan Wiggins
Adire Audio
http://www.adireaudio.com/Files/TechPapers/DriverOrientation.pdf
Typically drivers are faced down or out; facing up implies mounting the driver on the top of the cabinet, and that is usually not done for several reasons:
- Worse boundary coupling as compared to bottom mounting
- Harder to physically protect the driver from damage
- Places mass at the top of the cabinet which can be a stability concern
I'd say either look at downfiring or frontfiring; if crossing over fairly low (below ~125 Hz), downfiring is perfectly acceptable, provided your driver can work in that orientation.
Dan Wiggins
Adire Audio
More reasons to downfire
Downfiring will inject some acoustic LP filtering into the equation, giving additonal acoustic roll-off of mid frequencies, which can be quite significant if the electrical LP filtering is of the typically low slope used in subs. Additionally it will lower the radiating plane further fom the ceiling, which will help drop the cancellation node of the ceiling reflection down to a less obvious frequency.
You should figure out the clearance via an RTA after completeing the box, as the distance to the floor will affect the boundary loading and is something you'll want to be able to fine tune.
Downfiring will inject some acoustic LP filtering into the equation, giving additonal acoustic roll-off of mid frequencies, which can be quite significant if the electrical LP filtering is of the typically low slope used in subs. Additionally it will lower the radiating plane further fom the ceiling, which will help drop the cancellation node of the ceiling reflection down to a less obvious frequency.
You should figure out the clearance via an RTA after completeing the box, as the distance to the floor will affect the boundary loading and is something you'll want to be able to fine tune.
DanWiggins said:
A friend i know made his subwoofer system into his wooden floor, the drivers were upward facing and the results were very good.
It was a basic horn loaded design and it was tuned very low indeed.
The sag is not an issus really, as the cone has very little weight but agreed it can have an effect over time, but then again there is sag on any cone as gravity never takes a break, There have been a few speaker makers that have used woofers on top, but not subwoofers i must say, I like forward facing woofers but i like to see what i paid for and i feel its the most direct route for the bass wave to your ears, time delay is important as bass waves are the slowest.
Paradise_Ice said:
The speed of sound is medium dependent not frequency dependent.
Whether a woofer works well down firing is driver dependent as stated before.
Yes thats true, but why do we have sloped baffles, downward firing to me is slower but adds damping to the cone, its my own choice, i like forward firing, thats juts for me.
Sloped baffles are for phase and time alignment of two (or more) units. With subwoofers you can do the time alignment in the sub amp and often also in a HT amp. Most sub amps can adjust the phase with a pot from 0 to 180 degrees. If you need your sub to go relatively high frontfiring can be a better option as some lower mid will be audible. If you can stay low (say below 70-80Hz) then there is no reason not to go downfiring. As you mention a thor sub I assume that you keep the crossover low.
Would you really want to do that in a ideal world? i would rather not have the need for any crossovers as we all agree they mar the sound even if there an important part of the design for many reasons, I dont know if your remember but Naim had a 15 in driver with an isolated mid and treble units on top, each one was staggered back from each other.
Paradise_Ice said:
Subs must have some kind of crossover, since none can play into the upper frequencies. I'm a minimalist by necessity and want as little in the signal path as possible, but for a sub an xover is mandatory to send it only the lower frequencies.
The staggering you refer to is for time alignment purposes.
The bottom line is that some sub drivers function reasonably well in a down firing alignment. Adire Audio has some calculations to help determine whether a specific driver is suited for downfiring, however, downfiring affects any driver in a negative way. It reduces useable Xmax and affects the impulse response both of which are a simple matter of physics and the effect of gravity. Downfire if you have to and it might be OK for HT, but for music I'd say no don't.
Re: More reasons to downfire
Hi again,
I'm back, and thank-you everyone for the enlightened discussion. The consensus seems to be: Do it if you must, and I must.
Thanks Dan for the info. I calculated the sag factor for the Peerless 12" XLS subs and with an Xmax of 12.5mm, it comes out to 6%. (Their 10" XLS sub comes in at 5.5%.)
I'll be Xing over at approx. 80Hz.
Not that I want to seem to be shunning your advice, I will be setting up the subs as down-firing - 6% is not that far off, and the subs are already bought. An important consideration has to be room size, placement and esthetics, and in my case down-firing is the best compromise.
I will be making a removable base/stand so if it turns out badly I'll be able to revert to front-firing, which brings me to my next question:
Thanks Bill for your information.
What should the driver/floor clearance be? Is their and optimum figure? Or more importantly, what is an "RTA" and where do I get it?
By the way, the boxes are completed. I just have to cover them with plastic laminate - black mat, then I'll be making an active Xover which appeared in Speaker Builder.
Thanks all again,
fred p.
Hi again,
I'm back, and thank-you everyone for the enlightened discussion. The consensus seems to be: Do it if you must, and I must.
DanWiggins said:
Thanks Dan for the info. I calculated the sag factor for the Peerless 12" XLS subs and with an Xmax of 12.5mm, it comes out to 6%. (Their 10" XLS sub comes in at 5.5%.)
I'll be Xing over at approx. 80Hz.
Not that I want to seem to be shunning your advice, I will be setting up the subs as down-firing - 6% is not that far off, and the subs are already bought. An important consideration has to be room size, placement and esthetics, and in my case down-firing is the best compromise.
I will be making a removable base/stand so if it turns out badly I'll be able to revert to front-firing, which brings me to my next question:
BillFitzmaurice said:
Thanks Bill for your information.
What should the driver/floor clearance be? Is their and optimum figure? Or more importantly, what is an "RTA" and where do I get it?
By the way, the boxes are completed. I just have to cover them with plastic laminate - black mat, then I'll be making an active Xover which appeared in Speaker Builder.
Thanks all again,
fred p.
RTA is a Real Time Analyzer; you can download a program for one from the Allen Heath site; alternately just use a test tone CD and sound level meter to check response of the speaker and make the legs what ever length they need to be for best results, usually about four to six inches.
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