I'm building 4 bucket subs to run in stereo pairs; they'll be wired in parallel so their amp can see 4 ohms a side.
I'm debating whether or not to install a DPDT toggle switch in each bucket to be able to reverse phasing 0/180 degrees. I realize I could just reverse the stacked banana plugs at the back of the amp but since I have 4 switches ready to go I am wondering how desirable this might be.
One extra consideration: Since each pair will be wired in parallel---both speakers will need to be switched to the same setting simultaneously---otherwise the cross-connection would effectively short them out, right?
So while I could accomplish the same results by reversing both banana plugs in the amp (powered off) ; it might be a bit easier to flip two or four switches instead for quicker comparisons.
I have little idea how much of a difference there might be between two pairs of subs in regards to 180 degrees but since my crown xls amp doesn't have a phase switch I am considering this option.
Any comments will be appreciated.
I'm debating whether or not to install a DPDT toggle switch in each bucket to be able to reverse phasing 0/180 degrees. I realize I could just reverse the stacked banana plugs at the back of the amp but since I have 4 switches ready to go I am wondering how desirable this might be.
One extra consideration: Since each pair will be wired in parallel---both speakers will need to be switched to the same setting simultaneously---otherwise the cross-connection would effectively short them out, right?
So while I could accomplish the same results by reversing both banana plugs in the amp (powered off) ; it might be a bit easier to flip two or four switches instead for quicker comparisons.
I have little idea how much of a difference there might be between two pairs of subs in regards to 180 degrees but since my crown xls amp doesn't have a phase switch I am considering this option.
Any comments will be appreciated.
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True; hadn't considered that but the switches are pretty heavy duty.
I'm still mulling it over while the concrete cures over the next three or four days, then I'll "sew them up" and finish things.
Wondering about how much difference switching the phase of the different channels makes; I'm leaning towards just using the banana plug reversal method and being done with it.
I'm still mulling it over while the concrete cures over the next three or four days, then I'll "sew them up" and finish things.
Wondering about how much difference switching the phase of the different channels makes; I'm leaning towards just using the banana plug reversal method and being done with it.
An infinitely variable phase dial 0-180 deg I have always found far more "tunable" than a simple switch that never seems to get it right unless you're prepared to rearrange your listening room to suit that limited amount of "control" but with 4 of the little beasties you may not notice any phase issues at all. With correct positioning the standing waves in room can be killed dead and the bucket bass dress inappropriately at their funeral but phase not so sure. That may require DSP I say try as is and add only if necessary.
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Excellent post, audiopath and I think you are on to something about killing room modes with 4 scattered around the room. We have a lot of furniture, racks, tables, carpets that also must help to begin with. My workshop/den which is the small part of our L-shaped listening room even has an old couch turned on its end in the far corner to act as a makeshift bass trap, too.
Not having a phase tuning control on my amp is the reason I was considering the switches but your remarks totally reinforce what I was thinking---probably would not make enough difference to notice anyway. If it was only one or two subs then yes, it might---but the reason I decided on four was to make the system more efficient and mode-killing from the get-go.
Thanks to your reply I have decided to skip the switches---I can always reverse the plugs when/if I feel the need to experiment.
Yes, I am going to do a little writeup once all four subs are up and running (expect late next week) and I am taking pictures throughout my building process. This is so much fun and I am looking forward to the results!
Not having a phase tuning control on my amp is the reason I was considering the switches but your remarks totally reinforce what I was thinking---probably would not make enough difference to notice anyway. If it was only one or two subs then yes, it might---but the reason I decided on four was to make the system more efficient and mode-killing from the get-go.
Thanks to your reply I have decided to skip the switches---I can always reverse the plugs when/if I feel the need to experiment.
Yes, I am going to do a little writeup once all four subs are up and running (expect late next week) and I am taking pictures throughout my building process. This is so much fun and I am looking forward to the results!
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Right, top to bottom.
Let's talk about how to install your subs. First you take one sub and move it around to find four best locations using REW and a mic at your chair with nothing but the single sub playing.
You put all he speakers in place and then you get all the main and sub speakers playing REW sweeps. Then you reverse phase each sub one by one and see the effect. Not possible to predict ahead of time.
If having switches makes that materially easier, go for switches.
As theaudiopath says, a lot more possibilities using a DSP that adjusts phase and time/distance, such as the Behringer DCX2496 that no audio system should be without.
Ben
Ben,
Switches change polarity, not phase.
To adjust the phase requires a delay, the delay can be analog, digital or use FIR filters, which can also correct the phase of the speaker(s) to match the original signal.
Art
Ben; Thanks for outlining the proper way to set things up. I won't really be able to enjoy that method, however. Due to a fairly full, almost cramped living room area in our two-story townhouse I have very little leeway in placement.
One will go slightly left of the left mains in a short corner next to the kitchen (the wall comes 24" before becoming the kitchen area, the second will be to the right and also behind the right mains near a diagonal corner where the fireplace is. The third and fourth will be to the left and right of my listening position behind the couch or roughly adjacent to it.
Since I posted this question I've decided to revert to the original plan of bridging the output of the Crown sub amp and run all four mono in series/parallel to present an 8-ohm load (in parallel they'd present a too-low-for-my-amp 2-ohm load). I've been told by the sub's designer that they will integrate much better if run in mono and they like lots of current, too.
The way I am going to wire them also will allow little room for placement variation, too. I will be using one length of 12-2 jacketed cable that I'll "tap into" at each speaker or amp binding post (all banana jacks/dual plugs) by cutting a bit of jacket away at the connection point, cutting one wire on one side so as to provide a series connection on each pair of subs and a parallel connection at the amp. Tricky to explain but easier to visualize if I could post a sketch (which I could do later if requested).
Anyway, I'll add a little extra length between the cable taps so at least two or three of them could be moved a foot or two one way or another to provide a minor bit of adjustment. I will also put one sub atop a low end table as I've read that elevating at least one sub in a swarm helps tame room modes further.
While I have a DXC2496 and Ultra-Drive Pro I am currently using it in the tri-amp mode with my mains. Their output goes into a 6-channel volume control and then into my Adcom 6006 6-channel amp.
When I add the subs I will use the high-level (speaker)LF outputs via a "Magic Cable" recommended by the bucket sub's designer, Ed Schilling to feed the bridged Crown's left line in jack. (The Magic Cable is basically a Y-cable with two 680-ohm resistors going to the hot sides to buffer things. The reason Ed suggests this arrangement is to provide the Crown a higher input as the XLS series require a hefty signal for best performance). The Crown is also equipped with its own 24db/octave crossover so I can fiddle with the crossover point for these subs (probably will xover somewhere between 59-90 Hz as far as I can see now).
I also have a microphone that can be used with the Behringer gear to set things up and while I haven't tried that for years I will probably get out my manuals and read up on how to go about that again. I built my mains (OBs similar to the Orions) in 2005 and have since gotten more than a little rusty with all of this technical stuff. I don't have REW but I believe it is freeware so I may look into that as well---but I'm the kind of guy (old and lazy) that if the system makes me smile when I fire it up the first time then I'll probably leave well enough alone from then on. If not, I'll get out the Behringer manuals and start pulling out what few hairs I have left on my head...
Art; A bit confused by your statement---and I really should know this for sure already (I hold an Extra Class amateur radio operator license which requires a fair amount of electronic knowledge to begin with)---but wouldn't a DPDT switch automatically reverse the phase 180 degrees by reversing the polarity? Isn't reversing polarity the same as reversing phase? True that one cannot adjust phase with a switch but my original question is dealing with at least having a convenient way to reverse the phase only, no adjustment. The Crown XLS amp's one drawback over a standard sub plate amp is that there is no such switch or phasing control, hence the idea of installing switches.
All a moot point now as I will be wiring them in a different manner now---and I may be able to adjust the phasing after all via the Behringer---thanks anyway to everyone who provided me further information here---most helpful!
Thanks again,
Jeff, NH7RO
One will go slightly left of the left mains in a short corner next to the kitchen (the wall comes 24" before becoming the kitchen area, the second will be to the right and also behind the right mains near a diagonal corner where the fireplace is. The third and fourth will be to the left and right of my listening position behind the couch or roughly adjacent to it.
Since I posted this question I've decided to revert to the original plan of bridging the output of the Crown sub amp and run all four mono in series/parallel to present an 8-ohm load (in parallel they'd present a too-low-for-my-amp 2-ohm load). I've been told by the sub's designer that they will integrate much better if run in mono and they like lots of current, too.
The way I am going to wire them also will allow little room for placement variation, too. I will be using one length of 12-2 jacketed cable that I'll "tap into" at each speaker or amp binding post (all banana jacks/dual plugs) by cutting a bit of jacket away at the connection point, cutting one wire on one side so as to provide a series connection on each pair of subs and a parallel connection at the amp. Tricky to explain but easier to visualize if I could post a sketch (which I could do later if requested).
Anyway, I'll add a little extra length between the cable taps so at least two or three of them could be moved a foot or two one way or another to provide a minor bit of adjustment. I will also put one sub atop a low end table as I've read that elevating at least one sub in a swarm helps tame room modes further.
While I have a DXC2496 and Ultra-Drive Pro I am currently using it in the tri-amp mode with my mains. Their output goes into a 6-channel volume control and then into my Adcom 6006 6-channel amp.
When I add the subs I will use the high-level (speaker)LF outputs via a "Magic Cable" recommended by the bucket sub's designer, Ed Schilling to feed the bridged Crown's left line in jack. (The Magic Cable is basically a Y-cable with two 680-ohm resistors going to the hot sides to buffer things. The reason Ed suggests this arrangement is to provide the Crown a higher input as the XLS series require a hefty signal for best performance). The Crown is also equipped with its own 24db/octave crossover so I can fiddle with the crossover point for these subs (probably will xover somewhere between 59-90 Hz as far as I can see now).
I also have a microphone that can be used with the Behringer gear to set things up and while I haven't tried that for years I will probably get out my manuals and read up on how to go about that again. I built my mains (OBs similar to the Orions) in 2005 and have since gotten more than a little rusty with all of this technical stuff. I don't have REW but I believe it is freeware so I may look into that as well---but I'm the kind of guy (old and lazy) that if the system makes me smile when I fire it up the first time then I'll probably leave well enough alone from then on. If not, I'll get out the Behringer manuals and start pulling out what few hairs I have left on my head...
Art; A bit confused by your statement---and I really should know this for sure already (I hold an Extra Class amateur radio operator license which requires a fair amount of electronic knowledge to begin with)---but wouldn't a DPDT switch automatically reverse the phase 180 degrees by reversing the polarity? Isn't reversing polarity the same as reversing phase? True that one cannot adjust phase with a switch but my original question is dealing with at least having a convenient way to reverse the phase only, no adjustment. The Crown XLS amp's one drawback over a standard sub plate amp is that there is no such switch or phasing control, hence the idea of installing switches.
All a moot point now as I will be wiring them in a different manner now---and I may be able to adjust the phasing after all via the Behringer---thanks anyway to everyone who provided me further information here---most helpful!
Thanks again,
Jeff, NH7RO
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Jeff,
A polarity reversal reverses the phase 180 degrees at one frequency, the phase of a loudspeaker may vary hundreds, or even a thousand (or more) of degrees over it's range of operation.
A polarity reverse may help if the top speaker happens to be 180 degrees off in the crossover region, such as a bass reflex (phase inversion) speaker with it's Fb (tuning frequency) near that of the crossover to a sealed sub.
Another example of a polarity flip "working" would be if the time of flight of a folded horn happens to be the same time constant as one wavelength at the crossover frequency, the folded horn audio will lag the sealed top by one wavelength (360 degrees), but will be "in phase", just like the phase inverted port output of a BR cabinet is in phase with front wave.
Each "pole" of a crossover adds 90 degrees of phase lag in addition to that of the speaker, a 24 dB per octave crossover adds 360 degrees of phase shift.
FIR filters are the exception to the above, properly implemented, they can eliminate "phase wrap", resulting in an output signal that mimics the phase of the input signal, though the FIR filter requires a little time to accomplish that, the amount of time determined by the lowest frequency that is decided to be made "flat phase".
Art
Jeff - even with a usual layout, good to compare polarities. Incomprehensible to some, but you really might find the "wrong" polarity to work better in your room. Might not justify adding a switch assembly.
Barely any sound difference between mono and stereo subs, if crossover is below say 120 Hz. If subs are clean and xcover sharp, can be put anywhere in room, mono or stereo driven.
I always take for granted than non-tube amps so much reserve, they can take any connections except for very low impedance load. So that's your last constraint. Amps are so clean and bridging so complicated and prone to error, why bother bridge?
The statistical benefits of heterogeneity in all ways possible (like your coffee table example) helps combat room modes. Few other tools available.
I too use a 4-pot volume control downstream of my AES-fed DSP. All digital and all bits all the time are upstream of the ganged VC.
Even for those unfamiliar with Toole's critique of room EQ, if you do two runs with the Behringer, you get disparate tunings. There are expensive auto tune systems but better to explore with REW.
I think the reason Art goes into his picky schoolmarm tirade about phasing and polarity is because he rarely has an opportunity to lecture and be patronizing to somebody who taught in an engineering faculty, ahem, ahem. Let him enjoy his big moment of glory.
Ben
Barely any sound difference between mono and stereo subs, if crossover is below say 120 Hz. If subs are clean and xcover sharp, can be put anywhere in room, mono or stereo driven.
I always take for granted than non-tube amps so much reserve, they can take any connections except for very low impedance load. So that's your last constraint. Amps are so clean and bridging so complicated and prone to error, why bother bridge?
The statistical benefits of heterogeneity in all ways possible (like your coffee table example) helps combat room modes. Few other tools available.
I too use a 4-pot volume control downstream of my AES-fed DSP. All digital and all bits all the time are upstream of the ganged VC.
Even for those unfamiliar with Toole's critique of room EQ, if you do two runs with the Behringer, you get disparate tunings. There are expensive auto tune systems but better to explore with REW.
I think the reason Art goes into his picky schoolmarm tirade about phasing and polarity is because he rarely has an opportunity to lecture and be patronizing to somebody who taught in an engineering faculty, ahem, ahem. Let him enjoy his big moment of glory.
Ben
Oh, boy, Ben, just when I thought I've finally had this all figured out and was ready to set up... Now I'm back to fully undecided.
I believe what you're saying is sound advice (no pun intended) but I also think that Ed's bucket subs perform as well as they are reported to because of his strong encouragement to use his methods of feeding the amp and running mono instead of stereo (and he xovers his buckets at 59Hz, IIRC). He says he doesn't know why they work so well but he says as long as they are set up his way they will not disappoint.
Anyway, I'll mull the whole thing over some more while the concrete is curing a few more days. I've got to fabricate a couple of rack brackets and make up some interconnects in the meantime, too.
I appreciate your advice even though it is almost contrary to Ed's. Taking a break now to have lunch and think about my plans now.
Regards, Jeff
I believe what you're saying is sound advice (no pun intended) but I also think that Ed's bucket subs perform as well as they are reported to because of his strong encouragement to use his methods of feeding the amp and running mono instead of stereo (and he xovers his buckets at 59Hz, IIRC). He says he doesn't know why they work so well but he says as long as they are set up his way they will not disappoint.
Anyway, I'll mull the whole thing over some more while the concrete is curing a few more days. I've got to fabricate a couple of rack brackets and make up some interconnects in the meantime, too.
I appreciate your advice even though it is almost contrary to Ed's. Taking a break now to have lunch and think about my plans now.
Regards, Jeff
I made an important scientific discovery early in my audio research career... when I was studying highway noise abatement. I found one and only one kind of fence that worked all the time counter-acting highway impingements: the fence you build yourself.
Why am I not surprised that Ed's speakers work so well.... for him.
If you're crossing over at 59 Hz, the room modes are almost the only game in town.
B.
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NH7R0 I will add my experience contradicts some advice above.
I run 2 12in Peerless bass bins off 1 plate amp 125 litre sealed.
I have found in my 4×8 Metre +2.5 × 4 M x 2.4 M high open plan kitchen that positioning is critical. I also found 2 subs is WAY better than one The only way to find out is as Arnie would say "Kahm Ahn You Kahn DO IT!" Hook em up and let the subs tell you what they need. In theory to my understanding if the rear subs have the same firing distance to your ears as the front speakers/subs all should be sweet. BUT as we all know and as I've experienced your milage may vary in reality. I'm a novice that is constantly learning but I learn quick. Superb bass is one of the hardest things to get right. I'm not there yet by any means but each discovery and inprovement means I'm enjoying the journey.
I run 2 12in Peerless bass bins off 1 plate amp 125 litre sealed.
I have found in my 4×8 Metre +2.5 × 4 M x 2.4 M high open plan kitchen that positioning is critical. I also found 2 subs is WAY better than one The only way to find out is as Arnie would say "Kahm Ahn You Kahn DO IT!" Hook em up and let the subs tell you what they need. In theory to my understanding if the rear subs have the same firing distance to your ears as the front speakers/subs all should be sweet. BUT as we all know and as I've experienced your milage may vary in reality. I'm a novice that is constantly learning but I learn quick. Superb bass is one of the hardest things to get right. I'm not there yet by any means but each discovery and inprovement means I'm enjoying the journey.
Ben,
Your "important discovery" explains why you seldom bother to examine "picky tirades" such as the difference between specific audio terms and their distinctions.
Have fun on your continued journey of living behind the fences you built back when you taught in an engineering faculty, ahem, ahem.
If you think my explaining the difference between phase and polarity was my "big moment of glory", you both overestimate my opinion of you, and underestimate the many accomplishments in the audio field I have enjoyed, and look forward to continue to enjoy.
By the way, I have been running subs from bridged mono amplifiers for the last six years since I started using drivers that can use the additional 6 dB power that configuration provides, which is no more complicated than a polarity reversal on one input, and attaching the "+" and "-" speaker terminals to the L/R "+" terminals.
Cheers,
Art
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Is there anyone besides weltersys who didn't get my joke that it really isn't any kind of "important scientific discovery" to find people think their DIY projects are great successes?
But I'll stick with the story. I recommended to my clients (a Department of Transp.) that they give "highway neighbours" grants to build their own fences. That way, lots of people would be real happy with the results. But if the government built berms and good fences, nobody would ever think they did any good*.
Pity more DIYers don't recognize the need for blind testing.
Ben
*and in our acoustic field tests, it was pretty clear there really ain't much you can do about highway noise with a fence.
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I read through quickly so forgive me if it's already been mentioned, but I though the only "pat" reason for wanting sub phase reversal is to meet up with co-located mains with ported midbass, where output at cutoff is around 180 degrees out of phase. Of course as soon as sub locations differ greatly from the main speakers the combined response at yet some other position is anyone's project...
Oh, I got it, and I'm pretty sure weltersys got it too.
I think weltersys' totally true observation that you routinely discount real technical information, mock and personally attack the people that present it without any trace of technical response from you was a lot more amusing than your joke though.
I'll counter your story with one of my own.
I live 10 km from Highway 401. In the calm of night the highway noise is very audible from my house when I'm outside.
I have friends that live in Sarnia, their property backs onto highway 402 (same speed limit as 401). A simple concrete fence is all that separates their back yard from highway noise (or wayward vehicles). Their house is about 200 feet from the highway. Every time I go there I find myself staring at that fence in disbelief due to it's uncanny ability to block noise.
The noise at their house which is 200 ft away from the highway isn't that much louder than the noise at my house 10 km away from the highway. Sure, it is significantly louder, but not nearly as much as you might expect.
As my story above illustrates, there's a LOT you can do about highway noise with a fence. Highway noise (the annoying parts of highway noise anyway) are pretty high in frequency. High frequencies are fairly directional and easily reflected.
A simple glance at reflection data for a variety of different products should be all that was needed to conclude that fences can be very effective, and to narrow down a specific product to build the fence with.
As long as the fence is built with a solid reflective material that's high enough you can easily block most of the noise. This shouldn't have required a study, it common sense.
And this again leads back to the point that constantly offering your resume in lieu of technical data is not an argument. Despite the fact that you may have taught engineering and worked at Bell Labs (in a non scientific occupation), you are frequently very incorrect in your understanding of basic audio theory and concepts.
Art; I believe that additional 6db is the reason Ed is adamant about bridging the Crown and running all of them in mono---the little Peerless 830667s love gobs of power. Even at a combined impedance of 8 ohms the XLS2502 can dump 1550 watts if needed.
Of course, living in a condo with neighbors on both sides makes the complete road test of this highly unlikely.
As we all well know, the damping factor of a big amp is an essential part of things here and I am leaning towards fabricating a buffered Y cable so I can feed my amp with a mono signal and take the "bridge to bassland."
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