sphykik,
Did you ever get this resolved? Figurure out where the strange peak was coming from?
Bill
Did you ever get this resolved? Figurure out where the strange peak was coming from?
Bill
I had some free time and got a chance to take some indoor measurements at a lower volume, from a distance of ~3ft.
I did 4 measurements - L/R with no FIR filters and no EQ engaged, and L/R with FIR filters and the Linkwitz Transform + EQ.
I've included the phase plots as well - it's my understanding that they show that the FIR filters are getting me very close to a flat phase, but it seems I need to make some adjustments?
Left - 3ft - No FIR - No EQ
Left - 3ft -FIR - LT + EQ
Right - 3ft - No FIR - No EQ
Right - 3ft -FIR - LT + EQ
Oddly enough, the giant spike at ~720hz does not appear as present in these measurements. It still exists in the Left speaker (same one I measured outdoors), but it more of a broad hump and is not nearly as severe.
My room has a 12' sloped ceiling and is quite irregularly shaped, so the differences between L/R measurements are not surprising.
There's a major spike at 100hz, and I'm wondering if that can be attributed to overstuffing.
The null at 175-180hz seems like it might be the room, though the same dip can be observed in the outdoor measurement on Page 34.
A few notes about the outdoor measurements:
The prior outdoor measurements were taken at a much higher volume, quite a bit further away from the speaker. I did my best to position the speaker on grass, and point away from any surrounding buildings into the woods, but it seems I may still have gotten reflections off of the pavement or metal storage units. There was an embankment ~20' behind the speaker as well, and this could have also caused some problems.
Next Steps
I think I need to move the Right speaker into the Left position in the room and take another measurements to see if the 720hz peak is a product of the L speaker or its position in the room.
The plumber's putty "waveguide" under the midrange driver could also be an issue.
Depending on your feedback Bill, I may also try removing some of the stuffing to see what happens to the 100hz peak.
I will have the place to my self again this Saturday and will be able to take some more measurements.
Thanks for taking a look!
I did 4 measurements - L/R with no FIR filters and no EQ engaged, and L/R with FIR filters and the Linkwitz Transform + EQ.
I've included the phase plots as well - it's my understanding that they show that the FIR filters are getting me very close to a flat phase, but it seems I need to make some adjustments?
Left - 3ft - No FIR - No EQ
Left - 3ft -FIR - LT + EQ
Right - 3ft - No FIR - No EQ
Right - 3ft -FIR - LT + EQ
Oddly enough, the giant spike at ~720hz does not appear as present in these measurements. It still exists in the Left speaker (same one I measured outdoors), but it more of a broad hump and is not nearly as severe.
My room has a 12' sloped ceiling and is quite irregularly shaped, so the differences between L/R measurements are not surprising.
There's a major spike at 100hz, and I'm wondering if that can be attributed to overstuffing.
The null at 175-180hz seems like it might be the room, though the same dip can be observed in the outdoor measurement on Page 34.
A few notes about the outdoor measurements:
The prior outdoor measurements were taken at a much higher volume, quite a bit further away from the speaker. I did my best to position the speaker on grass, and point away from any surrounding buildings into the woods, but it seems I may still have gotten reflections off of the pavement or metal storage units. There was an embankment ~20' behind the speaker as well, and this could have also caused some problems.
Next Steps
I think I need to move the Right speaker into the Left position in the room and take another measurements to see if the 720hz peak is a product of the L speaker or its position in the room.
The plumber's putty "waveguide" under the midrange driver could also be an issue.
Depending on your feedback Bill, I may also try removing some of the stuffing to see what happens to the 100hz peak.
I will have the place to my self again this Saturday and will be able to take some more measurements.
Thanks for taking a look!
Hi sphykik,
It's a little hard to read your plots' scales. Are those 2dB/division (that's what I'm guessing anyway).
Phase: keep in mind that phase is also a function of distance from the source (or delay, which is the same thing, given the speed of sound). That's why people often talk about "group delay" rather than phase, since group delay is the same shape no matter how much the signal is delayed. Your viewing or measuring software should have a way to adjust the overall delay, remove about 9msec of overall delay from the plots (or adjust for flattest overall phase curve).
The 100Hz peak is in the design not from your stuffing, its an interaction between the driver and the crossover components. Different drivers might do better, but hard to find with good sensitivity and output SPL capability. The peak is in the range where room effects will be dominant, so since you're using MiniDSP for FIR anyway, add a PEQ null there to flatten it out, along with other peaks that the room will contribute.
The null at around 200Hz is ground bounce (also called "Allison Effect"), caused by having two strong paths from the woofers to he mic (one is direct, the other is bounced off the floor or the ground). If you move the speaker up or down from the floor you'll see it move around. You can EQ it a little, but don't try to add more than about 6dB to avoid overdriving woofers or clipping amps. You might not like the sound with that EQ'd out even if you could do it practically, since we are used to hearing nulls in that frequency range and things can sound a little odd without a dip there (most studio recordings are done with the mic close to the instruments so the null is weak in the recordings).
You do seem to have a small bump at around 700Hz on both speakers, not sure what that is from. I played a little with the crossover model, couldn't get that peak by messing with any of the components. Make sure the big midrange inductor isn't close to any of the woofer inductors, and make sure the midrange drivers seal well to the walls of the horn. You could try increasing the value of the larger capacitor in the midrange crossover to bring the bump down a little, but probably it would be easier to just do it in the EQ since you have it (assuming the bump bothers you at all, that is).
Also -- make some measurements a little off-axis (maybe 20 degrees or so off). Directly on-axis overemphasizes any cabinet or horn mouth reflection effects.
It's a little hard to read your plots' scales. Are those 2dB/division (that's what I'm guessing anyway).
Phase: keep in mind that phase is also a function of distance from the source (or delay, which is the same thing, given the speed of sound). That's why people often talk about "group delay" rather than phase, since group delay is the same shape no matter how much the signal is delayed. Your viewing or measuring software should have a way to adjust the overall delay, remove about 9msec of overall delay from the plots (or adjust for flattest overall phase curve).
The 100Hz peak is in the design not from your stuffing, its an interaction between the driver and the crossover components. Different drivers might do better, but hard to find with good sensitivity and output SPL capability. The peak is in the range where room effects will be dominant, so since you're using MiniDSP for FIR anyway, add a PEQ null there to flatten it out, along with other peaks that the room will contribute.
The null at around 200Hz is ground bounce (also called "Allison Effect"), caused by having two strong paths from the woofers to he mic (one is direct, the other is bounced off the floor or the ground). If you move the speaker up or down from the floor you'll see it move around. You can EQ it a little, but don't try to add more than about 6dB to avoid overdriving woofers or clipping amps. You might not like the sound with that EQ'd out even if you could do it practically, since we are used to hearing nulls in that frequency range and things can sound a little odd without a dip there (most studio recordings are done with the mic close to the instruments so the null is weak in the recordings).
You do seem to have a small bump at around 700Hz on both speakers, not sure what that is from. I played a little with the crossover model, couldn't get that peak by messing with any of the components. Make sure the big midrange inductor isn't close to any of the woofer inductors, and make sure the midrange drivers seal well to the walls of the horn. You could try increasing the value of the larger capacitor in the midrange crossover to bring the bump down a little, but probably it would be easier to just do it in the EQ since you have it (assuming the bump bothers you at all, that is).
Also -- make some measurements a little off-axis (maybe 20 degrees or so off). Directly on-axis overemphasizes any cabinet or horn mouth reflection effects.
I would like to build the ported small syn but not with a seos. I would rather build a wooden horn. I have built rectangular tractrix horns before. What would you say about that?
What cf and what about a tractrix flare. Two sides are straight anyway, it would be very easy to put a mid driver on.
What cf and what about a tractrix flare. Two sides are straight anyway, it would be very easy to put a mid driver on.
I guess it would work, but tractrix is a different pattern (that I don't know a lot about other than what I've read). Of course, the crossover would have to be redesigned (probably completely) to do that. There is thread here about someone who made a tractrix synergy.
The seos waveguide seems to load at around 1400hz, wouldn't it be better to have a horn which would be able to load lower. As the mid to low-mid driver crosses at 800hz. A horn that can load an octave below that would be good (400hz) so the crossing over would be smoother. So I think a 200hz or at least an 300hz horn can work. I think I can fit a 2" throat, with a 2" cd 300hz horn in a similar cabinet, add a midrange on top plate and add woofers below like you did.
The Small Syns design is targeted at directivity, loading wasn't much of a concern at all. The efficiency is high enough, SPL capability is more than needed and power is cheap these days anyway. A Synergy horn will load better at low frequencies when driven further up from the throat where the expansion rate is good for lower frequencies (that was one of the main original aims of Danley's Unity design, for high SPL PA use).
Tractrix would work in the same structure, and as you say, the flat sides would make it easier to mount your midranges. But if you're wanting to make your own horn, you can make a conical waveguide even easier than a tractrix, and all walls are flat -- see the SynergyCalc spreadsheet, you can calculate any rectangular flat sided conical waveguide you want.
Tractrix would work in the same structure, and as you say, the flat sides would make it easier to mount your midranges. But if you're wanting to make your own horn, you can make a conical waveguide even easier than a tractrix, and all walls are flat -- see the SynergyCalc spreadsheet, you can calculate any rectangular flat sided conical waveguide you want.
Hi Bill,
I don't think I'd seen this thread before yesterday, but have read it all now and think I'll build a pair for the bedroom next year. I have a couple of other builds to complete first though.
They'll be active using JRiver on my bedroom PC to do the xovers. The one mod, apart from enclosure shape*, will be to add a LAB12 below the sealed Small Syns to do from 80Hz down to 30Hz or so. Each flare will have 2 mids.
Thanks, you've saved me doing my own design. I love the concept as I have Unitys in the lounge/theatre. If I really like them, I'll build 4 more to replace the surrounds.
* Triangular xsection with a chamfered baffle to fit onto the corners.
I don't think I'd seen this thread before yesterday, but have read it all now and think I'll build a pair for the bedroom next year. I have a couple of other builds to complete first though.
They'll be active using JRiver on my bedroom PC to do the xovers. The one mod, apart from enclosure shape*, will be to add a LAB12 below the sealed Small Syns to do from 80Hz down to 30Hz or so. Each flare will have 2 mids.
Thanks, you've saved me doing my own design. I love the concept as I have Unitys in the lounge/theatre. If I really like them, I'll build 4 more to replace the surrounds.
* Triangular xsection with a chamfered baffle to fit onto the corners.
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How much higher up would they roll off (ported version) if moved into the room by 1.5 meters from front and side walls?
IMHO for my preferences all speakers, constant directivity or not have more depth to the soundstage when they're moved off the front walls, I am guessing because of increased front wall reflections.
IMHO for my preferences all speakers, constant directivity or not have more depth to the soundstage when they're moved off the front walls, I am guessing because of increased front wall reflections.
I dunno, you could probably just model it based on Baffle Step formulae and not be too far off. There's little to no directivity to speak of down there at those frequencies, so treat it like just a box.
Probably so. But much of that can be also obtained by some toe in of the horns -- front wall reflection helps to give ambience (only if delayed, hence the need for space behind), but IMO nowhere near as well as if they come from behind or from the sides of you (also delayed of course). Directivity in a speaker can direct energy over paths that take longer to get to you and have similar effect. It's hard to get as strong a delayed reflection from the sides and back without directivity since it is reflected from such a wide range of distances. I think that's why speakers without directivity really need to be out in the room (or else used like headphones!) to get an illusion of depth. More directivity, or ways to better collect the off-axis energy and focus it back delayed can do a pretty good job. In my basement, I use curved diffusors, which create a focused (but diffused!) late reflection, gives gobs of depth. But too large for our little living room.
If you put the small syns out in the room, you'll want to add some BSC. If you aren't religiously averse to EQ (
) , doing that would be a better approach than throwing away all the available power by doing BSC in the crossover.
No template, but the directions and drawings in the PDF are pretty specific and (I think) clear. You can use a woofer itself as the template to draw borders and mark for holes, too.
I've found this type of thinking to be poorly applied to multiple-entry horns (MEHs) with any kind of low frequency extension. Loss of bass doing this using straight-sided horns with mouth sizes of the size of Danley-style MEHs results in a disproportionate loss of bass extension if moved away from a wall or corner position (quarter or eighth space)Originally Posted by jpak
How much higher up would they roll off (ported version) if moved into the room by 1.5 meters from front and side walls?
IMHO for my preferences all speakers, constant directivity or not have more depth to the soundstage when they're moved off the front walls, I am guessing because of increased front wall reflections.
See the Olson article on "A Horn Consisting of Manifold Exponential Sections" to give yourself a clue to what's happening...and see the differences between figures 4,5 and 6 in the Edgar article on tractrix horn profiles, attached.
I've done measurements...and it's a significant loss of bass extension--well over an octave when comparing half space vs. eighth space (on floor vs. in a room corner).
If you're building an MEH that loses mouth polar control at 500 Hz or higher frequencies, then you'll have to rely on something else to provide bass. I see a lot of ported bass bin designs used, but the added effects of port group delay growth and modulation distortion doesn't sound very good to my ears, ref: http://assets.klipsch.com/files/Dope_760600_v15n6.pdf
I rather would recommend something like a closed box/acoustic suspension or perhaps a slot-loaded design for a bass bin--when coupled to the clean sound of a Danley-style MEH.
YMMV.
Chris
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One source for the Olson article on manifold exponential sections mentioned above: Article: A Horn Consisting of Manifold Exponential Sections - Technical/Modifications - The Klipsch Audio Community
