Regarding the thd discussion, I think the angle that isn't being said plainly; Why would you ever design towards caring about thd in the first place. Isn't the opposite, the goal. Designing towards minimal excursion, in particular, its already been discussed in @b_force's thread that driver touching midrange should stay 2x about Fs or within 1-2mm........ so where is there ever a need to consider Thd except for a bad design... lol I'm one to talk right? I'm trying to squeeze a 200hz xo out of my horn+tweeter. In my defense, I am above the horns f6 and my efficiency/headroom is really high. So thd might be a concern for someone trying to push the limits... but, pushing the limits, in a lot of peoples opinion is bad designing in particular if they perceive no worthy benefits actually the opposite is true, as in, lowering the excursion to a non consequential amount.
I'd be interested to see the FR of this woofer to compliment this measurement
I have drivers with original cones that are about 60 years old. Done re-foams close to 40 years old original cones. Never once saw a cone out of round or misshapen that was noticeable by eye.
That said the spiders are another issue depending on overall suspension stiffness. Driver storage can be a real challenge depending on MM vs stiffness. I remember old recommendations to periodically rotate drivers to avoid sag. That's in the way-back machine 60's 70'S
With modern drivers? I couldn't say for sure but think probably not.
Just my 2 cents!
Rob 🙂
Been there, done that and still do for drivers with doped surrounds for many decades as it's less hassle IME than getting it evenly rearranged/replaced. Other drivers have been stored face up, down, vertical with no obvious problems, so IME it's whatever 'floats yer (your) boat'. 😎
For horizontal mounted speakers, cone sag can be a very big deal.
https://www.diyaudio.com/community/...nimim-clearance-to-floor.385000/#post-6992295
This 10" speaker forward offset almost equal to it's Xmax.
It hammered the horn's phase plug and destroyed the cone.
In a subwoofer, there is no phase plug to hit, but the offset could easily get to the point where excursion is affected, and Xlimit hit on the downward half of the cycle, which sounds awful.
Every speaker I've owned mounted facing up or down has visible sag over time.
Art
OK I did some sims to help me see some potentials, The above row of graphs show a forward facing woofer on the front baffle in combination with additional woofers, no filtering, no delay, just to see how well they played together. The lower row of graphs show the same with no room included... The yellow line is the room response and in the lower row, I view the yellow and blue lines as a sort of anechoic, phase aligned example of the responses.
Below is what a representation of the Dampened PPSL slot facing the corner with a front firing woofer on the now front baffle IF lower pic which includes no room and potential fulling summing is near reality, thats not bad at all
With some time alignment via delay I can produce this
Otherwise the facing woofer with side mounted woofers seem to take the cake, which is not surprising. I think the rear facing PPSL is a option as the coupling will be strong due to close proximity and the point source created by the close proximity will be easier to dial in phase, using just one stereo dsp/amp.
Basically that area on the back of the box in this pic, can become the front baffle with a forward facing woofer on it... With the addition of another panel, the dept is enough. There is a bit of bracing in the area, but where theres a will theres a way. I think think that I am really just going the extra mile to remove any unwanted resonance the slot my introduce, with the added benefit of crossing higher if ever desired, not convinced its 100% needed but theres wondering about the slot resonances effect on the sound, however small, if they are simply, not there.... @gedlee looking at you 🙂
@gedlee I can't understand how you are ok with a non symmetrical setup, it would drive me wild. I still stand firm that I can locate subs in a small room.
Below is what a representation of the Dampened PPSL slot facing the corner with a front firing woofer on the now front baffle IF lower pic which includes no room and potential fulling summing is near reality, thats not bad at all
With some time alignment via delay I can produce this
Otherwise the facing woofer with side mounted woofers seem to take the cake, which is not surprising. I think the rear facing PPSL is a option as the coupling will be strong due to close proximity and the point source created by the close proximity will be easier to dial in phase, using just one stereo dsp/amp.
Basically that area on the back of the box in this pic, can become the front baffle with a forward facing woofer on it... With the addition of another panel, the dept is enough. There is a bit of bracing in the area, but where theres a will theres a way. I think think that I am really just going the extra mile to remove any unwanted resonance the slot my introduce, with the added benefit of crossing higher if ever desired, not convinced its 100% needed but theres wondering about the slot resonances effect on the sound, however small, if they are simply, not there.... @gedlee looking at you 🙂
@gedlee I can't understand how you are ok with a non symmetrical setup, it would drive me wild. I still stand firm that I can locate subs in a small room.
lol, Yeah I'm definitely in a scared straight, or should I say, scared vertical facing, type of way. Still my; water takes the path of least resistance combined with plinko style approach to design seems to continue to pay off.
Placing the slot loaded woofers to the back, Dampening them, low passing them, separately amp/dsp'ing them is a good path. With 3 18's playing on a channel, the front woofer can play without high pass, hand off to the horn, and maintain minimal excursion.
According to Rew and Virtuixcad, Deep in the corner produces a good FR, The front of the cabinet is still deep enough in the corner to create smooth FR within the passband.
Last edited:
Devils advocate;
Place 3rd woofer facing forward into current slot, with modifications to shortern path of forward most radiating surfaces to rear of slot
Use 3rd woofer to create a mtm, Ppsl on bottom, front facing woofer on top.
Place 1 woofer front faced with a slot on each side, immediate to that woofer, for the other 2 woofers.
🧐
Place 3rd woofer facing forward into current slot, with modifications to shortern path of forward most radiating surfaces to rear of slot
Use 3rd woofer to create a mtm, Ppsl on bottom, front facing woofer on top.
Place 1 woofer front faced with a slot on each side, immediate to that woofer, for the other 2 woofers.
🧐
That is not my experience. Certainly under certain unique conditions this is possible, but for complex music I have no sense of where my subs are located.
These some sweeps I did in Rew at my listening position, left channel, left ear position
turkey .25 windowing except the green one, I did by manually sweeping and recording the peak use the spectrum analyzer using 64k ff.
Theres some type of high pass filter, I'm not looking at it at the moment. The graphs are not smoothed.
Is this so bad for stereo subs?
Seems like DSP would clean this pretty easily?
Last edited:
Looking at phase, the low end seems pretty solid. That doohickey above 200hz sucks but what an improvement over the initial measurements in that area. carpet for a floor baffle did good. I think with a purposely placed dampener things could shape up more desirably through the low midrange.
I don't think that phase response has much meaning at these low frequencies. The "doohickey" at 200 Hz is due to the LP filter - its right on the edge of 180 degree phase.
Thanks! If I may ask, what criteria did you use to select the woofer for the NS15?