I finally did some tuning to my Kallax-sized MEH prototype (described here https://www.diyaudio.com/community/...ty-synergy-speaker.382400/page-3#post-7204894) and will build a second one. Both will be placed on a shelf and the only place for a bass unit / subwoofer is between the two.
The space is for a box of maximum dimensions of 1230 x 330 x 350 mm (WxHxD, around 142 l ext. volume)It could be narrower or shallower, but the height needs to stay exactly 330 mm to be a visual match to the horns.
The shelf has no problem bearing weight, it is a low wardrobe of high quality and strength, custom made. In any case I think that some sort of force - cancelling arrangements would be beneficial for the box not to cause excessive vibrations.
I built an open baffle 2x12 subwoofer (described here https://www.diyaudio.com/community/threads/slob-2x12-subwoofer-for-near-field.384529/page-2) and it would be a quite good fit for the purpose. It was really pumping air through the slot - a normal box would have started jumping already. But it has its problems.
First, its back and sides are open, so this would not be too good close to a wall - or it would not matter much?
Second, I think I made the slot too narrow, there is a peak around 212 Hz that needs heavy EQ - after EQ, it was actually quite a good match to this particular MEH.
Third, it is too high and deep.
I am thinking about a stereo subwoofer with the woofers in internally separated volumes, firing into slots that would be on each end. Due to the mono nature of the lowest frequencies, I should in theory get at least some force cancelling effect where the excursions are the largest.
The height limits me to the use of 10" size woofers. I am looking for 40 - 200 Hz operation, potentially a smooth roll of on the upper end would not matter. Ideally 115 dB capable. A single MEH is already too loud with few watts only, so this is just a reserve mostly. Since a 3 way MEH feeds the bass unit to the horn via a port, this would be like a LEGO-MEH system - for WAF and also portability. Or a large soundbar on steroids. All active with a basic DSP.
So my questions are:
1. Will I get a significant force-cancelling effect with stereo signal below say 150 Hz?
2. What would be the ideal slot width? Any tips for simulation? Height and depth is given by the woofer size.
3. Any woofer suggestions (available from soundimports.nl or TLHP)?
4. would any other enclosure style be better for this application?
Any sort of comments, hints and ideas are welcome. I would be more than happy if I would get the level of bass I got from the 2x12 without the 212 Hz peak in the form factor I described.
The space is for a box of maximum dimensions of 1230 x 330 x 350 mm (WxHxD, around 142 l ext. volume)It could be narrower or shallower, but the height needs to stay exactly 330 mm to be a visual match to the horns.
The shelf has no problem bearing weight, it is a low wardrobe of high quality and strength, custom made. In any case I think that some sort of force - cancelling arrangements would be beneficial for the box not to cause excessive vibrations.
I built an open baffle 2x12 subwoofer (described here https://www.diyaudio.com/community/threads/slob-2x12-subwoofer-for-near-field.384529/page-2) and it would be a quite good fit for the purpose. It was really pumping air through the slot - a normal box would have started jumping already. But it has its problems.
First, its back and sides are open, so this would not be too good close to a wall - or it would not matter much?
Second, I think I made the slot too narrow, there is a peak around 212 Hz that needs heavy EQ - after EQ, it was actually quite a good match to this particular MEH.
Third, it is too high and deep.
I am thinking about a stereo subwoofer with the woofers in internally separated volumes, firing into slots that would be on each end. Due to the mono nature of the lowest frequencies, I should in theory get at least some force cancelling effect where the excursions are the largest.
The height limits me to the use of 10" size woofers. I am looking for 40 - 200 Hz operation, potentially a smooth roll of on the upper end would not matter. Ideally 115 dB capable. A single MEH is already too loud with few watts only, so this is just a reserve mostly. Since a 3 way MEH feeds the bass unit to the horn via a port, this would be like a LEGO-MEH system - for WAF and also portability. Or a large soundbar on steroids. All active with a basic DSP.
So my questions are:
1. Will I get a significant force-cancelling effect with stereo signal below say 150 Hz?
2. What would be the ideal slot width? Any tips for simulation? Height and depth is given by the woofer size.
3. Any woofer suggestions (available from soundimports.nl or TLHP)?
4. would any other enclosure style be better for this application?
Any sort of comments, hints and ideas are welcome. I would be more than happy if I would get the level of bass I got from the 2x12 without the 212 Hz peak in the form factor I described.
I do not want to look like I am talking to myself, but a slightly modified "short" version of https://www.diyaudio.com/community/threads/light-as-air-slot-loaded-band-pass-sub.258433/ by tb46 could be fit in the place - actually, a pair of them.
Another option would be to build two 2x10" sealed boxes. The only way to get force cancelling would be to put one woofer at the front and the other to the back - the back woofer would be some 5 cm close to the back wall. Would that be an advantage or a problem?
Maybe even a cardioid arrangement with two woofers at the front and one at the back - I have one extra channel of amplification and DSP to use. Would that be of any benefit when so close to the wall?
By the way, the wall is a solid brick wall as all other walls in this room.
Maybe even a cardioid arrangement with two woofers at the front and one at the back - I have one extra channel of amplification and DSP to use. Would that be of any benefit when so close to the wall?
By the way, the wall is a solid brick wall as all other walls in this room.
Assuming I follow, seems like a pair of these dipole BP6P facing each other and wired in phase might be the best option overall, though presumably will require some empirical design work and/or learn AkAbak to get the optimal front, rear slot loading.
Thanks! This is exactly the kind of feedback I like - opening some options.
These look interesting, I was investigating them too. It would be a very simple build, but I have really zero idea on how to simulate these.
I think the best will be to make a chamber with interchangeable front and back and maybe an extra spacer or two. And I could start with the 12" woofers I already have.
So you mean to build two boxes like this and tie them mechanically face to face and point the resulting slot between them to the front?
These look interesting, I was investigating them too. It would be a very simple build, but I have really zero idea on how to simulate these.
I think the best will be to make a chamber with interchangeable front and back and maybe an extra spacer or two. And I could start with the 12" woofers I already have.
So you mean to build two boxes like this and tie them mechanically face to face and point the resulting slot between them to the front?
The problem to face is the space between woofers or depth of the manifold. You can use them up to below 1/4 wavelength of either depending onthe design. I use two 15s in a manifold that has an 18" depth, due to being mounted behind a wall. I have to cross below 100hz. Smaller woofers mounted on either side of a box or a shorter manifold will get you higher.
The depth of the manifold is not a problem with these dimensions. My 12" slot loaded with open back was ca 32 cm deep, so the upper frequency would be around 270 Hz. I had a resonance at 212 Hz, which was most probably related to the slot area being too small - and front bandpass volume being too small as well.
200 Hz 1/4 WL is 43 cm. Maximum dimensions for the slot are 33 cm height and 35 cm depth (minus walls). A pair of 10" should work, I need to run some simulations.
By the way, simulating the PPD as BP6P in Hornresp provided some really strange results.
200 Hz 1/4 WL is 43 cm. Maximum dimensions for the slot are 33 cm height and 35 cm depth (minus walls). A pair of 10" should work, I need to run some simulations.
By the way, simulating the PPD as BP6P in Hornresp provided some really strange results.
As soon I tried this configuration (2 woofers if the same closed box), I adopted it. The crossover is a BUT3, 250 Hz. The back woofer is at less than 1 ft from the wall. It's worth to test it.
Cool, thanks for the heads up! Maybe the simplest thing will be the best?
I tried investigating slot loading. What would be the suitable T/S parameters for that?
I tried investigating slot loading. What would be the suitable T/S parameters for that?
Some quick sims did not show what I expected. Nevertheless, I have my parametric CAD model and will cut some chipboard, just after revisiting the 2x12 SLOB build - I will try to give it a second chance in this room. The woofers will be recycled for this BP6P dipole and simple closed box experiments, maybe even with slots at the ends. Good to keep me busy in the next few months🙂
It seems that the slot does not really do anything I need. A pair of 12" woofers in a sealed box with a bit of EQ will what I need the same or better. So that is definitely something that needs to be tried as well🙂
I use this woofer https://hadex.cz/q340-repro-310mm--12-subbasovy-dualni-2x4ohm---250w-rms/ , TS parameters here: https://hadex.cz/spec/q340.pdf
It has reasonable fs, Vas and Qts and is not expensive at all (equvalent of around 40 USD). Its only weak point is the stamped basket, it seems to be a bit weaker than I would like. On a baffle it is stiff enough though.
It has reasonable fs, Vas and Qts and is not expensive at all (equvalent of around 40 USD). Its only weak point is the stamped basket, it seems to be a bit weaker than I would like. On a baffle it is stiff enough though.
Yeah, see no difference to wall or floor loading a driver; more than theoretical, 'squeeze' it till it 'whistles' so to speak and back off a bit and get some free extra BW, dynamic headroom.
The 2x12 SLOB is not too bad. I tried to measure how loud am I listening and at an already slightly uncomfortable level, I got a peak reading of 112 dB at the listening spot (2 m away, boxes 1.8 m apart). It was mostly the bass that gave these peaks. I was already overdriving the amp in the bass channel at times (75 W into 4 ohms). With the EQ set now, a single bass module should be safely below X-max and well below XDamage to 28.3 V, which means I need to use a more powerful amp and doubling up the driver surface will not hurt either. The bass from the SLOB is nicely clean and kicking without any "mud", it seems to be matching the Kallax MEHs pretty well, the level meter at the amp was showing usually at least 10 dB below the bass channel, so they will be safe and hardly sweating even at these levels. I hope the sealed box (with EQ) will be as good as the SLOB but without the anoying 220 Hz peak.
