A SLOB acts as a bandpass (LF) device so you will not get very much mids or highs if used for a full range driver.
Hi Eric
I had a thought: why not put the 8" drivers in side-by-side pairs, 6 per side. That will mean 12 drivers per box (so you will have to invest more for another 12 drivers
). The depth of the slot with two 8" drivers side-by-side will not be that much more than the slot depth for a standard 15" driver (and less than the depth for an 18" woofer). That way you will have much less power limiting in the bass. I have attached a side-view illustration to help explain my idea: An externally hosted image should be here but it was not working when we last tested it.
And to further extend this idea, how about mounting the rear pair of woofer on a inward slanting baffle, almost like a pinch at the rear. I have made another illustration, this time with a view from the top. The front of the speaker is on the left side:
An externally hosted image should be here but it was not working when we last tested it.
Enjoy,
Deon
PS. In terms of the tweeters- keep one pointing to the listening position and play with the angle at which the other is pointed upwards. I think that might work better.
Last edited:
Hi Eric
I had a thought: why not put the 8" drivers in side-by-side pairs, 6 per side. That will mean 12 drivers per box (so you will have to invest more for another 12 drivers
An externally hosted image should be here but it was not working when we last tested it.
And to further extend this idea, how about mounting the rear pair of woofer on a inward slanting baffle, almost like a pinch at the rear. I have made another illustration, this time with a view from the top. The front of the speaker is on the left side:
An externally hosted image should be here but it was not working when we last tested it.
Enjoy,
Deon
PS. In terms of the tweeters- keep one pointing to the listening position and play with the angle at which the other is pointed upwards. I think that might work better.
One thing to look out for in this case is the resonance within the slot.
With two 8 inch drivers, you're looking at a slot depth of around 18 inches (16 inches for the cones and at least another extra 2 inches for the frames and spacing). This would mean that you will get resonance at around 190-200hz.
An additional and more problematic resonance will occur along the vertical axis which will be around 27 inches. The resonant frequency in this case is 126 hz. Luckily this can be taken care of by dividing the slot into three separate chambers between each row of drivers.
Just my 2 cents
Regards,
True...but also, if the woofers are flipped cone to magnet there's a mechanical linearity equalization and don't forget mechanical counterbalance so the "secondary hit" is mostly the air velocity. These factors can play a role in distortion reduction.
As most of you know..I use PPSL IBs and listenrs are devastated in the listening room but when they walk back to the storage area where they load in to. They are always surprised at how quite they are. There are other factors like room gain involved but in IB I do hear more loudness in from of the slot over the back.
No, not a bandpass box, since the slot is to small for any real low pass filter function within the intended passband. (If you make the slot long enough you will get a bandpass box with a ragged quarterwave respons from the slot.)
You will get this:
http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
Cheers,
Johannes
You will get this:
http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
Cheers,
Johannes
A friend recently made a SLOB using some 12" GRS woofers and the reports seem to be very positive. He built his in his own unique way. The wings fold, giving a sort of U baffle shape to them.
I have a quad of 18" woofer that normally reside in Hframes but am considering a slot loaded baffle now based on their impressions of their SLOBs. The paper by Papa states "1/3 of combined piston area" is the slot size required. Now if I am using 2 woofer per slot, i would calculate it to be 1/3 of 2*Piston Area of woofer?
How does cone surface area and piston surface area differ?
If I "fold" my wings similar to my friends, how does it affect the dispersion? Does it now become a Ripole?
I have a quad of 18" woofer that normally reside in Hframes but am considering a slot loaded baffle now based on their impressions of their SLOBs. The paper by Papa states "1/3 of combined piston area" is the slot size required. Now if I am using 2 woofer per slot, i would calculate it to be 1/3 of 2*Piston Area of woofer?
How does cone surface area and piston surface area differ?
If I "fold" my wings similar to my friends, how does it affect the dispersion? Does it now become a Ripole?
Yes.
I never really considered the difference, just trusted the published Sd if it was available, approximated it by calculating the area of a disc approximating the outer diameter of the cone. I'm sure you'd come closer to the actual Sd if you calculated the surface area of the cone. I doubt a slot width that's 10% off either way is going to produce significantly different results in a SLOB.
Low frequencies radiate 360deg from wherever they emanate. Slot loading a woofer does not change this principle. But, using a large flat baffle or wings spread wide does approximate half-space placement, like pushing a speaker against a wall... The large baffle becomes the front wall, reflects sound toward the listener, thereby giving a bit of gain over free field placement. If the wings are folded all the way back, since the low frequency sound still radiates 360deg from the slot in front, I'd still expect the wings to reflect sound toward the listener, but they may also reflect more of the sound from the back of the cones into the room as well.
That said, with an open baffle, slot-loaded or otherwise, the purpose of the baffle or wings, (or sides, top and bottom of an open-back box for that matter,) is to reduce cancellation of the front wave you're listening to by the back wave you're not, by lengthening the path between the front and rear surfaces of the cones. Anything that shortens the path sound travels between front and rear will increase cancellation.
I suppose if the wings are folded back all the way against the magnets, you'd add some loading to the rear of the cones as well. The hallmark of the ripole seems to be slot loading BOTH sides. Since neither arrangement is efficient to begin with, and the near-field gain offered by slot loading only the front heavily debated here, why not enjoy the Fs reduction of the ripole by loading both sides?
Thanks for your reply, you answered many of my questions.
My last wonder is whether or not the Slot Loaded design is better suited to smaller woofers than my 18" drivers. I read once someone found they weren't the best sounding option for their larger sized woofers, and preferred the Hframes - which is what I have now.
My last wonder is whether or not the Slot Loaded design is better suited to smaller woofers than my 18" drivers. I read once someone found they weren't the best sounding option for their larger sized woofers, and preferred the Hframes - which is what I have now.
The Visaton Grand Orgue used 18in drivers in a ripole arrangement. I don't think it matters what size driver you use, provided you adhere to the 1/4 - 1/3 Sd size for loading (front only for the Nelson Pass arrangement, or front + rear for dipole)
If you are already happy with the sound of your H-frames, I don't think you're going to improve anything but aesthetics by transplanting the same drivers into a SLOB, or Fs reduction for a ripole.
After all of this fiddling around with 3D models, my rig still consists of a bunch of woofers on a flat baffle, and I'm pretty darn happy. Laziness trumps all
Slot or (flater) H-Frames
NO, it is not.
If you use it like Ripols or W-Pols it isn't - compared to H..U-Frames.
Last year I learned a lot about 1/4 lambda-resonances and I measured slots like U..H..R..W-frames (OK. the first ones have some more volume) getting best results for U..H-dipols in quality and linearity.
With full digital frequency control you can ignore it at all and get some more basement.
LINKWITZ-last-dipol-design is a still the better base.
bg
Wolfgang
NO, it is not.
If you use it like Ripols or W-Pols it isn't - compared to H..U-Frames.
Last year I learned a lot about 1/4 lambda-resonances and I measured slots like U..H..R..W-frames (OK. the first ones have some more volume) getting best results for U..H-dipols in quality and linearity.
With full digital frequency control you can ignore it at all and get some more basement.
LINKWITZ-last-dipol-design is a still the better base.
bg
Wolfgang
I did this and I like it..
Hi
I am pleased that this thread exists. Although I have not gone through all the posts, I wanted to post my pics. This is AER MD3 driver and Eminence 15' woofer... with Firstwatt B5.
Not the deepest bass but you can enjoy the huge soundstage and transparency in a relatively small size OB.
Cheers,
Chul
Hi
I am pleased that this thread exists. Although I have not gone through all the posts, I wanted to post my pics. This is AER MD3 driver and Eminence 15' woofer... with Firstwatt B5.
Not the deepest bass but you can enjoy the huge soundstage and transparency in a relatively small size OB.
Cheers,
Chul
Attachments
I was thinking about building a slot loaded woofer. I have six dynaco a25 woofers and I was wondering if they are suitable? If they are I could easily buy two more and run four per side. Or buy four more and run six per side. If these aren't suitable what would you recommend I buy, keeping it under $50 a unit.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.