Nope. No control of the backwave at all.
As you deduced the Xo will be mechanical in that the woofer rolls off at ~3k and the 2 inch will roll off below 2500.
The trick is that few would make a driver that rolls off above such a low FR. Even a PA woofer will have usable response to 3500 and that is too high.
A 3inch driver lowers the FR but this drags the SQ oscillations down in to the audible range, if no baffle is used.
800-1500hZ would be ideal, but since the ideal is often not attainable then a small circular baffle for the 2 inch will bring the FR SQ up so that it more smoothly transitions to the woofer.
So I suppose the Xo would be the tweeter baffle and the drivers selected for their FR and the no woofer baffle.
You can get a natural acoustic crossover for the woofer by putting a smaller aperture over it with a spacer to form a compression chamber. Tune this to match the baffle width controlled bass falloff from the fullrange. Typically around 400Hz is very achievable with standard width baffles.
Well, if you compare a 3" diam. Speaker to a 15" one, you can call the 3" a tweeter. The 15" s
dustcap might be bigger !
I usually call things with their names. SQ I suppose is sound quality and FR is frequency response.
Power limits are power limits and excursion in a given passband is EIAGPB 😛
Modulation is Modulation, ignoring those things and also the advantages offered by simple electr7cal means such caps and coils...s8rry, inductance and capacitance in series before a transducer, can make you go in circles....
Also ignoring what (where) the back wave does (goes) is funny, don't you think ?
dustcap might be bigger !
I usually call things with their names. SQ I suppose is sound quality and FR is frequency response.
Power limits are power limits and excursion in a given passband is EIAGPB 😛
Modulation is Modulation, ignoring those things and also the advantages offered by simple electr7cal means such caps and coils...s8rry, inductance and capacitance in series before a transducer, can make you go in circles....
Also ignoring what (where) the back wave does (goes) is funny, don't you think ?
I hope you realize that the directivity of the 15" at 3 khz and the 3" at 3 khz is no where near the same so they will not merge nicely.
Hi,
You look forward to sensible comments your then going to ignore.
You will never achieve your goals with such an arrogant attitude
to ignorance, and ignoring anything that doesn't suit you.
You won't achieve the bold stuff and underlined is just
wrong, causing loads of problems due to pure dogma.
No point offering any sensible advice, you won't take it.
As you won't develop a sensible approach there is nothing
much to see here folks, other than how to be belligerent.
rgds, sreten.
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I set up one of the 2 inches with a 15 and they sound OK. The 15 is a cheap driver for proof of concept, little FR below ~75hZ. Rolls off on the high side at ~2500-3150.
The issues are:
-2 inch drivers over excursion. They try to recreate ~80hZ (!) and this caused over excursion at any volume thus...
-A real tweeter is needed one with a large faceplate to modify ringing and FR, 4 inch plate.
-Best would be a planar tweeter but access to those parts in my location is not likely.
-Floor boundary placement of the 15 reinforces the bass nicely but,,,
-Soundstage is an issue as the sweet spot is 18 inches off the floor
-Need a much more robust frame/support for the 15.
-Higher quality drivers high and low once the setup improves
All things considered I am happy with the sound, it just needs tweaking. Imaging is good, as far as one can tell that close to the floor. Moving the woofer off the floor will eliminate floor reinforcement, just moving the tweeter up will spread out the image as the woofer covers up to ~2k or so, perhaps angling up of drivers to the listening position shall work.
I intentionally use cheap drivers for first builds to work out details. My PC desk cardboard OB began with 1EUR yellow cone paper woofers, and now the total parts cost is up to 43.75EUR and the sound is very good. With each build there is a point of diminishing returns, with the PC OB I think I have gone as far as I wish at this point.
The issues are:
-2 inch drivers over excursion. They try to recreate ~80hZ (!) and this caused over excursion at any volume thus...
-A real tweeter is needed one with a large faceplate to modify ringing and FR, 4 inch plate.
-Best would be a planar tweeter but access to those parts in my location is not likely.
-Floor boundary placement of the 15 reinforces the bass nicely but,,,
-Soundstage is an issue as the sweet spot is 18 inches off the floor
-Need a much more robust frame/support for the 15.
-Higher quality drivers high and low once the setup improves
All things considered I am happy with the sound, it just needs tweaking. Imaging is good, as far as one can tell that close to the floor. Moving the woofer off the floor will eliminate floor reinforcement, just moving the tweeter up will spread out the image as the woofer covers up to ~2k or so, perhaps angling up of drivers to the listening position shall work.
I intentionally use cheap drivers for first builds to work out details. My PC desk cardboard OB began with 1EUR yellow cone paper woofers, and now the total parts cost is up to 43.75EUR and the sound is very good. With each build there is a point of diminishing returns, with the PC OB I think I have gone as far as I wish at this point.
Fantastic idea. Is it possible and desirable to mount this directly to the mounting screws of the 15 in a No Baffle setup? Or does the spacing need to be greater?
A piece of cardboard would do to test the FR and then something more robust once permanent, I think.
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I use rings of foam core but cardboard will work. You can simulate response in HR or Akabak before making it if you want - that will guide you to approximate correct dia and volume. First try existing volume of cone with no spacer.
Mirage:
You get me completely wrong.
Backwards.
I was blessing you for what you're doin.
Sorry.
Iam out of this thread.
Honestly
Good luck.
You get me completely wrong.
Backwards.
I was blessing you for what you're doin.
Sorry.
Iam out of this thread.
Honestly
Good luck.
Issues with the 15's.
One arrived pre-fried and the other did not sound right. I was listening to piano and such and there was an odd suck out where one should not have been so I ran some test tones.
They had no FR graphs on the sellers page, that's why they are priced at 10EUR.
Put 3 x 22uF in series to figure this out. First one, then two, then a third, have not gotten to the fourth for an Xo of ~300.
The FR of these in free air is 75-300hZ.
300, not 3000. Yikes. No way to acoustically Xo to a smaller tweeter or 2inch without a high pass cap to filter out the lowest bass on a 2/3/4/5/6.5 inch wide range. Running any 2 or 3 inch un capped would cause it to over extend and any tweeter would roll off naturally at 1, 2, or 3k, far above this 15's roll off.
And as always no soundstage once a second driver is in the mix.
Moving the tweeter back and forth in its frame to in front of and behind the woofer changes the tonality of instruments and the soundstage focus, tweaking this later could have benefits. Counter to common wisdom having the tweeter in front of the woofer face plate sounds best.
Going to have to get some other 15's with proper graphs and such.
Driver selection in China is almost uniformly of very low Qts drivers mostly designed for nearfiled listening in ported small bookshelf boxes. Some as low as o.26, extremely low Q.
Yes, I know that makes them not ideal for OB or NOB.
More tinkering after lunch...
One arrived pre-fried and the other did not sound right. I was listening to piano and such and there was an odd suck out where one should not have been so I ran some test tones.
They had no FR graphs on the sellers page, that's why they are priced at 10EUR.
Put 3 x 22uF in series to figure this out. First one, then two, then a third, have not gotten to the fourth for an Xo of ~300.
The FR of these in free air is 75-300hZ.
300, not 3000. Yikes. No way to acoustically Xo to a smaller tweeter or 2inch without a high pass cap to filter out the lowest bass on a 2/3/4/5/6.5 inch wide range. Running any 2 or 3 inch un capped would cause it to over extend and any tweeter would roll off naturally at 1, 2, or 3k, far above this 15's roll off.
And as always no soundstage once a second driver is in the mix.
Moving the tweeter back and forth in its frame to in front of and behind the woofer changes the tonality of instruments and the soundstage focus, tweaking this later could have benefits. Counter to common wisdom having the tweeter in front of the woofer face plate sounds best.
Going to have to get some other 15's with proper graphs and such.
Driver selection in China is almost uniformly of very low Qts drivers mostly designed for nearfiled listening in ported small bookshelf boxes. Some as low as o.26, extremely low Q.
Yes, I know that makes them not ideal for OB or NOB.
More tinkering after lunch...
I can probably find foam core scraps around the local appliance store.
Cardboard is everywhere here.
Would such a setup work well with a planar that rolls off ~1500?
And what drivers are you finding that roll off, without a filter, at 400?
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You can get just about any driver to roll off at 400hz it is a function of chamber volume and aperture area - that is basis of low pass filtering of BLH and even BR speakers to some extent. The idea is that choking down a volume chamber reduces HF that can get through. You can use basic equation to get first order cutoff freq or use a simulation like HR or AkAbak.
There will still be some leakage but it helps a lot. It may introduce a peak before the falloff. I used it for a slot loaded open baffle using six 6.5 in drivers.
There will still be some leakage but it helps a lot. It may introduce a peak before the falloff. I used it for a slot loaded open baffle using six 6.5 in drivers.
I was not clear - I was referring to the free air FR t/s graph.
Slotting the baffle or placing a disc in front of the woofer would work, more so for the woofer as a low pass filter, but I was thinking of a mid-range that rolls off at 400hZ naturally in the t/s measurements to avoid over driving the widerange acting as a tweeter. The 2 inches over drive at volume levels even I think too low and the tweeters roll off far too high for this 75-300 KTV 15. The 2's are trying to do too much (these are made with very low Q and intended for small, near field, desk top boxes), and that 15 is sitting right under them.
Great idea btw, to slot load the six wide ranges.
What is your static DC resistance on the six combined drivers? Is it 3 x 2 drivers in series parallel or 2 x 3 in sp, or...?
Slotting the baffle or placing a disc in front of the woofer would work, more so for the woofer as a low pass filter, but I was thinking of a mid-range that rolls off at 400hZ naturally in the t/s measurements to avoid over driving the widerange acting as a tweeter. The 2 inches over drive at volume levels even I think too low and the tweeters roll off far too high for this 75-300 KTV 15. The 2's are trying to do too much (these are made with very low Q and intended for small, near field, desk top boxes), and that 15 is sitting right under them.
Great idea btw, to slot load the six wide ranges.
What is your static DC resistance on the six combined drivers? Is it 3 x 2 drivers in series parallel or 2 x 3 in sp, or...?
I remember what I did in my line level LP filter for OB bass was setting the shoulder frequency at 40 Hz or so.
That is for compensating dipole loss and a proper attenuation to mid and HF. The final FR is pretty much flat from 30 to 160 Hz or so then rolling off gently.
If such a filter can be done in acoustics, then I guess the port (of the BP) would be very small to suppress the output of higher frequency. Eventually the overall sensitivity (efficiency) would be very low. That's unavoidable. I don't see the benefit doing so.
Edit: Oh, I remember now. Bad memory. This is the crazy one who claim he/she doesn't need bass and xo ...etc. Oh well...
That is for compensating dipole loss and a proper attenuation to mid and HF. The final FR is pretty much flat from 30 to 160 Hz or so then rolling off gently.
If such a filter can be done in acoustics, then I guess the port (of the BP) would be very small to suppress the output of higher frequency. Eventually the overall sensitivity (efficiency) would be very low. That's unavoidable. I don't see the benefit doing so.
Edit: Oh, I remember now. Bad memory. This is the crazy one who claim he/she doesn't need bass and xo ...etc. Oh well...
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The one 15 has a manu defect, will have to get it replaced. The cone is not properly glued/seated to the spider at the top of the coil and this causes distortion and lack of SQ. When I press down the dust cap I can intermittently get good SQ.
It is glued and attached, but improperly.
The one mock up sounds ok in the frame and the one 15 resting on the floor perpendicular to the floor facing the listening seat, Needs higher quality drivers and a woofer that has FR up to ~1500 to Xo with a tweeter that goes down to the same FR.
I also need to fabricate a way to elevate the frame for the tweeter to the listening height, not 18 inches off the carpet. If the soundstage holds up I may just angle the woofer up to the listening seat and leave it on the floor.
As always, it's all about the soundstage.
It is glued and attached, but improperly.
The one mock up sounds ok in the frame and the one 15 resting on the floor perpendicular to the floor facing the listening seat, Needs higher quality drivers and a woofer that has FR up to ~1500 to Xo with a tweeter that goes down to the same FR.
I also need to fabricate a way to elevate the frame for the tweeter to the listening height, not 18 inches off the carpet. If the soundstage holds up I may just angle the woofer up to the listening seat and leave it on the floor.
As always, it's all about the soundstage.
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I am swapping out the many drivers on my styrene panels, fabricated a faceplate from binder covers to bolt to the styrene, allows for a larger opening behind it and I can attach 3/4/5/6.5 inch drivers to the plate and attach the plate to the styrene and listen to different drivers. It's a little too flexible, looking for something a bit more stiff but not too thick.
With a 15 driver you should be able to reach 250hz without a baffle easily at low volumes.
My biggest question mark WRT the whole approach is what about SPL? It has to differ a lot between the two drivers, even when considering the roll off.
My biggest question mark WRT the whole approach is what about SPL? It has to differ a lot between the two drivers, even when considering the roll off.
SPL sensitivity were chosen to match, not that much of an issue.
Second go round will require a much better fit on drivers, and if that does not work then a high pass cap may be needed 😱.
The idea works, to my satisfaction, it just needs tweaking.
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