Martin, i think what you built and shared with us on that project is wonderful! I have a handful of full range drivers i'd like to experiment with and may do something similar. Great job thinking thru the removable baffle. I'd like to be able to accommodate larger drivers up to 8 inch. I'm in the process of building a sealed powered sub that will live in a corner allowing me to play with different drivers in different types of cabinets including OB. I haven't critically listened to anything except for the H-frames with Alpha 15s for a couple years and am curious how going back to a sealed sub will be. I'll report my listening impressions for sure.
Last night i was enveloped in music for about 3 hours listening to Cowboy Junkies, Ammie Mann, Rachael Yamagata and finally Frank Sinatra. OB Beta 12lta (plus helper tweeter) over H-frames.
PS. Pano, i see you posted some cheap fun! Are those yours? If so, how do you like them?
Last night i was enveloped in music for about 3 hours listening to Cowboy Junkies, Ammie Mann, Rachael Yamagata and finally Frank Sinatra. OB Beta 12lta (plus helper tweeter) over H-frames.
PS. Pano, i see you posted some cheap fun! Are those yours? If so, how do you like them?
Zilla - those belong to John Busch, also a member here. I'll be building a pair soon. John's checking to see if there is enough difference to warrant the second woofer, at the moment he's happy with 1. Interestingly, a 4 woofer version costs only a few bucks more because of smaller inductors and the 4-up woofer price. Either way, they are super affordable.
Gotta get building, I have all parts in stock except the woofers.
Gotta get building, I have all parts in stock except the woofers.
Hi,
I beg to differ, there is nothing unreal about a paper exercise.
You layout a design and explain why (or give references to indicate)
why it seems to gel together and your choices seem good to you,
and invite examination / critique of what your suggesting by others.
The basic premise from the original post is a Jamo inspired OB.
This defines all the basic details, some may prefer something
else, but that doesn't change the basic premise. MJK seems
to prefer FR's, but he doesn't argue that point in this thread.
Similarly I don't want to debate rear tweeters
here, they are an option, not a necessity.
Just because you don't build a design does not render it meaningless,
anymore than building a very poor design makes it more meaningful.
My main worry would that for the passive version something like +10dB
bass sensitivity rather than +6dB sensitivity is actually needed, and
that the passive version might disappoint / underwhelm the builder.
Thinking about that I reckon incorporating this would be a good idea :
Baffle Step Compensation
An externally hosted image should be here but it was not working when we last tested it.
From Elliot Sound Products, implement at the power amplifier input
(Or build into the far end of the power amplifier cable, in a little box.)
This would make the passive version nearly as flexible as the active
version. I reckon 22nF is near ideal for a 400Hz acoustic c/o point.
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I do not intend to insist, but only to point something. With second crossover at ~1500-1800 Hz, these won't be a true dipole, but rather a no box speakers. Almost 4 octaves without rear radiation.
And if we consider the crossover of the Zaph in-wall:
R2 and R3 both being 4 ohm make about 8 db of attenuation (3ohm Dcr and 0.017mh). So the extra rear tweeter can come absolutely for free with no penalty in FR or phase response of the forward radiation.
See the tweeter level options:
Impedance is steady 4 ohms 3 to 15 kHz regardless of R3.
The very small reactance of a tweeter makes a 4 ohm tweeter a much better approximation to 4 ohms than the range from 3 to 6 ohms admissible for R3.
The signal will still be divided in two with the one half being distributed to the front tweeter. You could even use up to two ohms in series with one of the tweeters for adjusting to taste and still be inline with the original parameters of the Zaph crossover. It just has provisioned signal dividing regardles how you burn the one half whether with a resistor or with another tweeter.
See tweeter parameters:
Vifa, DQ25SC16
Dcr - 3 ohms and Le - 0.017mh
It even can be said that you ought to add the rear tweeter in order to preserve the balance as it wasn't supposed to be a dipole. Further having in mind the above said that the rear tweeter comes at no penalty, it becomes obvious.
I have dipole that is a dipole up to ~10 kHz and one that is a dipole all the way and somehow the second one sound less artificial and more open.
**Sreten*don't*read*above*unless*you*decide*to*opt*for*a*rear*tweeter**
About the sensitivity, I think that the 86-87 db mean SPL of the ZAPH will blend nicely with the twin 88 db "15 Goldwoods, they would be at least 94 db@ the same voltage, this gives you nearly 8 db difference.
What is causing your concerns for the sensitivity? Maybe the different figures for the different versions?
The in wall version has the sensitivity if the baffle step compensated version. But without the BSC. Then maybe yours is the BSC version and not the in-wall one?
The crossover and FR of the conventional BSC version:
With 85 db, you will have nearly 10 db more bass SPL.
Best regards!
And if we consider the crossover of the Zaph in-wall:
R2 and R3 both being 4 ohm make about 8 db of attenuation (3ohm Dcr and 0.017mh). So the extra rear tweeter can come absolutely for free with no penalty in FR or phase response of the forward radiation.
See the tweeter level options:
Impedance is steady 4 ohms 3 to 15 kHz regardless of R3.
The very small reactance of a tweeter makes a 4 ohm tweeter a much better approximation to 4 ohms than the range from 3 to 6 ohms admissible for R3.
The signal will still be divided in two with the one half being distributed to the front tweeter. You could even use up to two ohms in series with one of the tweeters for adjusting to taste and still be inline with the original parameters of the Zaph crossover. It just has provisioned signal dividing regardles how you burn the one half whether with a resistor or with another tweeter.
See tweeter parameters:
Vifa, DQ25SC16
Dcr - 3 ohms and Le - 0.017mh
It even can be said that you ought to add the rear tweeter in order to preserve the balance as it wasn't supposed to be a dipole. Further having in mind the above said that the rear tweeter comes at no penalty, it becomes obvious.
I have dipole that is a dipole up to ~10 kHz and one that is a dipole all the way and somehow the second one sound less artificial and more open.
**Sreten*don't*read*above*unless*you*decide*to*opt*for*a*rear*tweeter**
About the sensitivity, I think that the 86-87 db mean SPL of the ZAPH will blend nicely with the twin 88 db "15 Goldwoods, they would be at least 94 db@ the same voltage, this gives you nearly 8 db difference.
What is causing your concerns for the sensitivity? Maybe the different figures for the different versions?
The in wall version has the sensitivity if the baffle step compensated version. But without the BSC. Then maybe yours is the BSC version and not the in-wall one?
The crossover and FR of the conventional BSC version:
With 85 db, you will have nearly 10 db more bass SPL.
Best regards!
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Hi,
The above post is the sort of thing that just pointlessly complicates things.
the Jamo's are not dipolar above around 2KHz, and that is part of the original
premise, and there are lots of other OB's that are similar, without detriment.
2 ohm treble impedance is not appropriate, you can't add an extra tweeter
for free as R3 also damps the tweeters resonance, its all poor conjecture ...
Like I said if its good enough for a $10,000+ speaker, why argue ?
What is obvious very much depends on what you can actually see ....
The inwall version does not have the same sensitivity as the BSC version,
its higher, by 4dB or so, and 87dB is the target sensitivity, not 83dB,
the BSC'd version is simply wrong for a 20" baffle, it will be wrong.
As it is your showing the reduced BSC option, 85dB, but its still wrong.
The BSC versions are not appropriate. The baffle hump of a 20" wide baffle
is dealt with in MJKs c/o by moving the electrical c/o point to 500Hz to
give an acoustic 400Hz c/o point, (given a flat 2pi mid/treble response).
The in-wall version is designed to be flat into 2pi, halfspace, loading.
I don't like the look of the GW's*. The GRS's at 87dB will be 93dB a pair 4 ohm.
This is 6dB more than the ZA5.2iw which is 87dB, it might not be enough,
as MJK indicates bass levels are set 3dB higher than the sims indicate.
The idea is KISS, that doesn't mean the various issues haven't been
thought through, they have, which is why I posted the arrangement.
rgds, sreten.
*Only in comparison to the cheaper and apparently better to me GRS's,
but either choice seems valid, I'm as sucker for apparently bigger magnets,
and only want Qts to be as high as it needs to be, Qts=1.4 versus Qts=2.
The above post is the sort of thing that just pointlessly complicates things.
the Jamo's are not dipolar above around 2KHz, and that is part of the original
premise, and there are lots of other OB's that are similar, without detriment.
2 ohm treble impedance is not appropriate, you can't add an extra tweeter
for free as R3 also damps the tweeters resonance, its all poor conjecture ...
Like I said if its good enough for a $10,000+ speaker, why argue ?
What is obvious very much depends on what you can actually see ....
The inwall version does not have the same sensitivity as the BSC version,
its higher, by 4dB or so, and 87dB is the target sensitivity, not 83dB,
the BSC'd version is simply wrong for a 20" baffle, it will be wrong.
As it is your showing the reduced BSC option, 85dB, but its still wrong.
The BSC versions are not appropriate. The baffle hump of a 20" wide baffle
is dealt with in MJKs c/o by moving the electrical c/o point to 500Hz to
give an acoustic 400Hz c/o point, (given a flat 2pi mid/treble response).
The in-wall version is designed to be flat into 2pi, halfspace, loading.
I don't like the look of the GW's*. The GRS's at 87dB will be 93dB a pair 4 ohm.
This is 6dB more than the ZA5.2iw which is 87dB, it might not be enough,
as MJK indicates bass levels are set 3dB higher than the sims indicate.
The idea is KISS, that doesn't mean the various issues haven't been
thought through, they have, which is why I posted the arrangement.
rgds, sreten.
*Only in comparison to the cheaper and apparently better to me GRS's,
but either choice seems valid, I'm as sucker for apparently bigger magnets,
and only want Qts to be as high as it needs to be, Qts=1.4 versus Qts=2.
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Hi,
Right link but not the right version.
Mid/treble is "ZA5.2iw - 2-way in-wall system".
Designed to be flat into 2pi, so it fits in with MJK's c/o arrangement.
Used as an OB mid, with possibly the higher treble level used.
rgds, sreten.
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Hi,
Specifications: • Power handling: 150 watts RMS/300 watts max • VCdia: 1-1/2" • Le: 1.14 mH • Impedance: 8 ohms • Re: 7.21 ohms • Frequency range: 25-4,000 Hz • Fs: 29 Hz • SPL: 87 dB 1W/1m • Vas: 9.39 cu. ft. • Qms: 5.09 • Qes: 1.92 • Qts: 1.39 • Xmax: 4 mm • Dimensions: Overall diameter: 15-1/8", Cutout diameter: 14", Depth: 5-7/16".
$23 each 4-up versus $36 each 4 up
Specifications: • Power handling: 135 watts RMS/250 watts max • Voice coil diameter: 1-1/2" • Le: 0.9 mH • Re: 7.1 ohms • Frequency response: 27-1,200 Hz • Magnet weight: 20 oz. • Fs: 29 Hz • SPL: 87.8 dB 1W/1m • Vas: 12.95 cu. ft. • Qms: 7.08 • Qes: 2.69 • Qts: 1.95 • Xmax: 3.5 mm • Dimensions: Overall Diameter: 15" Cutout Diameter: 13-3/4" Mounting Depth: 5-3/16" • Net weight: 5 lbs.
What is your gut feeling regarding this budget driver choice ?
rgds, sreten.
An externally hosted image should be here but it was not working when we last tested it.
Specifications: • Power handling: 150 watts RMS/300 watts max • VCdia: 1-1/2" • Le: 1.14 mH • Impedance: 8 ohms • Re: 7.21 ohms • Frequency range: 25-4,000 Hz • Fs: 29 Hz • SPL: 87 dB 1W/1m • Vas: 9.39 cu. ft. • Qms: 5.09 • Qes: 1.92 • Qts: 1.39 • Xmax: 4 mm • Dimensions: Overall diameter: 15-1/8", Cutout diameter: 14", Depth: 5-7/16".
$23 each 4-up versus $36 each 4 up
An externally hosted image should be here but it was not working when we last tested it.
Specifications: • Power handling: 135 watts RMS/250 watts max • Voice coil diameter: 1-1/2" • Le: 0.9 mH • Re: 7.1 ohms • Frequency response: 27-1,200 Hz • Magnet weight: 20 oz. • Fs: 29 Hz • SPL: 87.8 dB 1W/1m • Vas: 12.95 cu. ft. • Qms: 7.08 • Qes: 2.69 • Qts: 1.95 • Xmax: 3.5 mm • Dimensions: Overall Diameter: 15" Cutout Diameter: 13-3/4" Mounting Depth: 5-3/16" • Net weight: 5 lbs.
What is your gut feeling regarding this budget driver choice ?
rgds, sreten.
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Were you planning to eq them with boost to get a little bass out of it? 3.5 / 4mm xmax doesn't seem like much. Maybe something with a little more motor?
Admittedly, I have no experience with OB, but I'm interested in this project as it seems cheap / easy.
The Fi Q15 might be cool (and look almost just like the woofer jamo used), but they're a little pricey.
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Hi,
The choice of driver Qts determines the amount of low bass EQ bass boost.
The Qts=2 driver adds around 3dB more than the Qts=1.4 driver around
Fs (30Hz), but then rolls off quicker, and won't be as tight transiently.
Choice of high Q drivers is very limited, by definition they have weak motors.
Further up MJK's offset c/o adds a further 6dB or so of bass boost.
Your right, 4mm is not a great amount*, but you have two 15"ers ......
As they are open baffle expect maximum bass SPL levels to be around
a fairly average 10" bass unit in a box (not a subwoofer). OB's simply
don't do bone crunching bass, its all about subtlety, if anything.
Your right I'm trying to make it relatively cheap as possible, technically
as sound as is possible, easy enough to do with c/o details supplied,
and as an OB relatively simple to build.
Though I now think for the passive version the ESP passive line level
EQ circuit would greatly reduce risk, and I'm pretty sure it would be
very useful for adjustment to suit various different listening levels.
rgds, sreten.
*OB's have baffle loss, the lower you go the less SPL they produce
for a given driver excursion, why you need big drivers to produce
an adequate domestic bass level, but they do go deep at modest
bass levels quite easily, unfettered by box volume constraints.
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Hi,
If you read back MJK indicates the GW's will go flat to 30Hz in a 20" baffle.
What is "ideal" depends on a number of things, very difficult to surmise here.
I'd really like to see more technical info for both drivers, it is a toss up.
What I can say is flat will more likely suit a wooden structure / building
and a tapered bass roll a more solid structure / building. The higher the
Q of the driver, the less power it will take around 30Hz, so IMO the
higher Q driver would suit lower listening levels than the lower Q.
Its impossible to say, but to me the GRS's are more appealing.
That does not mean of the two they are the best choice ....
rgds, sreten.
Get the GRS. See the photo I posted earlier. Maybe John B will chime in here, he has four of them and likes them a lot. A much better driver than price and appearance would lead you to believe. (John owns more 12, 15, 18 & 21" drivers than any DIYer I know.)
OK, 5.2iw, got it. Looks like a good choice but I'll bet you have to do some crossover work to use it open back. Box crossovers (even IB) rarely work well on OB. The baffle, rear radiation and walls change the tonal balance enough that what works in a box doesn't work on OB. It's a good starting point, tho.
OK, 5.2iw, got it. Looks like a good choice but I'll bet you have to do some crossover work to use it open back. Box crossovers (even IB) rarely work well on OB. The baffle, rear radiation and walls change the tonal balance enough that what works in a box doesn't work on OB. It's a good starting point, tho.
Here is one I have been working on. Should be done and measured soon. Not exactly beer budget, but I'm resourceful
A friend of mine designed the crossover, so I cannot answer much regarding the circuitry.
Blair
A friend of mine designed the crossover, so I cannot answer much regarding the circuitry.
Blair
Attachments
![AEx2 HDS Neo3 Diople crossover[1].jpg](/community/data/attachments/246/246178-ab7526c1adaf0a2e917f58f10b28597a.jpg)
Hi,
It isn't a box c/o, its effectively a huge OB c/o, the same as 2pi loading.
MJK's c/o compensates for the 20" baffle effects for a driver flat into 2pi.
The point is you don't have to do any c/o work, other than select
treble level, probably a little higher than the default. For sure the
power response will be different, but that is what makes different
speaker types sound different, time and time again it has been
shown a relatively flat direct response is paramount to quality.
The delayed or room or diffused response is different for different
speaker types but you can only slightly tweak the the direct
response to compensate for it without messing things up.
I don't agree any real c/o work is needed, that is one of the
main reasons I posted, YMMV, but it is a sound methodology.
Like the "its not dipole above 2KHz" alleged "issue" that does
not really matter for acoustic reasons I'm not going to go into,
(but why a lot of OB speakers don't bother with dipole treble),
I find saying it won't be right but not how it is wrong, tedious.
Its a relatively simple plan that will work better than one that is wrong.
I've seen enough of them .... getting something completely wrong .....
I'm really interested in have I got something fundamentally wrong ?
not subtleties of the conjectural type .....
rgds, sreten.
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It's not a huge OB, it's IB. They are not the same. The IB effectively has no rear radiation.
But no worries, build it and find out if you like it - could work well for you. The most important thing is Build It!
FWIW, it took me (dummy that I am) about two years to understand the differences and "think out of the box" with OB crossovers. You gotta start somewhere. Just trying to pass along some hard learned knowledge and experience.
But no worries, build it and find out if you like it - could work well for you. The most important thing is Build It!
FWIW, it took me (dummy that I am) about two years to understand the differences and "think out of the box" with OB crossovers. You gotta start somewhere. Just trying to pass along some hard learned knowledge and experience.
Hi,
Yes and I mentioned that in the original post, you may need to lift the
treble level a little over Zaphs default, for want of any other sensible
plan or approach, none are forthcoming, just that "it won't be right".
Well I disagree, with no better plan, go for the best one available.
I'm getting bored with stating the obvious "critique".
Its obvious to me also, and I've thought about it.
If no-one can pick any real holes in what I'm suggesting,
then that probably means means its as good a plan as any.
With passive c/o treble adjustment and the line level EQ
option for bass to mid, IMO it can be made to work well.
rgds, sreten.
There is no difference between huge OB and IB effectively,
as the only way to do both ends up exactly the same .....
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>>> What is your gut feeling regarding this budget driver choice ?
http://www.diyaudio.com/forums/mult...n-10-000-jamo-open-baffles-5.html#post2794927
They sim a bit differently but i think they are pretty close.
http://www.diyaudio.com/forums/mult...n-10-000-jamo-open-baffles-5.html#post2794927
They sim a bit differently but i think they are pretty close.
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