Hi tinitus,
Also these, though still an import;-
http://www.madisound.com/catalog/product_info.php?products_id=1768
and these, but rather expensive;-
http://www.supravox.fr/anglais/haut_parleurs/400_GMF.htm
http://www.supravox.fr/anglais/mesures/mes400EXC1.htm
Panomaniac is correct, so maybe better to look for 2x Pro divers in parallel with lesser pro power handling capabilities like the SM-115N listed under 'products' and then 'SM' and then 'Low Frequency' here;-
http://profesional.beyma.com/ENGLISH
This lifts the LF SPL capabilities without introducing a Qts boost.
I guess the OB DIYers are not properly catered for when it comes to woofers.
Cheers ........ Graham.
Also these, though still an import;-
http://www.madisound.com/catalog/product_info.php?products_id=1768
and these, but rather expensive;-
http://www.supravox.fr/anglais/haut_parleurs/400_GMF.htm
http://www.supravox.fr/anglais/mesures/mes400EXC1.htm
Panomaniac is correct, so maybe better to look for 2x Pro divers in parallel with lesser pro power handling capabilities like the SM-115N listed under 'products' and then 'SM' and then 'Low Frequency' here;-
http://profesional.beyma.com/ENGLISH
This lifts the LF SPL capabilities without introducing a Qts boost.
I guess the OB DIYers are not properly catered for when it comes to woofers.
Cheers ........ Graham.
I apologize that the graph didn't get uploaded with my last post - and I didn't notice! 
It is embedded below, so this time you can see it.
Hi tinitus. The 1st part of your quote is not from me, that must be John. The 2nd part is me.
Let me explain, if the chart below doesn't do the talking for me.
Whatever woofer you use for OB will need EQ if you want to get real low end. That's life, and that's why they make box speakers. It ain't pretty, but that's the way it is. So if you are starting at 86dB/W and having to EQ 10dB, where do you end up? In the dumps. But all is not as it may seem. Have a look at the plot below.
The missing chart:
We can see that the low Qts driver, the EV. falls of fastest. The high Qts driver the slowest (Alpha 15).
Now let's look at a practical application. We want our OB rig to have an F3 of 40Hz. How much do we have to attenuate the mids of each driver to give us that 40Hz f3 and where do we end up with over all sensitivity?
So there is still 9dB between the AE IB15 and the Alpha 15. But you can see John's point about the EV vs the AE. The EV ends up with an advantage of only 2dB a the cost of massive EQ.
In OB, just like in other speaker designs, you have to choose carefully. The bass losses on an Open Baffle need to be taken into account. They may be huge, if you choose the wrong driver. Starting out with the right driver will let you end up with good bass and good sensitivity.
It is embedded below, so this time you can see it.tinitus said:
Hi tinitus. The 1st part of your quote is not from me, that must be John. The 2nd part is me.
Let me explain, if the chart below doesn't do the talking for me.
Whatever woofer you use for OB will need EQ if you want to get real low end. That's life, and that's why they make box speakers. It ain't pretty, but that's the way it is. So if you are starting at 86dB/W and having to EQ 10dB, where do you end up? In the dumps. But all is not as it may seem. Have a look at the plot below.
The missing chart:
An externally hosted image should be here but it was not working when we last tested it.
We can see that the low Qts driver, the EV. falls of fastest. The high Qts driver the slowest (Alpha 15).
Now let's look at a practical application. We want our OB rig to have an F3 of 40Hz. How much do we have to attenuate the mids of each driver to give us that 40Hz f3 and where do we end up with over all sensitivity?
- Alpha15 -5dB EQ ____final = 93dB/W
- 15PW3 -9dB EQ ______final = 91.5dB/W
- EV 15 -17dB EQ _____final = 86dB/W
- AE 15IB -6dB EQ ____final = 84dB/W
So there is still 9dB between the AE IB15 and the Alpha 15. But you can see John's point about the EV vs the AE. The EV ends up with an advantage of only 2dB a the cost of massive EQ.
In OB, just like in other speaker designs, you have to choose carefully. The bass losses on an Open Baffle need to be taken into account. They may be huge, if you choose the wrong driver. Starting out with the right driver will let you end up with good bass and good sensitivity.
btw
Panomaniac, I dont see from where you got those graphs...they look very similar to me .... just different attenuations
Alpha15 and IB15 seem to have exactly the same response, just different SPL ... how come ?
Also we got to a point where the AE "dipole15" would be a better choise than the IB15
And remember I planned to use double woofers
How come that Hawthorne have succes with a single 88db woofer mated with a 97db coax ?
Panomaniac, I dont see from where you got those graphs...they look very similar to me .... just different attenuations
Alpha15 and IB15 seem to have exactly the same response, just different SPL ... how come ?
Also we got to a point where the AE "dipole15" would be a better choise than the IB15
And remember I planned to use double woofers
How come that Hawthorne have succes with a single 88db woofer mated with a 97db coax ?
Qoute from Hawthorne site
"Owners of The DUET will no longer think of open baffles as bass shy! Deep, tactile and visceral impacts are terms that aptly describe the presentation of the DUET. They create a rock solid foundation to the music in any room."
Rated at 96db ... coax driver 97db ... woofer 88.7db ... they have higher Qts though ... moderate baffle
Standard xo inductors and caps look rather small, so xo point is not low
"Owners of The DUET will no longer think of open baffles as bass shy! Deep, tactile and visceral impacts are terms that aptly describe the presentation of the DUET. They create a rock solid foundation to the music in any room."
Rated at 96db ... coax driver 97db ... woofer 88.7db ... they have higher Qts though ... moderate baffle
Standard xo inductors and caps look rather small, so xo point is not low
tinitus said:
Bass reinforcement, maybe. Something like what Lynn is doing in his "Beyond the Ariel" project.
If the 15" Coax can play low, then the 15" woofer could be brought in just to boost the lowest frequencies. So you would get a combined bass response that is higher.
Only guessing.
EDIT:
Yes, both drivers are high Qts. About 0.92
I'll try to run the same sims for you later - and add them together. I'm curious, too.
Hi tinitus,
Coming at your question from an opposite viewpoint, I could ask why some constructors are going for the higher Qes/ts drivers.
Reason, they are using the driver's Qes controlled Qms to boost the steady sine measured amplitude resounse.
Look at Michael's Alpha-15A plot.
That almost 3dB lift in the amplitude response above the Selenium 15PW3 is due to energy stored by the driver above that stored by the Selenium, this already having its own near optimum SPL response Qts figure of 0.61 (similar to the Beta-15A) which stores much less electromechanically transduced energy.
(Energy which should be moving the cone to generate a properly dynamic response and not becoming stored.)
Michael is showing the 'In-Room' response and not the *unloaded* 'On-Baffle' response, which really can show just how much of an amplitude peak the driver stored energy can give rise to at Fs. It is the stored energy from the first half or full cycle of waveform energisation which gives rise to this peak and a 'tonality' which is actually generated by the driver itself; not the music.
One Alpha-15A can level the amplitude response on its own, whereas lower Q drivers need to be separately amplified or to be parallel driven for a broader band 6dB LF lift, though this lift is achieved without invoking a similarly resonant tonality. Where the Alpha-15A has been scoring is that the single 15" is simple, its response benign and the result is generally well liked
Another aspect is that tube amplifiers and circuitry (crossover) between a SS amplifier and a woofer can effectively raise the Qts of a low Qes driver to achieve a 'best' sounding reproduction, whereas the only way of reducing the Qms induced Qts (bass tonality) of a high Qes driver, is with resistive (air motion) damping which reduces efficiency without improving reproduction dynamics.
Two medium Q LF drivers, or two efficient low Fs and lower Qes pro drivers are likely to be more sensitive than the Ae IB-15, though they will need a lower crossover point as Michael lists; this because the IB-15 wa designed for Infinite Baffle usage. Now if Ae could give this driver a much lighter cone with an Fs of around 24Hz and a Qes around 0.45 ....
Cheers ........... Graham.
Coming at your question from an opposite viewpoint, I could ask why some constructors are going for the higher Qes/ts drivers.
Reason, they are using the driver's Qes controlled Qms to boost the steady sine measured amplitude resounse.
Look at Michael's Alpha-15A plot.
That almost 3dB lift in the amplitude response above the Selenium 15PW3 is due to energy stored by the driver above that stored by the Selenium, this already having its own near optimum SPL response Qts figure of 0.61 (similar to the Beta-15A) which stores much less electromechanically transduced energy.
(Energy which should be moving the cone to generate a properly dynamic response and not becoming stored.)
Michael is showing the 'In-Room' response and not the *unloaded* 'On-Baffle' response, which really can show just how much of an amplitude peak the driver stored energy can give rise to at Fs. It is the stored energy from the first half or full cycle of waveform energisation which gives rise to this peak and a 'tonality' which is actually generated by the driver itself; not the music.
One Alpha-15A can level the amplitude response on its own, whereas lower Q drivers need to be separately amplified or to be parallel driven for a broader band 6dB LF lift, though this lift is achieved without invoking a similarly resonant tonality. Where the Alpha-15A has been scoring is that the single 15" is simple, its response benign and the result is generally well liked
Another aspect is that tube amplifiers and circuitry (crossover) between a SS amplifier and a woofer can effectively raise the Qts of a low Qes driver to achieve a 'best' sounding reproduction, whereas the only way of reducing the Qms induced Qts (bass tonality) of a high Qes driver, is with resistive (air motion) damping which reduces efficiency without improving reproduction dynamics.
Two medium Q LF drivers, or two efficient low Fs and lower Qes pro drivers are likely to be more sensitive than the Ae IB-15, though they will need a lower crossover point as Michael lists; this because the IB-15 wa designed for Infinite Baffle usage. Now if Ae could give this driver a much lighter cone with an Fs of around 24Hz and a Qes around 0.45 ....
Cheers ........... Graham.
Those graphs look like they came from Thorsten's Xlbaffle spreadsheet. It takes boundary gain into account, so it's probably picking up a few dB from the floor and back wall (depending on what was entered into the sims). A search through this forum should turn up Thorsten's posts where he talks about what's included in the simulation, what it can and cannot do, etc.
nickmckinney said:
If you look at the link below, you will find simulations of three different dipole configurations that produce 87 dB or greater at frequencies down to between 30 and 40 Hz without any EQ.
http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf
It comes down to having a Qts > 1, a fs around 40 Hz, and an appropriate crossover point. You really don't need a huge baffle.
panomaniac said:
A few things to mention here. First it depends on how low you are expecting the bass section of your OB to play. What you see in the graph is that they both go off the bottom of the screen at 25hz. At 25hz, the IB15 and Alpha15 are both at the exact same point. By 16Hz, the IB15 is actually over 5dB louder with equal input. Now for those looking at doing a true subwoofer section open baffle, this can be a big difference. For your 40hz F3 this may not be an issue, but for some it is.
Secondly, look at the overall output capability. It all comes down to displacement. With only 12.5W you will be exceeding the Xmax of the Alpha15 at 40hz. The IB15 however has much more useable excursion and power handling. A single IB15 with adequate power has the ability to play 8.5dB louder at 40hz than does the Alpha15. Even at that point it is still using only about 65% of it's available Xmax and will be more thermally limited at that point, meaning it is still operating in a very linear range. You would need 3 of the Alpha 15's to equal the output of the single IB15 at this 40hz point. Down below at say 20hz you would need 5 of the Alpha15's to equal the output of the single IB15 at Xmax. Again, it depends on application. It's a tradeoff between power vs efficiency and space. A single IB15 takes a lot less space on a baffle than 5 Alpha 15's and 500W amplification can be had quite inexpensively.
Also, take into account distortion. The Alpha15 does nothing to lower inductance or non-linear distortion, while the IB15 has the full copper sleeve on the pole like all the Lambda motors. I won't go through all the benefits of the copper sleeve, but will link you to the knowledge base article on it.
http://www.aespeakers.com/Lambda001-1.php
Yes, the higher the Q, the more extended the OB response will be. However, you need to also look at the phase and group delay issues caused by going with an extremely high Q driver. The Alpha15 has an Fs of 41hz, and in an OB, the Fc will equal Fs. This means at this point, the group delay will peak. In the case of this application, the Alpha15 peaks to 9ms at 40hz while the IB15 is at 3ms and does not surpass 9ms until under 20hz where the wavelength is much longer. I'd say right around 1.0 is an absolute maximum for Qts.
Again, the 40hz F3 may be practical for your application. For a 3way system I agree this could be quite practical. The point where people are considering IB15's for OB often is to cover the range down to as low as 16Hz. I have one person wanting to be able to do pipe organ material with an OB system. This requires multiple drivers per side. Looking at 4 IB15's per side with a good amount of power can reach his goals using an OB.
With the Alpha15 and the 5dB of EQ applied at 40hz, you are quite close to your limits at 93db 1m already. One more doubling of power and you are basically at the excursion limits o the diver. If this is loud enough for your goals, then it can work perfectly.
Again, it's about the person's overall goals for the system. For some, 40hz with higher efficiency and being able to power with a small tube amp may be their goal. For those wishing to play lower or louder, there just isn't any replacement for displacement. You need to move lots of air especially if doing an open baffle. In most applications though I suggest using an infinitebaffle subwoofer to supplement the low end of an OB system. It is much more efficient that way.
John
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