For anybody wishing to try an MJK style OB these may be worth a try.
I have never heard them so have no idea od their sound. They are
foam surround also and not as sensitive as the Eminences. Listed at
$64.95 ea.
15" Replacement Woofer, Laminated Cone, Foam Edge, 8 Ohm
Just after I posted I checked the link and the site is hosted in Aus. but is a US company
jamikl
I have never heard them so have no idea od their sound. They are
foam surround also and not as sensitive as the Eminences. Listed at
$64.95 ea.
15" Replacement Woofer, Laminated Cone, Foam Edge, 8 Ohm
Just after I posted I checked the link and the site is hosted in Aus. but is a US company
jamikl
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All those round woofers are made by Goldwood. There are a couple square ones on there too. I'm not sure if Goldwood makes those as well, but they don't appear on Goldwood's site. More importantly, the Qts of the square jobs is slightly below .7. There is a 15" version available elsewhere. See Parts Express, I don't know about Australia availability.
I have tried the 10" version of the square woofer in an OB PC speaker project, and it works great up to 300 Hz. To me the Q=.7 approach makes up well for the rolloff in its preservation of transient response. The decent "speed" keeps the bass impressive enough even if the level trails off at the bottom a bit. Many people have learned after many projects and modifications that they don't really want it louder if it's just a big resonant mess. The whole point of going OB in the first place is to get rid of that. They settle on a Q closer to 1 after starting much higher. AE speakers has a series of higher performance OB woofers. It's not necessarily relevant to your search, but they make Q=1 and .7 models.
I have tried the 10" version of the square woofer in an OB PC speaker project, and it works great up to 300 Hz. To me the Q=.7 approach makes up well for the rolloff in its preservation of transient response. The decent "speed" keeps the bass impressive enough even if the level trails off at the bottom a bit. Many people have learned after many projects and modifications that they don't really want it louder if it's just a big resonant mess. The whole point of going OB in the first place is to get rid of that. They settle on a Q closer to 1 after starting much higher. AE speakers has a series of higher performance OB woofers. It's not necessarily relevant to your search, but they make Q=1 and .7 models.
Goldwood GW-215/40/8 15" OEM Woofer 40 oz. | Parts-Express.com
Hi,
Its the same as the Goldwood, worth considering for OB's.
rgds, sreten.
Hi,
Its the same as the Goldwood, worth considering for OB's.
rgds, sreten.
Hi,
No, for higher Q drivers is defines the roll-off point, its very relevant.
rgds, sreten.
Hi,
It does not work like that, the open baffle roll of changes transient response,
as it must, as transient response is defined by frequency response and vice
versa. Lower Q drivers in an open baffle are fighting a losing battle.
Without some form of bass EQ higher Q drivers are the way to go generally,
if you want the best bass levels for your given baffle size, especially with
lower power amplifiers, the peaking Q gives useful efficiency gains.
Quad ESL57's and many other ESL's had a bass Q in the 2 to 3 range.
rgds, sreten.
The open baffle changes frequency response. Transient response near resonance is still defined by Q, no matter what type of system.
I understand what has been done in the past. See the Grenada. A reviewer I trust says it's maybe the best bass he's ever heard:
The Granada Loudspeaker
(I'm pretty sure those are the AE Speakers Dipole 12's)
Due to the very low cone stress in an open baffle woofer and the relatively low power it takes to achieve full excursion at the lowest frequencies, a moderate cost driver will not run into power handling issues before running out of excursion. Even a cheap woofer will not likely run into power handling issues through its entire operating band when equalized for flat response. If flatness is too much of an issue for some to leave it alone with Q=.7, it is quite easy to acheive the 6dB/oct gain with falling frequency without equivalently destructive effects of running high electromechanical Q at the speaker driver. See item 8:
http://www.linkwitzlab.com/filters.htm
In the end, the excursion/area is "where it's at" regarding open baffle output. It certainly does hamper power efficiency to run a lower Q, but staying around .7 is not going to require more power than typical .3-.5 Q drivers in a sealed box. The loss at very low frequencies is higher in the open baffle, but because the resonant frequency of the system is the natural frequency of the driver, you don't have to compensate for that as well. If maximum efficiency is the target, say possibly because of a favorite single ended tube amp, then there's no avoiding the high Q arrangement. If you're willing to throw common modern day power at the woofers, the Q = .7 approach is mainly superior. If you can't stand the idea of extra electrics/electronics to roll the top end down on the OB subs, you'll have to learn to like the high Q sound, and unfortunately, that part does sound exactly the same with or without a box.
I understand what has been done in the past. See the Grenada. A reviewer I trust says it's maybe the best bass he's ever heard:
The Granada Loudspeaker
(I'm pretty sure those are the AE Speakers Dipole 12's)
Due to the very low cone stress in an open baffle woofer and the relatively low power it takes to achieve full excursion at the lowest frequencies, a moderate cost driver will not run into power handling issues before running out of excursion. Even a cheap woofer will not likely run into power handling issues through its entire operating band when equalized for flat response. If flatness is too much of an issue for some to leave it alone with Q=.7, it is quite easy to acheive the 6dB/oct gain with falling frequency without equivalently destructive effects of running high electromechanical Q at the speaker driver. See item 8:
http://www.linkwitzlab.com/filters.htm
In the end, the excursion/area is "where it's at" regarding open baffle output. It certainly does hamper power efficiency to run a lower Q, but staying around .7 is not going to require more power than typical .3-.5 Q drivers in a sealed box. The loss at very low frequencies is higher in the open baffle, but because the resonant frequency of the system is the natural frequency of the driver, you don't have to compensate for that as well. If maximum efficiency is the target, say possibly because of a favorite single ended tube amp, then there's no avoiding the high Q arrangement. If you're willing to throw common modern day power at the woofers, the Q = .7 approach is mainly superior. If you can't stand the idea of extra electrics/electronics to roll the top end down on the OB subs, you'll have to learn to like the high Q sound, and unfortunately, that part does sound exactly the same with or without a box.
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Greetings, one for the aussies, if anyone is interested I have, 4 Eminance Alpha 15's for sale, two were used briefly on a test baffle and two are unused, have boxes. A friend and I imported these from America and we saved about $50 per driver. I would like to get back what I payed for them at $100 per driver $400 for the lot. They really area great OB driver and a well known entity with respect to OB designs out there, unfortunately I'm just not in a room where I can do OB now and so I'm about to embark on a mono corner horn to go with my largely mono jazz collection. I can probably deliver to Melb inner suburbs or post. cheers fergs
Hi,
Transient response for this case is not defined by the drivers Q. It is certainly
affected by the drivers Q and the baffle roll off. The baffle roll off effectively
adds damping to the transient response. Higher Q drivers used in open baffles
sound and measure nothing like they would do in infinite baffles or boxes.
rgds, sreten.
"The baffle roll off effectively adds damping to the transient response."
How is that possible if the baffle loss is not actually an additional resistive term (which would force a lower measured Q anyway) but just the shape and depth of the radiation pattern? In fact, due to acoustical unloading, I would expect the opposite to happen. The apparent magnitude of the response peak certainly will seem different if response at that frequency, at the listening position, has fallen for any reason at all, but the transient response well inside the dipole lobe will be dependent upon total Q. So you might say there is not as Much boom for same Q in a dipole, but there is the same kind of "mud". The transient response near the edges and practically outside dipole lobe, will still also be dependent upon total Q. You can't finally get better transient response than what you drive the air with to start. You can do all sorts of crazy things to sweep up for it though. Sit in a partial anechoic chamber might help.
How is that possible if the baffle loss is not actually an additional resistive term (which would force a lower measured Q anyway) but just the shape and depth of the radiation pattern? In fact, due to acoustical unloading, I would expect the opposite to happen. The apparent magnitude of the response peak certainly will seem different if response at that frequency, at the listening position, has fallen for any reason at all, but the transient response well inside the dipole lobe will be dependent upon total Q. So you might say there is not as Much boom for same Q in a dipole, but there is the same kind of "mud". The transient response near the edges and practically outside dipole lobe, will still also be dependent upon total Q. You can't finally get better transient response than what you drive the air with to start. You can do all sorts of crazy things to sweep up for it though. Sit in a partial anechoic chamber might help.
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The only place where you can easily get into picking nits with this is when you use electrical Q in a filter to compensate for the rolloff. Because it doesn't really matter were the resonance is in the system, the result can be arguably similar. But I don't think an RC filter for slope causes much trouble here, and if you use no compensation there is no question, other than whether you are less satisfied by lacking frequency or transient response. My personal preference is for the bass to be real even if it's a bit rarer.
Wait, Streten, you are right. The acoustical unloading at low frequencies in a dipole would cause a decrease in total Q. It would be enough similar to decreasing driving impedance or Re with falling frequency, if the cone load were constant. So, how do we analyze this exactly? It would depend upon baffle and room performance of course, but the Q at resonance is still the same. You get what you get in any case.
Hi,
As i understand it for 3rd order Butterworth you cascade a 1st order filter
(fixed "0.5 Q") (= baffle roll off) with a Q=1.0 second order filter for your
maximally flat filter. As its 3rd order transient response is worse than the
2nd order filter. (Q=0.7 being a Butterworth 2nd order maximally flat filter.)
If you reduce the second order filter to 0.7 you get an overdamped response.
(Overdamped here meaning lower Q than a maximally flat filter function).
Using unEQ'd drivers around Q=1.0 in an open baffle is similar to choosing
the box Q of around 0.7 for sealed boxes, maximally flat, a bit of boost or
less bass but better transient response.
OB roll off is third order, you just need to choose your poison ....
rgds, sreten.
http://www.quarter-wave.com/OBs/OB_Design.pdf
http://www.quarter-wave.com/Project08/Project08.html
As i understand it for 3rd order Butterworth you cascade a 1st order filter
(fixed "0.5 Q") (= baffle roll off) with a Q=1.0 second order filter for your
maximally flat filter. As its 3rd order transient response is worse than the
2nd order filter. (Q=0.7 being a Butterworth 2nd order maximally flat filter.)
If you reduce the second order filter to 0.7 you get an overdamped response.
(Overdamped here meaning lower Q than a maximally flat filter function).
Using unEQ'd drivers around Q=1.0 in an open baffle is similar to choosing
the box Q of around 0.7 for sealed boxes, maximally flat, a bit of boost or
less bass but better transient response.
OB roll off is third order, you just need to choose your poison ....
rgds, sreten.
http://www.quarter-wave.com/OBs/OB_Design.pdf
http://www.quarter-wave.com/Project08/Project08.html
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