Still hung up on the weak motor eh? I think you'll need more than a subjective opinion to prove your point though. There's a lot of proponents of the Alpha's...who in turn don't have any supporting measurements either. So goes the logic with beer.........unless you pointlessly like green bottles.
Samuel Adams certainly would have something to say about that.
unless you pointlessly like green bottles.
Oh, if only Sam Adams made speakers, I can see the commercial now:
"We're just literally shoving motor structure into our driver, there's over 75 lbs of neodymium in each one."
The crossover point is dictated by the dipole hump. For a tall 20" wide baffle standing on the floor the hump is between 300 and 400 Hz. So you set your low pass electrical crossover around 200 Hz and your high pass electrical crossover around 400 Hz so that the combined system acoustic crossover is at about 300 Hz.
Martin
Some people like the Alphas and some like the Betas. Probably room and amp dependent. Both are reasonably priced 15" woofers that can be use in an OB just like the GW or GRS drivers. Personal taste and budget drive the decisions.
The drivers you are using are no longer in production, they were a great deal. Probably too good of a deal for AE to make money on hence they are no longer available. If they were I would try them.
Since I have the more expensive Dipole 15 drivers and the Alpha 15 drivers I am able to hear them both in my experimental baffle with the same full range driver. The Dipole 15 is a better driver and does sound better, but in my opinion the improvements are not worth the cost difference. We have had this discussion before and our positions have not changed.
Too chase the "quality of music" you need to spend significantly more, not a problem for you and I obviously. But if cost was a consideration for a DIYer are you saying if you cannot afford the better woofer driver why bother building an OB system with the budget drivers being discussed? Personally, I could live with the less expensive options and still enjoy music even though the system is compromised per your statement. The result is not perfect but it is still pretty good. I might say better than most small stand mounted boxed speaker with the same cost target (the dynamics of a 15" woofer are hard to beat).
Martin
Hi,
One issue is that the bass drivers for this are cheap, no two ways about it,
and higher quality high Q drivers are simply not available, so you would
be forced down the route of better low Q drivers with active boost.
Which defeats the object of a simple passive OB speaker.
I have no doubts the Jamo drivers are superior, in response, distortion
and the ever critical parameter for low bass, excursion capability. No
such driver optimised for OB applications is available to the amateur.
Its churlish to knock the only drivers available to be used for this purpose.
rgds, sreten.
One issue is that the bass drivers for this are cheap, no two ways about it,
and higher quality high Q drivers are simply not available, so you would
be forced down the route of better low Q drivers with active boost.
Which defeats the object of a simple passive OB speaker.
I have no doubts the Jamo drivers are superior, in response, distortion
and the ever critical parameter for low bass, excursion capability. No
such driver optimised for OB applications is available to the amateur.
Its churlish to knock the only drivers available to be used for this purpose.
rgds, sreten.
sreten,
No, I just happened to quickly look at a simulation I had on my hard drive for two Alpha 15A woofers and a different full range driver on a 20" wide baffle. Depending on the number of Alpha 15A drivers and the next driver up in the system, the high pass crossover point gets tweaked to make sure they combine smoothly. I have used crossover points beyween 300 and 500 Hz in different design studys and for my own experimental OB system depending on the Qts of the full range driver.
Martin
Thinking about the statement above a little bit more. To my ears, the Dipole 15 extends deeper producing a more slightly pleasing bass performance compared to the Alpha 15A woofers. But if you look at the fs and Qts of the two drivers I guess this is not surprising.
Alpha 15A : fs ~ 39 Hz and Qts ~ 1.2
Dipole 15 : fs ~ 23 Hz and Qts ~ 0.82
Both of the other options, GW and GRS, have fs values of 29 Hz and Qts values of 1.95 and 1.39 respectivily. They appear to be closer to the Dipole 15 so they should produce deeper bass than the Alpha 15A woofers. I would expect them to perform between the Alpha 15A and Dipole 15 which narrows the gap between the low cost and the expensive drivers. Operating over a limited frequency range of fs to 200 Hz, I doubt that the quality of construction is a significant variable. If you were asking the cheaper woofers to extend up towards 1 kHz then I would expect significant perfomance advantages using the Dipole 15.
Martin
Hi Martin,
Qts in this case is 0.45 with Fs = 65Hz, the driver is flat into
2pi from 200Hz upwards, and -6dB at 70Hz again into 2pi.
If you assume all drivers have the same sensitivity what
c/o arrangement is indicated ? Do you just use 2nd order
L/R electrical and vary the c/o point offsets ?
rgds, sreten.
A couple of points and a comment.
A couple of years back at Burning Amp Papa Nelson in the process of demonstration of some very pricy custom full-range drivers (I think something like Festrex) used OB woofers that were full sheets of plywood wide. The woofers were Beta’s. The only warm beer was in my hand. The speakers sounded very nice.
Believe it or not I have more than one set of speakers set up in more than one room. In the small room with near field OB’s I do not have the real estate for 15 inch OB woofers. I use a single sealed subwoofer equalized to the small room. The tweeters are also not dipoles. In this small space I much prefer these speakers with OB midrange drivers to headphones. (the OB’s are MTM using two 6 ½” PL Vifa’s )
Now the comment: It is about personal preference, available space and swapping out all the pieces and parts that you can afford, just for the fun of it. The time is more a limiting factor than the money.
DT
A couple of years back at Burning Amp Papa Nelson in the process of demonstration of some very pricy custom full-range drivers (I think something like Festrex) used OB woofers that were full sheets of plywood wide. The woofers were Beta’s. The only warm beer was in my hand. The speakers sounded very nice.
Believe it or not I have more than one set of speakers set up in more than one room. In the small room with near field OB’s I do not have the real estate for 15 inch OB woofers. I use a single sealed subwoofer equalized to the small room. The tweeters are also not dipoles. In this small space I much prefer these speakers with OB midrange drivers to headphones. (the OB’s are MTM using two 6 ½” PL Vifa’s )
Now the comment: It is about personal preference, available space and swapping out all the pieces and parts that you can afford, just for the fun of it. The time is more a limiting factor than the money.
DT
Hi sreten,
I design by iterating simulations. I typically start with 2nd order LR at 200 Hz and 400 Hz. I iterate the frequency and the type of second order filter to dial in a smooth transition. Then I dial in individual crossover components to get additional smoothing and the final component values. The final crossover "type" may not be a perfect textbook 2nd order filter (Butterworth, Bessel, LR, ...). The driver fs and Qts can impact the final filter configuration.
Martin
I have one link to support my point: Open Baffle - Loudspeaker Design Part 16
I don't really think that as the writer says the quality of the response is roomdependent as such. The quality of output is more probably inherent with the quality of the driver. The Alpha will passive perhaps go some 5 Hz lower than the Beta in extension at the same level and those are really not the Hz you hear all the time. What you hear from the basspeaker all the time though will be the fundamentals and some overtones of bass and lowermidrange covering a lot of instruments and voice.
/Erling
I don't really think that as the writer says the quality of the response is roomdependent as such. The quality of output is more probably inherent with the quality of the driver. The Alpha will passive perhaps go some 5 Hz lower than the Beta in extension at the same level and those are really not the Hz you hear all the time. What you hear from the basspeaker all the time though will be the fundamentals and some overtones of bass and lowermidrange covering a lot of instruments and voice.
/Erling
Another part of that article:
Designing Loudspeakers - Open Baffle speakers - The Trials
The writer is Peter Comeau of Mission/Wharfedale/World Designs/Castle/Quad/Heybrook fame. I think he wrote for Hifi News for a while too.
Peter was going to build an OB designed for close to wall operation, a little like the Wharfedale SFB. I suspect he gave up when IAG/China came calling.
Designing Loudspeakers - Open Baffle speakers - The Trials
The writer is Peter Comeau of Mission/Wharfedale/World Designs/Castle/Quad/Heybrook fame. I think he wrote for Hifi News for a while too.
Peter was going to build an OB designed for close to wall operation, a little like the Wharfedale SFB. I suspect he gave up when IAG/China came calling.
And again, really a subjective 'rant' in context.....not to say your point isn't valid. A good set of measurements including impulse response would help to make your point. Having a way to quantify those few milliseconds into $$$ is another story.
The ported vs sealed camp would go to all out war over that one.Hi,
Regarding PC's comments on open baffles, like nearly all his articles,
they are biased towards what he has decided he wants to do, they
make out you are being imparted knowledge, but in fact you are not.
One man's tight bass is anothers no real bass, extended bass to
some is bloated bass to others, you simply can't win subjectively.
In the same situation comparing two nearly identical drivers except
for magnet size, the higher sensitivity lower Q driver will always
sound cleaner and tighter, with less extension, there is nothing
surprising about that at all, basically due to the response only,
its an inevitable effect of a bigger magnet, but its not the cause.
Less real bass extension gives apparently cleaner and tighter bass
in nearly all circumstances for similar drivers. Overegging the bass
pudding can give "slow" and "bloated" bass, you can say this is
cleaner and tighter than that which is relatively slow and bloated,
what you can't say is one is "clean and tight" and the other is
"slow and bloated", your using a fact to then mislead.
Everything is a compromise, and there are always those than will
say "this will be better" or "that will be better" without any real
technical justification, that makes it an opinion, not a fact.
In fact : the sort of placement PC seems to be going for
and justifying is very difficult to arrange in a lot of rooms,
I've seen it used with the Quad ELS63, and that required
a bass cut shelving circuit to restore correct bass balance,
(with the consequence of improved bass power handling).
rgds, sreten.
Regarding PC's comments on open baffles, like nearly all his articles,
they are biased towards what he has decided he wants to do, they
make out you are being imparted knowledge, but in fact you are not.
One man's tight bass is anothers no real bass, extended bass to
some is bloated bass to others, you simply can't win subjectively.
In the same situation comparing two nearly identical drivers except
for magnet size, the higher sensitivity lower Q driver will always
sound cleaner and tighter, with less extension, there is nothing
surprising about that at all, basically due to the response only,
its an inevitable effect of a bigger magnet, but its not the cause.
Less real bass extension gives apparently cleaner and tighter bass
in nearly all circumstances for similar drivers. Overegging the bass
pudding can give "slow" and "bloated" bass, you can say this is
cleaner and tighter than that which is relatively slow and bloated,
what you can't say is one is "clean and tight" and the other is
"slow and bloated", your using a fact to then mislead.
Everything is a compromise, and there are always those than will
say "this will be better" or "that will be better" without any real
technical justification, that makes it an opinion, not a fact.
In fact : the sort of placement PC seems to be going for
and justifying is very difficult to arrange in a lot of rooms,
I've seen it used with the Quad ELS63, and that required
a bass cut shelving circuit to restore correct bass balance,
(with the consequence of improved bass power handling).
rgds, sreten.
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Good point sreten, and i'm often fearful than a lot of 'hobbyists' don't understand this.....to the point where we get back to sealed systems being 'cleaner' when it's purely a lack of lower freq content that's often overcompensated by the room and not the speakers fault at all. The whole purpose of OB is to reduce these room modes from the get go and with proper extension and design will offer the possibility of the highest level of performance when compared to other alignments. Comparing or criticizing a weak motor on a 15" driver is really splitting hairs as a parallel pair of 15" Alphas per side is going to outperform a single bass unit box speaker on any given day of the week.
I think a budget concious 'format' design is just what this hobby needs but there's gotta be some considerations on the baffle. Most pass up this type of speaker based on the common DIY affordable OB's with the unusuallw wide baffles and somewhat 'less than acceptable' asthetics. Jamo addresses this with the 909 making for a system that almost anyone would be proud to own. Now we can all agree tha such a narrow baffle isn't exactly going to produce the lowest in-room response but there's concessions to be made with adding side panels to the area where the bass units are or carefull considerations in the crossover.
I'm hoping Martin will chime in here as if we use a pair of Alpha's as an example, that high efficiency is more usefull than it first appears especially if one considers a hybrid active version where a subwoofer amp (plate,chassis, whatever) is used.
I think a budget concious 'format' design is just what this hobby needs but there's gotta be some considerations on the baffle. Most pass up this type of speaker based on the common DIY affordable OB's with the unusuallw wide baffles and somewhat 'less than acceptable' asthetics. Jamo addresses this with the 909 making for a system that almost anyone would be proud to own. Now we can all agree tha such a narrow baffle isn't exactly going to produce the lowest in-room response but there's concessions to be made with adding side panels to the area where the bass units are or carefull considerations in the crossover.
I'm hoping Martin will chime in here as if we use a pair of Alpha's as an example, that high efficiency is more usefull than it first appears especially if one considers a hybrid active version where a subwoofer amp (plate,chassis, whatever) is used.
mayhem13,
since you brought it up. German Proraum produced a passive OB Neo10, Neo3 kit together with Usher basreflex bass. It was presented in Hobby HiFi january number 2008. Link is here (only in German I'm afraid): http://www.audax-speaker.de/index.p...=imported/tests-reviews/pro20d-hobby-hifi.pdf
Impressive deign ! The interesting parts are missing though, crossover and dimensions. The crossover was very simple for the Neo10, it relied on it's own rolloff and had a higpass only 6 dB/octav at 300 Hz, lowpass also 6 dB at 1500 Hz and also two notchfilters at 9.6 kHz and 2250 Hz all according to the measurements presented in the article. Obviously Proraum didn't see any problem with this crossover and B&G themselves state 2nd order 250 Hz as a minimum.
But you do need an exellent bass to accompany !
/Erling
since you brought it up. German Proraum produced a passive OB Neo10, Neo3 kit together with Usher basreflex bass. It was presented in Hobby HiFi january number 2008. Link is here (only in German I'm afraid): http://www.audax-speaker.de/index.p...=imported/tests-reviews/pro20d-hobby-hifi.pdf
Impressive deign ! The interesting parts are missing though, crossover and dimensions. The crossover was very simple for the Neo10, it relied on it's own rolloff and had a higpass only 6 dB/octav at 300 Hz, lowpass also 6 dB at 1500 Hz and also two notchfilters at 9.6 kHz and 2250 Hz all according to the measurements presented in the article. Obviously Proraum didn't see any problem with this crossover and B&G themselves state 2nd order 250 Hz as a minimum.
But you do need an exellent bass to accompany !
/Erling
mayhem13,
since you brought it up. German Proraum produced a passive OB Neo10, Neo3 kit together with Usher basreflex bass. It was presented in Hobby HiFi january number 2008. Link is here (only in German I'm afraid): http://www.audax-speaker.de/index.p...=imported/tests-reviews/pro20d-hobby-hifi.pdf
Impressive deign ! The interesting parts are missing though, crossover and dimensions. The crossover was very simple for the Neo10, it relied on it's own rolloff and had a higpass only 6 dB/octav at 300 Hz, lowpass also 6 dB at 1500 Hz and also two notchfilters at 9.6 kHz and 2250 Hz all according to the measurements presented in the article. Obviously Proraum didn't see any problem with this crossover and B&G themselves state 2nd order 250 Hz as a minimum.
But you do need an exellent bass to accompany !
/Erling
Thank you for the link!.......and yes it appears to be an excellent design....one such that the designer decided to forgoe the OB bass. I'd like to know why but hey, it's not the $64,000 question either.
I'll be trying to sim up the passive top end with some of the info in the PDF. Invaluable...thank you again!...one such that the designer decided to forgoe the OB bass.
I'd like to know why but hey, it's not the $64,000 question either.
Hi,
That is fairly simple why, maximum bass SPL for the frontal baffle area,
and the fact the bass drivers aren't far more sensitive than the mid/treble.
Still those two 8" units would cream the two 15'ers suggested here for
maximum bass levels, considerably around the port tuning frequency.
OB baffle loss is not just frequency response like a box, it is chucking
away driver excursion as well, such that OB's simply don't do loud bass
for the driver sizes, why you need massive bass drivers to work well.
rgds, sreten.
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