Just thinking off the top of my head... and couldn't find many threads on the Em 15" that I've heard is popular for the low end in a open box speaker. Saw Nelson's at BAF 09....
Anyway, noticed that the Dayton DC380-8 15" woofer is on Black Friday sale (till Sunday) for almost half price: Parts Express: Featured Categories Black Friday which puts it at $35.
Wonder if anyone has any experience with this one? Qts is lower than the other, have no idea how clean it may be, and how low/high it could go, compared to the Eminence 15b. Might be a nice deal. Time is limited, though!
Anyway, noticed that the Dayton DC380-8 15" woofer is on Black Friday sale (till Sunday) for almost half price: Parts Express: Featured Categories Black Friday which puts it at $35.
Wonder if anyone has any experience with this one? Qts is lower than the other, have no idea how clean it may be, and how low/high it could go, compared to the Eminence 15b. Might be a nice deal. Time is limited, though!
Hello....
The PE 15" could be a interesting opportunity... the way to make the best of this would be to use 2 in parallel... and a fairly large series inductor.... say a 10-12 mh iron core. Baffle width of about 18" and a 6 inch or so average depth slanted back wings.
Your OB operating efficiency will be the same as a single Emi Alpha 15... that is set by your baffle width...( f= & F peak values) but your pair of PE's will work half as hard or be able to play twice a loud. The PE's lower FS is a plus too. Not bad for $70 a pair delivered... (about the same as you wouild pay for one Alpha) assuming you get 4 of them. and... with the extra displacement you can also play about a half octave lower.
Add a typical OB appropriate 8" mid range (there are a bunch of choices) and traditional tweeter.
I have cobbled several different versions of the above... the best being dual Goldwood 1858 18's and all I can say is WOW!... YMMV...
John
The PE 15" could be a interesting opportunity... the way to make the best of this would be to use 2 in parallel... and a fairly large series inductor.... say a 10-12 mh iron core. Baffle width of about 18" and a 6 inch or so average depth slanted back wings.
Your OB operating efficiency will be the same as a single Emi Alpha 15... that is set by your baffle width...( f= & F peak values) but your pair of PE's will work half as hard or be able to play twice a loud. The PE's lower FS is a plus too. Not bad for $70 a pair delivered... (about the same as you wouild pay for one Alpha) assuming you get 4 of them. and... with the extra displacement you can also play about a half octave lower.
Add a typical OB appropriate 8" mid range (there are a bunch of choices) and traditional tweeter.
I have cobbled several different versions of the above... the best being dual Goldwood 1858 18's and all I can say is WOW!... YMMV...
John
Aha...
Well, interesting in that I just got back from much reading around on Martin's OB projects and other stuff... basically doing the homework I should have done before posting this. I see the benefit of having a Qts of about double or more of a single DC380... though I guess EQ'ing might make up for it.
John's suggestion of doubling them up works, and has other benefits... though compact size isn't one of them. (Hey, I'm spoiled by all the small speaker boxes I've had so far!) Nothing like having vast tracts of cone area to move lots of air...
So, even though it might not be a first choice driver, looks like the Black Friday(till Sunday) sale price is a worthy deal for those considering a big OB build.
Well, interesting in that I just got back from much reading around on Martin's OB projects and other stuff... basically doing the homework I should have done before posting this. I see the benefit of having a Qts of about double or more of a single DC380... though I guess EQ'ing might make up for it.
John's suggestion of doubling them up works, and has other benefits... though compact size isn't one of them. (Hey, I'm spoiled by all the small speaker boxes I've had so far!) Nothing like having vast tracts of cone area to move lots of air...
So, even though it might not be a first choice driver, looks like the Black Friday(till Sunday) sale price is a worthy deal for those considering a big OB build.
I have four low Qts 15" drivers just like those, they have been sitting in my basement for years after being replaced with Eminence Alpha 15A drivers. The SPL/w/m, Qts, and Xmax are all too low. My advice is to not jump for the low price and get the Alpha 15A drivers for an OB or H frame. Those drivers are not intended for an OB, sometimes the deal is no deal.
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Martin... I humbly disagree....
Martin...
Good to see your post... your work has been so supportive of OB applications...
But...
One way or the other... you must trade low Q and it's intrinsic efficiency advantage for a higher Q in an OB application. And I will bet you a "C" note that the two PE 15" drivers will out perform a single Alpha EMI 15. Yes you will trade the dual drivers efficiency away to get there.. but using a big inductor will raise the system Q... and the doubling of surface area with equal or greater Xmax will swamp the Higher Q advantage the Alpha offers. The Iron law is the Iron law ... and yes I have played with the Alpha... and yes as a simple single woofer solution in an OB application for low dollars it is hard to beat... but the two PE 15's per side wired in parallel will leave it in the dust when properly implemented... been there and done that!
Best
John
Martin...
Good to see your post... your work has been so supportive of OB applications...
But...
One way or the other... you must trade low Q and it's intrinsic efficiency advantage for a higher Q in an OB application. And I will bet you a "C" note that the two PE 15" drivers will out perform a single Alpha EMI 15. Yes you will trade the dual drivers efficiency away to get there.. but using a big inductor will raise the system Q... and the doubling of surface area with equal or greater Xmax will swamp the Higher Q advantage the Alpha offers. The Iron law is the Iron law ... and yes I have played with the Alpha... and yes as a simple single woofer solution in an OB application for low dollars it is hard to beat... but the two PE 15's per side wired in parallel will leave it in the dust when properly implemented... been there and done that!
Best
John
Drive power issue
Power requirements will be set by the usual parameters...
How loud, how deep, how big a room, music content, baffle width and so on.
With all that in mind.... and assuming a dual (parallel) PE OB 15" set up on an 18" wide baffle with 6" wing depth... and the inductor to get this system to play flat into the upper 30's, you will end up around 84 DB/watt at one meter... give or take. So 10 watts will produce 93 db or so... 100 watts about 102. For a stereo pair add about 3 db. Truth be told... you are going to be x-max limited from about 40 hz down. This will be about a 4.5 ohm load in the low end...so if you are using a solid state amp that is a plus.... if using a tube amp... you will be pushing things.
Hope this opinion helps...
Power requirements will be set by the usual parameters...
How loud, how deep, how big a room, music content, baffle width and so on.
With all that in mind.... and assuming a dual (parallel) PE OB 15" set up on an 18" wide baffle with 6" wing depth... and the inductor to get this system to play flat into the upper 30's, you will end up around 84 DB/watt at one meter... give or take. So 10 watts will produce 93 db or so... 100 watts about 102. For a stereo pair add about 3 db. Truth be told... you are going to be x-max limited from about 40 hz down. This will be about a 4.5 ohm load in the low end...so if you are using a solid state amp that is a plus.... if using a tube amp... you will be pushing things.
Hope this opinion helps...
How did you come up with those performance values? What size inductor and how much will it cost? At what frequency and SPL (at what input power) do you hit Xmax? What simulation tool did you use to do the calculations?
I tried modeling what you described this morning and cannot get anything close to what you have stated. Adding an inductor rolls off the response above the lowest frequency so you end up with a hump and no extended bass output (probably one note bass). The mid or full range driver would need to be crossed very low. I could not get bass below 40 Hz with any reasonable efficiency. In the end, I had a hard time even reproducing the response produced by one Alpha 15a in the same sized baffle.
I guess I am still sticking with my original posted recommendation. This is the wrong Dayton driver for an OB.
My own experience is that Q is the more important factor. I've got a bunch of low Q drivers collecting dust in my basement. You can fix with proper electronics, but why going to the trouble when a few simple dollars can buy you exactly what you need for OB? Stay with high Q forget about the Dayton for this application.
Similarly, high Q drivers are 'no good' in sealed or ported. Life is sometime difficult!
Similarly, high Q drivers are 'no good' in sealed or ported. Life is sometime difficult!
Martin, it's too bad you and John are on opposite coasts. You would have have a lot of fun getting together. Maybe some time at RMAF or LSAF.
FWIW, John has been building OB speakers since I was in knee pants. Of course longevity does not always = talent, but John does know what he is doing. He's not talking out of his (you know what).
I've built a couple of John's designs and heard many more. They DO have bass, usually plenty of it. As you know, there are a lot of gutless OB rigs out there - John's are not.
They also have excellent tonal balance and imaging.
I have also tried to simulate John's designs in software, yours and others, and it just doesn't look right. Then I hear them and think "holy crap! - how can it sound so good when it looks so wrong on paper?" Jedi mind tricks, or something.
Anyhow, it's fun to see the different approaches. One born of math and calculations, the other born of decades of "just do it." Both work. Both are based on the same physics. It would be fun to turn you both loose on your choice of drivers. The results might be more alike than different.
FWIW, John has been building OB speakers since I was in knee pants. Of course longevity does not always = talent, but John does know what he is doing. He's not talking out of his (you know what).
I've built a couple of John's designs and heard many more. They DO have bass, usually plenty of it. As you know, there are a lot of gutless OB rigs out there - John's are not.
They also have excellent tonal balance and imaging.
I have also tried to simulate John's designs in software, yours and others, and it just doesn't look right. Then I hear them and think "holy crap! - how can it sound so good when it looks so wrong on paper?" Jedi mind tricks, or something.
Anyhow, it's fun to see the different approaches. One born of math and calculations, the other born of decades of "just do it." Both work. Both are based on the same physics. It would be fun to turn you both loose on your choice of drivers. The results might be more alike than different.
"Just do it" is fine if you have done it and can show documented and measured results. If you have not done it already (either through building or calculations) then it is pure speculation with nothing behind the recommendation. I am looking to see what is behind the recommendations in this case. I don't take anything based on face value any more no matter the reputation/qualifications of the poster. If you make a recommendation based on physics it should not be too hard to provide some basic simple analysis or description to back it up. That is all I am asking for in this case.
I see way too many off the cuff designs posted by people speaking from a position of authority that quite frankly don't hold water. This is particularly true with more off the beaten path configurations like TLs, horns, and dipoles. Just to be clear, I do not consider myself the ultimate authority in any aspects of dipole design. But I do try and provide some technical basis for my posts, worksheets, and documentation. I did the math before I asked the above questions.
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Sorry Martin. I know your work - and I know John's. You may not like it or understand it, but his stuff is far from "off the cuff."
It's a shame not to be interested. I am always open to learn from those who do good work. But yes, judging from what is posted is very difficult, no doubt about it.
The main problem with forums like this is that we can't hear the work in question. A lot of numbers or subjective rants get thrown around the forums, because that's all we have. That leads to endless arguments over silly stuff. I don't hear these arguments when people actually get together and listen to the work. I've been lucky enough to meet a good number of forum members and hear their work. From that it is easier to judge what is being posted. Most forum members are not so lucky....
It's a shame not to be interested. I am always open to learn from those who do good work. But yes, judging from what is posted is very difficult, no doubt about it.
The main problem with forums like this is that we can't hear the work in question. A lot of numbers or subjective rants get thrown around the forums, because that's all we have. That leads to endless arguments over silly stuff. I don't hear these arguments when people actually get together and listen to the work. I've been lucky enough to meet a good number of forum members and hear their work. From that it is easier to judge what is being posted. Most forum members are not so lucky....
It has nothing to do with liking it or not. A recommendation was made which I don't understand and can not verify. I am asking some questions that is all. I will stop posting.
Keeping perspective....
Hello Martin....
OK... need to set a few things straight...
First.... your work in the DIY OB field is the GOLD STANDARD. Your math and principles are solid and repeatable. I and many others in the DIY community so appreciate your hard work.
Second... my post was not intended to question your position... integrity or conclusions... it was intended to stimulate others to learn about potential OB applications... designs. As my Pa used to say... "there are other ways around the barn". And... I think most designers will agree that "art" can be a lot of the design process. As tag on my reply stated... "I HUMBLY disagree".
Third... I have purchased 4 of the PE 15's in question and will put together a viable design and post what I come up with as well as measurements produced using True RTA Real Time Audio Spectrum Analyzer. As you know... projects can take a lot of time... but I will do my best to expedite.
Fourth... I think Pano's point was to validate my credibility as a experienced designer... it in no way was questioning your abilities. As stated above... you are well known and well regarded. I.. OTOH... am not as well known.
Fifth.... I do hope you continue to post... it would be a shame if you do not.... but I do understand and respect your decision.
Sixth.... In my defense.... I have built so many OB designs I have lost count. A lot of them were poor to worthless. But I have learned ... empirically... what works. And I take my better creations out into the real world... be it LSAF, RMAF or NC DIY. Like you I share... It's all about learning and having some fun - enjoyment along the way. I also admit I do not have your considerable math skills and am lesser for it. I use my 50 years of hands on experience and intuition.
In a post to follow... I will provide more general info about what I plan to do and what knowledge I use to support my decisions.
Best
John
Hello Martin....
OK... need to set a few things straight...
First.... your work in the DIY OB field is the GOLD STANDARD. Your math and principles are solid and repeatable. I and many others in the DIY community so appreciate your hard work.
Second... my post was not intended to question your position... integrity or conclusions... it was intended to stimulate others to learn about potential OB applications... designs. As my Pa used to say... "there are other ways around the barn". And... I think most designers will agree that "art" can be a lot of the design process. As tag on my reply stated... "I HUMBLY disagree".
Third... I have purchased 4 of the PE 15's in question and will put together a viable design and post what I come up with as well as measurements produced using True RTA Real Time Audio Spectrum Analyzer. As you know... projects can take a lot of time... but I will do my best to expedite.
Fourth... I think Pano's point was to validate my credibility as a experienced designer... it in no way was questioning your abilities. As stated above... you are well known and well regarded. I.. OTOH... am not as well known.
Fifth.... I do hope you continue to post... it would be a shame if you do not.... but I do understand and respect your decision.
Sixth.... In my defense.... I have built so many OB designs I have lost count. A lot of them were poor to worthless. But I have learned ... empirically... what works. And I take my better creations out into the real world... be it LSAF, RMAF or NC DIY. Like you I share... It's all about learning and having some fun - enjoyment along the way. I also admit I do not have your considerable math skills and am lesser for it. I use my 50 years of hands on experience and intuition.
In a post to follow... I will provide more general info about what I plan to do and what knowledge I use to support my decisions.
Best
John
Hi
With my little experienced in passive OB, i think John's solution is good, 2 subwoofers in parallel to have a good power handling.
In a passive crossover, the total Q of the system will rise 0.35 to 0.5, observed in most of cases.
0.5 is optimum to have the best phase response in the bass
but not the best level.
The problem with 2 woofers you should have a big amplifier to handle them. Not an easy task.
If you use active crossover, no problem you can equalize the driver but I think it will be useless in this case, just equalize the OB.
I think it depends on the point of view and taste if you want best phase response, use the Dayton Q~0.5. If you want more level use the Eminence Q~1.
More level, the loudspeaker is "slower", less Q (I personally prefer), less level the speaker is "faster", ears is very sensitive on the quality of the phase in the bass. In the graph you see the evolution of the level response versus Q.
Not really opposite point of view between John and Martin but different conception of the problem. None of these solutions are perfect.
Have fun
With my little experienced in passive OB, i think John's solution is good, 2 subwoofers in parallel to have a good power handling.
In a passive crossover, the total Q of the system will rise 0.35 to 0.5, observed in most of cases.
0.5 is optimum to have the best phase response in the bass
but not the best level.The problem with 2 woofers you should have a big amplifier to handle them. Not an easy task.
If you use active crossover, no problem you can equalize the driver but I think it will be useless in this case, just equalize the OB.
I think it depends on the point of view and taste if you want best phase response, use the Dayton Q~0.5. If you want more level use the Eminence Q~1.
More level, the loudspeaker is "slower", less Q (I personally prefer), less level the speaker is "faster", ears is very sensitive on the quality of the phase in the bass. In the graph you see the evolution of the level response versus Q.
Not really opposite point of view between John and Martin but different conception of the problem. None of these solutions are perfect.
Have fun
Dual DC380-8 OB design fodder...
Hello again all....
OK.... some data and conclusions to chew on....
My basic OB design considerations on what I have been posting the last couple of days....
From the published PE Specifications for the DC 380-8 15" Classic woofer....
RE= 6.5 each... for two in parallel about 3.3 ohms
Raw unbaffled QT= .35
SD each = 835 sq. cm.
Xmax = 4.35 MM Peak
Advertised sensitivity = 92.8.
This driver has an extended ... vented pole piece with a rear bump plate. Vance Dickason and others assume you can get an additional 15% of excursion before the Motor BL collapses... especially with a relatively low Xmax (assuming a BL of at least 70% or so)... this is what I have found to be true in the past.... so for this exercise I am assuming the usable peak to peak value of this driver to be 10 MM. BTW.. the motor for this driver is rather strong with a BL value of about 20.
Complete specs on this driver are here: http://www.parts-express.com/pdf/295-325s.pdf
But you have to be some what skeptical about specs... if you run the math to verify true sensitivity... you end up with more like 90.7 DBW (.74%). I obtained this value here: mh-audio.nl - Home. With the two drivers operating in parallel and allowing most of a DB lose in sensitivity... we end up with a usable raw sensitivity of 96 db. This is our starting point and in the design we will trade away 12 db of this to obtain a flat response into the upper 30's claimed in my post.
And we need to account for resistance effects on total Q for the driver pair... and I assume the inductor and other operating paracitics (sp?) will be at least 1 ohm... so we go here to see what the new operation value will be... mh-audio.nl - Calculations
We will end up close to an operating QTS on baffle of 0.50.
In the next post I will cover the calculated OB... actually a partial Cardioid F peak & F equal issues.
Hello again all....
OK.... some data and conclusions to chew on....
My basic OB design considerations on what I have been posting the last couple of days....
From the published PE Specifications for the DC 380-8 15" Classic woofer....
RE= 6.5 each... for two in parallel about 3.3 ohms
Raw unbaffled QT= .35
SD each = 835 sq. cm.
Xmax = 4.35 MM Peak
Advertised sensitivity = 92.8.
This driver has an extended ... vented pole piece with a rear bump plate. Vance Dickason and others assume you can get an additional 15% of excursion before the Motor BL collapses... especially with a relatively low Xmax (assuming a BL of at least 70% or so)... this is what I have found to be true in the past.... so for this exercise I am assuming the usable peak to peak value of this driver to be 10 MM. BTW.. the motor for this driver is rather strong with a BL value of about 20.
Complete specs on this driver are here: http://www.parts-express.com/pdf/295-325s.pdf
But you have to be some what skeptical about specs... if you run the math to verify true sensitivity... you end up with more like 90.7 DBW (.74%). I obtained this value here: mh-audio.nl - Home. With the two drivers operating in parallel and allowing most of a DB lose in sensitivity... we end up with a usable raw sensitivity of 96 db. This is our starting point and in the design we will trade away 12 db of this to obtain a flat response into the upper 30's claimed in my post.
And we need to account for resistance effects on total Q for the driver pair... and I assume the inductor and other operating paracitics (sp?) will be at least 1 ohm... so we go here to see what the new operation value will be... mh-audio.nl - Calculations
We will end up close to an operating QTS on baffle of 0.50.
In the next post I will cover the calculated OB... actually a partial Cardioid F peak & F equal issues.
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