Hi!
Very interensting speakers. A friend of mine has a pair of Duevel Planets, which use the same theory and I must say they seem to be great allrounders. I´m not sure that they are for me, though.. They have some wonderful qualities but they sacrifice too much of insight and the soundstage, while big, lacks the ability to make me pin-point where things are taking place. They sound a bit artificial.. I love the fact that sounds originates in thin air but I´m not sold.. For filling a room with sound they are excellent, but when I want to listen more actively they simply dont deliver..
A combination of the Planets and what I have today would be ideal..
I can very well imagine that the Planets just do what you describe ! But they should not be compared with my speakers
Demokrit is very different in this respect and Demokrit-T even more so. You can look into the stage and point exactly what instrument/musician is located where in width and depth.
Too bad Sweden is so far. Otherwise you just could pop in and convince yourself.
So, I see the Planets more like a design gag to be honest and not like a serious speaker.
But poke around, learn a bit and then decide.
The little Vifa is very nice, but I don't think it would satisfy me as a midrange driver. Maybe very near field, like desktop. But it doesn't cost much to try! You may be able to get it to mate to your sub OK at 120Hz. Worth a try.
You didn't like the idea of Seas 8"? It's a really good driver.
You may be able to get it to mate to your sub OK at 120Hz. Worth a try.You didn't like the idea of Seas 8"? It's a really good driver.
That is quite a distance to bridge vor both, omni and OB. For that you could potentially need more directional speakers or move them closer to you if possible.
I´ve looked at the Seas driver, and it seems to be a nice driver. I didn´t know that a driver as big as 8" could manage the entire frequency range. Seas recommends a closed box of 60L or a BR of 70L but will they work in an OB? A QTS of .35 seems a bit low.. From what I´ve read the optimum driver for an OB should have a high QTS but when frequencies lower than 120Hz (or up to 160Hz) is no issue I guess it wont matter that much.
Looking at the Seas I came across another promising candidate.. Visaton B200. I found an OB from Visaton called "Nobox" where the B200 is crossed over at 250Hz. Maybe it can be made to perform down to 150Hz?
I´ve just found something interesting...
http://www.diyaudio.com/forums/full-range/170079-new-alpair-7-small-ob-project.html
A small, cheap Alpair 7 driver in a small Open Baffle crossed over to subs around 140-150Hz.. Reading the listening impressions they just might be perfect. As far as I can tell it seems that no passive crossover whatsoever is used so a simpler build must be hard to find..
I could´nt find any measurements on the baffle, though.. Is it not that critical? And what about baffle step correction or some frequency respons correction? Is the Alpair driver so good that it doesnt need any ? I guess that is a question for the fullrange section of this forum, but since the discussion is up and running I keep it here.
*Edit*
The baffle seems to be as wide as the Nht Sub 2 that it sits on.. = 13". So I guess that 13x15" would be about right. My subs are only 25cm (about 10") wide, but looks are not everything..
http://www.diyaudio.com/forums/full-range/170079-new-alpair-7-small-ob-project.html
A small, cheap Alpair 7 driver in a small Open Baffle crossed over to subs around 140-150Hz.. Reading the listening impressions they just might be perfect. As far as I can tell it seems that no passive crossover whatsoever is used so a simpler build must be hard to find..
I could´nt find any measurements on the baffle, though.. Is it not that critical? And what about baffle step correction or some frequency respons correction? Is the Alpair driver so good that it doesnt need any ? I guess that is a question for the fullrange section of this forum, but since the discussion is up and running I keep it here.
*Edit*
The baffle seems to be as wide as the Nht Sub 2 that it sits on.. = 13". So I guess that 13x15" would be about right. My subs are only 25cm (about 10") wide, but looks are not everything..
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Shylock, that may indeed be the way for you to go. Sounds like you aren't ready to design anything on your own and that your budget constraints put most of the limited number of proven OB designs out of reach. A high quality full ranger could give you what you want and keep everything relatively simple. Dave/Planet10 talks highly of the Mark audio line.
If you haven't already, download this, the Baffle Diffraction & Boundary Simulator from here:
jbagby
Set the Selected Baffle Mode to 'Mononpole Box' and the Baffle Diffraction Modeled As to 'Loss' to see what different baffle and driver sizes do to the freq. response. What you want to note is that as the baffle goes wider and wider, the F3 point also gets lower but it still drops off much more than when the driver is in any type of enclosure.
Below is a quick, rough sim of the Alpair7 on a 16" x 46" baffle (include the size of the sub baffle too) just to give you an idea of what it looks like. (Just to let you know, I used a couple more programs to get to this result)
That must be a very sweet sounding driver indeed because its FR on that baffle without a XO is far from flat. It looks like it also needs to be XO'd to the sub at about 250Hz not 120Hz. Some XO work can probably help this out, but trying something like this just raw might be a good way to start out. If it doesn't seem right after that, then you might try shaping the curve with some passive components.
Personally, given your budget I would probably look at some even higher quality and slightly larger full range drivers too (a little more LF response hopefully), like the Alpair10 perhaps. If this is the way you want to go, then taking this to the Full Range forum might be a smart idea.
Cheers
If you haven't already, download this, the Baffle Diffraction & Boundary Simulator from here:
jbagby
Set the Selected Baffle Mode to 'Mononpole Box' and the Baffle Diffraction Modeled As to 'Loss' to see what different baffle and driver sizes do to the freq. response. What you want to note is that as the baffle goes wider and wider, the F3 point also gets lower but it still drops off much more than when the driver is in any type of enclosure.
Below is a quick, rough sim of the Alpair7 on a 16" x 46" baffle (include the size of the sub baffle too) just to give you an idea of what it looks like. (Just to let you know, I used a couple more programs to get to this result)
That must be a very sweet sounding driver indeed because its FR on that baffle without a XO is far from flat. It looks like it also needs to be XO'd to the sub at about 250Hz not 120Hz. Some XO work can probably help this out, but trying something like this just raw might be a good way to start out. If it doesn't seem right after that, then you might try shaping the curve with some passive components.
Personally, given your budget I would probably look at some even higher quality and slightly larger full range drivers too (a little more LF response hopefully), like the Alpair10 perhaps. If this is the way you want to go, then taking this to the Full Range forum might be a smart idea.
Cheers
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Yes, they will work very well indeed from about 80Hz up on Open Baffle - depending of course on baffle size. For 120Hz up you don't need a big baffle or a high Qts driver. For bass, you do.
I'll dig up the OB measurements for you.
"jReave"
Hmm.. That did not look good.. A 15dB difference between 500 and 1500Hz..
I´ve read the Alpair 7 OB-thread several times but I cant fint anything that mentions the use of any passive components whatsoever but a frequency respons like the one in your simulation must sound a bit strange. They seem to be very happy with the sound, though so my guess is that there is more to the Alpair OB than meets the eye..
You are right in your assumption that I´m not ready to design my own OB just yet. For that very reason I´m scanning the internet in search of designs and this Alpair seemed to be perfect. It even has som WAF-factor.. Your simulation of the Alpair 7 has made me think again and I have a hard time believing that the Alpair 7 OB-project can sound any good. Weak respons under 250Hz, and still crossed over at 140-150Hz.. A frequency response curve with a 15dB variation.. What we have here must be an amazing relation between a speaker and the room it sits in.
"Pano"
Just how big would the baffle have to be to reach 120Hz (or at least 150) with the seas driver? It does have a more suitable size for some midbass impact but my fear is that such a large driver might be much more directional and have a really small sweetspot.
Have you done a build with the Seas? Your experience with the driver would be very appreciated.
Hmm.. That did not look good.. A 15dB difference between 500 and 1500Hz..
I´ve read the Alpair 7 OB-thread several times but I cant fint anything that mentions the use of any passive components whatsoever but a frequency respons like the one in your simulation must sound a bit strange. They seem to be very happy with the sound, though so my guess is that there is more to the Alpair OB than meets the eye..
You are right in your assumption that I´m not ready to design my own OB just yet. For that very reason I´m scanning the internet in search of designs and this Alpair seemed to be perfect. It even has som WAF-factor.. Your simulation of the Alpair 7 has made me think again and I have a hard time believing that the Alpair 7 OB-project can sound any good. Weak respons under 250Hz, and still crossed over at 140-150Hz.. A frequency response curve with a 15dB variation.. What we have here must be an amazing relation between a speaker and the room it sits in.
"Pano"
Just how big would the baffle have to be to reach 120Hz (or at least 150) with the seas driver? It does have a more suitable size for some midbass impact but my fear is that such a large driver might be much more directional and have a really small sweetspot.
Have you done a build with the Seas? Your experience with the driver would be very appreciated.
Shylock, sorry, it wasn't my intent to turn you off of the Alpair7, just to do a quick sim to get an idea of what it was doing down in the lower frequencies from a guestimate of the baffle size used in the project. I've never used it, but those are some pretty positive real world reviews and I know that others concur.
Understand that the response can still be shaped to a fair degree by changing the baffle size and driver positioning and/or by using some passive XO components. If you don't have a feel for the baffle stuff yet, again you should really download that program I mentioned before. It's incredibly easy to use and you'll learn something in the process. (requires MS excel tho)
Below are a few more sims on the Alpair7 to give you some further info.
Image 1 - Alpair7 as before on a 16" x 46" baffle, driver in the center, 33" high but now with a Zobel, a RL contour filter and a notch filter
Image 2 - Naked FR on 12" x 49" baffle, driver 8" from the left side, 38" high and edges rounded over 1/2"
Image 3 - Same as image 2 but now with the XO components
Notice that by changing the baffle and driver placement, you get rid of most of the suck-out between 1000 and 2000Hz. And notice too that you lose a fair amount of dB (or in other words efficiency) when you flatten the response electrically. This is what some will consider one of the main drawbacks of an OB design. In order to effectively increase the bass response, you have to drop the rest of the response in the higher frequencies.
In your situation, you've got I think 130W of power available from that Denon AVR. From image 3, let's call sensitivity at about 77dB. Output increases 3dB every time you double the wattage. So 2W = 80dB, 4W = 83, 8W = 86, 16W = 89, 32W = 91, 64W = 93 and 128W = 96dB. You're not going to wake the neighborhood with these things and your room is somewhat large, but given the need for headroom, if you listen around 90dB or less you should probably be alright. (Haven't looked at what the xmax limit in terms of dB's will be here tho)
Again, with the right baffle, you might want to try it - or another full ranger - just raw to start off with and then only if you think it needs it, try it with the XO components.
Anyways, just trying to give you some tools and a little more info to make decisions with.
Cheers
Understand that the response can still be shaped to a fair degree by changing the baffle size and driver positioning and/or by using some passive XO components. If you don't have a feel for the baffle stuff yet, again you should really download that program I mentioned before. It's incredibly easy to use and you'll learn something in the process. (requires MS excel tho)
Below are a few more sims on the Alpair7 to give you some further info.
Image 1 - Alpair7 as before on a 16" x 46" baffle, driver in the center, 33" high but now with a Zobel, a RL contour filter and a notch filter
Image 2 - Naked FR on 12" x 49" baffle, driver 8" from the left side, 38" high and edges rounded over 1/2"
Image 3 - Same as image 2 but now with the XO components
Notice that by changing the baffle and driver placement, you get rid of most of the suck-out between 1000 and 2000Hz. And notice too that you lose a fair amount of dB (or in other words efficiency) when you flatten the response electrically. This is what some will consider one of the main drawbacks of an OB design. In order to effectively increase the bass response, you have to drop the rest of the response in the higher frequencies.
In your situation, you've got I think 130W of power available from that Denon AVR. From image 3, let's call sensitivity at about 77dB. Output increases 3dB every time you double the wattage. So 2W = 80dB, 4W = 83, 8W = 86, 16W = 89, 32W = 91, 64W = 93 and 128W = 96dB. You're not going to wake the neighborhood with these things and your room is somewhat large, but given the need for headroom, if you listen around 90dB or less you should probably be alright. (Haven't looked at what the xmax limit in terms of dB's will be here tho)
Again, with the right baffle, you might want to try it - or another full ranger - just raw to start off with and then only if you think it needs it, try it with the XO components.
Anyways, just trying to give you some tools and a little more info to make decisions with.
Cheers
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I personally have not, no - tho I've built with several other 8" FR drivers on OB supported by woofers.
So why do I continue to praise this driver? Because several people I know have built with it and been very happy. They have high praise for them and I've seen the measurements. It's an easy driver to get right in this application (important!) and has low distortion.
Below is a sample measurement of the Seas on a rather small OB. That's the actual FR at the listening position just popped into a random baffle. 120Hz? No, but a bigger baffle could do it. Placing it off center helps smooth the response even more.
Caveat: Not everyone likes 8" midrange drivers - I do.
I remember a very busy room I hosted at the Montreal Son et Lumiere show a few years ago. We had 3 speakers that were the same except for the size of the driver and box. All the same brand full range driver, one front, one on the back. We had 8", 6.5" and 4.5" versions. The 8" sounded best to me for overall balance and reality. But many of the 100s who came thru really liked the 4.5" version. It did something they really liked. I found it nice, but "small" sounding. Tastes vary.
I really like the 8" full range on open baffle with helper woofers. It sounds great, open and real. And with the right driver is easy to make it work the way it should. The Seas 8" is one of those drivers. Again, see below what it can do in room with little effort and no EQ or crossover. You can see the baffle peak circa 350Hz and the roll-off below that. You need a -6dB point about an octave below that. The baffle size for that can be calculated.
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Hi Pano,
can you please provide some details about your mid sized OB that you refer here..regarding drivers used and approximate dimensions. Thanks
Mid sized were the Manzanita project. See here:
Fast, fun, Inexpensive OB project - Page 46 - diyAudio
Fast, fun, Inexpensive OB project - Page 46 - diyAudio
"jReave"
I really appreciate that you are taking the time to do these simulations.
Pic 3 actually looks rather nice.. Not perfect, but in the right room we start to get to a point where the sounding result can be good.
I´ve noticed a big problem with the alpair 7 driver though.. With a sensitivity of 77dB my amp is more han up to the task of giving me the level of sound I need (I typically average 80dB and thats when I´m playing loud..) and the occasions when I feel the need to crank the system is few and far between.
The specs of the alpair driver states that it can handle a maximum of 20W rms.. With a sensitivity of 77dB (at 1m.. With the speakers 1m from the wall I will still be 3m from them = even lower sensitivity at the listening position), that would equal a maximum output of...well, if I want to maintain atleast a 10dB headroom (many of my recordings have a crest value of significantly more..) it simply wont work.. I don´t know if the Alpair is limited by its maximum excursion, capacity of the voice coil or what the deal is, and it might take some more power above 150Hz but..
Another worry is how many of the nice characteristics in the Alpair 7 that remain being so heavily filtered..
I still like the driver, but I guess a small sealed or BR enclosure simply suits it better. The drivers are affordable so I will order a pair today and try one of the more conventional builds to see what it can do. I will still try an OB though, but not with this driver.
"Pano"
That does not look half bad.. I don´t have Excel in my home computer (my kids have a break this week so I´ve taken the week off to keep them activated..) but I´m back at the office on Monday and I will give the software mentioned in the thread a try. It would be really great to find a thread will all the details (baffle size, possible filters and so on) and simply make a copy but I have not been able to find anything yet. I´m sure it´s out there, so I´ll keep on looking.
The driver I found when looking at the Seas, Visaton B200, is it comparable in quality to the Seas? It costs about the same here (a bit more expensive, but not to the point where it makes a difference) and with a high Qts it might be easier to push it down to 120-150Hz? Visaton has a kit called "Nobox BB" where this driver crosses over at 250Hz in a baffle with managable dimensions so maybe a -6db at 120Hz could be had in a smaller baffle than with the Seas? If outright soundquality of the Seas is much better, then I would consider a bigger baffle but a driver that is comparable in that respect but able to reach my bass extension requirement in a smaller baffle could be worth paying a little extra for..
I really appreciate that you are taking the time to do these simulations.
Pic 3 actually looks rather nice.. Not perfect, but in the right room we start to get to a point where the sounding result can be good.
I´ve noticed a big problem with the alpair 7 driver though.. With a sensitivity of 77dB my amp is more han up to the task of giving me the level of sound I need (I typically average 80dB and thats when I´m playing loud..) and the occasions when I feel the need to crank the system is few and far between.
The specs of the alpair driver states that it can handle a maximum of 20W rms.. With a sensitivity of 77dB (at 1m.. With the speakers 1m from the wall I will still be 3m from them = even lower sensitivity at the listening position), that would equal a maximum output of...well, if I want to maintain atleast a 10dB headroom (many of my recordings have a crest value of significantly more..) it simply wont work.. I don´t know if the Alpair is limited by its maximum excursion, capacity of the voice coil or what the deal is, and it might take some more power above 150Hz but..
Another worry is how many of the nice characteristics in the Alpair 7 that remain being so heavily filtered..
I still like the driver, but I guess a small sealed or BR enclosure simply suits it better. The drivers are affordable so I will order a pair today and try one of the more conventional builds to see what it can do. I will still try an OB though, but not with this driver.
"Pano"
That does not look half bad.. I don´t have Excel in my home computer (my kids have a break this week so I´ve taken the week off to keep them activated..) but I´m back at the office on Monday and I will give the software mentioned in the thread a try. It would be really great to find a thread will all the details (baffle size, possible filters and so on) and simply make a copy but I have not been able to find anything yet. I´m sure it´s out there, so I´ll keep on looking.
The driver I found when looking at the Seas, Visaton B200, is it comparable in quality to the Seas? It costs about the same here (a bit more expensive, but not to the point where it makes a difference) and with a high Qts it might be easier to push it down to 120-150Hz? Visaton has a kit called "Nobox BB" where this driver crosses over at 250Hz in a baffle with managable dimensions so maybe a -6db at 120Hz could be had in a smaller baffle than with the Seas? If outright soundquality of the Seas is much better, then I would consider a bigger baffle but a driver that is comparable in that respect but able to reach my bass extension requirement in a smaller baffle could be worth paying a little extra for..
I don't have any experience with the Visaton, so just don't know. They are mentioned often enough on these forums.
A higher Qts should give you a bit of a bass hump, which could help you down low. The advantage to the Seas is that they make very good drivers, well engineered. You may well be able to achieve good results with the B2000, I just don't know. An 8" FR on open baffle is not too hard to get right - it's a great approach to great sound.
A quick look in The Edge baffle software seems to indicate that you could achieve a -6dB point circa 120Hz with a 66X100 Cm baffle, maybe even smaller. Some small rear wings can help low end response without a huge baffle.
A higher Qts should give you a bit of a bass hump, which could help you down low. The advantage to the Seas is that they make very good drivers, well engineered. You may well be able to achieve good results with the B2000, I just don't know. An 8" FR on open baffle is not too hard to get right - it's a great approach to great sound.
A quick look in The Edge baffle software seems to indicate that you could achieve a -6dB point circa 120Hz with a 66X100 Cm baffle, maybe even smaller. Some small rear wings can help low end response without a huge baffle.
The B200 has an underhung motor with 4 mm linear coil travel (p-p). The SEAS has an overhung motor with 6 mm linear coil travel (p-p). Because of the different nature of underhung and overhung the SEAS will have almost twice the effective coil travel, making it capable of twice the SPL level at 120Hz compared to the B200.
For better LF extension on a smallish baffle without any equalisation, high Qtc drivers are the best bet. The Betsy driver is one such driver but will need taming of HF response as will most other ones including the Seas. If betsy is crossed to a tweeter you can have a small OB with the added benefit of better HF dispersion from the tweeter than a 6-8" FR driver doing the HF duties.
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"soundaatma"
I actually have a couple of tweeters laying around since previous builds. They are a pair of Morel MDT-32:s and a pair of Scanspeak D2905-9300:s.
I guess both pairs are more than 10 years old but they work fine.. (or did when they were last in a speaker)..
I like the idea of not having a crossover in the vocal range and with driver like the Seas I guess I wont need to use a tweeter (I wouldnt mind if one of the ones I have will do..) and it would look a lot better with just one, big driver..
I made a purchase last night.. I did order the Alpair 7 gen3 drivers, but also a cool little thing called a mini-dsp. A friend ordered one about a year ago but never used it, so I offered him the equivalent of 50$ and he sold it.. I´ve never used one, and I´m not sure of just what it can do but according to the seller I can use it to tailor the frequency response of a driver in an OB. With the mini-dsp came a microphone (Behringer 8000 something..?) and using some software he said I could put the driver in a baffle, make a measurement of the frequency response and then "import" it to the mini-dsp. The dsp then works it´s magic and hey presto: A flat response without the use of passive components and if I am willing to sacrifice some power (and the driver can handle it) it will extend the bass to where I want it to be aswell..
Sounds a bit hokus pokus to me bit it was cheap so I will definitely investigate what this little box can do.
I´ve been thinking about this: LAGAN Bänkskiva - bok, 126x60.6 cm - IKEA
If I cut it in half I end up with two baffles measuring 123x60,6x2,8cm.. That would be the perfect size for the baffles (looks-wise). If the mini-dsp can make just about any driver work in that size, than It will certainly be the best hifi purchase I´ve ever done in my life..
So, this day will be spent reading up on the mini-dsp and ordering the appropriate software for my needs. I also need something called "REW" and since I have no clue as to how the software works I have my work cut out for me..
Anyone here with experience in the mini-dsp department?
I actually have a couple of tweeters laying around since previous builds. They are a pair of Morel MDT-32:s and a pair of Scanspeak D2905-9300:s.
I guess both pairs are more than 10 years old but they work fine.. (or did when they were last in a speaker)..
I like the idea of not having a crossover in the vocal range and with driver like the Seas I guess I wont need to use a tweeter (I wouldnt mind if one of the ones I have will do..) and it would look a lot better with just one, big driver..
I made a purchase last night.. I did order the Alpair 7 gen3 drivers, but also a cool little thing called a mini-dsp. A friend ordered one about a year ago but never used it, so I offered him the equivalent of 50$ and he sold it.. I´ve never used one, and I´m not sure of just what it can do but according to the seller I can use it to tailor the frequency response of a driver in an OB. With the mini-dsp came a microphone (Behringer 8000 something..?) and using some software he said I could put the driver in a baffle, make a measurement of the frequency response and then "import" it to the mini-dsp. The dsp then works it´s magic and hey presto: A flat response without the use of passive components and if I am willing to sacrifice some power (and the driver can handle it) it will extend the bass to where I want it to be aswell..
Sounds a bit hokus pokus to me bit it was cheap so I will definitely investigate what this little box can do.
I´ve been thinking about this: LAGAN Bänkskiva - bok, 126x60.6 cm - IKEA
If I cut it in half I end up with two baffles measuring 123x60,6x2,8cm.. That would be the perfect size for the baffles (looks-wise). If the mini-dsp can make just about any driver work in that size, than It will certainly be the best hifi purchase I´ve ever done in my life..
So, this day will be spent reading up on the mini-dsp and ordering the appropriate software for my needs. I also need something called "REW" and since I have no clue as to how the software works I have my work cut out for me..
Anyone here with experience in the mini-dsp department?
The minidsp is one amazing gizmo that I feel is almost essential for any DIY speaker builder be it active or passive systems.
The large baffle sizes as suggested above by Pano would indeed be necessary to reach down to 120hz unless you have very high Qtc driver. Usually most of the high Qtc drivers dont tend to have a very extended HF response, so I mentioned about crossing over to a tweeter beyond 4K which is above vocal range. A small tweeter can have better HF dispersion too compared to a FR driver.
The Visaton 200 is perhaps the only one with a high Qtc and also extended HF response , but I have read that it is difficult to tame. In any case now with the miniDSP you can tweek to your heart's content You can easily shelve the Seas with this.
be it active or passive systems.The large baffle sizes as suggested above by Pano would indeed be necessary to reach down to 120hz unless you have very high Qtc driver. Usually most of the high Qtc drivers dont tend to have a very extended HF response, so I mentioned about crossing over to a tweeter beyond 4K which is above vocal range. A small tweeter can have better HF dispersion too compared to a FR driver.
The Visaton 200 is perhaps the only one with a high Qtc and also extended HF response , but I have read that it is difficult to tame. In any case now with the miniDSP you can tweek to your heart's content
You can easily shelve the Seas with this.
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