Hi everyone - as the title says I decided I want to build a pair of open-baffle full range speakers 
I have a Peter Daniel-copy Gainclone to drive them, so high sensitivity would be desirable, although not critical.
I would like to have just one full-range driver, supported by a bass unit if necessary. As far as building a case is concerned, I do have some carpentry tool and experience, although I would prefer something relatively simple to build.
The listening room is 3.5 x 4.5 metres, but I may be moving to a bigger space, so I want the speakers to be fairly universal in this respect.
I was looking at these drivers:
- Alpair 10.2 from Mark Audio - I really like these for their looks and engineering, but I’m not sure if they will work well in an open baffle?...
- Visaton B 200 - there are some great reviews on the net about these Visatons in a NoBox - but would I be able to modify the appearance of the NoBox bit? I really couldn’t live with a plain square box like this...
Any advice will be most appreciated.
I have a Peter Daniel-copy Gainclone to drive them, so high sensitivity would be desirable, although not critical.
I would like to have just one full-range driver, supported by a bass unit if necessary. As far as building a case is concerned, I do have some carpentry tool and experience, although I would prefer something relatively simple to build.
The listening room is 3.5 x 4.5 metres, but I may be moving to a bigger space, so I want the speakers to be fairly universal in this respect.
I was looking at these drivers:
- Alpair 10.2 from Mark Audio - I really like these for their looks and engineering, but I’m not sure if they will work well in an open baffle?...
- Visaton B 200 - there are some great reviews on the net about these Visatons in a NoBox - but would I be able to modify the appearance of the NoBox bit? I really couldn’t live with a plain square box like this...
Any advice will be most appreciated.
My first suggestion is that you visit Martin's (MJK's) site: www.quarter-wave.com
I have built a version of his small, passive OB using Fostex FF85k and Eminence Alpha 15a, which I like very much.
Martin's MathCAD worksheets include OB modeling, and I can recommend them as well.
There are at least two schools of philosophy as regards OB design. I admit that based on my experience, I side with Martin. YMMV
Cheers, Jim
I have built a version of his small, passive OB using Fostex FF85k and Eminence Alpha 15a, which I like very much.
Martin's MathCAD worksheets include OB modeling, and I can recommend them as well.
There are at least two schools of philosophy as regards OB design. I admit that based on my experience, I side with Martin. YMMV
Cheers, Jim
+1
I went with a Fostex fe103e over an Eminence Alpha 15A and they still make me smile.
I went with a Fostex fe103e over an Eminence Alpha 15A and they still make me smile.
Thanks for the link, very informative.
However, I decided that I really, really want to avoid crossover components on the full range driver... I could probably live with signal degradation and phase shifts in the bass, but I want to keep the main spectrum pure and "direct". This, unfortunately rules out both the NoBox and MJK's Fostex/Eminence design...
I could still try building a single-driver open baffle. How big a baffle would have to be to allow a full-range driver like Alpair 10.2 to go into the 60Hz regions? Is there a way to calculate (or approximate) this?
Or, would it be possible to use a bass driver that has significantly higher sensitivity than the fullrange and simply shape the bass driver response so that it matches fullrange's roll-off?
However, I decided that I really, really want to avoid crossover components on the full range driver... I could probably live with signal degradation and phase shifts in the bass, but I want to keep the main spectrum pure and "direct". This, unfortunately rules out both the NoBox and MJK's Fostex/Eminence design...
I could still try building a single-driver open baffle. How big a baffle would have to be to allow a full-range driver like Alpair 10.2 to go into the 60Hz regions? Is there a way to calculate (or approximate) this?
Or, would it be possible to use a bass driver that has significantly higher sensitivity than the fullrange and simply shape the bass driver response so that it matches fullrange's roll-off?
EV sp12b is as good as you are going to do.
make sure the baffle is big. if do a JE Labs baffle, add an in. to
the bottom of the sides so the front baffle is angled back a bit more.
if you go any smaller than this you are not going to get much bass
and it is not going to go very loud.
you are up against some very severe limitations with your parameters.
I have some in ply baffles if you want them. best offer. will do with
5 watts, better with 10 or 20.
make sure the baffle is big. if do a JE Labs baffle, add an in. to
the bottom of the sides so the front baffle is angled back a bit more.
if you go any smaller than this you are not going to get much bass
and it is not going to go very loud.
you are up against some very severe limitations with your parameters.
I have some in ply baffles if you want them. best offer. will do with
5 watts, better with 10 or 20.
Without any crossover on your full range driver, bass frequencies will generate large cone deflections and the associated distortion and compression. Mounted on an OB, the driver's motion is no longer controlled by an enclosure at low frequencies. This will get really bad as you turn up the volume. I would hazard a guess that this problem would be a bigger issue then anything a crossover might do (and I don't agree that a crossover is automatically bad) to the purity of the sound. It is all about trade-offs, I would keep the crossover.
Martin
I apologize for having my post to something, which I do not understand.
But common sense and my experience tells me no harm, if the full range driver is relieved of the lower frequencies, thus preserving their physical integrity. This course is essential if we like the large volume. (and our full range loudspeakers.) I think if we use an OB loudspeaker, the crossover is required. The most active crossover, and multiamp environment, I think.
Wacky Gyuri
P.S.:
Now I'm going to my brain runted, Martin says exactly what I am, just with different words.
Well, he just knows.
But common sense and my experience tells me no harm, if the full range driver is relieved of the lower frequencies, thus preserving their physical integrity. This course is essential if we like the large volume. (and our full range loudspeakers.) I think if we use an OB loudspeaker, the crossover is required. The most active crossover, and multiamp environment, I think.
Wacky Gyuri
P.S.:
Now I'm going to my brain runted, Martin says exactly what I am, just with different words.
Well, he just knows.
Last edited:
Is this based on experience? I would suggest trying both if you haven't experienced both. It's easy to try. Having tried both I can say that I have no issues with my crossover at 300Hz. As Martin suggested the benefits far outweigh the perceived drawbacks. Of course if you limit your listening to small acoustic groups with no upright bass, or drums, then listening with out a crossover can be quite rewarding. However as soon as any bass/volume is introduced you might find you prefer the crossover.
Joe
I know what you mean guys, and I realise I'm swimming against the current here. 
The reason I insist on crossover-less full range is that my experiences with other audio devices so far confirmed the simple truth - with every component you add, you take something away from the original information in the recording. I'm not talking about distortion, frequency response and such, but rather the emotion, the "soul" of music. I hope you understand what I'm trying to say...
So after some thinking and research I arrived at these two concepts: firstly open baffle, which is commonly described as pure and direct, and secondly full range as inherently coherent and requiring no crossover. So the obvious thought was "Let's make an open-baffle full-range loudspeaker and have the best of both worlds" I realise there are some serious challenges with this approach, and it seems rarely employed, but hey, every speaker design has challenges I want to at least try before I give up!
@Josephjcole - no, I haven't tried either of these approaches in practise - as the thread title says, it's my first build of this type.
@Racket Scientist - fantastic link! Just what I was looking for! I think I'm getting a lot closer to my goal now. I like that baffle idea, and I am nearly sure I can make it into something at least remotely attractive. So now it would be just a matter of choosing the right driver for the job...
Of course I'm still open to alternative suggestions.
The reason I insist on crossover-less full range is that my experiences with other audio devices so far confirmed the simple truth - with every component you add, you take something away from the original information in the recording. I'm not talking about distortion, frequency response and such, but rather the emotion, the "soul" of music. I hope you understand what I'm trying to say...So after some thinking and research I arrived at these two concepts: firstly open baffle, which is commonly described as pure and direct, and secondly full range as inherently coherent and requiring no crossover. So the obvious thought was "Let's make an open-baffle full-range loudspeaker and have the best of both worlds"
I realise there are some serious challenges with this approach, and it seems rarely employed, but hey, every speaker design has challenges I want to at least try before I give up! @Josephjcole - no, I haven't tried either of these approaches in practise - as the thread title says, it's my first build of this type.
@Racket Scientist - fantastic link! Just what I was looking for! I think I'm getting a lot closer to my goal now. I like that baffle idea, and I am nearly sure I can make it into something at least remotely attractive. So now it would be just a matter of choosing the right driver for the job...
Of course I'm still open to alternative suggestions.
Like others have suggested, running a puny 8" driver OB without help down below is going to limit how loud you can play. It will run out of excursion pretty quickly. A way out is to use an array of full range drivers. That would keep the excursion per driver low, but then you need some sort of shelving to get a flat response.
Even with a single driver, the loss in bass would have to be equalized. You are loosing bass at 12db/octave from a frequency that is dependent on the size of the driver and the baffle. This means you'll need some sort of EQ, or a filter, which is not too different from a crossover.
Active crossovers, those happening before the power amp, can sound better. Passive crossovers can be just as good if designed properly, but this is the hard part. With active crossovers, you can play to your heart's content until you think it is right. The learning curve is much less steep.
Try MiniDSP or DCX2496. For the ultimate full range OB active crossover, look at NP's Firstwatt B5.
Even with a single driver, the loss in bass would have to be equalized. You are loosing bass at 12db/octave from a frequency that is dependent on the size of the driver and the baffle. This means you'll need some sort of EQ, or a filter, which is not too different from a crossover.
Active crossovers, those happening before the power amp, can sound better. Passive crossovers can be just as good if designed properly, but this is the hard part. With active crossovers, you can play to your heart's content until you think it is right. The learning curve is much less steep.
Try MiniDSP or DCX2496. For the ultimate full range OB active crossover, look at NP's Firstwatt B5.
Issues in speaker design - 2
Scroll down to 'H: Mounting a driver to a baffle' and use the spreadsheet to calculate max SPL from your driver and baffle.
Scroll down to 'H: Mounting a driver to a baffle' and use the spreadsheet to calculate max SPL from your driver and baffle.
I'll give a quick description of what I'm running and very happy with. I use a pair of Wharfedale SFB/3's like described on the site I referenced, but replaced all the drivers (which are shot). I have a pro audio 12" in the bottom (Eminence Alpha 12), an 8" Tang Band 1808 (mounted in a homebuilt wood "adapter" to let it fit in the 10" opening) in the top, and the 3" up firing tweeter is replaced by a piezo "lemon squeezer" tweeter. I run the Tang Band with a Zobel and the piezo directly off the upper speaker with no other passive crossover components. I run through a pro-audio active crossover into 2 amps, with the low end below about 400 Hz going to the 12" and above 400 Hz to the full range/piezo. I also have a pair of pro audio 18" subs (I'm in a band) that I plan to hook up with another amp and cross over to below 100 Hz in the near future. This is all in my rather large basement. So far without the subs I really like the sound.
Based on your requirements, I'd consider trying just a full range (maybe the 6.5 inch Alpair) by itself on a largish baffle (maybe 25" to 30" wide), and anticipate not having much low bass, but having some low end boost by placing them near the wall in your current small room. If you do move to a bigger space, you could then add a separate woofer in another cab (or build a new baffle) that relieves your full rangers of bass duty so the system can go lower and play louder. I decided with mine I really prefer the sound with a Zobel, as they can be strident on axis without it.
Based on your requirements, I'd consider trying just a full range (maybe the 6.5 inch Alpair) by itself on a largish baffle (maybe 25" to 30" wide), and anticipate not having much low bass, but having some low end boost by placing them near the wall in your current small room. If you do move to a bigger space, you could then add a separate woofer in another cab (or build a new baffle) that relieves your full rangers of bass duty so the system can go lower and play louder. I decided with mine I really prefer the sound with a Zobel, as they can be strident on axis without it.
Just a quick comment - using an array opens a whole new can of worms. Not saying the above notes are incorrect, just that you lose some of the advantages of a single driver. If you don't listen too loudly and are in a smallish room, you should be fine with a single driver per side. If you need more, I'd really recommend augmenting the lows (and MAYBE the highs) with another type driver but crossing over away from the midrange as far as possible, rather than adding more full range or mid drivers.
Thanks ra7 - would you be able to explain to me what is the "Dipole path difference" parameter? I understand it has something to do with the baffle size, but how do I calculate it?
A can of worms indeed
This is what I felt intuitively anyway - if I want to build a system around a "simplicity" principle, then I should keep it simple throughout I hope a good single driver will be enough.Would someone be able to suggest/comment on the driver choice? Like I said before, Alpair 10.2 appeals to me, and the price is within my budget, but I may be missing some critical flaw. Or perhaps there are simply better alternatives...?
Last edited:
I'm guessing "as low as possible" is not a good enough answer
Well, let me put it this way:80Hz is absolute minimum requirement
60Hz would be good
50Hz would be fantastic
40Hz I would never look for anything else
20Khz, I guess?... But a bit of a roll-off in upper treble will not really bother me.
I could live with fairly large speakers, I suppose... Let's say max height 150cm / 60", max width 100cm / 40" - although with such a huge baffle I would probably prefer some kind of "winged" arrangement.
My listening room is rectangular 4.70m x 3.10m (approx 10x15ft) and I am pretty much free to arrange it any way I please.
Efficiency is not critical, and I generally listen at moderate volumes - loud enough to give a proper dynamic range to recordings, but not loud enough to wake up my neighbours.
My amp is a Gainclone (LM3875 on Black Gate N caps) and with my current PS it's running at some 40Wpc / 80W peak. Not very well-suited to driving extremely difficult loads (like a 2Ohm electrostatic), but fairly flexible otherwise; apparently, they tend to sound best with high efficiency speakers and simple crossovers. If going for a two-way system I will build two extra channels to power each driver independently.
I believe all of your goals can be achieved, even getting bass down to 40 Hz or maybe even lower. My recommendation would be to marry a Goldwood 18" or Eminence Alpha 15A with a single small full range driver (3" or 4") with an efficiency of 88 - 90 dB/W/m. You could go OB or H frame plus OB. You will need a crossover to get the optimum response. Think about trading off the crossover against overloading a full range driver with bass input and the nasty response that will result.
A higher efficiency 6" or 8" driver will require muiltiple woofers and a bigger system. I recently sized a really nice OB speaker that paired a Fostex FE-206E with two Eminence Alpha 15A woofers using a second order crossover, the SPL response was 98 dB/W/m down to 40 Hz (-6 dB).
A crossover is a requirement. Active crossovers are easy. The passive crossover has to be designed carefully for it to work well. A poorly designed passive crossover can ruin the system's performance. Not using a crossover will definitely create problems that are as bad if not worse then a poorly designed crossover. I believe that the optimum solution includes a crossover, anything else is a compromise.
This is probably the easiest type of speaker system to design and get right the first time.
Martin
A higher efficiency 6" or 8" driver will require muiltiple woofers and a bigger system. I recently sized a really nice OB speaker that paired a Fostex FE-206E with two Eminence Alpha 15A woofers using a second order crossover, the SPL response was 98 dB/W/m down to 40 Hz (-6 dB).
A crossover is a requirement. Active crossovers are easy. The passive crossover has to be designed carefully for it to work well. A poorly designed passive crossover can ruin the system's performance. Not using a crossover will definitely create problems that are as bad if not worse then a poorly designed crossover. I believe that the optimum solution includes a crossover, anything else is a compromise.
This is probably the easiest type of speaker system to design and get right the first time.
Martin
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.