[fillemon]

hello everyone, i'm new here.

i'm not the most experienced builder, but i did a bit of my share.
from what i have heard open baffle is the way to go. i have had an old philips two way paper cones speaker and opened up the back. the sound it gave was magnificent. (but no bass). i build a speaker with a coral flat 8 (br), but no luck either. Now i'm listing to a fostex 167e (ML TL) : which is okee, but no speaker ever gets close to a simple open baffle.

i have a diy tripath amp, and non os dac. (also a diy headphone amp: SS class A)


So now i wanna build a good speaker system open baffle. but i'm not willing to spent a fortune.

i was looking at the rather famous aplha 15 and b200 combination, still i have some questions about it
here i go

1)i wanna play it in a big room: so i need extra bass i suppose: i can use two alpha's per side: would that be possible or would it sound less ?
2)if i want more bass: i can add whings to the baffle ? good idea ? even with two alpha's already in line per side ?
3)would it upgrade the sound if i buy oval saba greencones (and tweeter) in stead of the b200 ? (the saba's have even more sensitivity so that might be a good combination with two alpha's
4)i can use EQ via the computer cause i will use and usb dac, but i will listing to radio also, so preferably it needs to be as flat response as possible

did anyone already experiment with my ideas above ?
or does anyone know a better rig for that money ? (i know putting a ribbon on it wil sound better, or a better woofer but for the money i think it might be a very good system). I will build a EL84 PP triode to power it up.

thank you guys.
within a few months i wanna start building. and maybe never build again 

[giamba76]

I don't know how big is your listening room, but i do the same of you, using 2 Alphas on each side and fullrange similar to B200 (Ciare Hx201). In my final set up i have all my OB driven in active using 2 tubeamp (el 84 ~ 15w for Hx201 / el34l ~ 30w for Alphas15) also connect to Eq/notch filter very useful to permit to have the most flat respon in your room. For to go in passive (i try) you have to do much test, and spend money in caps and coils...so this is my opinion!
I use a baffle of 88cm (with open wings) and high 120cm...and i have very deep and fast bass

[fillemon]

thanks, so i have almost your setup great.

well my room is 28 X 16 X 10 (height) and my next room might be bigger (33*20*15)
So i think i might run out of steam with one alpha.  i don't listing that loud, but it's nice
that bass is there at low volume.
i don't think i will drive it with two tube amps, (maybe a SS for the woofers, and tube for the fullrange)

how deep does the bass goes -3db point ?
why do you use the ciare ? (and not something else ?)
i suppose you run the ciare full range ?
what kind of EQ filter do you have ? (well is a complex one? i suppose you did the adjustement for your room
and not in a "dead" chamber)

thanks again for you information
greetz

[mcgsxr]

I run a system related to what you describe, but different in a few key areas.  Pics in my gallery, link in my signature.

1 - I run a b200.
2 - I run active Xover - Reckhorn
3 - I run an active bass amp, for the 2 12's - one 12 per baffle
4 - my room is large - 25x35x8
5 - bass varies around the room - hard to describe - at the listening chair it is balanced well, but over by the pool table there are areas where the bass is stronger - nodes I assume
6 - I might (ducking here!) recommend the use of a sealed sub in concert with the single 15's per baffle, on a dedicated sub amp.  That will take over under the F3 point of the OB, and will take care of the deep, deep stuff.  Some will argue that OB bass is the only way to fly (and for me it is)

Oh, and welcome to AC and the OB forum!

[giamba76]

how deep does the bass goes -3db point ? In my program i see 83db @20hz - 91db @30hz - 94.5db @40hz - 97db @50hz for freq.resp. absolute spl

why do you use the ciare ? (and not something else ?) because i live in italy and i find it at good price
i suppose you run the ciare full range ? No i cut with elettronic 2way crossover (behringer CX2310) around 150/160hz
what kind of EQ filter do you have ? (well is a complex one? i suppose you did the adjustement for your room
and not in a "dead" chamber) yes i tune the eq for my room complying my ears i use the behringer T1951 tube vintage serie, very easy to use, for bass i set up +5db @30hz with less than 0.5 of Q

thanks again for you information
greetz

See red words......
cheers

[fillemon]

thanks guys,

your systems are not that simple i see.
electronic crossover, active Xover.... biamped...

well i might buy something like that to, (like the berhinger)
the advantage is that you can always tune it if you like, (otherwise there isn't ? or is there ?)

so you split the signal in an electronic crossover between sub and fullranger
then it would be best to flatten the bass as good as possible (like the t1951)

i suppose you don't use an digital crossover (like dec2496) because the quality loss in conversion  ?)

but if you have 2 amps behind the crossover: how do you manipulate the volume or do you do this before the crossover ?

thanks

[mcgsxr]

I use an old analog EQ to help boost the lowest bass, in an effort to flatten the in room response.  I am sure a digital EQ would be better, but I had this lying around, so free was better in my case!

To even the sound between the b200 and the subs, I adjust the sub amp once to a specific volume, and then as the preamp drives the overall volume prior to the Xover, it remains in sync.

So, inital playing with the sub (volume, Xover point, and EQ) was pretty involved, but since settling on the settings, I have not touched it since.

[Bob in St. Louis]

but if you have 2 amps behind the crossover: how do you manipulate the volume or do you do this before the crossover ?

I've got two amps "downstream" of a Behringer DCX2496. Each has it's own volume knob. Works pretty well.

Bob

[ultrachrome]

The dcx2496 is quite popular as a dac/crossover but it is noisy when used with amps that only support unbalanced inputs.  This is especially true with efficient drivers.

I feed it an s/pdif signal through a small transformer into the aes/ebu digital input.  I swapped the balanced output boards with unbalanced using some boards from a guy who's name may be Bruce DiPaola and is, as far as I know, not actively producing these.  However, there is a wealth of info and products focused on smoothing out the warts of this unit.  http://www.dcx2496.fr/en/index_en.php

What about taking your fostex driver and trying it in an open baffle with something like the Eminence Alpha 15's or the Goldwood 18"?

It is possible to do this passively.  Check out the open baffle designs at  http://quarter-wave.com.  A lot of info there that you can use.

Biamping costs more but with a digital crossover and an extra amp you gain a lot of flexibility to try new things.

[fillemon]

thanx guys, i never saw that site for modding the dcx2496, very interesting.

i don't know if i will go balanced, (i'm looking at the sympatico amp from twisted pear audio, but it's getting price then, two of those, an dcx 2496 and mods...) still i looks like sound heaven to me.

well i have run my corals and fostex in open baffle, but they never sounded that good to me. the simple old paper philips did it much and much better. I think the suspension of the fostex and the corals are to weak, (mm it will be more compicated than that, but i didn't like the sound in free air of those drivers).

another thing to worry is: what about a turntable, if i build on a digital crossover i cannot use a turntable. which is a pitty. (i know audi nirvana is all about compromises, but this one might be to big).

well whatever part i'm gonna buy, it needs to be very cheap or good enough to keep all the way.
i suppose that 15" eminence will be good enough to keep all the way. the saba greencones probably will be okee to, and a tweeter i can always add a more expensive one later.

for the woofer: my goal is not to let a woofer run above 80hz. so that most of male voices (and up: like female voices) are for the saba: if i need more juice around 85hz for example i can add 2 saba's per side. i really don't like splitting up frequency's in the delicate human voice range (around 50-8000hz; 50 for very low male voices; 8000hz for the "gingle bell" sound in voices: it is the resonance frequency for the cavity in your ear within your skull, where the sound resonate when somebody knows how to sing) (anyway enough human anatomy, this is a hifi forum  )

what do you think: i would buy the saba mid and tweeter and 1 aphla per side, with a hardware crossover, if that isn't good enough i can move on. putting an extra alpha per side, and then get an dcx2496 (i don't think i will buy a electronic crossover, cause the possibilities of a dcx2496 are so much more then a simple crossover, exept when i need my turntable).

thanx for the replies

[ultrachrome]

The dcx does have analog inputs but running through an ADC doesn't sound all that attractive if you're into vinyl.

That driver will be rolling off well above 80Hz due to baffle dimensions.  You'll need a couple of octaves of low pass to overcome the dipole effect for that driver assuming you keep the baffle narrow.  I don't know what kind of xmax the Saba has but if you crossover at 80, it will be the limiting factor in your SPL.  I don't know how well that will fill a big room.

According to the ABC Dipole spreadsheet max spl of a 8" driver at Fc=80Hz with 1mm of xmax in a 30cm wide baffle will be about 85dB.

Adding a second driver to compensate complicates because you won't likely be that happy with the comb filtering running two 8" drivers at high frequencies.  You'll need to make a 2.5-way crossover.

Do you have a measurement microphone?  How do you plan to design the crossover?

[fillemon]

thanx ultrachrome for you information,


yes i have a measurement microphone (a behringer)

indeed using 2 saba's per side will be a hard task, also the fact that i have two sources will make that the sound will be out of fase.
i need to keep one saba per side,

1)but i can make a wider baffle, 55cm, and put two whings on it (something like 35 cm of 45 in glass : so that makes a baffle of 120-140cm): that might do the trick, but then again, from a 20cm speaker in open baffle asking to do 80hz at loud volume might compromise higher frequencies from that driver.

2)i looked for the ABC Dipole spreadsheet and found a tread of you (i'm gonna read it carefully)
http://www.audiocircle.com/index.php?topic=64370.0

3)i just don't know how i would design the crossover: that is a bridge to far for me. i think it is one of the hardest things you can ever do in building a speaker. So i will need to look at others, luckily a few people have done this before me with a saba. (well from what i think, i'll take a quite steep filter; from 35-80hz the woofer, 80-12000 (or so) the mid, and then the tweeter. (i suppose second order, and the baffle will do the rest, so that i get a 48db filter (well it's a long time ago since i have thought about the filter);

4)indeed: the vinyl could be a problem. maybe if i find some good setting, i could try to make it as hardware version, but probably it will never sound that good.

thanx

[kyrill]

thanx guys, i never saw that site for modding the dcx2496, very interesting.

i don't know if i will go balanced, (i'm looking at the sympatico amp from twisted pear audio, but it's getting price then, two of those, an dcx 2496 and mods...) still i looks like sound heaven to me.

well i have run my corals and fostex in open baffle, but they never sounded that good to me. the simple old paper philips did it much and much better. I think the suspension of the fostex and the corals are to weak, (mm it will be more compicated than that, but i didn't like the sound in free air of those drivers).

another thing to worry is: what about a turntable, if i build on a digital crossover i cannot use a turntable. which is a pitty. (i know audi nirvana is all about compromises, but this one might be to big).

well whatever part i'm gonna buy, it needs to be very cheap or good enough to keep all the way.
i suppose that 15" eminence will be good enough to keep all the way. the saba greencones probably will be okee to, and a tweeter i can always add a more expensive one later.

for the woofer: my goal is not to let a woofer run above 80hz. so that most of male voices (and up: like female voices) are for the saba: if i need more juice around 85hz for example i can add 2 saba's per side. i really don't like splitting up frequency's in the delicate human voice range (around 50-8000hz; 50 for very low male voices; 8000hz for the "gingle bell" sound in voices: it is the resonance frequency for the cavity in your ear within your skull, where the sound resonate when somebody knows how to sing) (anyway enough human anatomy, this is a hifi forum  )

what do you think: i would buy the saba mid and tweeter and 1 aphla per side, with a hardware crossover, if that isn't good enough i can move on. putting an extra alpha per side, and then get an dcx2496 (i don't think i will buy a electronic crossover, cause the possibilities of a dcx2496 are so much more then a simple crossover, exept when i need my turntable).

thanx for the replies

Ok

I tried the Saba as well in OB because of some very positive stories on the net.
I bought the tweeters ( was in the package) but did not use them. they are heavy looking. I really belief modern tweeters will have much more air around them than those heavy little drivers with their little magnets.

But back to the Saba green cone 20cm mid range tweeter with alnico magnets. the sound is superb musical and that's it. No intrinsic details actually no micro details. no real focus. echo and voice are not separated, 3rd voices behind the main singer become one voice albeit a touch richer. Wonderful tone

But if you like transparency and details then this is not the driver for you in very good to best systems.

Then i see, you want to xover at 80 hz... The maximum lowest freq. i got without EQ from the SABA was 180 hz in a baffle of width 16+ inch (42 cm) x length 43,3 ( 110cm)  inch U frame is 6 inches deep, Saba at +/- 6 inches ( 16cm) form the upper edge

making a wider baffle asks for other sacrifices, mostly imaging see http://www.audiocircle.com/index.php?topic=64048.0
making a deeper U frame asks for higher resonance 200-300hz and up)

[fillemon]

thanks kyrill,

i have been reading more, it seems that definitly need a "trapezium" baffle, to compensate for beaming.
i don't mind that, i even like the look of it, so if it is functional and good looking, even better.

okee, i see it, no matter what mid-driver i take, it will not be possible to let it perform from 80hz
it will be more around 250-500, so the woofers will have to perform this human voice area.

i'm gonna look around, but for 90 euro i can buy the mid and tweeter saba greencones, not that much money
for trying. i do like air (i like ESL) but i'll see what happens.

i have seen that on this board there is a lot of open baffle going on, i have been reading post of rudolf, seem like he is
very capable. nice to see so many people who are doing it OB, that way i can try to avoid the pitfalls of this design.

thanx people.

ps: i have looked at MJK projects with the goldwood and the fostex/jordan; but he doesn't narrow his baffle two approx two times the driver size ? so it will be a bit beaming i suppose ? (his design is well documented and might be a good start for a beginner like me)
ps2: i have seen kyrill that you have found a decent midrange driver: i'm folowing you topic to see how good it performs.

thanx guys

[Rudolf]

i have been reading more, it seems that definitly need a "trapezium" baffle, to compensate for beaming.
i don't mind that, i even like the look of it, so if it is functional and good looking, even better.

Building dipoles is always a matter of compromises, especially compared to the traditional CB or BR concepts. With my treatise on baffle width I just wanted to show where the compromises WRT wide baffles lie.
As you already have noticed, my concept of matched baffle width demands more than two drivers to cover the full range. Typically one driver would only span one order of magnitude, like 30-300, 300-3000, 3000-20 kHz. And that is already stretching the concept. So there is no way to cover the complete range of the human voice with one driver if you follow my thinking.

okee, i see it, no matter what mid-driver i take, it will not be possible to let it perform from 80hz
it will be more around 250-500, so the woofers will have to perform this human voice area.

Crossing over in the mid of the human voice is possible without any sacrifices IMHO, but you really need to get the crossover right. And I doubt that can be done without measurement capabilities, if you don´t follow a proven design. It is less difficult below 500 Hz, but will be a problem at 1 kHz and higher.

ps: i have looked at MJK projects with the goldwood and the fostex/jordan; but he doesn't narrow his baffle two approx two times the driver size ? so it will be a bit beaming i suppose ? (his design is well documented and might be a good start for a beginner like me)

My concept asks for mandatory EQ at the bottom end of each drivers range. This will crush some efficiency and could end in more complexity of the crossover. In fact my concept really asks for active solutions instead of passive filters.
MJK´s designs satisfy the much expressed wishes for less complex and easy-to-build solutions. And as I believe they do exceptionally well in that regard! They need a wide baffle to fight the dipole loss at the low end of the Fullrange. As a consequence MJK has to concentrate on the on-axis-response. But his H frame with OB designs are an excellent place to start from.

WRT "beaming": Actually the concept of "baffle width approx two times the driver size" will "beam" more than a wide baffle. But while a wide baffle might "beam" - depending on frequency - in different directions and with different "beam width", the direction and width of the small baffle "beam" should be constant with frequency.

BTW: I put the "beam" between quotation marks, because beaming reminds me of lighthouses and torch lights. In comparison "beaming" loudspeakers will just have some variation in their radiation pattern, but they don´t have you "standing in the dark", if you are off-axis. What you see in those polar diagrams looks much more dramatic than what your ear will notice.

[panomaniac]

It is less difficult below 500 Hz, but will be a problem at 1 kHz and higher.

Oh, you ain't kiddin'!  My present rig crosses right at 1KHz and it is very touchy.  Any little crossover change is so easy to hear.  Drop the x-over point by 2 octaves and it's much less of a problem.

..reminds me of lighthouses and torch lights. In comparison "beaming" loudspeakers will just have some variation in their radiation pattern...

That's because the wavelengths of light are so short.

[MJK]

ps: i have looked at MJK projects with the goldwood and the fostex/jordan; but he doesn't narrow his baffle two approx two times the driver size ? so it will be a bit beaming i suppose ? (his design is well documented and might be a good start for a beginner like me)

My concept asks for mandatory EQ at the bottom end of each drivers range. This will crush some efficiency and could end in more complexity of the crossover. In fact my concept really asks for active solutions instead of passive filters.
MJK´s designs satisfy the much expressed wishes for less complex and easy-to-build solutions. And as I believe they do exceptionally well in that regard! They need a wide baffle to fight the dipole loss at the low end of the Fullrange. As a consequence MJK has to concentrate on the on-axis-response. But his H frame with OB designs are an excellent place to start from.

I am not sure I understand the continued emphasis on the narrow baffle (approx two times the driver size) concept. If you run my OB / H Frame model on axis and 30 degrees off axis the only significant change in the response is caused by the Jordan driver becoming directional at higher frequencies. You do not see any signficant impact from the baffle width. I would think you would want the non bass driver(s) running above the OB generated hump, in fact use the hump as an aid in the crossover design.

As far as bass drivers, the ultimate would be infinite baffle. So I would say a wider baffle would be better for the bass drivers. Obviously size can become a WAF issue so go with the maximum tolerable.

In my opinion, the desire to limit the baffle width to twice the driver diameter is not a clear advantage and could be limiting the flexibility of integrating drivers and the ease of doing the OB crossover design. My recommendation would be not to rigidly follow this rule of thumb for OB designs. Wider is probably better.

Martin

[ultrachrome]

I would think you would want the non bass driver(s) running above the OB generated hump, in fact use the hump as an aid in the crossover design.

So a wider midrange baffle pushes its dipole peak lower.  Are you suggesting using the hump to extend its LF extension?

I'm still struggling to get my arms around this but this leads me to believe I'd want to size the woofer section and mid range section accordingly so their respective peaks are spaced apart?

Can you talk a little more about how the hump aids the midrange or point me to a resource that does?]

Thanks.

[MJK]

So a wider midrange baffle pushes its dipole peak lower.  Are you suggesting using the hump to extend its LF extension?

That is exactly what I am saying and how I have done all of my crossovers between the full range driver and the woofer. If the dipole hump is centered at 200 Hz, you can design your full or mid range driver's electrical crossover at 300 to 400 Hz and use the hump to produce an acoustic crossover that is lower shifted towards 200 Hz. This means smaller and less expensive passive crossover components. Look at the passive crossover in my Fostex / Alpha 15A OB article to see the dipole hump accounted for in both of the 2nd order filters.

I want the baffle wide enough so that the full range or midrange and tweeter operate above the dipole hump, I do not believe the diffraction ripple is very significant if you offset the driver a little from centered on the baffle. The potential for a couple of dB of ripple is not as significant as floor bound ripple, other room effects, or the basic uneven response produced by the driver's cone.  I do not believe that beaming, directional response, and ripple are necessarily driven strictly by baffle width. I have to question if the discussion is focusing too much on a smaller problem in the overall scheme of OB design issues.

[Rudolf]

Martin,
I am sure this discussion IS focusing too much on a smaller problem in the overall scheme of OB design issues. And it has emerged as my reaction to people fussing too much about moving drivers one inch to get a flatter on-axis response diagram with EDGE (a microscopic problem) without looking for what happens off axis. Whether you find the following either quite irrelevant or making things much too complicated is completely up to you - I just want you to understand were I´m going:

These are on-axis measurements of a small 3" FR driver on an infinite baffle (unendlich) and on baffles of different width:



There are two situations with a smooth response:
First case: A 40 cm wide baffle with the driver mounted at an asymmetrical position.
Second case: A baffle of twice the cone width (11.5 cm). Admittedly the second case driver needs some EQ below 1 kHz to be as linear as the first case.
In contrary to you I see some signficant impact from the baffle width when comparing the different baffle measurements.

Next are-off axis simulations for the same driver on the 11.5 cm wide baffle (which are identical for left and right)



and for the first case (different for left and right)



The diagrams speak for themselves and need not to be commented. I have come to the conclusion that the difference is significant at least for me. Generally speaking I´m desiging left of the dipole peak (blue area) nowadays while you are designing mainly above the OB generated hump (red area) - at least for the FR driver:



You are perfectly right that my approach will "be limiting the flexibility of integrating drivers and the ease of doing the OB crossover design". And people should understand that your approach will give them best value and ease of construction while I am surely on a path of diminishing return.

Thank you for helping me to make that clearer. 

Rudolf