Oooh, Event Horizon. One of the most evil films ever made (rather good though. 
)
I'm not Norman, but baffle step marks a transition from 2pi to 4pi radiation space. Basically, it's to do with wavelength and baffle width. Keeping it as simple as possible, when wavelengths are shorter than the baffle width, they are directed forward, at the listener (2pi radiation space). When they become longer than the baffle width, the baffle no longer supports them, and the speaker, below this frequency, transitions to ~omnidirectional behaviour (4pi radiation space). What this means in practice is that the lower frequencies seem quieter than those above the step-point because they are dispersed around the room rather than being directed at you.
One question -if you like your JBLs, why are you wanting to change them? Don't get me wrong, I'm not trying to discourage you (quite the reverse), just curious.
)I'm not Norman, but baffle step marks a transition from 2pi to 4pi radiation space. Basically, it's to do with wavelength and baffle width. Keeping it as simple as possible, when wavelengths are shorter than the baffle width, they are directed forward, at the listener (2pi radiation space). When they become longer than the baffle width, the baffle no longer supports them, and the speaker, below this frequency, transitions to ~omnidirectional behaviour (4pi radiation space). What this means in practice is that the lower frequencies seem quieter than those above the step-point because they are dispersed around the room rather than being directed at you.
One question -if you like your JBLs, why are you wanting to change them? Don't get me wrong, I'm not trying to discourage you (quite the reverse), just curious.
Oooh, Event Horizon. One of the most evil films ever made (rather good though.
I'm not Norman, but baffle step marks a transition from 2pi to 4pi radiation space. Basically, it's to do with wavelength and baffle width. Keeping it as simple as possible, when wavelengths are shorter than the baffle width, they are directed forward, at the listener (2pi radiation space). When they become longer than the baffle width, the baffle no longer supports them, and the speaker, below this frequency, transitions to ~omnidirectional behaviour (4pi radiation space). What this means in practice is that the lower frequencies seem quieter than those above the step-point because they are dispersed around the room rather than being directed at you.
One question -if you like your JBLs, why are you wanting to change them? Don't get me wrong, I'm not trying to discourage you (quite the reverse), just curious.
I want to build something Scott. I would like a really nice pair of monitors.
Start here -- links to other pages & other sites with additional information:
Baffle Diffraction Step
dave
Baffle Diffraction Step
dave
excuse the intrusion and rant, but the word "monitors" is so highly overused and abused as to be almost meaningless
and don't cite "studio grade" monitors, as they can range from as horrible as the Yamaha NS10 to as bloated and impractical for many domestic situations as much larger JBL "control" monitors than your 4312s
the real question should be, that aside from wanting to build (at least one - I dare ya
) something, do you have any particularly special application requirements for this potential project, or will it be for "occasional casual listening - you know, sometimes I just wanna kick back and enjoy the music"? If the latter, don't be surprised if they get used a lot more than occasionally - the Alpair 7 is that good.
to be honest, I've not heard this specific device, and was only half-heartedly ranting about the term "monitor" itself, which has been so diluted by widespread over / mis-use as to mean nothing
I will say that of the half a dozen or so domestic JBL systems I've heard over my 45 year "career" in this hobby none have impressed me with a relaxed musicality - (blame it on exposure to mostly "British" or "East Coast US" school of speaker flavoring, during my formative years starting in the mid 60's)
No doubt there are many far more experienced professional musicians and studio mixing engineers who would have their own favorite brands and models of playback monitors - which they might value for quite different reasons at work than for any recreational listening that they undertake at home.
Now, back to the topic of the Alpair 7 ; for a home listening system with moderate listening level requirements ( i.e. not a dance party PA at which the 4312 would probably excel), this is one great candidate of a wide-band driver for which many DIYers have already designed some great sounding enclosures.
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I'd go for it, just keep the db volume low, probably lower db than your magnepans and without the intoxicating large wave launch and dipole wall bounce. I like wide baffle speakers so I don't have to boost bass as much (less excursion, especially for small drivers).
I'm curious which would have more detail and using what songs (mmg vs dual alpair 7) ........... Thats what most of us chat about here.
I've a pair of alpair 12's on the way because I want to know if 2 bamboo smaller drivers are better to me than a 1 larger alloy driver. That's why most of us end up with piles of this stuff. We have to build it then compare it to what we have. Yes we can read opinions, but we are all different
I know that 4 of my 4" (focused array) was better than 2 (just taking into account distortion, etc) given the MASSIVE constraint on 1 distance away and 1 distance up and down and basically 1 distance left and right and you ignored a slight chesty resonance (2' cube open backed box with foam).
There are many many monitors on the market. They usually stress higher spls for close listening distances (3-4'). A dynaudio monitor (a few different models even) sounds different from jbl monitors. Every speaker sounds different. The far field response is what you hear 10-15' away sitting on your couch, totally different than what you hear at 3'.
But there are people who swear by monitors.
So, your opinion in your room. Better is up to you and your values, experience, music, volume level, acoustics, etc. And what you thought was best may be junk to you in a couple of years.
Norman
I'm curious which would have more detail and using what songs (mmg vs dual alpair 7) ........... Thats what most of us chat about here.
I've a pair of alpair 12's on the way because I want to know if 2 bamboo smaller drivers are better to me than a 1 larger alloy driver. That's why most of us end up with piles of this stuff. We have to build it then compare it to what we have. Yes we can read opinions, but we are all different
I know that 4 of my 4" (focused array) was better than 2 (just taking into account distortion, etc) given the MASSIVE constraint on 1 distance away and 1 distance up and down and basically 1 distance left and right and you ignored a slight chesty resonance (2' cube open backed box with foam).
There are many many monitors on the market. They usually stress higher spls for close listening distances (3-4'). A dynaudio monitor (a few different models even) sounds different from jbl monitors. Every speaker sounds different. The far field response is what you hear 10-15' away sitting on your couch, totally different than what you hear at 3'.
But there are people who swear by monitors.
So, your opinion in your room. Better is up to you and your values, experience, music, volume level, acoustics, etc. And what you thought was best may be junk to you in a couple of years.
Norman
Do keep in mind that if you use the A12 as an exemplar of an alloy driver all other alloy drivers (except the A7 & upcoming A10, maybe the CHR-Mk2) will likely be found wanting
Also don't rush to judgement... they take longer than Fostex to break-in (and follow the guidlines on Mark's forum for initial break-in)
dave
Hi Apt,
From my memory, similar low end and running to +20-kHz.
Actually........, thinking about these two double chamber designs, it would be really interesting to compare them in listening rooms. Hope some Diyers will try this out. I'll try to make some time to do this also but I got press on with more driver development and production, tonnes of work still to do.
Ummmmmmph..... could be very interesting.
Cheers
Mark.
From my memory, similar low end and running to +20-kHz.
Actually........, thinking about these two double chamber designs, it would be really interesting to compare them in listening rooms. Hope some Diyers will try this out. I'll try to make some time to do this also but I got press on with more driver development and production, tonnes of work still to do.
Ummmmmmph..... could be very interesting.
Cheers
Mark.
Hi Gazzzzzz,
I think you mean driver spacing and any combing issue? Unless you're listening from a few Cm distance, you're not going to notice any difference.
Thx
Mark.
Combing was something i used to worry about with 2 drivers... purely from a theoretical standpoint.
Combing from 2 drivers is something that looks terrible on a FR measurement (usually done near-field), but Floyd Toole has shown in his last book that because the ear/brain always expects combing the result is no near as bad as the measures would make it out to be.
Then last summer Bob brought by a set of EL70x2 BRs (and fairly widely spaced at that) and the combing was not an issue. Since then we have also made a 2xFF85 as a further experiment. They work fine too.
If one really wanted to have just 1 driver front-firing, and wanted to move away from a monitor, the 2nd driver could be put on the top or the side, or the whole thing could be rotated 90 degrees, with one on the front and one on the back (ie the sides are in the current plans). We have had good results from all 3 of these in the right room with the right placement.
dave
Combing from 2 drivers is something that looks terrible on a FR measurement (usually done near-field), but Floyd Toole has shown in his last book that because the ear/brain always expects combing the result is no near as bad as the measures would make it out to be.
Then last summer Bob brought by a set of EL70x2 BRs (and fairly widely spaced at that) and the combing was not an issue. Since then we have also made a 2xFF85 as a further experiment. They work fine too.
If one really wanted to have just 1 driver front-firing, and wanted to move away from a monitor, the 2nd driver could be put on the top or the side, or the whole thing could be rotated 90 degrees, with one on the front and one on the back (ie the sides are in the current plans). We have had good results from all 3 of these in the right room with the right placement.
dave
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Hi Guys,
An up-dated version of the Alpair 7 Twin Studio plan can now be down-loaded from Post No.20 on this thread:
http://www.diyaudio.com/forums/markaudio/169016-alpair-7-twin-driver-studio-monitor-plan-2.html
Please ignore and/or revise all previous sketch drawn plans in favour of this download.
Thanks
Mark.
An up-dated version of the Alpair 7 Twin Studio plan can now be down-loaded from Post No.20 on this thread:
http://www.diyaudio.com/forums/markaudio/169016-alpair-7-twin-driver-studio-monitor-plan-2.html
Please ignore and/or revise all previous sketch drawn plans in favour of this download.
Thanks
Mark.
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