I believe that the drivers are still the Seas discussed earlier. I have seen no mention of any changes in this approach.
Midrange driver enclosure????
One thing that really needs some discussion is the type of mid enclosure and methods to reduce the backwave. Besides the crossover I think this has the largest bearing on the final sound and is one of the most neglected areas in 3-way designs.
So often a small sealed enclosure is used constructed from pipe. I've tried this in the past and certainly introduces problems and backwave issues. I remember on two occasions chasing an edge in the sound when tweaking the crossover and turned out to be the backwave and both were solved by changing to an OB type mid enclosure but that can only be done if the driver and room are suitable. On both occasions they were Vifa P series drivers which are noted for their smooth behaviour. The amount of energy that comes out of the back of the driver when you remove the back panel is quite large and difficult to be controlled in a very small enclosure.
The crossover to the mid would roughly be 2-3 octaves above the Fs of the MCA15RCY so in theory would be operating very little in it's piston range. The choices are:
Sealed
Vented
TL
Aperiodic
OB
Shape of enclosure and use of non parallel walls, angled rear panel etc would help as well as maybe in a dimishing taper ala B&W.
Advantages of various enclosure types on reflections, excursion etc.
I think this needs some good discussion and thoughts from those who have had success in controlling mids in their enclosure as is a very important part of the sonics of this design and ultimately it's success.
One thing that really needs some discussion is the type of mid enclosure and methods to reduce the backwave. Besides the crossover I think this has the largest bearing on the final sound and is one of the most neglected areas in 3-way designs.
So often a small sealed enclosure is used constructed from pipe. I've tried this in the past and certainly introduces problems and backwave issues. I remember on two occasions chasing an edge in the sound when tweaking the crossover and turned out to be the backwave and both were solved by changing to an OB type mid enclosure but that can only be done if the driver and room are suitable. On both occasions they were Vifa P series drivers which are noted for their smooth behaviour. The amount of energy that comes out of the back of the driver when you remove the back panel is quite large and difficult to be controlled in a very small enclosure.
The crossover to the mid would roughly be 2-3 octaves above the Fs of the MCA15RCY so in theory would be operating very little in it's piston range. The choices are:
Sealed
Vented
TL
Aperiodic
OB
Shape of enclosure and use of non parallel walls, angled rear panel etc would help as well as maybe in a dimishing taper ala B&W.
Advantages of various enclosure types on reflections, excursion etc.
I think this needs some good discussion and thoughts from those who have had success in controlling mids in their enclosure as is a very important part of the sonics of this design and ultimately it's success.
Absolutely
The other thing that needs to be considered is how it affects the rest of the box construction, if it is to be a clasic 3way type enclosure... Separate woofer and Mid/tweeter cabinets makes this much easier, but has it's own problems. Unfortunately I'm not yet to the point where I can comment on the success side of things... I have opted for very boring boxes, the only thing I did was to make the internal dimentions all prime numbers, Interestingly they turned out to be a (not the) golden ratio... This however was intended mostly to deal with standing waves.
One approach to take (provided it doesn't result in an extreme enclosure) is to make the depth of the enclosure the longest dimention. I like the idea of a tapered enclosure, but construction seems a bit scary... perhaps a normal shaped box with an opern cell foam block filling it, with the centre cut out going down to a taper?? although that might be harder than just constructing the box that way
Tony.
Well if we used plastic sewer pipe or cardboard tube it could extend all the way through the box and do it TL style, but to some extent doesn't the midrange enclosure depend on the XO slope??
Even with a XO 2 octaves above Fs if we use a first ordet then there will be some pistonic movement.
I mention this only to put first order crossovers in perspective.
Have to say I have only built sealed and OB midrange and when building sealed I often make the mid box too big, robbing the bass driver of volume.
Perhaps the easiest option would be to find a ready made plastic hemisphere of the correct cubic capacity and just use that, such as this 3liter cup from Visaton, which we fill with an appropriate stuffing
Midrange Enclosure 3 Litre - Soundlabs Group
Even with a XO 2 octaves above Fs if we use a first ordet then there will be some pistonic movement.
I mention this only to put first order crossovers in perspective.
Have to say I have only built sealed and OB midrange and when building sealed I often make the mid box too big, robbing the bass driver of volume.
Perhaps the easiest option would be to find a ready made plastic hemisphere of the correct cubic capacity and just use that, such as this 3liter cup from Visaton, which we fill with an appropriate stuffing
Midrange Enclosure 3 Litre - Soundlabs Group
Just throwing this out..
Has a simple BR or sealed cab for bass drivers cabs & MCA15RCY ran on super small & narrow baffle & an easliy avalible mono tweeter , with lets say XO @ 1k & 6k been thought of..?. Reason I say this is that the MCA15 RCY is one of the most detalied & well behaved OB mid drivers I have heard. Actually the best to be honest. It has no percieved wierdness or peaks that drive me up a wall. I have ran these in stock XO'ed L65A' w/ JBL 122A-MCA15 RCY ran open on top front baffle edge & JBL 077 for over a year without changes. I would amagine something simple but extremely nice looking & sounding could be done. Very compact due to non dipole bass & 1k to 6k or so XO. Would be a outstanding 89.5 system IMO. Seams the bass driver would be the issue to get a good one up to 1k.I don't buy into not going up to 1k range for XO anymore. Any good soft dome tweeter of know goodness of 6k up seems like something easy enough to get going.I could be dead wrong on all this except the quality of the sonics of the little SEAS mid in OB.
Joe
Has a simple BR or sealed cab for bass drivers cabs & MCA15RCY ran on super small & narrow baffle & an easliy avalible mono tweeter , with lets say XO @ 1k & 6k been thought of..?. Reason I say this is that the MCA15 RCY is one of the most detalied & well behaved OB mid drivers I have heard. Actually the best to be honest. It has no percieved wierdness or peaks that drive me up a wall. I have ran these in stock XO'ed L65A' w/ JBL 122A-MCA15 RCY ran open on top front baffle edge & JBL 077 for over a year without changes. I would amagine something simple but extremely nice looking & sounding could be done. Very compact due to non dipole bass & 1k to 6k or so XO. Would be a outstanding 89.5 system IMO. Seams the bass driver would be the issue to get a good one up to 1k.I don't buy into not going up to 1k range for XO anymore. Any good soft dome tweeter of know goodness of 6k up seems like something easy enough to get going.I could be dead wrong on all this except the quality of the sonics of the little SEAS mid in OB.
Joe
While I would fer to push the MCA15 to 6kHz using it in OB is a one option. This would also mena that a rear facing tweeter might need to be used.
Also putting the mid in an OB means that the box for the woofer gets a little smaller (actually quite a bit smaller) which might eliminate the TL option for the woofer. If we make a TL box like shown in Post 4 here 8" Transmissio Line Sub - Home Theater Systems - Electronics and Forum - HomeTheaterShack and stick an OB mid and tweeter combo on top however it might work something like Linkwitz's Orion or more like GR Reseach's VR1 or the EXmotion (Strassacker: Lautsprecher - Boxen - Selbstbau), or maybe like Troels's Acapella (Acapella SEasThe non-).
Above 2K you start to get beaming, thus my preference to XO to a good tweeter at lower freq.
Yep... I should have mentioned that my thoughts were based on a 2nd order throughout and is probably the crossover that would end up being used. You are right with your comment on 1st order.
How did it go with power handling in OB? I only ask as I have tried a PL11MH in OB and reached it's limits rapidly due to the small excursion capabilities. Of course it had a smaller Sd and lower SPL than the MCA15RCY.
I use 20w PP mono's on them now & all is fine, far from optimized, but sound excellent. 2nd order on the mid is what I see on schemetic from JBL. Someone else did a DIY effort that was well reguarded @ DIY show & think I have info on it somewhere useing the MCA15 RCY. Might be intresting to get some ideas. The poor mans strad had this mid I think..? Just seems this mid has very little problems & could be optimized to sound stellar.
Joe
Joe
I don't think dying but maybe having a breather I've been thinking about doing some modelling with akabak! But I've also been thinking I should do my own speaker first so I can see how accurate the modelling actually is. It will model baffle geometry as well as the freq response characteristics based on the driver geometry! Somewhat more advanced than the usual sims I do
Tony.
I've been thinking about doing some modelling with akabak! But I've also been thinking I should do my own speaker first so I can see how accurate the modelling actually is. It will model baffle geometry as well as the freq response characteristics based on the driver geometry! Somewhat more advanced than the usual sims I do Tony.
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