[Kevin P]

So this question just occurred to me. If the baffle is 1.5" wider, do we adjust the other dimensions to maintain the original enclosure volume, or leave them alone?

If we can change the depth (decreasing to just over 14.5" deep would maintain the original 4690 in^3 volume, vs the 16.75 deep of the original plan) that would actually suit my particular setup.

Actually what you need to adjust is the volume seen by the two woofers.   It should be nowhere near 4890 in^3.   It should be about 1.5ft^3 which is about 2592 in^3.  With our current port length that tunes it to around 33Hz.

Anyone (dan, kevin?) comment if either of these would affect the xover/sound, and which route is preferable?

bald

Much of this information is getting repeated and warped in translation.  

What Dan has said is that you can change baffle width by up to 10% with only minor changes in the FR of the speaker.   The speaker was designed around the stock baffle width.   That means we built and measured the frequency response, phase and impedance of the drivers in the original enclosure.   Captured in those measurements are the effects of driver to driver cancelations, baffle diffraction and baffle step loss.   We designed the crossover around these features that are as much a function of the enclosure and it's layout, as it is the parameters of the drivers.    When you change the baffle dimensions or the driver layout you change the baffle diffraction.   This effects the edge diffraction mainly and baffle step to a lesser degree.    Baffle step loss occurs over a wide range gradually so changing the baffle by 10% has negligible effect on baffle step.   It probably has greater effect on edge diffraction characteristics.   How much?   It's not entirely predicatable without very complex mathmatical models and it's much easier just to measure rather than calculate.     The advice that you can change dimensions by up to 10% is just a general rule of thumb that Dan is using based upon his extensive experience.  

The volume of the enclosure only effects the low frequency performance.   The box is tuned via port size & length and when you change the volume of the cabinet from the original design you change port tuning (unless you change the port length to compensate).   If you make the front baffle wider you are effectively increasing the internal volume of the enclosure.   If you don't compensate by decreasing the volume you will change the tuning frequency (downward).   You will once again be deviating from the original design and how much is allowable is a little bit of a guess.    

Does that better explain the situation?

[bald]

Thanks for the detailed reply. I made a mistake, completely forgetting that the mid/tweeter were sealed off on the inside, so my volume was way off. But I guess the principle of the question was the same.

If you don't compensate by decreasing the volume you will change the tuning frequency (downward). You will once again be deviating from the original design and how much is allowable is a little bit of a guess.

I think what you said is what I wanted to hear. I can appreciate this is somewhat of an art, I just want to confirm I'm not making any retarded design mistakes before I set out to make $1500 worth of speakers.

I want to use Al's nice baffles and with that extra inch and a half of width, decrease the depth of the speaker in order to maintain the volume that the extremis sees as the same as the original design. It seems like changing the depth wouldnt have much effect on the things you mention like diffraction/baffle step, since that particular modification doesn't change the front face at all. I guess it would bring the back wall closer to the ports, not sure if that would matter. probably not i guess.

Thanks for the reply, sorry if you feel like you're explaining the same things over and over again, I know the feeling, I do it all day

bald

[RAW]

We have the new plans in the works.
Just adjusting the depth for correct volume yes.
Using the 1.5" wider baffle .75" on each side with all the drivers locations staying the same will have no effect of the xover from what I have been told by Dan.
As well once the .75" wider cabinet has a .75" round over as most of us cabinet builders do to wrap veneer the over all width is not as great.

If nothing a better responce will be had dueto the rounded corner over the sharp corner.

http://murphyblaster.com/content.php?f=cabinets.html

http://murphyblaster.com/images/mbow1_2nd_15.png

Dennis tested these  below same cabinet as above in every way but the below cabinet has a 3/4" round over.

http://murphyblaster.com/images/mbow1_round.gif

Think that kind of explains it in a nut shell.

This is why I wanted to go with a wider cabinet for the round over as well as wraping veneer.


Al
[/img]

[Kevin P]

Thanks for the reply, sorry if you feel like you're explaining the same things over and over again, I know the feeling, I do it all day  

You know it!     That's just part of the process.  

I guess the big thing I'd like to point out is that when you deviate from the design you really need to understand what you are doing.   I know the stock design doesn't fit everyone's needs so we are working on variations.  We will publish them as we get a chance but there are only so many hours in the day and we are cracking on them as fast as possible.  

When we get done there will probably be four different variations of the LCR.   There will be at least two variations of the 2641.   There will be two variations of the 641 and two variations of the 61.    It takes time to work through all of the variables, build, test and make sure we have parts for all of them.   In addition I'm taking orders, answering the phone, answering email, monitoring the forums,  paying bills, ordering parts,  shipping orders, providing tech support, processing returns, developing documentation, doing web development, taking photos, building product and developing new ones.   Whew.... lots to do.  

It becomes impossible to support the products when everyone is building the speaker differently.   From a tech support perspective we need to have a couple designs that fit 90% of the situations and stick with them.   I just have no way of telling people how variation XYZ is going to compare with variation ABC when I've never built, measured nor listened to either.       That is my main concern.   That people are going to make changes and end up with poor results.

[RAW]

I have had a few emails asking what I have listened to in the last while.As far as kits go.
Kind of thought I would drop this on your step.

kit41
kit61
LCR
Kit261
(Apex in the photo and coming)
GR AV1
New GR AV4
Criterion
RAW
HT1
HT2
HT2C
HT3
HT6

Now can I make a comment on one kit.
Better think on that one

Enjoy.

Al