Burnett,
Your PMC clone's freq. response curve looks unbalanced, how do you find the sound reproduction? Is it acceptable to you?
I was think of building a similar clone and decided not to proceed because there were to many factors to juggle to get the sound right, e.g. cabinet size, cab. construction, inside foam lining, etc. too much time involve in get the sound right, unless you can model the cabinet size, and foam lining using Martin's Mathlabs maths sheet. Even then you must know what you are doing.
Your PMC clone's freq. response curve looks unbalanced, how do you find the sound reproduction? Is it acceptable to you?
I was think of building a similar clone and decided not to proceed because there were to many factors to juggle to get the sound right, e.g. cabinet size, cab. construction, inside foam lining, etc. too much time involve in get the sound right, unless you can model the cabinet size, and foam lining using Martin's Mathlabs maths sheet. Even then you must know what you are doing.
Well, there is a 15dB drop between 60 & 80 Hz. If that is due to the room, and could easily be the case, then fine. I'm not sure how you can measure anything or test speakers in a room that is less than perfect.
Ideally you'd want the curb to be within about 3dB from 20 to 20K but that must incredibly difficult to achieve.
If the drop you have below 80Hz is not due to the room then maybe it could be addressed by a redesign of the box and/or a tuned port / transmission line.
I can't remember if these have a transmission line or not, actually. Do they? I used to own them, i should know, sorry.
Ideally you'd want the curb to be within about 3dB from 20 to 20K but that must incredibly difficult to achieve.
If the drop you have below 80Hz is not due to the room then maybe it could be addressed by a redesign of the box and/or a tuned port / transmission line.
I can't remember if these have a transmission line or not, actually. Do they? I used to own them, i should know, sorry.
@RickDangerous: That's quite a bold statement. If you have a perfect room (what is that anyway?), then fine. I do and won't have one.
Pardon my ignorance, but have you ever built or measured speakers? 20hz to 20khz +-3db in a small 2way-speaker is utopious just regarding physics.
My measurements where done in 1.5m height and 1m between speaker and mic.
And if you had had a look at the measurements from "production partner" which I posted, then you would have seen that the original and my clone behave nearly the same in the way the midbass works.
And yes, as all speakers PMC builds it has a transmission line.
Just my 2 cents.
Pardon my ignorance, but have you ever built or measured speakers? 20hz to 20khz +-3db in a small 2way-speaker is utopious just regarding physics.
My measurements where done in 1.5m height and 1m between speaker and mic.
And if you had had a look at the measurements from "production partner" which I posted, then you would have seen that the original and my clone behave nearly the same in the way the midbass works.
And yes, as all speakers PMC builds it has a transmission line.
Just my 2 cents.
How on earth can you expect any sort of rational result without firstly testing the specific behaviour of the drivers in question before deciding on the box design - it's like you're designing/building a car with only an approximate engine size or gearbox design - you're going about this backwards and even the best speaker's published specs are usually very wide tolerances, sometimes extremely optimistic indeed.
Choose the drivers, get them measured, then start your box design that does include the passive crossover - it's all one integrated system and a dsp can't correct gross errors in speaker design, or lack of it.
Choose the drivers, get them measured, then start your box design that does include the passive crossover - it's all one integrated system and a dsp can't correct gross errors in speaker design, or lack of it.
Jameshillj mentions driver tolerances, and indeed, independent measurements of the tweeter show deviations from the frequency response published in the datasheet. I didn't notice that yesterday. Attached is an updated version of the crossover with minor changes. The design should be more balanced now.
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