Hello everyone!
I am designing some small (2.5 litre) speakers and i was thinking of using the Dayton Audio nd91-8 3.5 inch woofer in isobaric face to face configuration (i get really low base in a small driver and I can pump them louder). One of the driver motors would be pointing down and be physically outside the speaker. I wanted to know until what crossover point would be ok to crossover to a tweeter/mid tweeter in this isobaric configuration.
From the measurements it seams that they are pretty ominidirectional until 2000 HZ. I was thinking about crossing over somewhere between 1200 to 1800 hz to a controlled directivity tweeter (mid tweeter). Is this possible with a back facing driver? Any disadvantages to sound production pointing the speaker down and facing the wrong direction? Also, any good tweeter recommendations that are good off axis? Will the isobaric face to face configuration be detrimental to sound quality in the frequency range used?
My idea is to see if i can get lower in a 2.4 litre box and better sound than by using the L12re coaxial Seas drivers. I will actually build the seas version as well to have something to compare them to.
Any thoughts would be greatly apreaciated.
I am designing some small (2.5 litre) speakers and i was thinking of using the Dayton Audio nd91-8 3.5 inch woofer in isobaric face to face configuration (i get really low base in a small driver and I can pump them louder). One of the driver motors would be pointing down and be physically outside the speaker. I wanted to know until what crossover point would be ok to crossover to a tweeter/mid tweeter in this isobaric configuration.
From the measurements it seams that they are pretty ominidirectional until 2000 HZ. I was thinking about crossing over somewhere between 1200 to 1800 hz to a controlled directivity tweeter (mid tweeter). Is this possible with a back facing driver? Any disadvantages to sound production pointing the speaker down and facing the wrong direction? Also, any good tweeter recommendations that are good off axis? Will the isobaric face to face configuration be detrimental to sound quality in the frequency range used?
My idea is to see if i can get lower in a 2.4 litre box and better sound than by using the L12re coaxial Seas drivers. I will actually build the seas version as well to have something to compare them to.
Any thoughts would be greatly apreaciated.
Isobaric cuts the Vas in half so you can make a smaller enclosure for a given driver and alignment, but you're not changing the displacement so you can't actually pump it louder. But the ND91 was designed for small enclosure from the start so around 2.5L works great for a single driver if that's what you have after subtracting the port volume etc.
If you are trying to tune the ND91 isobaric much lower "simulating" a Vas close to 5L, sure it looks like you can make it go lower - but check the port requirements, that's usually where plans like this hit the wall. And you're probably getting pretty far below Fs, which usually isn't great for good bass.
Running a down firing, rear faced, isobaric ND91 up to tweeter frequencies sounds like trouble if you care about sound quality. If you want to experiment with isobaric, have fun, but I'd cross it several octaves lower and pair it with a small wide band on top like the Aura NSW2.
Needless to say, there are tonnes of great small speaker designs out there if you want to build something safe. If this is for fun and experimenting, try/fail/rinse/repeat is part of the attraction. It's been a while since you asked the question - where did you get to? What's the goals and priorities, and given limitation?
If you are trying to tune the ND91 isobaric much lower "simulating" a Vas close to 5L, sure it looks like you can make it go lower - but check the port requirements, that's usually where plans like this hit the wall. And you're probably getting pretty far below Fs, which usually isn't great for good bass.
Running a down firing, rear faced, isobaric ND91 up to tweeter frequencies sounds like trouble if you care about sound quality. If you want to experiment with isobaric, have fun, but I'd cross it several octaves lower and pair it with a small wide band on top like the Aura NSW2.
Needless to say, there are tonnes of great small speaker designs out there if you want to build something safe. If this is for fun and experimenting, try/fail/rinse/repeat is part of the attraction. It's been a while since you asked the question - where did you get to? What's the goals and priorities, and given limitation?
Isobaric sounds impressive as marketing jargon but in praxis it doesn't have much value (any more).
These woofers already are designed to be put in a tiny closed enclosure. If the box is too small for a flat response, use a DSP to correct and extend the amplitude respons. I would use both woofers in an ordinary configuration (not isobaric). That will work in 2.5 L and have about the same SPL as the single isobaric pair in a vented box.
A vented box will not be possible to build because the port will not fit.
A vented box will not be possible to build because the port will not fit.
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