[Paragon]

Quote:

Originally Posted by Zenja /img/forum/go_quote.gif From playing around with WinISD in the last few days, it seems that you can go much, much lower with a ported box. It depends on the natural resonance frequency of the drivers though. I tried modeling a box for some car speakers I just got, and with a closed box they steadily drop past 100 and they're at -3db by like 70Hz. Using a ported design, I could get the response graph to stay almost flat until about 45Hz. If you try to go too much lower than the resonant frequency though, it falls apart.

Interesting. I would have thought a sealed would have flatter response.. oh well.

 

[nightfire]

Hmm. Ok I must be missing something.

It's my understanding that any driver can reach any low frequency down to 0 hz (straight DC). The question is how much sound pressure can it produce accurately at that frequency... no?

The "drivers" in ER4s can reach 20hz, accurately, no problem.. and they're microscopic. But then, they're creating a very tiny amount of sound energy.

I'm not using this sub to fill a room with bass; it'll be less than a few feet away. I think 2 6" speakers should be sufficient...

In any case I'll be able to work on it this weekend, hopefully.

 

[randytsuch]

Quote:

Originally Posted by nightfire /img/forum/go_quote.gif Hmm. Ok I must be missing something. It's my understanding that any driver can reach any low frequency down to 0 hz (straight DC). The question is how much sound pressure can it produce accurately at that frequency... no? The "drivers" in ER4s can reach 20hz, accurately, no problem.. and they're microscopic. But then, they're creating a very tiny amount of sound energy. I'm not using this sub to fill a room with bass; it'll be less than a few feet away. I think 2 6" speakers should be sufficient... In any case I'll be able to work on it this weekend, hopefully.

I don't think this is the case, drivers have a roll off frequency, for both the low and high ends. From my understanding, you can influence the rolloff frequency, and how sharply it rolls off by the type/size of enclosure.

I am not sure how IEM's work, but it must have something to do with creating a seal inside the ear canel. If you don't get a good seal, you don't get the low end.

Randy

 

[nightfire]

Quote:

Originally Posted by randytsuch /img/forum/go_quote.gif I don't think this is the case, drivers have a roll off frequency, for both the low and high ends. From my understanding, you can influence the rolloff frequency, and how sharply it rolls off by the type/size of enclosure. I am not sure how IEM's work, but it must have something to do with creating a seal inside the ear canel. If you don't get a good seal, you don't get the low end. Randy

Well for sure there's roll-off, but I can compensate with the low-pass filter..

IEMs work similarly to any other transducer, vibrating a diaphragm. It's just the methodology is different. Anyway take your pick; there's lots of normal dynamic phones that are 1" in diameter (or less) that can reproduce 20hz.

The question is can a 6" driver produce enough pressure at 20hz without distortion...

 

[Zenja]

Even using that way of thinking about it, you'll still have a big problem because the roll-off rate that low below the optimum frequencies is extremely steep. It'll be nowhere near flat, or acceptable. I'm sure that there'd be lots of distortion too.

I actually scanned through the hundreds of drivers that WinISD comes loaded with. It's basically all sub drivers, but there's only a few 6 inch ones. All of them came nowhere near being acceptable for what you're trying to do. If anything, you should really consider 8" drivers. I was able to find some that would work nicely down to 20Hz (with the right vented box). For example, the JL 8W6 tuned to 20Hz in a 65L box projects as doing 20Hz to 50Hz at -1dB to -3dB from its response at the highest frequencies. I'm not sure if it would be worth doing for you though.

Actually, I just found a possible solution using 6" drivers. Two Morel 6.1 drivers in a 150L box tuned to 20Hz gives this graph (the single JL 8W6 is above it and the Morels are the white line)