Tapped horn for TB W8-670C?

lost eden

Member
2009-09-02 10:47 am
A while ago I bought 2x Tang Band W8-670C when half price. I built a basic bass reflex cab for one, tuned to 43Hz, which has served me well (design, sim, pictures here).

I'm wondering whether I can build a tapped horn for the second driver that will play lower than my existing bass reflex design? I don't really know much about what makes a driver suitable for tapped horn loading or not, so would greatly appreciate if somebody could briefly look at the T/S values for the W8-670C & just let me know whether it is at all possible. Datasheet is here. If so then I can start learning how to use hornresp.

I realise I could just build a larger bass reflex enclosure, but I would like to keep it as small as possible - I'm thinking something like an upscaled version of volvotreter's 6.5" 30Hz tapped horn.
 

OscarS

Member
2011-01-02 10:44 pm
A while ago I bought 2x Tang Band W8-670C when half price. I built a basic bass reflex cab for one, tuned to 43Hz, which has served me well (design, sim, pictures here).

I'm wondering whether I can build a tapped horn for the second driver that will play lower than my existing bass reflex design? I don't really know much about what makes a driver suitable for tapped horn loading or not, so would greatly appreciate if somebody could briefly look at the T/S values for the W8-670C & just let me know whether it is at all possible. Datasheet is here. If so then I can start learning how to use hornresp.

I realise I could just build a larger bass reflex enclosure, but I would like to keep it as small as possible - I'm thinking something like an upscaled version of volvotreter's 6.5" 30Hz tapped horn.

Do keep in mind, that nothing is free. If you keep the enclosure volume the same, you're either going to have to sacrifice low-end extension, sensitivity, or a little of both in the tapped horn. For example, if you want 30Hz extension while keeping the enclosure volume the same, sensitivity will suffer. No escaping the evil triangle.
 

lost eden

Member
2009-09-02 10:47 am
Do keep in mind, that nothing is free. If you keep the enclosure volume the same, you're either going to have to sacrifice low-end extension, sensitivity, or a little of both in the tapped horn. For example, if you want 30Hz extension while keeping the enclosure volume the same, sensitivity will suffer. No escaping the evil triangle.
Am I right in taking from this that the volume of an enclosure defines constraints on the low-end extension & sensitivity, regardless of the enclosure design (eg bass reflex, tapped horn, scoop, hybrid-6th-order-bandpass-horn, etc.)? So a tapped horn of similar dimensions to my current bass reflex won't be able to play lower without sacrificing sensitivity?

If so I will have to consider how to accommodate a larger enclosure into a small room, perhaps something that fits under a bed or stands behind/along a desk. My current bass reflex design can't keep up with my mains as it is, so sacrificing sensitivity isn't an option.
 

OscarS

Member
2011-01-02 10:44 pm
That is absolutely correct. There is no free lunch. You can get 10% off your lunch, but ain't no way she's letting you get it for 50% off. :D Mother nature has a very clever way of hiding these kinds of manifestations of the laws of physics. Meaning that you can "nudge" things just a bit here and there that make it seem like you're eating without paying, but once you try and get greedy with things like ultra-small boxes, ultra-low extension, and massive sensitivity, you'll get called on your bluff and get busted and have to pay full price. :)

The the only way to "cheat" the evil triangle that is Hoffman's Iron Law (aside from doing things like corner 1/2 Pi boundary loading and things like that), is to sacrifice bandwidth to get a bump in sensitivity within a narrow band. Even then, it's not really cheating, because you're giving up something for something else.

I would venture to say, that driver would be a very good candidate for a tapped horn. Qts is low enough, Fs is just right for high-20s/low 30s primary tuning, and Vas is not too large.
 
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