QuestionQUESTION: What do you think the keys would be to building a vehicle that could play 169 for 30 seconds? Let's just say they opened up a 169.9 bassrace class. What kind of attack would you make to achieve this?
I know you've built SS cars working at 170. Could you apply those efficiency and physical concepts to a musical enclosure?
Just let me know if you've ever considered something like this. One of my dreams is building a 159.9 car, but if it's possible down the road, I may consider an attempt at this.
ANSWER: Well that is a tall order!
You could certainly use some of the high SPL methods for music.
But to average a 169.9, it would take an extreme car capable of burping in the mid 170s.
Even if Bob Perillo would have the best Bass Race run of his life, he would only manage to bass race 163s when he burps 169 at 53hz.
The thing with SS cars is the loss in sympathetic vibration. And in our experiments, the fatigue of body panels and glass over the course of a 30 second run starts to diminish the score. That tied with the loss of battery power and equipment heat means a huge drop from a burp score to a bass race score. Some smaller 129.9 and 139.9 systems can bass race very close to what they burp, but body fatigue is a factor in the higher classes.
A reinforced cabin is the way to go with a true 169.9 Bass Racer. Just because you can build a car that peaks at 180 dB at 79hz, doesn't mean you can't retune it to play flatter and lower to do mid 170s at 45hz. Then throw on some songs and let it bass race a 170.
So the cabin reinforcement would take care of body fatigue. Then just get an oversized electrical system to take care of power fatigue.
You can also spray NOS on the woofers to take care of woofer fatigue.
Let me know if you would like to discuss this more. I'm interested in these types of projects and I can definitely help you out! =]
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QUESTION: So if I were to go for this, should I go straight quarter-wave port or should I go for a bandpass to abuse the narrow spike? I've never seen the extreme class use bandpass and I'm wondering if they are missing something. I'll keep this short since I'm going to ask a lot of questions. Thanks again mang!
AnswerWell first off, you would probably go with a 4th order if you were to try this, but I wouldn't recommend it.
I'll tell you now that I don't compete dBDrag, but I've been around long enough to get the basic concepts of 170+. Alan Dante, Craig Butler, etc. have information and techniques that nobody really knows. They won't give up their tricks of the trade either! Everybody will do the work and build ten thousand boxes to get where they are just like they did.
A bandpass going for 170+ would be extremely difficult to design to achieve the same level of measured pressure as a quarter-wave. Even after measuring resonance and impedance rise, using the "narrow spike" you mentioned would destroy the subwoofers with the appropriate power (which would be much less than a quarter wave since your efficiency would be maximized in the chambers). While the passband would have a significant gain, the acoustics wouldn't allow for a match of the quarter-wave.
Gain would be limited to around 3dB and your s factor would be low. With this setup, there would be an incredible amount of uneven pressure on the cones since you would need to port on drivers side to maximize compression at the meter. AND you would need a very LARGE vehicle to pull it off which would also hurt your score since the large cabin, and respective modifications would either destroy air flow or not support cone movement (due to the ratio of cabin volume and enclosure).
I've never seen it done, and I don't see any future plans for it. I honestly can't give you definitive answers to this other than theory and experience.
However, the rarefaction is what hurts your score. A 4th order with tremendous gain will have a tremendous backwave and inverse compression as a result. This is why the quarter-wave method works so well. The meter barely sees less than amplitude. And I'm sure you know, but your distances have to be EXACT for this to work properly.
Keep the discussion going! =]
