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Old 21st May 2007, 04:44 AM   #1
aceinc is offline aceinc  United States
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Default TL/TQWT conceptual question

If this is a stupid question, be gentle.

Based on my understanding, which is quite miniscule I assure you, one of the problems with TL type designs, is peakiness at certain harmonic frequencies above the tuning freq.

If one were designing a TL sub could one feed the output of a bandpass enclosure into a TL since bandpass enclosures roll off high as well as low freqs fairly steeply?

Would this have a beneficial affect of reducing the volume of the higher frequencies so that they wouldn't be a concern?

I was thinking of a 6th order bandpass with the front chamber firing into the room, and the rear chamber firing into a TL.

I am sure someone else has thought of this. I'm sure someone has thought of pickle flavored ice cream as well. Has anyone tried to model this concept? (the speaker, not the ice cream...)

Paul
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Old 21st May 2007, 10:57 AM   #2
Volenti is offline Volenti  Australia
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The out of passband peaks can be avoided with sufficiently steep filters and some of the inband peaks can be dealt with by driver offset and carefull design, I'm assuming we're talking about non-tapered bass lines here.

I personally don't experience sufficient issues with harmonic peaks to warrant spending time to get rid of them, I can avoid them easily enough as it is (I build one or two a week, car audio)

[edit]I can't see feeding the output of a bandpass into a TL achieving good results, it's hard enough to get 6th order BP to sound any good as it is, and the whole point of using the bandpass, filtering, can be done better electronically.
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Old 21st May 2007, 03:29 PM   #3
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wouldnt GD be like...off the wall? i always thought BP had big GD and thats why no one used it.

so icant really help with that...

...BUT i can ssure you that pickle ice cream is already thought of and sold somewhere in the US(saw it on TV once) they chose dill too...

...so by that logic, id say try building it, maybe SOMEONE out there at least will like it!
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Old 22nd May 2007, 12:46 PM   #4
Volenti is offline Volenti  Australia
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Quote:
Originally posted by xstephanx
wouldnt GD be like...off the wall? i always thought BP had big GD and thats why no one used it.

Yea GD is one reason why this isn't such a hot idea, though I use 4th order BP in certain suitations and can get the GD down to ~twice that of sealed so it's not too bad, has it's niche.
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Old 22nd May 2007, 12:58 PM   #5
aceinc is offline aceinc  United States
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What is the rule of thumb for Group Delay?

I would think that the nature of tuned pipes would be a fairly large GD.

Paul
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Old 23rd May 2007, 02:10 AM   #6
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I just can't seem to picture your concept. How do you connect an enclosure that operates on the rear wave of a direct radiator(TL) onto a bandpass enclosure which has no rear wave?
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Old 23rd May 2007, 02:17 AM   #7
aceinc is offline aceinc  United States
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In a 6th order bandpass enclosure, both the front and the rear of the speaker have ports, and are generally tuned to different frequencies. It is my understanding that 6th order bandpass enclosures are difficult to do well, but they supposedly provide a wider frequency range, and somewhat more output.

Paul
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Old 26th May 2007, 02:19 PM   #8
Volenti is offline Volenti  Australia
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Quote:
Originally posted by aceinc
What is the rule of thumb for Group Delay?

I would think that the nature of tuned pipes would be a fairly large GD.

Paul
A rule of thumb is pretty difficult since an "acceptable" amount is extremely frequency dependant, though generally the lower in frequency you go the more GD you can get away with.

I think the reason that tuned pipes can sound as good as they do isn't because of low GD (their GD is probably similar to a vented box of similar tuning), it's because of the lack of stored energy compared to a conventional enclosure, especially when the pipe in question is tapered and/or stuffed.
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