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ceharden 
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 Topic: Reflex or Bandpass Sub-bass?
Posted: 18 December 2006 at 8:21pm |
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No answers that it should be a horn please!
I need a sub-bass cab to eventually sit underneath my new kick horn. Usefully a slightly modified X1 fits into the same dimension cab as the kick horn. Been doing a lot of playing in WinISD comparing different tunings etc. Generally the BP6 cabs come out with about 2dB extra efficiency over their useable range compared with a reflex cab with the same driver. The BP6 is also at least 1.5x the volume.
Is the extra cabinet size worth the 2dB gain you get, or should I just use reflex cabs and have one extra to make up the output? Are there other benefits with the bandpass.
As an aside, anyone else modelled the X1 and not quite got the response shown on the plan page? Mainly regarding sensitivity and low extension.
Regarding modelling, any idea how much port extension you get on the front chamber of the X1 due to the lack of a clear transition from chamber t port?
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hifiger
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Posted: 18 December 2006 at 8:23pm |
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How low do you want the subs to reach?
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ceharden
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Posted: 18 December 2006 at 8:28pm |
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The kick horn goes to about 55Hz, probably crossover at 65-70Hz. Want something to go from there down to about 35Hz. X1 type frequency range.
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mobiele eenheid
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Posted: 19 December 2006 at 9:10am |
 Is the extra cabinet size worth the 2dB gain you get, or should I just use reflex cabs and have one extra to make up the output? Are there other benefits with the bandpass |
If you want maximum bang for the buck than it looks like an option to me, 2 dB isn't perceived by the human hearing as much at all.
Double reflex would offer 6 dB due to coupling and doubled powerhandling, which is more than the bandpass but will cost more to. Might be easier for you to handle a multiple of single reflexes tha a loggy BP.
BP and reflex generally do sound different.
| As an aside, anyone else modelled the X1 and not quite got the response shown on the plan page? Mainly regarding sensitivity and low extension |
Yes and yes, many have.
Dom's measurement somewhere around seems to agree with the lack of low end extension.
| Regarding modelling, any idea how much port extension you get on the front chamber of the X1 due to the lack of a clear transition from chamber t port? |
I don't know, I do expect it to be there but not much, the measurement should clear things up.
Wkr Johan
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ceharden
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Posted: 19 December 2006 at 10:40am |
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Cheers, that's pretty much confirmed my thinking on the subject. I think I'll wait for now cos there are plenty of 18" reflex boxes kicking around the local area to play with, singles and doubles. I need to design a new twin 18" for a local PA company anyway (not that they know it yet but I don't like their current design!!!)
One of the things I like about the bandpass is that from an impedance point of view, it looks a lot nicer for the amp to drive. The reflex has a massive impedance peak in the middle of the range of interest whereas the BP has two smaller peaks. In my mind that means better control over the cone and a tighter sound. Low tuned reflex boxes can sound a little loose and you can also get a dip between the output of the port and the direct sound from the cone taking over.
Might be a case for some MDF prototyping.....
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norty303
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Posted: 19 December 2006 at 1:12pm |
haaaaaaang on a second......
Isn't djk's post on another thread about bandpass boxes directly contrary to some of the things being said here regarding box volume?
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This 6th order design is of a type that has the highest efficiency vs the minimum box size and the maximum bass extension possible.
Posted by djk ( M ) on July 25, 2005 at 00:55:59
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB). |
Also, this is the wrong way around...
| Dom's measurement somewhere around seems to agree with the lack of low end extension. |
Dom's measurement of the letterbox X1 revealed extended low range response over the original, which Rog explained to us at Plasa last year was more than likely due to the larger surface and port area in contact with the ground. It might be his measurements of the groups of HD15's you're thinking of.
Edited by norty303 - 19 December 2006 at 1:14pm
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ceharden
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Posted: 19 December 2006 at 1:20pm |
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Hmmm... since I'd be going for a design very similar to the letterbox X1 and could expect a similar extended response maybe it would be a good plan..... Really need to borrow one and try it with my kick bin I guess....
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Rog
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Posted: 20 December 2006 at 7:41pm |
Did you not see the plot I posted recently of an X1 and Lab sub.
The X1 looks to have an F3 of around 33Hz and an average sensitvity of about 101 dB. Ok the measurement conditions were not perfect. but thats what you would have heard if you were in that room in that spot at that time. Its not far off the plot on the plan, which is a simulation and not a measured plot. You have to take into account that most design programs think the ports are in free space. My simulations take into account that the ports will be slightly longer due to half space loading. I also did my X1 simulation plot in quater space as it was designed for a club where it would be used on the floor and against a rear wall. This accounts for the sensitvity being a bit higher on the plan plot.
If you use WINisd or bass box pro it will show the X1 to have a higher F3 point. Only when all considerations are taken into account will your simulation look like its measured response.
Yes letterbox X1 wil play lower due to larger surface area against the floor and more port area contected to the floor.
Rog.
Edited by Rog Mogale - 20 December 2006 at 7:42pm
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cyranotr
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Posted: 21 December 2006 at 3:12am |
See X1 measurements (real). Cabinet is chip board (bad) and driver not optimised for it. still....I plotted impedence, freq on ports. The box was at 50cm from ground at time of measurement. Hope it can halp. (see X1 Measure TOPIC)
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Trust your ears...
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mobiele eenheid
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Posted: 21 December 2006 at 4:46am |
| Isn't djk's post on another thread about bandpass boxes directly contrary to some of the things being said here regarding box volume? |
I don't see how it is, could you elaborate?
| Dom's measurement of the letterbox X1 revealed extended low range response over the original? |
Yes, I remember that.
I do also seem to remember a measurement from Dominic, showing a original X1 with less low end extension as per plans.
To bad it got a 24 dB highpass, but if my extrapolation abilities aren't playing tricks on me it confirms as stated above.
Wkr Johan
Edited by mobiele eenheid - 21 December 2006 at 4:47am
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