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Basic Cabinet Tuning Tutorial?
- Thread starter AchtungBass
- Start date
They're sealed, you don't tune them. If you're talking about an HLF or something, that's already all figured out at Ampeg.
billfitzmaurice
Commercial User
- Sep 15, 2004
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- Owner, Bill Fitzmaurice Loudspeaker Design
The proposed tuning frequency is 55Hz.
The internal volume per 3015 will be 3.65 cubic feet, 7.3 cubic feet total for the 215.
The cab's dimensions will be 44" tall x 23.5" wide x 16" deep. The dimensions of the horn I'm using are 10.79" wide x 6.46" tall, so another 6 1/2" on top of two 15s makes for a taller box. And the four 4" flared ports contribute to the width.
I play 4-bangers for the most part, but 5ers at times. Does 55Hz seem like a "not unreasonable" figure?
- Nov 24, 2008
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- Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
I think 55 Hz is a bit high from a fartout standpoint. I'd go with 45 Hz or so in that size box. That will still give you plenty of output at the first overtone of low-B, but most importantly more headroom before fartout.
A "builder" does not have to be an expert but they do need to be able to build accurately to a plan!
If you are an expert design engineer, you need to know the tuning principles etc and be able to get the information across to a builder to know that what they build will work.
This goes for BFM and Fearful cabs and many others. The designer is the expert. The builder is usually not. If you expect them to be, you are mearly providing a specification for them to design and build and they will charge you more!
If you have a low E bottom, you could look around 48 to 52 Hz tuning. If you have a low B, it will easily fart out if you tune in to the 50's so tune lower, maybe 37 to 43 Hz. I tend to favour lower tuning as my design principles help loading further up as well but you may want to go for the higher numbers.
This seems like a good post - the people on the assembly line don’t design the product - they just build it (so check their work). But, 37 to 43 Hz seems a bit low to me - but I’m just a bass hack learning.
Thank you... The message is getting through at last!
Low tuning is only ok is you have a broad resonant or multimode response or you will find at around twice the frequency you end up farting out.
For a basic reflex design, use the upper of the figures I quoted. If you go any higher, particularly in a large ish box, that B string will always fart out, especially as the B string generally has more fundamental (potentially) than the E for a given note. (obviously slightly driver dependent, only a guide) If you value your cab and drive it hard with the low notes, don't tune too high!
Probably should have asked this earlier, but better late than never.
Is the cabinet tuning frequency separate & independent from the internal volume figure & other WinISD modeling calculations? I believe it is, but would appreciate a quick affirmation or dissent.
Also, thinking 50Hz tuning may be a good happy medium for me with this 3015s-loaded, 7.3 ft3, 215 box w/four 4" flared ports. I play 4-bangers for the most part, 5'ers from time to time.
Is the cabinet tuning frequency separate & independent from the internal volume figure & other WinISD modeling calculations? I believe it is, but would appreciate a quick affirmation or dissent.
Also, thinking 50Hz tuning may be a good happy medium for me with this 3015s-loaded, 7.3 ft3, 215 box w/four 4" flared ports. I play 4-bangers for the most part, 5'ers from time to time.
Yes, they are independent from each other, but work together with the driver to make the system.
Example, the lowend in a small box tuned to 50 and a larger box tuned to 50 will sound very different from each other. One may work very well, the other, not so much. It's a balancing act.
Example, the lowend in a small box tuned to 50 and a larger box tuned to 50 will sound very different from each other. One may work very well, the other, not so much. It's a balancing act.
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
+1. Tuning frequency and actual response are only peripherally related. Just as driver size and watts in and of themselves mean nothing neither does Fb.
Letting LSPCAD optimize the setting results in a tuning of 51.5 Hz in a fairly small volume of about 76 litres. In enclosures of that size i find singnificantly lower tunings of the 3015 sounding a bit thin. Recently i actually increased the tuning of my box into that range. Well, maybe a 215 design could live with a tuning somewhat lower - but the 115 definitely not.
A good rule of thumb is that the port will control cone excursion about 1/2 octave on either side of the port frequency. If the tuning is 55 hz, one "octave" is half that, or 28 hz. A half octave would be around the middle of 28-55 hz or about 41 hz.
The cabinet should be fine for a 4-string bass since the open-E is about 41 hz. Not too good for 5-string or drop-D basses.
Good Luck!
Hmm... hopefully this is a good place to ask this. I feel like I've read a number of posts around TB that imply that Vb does not scale with number of drivers, i.e. Vb for 1 driver =/ 1/2 Vb for 2 drivers, etc. Put another way, that there is a difference in day-to-day playing between a double chamber 2-15 and a fully open 2-15, for example. True or false?
I think I may be getting confused with a couple different concepts: 1) if one driver dies, it's bad news for the remaining speaker(s) in a now too-big box. 2) Speaker coupling provides more lows (which I think is what that quoted post above is getting at).
I'm asking partly out of sheer curiosity and partly because I used half of JohnK's 2x15 Vb as a data point for a single 15 box I'm building now. So, am I screwed or what and does the question make sense?
You're not screwed.
1/2 box size with 1/2 the number of drivers, tuned to the same frequency would have the same freq. response as johnk's cab. Just 3db less output with the same amount of input and 1/2 the powerhandling.
Some companies make thier 2x cabs a little smaller than double size their 1x cabs just for decreased size/weight, portability, etc. If they wanted them to be same, they would make them double size.
Example is, a lot of companies use the same box for their 410 and 115 cabs, but also use the same box for their 610 and 215 cabs. Has more to do with cutting production costs than it does speaker engineering.
1/2 box size with 1/2 the number of drivers, tuned to the same frequency would have the same freq. response as johnk's cab. Just 3db less output with the same amount of input and 1/2 the powerhandling.
Some companies make thier 2x cabs a little smaller than double size their 1x cabs just for decreased size/weight, portability, etc. If they wanted them to be same, they would make them double size.
Example is, a lot of companies use the same box for their 410 and 115 cabs, but also use the same box for their 610 and 215 cabs. Has more to do with cutting production costs than it does speaker engineering.
I'm asking partly out of sheer curiosity and partly because I used half of JohnK's 2x15 Vb as a data point for a single 15 box I'm building now. So, am I screwed or what and does the question make sense?
JohnK's box seems to have a size slightly larger than the optimum of the simulations but still pretty close to it.
In my own cabinet i recently went from a 40 Hz tuning over some 45 Hz toward roughly 51 Hz - not measured, but with ballbark corrections of the port at the side of the enclosure.
From this experience and the sound clips JohnK posted i would not go much below about 50 Hz - the sound will probably lose.
Please remember that the tone of an electric bass is usually dominated by its 2nd harmonic. Therefore, the value of the lower corner frequency is not as important as often believed.
Beate
A single driver is -6dB compared to two wired in parallel.
RTA measurement of a single driver shows -6dB less output compared to the pair.
-3dB for the loss of the 2nd cone area, another -3dB for the loss of the 2nd power sink.
That is only assuming the level of power changes with a different number of drivers.
My tube head is 400 watts into a 4 or 8 Ohm load. If I double my speakers I only gain a 3 dB increase.
