Is this to be a serious cabinet used for actual practices and performance? If so, there are so many issues.
Full range bass cabs are not tuned for hi-fi type bass extension. You've got a 10" driver with 3mm Xmax. It's not even close to being up to the job. Muti-way bass cabs that are tuned for flat bass use PA subwoofer drivers: 12" and 15" drivers with much larger Xmax.
If you have already bought that driver I think your only option is to go with a sealed cabinet and try to protect it from overexcursion.
Full range bass cabs are not tuned for hi-fi type bass extension. You've got a 10" driver with 3mm Xmax. It's not even close to being up to the job. Muti-way bass cabs that are tuned for flat bass use PA subwoofer drivers: 12" and 15" drivers with much larger Xmax.
If you have already bought that driver I think your only option is to go with a sealed cabinet and try to protect it from overexcursion.
Nothing wrong with a 10" driver and a 3mm Xmax. One of the most commonly used 10" drivers is the Eminence Delta-10 which has 3.5mm.
Trick is managing expectations. A 1x10" cab is never going to give the bottom-end feel of a 2x15". That said, a single 10" driver can put out useful SPLs above 80Hz or so, which is the octave above the low-E string. Given that the harmonics are usually louder than the fundamentals anyway, I'd aim for a smallish box tuned to 80Hz and then add a highpass filter if the bass driver farts when unloaded. Some will overload gracefully when driven past Xmax, and some will just make bad noises.
Chris
Trick is managing expectations. A 1x10" cab is never going to give the bottom-end feel of a 2x15". That said, a single 10" driver can put out useful SPLs above 80Hz or so, which is the octave above the low-E string. Given that the harmonics are usually louder than the fundamentals anyway, I'd aim for a smallish box tuned to 80Hz and then add a highpass filter if the bass driver farts when unloaded. Some will overload gracefully when driven past Xmax, and some will just make bad noises.
Chris
if just one 10 in a cabinet - then I'd suggest a Karlson enclosure. xrk971's "XKi" tread has dealt with dual stacked drivers with smallish front cavity and K-aperture. Rear chamber volume and system tuning would be set for "punch" - probably no more than 35L per driver. ChurritoTierno might ask xrk971 to run an XKi alignment for that (Eminence?) 10. I have a 0.62 scale "K15" - cutoff with even Beta10cx is quite high - Vb rear ~25 liter). A change in port area will change "voicing" but nothing much on a graph (why ?) The little K has 3-5dB more output in the 100-200Hz octave than Beta10cx in a 5 cubic foot Karlsonator tuned to 37Hz. Under sine conditions, when I played with obstructing part of the inner port with a narrow slot in a board, a lot of harmonics were introduced (modulated noise?)
this is probably ~ 1Pi - the green trace is for the cabinet whose total bulk is a bit less than 2 cubic feet.
Dual driver XKi - for little fullrange
for the 10, I'd expect system tuning to be in the mid-60s depending upon rear chamber volume
a Karlson 12 would be an upper limit imo so around 36 liter or so per driver, xrk971
can do an akabak sim with your numbers. To save time on his part - put your driver's T-S
in this form
Def_Driver 'Fane Sovereign Pro10" | Fane 300W rated speaker with 4mm VC overhang, Qts = 0.32, 2.5" VC, 56oz ferrite magnet
Sd=378 cm2
Fs=58 Hz
Mms=37g
Qms=6.08
Qes=0.34
Re=5.7 ohm
BL=15.3 T/m
Le=1.68mH
Vas=41L
this is probably ~ 1Pi - the green trace is for the cabinet whose total bulk is a bit less than 2 cubic feet.
Dual driver XKi - for little fullrange
for the 10, I'd expect system tuning to be in the mid-60s depending upon rear chamber volume
a Karlson 12 would be an upper limit imo so around 36 liter or so per driver, xrk971
can do an akabak sim with your numbers. To save time on his part - put your driver's T-S
in this form
Def_Driver 'Fane Sovereign Pro10" | Fane 300W rated speaker with 4mm VC overhang, Qts = 0.32, 2.5" VC, 56oz ferrite magnet
Sd=378 cm2
Fs=58 Hz
Mms=37g
Qms=6.08
Qes=0.34
Re=5.7 ohm
BL=15.3 T/m
Le=1.68mH
Vas=41L
An externally hosted image should be here but it was not working when we last tested it.
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Hello, and welcome!
In your pdf is the sentence "Also the cone excursion will be half of that a single speaker Xmax =1.05mm." I do not think this is correct; the point is that, with two speakers operating, there is twice as much speaker piston area moving air. So, for the same sound pressure level, each speaker cone needs to move only half as far.
But this is not the same as Xmax, which is the maximum distance one speaker cone can travel. That is a mechanical property of the driver, and stays the same, whether you use one driver, two, or four.
So, for a given SPL, each speaker only needs half the "x" compared to one speaker alone. But Xmax for each speaker is still the same 3 mm as before. That means, when both speakers are driven all the way to their Xmax limit, you are now moving twice as much air as before, making +3 dB SPL more than one speaker alone in the process.
Actually it gets better than that - having twice the speaker cone area also increases speaker efficiency by coupling to the air more efficiently. So you should get about another +3 dB more from that effect.
Combining both effects, if you drive two speakers in phase with the same low-frequency signal all the way to their Xmax limit, you should get nearly 6 dB more SPL than you could get from one single speaker. (Of course it takes twice as much power to drive the speakers, that's +3 dB more power. But the extra +3dB on top of that is a free gift, because of the improved coupling to the air.)
The other question you asked - "Could I take some intermediate value for the box volume?" is an interesting one. Firstly, published Thiele-Small parameters for drivers are never exact, and there are also manufacturing tolerances to deal with between one driver (speaker) and another. Then there are correction factors like the volume of the loudspeaker itself (volume of magnet, plus conical volume of speaker cone) which subtract from the volume inside the box.
So there is really no way to get exactly the right volume the first time - usually, if you want it exact, you have to build, measure, modify, measure, and so on, until the speaker behaves the way you want. This is the normal way prototype speakers are developed in a factory, before the design is finally frozen and ready for production.
But how exact does it have to be? If the box volume isn't exact, the low-frequency alignment won't be exactly what you want. This means the frequency response won't be exactly the same shape you intended. But if the difference is slight, you probably won't be able to hear it; particularly because simply moving a perfectly designed bass cabinet into a different room will usually completely mess up the frequency response due to room interactions!
And let's not forget, you have tone controls, and maybe a graphic EQ, on your guitar and bass amp, which will also help you make small changes to frequency response, to correct for whatever minor imperfections your design has.
So if you already have a box that is nearly the right size, or perhaps you wind up using one less sheet of plywood by slightly changing the volume of the box, I would go ahead and just do it. It will probably make too little difference to matter.
This is bass guitar we're talking about, not precision audio monitor speakers, where you really want everything flat to less than +/- 1 dB if you can manage it.
And I agree about the bottom octave not being important: I usually use a 60 Hz high-pass filter with my 5-string bass, which has a low B tuned to 30 Hz. It sounds wrong if you come from the Hi-Fi world, but cutting off the bottom octave of the bass actually makes the bass sound better, less boomy, and it sits better in the mix with the drums.
-Gnobuddy
As far as I know, all bets are off with a tube amp - the output impedance is so high that the loudspeaker Thiele-Small parameters are worthless, Q of the driver goes up to Qms rather than Qts, and because Qms is huge (far greater than 0.707) there is no hope of designing a controlled bass frequency response.
However, I don't think anyone mentioned using a tube bass amp so far in this thread.
-Gnobuddy
Dual 10in drivers in XKi works well
Freddi has a good suggestion for an XKi for this purpose. I agree that tuning this to maximize 80Hz and limit excursion is the way to go. I used the Vas spec to size this at 46 liters for both drivers and this will tune it a bit higher for more output and less cone movement. With a 12in wide cabinet and qnty 2 x 12in wide x 1in deep x 9.0in long vents, make the front chamber a "V" with a vertex in the middle so that 20% of the box volume is in the front chamber and 80% is in the rear chamber. Wire the drivers in parallel and here is the predicted SPL vs frequency for 2.83v input. It is 100dB sensitive with 03dB at 72Hz. This will play the 80Hz notes very clearly and loud. Ignore the falloff above 300Hz as this model is for the bass response only (I do not have the direct radiation from the cone passing through the aperture captured here):
Here is the cone excursion at 23vrms input, use a 51Hz high pass filter:
Here is the max SPL at 23vrms - about 118dB at 1m, not too shabby:
XKi - X's ab initio Karlson 6th Order Bandpass
Make the box like this (but out of wood of course):
I would open the aperture up a bit to let more highs out...
It is actually a pretty compact cabinet. If you want deeper extension, say to 40Hz, that is a challenge as the fs is 54Hz. It can be done but overall SPL will be very limited, and cabinet will be double the volume.
Freddi has a good suggestion for an XKi for this purpose. I agree that tuning this to maximize 80Hz and limit excursion is the way to go. I used the Vas spec to size this at 46 liters for both drivers and this will tune it a bit higher for more output and less cone movement. With a 12in wide cabinet and qnty 2 x 12in wide x 1in deep x 9.0in long vents, make the front chamber a "V" with a vertex in the middle so that 20% of the box volume is in the front chamber and 80% is in the rear chamber. Wire the drivers in parallel and here is the predicted SPL vs frequency for 2.83v input. It is 100dB sensitive with 03dB at 72Hz. This will play the 80Hz notes very clearly and loud. Ignore the falloff above 300Hz as this model is for the bass response only (I do not have the direct radiation from the cone passing through the aperture captured here):
Here is the cone excursion at 23vrms input, use a 51Hz high pass filter:
Here is the max SPL at 23vrms - about 118dB at 1m, not too shabby:
XKi - X's ab initio Karlson 6th Order Bandpass
Make the box like this (but out of wood of course):
I would open the aperture up a bit to let more highs out...
It is actually a pretty compact cabinet. If you want deeper extension, say to 40Hz, that is a challenge as the fs is 54Hz. It can be done but overall SPL will be very limited, and cabinet will be double the volume.
Attachments
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Just to clarify - Qes and Qts are Thiele-Small driver parameters, they are independent of the source.
Qes is the driver resonant electrical Q at the driver resonance frequency, due solely to inherent electromagnetic damping.
Qts is the driver total Q.
Changing the value of the amplifier output resistance has no effect on Qes or Qts. This can be readily confirmed using Hornresp by entering a large value for amplifier output resistance Rg and checking the driver Thiele-Small parameter values by double-clicking on the Sd input box. Qes and Qts will remain unchanged.
I read in a book, actually was an example of enclosure calcutation where the author "modifieded" the Qes of the driver to take in account the output impedance of the amplifier... Qes (new) = Qes*(1+Ramp/Re)
stacked
http://home.planet.nl/~ulfman/images/soundl12.jpg
Stanley's rig with helper tweeter
https://community.klipsch.com/uploads/monthly_10_2013/post-16352-1381928099972.jpg
http://home.planet.nl/~ulfman/images/soundl12.jpg
Stanley's rig with helper tweeter
https://community.klipsch.com/uploads/monthly_10_2013/post-16352-1381928099972.jpg
incredible job Freddi.
In reallity, i'm not very handy and don't really think that I could do that kind of wood working, even in 10 years..
Doing a simple vented box is really a challenge to me.
So, is there the posibility of blown the drivers beacouse I do not "hit the volume targed for a specific alignement"??
First you should attach some pictures of this driver so people know what they are dealing with. It may not be a suitable candidate.
Assuming it is suitable, I would probably do a 60-90 liter box and tune it to ~60 Hz or so. As another said, if it complains at low frequencies, add a 2nd order subsonic filter at ~60-80 Hz. You won't blow a driver by "not hitting volume target", you blow drivers by applying too much power or driving them with tones below their tuning frequency.
Skip the "Kult of Karlson" with the silly reflector business...
Assuming it is suitable, I would probably do a 60-90 liter box and tune it to ~60 Hz or so. As another said, if it complains at low frequencies, add a 2nd order subsonic filter at ~60-80 Hz. You won't blow a driver by "not hitting volume target", you blow drivers by applying too much power or driving them with tones below their tuning frequency.
Skip the "Kult of Karlson" with the silly reflector business...
Hi Ron.
This is the driver:
4 pack 10" 8 Ohm Eminence SWR Goliath Woofer Midbass Bass Guitar Speaker USA | eBay
I wrote to the seller asking the T/S parameters. He sent me this:
Re 10.87 Ohms
fs 55.9 Hz
Le 1.46 mH
Mms 30.4 grams
QM 8.23
Mmd 26.7 grams
QE 0.48
Cms 0.267 mm/N
QT 0.45
Rms 1.297 N*sec/m
Xmax 3.01 mm
Vas 46.5 liters
Pmax 150 Watts
SD 350.1 cm^2
Bl 15.53 Tm
VD 105.4 cm^3
Coil Diameter 2.00 Inches
EBP 116.1
Gap Height 0.313 Inches
Magnet Weight 38 ounces
Efficiency 1.63 %
Winding Width 0.550 inches
SPL 94.1 dB 1W-1m
By the way, is strange the value of Re = 10,87 Ohms for a 8 Ohm rated driver, don't you think?
I don't compared yet to the eminence CA10 specs,.. but the seller said me that both are very similar.. by the pictures It is obvious that the frame is identical...
I could copy a SWR cabinet but I don't know wich version of the Goliath used this speaker...
My first idea was to build two 2x10 for transportability rather than a 4x10.
Thanks to all for your answer!!!
P.D.: Sorry for my english.. For sure is really bad.
so it looks like the drivers are usually in a ~100-120L enclosure for 4 of them. Probably fairly simple to get an upper and lower bound on the tuning frequency. I'd guess the port at the bottom is perhaps 23" x 1.5" or so - 50-51cm x 4 cm Length could be perhaps 8-10" or 20-25cm . Assuming 100-120L is correct, it sims better wit ha ~65-70Hz tuning, IMO
Your english is fine, no need to be self conscious.
Your english is fine, no need to be self conscious.
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We may not be thinking about the same kind of valve amp, but, FWIW, the question of valve amp output impedance came up on a guitar-amp thread on another forum. Valve guitar amps invariably have pentode outputs, and only a few dB of global negative feedback.
Even with 10 dB of global negative feedback (about the maximum you might find in a valve guitar amp), I estimated Zout - for a typical guitar amp with 6V6 outputs - was in the ballpark of one hundred ohms, a lot higher than the DC resistance of a typical loudspeaker.
If that estimate is even close to correct, the loudspeaker is, to all intents and purposes, being driven from a current source, because the amplifier Zout is more than an order of magnitude larger than the voice coil resistance. There would be essentially no damping due to back-EMF driven current flow in the coil, and driver mechanical Q would rise to virtually Qms in free air (and even higher if you then mount it in a sealed enclosure).
Here's the reasoning behind the back-of-the envelope amp Zout estimate I made: a 6V6 datasheet lists anode resistance of 77k at 315V on the anodes. A push-pull pair is typically used with an 8k anode-to-anode output transformer feeding an 8 ohm speaker; each half of the primary is therefore 2k.
Due to the output transformer, the impedance ratio from anode to speaker is therefore (2000 ohms/8 ohms), or 250:1.
Therefore a 77k anode resistance will appear, at the speaker, to be (77000/250), or 308 ohms.
Negative feedback reduces output impedance in proportion to the loop gain. If we have 10 dB global negative feedback, the loop gain is reduced by a factor of 3.16 times. The output resistance of the amp should be reduced by the same factor, to (308 ohms / 3.16), or 97.5 ohms.
It should be noted that there are plenty of valve guitar amps that use no negative feedback whatsoever around the output stage, so for those, the estimated output impedance is in the ballpark of 300 ohms.
Every factor in these calculations is approximate, so I just quoted the ballpark figure, i.e. 100 ohms output resistance.
I've never sat down and measured this, so if I somehow made a huge error in my estimate, please feel free to correct, and educate, me!
-Gnobuddy
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