Attached sweeps
1-2: Separate left and right mono woofer only, running full range. Note right woofer is louder due to closer boundaries. They look better separately, but the interaction makes modes affecting the summed FR. Repositioning should help this.
3-4: Left woofer, mic 1/2" from dustcap. With and without 2nd order low pass filter at 150Hz.
1-2: Separate left and right mono woofer only, running full range. Note right woofer is louder due to closer boundaries. They look better separately, but the interaction makes modes affecting the summed FR. Repositioning should help this.
3-4: Left woofer, mic 1/2" from dustcap. With and without 2nd order low pass filter at 150Hz.
Attachments
Although we don't see the whole pic here, it does seem promising to be able to achieve a good result. The non-linearities from the raw response is not bad at all- A few inches here and there and I believe you can achieve an even more linear response prior to EQ-ing.
To be able to detect room modes, you need to study un-smoothed single point measurements.
Since you are into DSP and active crossover, it is also an option to place the woofers different to the mid/tweeter since you cross-over pretty low. E.g. placing the woofers closer to the front wall for optimizing bass response and increase headroom. The mid/tweeters can be placed for minimizing comb filtering effects and optimizing midbass/lower mid response. You need off course to time delay the mid/tweeters accordingly to the woofers. At least you should try it before ditching it.
To be able to detect room modes, you need to study un-smoothed single point measurements.
Since you are into DSP and active crossover, it is also an option to place the woofers different to the mid/tweeter since you cross-over pretty low. E.g. placing the woofers closer to the front wall for optimizing bass response and increase headroom. The mid/tweeters can be placed for minimizing comb filtering effects and optimizing midbass/lower mid response. You need off course to time delay the mid/tweeters accordingly to the woofers. At least you should try it before ditching it.
Last edited:
My (limited) hands-on experience is the same, high-Qtc loudspeaker equalized to low-Qtc don't sound the same as genuine low-Qtc loudspeaker. The same is for low-Qtc loudspeaker equalized to high-Qtc.
Also, to achieve an acoustic-suspension type of box, Qtc should be at least 2 times the driver's Qts. Otherwise, it is an "infinite baffle" box and it doesn't sound the same in spite of the same Qtc (with different driver).
I would be grateful to speaker dave to comment on this.
Last edited:
Having a second look at the LP filtered response. You have used 12dB/oct filter. Try going more brutal on the filter order. You will then eliminate smearing from the woofer in the mid region and increase power handling of the midrange driver. Varying the XO-point with a few Hz step at a time can also have great impact on the audible end-result.
So you think that the blooming, boominess is related to reflections? I'll try moving them around to see if it changes the tone. But honestly I'm not confident that speaker positioning is primarily responsible for the poor tone quality, especially since so many other speakers have had clear bass placed in similar locations.
If it turns out that the position is not the problem, what is my next step?
I read something about speakers with low Q having motors too strong for sealed boxes, because it increases the system resonance. Could this be the reason this driver is misbehaving in the large box?
From here: GlassWolf's Pages
"EBP -
EBP stands for "efficiency bandwidth product", and it's just a helpful calculation, to expand on what Qts tells you with regard to the "what box is it good with?" question.
EBP = Fs / Qes. Simple calculation.
It includes Fs in the equation, because in a sealed box, the subwoofer needs a low Fs in order to play low frequencies.
In a vented box however, you can design the enclosure so that it helps extend the low frequencies farther than a sealed box, so Fs isn't as important for that.
Qes is important because in a vented enclosure, you have higher pressure forces at work - so you need a stronger motor to contend with them. In a sealed box, that stronger motor will drive up the system resonance (a box/sub combination version of Fs), making for bad sealed performance.
The actual EBP number tells you whether it's good in sealed or vented...
EBP at 50 or below, sub is best suited to sealed.
EBP higher than about 80, sub is best suited to vented boxes.
EBP in between, sub is OK in either sealed or vented."
Is this (bold) something?
If it turns out that the position is not the problem, what is my next step?
I read something about speakers with low Q having motors too strong for sealed boxes, because it increases the system resonance. Could this be the reason this driver is misbehaving in the large box?
From here: GlassWolf's Pages
"EBP -
EBP stands for "efficiency bandwidth product", and it's just a helpful calculation, to expand on what Qts tells you with regard to the "what box is it good with?" question.
EBP = Fs / Qes. Simple calculation.
It includes Fs in the equation, because in a sealed box, the subwoofer needs a low Fs in order to play low frequencies.
In a vented box however, you can design the enclosure so that it helps extend the low frequencies farther than a sealed box, so Fs isn't as important for that.
Qes is important because in a vented enclosure, you have higher pressure forces at work - so you need a stronger motor to contend with them. In a sealed box, that stronger motor will drive up the system resonance (a box/sub combination version of Fs), making for bad sealed performance.
The actual EBP number tells you whether it's good in sealed or vented...
EBP at 50 or below, sub is best suited to sealed.
EBP higher than about 80, sub is best suited to vented boxes.
EBP in between, sub is OK in either sealed or vented."
Is this (bold) something?
Hi,
The reality is a 0.3 Qts driver in a 0.5 Qtc sealed box will work
much better vented in the same box, tuned for the best ~ F6.
That is a far better starting point in terms of room matching.
Add notches for the main room modes, analyse room modes.
Eq to deep, clean and even, and then filter subsonics below
the port tuning, which should be pretty low given the above.
rgds, sreten.
The reality is a 0.3 Qts driver in a 0.5 Qtc sealed box will work
much better vented in the same box, tuned for the best ~ F6.
That is a far better starting point in terms of room matching.
Add notches for the main room modes, analyse room modes.
Eq to deep, clean and even, and then filter subsonics below
the port tuning, which should be pretty low given the above.
rgds, sreten.
Oh, a slight OT about OB. Try some slot-loading next time. I feel it helps quite a lot. Plus high-impedance drive, which you might need when you switch to lower Q woofers.
Flat baffle is good for mid-high clarity, but the woofer needs more loading for bass. In fact, we have to give it as much air-coupling as we can -among all other compromises- to get the best result.
-------
Back to the Q problem, I have another experience on 2 wide-rangers. They are in the same size (8") and made by the same manufacturer. They both have paper main cone and whizzer cone. One of them has bigger motor and lower Qts (~ 0.3 IIRC), the other has smaller motor and higher Qts (~ 0.4x). They're measured by WT3.
I use them both on OB, and the one with lower Q sounds much fuller and richer in bass. I was wondering.
Flat baffle is good for mid-high clarity, but the woofer needs more loading for bass. In fact, we have to give it as much air-coupling as we can -among all other compromises- to get the best result.
-------
Back to the Q problem, I have another experience on 2 wide-rangers. They are in the same size (8") and made by the same manufacturer. They both have paper main cone and whizzer cone. One of them has bigger motor and lower Qts (~ 0.3 IIRC), the other has smaller motor and higher Qts (~ 0.4x). They're measured by WT3.
I use them both on OB, and the one with lower Q sounds much fuller and richer in bass. I was wondering.
I recently built a stereo pair of bass cabinets like yours, except with 15" woofers, namely B&C 15CL76, I ported the enclosures during the build but decided on sealed after some experimentation. Enclosure volume is 100 litres. I was on the same quest as you, tight accurate bass. I achieved that with my design. The bass is very articulate and textured. I am using the MiniDSP to take out some very nasty room modes, otherwise my labour would be in vain. The MiniDSP cannot add bass. If I do then it will severely compress the dynamic range of the bass. Tweaking the bass knob up on my preamp a bit does far more than anything achievable in the digital domain(for getting more bass). I was after a driver with a higher BL, that I believe is an important factor.
It sounds like you may be reading the same book as me, Loudspeakers For Music Recording and Reproduction Philip Newell and Keith Holland???
Anyways, one quote I think is relevant...
"Some manufacturers have tried to sacrifice system sensitivity by lowering the magnet flux in order to lower the system Q. There is a strong ‘amplifier power in cheap’ lobby, who believe that lower efficiency systems can exhibit higher Qs, and hence can be extended in their low frequency range. What they often seem to fail to realise is that a heavier current in the voice coil and a lower power magnet will drastically alter the ratio of the fixed magnetic field to the variable magnet field. The much higher variable field due to the voice coil current can severely distort the position of the flux lines of the weak, permanent magnet, and give rise to loss of low level detail in the sound and increased levels of intermodulation distortion. This highlights perhaps one of the worse aspects of the use of programmable calculators or computers in the wrong hands – they can lead to good results on paper, but they can give rise to unpleasant side- effects in practice."
It sounds like you may be reading the same book as me, Loudspeakers For Music Recording and Reproduction Philip Newell and Keith Holland???
Anyways, one quote I think is relevant...
"Some manufacturers have tried to sacrifice system sensitivity by lowering the magnet flux in order to lower the system Q. There is a strong ‘amplifier power in cheap’ lobby, who believe that lower efficiency systems can exhibit higher Qs, and hence can be extended in their low frequency range. What they often seem to fail to realise is that a heavier current in the voice coil and a lower power magnet will drastically alter the ratio of the fixed magnetic field to the variable magnet field. The much higher variable field due to the voice coil current can severely distort the position of the flux lines of the weak, permanent magnet, and give rise to loss of low level detail in the sound and increased levels of intermodulation distortion. This highlights perhaps one of the worse aspects of the use of programmable calculators or computers in the wrong hands – they can lead to good results on paper, but they can give rise to unpleasant side- effects in practice."
Thanks sreten. I can accept it on faith, everything I read is saying it. But I am curious why. Can you explain why low Q driver works better in vented box?
Do you mean tuned for lowest frequency F6 or loudest F6?
What do mean by room matching? You mean louder SPL at low frequency for the larger room volume? Small room couldn't handle that much low bass? I just want to make sure I understand. Thanks
This driver just won't work right in a sealed alignment. My reading narrows down the EBP towards the vented side when EBP passes thru 50.
As we know it is the electrical side of things that really determines control. It's that fancy Moly magnet driving down Qes. That product over sum calculation is just a fancy way of saying, 'since mechanical is so uncontrolled, it's up to you Mr. magnet to keep things in check'.
Now we need compliance in the moving mass...this is not a guitar driver, so mechanical will always be a multiples of electrical.
Since this driver has utter electrical control, we don't need to add a stiffening agent via a sealed box. This just adds unneeded control of the cone. This just starts the curve rolling off way too soon, especially considering the low value of Fs.
_______________________________________________________Rick........
As we know it is the electrical side of things that really determines control. It's that fancy Moly magnet driving down Qes. That product over sum calculation is just a fancy way of saying, 'since mechanical is so uncontrolled, it's up to you Mr. magnet to keep things in check'.
Now we need compliance in the moving mass...this is not a guitar driver, so mechanical will always be a multiples of electrical.
Since this driver has utter electrical control, we don't need to add a stiffening agent via a sealed box. This just adds unneeded control of the cone. This just starts the curve rolling off way too soon, especially considering the low value of Fs.
_______________________________________________________Rick........
In addition to the limited capacity when using sealed enclosures, the additional stroke and power needed to create the same sound pressure level at low frequencies compared to BR do also increase driver distortion. The extent and audibility of this will strongly depend on the quality of the driver used.
I came across recommendations from a few decades back that said:
Low Qts drivers suit vented box loading.
Medium Qts drivers suit sealed box loading.
High Qts drivers suit infinite baffle loading.
I have found this is still promoted and it seems there is quite a bit of overlap between the types of loading.
If I want a vented loading I look for a Qts<0.4
For sealed look for >0.35 and <0.7
For infinite look for >0.6
Is there anything wrong with that advice?
Low Qts drivers suit vented box loading.
Medium Qts drivers suit sealed box loading.
High Qts drivers suit infinite baffle loading.
I have found this is still promoted and it seems there is quite a bit of overlap between the types of loading.
If I want a vented loading I look for a Qts<0.4
For sealed look for >0.35 and <0.7
For infinite look for >0.6
Is there anything wrong with that advice?
Maybe it's derivative ...or integrative
to the fact that : allowing a natural HP for the device
and ambient+ (room gain) contribution, thus allowing
for a discrete Butterworth as a natural for-the-ear reconstruction
(note that the 0.707 is reached easily in closed box/but not everytime it applies to PS as also the compliance of the system driver+ box has to be taken in exam> see GD )
to the fact that : allowing a natural HP for the device
and ambient+ (room gain) contribution, thus allowing
for a discrete Butterworth as a natural for-the-ear reconstruction
(note that the 0.707 is reached easily in closed box/but not everytime it applies to PS as also the compliance of the system driver+ box has to be taken in exam> see GD )
I can't think of any theoretical reason why this would be so.
Certainly for small signal conditions we would have a hard time distinguishing between high Qtc equalized to low or vice versa. The only question would be whether there are some secondary issues that impact large signal conditions.
If we consider the high Qtc equalized to low vs. a "genuinely" low Qtc, say for example we put the same woofer in a large box and a small box and equalized the small box case, what would be different? The compliance would be less with the small box combination and a greater percentage (of stiffness) would come from the cabinet air. Hard to say if that would effect linearity. The air in the box might be more linear than the woofer suspension, but I don't see a big impact from that. The Bl nonlinearity is the greater factor and it is the same for both (and excursion for both is identical after EQ). Watts required for each would be different at different frequencies, but hard to predict an overall impact from that.
With too many of these scenarios people will try one case and then think they hear a difference and then extrapolate a universal truth from that. That's why I would rather see some measurements as corroboration.
Regards,
David
High Q in OB is loose suspension and weak motor to allow cone overshoot that exaggerates bass extension and loudness to avoid the need for bass EQ making simple passive crossovers ideal. The price is loss of detail because neither the suspension nor the motor adequately controls the cone. Eminence Alpha 15 is the OB king, its Qts is 1.26! Low and loud with only a LP filter to your favorite fullrange at 300Hz. Low price makes a DIY dream. But poor detail doesn't blend with lowQ fullrange driver. It has a beautiful flat FR, but the hidden fact is it's all sine waves.
I had this problem with an OB project, I used AE Dipole12 drivers (Qts .7.) They had too little detail. They blended poorly with my Feastrex. Another time I bought used servo OB subs but the servo sensors were broken so it was just high Q drivers in OB with no "electronic suspension." Same warm blurry sound.
That's really the problem I am having. Lack of detail, poor transient response. I have loose suspension just like OB speaker. I have high acoustic compliance similar to OB speaker. But I have a strong motor instead of a weak motor. Why is the strong motor causing worse transient response? Or maybe it's the high compliance not the strong motor that's the problem.
Madisound says my driver in sealed box should be only 19 liters, that's Qtc .88! Would the stiffer air spring make better transient response? A reflex port resists the cone motion too.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.