QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

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AcousticScience
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QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#1 Post by AcousticScience »

Fs 32.4 Hz
Re 3.67 Ohm
Qts 0.437
Vas 31.8161 litres
Xmax +/- 9mm, though the cone can move quite a bit further in the non-linear range (15mm+)
250 watt continuous/750 peak

I snagged it off Ebay for £22 as old stock to mount in a back pack so I could "feel the bass" when listening to headphones (I got a bit carried away and blew the SPLX SPL10R I had). So far tested on metal music, powered off a Peavey IPR1600, the kick drum causes my teeth to chatter!

But realised it had compatible Thiele/small parameters with some of the Tuba cabs on this site, so anyone looking for a budget woofer along with JBL/Infinity etc might be interested.
I've got an Autotuba at my mum's house somewhere for an 8 - might need an adapter. I'm thinking this woofer or 2 will blow the doors off in a Table Tuba.

It even has light up LEDs built into the cone! Well that won't be much use in the horns unless someone builds a T39 with acrylic front :P
I posted it here as it is likely more compatible with the home audio stuff than the Pro Sound Tubas/Titans

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Seth
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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#2 Post by Seth »

Have you heard of SubPac? I bought one a couple years ago and it was absolutely great!.. Except, the coil in the tactile transducer melted in less than a week... returned it for a refund. They need to integrate some sort of thermal limiting before I buy another.

Here's some guys using it along with IEM's

Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

AcousticScience
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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#3 Post by AcousticScience »

Truth is the SubPac is what inspired me. But because they cost £300 I wanted to see if there was a way to manufacture a cheaper one from stuff I had laying around the house. The answer is yes, and mine is a high powered version with a 250 watt continuous 750 watt peak 10" woofer. Though I did blow up an SPLX SPL10R by pushing it too hard with the Peavey IPR1600. Thankfully I didn't pay huge money for it. I had a JBL GTO1264 driver in it for a while but it barely fit in the bag and was heavy, before getting the QX Aero 10. I haven't tested the LED lights on then yet I'm not sure whether you connect them to the amplifier or run a low DC voltage to them (I don't want to blow the bulbs on the amplifier even though I'm not likely using them and they are a bit of a gimmick).

Truth is it's hard to set power limits for speakers, precisely because program material varies so much.
Program.png
Both these types of music have the same peak limit, but you can see the second type will heat up your woofers much faster. Peak limit is useful for overexcursion, but it will leave performance on the table if it is set low enough for the speaker to pass a sine wave for 16 hours without burning up.

When looking at the spec it also seems it would make a mean Table Tuba woofer, but because there are too many big wooden boxes in my life I'm holding off on any more builds. I have thought about an isolation box that I sit inside and can seal (perhaps a long ventilation tube or two to get fresh air inside). Perhaps a Tall Autotuba for those wanting to see the woofer (if you put an acrylic window in front of the driver like those old bandpass boxes in budget car audio stores.

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#4 Post by Grant Bunter »

AcousticScience wrote: Fri Jun 05, 2020 7:19 am the same peak limit, but you can see the second type will heat up your woofers much faster. Peak limit is useful for overexcursion, but it will leave performance on the table if it is set low enough for the speaker to pass a sine wave for 16 hours without burning up.
What is a peak limit?
Why are you suggesting it's ok to take drivers to over excursion?
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#5 Post by AcousticScience »

Overexcursion can always damage a driver, whereas temporarily exceeding thermal won't.
If you have a song with a kick 10% of the time and you supply 500 watts to the subwoofer with a 250 watt thermal rating, the average power is 50 watts. If you'd limit to 250 watt thermal you'd only average 25 watts to the subwoofer, though it's safe of course.
If you knock over your bass guitar near the subwoofer and the string starts ringing at full feedback for a long time, then you have an average power closer to 500 which may overheat the subwoofer. It was Ivan Beaver of Danley Sound labs that suggests a peak stop limiter set at program AND a lower value thermal limiter set about half of RMS (whatever voltage this is as you can't set to watts obviously).

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#6 Post by Seth »

AcousticScience wrote: Wed Oct 14, 2020 4:16 am Overexcursion can always damage a driver, whereas temporarily exceeding thermal won't.
If you have a song with a kick 10% of the time and you supply 500 watts to the subwoofer with a 250 watt thermal rating, the average power is 50 watts. If you'd limit to 250 watt thermal you'd only average 25 watts to the subwoofer, though it's safe of course.
If you knock over your bass guitar near the subwoofer and the string starts ringing at full feedback for a long time, then you have an average power closer to 500 which may overheat the subwoofer. It was Ivan Beaver of Danley Sound labs that suggests a peak stop limiter set at program AND a lower value thermal limiter set about half of RMS (whatever voltage this is as you can't set to watts obviously).
Tim! Welcome back. Haven't seen you around these parts in some time.

From a thermal standpoint, I agree with what you've said. However, within the realm of displacement limiting subwoofers, I'm pretty sure the point is to maintain an effective relationship between the magnet and coil's magnetic field. Where pushing the driver beyond Xmax, yet not quite to Xlim, the coil leaves the magnetic field of the magnet causing the impedance to drop off and more energy is converted into heat as well as reducing the mechanical control the coil has over the movement of the cone.

That's my understanding of it anyway. May not be 100% accurate.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#7 Post by Grant Bunter »

AcousticScience wrote: Wed Oct 14, 2020 4:16 am Overexcursion can always damage a driver, whereas temporarily exceeding thermal won't.
If you have a song with a kick 10% of the time and you supply 500 watts to the subwoofer with a 250 watt thermal rating, the average power is 50 watts. If you'd limit to 250 watt thermal you'd only average 25 watts to the subwoofer, though it's safe of course.
If you knock over your bass guitar near the subwoofer and the string starts ringing at full feedback for a long time, then you have an average power closer to 500 which may overheat the subwoofer. It was Ivan Beaver of Danley Sound labs that suggests a peak stop limiter set at program AND a lower value thermal limiter set about half of RMS (whatever voltage this is as you can't set to watts obviously).
This didn't answer my question. What's a peak limit?

As for the response, how does it apply to BFM? Certain drivers (Lab12 springs to mind) in many of Bill's designs reach Xmax and their thermal limit at the same voltage displacement limit, so if you exceed thermal, even briefly, you exceed Xmax as well.
Even with voltage displacement limiting, if you keep on constantly tickling the limiter you can make the driver burn out the VC.

Kick is not 10% of most songs. With the simplest beat, in 4/4 there are 2 kicks to the bar. That means kick is 50% of that song, in the drum track alone.
However, the greatest excursion isn't caused by kick at 50-70Hz, it's more likely to be a bass line playing in the key of E (if the driver/and or enclosure is capable of reproducing it) that produces the most excursion nearer to Fs.

I'm sure Ivan knows his stuff. Was it your words or his that says suggests?
To me, describing a dual limiter system (how does one even achieve that?) attributes human characteristics to a piece of electronics.
eg: "Oh this stretch of material will produce a strong thermal response, I best use the thermal limit. Now this piece doesn't have that thermal issue, so I can use the programme material limit."
Nonsense. A limit is a limit. And the limiter will engage the limit, every time (one hopes), at whichever is the lowest voltage limit set in the limiter, because that's it's only job...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#8 Post by Bill Fitzmaurice »

Using thermal driver ratings to set limiters is fine when the thermal limits are equal to or lower than the mechanical limits. That's usually the case with mains. With subs the mechanical ratings tend to be equal to or lower than the thermal ratings, so the mechanical ratings are what should be used to set limiters.

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#9 Post by Seth »

Grant Bunter wrote: Wed Oct 14, 2020 4:23 pm Kick is not 10% of most songs. With the simplest beat, in 4/4 there are 2 kicks to the bar.
Pretty sure the meat and potatos of a kick drum signal is about 100-200ms per beat. Not sure what that would math out to be over time though. 100bpm... would that be 10-20 seconds out of a minute, or 16-32%?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#10 Post by AcousticScience »

I was just saying mechanical limits tend to be of a nature where you exceed it once and you're done (usually if a coil hits a back plate it's permanently dented). Thermal limits tend to be "you can temporarily exceed, but the voice coil will need to cool" e.g. like a toaster that says "not for commercial use" meaning if you toast slice after slice after slice of bread, it will overheat. Or in the case of a speaker; the coil insulation browns and smokes, the voice coil glue starts to melt and the wire pulls off the coil and makes a nice little rat's nest in the magnetic gap.

It was Ivan Beaver's words that he recommended a dual limiter. A mechanical brick wall limiter with an attack and release time as short as possible set maybe at xmax, but lower than xlim wherever in the pass band is highest. To answer Grant for a speaker tuned to 40Hz, whether a bass reflex or a quarter wave horn, excursion will be lower here and rise above this frequency peaking maybe 50-60 Hz and lowering again, and rise below but the high pass filter will catch it).
A thermal limiter with an attack time depending on driver (I can't remember exact times he said, maybe attack times of 3 seconds for subs, 1-2 for midrange and 0.5 for tweeters as a ballpark guess) set at half the continuous rating or 1/4 of the program rating, (using volts 1/sqrt 2 and 1/2 respectively)

I've seen this multiple times on prosoundweb. I'm not sure if this dual limiter can be fooled by repeated signals above thermal limit but just below the attack time followed by a brief silence, but it should catch the vast majority of program material from slap bass and mic drops to DJs with extended bass note woofer workouts.

Of course if mechanical ratings are lower or the same (depending on frequency, the thermal limit will be lowest at tuning, mechanical at peak pass band excursion) then a single fast limiter will suffice and the thermal limiter is redundant.

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#11 Post by Bill Fitzmaurice »

There's a very good reason why you don't see most sources refer to the voltage at which the mechanical limit is reached: they don't know what it is. Consider that before accepting their word as gospel.

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#12 Post by Grant Bunter »

SethRocksYou wrote: Wed Oct 14, 2020 6:15 pm
Grant Bunter wrote: Wed Oct 14, 2020 4:23 pm Kick is not 10% of most songs. With the simplest beat, in 4/4 there are 2 kicks to the bar.
Pretty sure the meat and potatos of a kick drum signal is about 100-200ms per beat. Not sure what that would math out to be over time though. 100bpm... would that be 10-20 seconds out of a minute, or 16-32%?
It isn't really about duration, but the amplitude.

Does this mean you agree with me, or with the OP?
16-32 isn't 10 right?
Standard dance tempo is 128 bpm. That would be the old school square dance style meter (and a number of other styles too), and there's a bunch of songs, that are well in excess of 128 BPM, and many of those are in cut time, or 2/4.

The OP's initial "graphs" aren't about frequency per se, as there's no reference on the chart provided. So it's about amplitude, excursion, and a made up terminology, and consequently, essentially those charts are useless, but are merely provided as a wheelbarrow by the OP.
To suggest that maximum excursion doesn't occur at Fs is somewhat incredible, and certainly ignores response graphs from every decent speaker manufacturer in the world (even if it's not at Fs, it's near Fs where excursion is rising in amplitude towards Fs, and greater in amplitude than kick at Fs and lowering).

Next up, the "mechanical" limiter. WTF is that? An axe?
All limiters are simply electronic signal modifiers. Put in to much on the input, will lead to clamp that at the output so you don't blow your driver.
Limiters aren't HAL...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#13 Post by Bill Fitzmaurice »

Excursion at Fs is moot. Fs is free air resonance. It's measured with the driver literally dangling in the air. In that configuration Z is at a maximum at Fs, which results in excursion being at a minimum, but we don't use drivers suspended in the air, so it doesn't have a whit of relevance where limiting is concerned.

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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#14 Post by Seth »

Grant Bunter wrote: Thu Oct 15, 2020 4:24 am
It isn't really about duration, but the amplitude.
G'day mate.

I think the point he's making is both. Amplitude over time is essentially RMS.
Does this mean you agree with me, or with the OP?
16-32 isn't 10 right?
Standard dance tempo is 128 bpm. That would be the old school square dance style meter (and a number of other styles too), and there's a bunch of songs, that are well in excess of 128 BPM, and many of those are in cut time, or 2/4.
I'm not taking any sides on this one. But, yes, I agree it's not 10%. However, I'm pretty sure Tim loosely tossed out 10% to exemplify the point he's making, which I think is valid, even if it's only for discussion value.
The OP's initial "graphs" aren't about frequency per se, as there's no reference on the chart provided. So it's about amplitude, excursion, and a made up terminology, and consequently, essentially those charts are useless, but are merely provided as a wheelbarrow by the OP.
I took the charts to represent power over time in regards to thermal management, not necessarily about cone travel.
To suggest that maximum excursion doesn't occur at Fs is somewhat incredible, and certainly ignores response graphs from every decent speaker manufacturer in the world (even if it's not at Fs, it's near Fs where excursion is rising in amplitude towards Fs, and greater in amplitude than kick at Fs and lowering).
I'm not 100% positive about this, but I'm of the understanding that the lower the frequency the greater the excursion need be to maintain any given output level. I'm also fairly certain the excursion of a driver in a horn loaded sub greatly increases at frequencies below it's 1/4 wave frequency, or below the tuning frequency of a ported enclosure... hence the need for a high pass filter.
Next up, the "mechanical" limiter. WTF is that? An axe?
All limiters are simply electronic signal modifiers. Put in to much on the input, will lead to clamp that at the output so you don't blow your driver.
Limiters aren't HAL...
No no... a mechanical limiter... it's a little bridge over the cone with an adjustable rubber door stop to limit cone travel! Hahaha

Seriously though, I think this may boil down to regional terminology. We're all from different corners of this planet. I assume he's talking about limiting the (mechanical) excursion with a brick wall limiter. But, to your point, are you aware of RMS limiters and how they differ from a brick wall limiter? You've contributed a great deal to many aspects of my learning things here over the years, so I assume you do. But, maybe you don't? I didn't always know what I know now. We're all human. I've never used the RMS limiter feature, but I've been curious about it's value and practical use. So, I found what Tim had to say in the matter rather interesting.

Obviously, it's not a thing for all applications and not specifically related to displacement limiting, but more of a thermal management plan... I think. To which, I thought you had a good point/question... how does it translate into BFD land?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

AcousticScience
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Re: QX Aero 10, New high performance Table/Auto/Truck Tuba woofer?

#15 Post by AcousticScience »

Bill Fitzmaurice wrote: Thu Oct 15, 2020 6:50 am Excursion at Fs is moot. Fs is free air resonance. It's measured with the driver literally dangling in the air. In that configuration Z is at a maximum at Fs, which results in excursion being at a minimum, but we don't use drivers suspended in the air, so it doesn't have a whit of relevance where limiting is concerned.
Why I don't tend to factor it much. Maximum and minimum excursion is based mostly on cabinet design and how it interacts with the driver's thiele small parameters - at least for bass cabinets and woofers and generally the bottom portion of the audio spectrum. For a vented box, the helmholtz resonance will usually have a minimum (and at the resonant frequency of a horn, there will also be a minimum, although probably slightly less pronounced than it is for a vented box.) The maximum displacement of a vented box will be somewhere in the middle of the pass band, probably close to what that speaker would do in a sealed box of half the size if the ports are resonating in unison. The Fs of the speaker will come into it somewhat. How much this dominates will be related to the size of the box, area of the cone, stiffness of the suspension, moving mass. I would assume it's at the point the port air is in phase with the speaker, but I am unsure as to exactly how to calculate this point, as different speakers in the same box will have a different displacement peak at a different frequency.

As a horn mouth or group of horns gets larger, the displacement and impedance curves will become flatter, though it would be rare for them to be ruler flat. As a general rule, when the acoustic resistance on the speaker is higher, its impedance will be lower and vice versa.

To answer Grant's points about kick duration, it depends how staccato the kick is. In EDM, there is a trend to attach bassline to the kick, whereas in rock music it's more likely to be a quick thump and gone. So I'm talking about what proportion of the music the main thump actually lasts. In a classic rock song with a kick every other beat - maybe one of the verses to Bye Bye Beautiful by Nightwish, this might not be much time at all. In a song that's mostly bass - like The Tunnel by Jay Cosmic, your subwoofers are almost continuously on.
The following three will heat the speaker the same on average. A continuous sine wave at thermal limit, a half second pulse at double the thermal limit followed by half a second of silence, a third of a second at 3 x the thermal limit followed by 2/3 of a second of silence.
There are limits to this. Don't expect to drive your speakers hard for a minute or longer, then rest 2 minutes - but within the realm of music tempos, the thermal inertia of the coil at least on a low frequency loudspeaker should be able to average the peaks and troughs. Obviously for tweeters, the coil is smaller and heats up more easily.

Mechanical limit doesn't work the same way. Trying to do twice the mechanical limit and then making up for it with a rest period will still damage the speaker. However, technically Xmax is not the mechanical limit, just the point at which the loudspeaker is no longer linear - whether due to suspension becoming stiffer or the voice coil not being all in the gap. (Technically with an overhung coil it's never all in the gap but a consistent length portion of it is throughout Xmax) You might notice some harmonic noise added to your clean bass notes. The real mechanical limit is a second number called Xlim or Xdamage - the total range of the suspension or coil in the gap. Note I don't recommend limiting to Xdamage as there is no margin or error whatsoever.

When I say mechanical limiter, I mean a restriction on the maximum voltage you can apply to a speaker sweeping through its pass band at which the cone won't move too much. I can usually get a ballpark figure from Hornresp graphs.
When I say thermal limiter, I mean a restriction on the maximum voltage you can apply at the speaker's minimum pass band impedance that the speaker coil can play for prolonged periods without overheating.

Thermal limit is usually "don't remain above this zone, though short duration signals can temporarily exceed it as long as there is adequate rest period"
Mechanical limit is "NEVER exceed this under any circumstances unless you like reconing speakers."

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