What's the difference between a true SPL sub and a true SQ sub?

[spark plugs. 10+ year member]

what characteristics should you look for physically AND in the T/S parameters?

i've tried to compare my BL and my IDMAX's t/s specs. and the only major diff. that really stood out to me was that the IDMAX had a significantly lower fs....but when i look at other subs that are supposedly really good sq (like the mag d2), i notice that the IDMAX has a fs that isn't really all that common.

so what's really the difference?

Click to read more...

 

[Electrodynamic 10+ year member]

There are many different ideologies in respect to what makes a SQ or SPL sub. There have even been companies that have experimented with different parameters (one in particular made a sub with a low Fs as a goal because they peak higher in enclosure simulation programs) trying to come up with what exactly defines an SQ and a SPL sub. For demonstration purposes, lets explore the different ideologies of an SPL sub:

High BL = SPL sub. This can be true. Higher BL means the motor has more force and control over the moving assembly at a certain point (there are high BL subs that have a very non-linear BL curve so the BL is focused within a few mm of travel and beyond that range the BL drops drastically). The main goal is to have enough BL to reach full excursion at a given frequency with a given amount of power. But high BL doesn't mean it will get louder instantly compared to lower BL subwoofers (take the older Brahma's - Scotty Johnson used them and whipped arse...BL was ~14 I believe).

A lot of the time higher BL subwoofers have lower Qts's, which lend them to like ported enclosures (once again, more SPL oriented). However, this doesn't mean that they can't sound good in the proper alignment (enclosure type and size).

Low Fs, high Qts = SQ sub. Not necessarily always, but can be true in some instances. Low Fs subwoofers can be coined as sealed-box woofers, which can be true dependent upon other T/S's. Same goes for High Qts. High Qts's vs low Qts's can tilt the tables significantly either way. A lot of the time lower Qts drivers are more driven towards ported enclosures (as stated above) so they're louder than their sealed counterparts (3 dB gain when porting). Hence the "SPL" label.

It's all about the goal of the subwoofer though. Target enclosure volumes with a target F3 in those specified volumes and power handling are the three biggies when designing a subwoofer. There are a lot of other factors too (I am very anal - yes I said anal //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif - about soft part selection and how it affects the overall sound of the woofer along with how the motor is designed for linearity, BL, size, etc).

But anyway...instead of de-railing massively, which I've just done, if you have two woofers: woofer A has a BL of 30 and a Qts of .19 with an Fs of 35 Hz and woofer B has a BL of 19 and a Qts of .40 with an Fs of 28 Hz, woofer A will be your SPL option and woofer B will be your SQ option. But keep in mind that was a HUGE generalization. HUGE generalization.

 

[spark plugs. 10+ year member]

There are many different ideologies in respect to what makes a SQ or SPL sub. There have even been companies that have experimented with different parameters (one in particular made a sub with a low Fs as a goal because they peak higher in enclosure simulation programs) trying to come up with what exactly defines an SQ and a SPL sub. For demonstration purposes, lets explore the different ideologies of an SPL sub:
High BL = SPL sub. This can be true. Higher BL means the motor has more force and control over the moving assembly at a certain point (there are high BL subs that have a very non-linear BL curve so the BL is focused within a few mm of travel and beyond that range the BL drops drastically). The main goal is to have enough BL to reach full excursion at a given frequency with a given amount of power. But high BL doesn't mean it will get louder instantly compared to lower BL subwoofers (take the older Brahma's - Scotty Johnson used them and whipped arse...BL was ~14 I believe).

A lot of the time higher BL subwoofers have lower Qts's, which lend them to like ported enclosures (once again, more SPL oriented). However, this doesn't mean that they can't sound good in the proper alignment (enclosure type and size).

Low Fs, high Qts = SQ sub. Not necessarily always, but can be true in some instances. Low Fs subwoofers can be coined as sealed-box woofers, which can be true dependent upon other T/S's. Same goes for High Qts. High Qts's vs low Qts's can tilt the tables significantly either way. A lot of the time lower Qts drivers are more driven towards ported enclosures (as stated above) so they're louder than their sealed counterparts (3 dB gain when porting). Hence the "SPL" label.

It's all about the goal of the subwoofer though. Target enclosure volumes with a target F3 in those specified volumes and power handling are the three biggies when designing a subwoofer. There are a lot of other factors too (I am very anal - yes I said anal //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif - about soft part selection and how it affects the overall sound of the woofer along with how the motor is designed for linearity, BL, size, etc).

But anyway...instead of de-railing massively, which I've just done, if you have two woofers: woofer A has a BL of 30 and a Qts of .19 with an Fs of 35 Hz and woofer B has a BL of 19 and a Qts of .40 with an Fs of 28 Hz, woofer A will be your SPL option and woofer B will be your SQ option. But keep in mind that was a HUGE generalization. HUGE generalization.

****...that was awesome. thanks. //content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gif

 

[BringDaBoom 10+ year member]

There are many different ideologies in respect to what makes a SQ or SPL sub. There have even been companies that have experimented with different parameters (one in particular made a sub with a low Fs as a goal because they peak higher in enclosure simulation programs) trying to come up with what exactly defines an SQ and a SPL sub. For demonstration purposes, lets explore the different ideologies of an SPL sub:
High BL = SPL sub. This can be true. Higher BL means the motor has more force and control over the moving assembly at a certain point (there are high BL subs that have a very non-linear BL curve so the BL is focused within a few mm of travel and beyond that range the BL drops drastically). The main goal is to have enough BL to reach full excursion at a given frequency with a given amount of power. But high BL doesn't mean it will get louder instantly compared to lower BL subwoofers (take the older Brahma's - Scotty Johnson used them and whipped arse...BL was ~14 I believe).

A lot of the time higher BL subwoofers have lower Qts's, which lend them to like ported enclosures (once again, more SPL oriented). However, this doesn't mean that they can't sound good in the proper alignment (enclosure type and size).

Low Fs, high Qts = SQ sub. Not necessarily always, but can be true in some instances. Low Fs subwoofers can be coined as sealed-box woofers, which can be true dependent upon other T/S's. Same goes for High Qts. High Qts's vs low Qts's can tilt the tables significantly either way. A lot of the time lower Qts drivers are more driven towards ported enclosures (as stated above) so they're louder than their sealed counterparts (3 dB gain when porting). Hence the "SPL" label.

It's all about the goal of the subwoofer though. Target enclosure volumes with a target F3 in those specified volumes and power handling are the three biggies when designing a subwoofer. There are a lot of other factors too (I am very anal - yes I said anal //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif - about soft part selection and how it affects the overall sound of the woofer along with how the motor is designed for linearity, BL, size, etc).

But anyway...instead of de-railing massively, which I've just done, if you have two woofers: woofer A has a BL of 30 and a Qts of .19 with an Fs of 35 Hz and woofer B has a BL of 19 and a Qts of .40 with an Fs of 28 Hz, woofer A will be your SPL option and woofer B will be your SQ option. But keep in mind that was a HUGE generalization. HUGE generalization.

Awesome post man. Great explanation.

 

[its_bacon12 10+ year member]

you're lucky to get such a knowledgeable person to post. this is the type of discussion that should be on these kinds of forums and is very present at DIYMA

 

[audioholic 5,000+ posts]

There are many different ideologies in respect to what makes a SQ or SPL sub. There have even been companies that have experimented with different parameters (one in particular made a sub with a low Fs as a goal because they peak higher in enclosure simulation programs) trying to come up with what exactly defines an SQ and a SPL sub. For demonstration purposes, lets explore the different ideologies of an SPL sub:
High BL = SPL sub. This can be true. Higher BL means the motor has more force and control over the moving assembly at a certain point (there are high BL subs that have a very non-linear BL curve so the BL is focused within a few mm of travel and beyond that range the BL drops drastically). The main goal is to have enough BL to reach full excursion at a given frequency with a given amount of power. But high BL doesn't mean it will get louder instantly compared to lower BL subwoofers (take the older Brahma's - Scotty Johnson used them and whipped arse...BL was ~14 I believe).

A lot of the time higher BL subwoofers have lower Qts's, which lend them to like ported enclosures (once again, more SPL oriented). However, this doesn't mean that they can't sound good in the proper alignment (enclosure type and size).

Low Fs, high Qts = SQ sub. Not necessarily always, but can be true in some instances. Low Fs subwoofers can be coined as sealed-box woofers, which can be true dependent upon other T/S's. Same goes for High Qts. High Qts's vs low Qts's can tilt the tables significantly either way. A lot of the time lower Qts drivers are more driven towards ported enclosures (as stated above) so they're louder than their sealed counterparts (3 dB gain when porting). Hence the "SPL" label.

It's all about the goal of the subwoofer though. Target enclosure volumes with a target F3 in those specified volumes and power handling are the three biggies when designing a subwoofer. There are a lot of other factors too (I am very anal - yes I said anal //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif - about soft part selection and how it affects the overall sound of the woofer along with how the motor is designed for linearity, BL, size, etc).

But anyway...instead of de-railing massively, which I've just done, if you have two woofers: woofer A has a BL of 30 and a Qts of .19 with an Fs of 35 Hz and woofer B has a BL of 19 and a Qts of .40 with an Fs of 28 Hz, woofer A will be your SPL option and woofer B will be your SQ option. But keep in mind that was a HUGE generalization. HUGE generalization.

Ya... what do you know!
//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[bose301s 5,000+ posts]

Nick, you can post here but not give us more info on the new Mag? Come on man, we are dieing here waiting for new info and pics!! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Electrodynamic 10+ year member]

No problem guys. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Info on the Mag's and BM's will be coming when they arrive. Trust me, I'll keep this forum updated. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[spark plugs. 10+ year member]

you're lucky to get such a knowledgeable person to post. this is the type of discussion that should be on these kinds of forums and is very present at DIYMA

seriously, a post like that should get a sticky or something.

 

[vehementSPL 10+ year member]

seriously, a post like that should get a sticky or something.

AGREED

 

[BringDaBoom 10+ year member]

seriously, a post like that should get a sticky or something.

x2. Mods please sticky

 

[jake760 10+ year member]

x2. Mods please sticky

x3 Thankyou

 

[JohnEJanowitz 10+ year member]

what characteristics should you look for physically AND in the T/S parameters?
i've tried to compare my BL and my IDMAX's t/s specs. and the only major diff. that really stood out to me was that the IDMAX had a significantly lower fs....but when i look at other subs that are supposedly really good sq (like the mag d2), i notice that the IDMAX has a fs that isn't really all that common.

so what's really the difference?

In reality you want many of the same things for both an SQ and SPL driver. Just for different reasons. Parameters often aren't that telling in a woofer unless we are looking at everything. Many people look at Fs at Qts only but don't look at anything else. Those don't tell us a whole lot in general. I can make 3 different drivers with different size coils and motors all come out with the same Fs and qts while they are drastically different drivers. Looking at the design goals tells us much more about the woofer.

Whether you are looking for an SPL or SQ woofer you are going to want a linear, symmetrical BL curve. You are going to want good heat transfer and cooling. If you don't have those things, which unfortunately many drivers don't, they probably aren't going to be good for SQ or SPL.

For the SQ option you want the linear BL curve for low distortion. As your BL changes throughout the stroke, or if it is non-symmetrical on the inward and outward stroke, you have a large amount of distortion. Obviously not desireable for SQ applications. In an SPL woofer you want the linear BL curve because you want more force throughout the stroke to excite the resonance in the port, giving you more efficiency and output. More efficiency means less power is wasted as heat. This means less input power to reach the same levels, and less power means less heat. Less heat means less power compression which again means you're getting more output for the amount of power you put in. It's somewhat of a chain reaction.

Heat transfer is also important and often overlooked. As the temperature of your coil rises, so does the resistance. As the resistance rises, your amp needs to put out more power to reach the same output levels. As it is putting out more power, the coil is then also heating up more, requiring more and more input power to get the same levels. This is what's known as power compression. This is bad for both SQ and SPL applications. For SPL, it is obvious. You are losing output. That is why in most cases you hit significantly higher levels on initial runs. As the coil heats up you just can't deliver as much power to it. For SQ, this heating again leads to higher distortion.

That all said, in general an SPL woofer will be used in a vented enclosure where you are expecting the woofer to excite the resonance of the port to create output. You are operating at and around the tuning frequency so the driver doesn't need to travel a long distance. You're more excited about exciting the resonance than moving long distances. You want a very linear stroke, but not a very long stroke. You'll typically want high motor strength and large cone area to do this. Since you aren't moving long distances, huge surrounds are not a benefit. The more cone area you have, the better you can excite the resonance.

John

 

[Boomboy 10+ year member]

Stickayyy

 

[btdickey99 5,000+ posts]

x3 Thankyou

X4