NEW PURIFI 8'' MWoofer [PTT8.0X04]

[voodooless]

Or multiple times as cheap;

W.46.1300.8.MC

Głośnik niskotonowy / subbasowy Średnica - 465 mm Moc - 1300 W Impedancja - 8 Ω Efektywność - 98 dB Fs - 36 Hz Qts - 0,32 Vas - 164 L Materiał membrany - celuloza mody

stx.pl

(the 15 inch W.38.800.4.MC seems actually VERY interesting as well for that price bracket! )

It only has half the Xmax though. The ipal does 20mm one way. Induction is also very high, so probably no demodulation rings. I’m pretty sure distortion will be worlds apart. But at 140 euro it’s crazy cheap!

 

[sarumbear]

I don't have idea, because I don't have experience. His OB have 8x 18 inch AE Dipol and 8x 12 inch AE Dipol. If I good remember these OB have 14Hz with -3 or -6dB.

I wasn’t commenting on a particular OB. I was pointing out the fact that the chart fits a Q=~0.3 driver’s response and this driver’s Qt is 0.34.

 

[OWC]

It only has half the Xmax though. The ipal does 20mm one way. Induction is also very high, so probably no demodulation rings. I’m pretty sure distortion will be worlds apart. But at 140 euro it’s crazy cheap!

Demodulation rings don't have that much benefits anymore for lower frequencies.
Below 200Hz or so, or better, below the minimum of the dip after the resonance frequency in the impedance.

Yes the ipal has much much more excursion, but how quickly do you want you ears to start bleeding again?
Besides, with 6-8 of those I beat that 20mm with ease!

Btw, those 20mm are "sound-reinforcement excursion millimeters" , equal "hifi millimeters" it's 16mm.

 

[sarumbear]

You spend all your cash on your Kef wall.. so priorities I guess… It’s cheaper than the equivalent number of Purifies though, isn’t it. On the other hand, so many subs distributed in a room will probably give you very smooth low end response.

I can assure you KEFs are not even the largest expense in the system.

However, comparing 8” mid-woofers to full-range dual concentric speakers makes no sense whatsoever.

I’m out.

 

[abdo123]

The signal to noise ratio of this thread just dropped dramatically it seems.

 

[OWC]

The signal to noise ratio of this thread just dropped dramatically it seems.

As we can see, the performance is only as good as the surrounding noise

 

[DSJR]

Any comments on the response taking off in the mid kHz region?

 

[abdo123]

Any comments on the response taking off in the mid kHz region?

It's typical of a diaphragm of this size, infact much better than 99% of 8-inch woofers out there.

 

[abdo123]

This is thing is a beast, even with a modest enclosure full-range speaker is possible

 

[OWC]

It's typical of a diaphragm of this size, infact much better than 99% of 8-inch woofers out there.

The question is how important that is?

With a 8 inch woofer, you want to cross typically around 1200-1800Hz (or lower) minimum to get the directivity right.
What is important is the cone break-up, since this folds back in the harmonic distortion as well (look at the 3rd harmonic, to unfortunate they don't show the 4th and 5th).
Having this breakup around 5-6kHz isn't very unique.

I would never want a full-range speaker, especially not a BR.
But if that is your preference it's a very good speaker, but that was something we were already expecting.

 

[abdo123]

The question is how important that is?

With a 8 inch woofer, you want to cross typically around 1200-1800Hz (or lower) minimum to get the directivity right.
What is important is the cone break-up, since this folds back in the harmonic distortion as well (look at the 3rd harmonic, to unfortunate they don't show the 4th and 5th).
Having this breakup around 5-6kHz isn't very unique.

I would never want a full-range speaker, especially not a BR.
But if that is your preference it's a very good speaker, but that was something we were already expecting.

you're not thinking about this right, a full range speaker works perfectly in a multi-sub setup as you would have one extra subwoofer for free to reduce the seat to seat variation.

 

[OWC]

you're not thinking about this right, a full range speaker works perfectly in a multi-sub setup as you would have one extra subwoofer for free to reduce the seat to seat variation.

That's not gonna work since ideally you want to have all freedom in sense of delay setting per subwoofer.
In case of a fullrange system that's not possible because that will also change the crossover with the tweeter.
A multi-sub system doesn't magically "just work" by adding subswoofers, you also need to active filter and delay those subwoofers.
Delaying just only the back subwoofer(s) could work, but it will always be a limitation in the whole system.

Btw, I don't find 40-50 liter a small system.
Might as well chuck a 10 or 12 inch on the side to do the same thing.
In a small enclosure we will run into a overly large BR port, so PR will be the only other solution in that case.

 

[OWC]

It's a little hard to compare, but it seems that a Wavecor SW223BD02 will perform very similar.

Test Bench - Wavecor SW223BD02 8.75” Subwoofer

In this Test Bench, Vance Dickason measures the SW223BD02 8.75” subwoofer from Wavecor, part of the brand’s rather extensive line of subwoofers. Wavecor’s SW223BD02, which is the 4-Ω version (SW223BD03 is 8 ohm), was designed specifically for high performance compact subwoofer applications and...

audioxpress.com

 

[ernestcarl]

That's not gonna work since ideally you want to have all freedom in sense of delay setting per subwoofer.
In case of a fullrange system that's not possible because that will also change the crossover with the tweeter.
A multi-sub system doesn't magically "just work" by adding subswoofers, you also need to active filter and delay those subwoofers.
Delaying just only the back subwoofer(s) could work, but it will always be a limitation in the whole system.

Basically, it is believed that the ears are incapable of discriminating independent arrivals of waves in the modal region. So it isn't terrribly important that the timing is as exacting as seen in the higher frequencies. The goal of the multiple bass sources in small rooms is to increase the density, distribution and interaction of modes.

 

[OWC]

Basically, it is believed that the ears are incapable of discriminating independent arrivals of waves in the modal region. So it isn't terrribly important that the timing is as exacting as seen in the higher frequencies. The goal of the multiple bass sources in small rooms is to increase the density, distribution and interaction of modes.

This doesn't have anything to do with the audibility of arrivals of waves.
Adding a delay to a subwoofer has the same effect as moving it in space.
Therefor the room modes will (and must) change.

So in fact it is very important to have a good mix between positioning as well as using the right delays per subwoofer.
Even more so when the listening position as well as the placement of the subwoofers is less optimal because of practical constraints.

As far as I know this can even be read in Toole's book, but there are plenty of other resources out there.
One of the things a DIRAC system also does for example.

Or a (VERY) good DIY solution;

Multi-Sub Optimizer Freeware for Multiple Subwoofers

Optimize bass performance of multiple-subwoofer audio systems. Reduce seat-to-seat frequency response variations.

www.andyc.diy-audio-engineering.org

 

[ernestcarl]

So in fact it is very important to have a good mix between positioning as well as using the right delays per subwoofer.

Nobody is saying timing and response filtering for each source should not be adjusted, nor that positioning isn't important at all -- only that the exact time-alignment in the modal region is not as important if the goal is smoother bass response (in the modal region) across multiple seats using multiple bass sources.

 

[OWC]

Nobody is saying timing and response filtering for each source should not be adjusted, nor that positioning isn't important at all -- only that the exact time-alignment in the modal region is not as important if the goal is smoother bass response (in the modal region) across multiple seats using multiple bass sources.

I was very much under the impression that it was just being said a minute ago?

Anyway, that doesn't matter.

Most import point is; to get all freedom and least amount of compromises to attack those pesky room modes, you want full control over your sub region, aka the region below the Schroeder frequency. A full-range system is not gonna give you that full freedom.
Multiple separate subwoofers with individual DSP control will give you heaps more freedom.

fyi, this is a general approach, there are always individual and anecdotal situations were people can get by obviously.
Often they were more just lucky than that it was a well calculated effort.

 

[abdo123]

Often they were more just lucky than that it was a well calculated effort.

This discussion would be more constructive if you actually attempted to comprehend what we're trying to say instead of just brushing it off because it's not something that you would do.

 

[thulle]

You will be surprised to find out that for many famous 188” drivers it’s the opposite. It is not easy to move a large piston without breaking up.

Not at all, but why would I use one of those for a subwoofer where I want the Xmax?

 

[OWC]

This discussion would be more constructive if you actually attempted to comprehend what we're trying to say instead of just brushing it off because it's not something that you would do.

My apologies, but I don't understand what you're asking for or even referring to, so maybe you can explain it differently?

I think I explained very well, why a fullrange system doesn't fit "perfectly" in a mutlisub setup, I don't see how that is not constructive?