Musically subwoofer?

[Dr.db]

If I´d use the W15gti e.g. the 2256g, 3cubic feet is almost close to Q= 7 in a sealed enclosure. Would there be a benefit in building a larger, sealed enclosure for these drivers?

I will locate the mono-sub very close to the mains, so locating-issues aren´t that dramatic.
I would propably use a lowpass at 80-100hz due to two facts:
- My main speakers (using E-145) start to roll-off gently at ~100hz
- every Filter creates some kind of group-delay and it gets worse the lower the filter is set

A 80hz lowpass-filter generates less group-delay than a 50hz lowpass-filter, resulting in a more time coherent system.
(I´m not using a DSP, so no way to set delays on the mains etc...)

[toddalin]

Regardless of whether you can localize the sound or not, if you don't cross it over at at least 80 Hz, you'll loose a least some of the ".1" in a home theater set-up.

[Ruediger]

See the thread named "JBL K140" in the "Lansing product DIY Forum" (which is THIS forum). Look for the patent granted to K.E.Stahl. Look for doctordate, he has done PCBs for such a project.

Basically the effective loudspeaker parameters are modified by electronic means.

Ruediger

[rusty jefferson]

Thanks a lot for your input guys!

The required bandwith would be 25-100hz.
I have to deal with a monosubwoofer, allthough Im aware of the benefit of multiple subs spread in the room.

What enclosure would you recommend for the W15gti if soundquality is the priority?

What enclosure would be appropriate for the Aurasound?

Does the Dayton really keep up with the Aurasound or is it just a cheap alternative with less qualitiy?

Below is a sort of spreadsheet of the 3 drivers we've mentioned. I know the Ultimax woofers are made in China and that's not necessarily great. However, it does appear to be a good sounding, and measuring driver for use as a subwoofer in the home. I don't make any claims about it's potential longevity.

You can see from the chart that if 4 cubic ft is the desired input (the reason I mentioned the Ultimax was your interest in a small 3 cubic foot box), the resonant frequency is considerably lower with the Ultimax meaning less eq and amplifier power.

If the desired input is changed to 30hz resonant frequency, the Ultimax would only need a 5.5 cubic foot box, while the Aurasound would need 9 cubic feet, and the JBL 11 cubic feet.

FS	19.5	20	25.2
QT	0.53	0.47	0.48
VAS	212.1	322	132.2
Input Desired Q
QB=	0.7
Driver	Ultimax 18	Aurasound 18	JBL W15Gti
FS	19.5	20	25.2	0
QB	0.7	0.7	0.7	0.7	0.7
QT	0.53	0.47	0.48	0
FB	25.75	29.79	36.75	#DIV/0!	#VALUE!
VAS	212.1	322	132.2	0
VB (L)	284.93	264.32	117.33	#DIV/0!	#VALUE!
VB (cu ft)	10.06	9.33	4.14	#DIV/0!	#VALUE!
Input Desired Volume
VB (cu ft)=	4
Driver	Ultimax 18	Aurasound 18	JBL W15Gti	0	0
FS	19.5	20	25.2	0
VAS	212.1	322	132.2	0
VB (L)	113.26	113.26	113.26	113.26	113.26
FB	33.05	39.21	37.10	0.00	#VALUE!
QB	0.90	0.92	0.71	#DIV/0!	#VALUE!
Input Desired Resonance
FB=	30
Driver	Ultimax 18	Aurasound 18	JBL W15Gti	0	0
FS	19.5	20	25.2	0
QT	0.53	0.47	0.48	0
VAS	212.1	322	132.2	0
QB	0.82	0.71	0.57	#DIV/0!	#VALUE!
VB (L)	155.17	257.60	316.85	#DIV/0!	#VALUE!
VB (cu ft)	5.480	9.097	11.190	#DIV/0!	#VALUE!

[hsosdrum]

Regardless of whether you can localize the sound or not, if you don't cross it over at at least 80 Hz, you'll loose a least some of the ".1" in a home theater set-up.

I doubt that the .1-channel information (in programs that even contain any .1-channel info) has any content at all above 50Hz – 60Hz. That channel is used for high-energy low-frequency information. Stuff around 80Hz and above would normally not be in the .1 channel, it would be in one of the 5 (or 7) full-range channels).

The primary reasons that THX chose 80Hz as the crossover point for THX home systems were 1) to keep the size of the L/C/R speakers small enough that they wouldn't dominate the room, and 2) because as a rule, humans cannot locate the source of sounds below around 100Hz (the wavelengths are so long — >10 feet — that they reach both ears simultaneously, and our brains rely on inter-ear timing differences to localize the direction a sound is coming from). As with just about everything, it's a compromise, but one that was chosen based as much on psychoacoustics as it was on Spousal Acceptance Factor.

I'm not sure what crossover frequency is used in the THX crossovers installed in THX-certified movie theater sound systems, but considering the size and low-frequency capability of THX-certified behind-screen L/C/R speakers it's no doubt lower than 80Hz. (Plus, localization isn't an issue in movie theaters since the subs are behind the screen along with the L/C/R speakers.)

[toddalin]

You've also got to consider that the theater subs also fill in for the surround speakers, and these don't necessarily have the bandwidth of the L/C/+R.

In fact, the "go to" JBL surround speakers (8330s) are rated from 70 Hz - 14kHz +- 3 dBA.

[Dr.db]

@rusty jefferson: Thanks a lot for your effort you put in the tables!

See the thread named "JBL K140" in the "Lansing product DIY Forum" (which is THIS forum). Look for the patent granted to K.E.Stahl. Look for doctordate, he has done PCBs for such a project.

Basically the effective loudspeaker parameters are modified by electronic means.

Ruediger

I have had a look on this but I believe I´m not familiar enough with all these parameters to really understand it.
http://www.audioheritage.org/vbullet...light=jbl+k140

So far I understood this is no simple EQing, rather it is a manipulation of the drivers parameter with an electronical filter before the amplifier.

One questions comes to mind; how does this affect the drivers output capacities in terms of spl ?

[berga12]

a pro 18" with a Fs around 28-30hz not so heavy, and use a class D (quality ones...) with good amount of power.

I could say 2245h, but I never ear in my life one...

not below 18" for your speakers setup, and not a GTI.......yes tunderstorm but not quick enough. you need Speed to be "glued" to yours E145.

[Dr.db]

I think the maximum enclosure I could deal with would be 8 cubic feet...

So I would either have one Aurasound NS18 or two JBL W15gti.
Can anyone compare the sound of these two
I know that two gti would outperform one Aurasound in spl but which one sounds better with music?




@berga: Have you personally listened to the W15gti ?

[pos]

I had the opportunity to compare the W15GTI and 2245H, and what I found was that at "low" volume/excursion the 2245H produced far less distortion than the W15GTI.
The W15GTI has more excursion and power capabilities (ie higher SPL potential) but when you stay within its limits the 2245H is superior IMHO.
But of course YMMV

[Dr.db]

Thanks a lot for sharing your experience.

What kind of encloshure had been used for the W15gti ?
Which freq. bandwith were they used at ?

[pos]

The enclosure was about 130 or 140L IIRC, I don't remember the tuning frequency.
My distortion tests where conducted in the <50Hz range.
Excursion noises can also be tested without an enclosure.

[Dr.db]

Sealed or vented ?

[pos]

vented

[JuniorJBL]

I use 4 W15GTi's (2 per 10 cu ft) and 2 2242H's (8 cu ft ea) in the theater. They all work very well for this application, however I still prefer my 2245's (8 cu ft per) in my 2 channel room for music. The ultra low distortion is far better with music IMHO. YMMV

I have only heard the others in theaters on movies.