JBL 18 inch up to 300 Hz?

[mefisto]

Hi,

I would like to use a driver between 40 Hz an 300 Hz in a domestic environment. I was thinking about an 18 inch (2241) just to keep the excursion to minimum.

Is someone running such a large driver that high? How does it sound at the higher frequencies (300 Hz) compared to a smaller (15 inch) driver?

Thank you,

M

[Robh3606]

Look at the 4345, uses the 2245 up to 300Hz with no problems at all.

Rob

[rich carnese]

Just to play devils advocate, I believe, for home use, and for the range you specify..if you can find a 2231 (L136). you'll do better. If you can find an earlier alnico magnet model all the better. It can also be used in smaller enclosures (3-5 cu. ft is good) and will yeild reasonably flat response to 40Hz, and will sound better in the upper range. R

[Nightbrace]

Earth narrows down your location .

[Nightbrace]

What about floating on an 11 dimensional membrane?

[moldyoldy]

Generally, a design shouldn't require a cone driver to reproduce frequencies with wavelengths smaller than the cone diameter, so the driver can operate in pistonic mode over its' full bandwidth. For an 18", this is approx. 700Hz, for a 15" it's around 1100Hz.

The main remaining issue is intermodulation distortion, which rears its' head when a driver has to deal with much more than 2 octaves.

Also for consideration is the effect of having an XO point in the midst of the musical fundamental range, but that's an unavoidable issue in multi-way broadband systems.

[Mr. Widget]

I would like to use a driver between 40 Hz an 300 Hz in a domestic environment. I was thinking about an 18 inch (2241) just to keep the excursion to minimum.

I'd recommend the 2245 as it just sounds better to me... and to many others. I wouldn't worry about the excursion thing... unless you are you planning on SPLs of 120dB. If you are, use several of them.

Is there a reason you want to bandwidth limit the system below 40Hz?

Look at the 4345, uses the 2245 up to 300Hz with no problems at all.

Yes and no... I personally think the 4345 would sound even better if the crossover was around 150Hz or even lower. It isn't really possible with that driver compliment and the ~300Hz XO was the best option... it isn't terrible by any stretch, in fact the 4345 is one of my favorite JBL systems, but for ultimate resolution, that massive cone does seem to cloud a small portion of the music just a tad.


Widget

[mefisto]

Thank you all for your answer, although I have some difficulties deciphering Nightbrace's recommendations. ;-) But then again, I am not the smartest guy around.

Dear Mr. Widget,

The bandwidth is dictated at the upper frequency by the horn I will be crossing over to between 250-300Hz. On the lower frequency, in my room, room gain starts at about 60-70 Hz. So I was thinking that the roll-off of the driver will be compensated by the room gain.

If there is a better driver for the intended puurpose, which will assure low distortion and high sensitivity please recommend it to me.

Kindest regards,

M

[hjames]

Thank you all for your answer, although I have some difficulties deciphering Nightbrace's recommendations. ;-) But then again, I am not the smartest guy around.

Nah, NightB was jest diggin' at you for using the oblique "Location: Earth" in the user details you "shared" with us ...

perhaps you'd bless us by a using a more specific point on the ol' globe ...

[Chas]

Actually, I am running 2245's 40-290Hz in my 4345's and it isn't bad at all. I plan to try substituting a pair of Alnico 2235's (easy to plug and play with Speakons, now ) and see if there is any difference.

The only immediate downside is that I end up with a lot of large boxes in the listening room....

[Ian Mackenzie]

We need to know more about the rest of your proposed system.

The problem of goinn up higher than 300hz (within reason) is not so much the driver but the effects of colouration from the interior of the enclosure back through the woofer cone. Larger boxes because of the panel sizes and internal dimensions produce box colouations. The normal use of bracing will help control panel resonance in the bass region and the fill (fibre glass damping) on the walls of the enclosure will absorb a lot of the energy and provide some degree of damping of the woofer at box tuning frequency.

However you should consider boundary layer pressure damping on the walls of the enclosure if you propose to run above 300 hz. Even at 300 hz crossover may help.

Sometime back I experiemented with this and had excellent results using bubble wrap on the walls and styrene pellets on the interior floor of the enclosure.

The 2245H was designed for a response without the need for boundary reinforcement like some of the other JBL 18 inch woofers. The 2241 is a different applciation of driver and its response below 100 hz is supported by wall boundary effects. The 2241 has higher sensitivity in the upper band area above 100hz but does not have the extension of the 2245 in terms of normalised amplitude response.

You may therefore find the placement and effects of room gain are important to obtaining smooth mid bass response .

Consider this alignment from Drew Daniels box calculator for the 2245H which I recommend for home use.

10.15 cuft 3 (net vol), Fb 27.3, Fs 32hz. The response is-.5 db down at 72 hz and -1 db at 46 hz and -3 db at 32 hz.

I have used this design with outstanding results biamped from 250-400 hz using an Audax 210HTO mid cone driver with the wall damping methods discussed above.

Ian

Hi,

I would like to use a driver between 40 Hz an 300 Hz in a domestic environment. I was thinking about an 18 inch (2241) just to keep the excursion to minimum.

Is someone running such a large driver that high? How does it sound at the higher frequencies (300 Hz) compared to a smaller (15 inch) driver?

Thank you,

M

[Thom]

This is not advice on doing this but rather a question to everybody with all the advice. Aren't there several JBL 18's that would be happier at 300 and be more easily acquired and go to 40? He didn't ask for 30. I know there are ones that say that they will. Is this a matter of those who write specs take liberties? I haven't really played with my 18's yet and that is why I'm asking and not giving advice.

[mefisto]

Dear Ian,

thank you for your reply.

Regarding your question about the rest of the system, I have two options. One is Tom Danley's Unity, the other is Steve's compression driver on appropriate horn. Both options sound good even below 300 Hz, so the 300 Hz cross-over point was selected based on reasonable size horn.

I do want to go with a sealed box below; to _me_ it sounds better than a ported design. I understand from Thiele's and Small's work that if one wants high efficiency (to match the horn in my case), this will limit the low end.

As Thom has noted (thank you Thom), I am looking for experience with 18 inch woofers at 300 Hz. If the consensus is, as some have already suggeted, that 15 inch is better there, I will sacrifice the low frequency extension for that.

In fact, if you look at my other thread (Help noob with enclosure aligment please), I have already looked at Altec 515B, and if one can trust the simulator, it can reach 104 dB at 40 Hz. Assuming 3 dB gain from stereo and 20 dB dynamic range, one is at 87 dB average listening level. Since my listening is on average 65 dB, I have another 12 dB overhead.

I understand that the Altec is not the best driver for the lower frequencies, but _I_ just love it for the mids. If however, there is a better driver, I would like to hear it.

Do I make sense or am I deluding myself?

M

[soundboy]

Been playing with this stuff many years, both for live sound, and home....used 2235H's and 2245H's and 2240's, and 2241's off an on for decades....my two cents is that for home "hifi" use, crossing any 18" higher than 80-100hz sounds too colored. The 2235H any higher than about 300 sounds too colored. It all depends on what your goal is....an 18 is an 18, at 300 hz....although the 2240H/ 2241 would sound a bit smoother than a 2245H, IMHO. To me, they are all too colored above 200hz, exept for live sound reinforcement......if you want a PA system in your living room, go for it...if you want uncolored, transparent music reproduction, use a 12 or a 15, with an 18 below 80hz.....
A lot of guys are doing the "PA" in the living room thing on here....that is fine, and a boatload of fun...it just depends on your goal. I prefer a more transparent wall of sound these days....asking which 18" woofer sounds best at 300hz....is like asking which model corvette carries the most luggage and kids

[Mr. Widget]

Been playing with this stuff many years, both for live sound, and home....used 2235H's and 2245H's and 2240's, and 2241's off an on for decades....my two cents is that for home "hifi" use, crossing any 18" higher than 80-100hz sounds too colored. The 2235H any higher than about 300 sounds too colored....

I strongly agree... however folks here will put on their best pouty faces and say, "but JBL used the 2235H up to 1KHz in the 4430/35 and the 2245H up to ~300Hz in the 4345 and those are both studio monitors so you must be wrong!"

The fact is JBL is no different from the rest of us... they have to accept compromises too.... when their sales literature is telling us the praises of one of their designs, they rarely mention the compromises.

So, yes you can use a JBL 18" to 300Hz and a 2235 to 1KHz.... I wouldn't, and I wouldn't try to take a lot of luggage in a Corvette either.


Widget