HELP! I keep blowing my JBL 2245H subs - AVS Forum
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post #1 of 27 Old 09-23-2006, 08:17 AM - Thread Starter
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Ok, so I like my bass!

I got a pair of 2245H, each mounted in a custom build (1" MDF) 16 ft3 vented enclosure.

Here's a front shot from my HT room after I pulled the blown drivers this morning:



Each sub is being powered by a bridged Crown CE 2000 (1,320W into 8 ohms). My crossover is 80Hz and done by my Sony TA-E9000ES pre-amp.

Now, I know that the 2245H is rated for 600W continuous program and my Crowns are capable of more than double that, but I wanted to make sure the amps didn't run out of steam, so that's why I went with this combination.

Ok, so after setting the levels (using my Radio Shack SPL meter and Avia), all is well and good until I watch/listen to a live concert DVD at "concert level" SPLs. You know, where you can feel the bass in your chest.

Last night I was watching some George Clinton P-Funk footage with some nasty bass, and then all of a sudden, the bottom end went out, and sure enough, I had blown both 2245H drivers (this is the third time now).

So should I sent these off the be reconed again, or should I be looking for some other drivers to meet my needs?

I'd obviously prefer something that will work in my existing 16 ft3 vented enclosures, although I can block the ports pretty easy in case a sealed solution is better. These enclosures are extremely rigid with hardwood bracing internally.

I haven't really been keeping up with what's out there as far as 18" drivers, but back when I built my HT, the 2245H were the thing if you wanted accurate bass down to 20Hz or so.

Thanks!
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post #2 of 27 Old 09-23-2006, 09:43 AM
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You are definitely a bassoholic if you are blowing 600 watt rms 18's. I'd consider switching those cabinets to sealed, to take advantage of your amplifier's power. It may not be as good for George Clinton, but may prove to me more accurate, and save you the hassle of blowing another set.

Are these drivers under warranty, or do you pay each time to get them reconed?
What do these JBL drivers run? You can rack up a large bill purchasing new 18" drivers.

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post #3 of 27 Old 09-23-2006, 10:37 AM - Thread Starter
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I think part of the "problem" is that my HT room is very large (23' x 34'), so it takes a lot to get some kicking bass.

I'll look into possibly sealing the enclosures by screwing some 1" MDF plates over the vents.

I don't think JBL is still making the 2245H. They run $600 used from GoldSound with a warranty and about $400 on Ebay in unknown condition. Mine are no longer under warranty and they cost me about $200 each to have reconed.

My Crowns will do 1,950W bridged into 4 ohms, so a pair of 4 ohm 18" drivers that can handle 2000W rms and work well in a 16 ft3 sealed or vented enclosure would be just the ticket, but I don't think such a driver exists?

I do have a servodrive (driver out of a Contrabass) complete with the control panel, but no cabinet. I've been trying to locate a cabinet or plans on how to built one, but so far I have had no luck and it looks to be rather complicated folded horn type cabinet.
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post #4 of 27 Old 09-23-2006, 11:26 AM
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Hi pclausen,

Have you confirmed that you are burning the coils and not mechancially damaging the drivers? These are two failure modes with different causes and solutions.

For a room that size and what you are probably after, I would say you might be pushing it while trying to also get down to 16Hz in the single cabinet you have. Are you clipping the CE2000 in your listening session? Do you have one amp per driver? Clipping the amplifiers quickly increases the average power vs. peak power. Peaks are not as likely to cause thermal failures as the average power.

Since you are already spending quite a bit of money on the JBLs, you might want to take a look at both the Acoupower drivers and some of the new TC Sounds drivers. The Acoupower drivers would be a certain remedy of the thermal failure problem, and give you more sub 50Hz bass capability with better sound quality as you are almost certainly driving the JBL's past their linear limits. Some of the new TC Sounds drivers would also likely work very well, but I haven't modeled them.

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post #5 of 27 Old 09-23-2006, 12:36 PM
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Since you are having them reconed, I will assume you are tearing the surround. Is it possible the an HP filter would help. You are possibly exceeding cone travel limits on the really loud/low passages and that stresses then rips the surround.

Randy
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post #6 of 27 Old 09-23-2006, 01:01 PM
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Randy,

Reconing is the act of re-building all of the moving parts including the voice coil, spider, cone, surround, etc. An "autopsy" of some form needs to be taken to asses the failure mode of the speaker. In simplest terms, an open circuit VC or a nearly shorted coil would suggest thermal problems, as would a brown/black voice coil upon removing the cone.

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post #7 of 27 Old 09-23-2006, 01:07 PM - Thread Starter
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Just to be clear, I have 2 16 ft3 cabinets (one is mounted on top of the other), 2 18" drivers and 2 CE2000 amps each running in bridged mode.

What is happening is that the voice coils are melting I think. The cones are "frozen" in place and won't budge at all. The surround isn't torn at all, but I don't think one can just replace the voice coils independant of the rest of the moving assembly.

I don't hear any distortion at all warning me that the drivers are about to blow. I have to drive them pretty hard for about an hour before the blow. So perhaps they just get real hot after extended listening at high levels and that is what causes the coils the melt?

I've never had any issues when watching movies, and some of those explosions and what not seem to have a lot more going on down real low, but of course this isn't continious so things don't get a chance to heat up.

I don't recall ever seeing the clipping LEDs on the Crowns, but then they are mounted in a rack in the room behind the screen so I can't really tell. I was blowing the breaker occasionally until I ran a dedicated 20A circuit for the Crowns (and another 20A circuit for the Adcom amps (GFA 5500 and GFA 7500).

Those Acoupower units looks like just the ticket Mark.

I just might end up picking up a pair of those. In the long run I should make my money back.

EDIT: Wow, the Acoupower 18's have the exact same 441 mm bolt circle diameter, so they will bolt right up. They are 44 lbs vs. the 30 lbs of the JBLs. The max excursion of the JBL is 25 mm, the Acoupower is 78mm. 3 times more!

I'm like so close to pull the trigger on a pair of them! The Pearl is going to have to wait.
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post #8 of 27 Old 09-23-2006, 03:04 PM
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Thanks for the education Mark. So the whole rotor assembly (using motor terms) is referred to as the cone. This consists of the VC, former, spider, diaphram, and surround? I figured that reconing as you describe it wouldn't have been economical. Learn something every day. At what price point are speakers not economical to recone and should just be replaced? Looking at TC drivers, the SVS TV12 ($579) would be rebuilt, but the DB12 ($169) should just be replaced?

Randy
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post #9 of 27 Old 09-24-2006, 04:10 PM - Thread Starter
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Randy, you might want to check out this site for a general idea of reconing costs for various drivers:

http://simplyspeakers.com/16reconing.htm

I posted about my JBL driver woes over in the DIY forum. It looks like my main issue is the 9.5mm max excursion that my 2245H have.

http://www.avsforum.com/avs-vb/showthread.php?t=727711
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post #10 of 27 Old 09-27-2006, 12:06 PM
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You may want to consider lowering your x-over point from 80 Hz to reduce the amount of heat.
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post #11 of 27 Old 11-30-2006, 04:40 PM
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Has to be distortion, either real high frequency (Unlikely if you are using a passive crossover) or DC. If you are bi amping the lf then the amp could be suspected of HF distortion. Should be easy to check for dc at your speaker cables with a simple volt meter set to DC. No way you can play that unit with the JBL horns loud enough to burn it out and keep your hearing. That setup will take over 20 to 20K at 120 DB steady state for hours on end. That might drop a little in your room size but still super loud.

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post #12 of 27 Old 11-30-2006, 04:51 PM
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Quote:
Originally Posted by Bill Shenefelt View Post

Has to be distortion, either real high frequency (Unlikely if you are using a passive crossover) or DC. If you are bi amping the lf then the amp could be suspected of HF distortion. Should be easy to check for dc at your speaker cables with a simple volt meter set to DC. No way you can play that unit with the JBL horns loud enough to burn it out and keep your hearing. That setup will take over 20 to 20K at 120 DB steady state for hours on end. That might drop a little in your room size but still super loud.

Agree with the above. Woofers are not easy to burn when signal is clean from an amp that is not driven into clipping. And Pro JBL drivers are not little toys that burn,and this often!

I blasted many subs many times and have yet to fry a VC on one!

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #13 of 27 Old 11-30-2006, 05:59 PM
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The only thing that burns voice coils is high average power over time. Period.

In a vented system you have a low impedance range centered right at the port's tuning frequency. If you play a ported box that's tuned at 30 Hz really loud, you will get low excursion but a lot of power being dissipated by the coil between 25 hz and 35 Hz or so... above and below those freq's the impedance rises, power goes down and excursion increases... If your material has lots of energy at or near the tuning frequency, this creates a thermally difficult condition for the speaker if it lasts for a long time. Your situation appears to hit a "perfect storm" when you play Parliament Funkadelic at high SPL's for long periods of time.

Do you know what your enclosure is tuned to? A typical alignment for a 2245H in 8 cu.ft. would have a tuning around 25-30 Hz.

Running them sealed is probably not a great idea as these are low-excursion, high-efficiency designs specifically engineered for vented cabinets.
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post #14 of 27 Old 11-30-2006, 07:11 PM
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Guys, he has already remedied the situation.

http://www.avsforum.com/avs-vb/showthread.php?t=739242

Got those TC drivers and also lowered the Fb for each enclosure...closer to 17Hz IIRC.

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post #15 of 27 Old 11-30-2006, 07:42 PM - Thread Starter
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Willd hit it right on!

I'm not posting much 'cause I'm downstairs *jamming* all the time! I'm so caught up in the awe of it all, that I keep putting off running another couple 20A circuits to behind my racks. I keep blowing my existing 20A circuit because of those damn 18's driven by the Crowns!

A box fan behind the Adcoms help, but I need to run at least another 20A circuit to prevent "the day the music died" from happening. The equipment isn't overheating, it's just pulling too much power!
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post #16 of 27 Old 11-30-2006, 07:49 PM
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Isn't it great?

You fix one problem yet discover another.
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post #17 of 27 Old 12-01-2006, 05:20 AM
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[quote=msmith_JL]The only thing that burns voice coils is high average power over time. Period.

Not period unfortunately. I fried a pair of Diamond Audio 6 inch drivers in my car. Not with volume, just a stupid Kicker 30 watt amp putting out DC. Does not take long at all (a matter of less than a minute) and you never know that they are in trouble since there is no volume heard. The comment about tuning frequency is true also. If you have it tuned too high and do not have a filter for fast drop off below that frequency, the impedence drop will cause super excursions. The reason I say too high is that the impedence does drop quickly below the tuning frequency and if it were low, with music and no dc problem there jsut is not that much there below about 30 cps. Most is around the 40 cps realm. The only thing down in the 20's is a pipe organ with 20 ft+ pipes.
Two things are needed. If tuned using a low frewuency boost you MUST have a low frequency cut off filter or when the input goes 10 cps or so below the enclosure tuned frequency with high power due to a boost, the speaker will bottom out unless you have a fast cutoff(18 to 24 dB/octave). Sixth order crossovers use that technique. Did you find out what was doing it to your jbl's?

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post #18 of 27 Old 12-01-2006, 04:30 PM
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It may be too late, but I think you were simply overpowering your JBL drivers. They were designed to be woofers, not sub woofers. The 600W capacity in likely over a wider frequency range than you were driving them with. You are feeding them more power than they can dissapate, because you are
sending them 1000+ watts below 80 hz while the speaker was designed to take 600W below 400HZ. You are cooking thoose poor things. They were not made for that type of use/abuse.

Following the link it seems like you've found a good solution - i.e. a speaker that was designed to take the power you were sending it.

I'm curious, how do your new drivers compare to what you were using?

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post #19 of 27 Old 12-01-2006, 05:20 PM
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JBL used that driver in a great subwoofer. An 8 cu ft box. If fed with a sixth order network where the box is tuned a little on the low side and the input is properly filtered to cutt off most stuff below 20 cps at 24 dB per octave it will really blast out the spl. If pushed, tuned low and not properly cut off, a reflex enclosure will blow anything. To try to get output for "music" below 25 cps is sort of weird. There just ain't no music down there! Bass guitar is about 42 cps. MAybe some subsonic from Tymphony but tuned to cut off at 25 should give that pretty well. I had mine in an 8 cu ft, tuned to about 25 with a 6th order crossover coming in about 50 cps. Took it out of the system. The 136A 15 inch drivers went down to nearly 30 without it and sounded much better without it. That speaker is a great unit from about 25 to 800+cps if properly set up. For full range(35 to 800) with the accompanying horns above that it is great. For 50 down as a sub, the same IF properly set to remove subsonic excursions.

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post #20 of 27 Old 12-02-2006, 07:44 PM
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[quote=Bill Shenefelt]
Quote:
Originally Posted by msmith_JL View Post

The only thing that burns voice coils is high average power over time. Period.

Not period unfortunately. I fried a pair of Diamond Audio 6 inch drivers in my car. Not with volume, just a stupid Kicker 30 watt amp putting out DC.

Bill,
I am certain that Mr. Smith knoes about the damage that can be done to a driver by an amp going into straight DC...

I know that they kept a "trophy" blown driver which came from an install done by my former company. It was a 10W5's who's VC former broke free of the neck joint (joint between VC former and cone) and launched forward to the underside of the dustcap, which then melted around the former.

A beast was born, Godzilla...

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post #21 of 27 Old 12-03-2006, 07:30 AM
 
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pclausen

I know this might sound out of order. But third time in a row is simple negligence and miss-care with settings heavens above I don't know how you could have possibly done this three times in a row!

I've been running the JBL 4645 cinema sub bass with a newer JBL 2240H sub bass driver now for the past 8 years and not a single days trouble with. It might have something to do with that fact that I've worked in the cinema industry for UCI and Warner Bros as projectionist some take it quit literal and some don't.

Mate I may have solution a very cheap and affordable way of keeping an eye on the exclusive baby boom track or as it is called now LFE.1

The room hasn't really got anything to do with the size. The Empire Leicester square in London used to use up to x8 JBL 4645 and not one of them ever blew! The Empire has been refitted this summertime 2006, with THX and JBL with a whooping x16 JBL 4645C subs behind the screen, which is 13 feet wide and 8 feet high!

Now the reason why you're probably destroying the JBL 4645H is! Overdriven with too much input going into the amplifier, I bet you £1.00 pound UK! That you're LFE.1 content is exceeding 0db!!!

Here's my JBL set-up note the JBL 4645 placed to the left-hand corner, you can't miss it it's LOL larger than the flipping SONY monitor!



The AVR set-up is somewhat complicated and yet it so simple with a few special modification, note the stereo audio mixer above!



All outputs from the Kenwood KRF-X9050D THX select uses RCA phone outputs this gives the user greater flexibility!

Also my set-up goes though a rigorous special processing where I can control the mix within the Dolby dts 5.1 domain!

Now, sub bass extension and LFE.1 content which is set to 0db with THX bass manager tuned to ON! Helps keep the LFE.1 from exceeding 0db when the Kenwood KRF-X9050D THX fader is set to 0db!

Also the outputs for left and right monaural sub bass extension passes into the audio mixer where it is balanced, centre channel monaural sub bass extension also passes into the audio mixer where it is balanced surrounds are also balanced and all this via separate inputs!

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post #22 of 27 Old 01-03-2007, 03:24 PM
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well everyone that is a bit interested in the JBL 18" knows they are DESIGNED to be used in a 225l
enclosure. the 2242H is one mighty unit, handling 800w cotninuous and 3200w peaks.
but it MUST be also protected at minimum 20hz 12db per octave filter +B6 filtering.
and if you need more bass ADD MORE SUBS rather more amp power !!. put some bass resonators too to flatten response and correct nulls

the danger of DIY i see...

i have two 2242H 4645C THX units for now about 8years i think and no problem. they fill a large HT of total 9x4.3meters (see pics in the digital gallery)
they are nourrished by a QSC SRA 2422 and velodyne processor and 10sq mm cables.
i will add 2 more some day or a velodyne dd15 at the rear or 6 15" for the mid bass (40-100hz) and leave the 4645C do the LFE + <40hz. haven't decided yet.
good friend of mine has also 2 4645c and no problem at all
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post #23 of 27 Old 01-03-2007, 05:02 PM
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JBL did use that driver(different number maybe but same theil small parameters) back then maybe but as a wide range driver used in their 3 way Bi radial "baby cheeks horns" monitors as a bass driver crossed over at about 800 CPS and a subwoofer sold in a separate amplified enclosure. The sub was used to extend bass responce from about 32 cps in the 15 inch version (called 136 A before they started dumping the alnicos to save $) down to about 28 cps I think. When in the 3 way system, it was just used to increase SPL a little. These are MUSIC speakers, not room shakers or chest pounders! There is virtually little real music below 40 cps other than pipe organ and then it takes a 32 ft pipe to reach to the levels that the 18 can still put out. Few pipe organs have that size pipes. I had my 18 " jbl in an 8 cu ft enclosure with a 6 inch port (with elbow to achieve the required length) tuned to about 28 cps and a 6th (24 db/octave) order active crossover to cut it off drastically about 22 cps. It could light the lights on a 250 watt heath with 3 db headroom bridged. No problem. I pulled it from my system returning to just the 15 inch jbls since I thought the extra crossover cost me more in fidelity than I really gained from any non functional bass extension. It now purrs along on a 200 heath as a home theater sub. Seldom sees 20 watts peak but that is enough for most movies. (front side speakers are the equivalent of 6 cu ft L200 JBL studio monitors (horn/15 inch bass) The only speakers I ever fried were a real nice pair of Diamond acoustics 6 inch car speakers. Stupid kicker amp went DC on me and froze up the voice coils without a peep out of them. I think what the guy needs is a long excrusion/non musical bass thumper to give him whatever felt sound he is after. Not being derogatory, just that there ain't no music down there. This speaker is built as a music speaker for studio mizing and monitoring.

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post #24 of 27 Old 04-10-2008, 05:48 AM
 
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I'm just wondering if you have fixed the issue with blowing JBL sub bass low frequency transducers, because I keep getting some member PM me, asking me about the JBL4645H.

I don't even own the JBL 4645H, sure I own JBL 2240 but why I keep getting PM even few 6 months or so is crazy.
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post #25 of 27 Old 04-10-2008, 05:53 AM
 
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Quote:
Originally Posted by Bill Shenefelt View Post

JBL did use that driver(different number maybe but same theil small parameters) back then maybe but as a wide range driver used in their 3 way Bi radial "baby cheeks horns" monitors as a bass driver crossed over at about 800 CPS and a subwoofer sold in a separate amplified enclosure. The sub was used to extend bass responce from about 32 cps in the 15 inch version (called 136 A before they started dumping the alnicos to save $) down to about 28 cps I think. When in the 3 way system, it was just used to increase SPL a little. These are MUSIC speakers, not room shakers or chest pounders! There is virtually little real music below 40 cps other than pipe organ and then it takes a 32 ft pipe to reach to the levels that the 18 can still put out. Few pipe organs have that size pipes. I had my 18 " jbl in an 8 cu ft enclosure with a 6 inch port (with elbow to achieve the required length) tuned to about 28 cps and a 6th (24 db/octave) order active crossover to cut it off drastically about 22 cps. It could light the lights on a 250 watt heath with 3 db headroom bridged. No problem. I pulled it from my system returning to just the 15 inch jbls since I thought the extra crossover cost me more in fidelity than I really gained from any non functional bass extension. It now purrs along on a 200 heath as a home theater sub. Seldom sees 20 watts peak but that is enough for most movies. (front side speakers are the equivalent of 6 cu ft L200 JBL studio monitors (horn/15 inch bass) The only speakers I ever fried were a real nice pair of Diamond acoustics 6 inch car speakers. Stupid kicker amp went DC on me and froze up the voice coils without a peep out of them. I think what the guy needs is a long excrusion/non musical bass thumper to give him whatever felt sound he is after. Not being derogatory, just that there ain't no music down there. This speaker is built as a music speaker for studio mizing and monitoring.

A 32 footer pipe now I was thinking about something last year maybe the year before. How about a sealed box with the 18” sub bass drivers housed deep inside and with long pipe extending upwards from where the sub sits on the floor then the pipe bends off at 45° and then travels the length of the room what ever length that may be.

Get the general idea of the idea? Not sure if it would be a complete success thou, trial and error I guess.
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post #26 of 27 Old 12-13-2008, 02:13 PM
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Hi
Nice box you have there. Mine was not quite as nice but was working perfectly...until I torn the suspension...
I have (I had) 2 JBL 2245H monted as BandPass and good for at leas 16 Hz (verified).
For music, they were excellent. But when I installed my HT system and started listening to films, things got out of hand.
I was listening to the last "Pirates of the Carribeans" and the base was blowing my pants!!!!!
That's the last I hard of them..... Now, all I get is a BUZZ. The voice coils are still ok: they measure 5.6 ohms but the suspension is blown, unglued, torn...
I will try selling them as is and replace them with SVS 13 ultra.
The suspension is too narrow for them to shove air at 15 HZ even at 200 Watts a peice...
Regards

Horace
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post #27 of 27 Old 04-22-2009, 01:38 PM
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Quote:
Originally Posted by msmith_JL View Post

The only thing that burns voice coils is high average power over time. Period.

In a vented system you have a low impedance range centered right at the port's tuning frequency. If you play a ported box that's tuned at 30 Hz really loud, you will get low excursion but a lot of power being dissipated by the coil between 25 hz and 35 Hz or so... above and below those freq's the impedance rises, power goes down and excursion increases... If your material has lots of energy at or near the tuning frequency, this creates a thermally difficult condition for the speaker if it lasts for a long time. Your situation appears to hit a "perfect storm" when you play Parliament Funkadelic at high SPL's for long periods of time.

Do you know what your enclosure is tuned to? A typical alignment for a 2245H in 8 cu.ft. would have a tuning around 25-30 Hz.

Running them sealed is probably not a great idea as these are low-excursion, high-efficiency designs specifically engineered for vented cabinets.


Excellent post. At the resonant frequenct (FS) the voice coils are held at bay by the port resistance and have little means to dissipate the heat!
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