I am frustrated with my speakers that i put a lot of time and learning into building and I still have a nagging problem of no bass with my system.
My design goals were to create a system with high SPL and extended frequency range. My amp is only about 50 WPC, so efficient speakers are pretty much a must. I use these for playing music mostly.
The speaker is a 3-way with a 15" JBL 2235H woofer, an Audax PR170M0 for the mid, and a Morel MDT-37 tweeter.
The mid and tweeter are in their own sub-cabinet. The 2235H is in a 6 cubic foot ported enclosure with two 3.95" diameter flared vents 6" long (tuned to 32 Hz).
I should see a flat response down to at least 35 Hz (according to LEAP and Bass Box Pro), but it dies at about 55 Hz.
Madisound designed the 3-way crossover using LEAP. It sounds great, except the lack of bass.
I did a 1 meter frequency plot on-axis and got this:
Here is the mic stuck right into one of the ports:
I am just baffled by the lack of bass and I would have though the JBL would kick butt in this department, but it doesn't and I can't seem to explain why.
Anyone have any ideas?
My design goals were to create a system with high SPL and extended frequency range. My amp is only about 50 WPC, so efficient speakers are pretty much a must. I use these for playing music mostly.
The speaker is a 3-way with a 15" JBL 2235H woofer, an Audax PR170M0 for the mid, and a Morel MDT-37 tweeter.
The mid and tweeter are in their own sub-cabinet. The 2235H is in a 6 cubic foot ported enclosure with two 3.95" diameter flared vents 6" long (tuned to 32 Hz).
I should see a flat response down to at least 35 Hz (according to LEAP and Bass Box Pro), but it dies at about 55 Hz.
Madisound designed the 3-way crossover using LEAP. It sounds great, except the lack of bass.
I did a 1 meter frequency plot on-axis and got this:
An externally hosted image should be here but it was not working when we last tested it.
Here is the mic stuck right into one of the ports:
An externally hosted image should be here but it was not working when we last tested it.
I am just baffled by the lack of bass and I would have though the JBL would kick butt in this department, but it doesn't and I can't seem to explain why.
Anyone have any ideas?
Room is about 15' by 33' with a sloped ceiling. Room is a bit live as it contains a kitchen. I have not dragged the speaker outside (the bugger is heavy!!!).
I ran the tests with the speaker moved into the middle of the room facing a sofa with the mic stand in front of it about 1 meter away. I tried other arrangements and different volumes and get the same basic plots, so I think the measurements are correct. Well, they are at least consistent.
Yes, the tool is Fuzmeasure 3.2. Good catch!
JBL 15"s should kick butt on LF (I owned a pair of JBL L201s? driven by a 85 watt amp and never had a lack of bass, even at partys with 150 people). A couple things you could check. If you havent already). Make sure the the speakers are wired in phase? (Swap + and - at one speaker and see if you get less bass). Make sure the pre and amp are putting out LF. (tone sweep?) Make sure you arnt measuring in a LF room mode null (move the mic around the whole room and try a few more measurements (or test it properly and take it outside). Try measuring 1 speaker at a time (to avoid acoustic phase cancelation between the 2 speakers, although this shouldnt matter if the mic is centered between the speakers)
Sorry reread your post and saw you were testing one speaker so disregard the phase swap etc.
Sorry reread your post and saw you were testing one speaker so disregard the phase swap etc.
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First thing I'd try is to hustle up someone elses amp, particularly if you can get your hands on a reputable one, as it is very easy to then eliminate this as the problem. I'm talking about frequency response/damping factor/speaker control etc. being the problem rather than total power. You should get plenty of bass with 50W.
What amplifier source impedance was assumed when choosing the bass alignment and designing the cross-over? You might want to try inserting a small amount of series resistance between amp and speaker and see if the measured result changes- this will increase driver QES and thereby QTS. All of this assumes that the low cut filter if present on your amp is not turned on and the amplifier otherwise works properly.
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First check the polarity as Cal Weldon suggested.
But then frankly there is nothing wrong with the graph you posted. That's what those JBL speakers more or less should look like. And you should NOT expect to hear any bass out of them.
Modern hi-fi systems come with built in house curve:
DIY-AV • View topic - House Curve ( Part 1 of 2 )
take a look at the measurement of Sennheiser IE-8 headphone which gets rave reviews:
when your system measures like that - then you will have the bass you want !
in fact that's what my system more or less looks like except the bass doesn't stop rising at 100 hz. in fact it is rising the fastest at around 30 hz.
you have a GOOD SYSTEM man. just throw an equalizer and a pair of 1,000W subwoofers (50hz crossover) in the mix and you're good.
But then frankly there is nothing wrong with the graph you posted. That's what those JBL speakers more or less should look like. And you should NOT expect to hear any bass out of them.
Modern hi-fi systems come with built in house curve:
DIY-AV • View topic - House Curve ( Part 1 of 2 )
take a look at the measurement of Sennheiser IE-8 headphone which gets rave reviews:
An externally hosted image should be here but it was not working when we last tested it.
when your system measures like that - then you will have the bass you want !
in fact that's what my system more or less looks like except the bass doesn't stop rising at 100 hz. in fact it is rising the fastest at around 30 hz.
you have a GOOD SYSTEM man. just throw an equalizer and a pair of 1,000W subwoofers (50hz crossover) in the mix and you're good.
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LOL! Have you ever actually used a pair of the woofers he's using??
Rob
no but i have 15" JBL DJ speakers and they have no bass.
It would not surprise me in the slightest that borat could well be correct.
I have not done any sims on those drivers.
however, I run PHL 18's. Pro drivers (and I assume the JBLs have the same heritage??).
they do not go below seventy hz naturally.
I eq the hell out of them (and the lowest I can get them even then is thirty) but I have the most visceral, impressive bass you could want for. (after eq I mean)
does that follow in this case? dunno.
but I can well imagine it.
eq them, throw power at them and you will be in heaven.
50 w will not cut the mustard for that amount of eq.
I have not done any sims on those drivers.
however, I run PHL 18's. Pro drivers (and I assume the JBLs have the same heritage??).
they do not go below seventy hz naturally.
I eq the hell out of them (and the lowest I can get them even then is thirty) but I have the most visceral, impressive bass you could want for. (after eq I mean)
does that follow in this case? dunno.
but I can well imagine it.
eq them, throw power at them and you will be in heaven.
50 w will not cut the mustard for that amount of eq.
Hmm ... I checked the vent calculation and did a quick sim.
Looks like you got the math right - it should go much lower.
Some ideas:
1) Is the box properly sealed - no gaps/cracks/leaks?
2) What about the microphone you measured with?
(Maybe the mic has a lousy response)
3) New drivers will still be stiff and need breaking in.
Here's something I never heard of before:
Lansing Heritage Forums - Le15A...how low does yours go?
Suspension of old JBL drivers stiffen with age and need to be treated with brake fluid!?
Looks like you got the math right - it should go much lower.
Some ideas:
1) Is the box properly sealed - no gaps/cracks/leaks?
2) What about the microphone you measured with?
(Maybe the mic has a lousy response)
3) New drivers will still be stiff and need breaking in.
Here's something I never heard of before:
Lansing Heritage Forums - Le15A...how low does yours go?
Suspension of old JBL drivers stiffen with age and need to be treated with brake fluid!?
Lack of bass could be caused by room cancellations. Do a near-field measurement as close to the cabinet as possible, and halfway between the woofer and the port. That should tell you if the speaker itself outputs any low bass. This kind of measurement isolates the room pretty well. You could also measure impedance to check if the bass port tuning frequency is wrong.
Well, many different questions by everyone and thank you so much for your responses.
I can take some far-field measurements, but my understanding was that a 1-meter distance, on-axis plot is pretty standard in the industry. Going far field would add more room acoustics to the mix, I presume.
I coud drag one outside and run a sweep, but these are not easy to tote around. I need a dolly to move these and the step from inside to outside is a bitch, too.
I could also actually listen to one speaker, but it doesn't seem to make sense to me as I know the bass is lacking and I can measure what I subjectively hear with a sweep.
As far as the amp goes, it is one I built. It is just a power amp, so no tone controls are in the circuit. I already measured the amps frequency and distortion characteristics and it is flat down to about 10 Hz. I don't know what the damping factor is.
Kevin, this is the LEAP designed crossover file:
http://www.mdbq.net/pyramid/leap.pdf
Let me know what you think. All components are good quality components.
Johan, the drivers are older, but have new surrounds. The cones got beat up during shipment some time ago. Actually, it was the domes. I pulled them back into shape with tape, did a impedance measurement sweep, and put them into service.
Today I will do an impedance sweep of the cabinet and I will also do a near-field sweep with the mic located between one port (there are two ports, one on each side of the woofer) and the woofer.
Here is a little picture of the cabinet:
I can take some far-field measurements, but my understanding was that a 1-meter distance, on-axis plot is pretty standard in the industry. Going far field would add more room acoustics to the mix, I presume.
I coud drag one outside and run a sweep, but these are not easy to tote around. I need a dolly to move these and the step from inside to outside is a bitch, too.
I could also actually listen to one speaker, but it doesn't seem to make sense to me as I know the bass is lacking and I can measure what I subjectively hear with a sweep.
As far as the amp goes, it is one I built. It is just a power amp, so no tone controls are in the circuit. I already measured the amps frequency and distortion characteristics and it is flat down to about 10 Hz. I don't know what the damping factor is.
Kevin, this is the LEAP designed crossover file:
http://www.mdbq.net/pyramid/leap.pdf
Let me know what you think. All components are good quality components.
Johan, the drivers are older, but have new surrounds. The cones got beat up during shipment some time ago. Actually, it was the domes. I pulled them back into shape with tape, did a impedance measurement sweep, and put them into service.
Today I will do an impedance sweep of the cabinet and I will also do a near-field sweep with the mic located between one port (there are two ports, one on each side of the woofer) and the woofer.
Here is a little picture of the cabinet:
An externally hosted image should be here but it was not working when we last tested it.
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