I'm thinking about taking an 8" MCM 55-2421 and sticking it in an existing 36 liter sealed enclosure. Qtc will end up around 0.30, which is too low, but that's the box I've already got and I'm so lazy. Then I'm going to bolster the bottom end with about 12 dB of EQ centered at 34 Hz or so. Is this going to be a horrible mistake? I've got about 300 watts to spend at the amplifier end.
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Download WinISD and model it. If the box is too big maybe try wrapping some polyester stuffing around a couple of bricks and stick them in the box to remove cabinet volume 🙂
I once put 14dB of gain at 28Hz on a pair of 8" drivers, 44L sealed.
Sounded reasonable until turned up - excursion got very silly very quickly. IMO, the rule of thumb about an 8" driver going to 40Hz is about right. Even then, you're limited on how loud you can have it.
Chris
Sounded reasonable until turned up - excursion got very silly very quickly. IMO, the rule of thumb about an 8" driver going to 40Hz is about right. Even then, you're limited on how loud you can have it.
Chris
you might find this project interesting:
P48 Sub-Woofer Controller (Rev-A)
I run a pair of 10" car subs in very small enclosures with a ESP P48A with the peak set at 33 Hz in a apartment, works well.
P48 Sub-Woofer Controller (Rev-A)
I run a pair of 10" car subs in very small enclosures with a ESP P48A with the peak set at 33 Hz in a apartment, works well.
The lower qtc (+ EQ), the better for a sealed system. This will reduce distorsion below the system resonance frequency where the mass control is lost.
I've never been a fan of peaking response by storing energy in the transducer system. Low Q sealed is about the only way to get a low output impedance into the room. Raising Q just stores energy in the transducer, yuk! I also find building cabinets for large, such as an 18", much more difficult than building four top quality 10" cabinets. Easy to make a small cabinet solid and light weight. But that 18" cabinet was over 400 pounds!
I did a quick and dirty test using a Tripath amp and a DSP crossover. It actually sounded rather nice, up to the limits of the amp. Boy, when that thing clips there is no mistaking it. As you approach 30 Hz there is a lot of excursion, even with the measly six watts or so coming out the Tripath amp. My daughter was impressed with it, however. My wife wondered what was causing the gentle rumble in the floor.
Overall, it seemed good enough to pursue further. I think I might clean up the boxes a bit, connect it to a real amp, and experiment a bit more with the equalization. If I can find my good mic, I might try to take some measurements and see if I can achieve a somewhat flat response.
Cal thinks col's idea about adding some filler to the box is a great place to start. Done it many times to determine the "right" size box. reusing some older, larger ones to experiment with instead of building anew.
Just had a look at which driver you're using.
Mine had a mere 3mm one-way Xmax, so I think yours will handle the boost better. I would still consider putting a low cut filter somewhere low down (25Hz?) in case it ever comes into contact with movies - here lieth the monsters.
Chris
Mine had a mere 3mm one-way Xmax, so I think yours will handle the boost better. I would still consider putting a low cut filter somewhere low down (25Hz?) in case it ever comes into contact with movies - here lieth the monsters.
Chris
I am faceing a similar problem. One thing to think about is just using a seriese resistor
in line with the woffer. You have to do some calculations to find the value but I would expect you would need something in the 4 to 20 ohm range and needless to
say high wattage. You would loose a lot of amp power but as you said with 300W to play with.
in line with the woffer. You have to do some calculations to find the value but I would expect you would need something in the 4 to 20 ohm range and needless to
say high wattage. You would loose a lot of amp power but as you said with 300W to play with.
Modeling Clay
If you want to work in a bigger box adding mass to the cone seems a better choice than a series resistor. Use modeling clay or something kind of sticky and heavy and add a ring at the dust cap for testing. Easily removed. This also allows adding lots of mass and playing around a bit.🙂
If you want to work in a bigger box adding mass to the cone seems a better choice than a series resistor. Use modeling clay or something kind of sticky and heavy and add a ring at the dust cap for testing. Easily removed. This also allows adding lots of mass and playing around a bit.🙂
I don't see anything wrong with oversized sealed boxes personally. At some point, it just starts to act like an IB install, which any speaker can work in at least acceptably well.
The only thing a smaller box will do, is take away efficiency and replace it with power handling, which does nothing to improve output on the bottom end. Small sealed boxes will cause you to run into thermal power handling issues before excursion, which translates to lower maximum output in many cases.
WinISD is telling me that you would be Xmax limited to ~70W @ 34hz (94dB@1M) in a 36l box. Down to ~50W at 25hz (89dB@1M). Not the most spectacular bottom end extension, but, it will work.
Dropping down to a 7L box will increase Pe to 120W@34hz, but at 120W, output drops to 93db@1M. Same problem with the 25hz test, Pe is up to 120W, but the actual output at that power in the small box is 88dB, worse than the large box with less than half the power.
The only thing a smaller box will do, is take away efficiency and replace it with power handling, which does nothing to improve output on the bottom end. Small sealed boxes will cause you to run into thermal power handling issues before excursion, which translates to lower maximum output in many cases.
WinISD is telling me that you would be Xmax limited to ~70W @ 34hz (94dB@1M) in a 36l box. Down to ~50W at 25hz (89dB@1M). Not the most spectacular bottom end extension, but, it will work.
Dropping down to a 7L box will increase Pe to 120W@34hz, but at 120W, output drops to 93db@1M. Same problem with the 25hz test, Pe is up to 120W, but the actual output at that power in the small box is 88dB, worse than the large box with less than half the power.
"Small sealed boxes will cause you to run into thermal power handling issues before excursion," -mdocod
Sorry to disagree but have never seen this happen in real testing and and in many real applications installations. Every woofer I have ever used ran out of excursion long before even approaching the thermal limit. For that reason am only using 30-50 watts per 10" driver, 1.5"VC, & 28 ounce magnet. This is enough power to move the cone almost double Xmax at the lower end of 40Hz. Power handling on "normal" 1.5" voice coils is around 75 watts.
Maybe mdocod above was referencing these many very low efficiency woofers which have become popular in recent times. If this were an 80dB for 1 watt woofer then yes, it may thermal out before Xmax is reached. In that case I should apologize.
On the other hand, I deplore inefficient transducers and never waste my time even considering them. All drivers need a 90dB for one watt or higher sensitivity.
Sorry to disagree but have never seen this happen in real testing and and in many real applications installations. Every woofer I have ever used ran out of excursion long before even approaching the thermal limit. For that reason am only using 30-50 watts per 10" driver, 1.5"VC, & 28 ounce magnet. This is enough power to move the cone almost double Xmax at the lower end of 40Hz. Power handling on "normal" 1.5" voice coils is around 75 watts.
Maybe mdocod above was referencing these many very low efficiency woofers which have become popular in recent times. If this were an 80dB for 1 watt woofer then yes, it may thermal out before Xmax is reached. In that case I should apologize.
On the other hand, I deplore inefficient transducers and never waste my time even considering them. All drivers need a 90dB for one watt or higher sensitivity.
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