The only attributes that are important for box volume reduction are that (1) the material being used to reduce the volume is "stiff", and (2) the material being used to reduce the volume is airtight and (3) it is rigidly fixed to the inside of the enclosure. For example, you can use a small hollow airtight box with thin stiff walls as a volume reducer and it would be just as effective as using a concrete brick with the same external dimensions. In fact, the "cone correction" I used for my POC3 TH is just that - a small box with a hollowed out interior (so it adds slightly less weight to the TH, which is heavy enough already, LOL).
Hi Brian Steele,
We agree on (1) (2) and (3) but we seem to disagree about the material and its properties, to deliver the needed acoustic stiffness, that's all.
For clearance, I do think that XPS has enough structural strength to enforce a relative 'weak' sealing material like drywall for instance. Not sure how durable drywall is under all those vibrations so I would use reinforced epoxy (but is more work and more expensive than wood). The only 'danger' I foresee is that it might resonate within the bandpass of the TH and XPS does not deliver any significant acoustic damping. A wooden cone-volume-correction does not suffer from it and can also increase the acoustic stiffness of the first segment, which is clearly audible.
Regards,
Djim
(Ps we still have to figure out something, don't we?! Perhaps private message?)
We agree on (1) (2) and (3) but we seem to disagree about the material and its properties, to deliver the needed acoustic stiffness, that's all.
For clearance, I do think that XPS has enough structural strength to enforce a relative 'weak' sealing material like drywall for instance. Not sure how durable drywall is under all those vibrations so I would use reinforced epoxy (but is more work and more expensive than wood). The only 'danger' I foresee is that it might resonate within the bandpass of the TH and XPS does not deliver any significant acoustic damping. A wooden cone-volume-correction does not suffer from it and can also increase the acoustic stiffness of the first segment, which is clearly audible.
Regards,
Djim
(Ps we still have to figure out something, don't we?! Perhaps private message?)
Hello again,
so I read the entire Thread and Im still not sure whats the right cone correction. To be Honest, i dont know either which plan in general is the best for the 18sw115. the new version seems to have the cone correction + internal bracing. There were many suggestions (disks for the cone correction, etc with a lot of helpful suggestions) but I still dont know which one is the right one (correction). the corrections that I found for the B&C chassis are without any dimensions (build photos). I found a detailed cone correction / but its for another driver...
the disk correction is with dimensions but is this suitable for the 18sw115 ( Post #1633) ?
I dont want to damage the subwoofer chassis right away (school holiday is over so i cant work for a new one), so I would prefer a cone correction with a lower compression rate or a correction that is "tested" with the driver and is working, even with "full power".
I ordered the 18SW115-4 and I got the 18SW115-8 (......) (slightly different TSP, more like 6,5-7 Ohms nominal than 8 and 2-3 dB less output from what i saw / heard).
is the motor too weak on the 8 Ohm version ?
I assume that the ideal cone correction remains the same as with the 4 Ohm Version (same cone) ?
does the 8 Ohm even work ? the motor should be weaker (maybe too weak for the th18?)
Would the initial Plan + Bracing and the Disk cone correction work with the 8 Ohm 18SW115 ?
Are there other changes when it comes to this chassis ?
I know that its tiring to answer similar questions over and over again but that would really help me (& help to get started)
best regards
so I read the entire Thread and Im still not sure whats the right cone correction. To be Honest, i dont know either which plan in general is the best for the 18sw115. the new version seems to have the cone correction + internal bracing. There were many suggestions (disks for the cone correction, etc with a lot of helpful suggestions) but I still dont know which one is the right one (correction). the corrections that I found for the B&C chassis are without any dimensions (build photos). I found a detailed cone correction / but its for another driver...
the disk correction is with dimensions but is this suitable for the 18sw115 ( Post #1633) ?
I dont want to damage the subwoofer chassis right away (school holiday is over so i cant work for a new one), so I would prefer a cone correction with a lower compression rate or a correction that is "tested" with the driver and is working, even with "full power".
I ordered the 18SW115-4 and I got the 18SW115-8 (......) (slightly different TSP, more like 6,5-7 Ohms nominal than 8 and 2-3 dB less output from what i saw / heard).
is the motor too weak on the 8 Ohm version ?
I assume that the ideal cone correction remains the same as with the 4 Ohm Version (same cone) ?
does the 8 Ohm even work ? the motor should be weaker (maybe too weak for the th18?)
Would the initial Plan + Bracing and the Disk cone correction work with the 8 Ohm 18SW115 ?
Are there other changes when it comes to this chassis ?
I know that its tiring to answer similar questions over and over again but that would really help me (& help to get started)
best regards
Hello everyone, I did some tests between the TH18 vs L-ACOUSTICS SB28 , 2 vs 2.
In the blue measurement one can see the response of the 2 TH18 with crossover and EQ and all pass filters to match their impedance trace and coupled to the SB28 .
Yellow curve there's the SB28 raw response and red is processed on the LA8. They add 11.5 dB @34 HZ 0.7 Q
In the blue measurement one can see the response of the 2 TH18 with crossover and EQ and all pass filters to match their impedance trace and coupled to the SB28 .
Yellow curve there's the SB28 raw response and red is processed on the LA8. They add 11.5 dB @34 HZ 0.7 Q
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Had some fun yesterday.
The 2 Xoc1 on FP14000 clone vs the 2 SB28 was the most interesting. The SB28 goes 1-2,5 DB over the 2 Xoc 1 Th18 max SPL burst. Also, they can sustain for longer without heating.
Obs.: Next to the Xoc1 there are 2 DB S30 that were not turned on during the measurement on the Xoc and the tuning of the enclosure is at 56.2 Hz where one can se a bump
The 2 Xoc1 on FP14000 clone vs the 2 SB28 was the most interesting. The SB28 goes 1-2,5 DB over the 2 Xoc 1 Th18 max SPL burst. Also, they can sustain for longer without heating.
Obs.: Next to the Xoc1 there are 2 DB S30 that were not turned on during the measurement on the Xoc and the tuning of the enclosure is at 56.2 Hz where one can se a bump
I've spent a lot of time to integrate the subs to work together. But in the end I I had to choose. Up to +6 dB over in some bands or an even +3 dB across all. I choose +6 dB around 40-75 hz band .
After all I decided not to use those DB S30 and to integrate these 2 types perfectly, I gained 4-5 dB across the band. I've put the LPF at 115 hz and I added a "bit " of eq on the TH18 to make them sound more like the SB28 .
After all I decided not to use those DB S30 and to integrate these 2 types perfectly, I gained 4-5 dB across the band. I've put the LPF at 115 hz and I added a "bit " of eq on the TH18 to make them sound more like the SB28 .
How does the FR of the SB28 hold up at higher power levels? Any sign of vent compression effects?
The measurement graphs are not sensitivity measurements. Nor they're max SPL . They just show the relative magnitude response to show how they compare
The port on the SB28 is very big, the enclosure is large enough and the BMS 18n850V2 drivers handle large signals pretty well.on the LA8 amp the excursion is kept under 12 mm even when they are pushed in clipping. Because of the PEQ added at 34 hz, the sub keeps it's response shape almost intact up until limiting occurs . I didn't take long term sweeps to see power compressions because the setup was not that well controlled but the air speed was very low on that sub. Even when I put it on the clone an I hit the 195volts VPL led, the air speeds didn't cause any noise
Ah, ok. I was wondering about how the 28's had a relatively higher response. So I guess it's not because of sensitivity but rather impedance.
Thanks.
John
Hmm... perhaps that's why TD uses 4 ohm drivers in the TH118, for a more direct comparision with 2x18 BR systems that would have a combined impedance of 4 ohms
.What I was interested in was how they compare to a real double 18", in real life use , with recommended settings for each of them. And as the SB28 should be used in combination with the LA8 with recommended presets, I used the TH18 with the 8 Ohms drivers on the clone with VPL settings at 195 Vpeak soft clipping (about 3200 watt at impedance minimums) to keep the excursion in the recommended Klippel protection value of 16.7 mm, with RMS limiter set at 140 Volts peak with 250 ms attack time and 1200ms release to keep the power in check and in use on all types of music genres, from hip hop, techno, dance, DNB, live recordings, drums, rock, you name it, the SB28 had a small edge on them. Measured with a Bruel Kjaer 2270 at 10 meters, the SB recorded higher LCPEAK, fast and slow time constant SPLz values of 1 to 2.5 dB over, depending on song. The purpose was exactly that, to see which one is louder or is felt better, or has better sound , or goes deeper, or got hotter in everyday use, with everyday music and not trough sensitivity measurements or other Lab tests. But I will do that very soon.
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There is a good reason why touring companies use ported cabinets. They are the most compact cabinet but need more power.
If the driver & amplifier count was the same for reflex & tapped horn then the tapped horn pair would in theory gain another 6dB.
So if the builder does not mind the extra size then there is an advantage for the tapped horn.
Interesting comparisons
I wonder what the cost comparison is?
I designed the TH18 in my man cave in my spare time. I wonder how that compares with the R&D budget of L-Acoustics.
Regards Xoc1
If the driver & amplifier count was the same for reflex & tapped horn then the tapped horn pair would in theory gain another 6dB.
So if the builder does not mind the extra size then there is an advantage for the tapped horn.
Interesting comparisons
I wonder what the cost comparison is?
I designed the TH18 in my man cave in my spare time. I wonder how that compares with the R&D budget of L-Acoustics.
Regards Xoc1
Clearly, there's no comparison between the costs of there subs. One SB28 is 5500€ street price. I will soon put my hands on a pair of Danley TH118 that costs about 25-30% less than that here in Europe and I will make some measurements in a controlled manner, double and triple checking the results. I will compare it with two types of reflex subs that are using the same 18SW115-8 drivers inside: a L-ACOUSTICS KS28 , tuned to 29.5 hz and a Nexo RS18 with almost the same volume but tuned to 37 hz.There is a good reason why touring companies use ported cabinets. They are the most compact cabinet but need more power.
If the driver & amplifier count was the same for reflex & tapped horn then the tapped horn pair would in theory gain another 6dB.
So if the builder does not mind the extra size then there is an advantage for the tapped horn.
Interesting comparisons
I wonder what the cost comparison is?
I designed the TH18 in my man cave in my spare time. I wonder how that compares with the R&D budget of L-Acoustics.
Regards Xoc1
In the meantime I will make more experiments with a different driver
it would be interesting to see/hear the difference between the sb28 and the new improved ks28 with the LA12X amp.... must be a perfect vented sub.
but what do you think about the sound? the SB28 shurely is a premium vented sub but how would you describe the sound compared to your tapped horns? i like the very fast impulse response or "attack" of the hornsubs. to me its completely different sound compared to bassreflex sound. would be fine to read also something about this aspect.
Regards Bertlsound
but what do you think about the sound? the SB28 shurely is a premium vented sub but how would you describe the sound compared to your tapped horns? i like the very fast impulse response or "attack" of the hornsubs. to me its completely different sound compared to bassreflex sound. would be fine to read also something about this aspect.
Regards Bertlsound
Today tested with different L'Acoustics subs and especially its presets (on a LA12x). I used the 100hz presets in my measurements. We had SB28's and KS28's and LA12x amps. Of course, we've measured the SB28 and the KS28 to see the difference in frequency response. The green measurement is the SB28 and the blue measurement is the KS28. I have the 3db level differences not tested (the KS28 would go 3db harder as the SB28 according to the manufacturer), I believe that, I'm mainly talking about the frequency response. To find out what's happening in the presets and what's happening in the cabinets, I've pushed some of the presets and cabinets (pure to find out here, of course, it's not wise to go live). Orange is the SB28 preset on the KS28. In the measurement where you see blue and orange together, you can see that the real sub in the presets is the same, but the KS28 originates more low (you can see in the measurement where green and blue are together), so this is the efficiency / construction of the cabinet / speaker and not the preset. In addition, the KS28 of itself 3db is less 63hz, because in the preset they are equal but not in output. In short, the KS28 is much better in the real layer, but slightly less in the middle (around 63hz), so if the KS28 in this area also really gets that 3db harder, the question is, in the low area (36hz and below ) this is clear. Red is the SB218 measurement preset on a SB28. Unfortunately, no SB218 was available to test it. But we can see that something else happens in the preset. In the "high area" of the SB218, it is assumed that this has been done to correct the cabinet (I have not been able to test this). This story may well explain the fact that many technicians believe that the SB218 sounds more musical because it may have more efficiency in the high area and thus the SB28 less and possibly the SB28 seems to sound tighter and thus the SB28 is more favorite in the electronic music. But well, this is guessing because I have not been able to check this. Pink is the SB28 preset on the KS28 + what EQ, 36hz 1.4db with it and 170hz 2db (as shown in the LA Network Manager's picture). In the measurement, you see that the frequency and phase response are substantially equal between the SB28 and the KS28 with SB28 preset (and the EQ). In short, in the KS28 preset there is 1.4db less 36hz and 2db more 170hz while both subs at those two frequencies do as much. In short, the KS28 has more efficiency at 36hz and less efficiency at 170hz than the SB28. Conclusion: I think the freq. SB28's response looks more beautiful, but the KS28 is broken in the real sub (36hz and below) and has a very high efficiency. The question is if the KS28 is about the 63hz area and above that actually goes that 3db harder as claimed, as it has less efficiency than the SB28, in the extremely low area (under 36hz) the KS28 is definitely the 3db harder . But good, end conclusion: the KS28 is a brutal and fat sub ... !! Ohhja, just for sure: I've tested this with 1 single sub, what happens with multiple cabinets together, that's maybe another story ...
CS-Audio Netherlands
CS-Audio Netherlands
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