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[Fernando Lopez]

First Hand I did not see any difference between the subs but I will measure them over the weekend

[Frederik Rosenkjær]

First Hand I did not see any difference between the subs but I will measure them over the weekend

I'm sure it's just an illusion. The same thing is happening (for me, at least), to a slightly lesser degree, with the TH-MINIs on the right.

[Art Welter]

4 ohms is standard. You can get 8. Ohms on special order

Ivan,

The current TH-118 4 ohm PDF seems to show a  picture of a TH-115, not a B&C BC-18SW115 or Eighteen Sound 18NLW9600 .

No big deal, the boxes are the same outside...

However, the chart does not agree with the written spec.:
Sensitivity @ 1M ................................................................ 108 dBSPL
.................................................................. 112 dBSPL @ 100 Hz max
........ (Referenced to 2.83V @1M 1/2 space, measured as 28.3V @ 10M)

The chart title states 100 watts at 10 meters, which should be referenced to 20 V,   28.3 volts would be +3 dB, 200 watts.
The chart also shows 100 Hz to be about 107 dB, not 112 dB as in the spec.

I would assume the chart saying 100 watts is a typo ( the 4 ohm TH-115  has the same typo) but the 100 Hz inconsistency may mean the written spec is for a different 18” speaker than the chart.

Is the chart for the  B&C BC-18SW115 or Eighteen Sound 18NLW9600 ?
100 watts, (20 volts) or 28.3 volts (200 watts?

[Tim Talbot]

You need to think in terms of dB-not wattage.  Especially at higher wattages.

If you are running a rig within 1.7dB of max-you need a larger rig.

Very wise words  and if you want more SPL / output etc add more cabinets rather than buying bigger amps...

[Ivan Beaver]

Ivan,

The current TH-118 4 ohm PDF seems to show a  picture of a TH-115, not a B&C BC-18SW115 or Eighteen Sound 18NLW9600 .

No big deal, the boxes are the same outside...

However, the chart does not agree with the written spec.:
Sensitivity @ 1M ................................................................ 108 dBSPL
.................................................................. 112 dBSPL @ 100 Hz max
........ (Referenced to 2.83V @1M 1/2 space, measured as 28.3V @ 10M)

The chart title states 100 watts at 10 meters, which should be referenced to 20 V,   28.3 volts would be +3 dB, 200 watts.
The chart also shows 100 Hz to be about 107 dB, not 112 dB as in the spec.

I would assume the chart saying 100 watts is a typo ( the 4 ohm TH-115  has the same typo) but the 100 Hz inconsistency may mean the written spec is for a different 18” speaker than the chart.

Is the chart for the  B&C BC-18SW115 or Eighteen Sound 18NLW9600 ?
100 watts, (20 volts) or 28.3 volts (200 watts?

Thanks for catching those errors.

That is part of the danger of "copy/paste".

The IT guy used a photo of a TH115 because it looks the same as the TH118 (until you look closely at the driver HA-HA).

He also used the TH115 spec sheet as a template (because so much is the same) and didn't change the line in the specs about 112dB SPL at 100Hz.  The max db is listed correctly @134Hz.  I have given him the change for that particular line.

The 100 watts on the TEF plot is an error on my part (that darm template idea again).   You are correct that it should state 28.3V @ 10m (which is not 100 watts into the TH118's impedance).  I will change that.

The drivers are practically identical in terms of response in the cabinet.  With the Tapped horn, the cabinet is the biggest contributor to the output and response.

[Art Welter]

Thanks for catching those errors.

That is part of the danger of "copy/paste".

The IT guy used a photo of a TH115 because it looks the same as the TH118 (until you look closely at the driver HA-HA).

He also used the TH115 spec sheet as a template (because so much is the same) and didn't change the line in the specs about 112dB SPL at 100Hz.  The max db is listed correctly @134Hz.  I have given him the change for that particular line.

The 100 watts on the TEF plot is an error on my part (that darm template idea again).   You are correct that it should state 28.3V @ 10m (which is not 100 watts into the TH118's impedance).  I will change that.

The drivers are practically identical in terms of response in the cabinet.  With the Tapped horn, the cabinet is the biggest contributor to the output and response.

Ivan,
Thanks for clearing that up.
One other point you may want to address is the issue of the parameter changes between a 4 ohm and 8 ohm speaker.
As you said, "With the Tapped horn, the cabinet is the biggest contributor to the output and response."

Yesterday, doing a simulation, I found that the four ohm version of the BC18SW115 was 2 dB less sensitive in the same design.
If correct, it would mean the four ohm version would only net 1 dB gain using twice the power.
I was  surprised how much the TS parameters changed between the 4 and 8 ohm version.
Charlie Tappa is checking with the factory to see if the 4 ohm specs are indeed correct.

Since the 4 ohm version is less sensitive, more power would go to heat, which probably would cause more thermal limiting, net effect being that the four ohm version may actually have less output than the eight ohm no matter how much power it is given.

I will be the first to agree with you that actual measurement trumps any simulation, but differences between the speaker impedance and actual in cabinet response may have "slipped through the cracks" in to the specs too.

I have not seen an actual 8 vs 4 ohm chart on either the TH-115 or TH-118, have they been made, or was the 8 ohm chart just raised by 3 dB when the 4 ohm variant became available?

[Ivan Beaver]

Ivan,
Thanks for clearing that up.
One other point you may want to address is the issue of the parameter changes between a 4 ohm and 8 ohm speaker.
As you said, "With the Tapped horn, the cabinet is the biggest contributor to the output and response."

Yesterday, doing a simulation, I found that the four ohm version of the BC18SW115 was 2 dB less sensitive in the same design.
If correct, it would mean the four ohm version would only net 1 dB gain using twice the power.
I was  surprised how much the TS parameters changed between the 4 and 8 ohm version.
Charlie Tappa is checking with the factory to see if the 4 ohm specs are indeed correct.

Since the 4 ohm version is less sensitive, more power would go to heat, which probably would cause more thermal limiting, net effect being that the four ohm version may actually have less output than the eight ohm no matter how much power it is given.

I will be the first to agree with you that actual measurement trumps any simulation, but differences between the speaker impedance and actual in cabinet response may have "slipped through the cracks" in to the specs too.

I have not seen an actual 8 vs 4 ohm chart on either the TH-115 or TH-118, have they been made, or was the 8 ohm chart just raised by 3 dB when the 4 ohm variant became available?

I have not measured an 8 ohm TH118, as the standard model is 4 ohms.  8 ohms would be a special order.  So the measurements are on the 4 ohm version with 28.3V input.

To be honest I cannot remember exactly about the TH115 and whether it was "raised" or remeasured-that was awhile ago-I will have to check into that.

The 4 ohm TH115 is sonically around 3dB greater than the 8 ohm.  Definately not 1 dB or so.

[Art Welter]

I have not measured an 8 ohm TH118, as the standard model is 4 ohms.  8 ohms would be a special order.  So the measurements are on the 4 ohm version with 28.3V input.

To be honest I cannot remember exactly about the TH115 and whether it was "raised" or remeasured-that was awhile ago-I will have to check into that.

The 4 ohm TH115 is sonically around 3dB greater than the 8 ohm.  Definately not 1 dB or so.

Good to know  the TH-115 4 ohm is sonically around 3dB greater than the 8 ohm .

Would be interesting to find if the BC18SW115-4 is also sonically 3 dB greater than the BC18SW115-8 in the TH-118.

Is the TH-118  measurement on the PDF spec sheet the BC18SW115-4 or the 18 Sound 18NLW9600?

Have you or DSL measured both?

[Art Welter]

Good to know  the TH-115 4 ohm is sonically around 3dB greater than the 8 ohm .

Would be interesting to find if the BC18SW115-4 is also sonically 3 dB greater than the BC18SW115-8 in the TH-118.

Is the TH-118  measurement on the PDF spec sheet the BC18SW115-4 or the 18 Sound 18NLW9600?

Have you or DSL measured both?

Anybody measured or have subjective opinions of the TH-118 loaded with BC18SW115-4 compared to the 18 Sound 18NLW9600-4?

[Ivan Beaver]

Anybody measured or have subjective opinions of the TH-118 loaded with BC18SW115-4 compared to the 18 Sound 18NLW9600-4?

Subjectively the B&C has a bit more "punch" in the TH118 than the 18 Sound.

[ProSoundWeb Community]