I'd be quite surprised if that's the case, as the TH118 has a noticeably lower resonance frequency. In fact, I remember that there was a lot of discussion here about how TD may have managed to achieve such a low resonance frequency in a box that size.
From the low peaks in the impedance curve, I'd say that the TH118 is partly stuffed. The TH18 isn't stuffed at all, so that will impact the FR too.
Well I know you saw this, as the very next post was yours. The measurement is an attachment so I couldn't show it here so I just saved it and rehosted it so I could show it here. Green is Danley TH118 and red is diy Xoc TH18. Since this was posted back in April I thought the controversy regarding something special going on in the Danley cab was settled, there's nothing going on there and if Danley is showing a low resonance frequency it's likely got to do with how he measured it.
This guy measured both of these in the same spot - up on a wall in a room, so not ideal but perfectly fine for making comparisons. The post containing the measurement is here - http://www.diyaudio.com/forums/subwoofers/190635-th-18-flat-35hz-xoc1s-design-221.html#post4698461
Here's a copy of the picture of the measurement -
This guy measured both of these in the same spot - up on a wall in a room, so not ideal but perfectly fine for making comparisons. The post containing the measurement is here - http://www.diyaudio.com/forums/subwoofers/190635-th-18-flat-35hz-xoc1s-design-221.html#post4698461
Here's a copy of the picture of the measurement -
An externally hosted image should be here but it was not working when we last tested it.
This post shows how he set the cabs up, I think this reflects the position they were in when measured, although I can't guarantee that. This might be where he is using them now but not where he took the measurement in the last post, I'm not sure, but he does show a mic in front of one of the cabs.
http://www.diyaudio.com/forums/subwoofers/190635-th-18-flat-35hz-xoc1s-design-226.html#post4740486
http://www.diyaudio.com/forums/subwoofers/190635-th-18-flat-35hz-xoc1s-design-226.html#post4740486
Going by the scale in the picture, the TH118 has 2dB less output at 50 Hz and 1~2dB or so greater output at 40 Hz and below. This suggests a lower tuning. There's also more significant differences above 100 Hz that are likely caused by differences in internal layout of the horns. And going by the picture, that's probably not the best way to measure the FR of a TH the size of the TH118. Or the TH18 for that matter.
TD's impedance measurement shows significantly lower impedance peaks than expected, along with the low resonance frequency. Based on the stated measurement technique (open field, 10M, 28.3V), I can't think of anything about that measurement process that would significantly shift both the resonance frequency and the magnitude of the resonance peaks downwards. Using a driver with a very low Qms might produce lower impedance peaks, but won't explain the low resonance frequency.
TD's response curve for the TH118 can be seen here - http://www.danleysoundlabs.com/danley/wp-content/uploads/2012/04/TH-118-spec-sheet.jpg
Or it could suggest the mic or the speaker wasn't in the exact same position, even a couple inches difference could cause that. I do not agree with your assessment, these measurement are about as close to a perfect overlay as you can get from about 24 - 70 hz. Even if he measured the same speaker twice (setting up the measurement twice) you could expect to see differences like this.
This I agree with.
Also agree, but for making relative comparisons it's fine.
I don't really care what Danley's measurement shows, I don't really trust it.
If you want to talk to the guy that did these measurements, I recognize the name, I think he's active on avs and the data-bass forum too if you can't get in touch with him here.
You can request impedance measurements and you can ask him if there's stuffing in the TH118. I can pretty much guarantee he's going to say no, as the measurements of the TH18 and TH118 are about as close as a perfect overlay as you could possibly get in the subwoofer frequencies.
Let me know if you don't feel like contacting him, then I will attempt to get him to answer some questions.
The HornResp sim for the TH18 suggests a resonance frequency around 35~36 Hz, significantly higher than that of the TH118.
Regardless, the previous discussions IIRC had to do with the TH118 being tuned SEVERAL hz lower than the sims indicated - this is clearly not the case in the measurements here - the TH118 has a bit more path length than the Xoc1 TH18 which may account for maybe 1 hz or so lower tuning, but sims don't lie - this commercial cab is not significantly different than the Xoc1 TH18.
If you sim them both accurately you will find that they are not significantly different. We've gone over this and I don't really want to rehash it.
If you don't want to contact the guy that took the measurements I will. Let me know. We'll see if we can get you an impedance measurement of both cabs so you can see that they are not significantly different.
...and then
So, you trust the measurements of a guy but you're not even sure he put the mike in exact same position for the measurement comparisons (which would then render the comparison totally invalid, of course), but you don't trust that of a well-known person in the pro audio field that actually popularized the TH design and who details the process used to measure the TH118?
Well, I think I'll just give that the due attention it deserves
.So, you trust the measurements of a guy but you're not even sure he put the mike in exact same position for the measurement comparisons (which would then render the comparison totally invalid, of course), but you don't trust that of a well-known person in the pro audio field that actually popularized the TH design and who details the process used to measure the TH118?
Well, I think I'll just give that the due attention it deserves
That's a spec sheet used for marketing purposes. I'm sure the measurements are done carefully to make the product look good. On the same spec sheet it lists this nominal 4 ohm cab (which means the Re is less than 4 ohms) sensitivity at 2.83V. This makes no sense, he's listing sensitivity at almost 3 watts. And he also lists the sensitivity at the height of the big peak at 138 hz. WTF is that? it's not even in the passband and it's a peak, not even remotely useful to look at sensitivity at that frequency so why is it even there? Marketing.
Let's give this marketing document the due attention it deserves. None.
Maybe the marketing dept did stuff a few handfuls of stuffing in there for the measurement. But there's none in the commercial product. There's a guy that has this product (or at least had it) so why not just talk to him instead of arguing with me?
Last edited:
Um, SENSITIVITY is always measured with reference to voltage. That's how it's defined, JAG. It is EFFICIENCY that's measured in terms of watts. And while he gives the sensitivity at 138 Hz, he also gives the passband sensitivity. It's the line right above - did you miss it?
That doesn't explain why he decided to measure all his products at 2.83V when most of them (maybe all of them) are well under 8 ohms, most are a 4 ohm nominal load. So no reason to spec sensitivity at 2.83V, which gives almost 3 watts into a 3 ohm load. It's done this way to get a high sensitivity spec for people who compare to other products that are measured at whatever voltage it takes to achieve 1 watt.
I did not miss it, I'm just questioning the audacity to even mention the 2.83V sensitivity of a 3 ohm product at a peak outside the passband. This is marketing. People like us can read the spec sheet and know what it really says, but it's not intended for people like us, it's meant to trick people that are comparing other products that are not measured in this way.
If DSL is comfortable taking these liberties on the spec sheet I have no doubt that the measurement may have been manipulated in a similar fashion, to show the product in the best light.
Anyway, there's not much point in discussing this. I'll ask the guy if he can take an impedance measurement of both cabs (if he still has them both) being careful to place them in the same spot for the measurement. I'll also ask him if there's any stuffing in there (there's not).
I wouldn't be surprised if most manufacturers do that. It's very simple to measure input voltage into a speaker, and it will not vary with frequency if it's a good amplifier. Not so easy to measure input wattage, which varies with the speakers' impedance and therefore also varies with frequency. And I'll bet that any manufacturer that does quote a measured efficiency actually measured the speaker's sensitivity then did the mathematical conversion to derive so-called "reference" efficiency from sensitivity.
Good idea.
That might be difficult as a there's a good section of the horn that's not visible unless you send a camera up around the bends to check. Anyway I simmed the impact of stuffing on the TH18 sim, and it looks like any level of stuffing that reduces the resonance frequency and drops the magnitude of the impedance peaks also significantly alters the horn's frequency response at the upper end of its passband. So the mystery remains...
Last edited:
Some manufacturers do that, and some play much more devious tricks. We've all seen $100 woofers with no specs except "1000 watts" written on the duscap in bold letters, and car amps that say 1000 watts that have a 20 amp fuse. I don't condone any of it. Sensitivity should be specified at the voltage it takes to produce 1 watt at the cab's minimum impedance, or at worst 1 watt into the nominal impedance.
We've discussed all this in the past, I'm not going to do it again. This is one of only two things we haven't agreed about IIRC. And discussing these things does nothing but create unnecessary animosity. There's no point in that, I respect your input on the forum and agree with you on over 99 percent of topics, so let's just agree to disagree on this.
I've already sent the guy a PM to find out if he's willing to discuss these designs. If he doesn't answer here I'll try to track him down in other forums.
I got an answer already - he doesn't have the Danley cab onhand anymore, it's in a permanent installation in a different city. So no impedance measurements will be forthcoming.
I also asked a series of other questions about the driver used, measurement conditions and stuffing. He didn't think there was any stuffing, but as you noted it's impossible to see the entire horn path.
So unfortunately that didn't answer much. He's a nice guy if you have any questions for him.
I also asked a series of other questions about the driver used, measurement conditions and stuffing. He didn't think there was any stuffing, but as you noted it's impossible to see the entire horn path.
So unfortunately that didn't answer much. He's a nice guy if you have any questions for him.
hello
here are the results requested but is important to highlight that the drivers have different powers and due to AC power supply + amp i will just use the speakers till 600W. In addition, there is no price diference now a days from a driver with 600W or 1200W at my market.
First of all the T/S parameters for all drivers involved on the simulation
click here for larger image: https://s10.postimg.org/6du36zhmx/T_S_data.png
The results for max power (the graphic didn't change much the shape)
click here for larger image: https://s11.postimg.org/pwllgm2s3/TH18_results_MP.png
regarding the displacement something wear comes to light, all drivers even the original one considered by Xoc1 don't have enough Xmax to allow the max power output and even reducing the power, to the level I intent to use, the simulation still shows more displacement them the drive has. This is confusing me.
Displacement results for 18LW2400
click here for larger image: https://s13.postimg.org/ejwtd972f/TH18_18_LW2400_MP_fail1.png
Displacement results for KSPA 18-1200
click here for larger image: https://s21.postimg.org/xuj646o9j/TH18_KSPA_18_1200_fail1.png
Displacement results for SUB-800
click here for larger image: https://s18.postimg.org/cw1am6auh/TH18_SUB_800_fail1.png
Displacement results for HPX2180
click here for larger image: https://s14.postimg.org/d8x08fkip/TH18_HPX2180_fail1.png
here are the results requested but is important to highlight that the drivers have different powers and due to AC power supply + amp i will just use the speakers till 600W. In addition, there is no price diference now a days from a driver with 600W or 1200W at my market.
First of all the T/S parameters for all drivers involved on the simulation
An externally hosted image should be here but it was not working when we last tested it.
click here for larger image: https://s10.postimg.org/6du36zhmx/T_S_data.png
The results for max power (the graphic didn't change much the shape)
An externally hosted image should be here but it was not working when we last tested it.
click here for larger image: https://s11.postimg.org/pwllgm2s3/TH18_results_MP.png
regarding the displacement something wear comes to light, all drivers even the original one considered by Xoc1 don't have enough Xmax to allow the max power output and even reducing the power, to the level I intent to use, the simulation still shows more displacement them the drive has. This is confusing me.
Displacement results for 18LW2400
An externally hosted image should be here but it was not working when we last tested it.
click here for larger image: https://s13.postimg.org/ejwtd972f/TH18_18_LW2400_MP_fail1.png
Displacement results for KSPA 18-1200
An externally hosted image should be here but it was not working when we last tested it.
click here for larger image: https://s21.postimg.org/xuj646o9j/TH18_KSPA_18_1200_fail1.png
Displacement results for SUB-800
An externally hosted image should be here but it was not working when we last tested it.
click here for larger image: https://s18.postimg.org/cw1am6auh/TH18_SUB_800_fail1.png
Displacement results for HPX2180
An externally hosted image should be here but it was not working when we last tested it.
click here for larger image: https://s14.postimg.org/d8x08fkip/TH18_HPX2180_fail1.png
That's fine, but if things improve for you and you end up in a situation where you have better AC power and can afford a better amp, it's nice to know how the speakers will do with that. Behringer Inukes are a good budget choice and if you get the dsp version you don't have to buy extra dsp, it's very affordable.
The curve shape won't change at all when you change power level, it will rise or fall in spl but won't change shape.
That doesn't sound right. Post your input screen and make sure you show how much power (Eg) you are using to get these results.
here is the input data @8ohm (97,98v for 1200W and it was 2,83V when the power was 1W)
An externally hosted image should be here but it was not working when we last tested it.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.