FTRCelestion FTR15-4080FD and THAM-15

FTRCelestion FTR15-4080FD and THAM-15 (Bad Idea? 6mm xmax)

Hi all,

After spending hours with HornResp trying to get a 12" TH to look more like the THAM-15 I gave up and decided to just build a set of THAM-15s. Parts Express recently had a sale on celestions so I took advantage of that and ordered two Celestion FTR15-4080FD drivers which seemed to sim well enough.

Well, to make a long story short, PE had erroneously listed the xmax at 10mm when, in fact, it's 6mm. They've agreed to pay for the return shipping owing to their error, however, before I send them back I want to make sure that I'm not overreacting.

Does anyone have any experience, or lacking that, simply thoughts/opinions with these drivers in a TH? My sims suggest that the xmax difference will result in a dramatic reduction in SPL.

tnx,
gs
 
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Well, to make a long story short, PE had erroneously listed the xmax at 10mm when, in fact, it's 6mm.
Does anyone have any experience, or lacking that, simply thoughts/opinions with these drivers in a TH? My sims suggest that the xmax difference will result in a dramatic reduction in SPL.
Your sims are correct.

A driver like the BC15TBX100 costs more because it can displace nearly as much air as two of the FTR15-4080FD, a 6 dB increase in clean SPL.
If you want small and loud (and known high quality), gotta pay the piper.
That said, you might look at displacement for dollar comparisons, there are some car drivers that have a lot of bang for the buck.
 
Your sims are correct.

A driver like the BC15TBX100 costs more because it can displace nearly as much air as two of the FTR15-4080FD, a 6 dB increase in clean SPL.
If you want small and loud (and known high quality), gotta pay the piper.
That said, you might look at displacement for dollar comparisons, there are some car drivers that have a lot of bang for the buck.


Sure, but the BC15TBX100 only has a 9mm xmax. I purchased these becasue PE said that they had 10. The next step up Celestion has 8mm xmax and (was) $100 less than the B&C. I certainly would have paid the extra $45 per driver to get something that was going to work. I only went with the driver that I did because it seemed well suited based on the data that I had.

In sim I get about 123dB or so from the Celestion and 126dB from either the larger Celestion or the BC15TBX100.
 
I'll note that I don't have real-world experience with either driver, but...

I don't think the Celestion is as much of a dog as you might think. Not to take anything away from the B&C 15TBX, which I agree is a monster in its own right, I'm not so sure its such a huge leap ahead of your Celestion. Celestion seems to use the old school method of xmax rating: (VClength-Gap)/2 (for overhung). B&C, Faital, and others have gone away from that since their advancements in motor design, apparently, have made that too conservative of a thumbrule (at least for the marketers). A look at the Celestion's impedance curve will tell you that is no slouch of motor. Not sure if it has demod ring(s) like the B&C, but its quite flat and non-inductive. A bit more research shows the FTR series having improved cooling mechanisms too.

In a nutshell, my guess is the 6mm of xmax on the Celestion is a fairly conservative rating.

Cheers,
Sam
 
I'll note that I don't have real-world experience with either driver, but...

I don't think the Celestion is as much of a dog as you might think. Not to take anything away from the B&C 15TBX, which I agree is a monster in its own right, I'm not so sure its such a huge leap ahead of your Celestion. Celestion seems to use the old school method of xmax rating: (VClength-Gap)/2 (for overhung). B&C, Faital, and others have gone away from that since their advancements in motor design, apparently, have made that too conservative of a thumbrule (at least for the marketers). A look at the Celestion's impedance curve will tell you that is no slouch of motor. Not sure if it has demod ring(s) like the B&C, but its quite flat and non-inductive. A bit more research shows the FTR series having improved cooling mechanisms too.

In a nutshell, my guess is the 6mm of xmax on the Celestion is a fairly conservative rating.

Cheers,
Sam


Ok, so when we measure the 15TBX100 by the same method I get (25-12)/2 = 6.5mm and the 15PS100 has (21-11)/2 = 5mm. What PE must be reporting is what B&C refers to as XVAR which is determined by the driver's ability to reproduce a sine wave under a predetermined distortion level, yes?

So with the B&C drivers this allows for a 60% increase over xmax. Of course, I can't assume that the Celesition's will perform the same way, but even if they can achive half that at say 30% over xmax, then the xvar rating of the celestion will be similar to the lower priced B&C. It seems to me that it's probably reasonable to assume that the lower cost celestion will behave similarly to the 15PS100 and the higher cost celestion will behave similarly to the 15BTX100 with respect to excursion and power handling.

By that, I simply mean that, given that some people have been reasonably happy with the 15PS100 in the THAM-15, that I would probably be reasonably happy with the Celestion. Or, said differently, that any difference between the Celestion and the 15PS100 will be marginal at best?

I'm not looking for absolute answers here, just a seat of the pants comparison to decide whether the Celestion will perform adequately in the THAM-15. I can certainly send them back and get the 15PS100, or, spend twice as much and get the 15TBX100.

At the end of the day, we're talking about $300 and I've blown more than that in a single weekend just having a good time. I don't need the ultimate performance, I was just concerned that the driver I chose was severely inappropriate for the application. It sounds like I should have purchased the higher priced Celestion, and I might still do that, but I'm not sure if it's worth the hassle returning the lower cost drivers. The next model up also sims well and has a stated xmax of 8mm, assuming that xvar is greater, this is probably comparable to the 15BTX100.

I will be using these with a pair of JBL SR4722 tops (not SRX). They are rated at 600 watts but, IIRC, they really only take about 300 or so. I was planning on driving the subs in 4 ohm bridged mono with about 2kw.

tnx,
gs
 
I'm not looking for absolute answers here, just a seat of the pants comparison to decide whether the Celestion will perform adequately in the THAM-15. I can certainly send them back and get the 15PS100, or, spend twice as much and get the 15TBX100.

The next model up also sims well and has a stated xmax of 8mm, assuming that xvar is greater, this is probably comparable to the 15BTX100.
You can look through B&Cs specs, you will find that Xvar is not some linear relationship to Xmax, it varies with the magnet structure and coil design. Some have hardly any difference, some quite a bit.

You can't assume Xvar specs on other unmeasured drivers. Well, you can, but they would only be guesses.

I have no experience with Celestion (other than hearing Marshall stacks :rolleyes:) but my experience in comparing Eminence to B&C is the B&C at Xvar have less distortion than the Eminence at Xmax.

If that is true with the Celestion, paying double for nearly double (6 to 11) the usable excursion is worth it, if you want the maximum LF potential from a small cabinet.
 
You can look through B&Cs specs, you will find that Xvar is not some linear relationship to Xmax, it varies with the magnet structure and coil design. Some have hardly any difference, some quite a bit.

You can't assume Xvar specs on other unmeasured drivers. Well, you can, but they would only be guesses.

I get that, which is why I'm asking questions here.

I have no experience with Celestion (other than hearing Marshall stacks :rolleyes:) but my experience in comparing Eminence to B&C is the B&C at Xvar have less distortion than the Eminence at Xmax.

Ok, good to know.

If that is true with the Celestion, paying double for nearly double (6 to 11) the usable excursion is worth it, if you want the maximum LF potential from a small cabinet.

Right. Are these Celestion pro drivers new? I'm finding very little information about them on the web?
 
If I had to guess I think PE misread the datasheet for the Celestion and transcribed the 10mm gap depth listed right below the 6mm xmax.

You're right, I think the 4080HDX is intended for subwoofer duty more than the 4080FD which, given its upper end response and lower moving mass, is more of a midbass with improved bass capabilities.

Architecturally, I'd say the 4080FD is at least on par with the 15PS100 though. Doesn't have triple roll surround, but it has a funky double roll ('flexirol'). Both have a double spider, 4" copper voicecoil on a glass former. I'd bet the 4080FD has an edge in motor cooling and inductance linearity over the 15PS100.

If I were you I'd give the Celestion a try. How is PE's return policy on slightly used driver, or one that didn't live up to your expectations? Would they at least refund towards the B&C if the Celestion doesn't work out?

By the way, from B&C's website:
Evolution is a process that affects not only products, but also their technical specifications. Constant advances in research provide more and more precise methods to measure the performance of loudspeakers, and describe their features. Thiele – Small parameters have become the universal language for describing loudspeaker behavior in the small signal domain. Nevertheless, they comment little on the working limits of loudspeakers in the large signal regime.

These limits are customarily indicated by Xmax, the maximum linear excursion. This value is typically measured according to the AES2-1984 standard, corresponding to a maximum of 10% total harmonic distortion (THD) with a sinusoidal signal (though most manufacturers, including B&C, now typically provide data for Linear Mathematical Xmax, not measured Xmax). Recent research shows that this method can yield ambiguous results, and even different numerical values for the same loudspeaker. The main limit of this measurement is that it looks at the output signal instead of the physical features of the driver itself. On the contrary, the most up-to-date instruments for distortion analysis can measure the variations in loudspeaker parameters when they are fed with high-level signals. In this way, an excursion limit can be fixed, beyond which the parameter’s variation becomes excessive.

The “X var” value reported in our data (generally after the traditional “Xmax” value) is measured this way. Beyond this excursion limit, the magnetic field seen by the voice coil, or the total suspension compliance, or both, drops to less than 50% of their small signal value, producing high distortion levels, strong variations from small signal behavior and power compression. The new technique yields different results from the standard measurement based on THD. B&C Speakers believes that this added information gives a more accurate and reliable description on loudspeakers behavior in actual operating conditions.


Cheers,

Sam
 
The “X Var” is only by B&C where everyone else will state xmax and/or xmech. This means using the “X Var” by B&C will not enable you to make a fair comparison amongst other drivers since no other manufacture other than B&C offers “X Var.”

Historically Celestion offered mathematical xmax on there 15 & 18-inch drivers. Mathematical xmax is not popular anymore due to marketing hype. I do recall in the mid 1990’s feeding each Celestion 18-inch driver 600 – 800 watts (and sometimes 1000 watts) which offered a 3.25 mm xmax with no issues of mechanical damage.

I actually still own 6-8 of those old Celestions today, retired, sitting in cardboard boxes.

The choice is really up to you if you know you are going to drive the loudspeaker with no remorse why paying for an extra 3mm is worth it. It is usually better to just use a pair of bins than trying to extract every ounce of SPL (which will guarantee distortion) from one bass bin. Bear in mind the majority lose drivers due to electrical damage (burned up voice coils) than mechanical damage (exceeding the xmechanical limit).
 
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If I had to guess I think PE misread the datasheet for the Celestion and transcribed the 10mm gap depth listed right below the 6mm xmax.

Yep, I saw that as well. Lesson learned on that one.

You're right, I think the 4080HDX is intended for subwoofer duty more than the 4080FD which, given its upper end response and lower moving mass, is more of a midbass with improved bass capabilities.

Architecturally, I'd say the 4080FD is at least on par with the 15PS100 though. Doesn't have triple roll surround, but it has a funky double roll ('flexirol'). Both have a double spider, 4" copper voicecoil on a glass former. I'd bet the 4080FD has an edge in motor cooling and inductance linearity over the 15PS100.

If I were you I'd give the Celestion a try. How is PE's return policy on slightly used driver, or one that didn't live up to your expectations? Would they at least refund towards the B&C if the Celestion doesn't work out?

I think that they don't want to see any installation marks. That said, their customer service has been great so far. I'll reserve my full judgement on that until this is completely resolved, but, they seem understanding and willing to help.

By the way, from B&C's website:

These limits are customarily indicated by Xmax, the maximum linear excursion. This value is typically measured according to the AES2-1984 standard, corresponding to a maximum of 10% total harmonic distortion (THD) with a sinusoidal signal
...
The “X var” value reported in our data (generally after the traditional “Xmax” value) is measured this way.

Yes, I saw that and that's how I was able to conclude, based on B&C's reported gap/coil width, that PE shows XVAR for B&C speakers, and not XMAX. I think that, more than anything, I will go to manufacturer data and double check anything I'm considering using in the future.

At this point I'm leaning towards simply returning them and going back to the drawing board. The main issue is that there simply isn't much information about these speakers so it's difficult to make an informed choice. If I had any experience measuring speakers it wouldn't bother me to be a guinea pig and take some measurements, but, at this point, it's out of my skill range.

The only information I can find on these speakers is a few odd videos. One with an anemic fellow talking about the 21" sub in a voice so quiet you can hardly hear him, another with a salesman who appears to have had too much coffee, and a third with some club install dude who's clearly just hawking his wares.

Maybe these are fine speakers, maybe the next step up is also fine, or in fact, even comparable to the BTX, and maybe they're a good value. Or, as Art points out that I'm just guessing, maybe they fall apart close to xmax. I don't have enough experience or information to be able to ***** them fairly.
 
The “X Var” is only by B&C where everyone else will state xmax and/or xmech. This means using the “X Var” by B&C will not enable you to make a fair comparison amongst other drivers since no other manufacture other than B&C offers “X Var.”

Historically Celestion offered mathematical xmax on there 15 & 18-inch drivers. Mathematical xmax is not popular anymore due to marketing hype. I do recall in the mid 1990’s feeding each Celestion 18-inch driver 600 – 800 watts (and sometimes 1000 watts) which offered a 3.25 mm xmax with no issues of mechanical damage.

Thanks, that's at least an experience anecdote. I'm finding very little on line.

The choice is really up to you if you know you are going to drive the loudspeaker with no remorse why paying for an extra 3mm is worth it. It is usually better to just use a pair of bins than trying to extract every ounce of SPL (which will guarantee distortion) from one bass bin. Bear in mind the majority lose drivers due to electrical damage (burned up voice coils) than mechanical damage (exceeding the xmechanical limit).

To be clear, I'm planning on building a pair of THAM-15s to go with my JBL 4722s. That said, I'm trying to avoid owning (and transporting) two pairs.

Ok, so let me ask a direct question since you have some experience with Celestion drivers. If you could choose between the FTR15-4080HDX which has 8mm of xmax and handles 1000w RMS, (not the one that I ordered, but the one more appropriate for sub duty), or the B&C15PS100 (not the higher powered BTX), which would you choose.

The 15PS100 has 8mm xvar rating and 700w, the 4080HDX 15mm xmax rating, and 1000w. The B&C is well known and respected, the Celestion seems new and either untested or simply not used by hobbyists.

They are roughly the same price and both cost somewhat less than the higher priced B&C.

tnx,
gs
 
Hi All,

Can someone tell me why Celestion would recommend the FD variant of this driver for a horn (traditional, not TH), but not the HDX? Also, based on this website, is it correct to think of the "scoop" and TH as similar with respect to the types of drivers that might work well?

Replace your PA drivers - Celestion - Guitar, Bass & Pro Audio Speakers

tnx
gs
"Traditional" horns used lightweight, low Xmax drivers, back in the day when few amps had the potential to push them beyond Xmax unless driven below Fc.
With amp power cheap, use of lightweight, low Xmax speakers in a horn sacrifices output power for efficiency.
If you are a DJ on a beach using a home stereo amp run off 100' of 18 gauge extension cord, you need all the efficiency you can get.
Otherwise, stiff high Xmax speakers are the way to go.

A scoop has a back chamber, so is somewhere between a TH and a BP.

The Celestion "suggestions" made are so generic as to be largely useless, Hornresp will give you a better idea of output potential, though still will give no information on whether a cone will sound good at high power/excursion extremes in a horn.
 
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djk

R.I.P
2001-02-04 4:23 am
USA
130Avs2226vsLE15A.gif


The 2226 is about 4.5dB less efficient than the 130A. Note how there is no difference in the bass output below about 200hz, the efficiency is determined by the horn, not the driver. The 2226 has a much larger x-max and so will play quite a bit louder below 200hz.

The higher efficiency 130A comes into its own at 500hz, where it has about 4.5dB more output that the 2226.

Rule of thumb: use the lowest efficiency driver that has the highest x-max you can find and a mass corner high enough to reach your intended crossover point.

130A mass corner = 400hz
2226 mass corner = 240hz

The LE15 is 3dB less efficient because it's 16Ω, its mass corner = 180hz, so it has even less output at 200hz and above, but may actually have a touch more output (adjusted for its impedance) below 100hz.

The No% are 7.7%, 3.3%, and 2.6% respectively. X-max is 2mm, 7.62mm, and 4mm respectively (the LE15 is underhung and as such cannot be compared directly to the other overhung drivers). Based on x-max, the maximum output of the LE15 is 6dB higher than the 130A, and the 2226 is 11.6dB higher.

Design and graph by Bill Woods (Yorkville).
 
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djk

R.I.P
2001-02-04 4:23 am
USA
The Re is not a big deal other than it changes the voltage required for 1W.

The impedance in the horn will change things too, the Qes and Qms being different makes the impedance swings different, and not entirely related to the Re (as you would think).

The points about the sensitivity and maximum output are still valid; choose the proper mass corner and x-max for your needs.
 
Hi!

Quote
By that, I simply mean that, given that some people have been reasonably happy with the 15PS100 in the THAM-15, that I would probably be reasonably happy with the Celestion. Or, said differently, that any difference between the Celestion and the 15PS100 will be marginal at best?
Unquote.

No experience with the 15PS100, but with 12PS100 which performs very well in the TH12 when you can beside use it till Pe, the performance of a bass guitar notes played thru the TH are also well defined from 40 to 100Hz, without overexcursion issues, and without any cone correction (impressive as THs suffer from overexcursion ill at Pe).
This performance (defined notes) isn't achieved by much drivers. To me it's a try and error thing beside parameters.

As the 15PS100 apparently has the same motor why not try one.

NB: Build 4 THAM15, sold two and two remain here unused. Tried several drivers innit. To me lacks lows.

Regards,