FTRCelestion FTR15-4080FD and THAM-15 - Page 2 - diyAudio
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Old 26th March 2013, 11:34 PM   #11
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Quote:
Originally Posted by stinems View Post
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.

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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.

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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.
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Old 26th March 2013, 11:48 PM   #12
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Quote:
Originally Posted by OMNIFEX View Post
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 1990s 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.

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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
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Old 28th March 2013, 12:40 PM   #13
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I can find virtually nothing on these drivers. It seems QSC uses some variant of them in some of their powered speakers.
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Old 1st April 2013, 10:36 PM   #14
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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
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Old 2nd April 2013, 02:34 PM   #15
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Quote:
Originally Posted by ghettosynth View Post
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.

Last edited by weltersys; 2nd April 2013 at 02:43 PM.
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Old 3rd April 2013, 11:10 AM   #16
djk is offline djk
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Click the image to open in full size.

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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Last edited by djk; 3rd April 2013 at 11:39 AM.
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Old 3rd April 2013, 12:08 PM   #17
Djim is offline Djim  Netherlands
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Hi djk,

????????Re????????

2226 = 5 Ohm
130A = 5,7 Ohm
LE15a = 8,8 Ohm
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Old 3rd April 2013, 12:21 PM   #18
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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.
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Old 3rd April 2013, 11:55 PM   #19
Djim is offline Djim  Netherlands
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Hi djk,

Since you haven't showed any impedance plot, I can only judge by using Re. Those values suggest that all three drivers have a 'nominal' of 8 Ohms.

Last edited by Djim; 3rd April 2013 at 11:58 PM.
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Old 4th April 2013, 12:58 AM   #20
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Hi!

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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,
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