I thought I would share some measurements of this Tymphany/Peerless DFM-2535-R00-08 1.4" voice coil, 1" exit titanium compression driver with ferrite magnet
Here's the spec sheet, retrieved 01/08/2024 shows the response in a Plane Wave Tube @0.283V:
As well as in a horn:
N.B. The left vertical axis denotes 2.83V/1m ("with LTH102 test horn")... A web search shows... is this the FaitalPRO LTH102 horn ?
Since Tymphany don’t make their own horns (AFAIK), I mounted it onto a SB Audience H225 , a 225mm square 90x70 degree constant directivity horn.
It needs four M6 x 16mm bolts to mount directly only the horn- no modifications or adaptor required:


Now we measure at 0.5m (to reduce reflections in from floor/ceiling) but plot for 1m (-6dB) in the "standard" 25dB/decade aspect ratio, from 600Hz to 40KHz:
Here are the polar measurements, taken in 10 degree steps, in both the Horizontal and Vertical axis from 0-90 degrees.
This is with a gentle 1V RMS drive level so measurements could be taken down to 500Hz, but SPL plotted for 1m.
The gating is 4ms, so the frequency resolution is approximated below 1KHz.
Here's the polar response, with 1dB demarcations.
Next we use software DSP to flatten with on-axis frequency response and insert a filter for acoustic LR4 1KHz:
86dB@1m seems to be a walk in the park- all harmonics below noise floor of this room:
Here is 96dB , this time with crossover for 800Hz (see post 17)
STRETCH GOAL:
106dB/m
Edit:
01/08/2024 - tidied up. B&W for some, colors for others!
Here's the spec sheet, retrieved 01/08/2024 shows the response in a Plane Wave Tube @0.283V:
As well as in a horn:
N.B. The left vertical axis denotes 2.83V/1m ("with LTH102 test horn")... A web search shows... is this the FaitalPRO LTH102 horn ?
Since Tymphany don’t make their own horns (AFAIK), I mounted it onto a SB Audience H225 , a 225mm square 90x70 degree constant directivity horn.
It needs four M6 x 16mm bolts to mount directly only the horn- no modifications or adaptor required:


Now we measure at 0.5m (to reduce reflections in from floor/ceiling) but plot for 1m (-6dB) in the "standard" 25dB/decade aspect ratio, from 600Hz to 40KHz:
Here are the polar measurements, taken in 10 degree steps, in both the Horizontal and Vertical axis from 0-90 degrees.
This is with a gentle 1V RMS drive level so measurements could be taken down to 500Hz, but SPL plotted for 1m.
The gating is 4ms, so the frequency resolution is approximated below 1KHz.
Here's the polar response, with 1dB demarcations.
Next we use software DSP to flatten with on-axis frequency response and insert a filter for acoustic LR4 1KHz:
86dB@1m seems to be a walk in the park- all harmonics below noise floor of this room:
Here is 96dB , this time with crossover for 800Hz (see post 17)
STRETCH GOAL:
106dB/m
Edit:
01/08/2024 - tidied up. B&W for some, colors for others!
Last edited:
With a 7 db drop from 2 khz to 10 khz, and 3 db drop from 1200 to 2000, I will not use it all. I can still hear to 14 khz.But's that's ok- you'll probably only use this horn above 1Khz anyway.
An N151M-8 is only $95 and vendor data suggests it drops 0 db between 2k & 10k. 5 db drop 10k to 15k.
Thanks for the work.
indianajo have you never worked with a waveguide/horn before? The are generally tilted as above and after simple crossover filtering are brought back to flat. This is normal. When that is done, you will only be left with 2 dB dip at 2.5khz and a 4 dB dip at 10khz.
I concur with @augerpro
When thinking about tuning it for neutral response, the normalised frequency response graph (the bottom right of the 4) is the one to look at.
Think "when I tune the on-axis flat... this is what happens to the off axis"
For sure there's a dip at 14KHz. That's a little fly in the ointment, I agree.
It seems to be created by the horn, because it's not as severe in the vertical response. Though In comparative terms, I'd rather at dip in the top octave around 14Khz, than one at 10KHz:
Reference:
https://www.erinsaudiocorner.com/loudspeakers/jbl_m2/
I might take a look at the H225... and see how it compares....
For those wanting the smoothest response, I would go with the custom 3D printed or CNC'ed ST260 waveguide by @mabat
When thinking about tuning it for neutral response, the normalised frequency response graph (the bottom right of the 4) is the one to look at.
Think "when I tune the on-axis flat... this is what happens to the off axis"
For sure there's a dip at 14KHz. That's a little fly in the ointment, I agree.
It seems to be created by the horn, because it's not as severe in the vertical response. Though In comparative terms, I'd rather at dip in the top octave around 14Khz, than one at 10KHz:
Reference:
https://www.erinsaudiocorner.com/loudspeakers/jbl_m2/
I might take a look at the H225... and see how it compares....
For those wanting the smoothest response, I would go with the custom 3D printed or CNC'ed ST260 waveguide by @mabat
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Now compare to SB26ADC in @augerpro 's fantastic waveguides:
https://www.somasonus.net/waveguides
FR traced from:
Augerpro 's 8"x 1.5" waveguide for SBA SB26ADC (sans phase shield)

VS.
DFM2335 in SBA H225:

https://www.somasonus.net/waveguides
FR traced from:
Augerpro 's 8"x 1.5" waveguide for SBA SB26ADC (sans phase shield)

VS.
DFM2335 in SBA H225:

For PA use, the rapid rise in distortion at the bottom of the response at just 1V drive level is a concern- the DFM-2535R00-08 Product Sheet lists Xmax at only .1mm (one tenth of a mm), while most HF drivers have more like .5mm (one half mm).I thought I would share some measurements of this Tymphany Peerless compression driver mounted on a SB Audience H250 (250mm square) 90x60 degree constant directivity horn.
The windowing is 4ms gating, so the frequency resolution is approximated below 1KHz.
But's that's ok- you'll probably only use this horn above 1Khz anyway.
Here's the distortion:
That said, distance between the diaphragm and phase plug specifications (Xmech/Xlim) are hard to find, and Xmax specifications often are derived with different methods.
Without distortion testing at typical PA levels can't say for sure if the excursion would be a concern with a steep 1kHz crossover, but with a noise rating of only 30 watts 1500-1.5Khz, would expect around 120dB may be it's "hard limit", easily exceeded by a typical 10" driver.
Although HF rolloff on a constant directivity horn is to be expected, both your and the SB Audience H250 published polars show it narrows considerably in both horizontal and vertical patterns as frequency increases.
The SB Audience Bianco-44CD-PK driver appears to have almost no HF rolloff on the H250 horn from 1kHz to 15kHz, your DFM-2535R00-08 measurements show about a 7dB drop.
Measurement conditions could account for the differences, testing at just one meter may accentuate the low frequency.
I don't believe the Bianco-44CD-PK could have a .71mm distance between the diaphragm and phase plug and also have response extending that high.
At any rate, for home use a 30 watt HF driver is probably more than enough for most, but for PA use, not so much 😳
Art
You are right @weltersys and @indianajo
I did some fresh distortion measurements this weekend of this compression driver/horn combination to see how well it would actually take my proposed XO. Well 2 things, the top end roll off is indeed real.
Btw It’s also seen on the Tymphany datasheet.
https://products.peerless-audio.com/transducer/438
but I wonder whether the 107dB sensitivity rating by given by Tymphany was for the 1Khz response. If we’re going to do passive crossovers, where one can cut but not boost, I would take the top octave as the true sensitivity.
The second thing is the XO point; it’s much more suitable for an acoustic LR4 closer to 1KHz, than 700 Hz.
And LR2? Fuggedabout it.
I’ll upload the distortion data later
? Mods ? @AllenB
Yes, smooth response but not high sensitivity- probably not PA ready.
Can we move this to the Multi-Way thread?
I did some fresh distortion measurements this weekend of this compression driver/horn combination to see how well it would actually take my proposed XO. Well 2 things, the top end roll off is indeed real.
Btw It’s also seen on the Tymphany datasheet.
https://products.peerless-audio.com/transducer/438
but I wonder whether the 107dB sensitivity rating by given by Tymphany was for the 1Khz response. If we’re going to do passive crossovers, where one can cut but not boost, I would take the top octave as the true sensitivity.
The second thing is the XO point; it’s much more suitable for an acoustic LR4 closer to 1KHz, than 700 Hz.
And LR2? Fuggedabout it.
I’ll upload the distortion data later
? Mods ? @AllenB
Yes, smooth response but not high sensitivity- probably not PA ready.
Can we move this to the Multi-Way thread?
Here is the distortion after the frequency response has been straightened and an acoustic LR2 @1KHz crossover incorporated.
Here is LR4@ 1KHz:
Acoustic LR4 + 10dB louder.
Some impedance compensation may be needed around Fs to bring down the distortion around 600Hz.
TBC...
Here is LR4@ 1KHz:
Acoustic LR4 + 10dB louder.
Some impedance compensation may be needed around Fs to bring down the distortion around 600Hz.
TBC...
In a more perfect world, 1w/1m (or at the specified voltage of 2.83) sensitivity should be the average over the stated frequency range, 1500 - 15000 Hz for the DFM-2535R00-08.but I wonder whether the 107dB sensitivity rating by given by Tymphany was for the 1Khz response. If we’re going to do passive crossovers, where one can cut but not boost, I would take the top octave as the true sensitivity.
107dB is instead the rounded up peak midband sensitivity.
With the chart provided, at least more or less "what you see is what you get" 😉
Distortion looks better than expected, looks like it may exceed ~120dB before reaching 10% THD with a LR4@ 1kHz.
That said, if its product sheet listing Xmax at only .1mm (one tenth of a mm) is correct, there is going to be a very small range between "OK", and "Ouch" 😳
Art
The distortion is likely even lower. I’ve changed my measurement setup:
https://www.diyaudio.com/community/...mnidirectional-microphones-for-diyers.412011/
Hopefully will be able to measure this driver again in weeks to come…
https://www.diyaudio.com/community/...mnidirectional-microphones-for-diyers.412011/
Hopefully will be able to measure this driver again in weeks to come…
Just curious about this in general.The distortion is likely even lower. I’ve changed my measurement setup:
https://www.diyaudio.com/community/...mnidirectional-microphones-for-diyers.412011/
Hopefully will be able to measure this driver again in weeks to come…
There isn't a lot of information on compression drivers, or data is very dated.
I have seen ones that perform many miles better compared to VERY expensive regular dome tweeters.
Yet having an awful lot more headroom and the obvious boost in sensitivity.
I only haven't seen many custom waveguides for compression drivers either?
Measured with HPF acoustic LR4 1KHz, using REW Farina log sine sweep 256K samples x8 repetitions
Sensitivity ~98dB 2.83V (-8dB c.f. 40cm)
-6dB point ~17.4KHz.
Recall polar map with 1dB demarcations:
I suspect this a nice balance of smoothness and sensitivity in an indoor setting. And likely even better in @mabat 's ATH.
@tktran303 Would you mind showing the relative distortion?
Absolute numbers are hard to read + can be pretty concealing at times.
Absolute numbers are hard to read + can be pretty concealing at times.
Let's see measurements again, this time with full range sweeps @1m, which is suitable for HF devices because a reflection-free window of 6ms is enough to cover the entire bandwidth.
First testing at 2.83V to check sensitivity:
Legend marks SPL @10KHz. Please ignore the decimal point- This Omni1 microphone has not calibrated, hence SPL is accurate to only +/-1dB.
I'm going to call it 98dB @10KHz.
Let's flatten the response and measure to some "standards" ...
like 85dB @1m:
Here's the fundamental and harmonics for 85dB @1m:
A different view:
As @b_force suggested- it certainly it easier to read.
for 95dB @1m, I've limited the measurement bandwidth to 800Hz protect this now difficult to replace driver.
Let's put some XO filters in and test them:
85dB with LR4@2KHz:
95dB with LR4@2KHz:
105dB with LR4@2KHz:
Well, what about a 1.5KHz acoustic LR4 XO?
95dB:
Or 1KHz acoustic LR4 crossover,
95dB:
How low can it go?
What about acoustic LR4 @ 800Hz.
95dB:
First testing at 2.83V to check sensitivity:
Legend marks SPL @10KHz. Please ignore the decimal point- This Omni1 microphone has not calibrated, hence SPL is accurate to only +/-1dB.
I'm going to call it 98dB @10KHz.
Let's flatten the response and measure to some "standards" ...
like 85dB @1m:
Here's the fundamental and harmonics for 85dB @1m:
A different view:
As @b_force suggested- it certainly it easier to read.
for 95dB @1m, I've limited the measurement bandwidth to 800Hz protect this now difficult to replace driver.
Let's put some XO filters in and test them:
85dB with LR4@2KHz:
95dB with LR4@2KHz:
105dB with LR4@2KHz:
Well, what about a 1.5KHz acoustic LR4 XO?
95dB:
Or 1KHz acoustic LR4 crossover,
95dB:
How low can it go?
What about acoustic LR4 @ 800Hz.
95dB:
So how that compare to others?
The JBL M2, as measured by www.erinsaudiocorner.com
Obviously this is full system sweep of a 15" woofer + compression driver that is actively driven and has a crossover frequency of 800Hz.
I don't recall whether @bikinpunk measured JUST the compression driver. Did you get a chance Erin?
The disadvantage of judging what HF unit is doing from a full frequency sweep is that there is a uncertainty area above and below the XO frequency. ie. above 800Hz the woofer is contributing, and below 800Hz the compression driver is contributing.
Here's the DFM2335-
Let's bring back some colour so we can compare... sorry @jasdiy
What about the JBL 4367, again measured by www.Erinsaudiocorner.com
Another 15" woofer + compression driver in proprietary waveguide by JBL. This time using passive crossovers and a XO frequency of 700Hz:
Here's the DFM2335:
And before I forget, yes, I do believe that Fs compensation would improve performance in the low end (not shown)
@mabat 's ATH would also improve performance.
The JBL M2, as measured by www.erinsaudiocorner.com
Obviously this is full system sweep of a 15" woofer + compression driver that is actively driven and has a crossover frequency of 800Hz.
I don't recall whether @bikinpunk measured JUST the compression driver. Did you get a chance Erin?
The disadvantage of judging what HF unit is doing from a full frequency sweep is that there is a uncertainty area above and below the XO frequency. ie. above 800Hz the woofer is contributing, and below 800Hz the compression driver is contributing.
Here's the DFM2335-
Let's bring back some colour so we can compare... sorry @jasdiy
What about the JBL 4367, again measured by www.Erinsaudiocorner.com
Another 15" woofer + compression driver in proprietary waveguide by JBL. This time using passive crossovers and a XO frequency of 700Hz:
Here's the DFM2335:
And before I forget, yes, I do believe that Fs compensation would improve performance in the low end (not shown)
@mabat 's ATH would also improve performance.
@tktran303 Voice Coil magazine has a bunch on their website.
Unfortunately only with 104dB @ 1 meter
Unfortunately only with 104dB @ 1 meter
@b_force
Yes. Am aware.
Nothing wrong with standardising for 104dB @ 1m. But putting the mic at 10cm from the horn exposes it to be over 120dB:
If the Listen Inc SCM mic has 1% distortion at 126, then at 120dB it has at least 0.5% distortion, likely H2 dominated.

^^^
The harmonics depicted here may be mix of the signal path. It hard to fathom that a PA driver have this much strain under 4KHz
Reference:
https://audioxpress.com/article/test-bench-b-c-speakers-de111-8-1-pro-sound-compression-driver
Yes. Am aware.
Nothing wrong with standardising for 104dB @ 1m. But putting the mic at 10cm from the horn exposes it to be over 120dB:
If the Listen Inc SCM mic has 1% distortion at 126, then at 120dB it has at least 0.5% distortion, likely H2 dominated.

^^^
The harmonics depicted here may be mix of the signal path. It hard to fathom that a PA driver have this much strain under 4KHz
Reference:
https://audioxpress.com/article/test-bench-b-c-speakers-de111-8-1-pro-sound-compression-driver
No but I am more talking about how the distortion evalves.Nothing wrong with standardising for 104dB @ 1m.
Which is definitely not the same for each driver.
Which is always difficult to see and understand with just one graph.
Especially when 104dB is pretty loud.
And yes, their graphs, presentation and discussion of the results are in some cases mediocre at best.
I have seen subs where the graph starts at 100Hz. Doh! 🤷🏻🥴
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