3" driver for CBT array?
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=104744
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Topic: 3" driver for CBT array?
Posted By: snowflake
Subject: 3" driver for CBT array?
Date Posted: 24 January 2020 at 2:59pm
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Hi I'm planning to build a CBT array about 1.2m long. After looking at about 100 different drivers I've landed on the Beyma 3FR30 which seems to beat everything else in terms of xmax and sensitivity. Annoyed I didn't consider it earlier. next most suitable seem to be FaitalPro 3FE25 or Peerless 65F25AL01-04 anyone have any other suggestions before I buy? don't suggest anything over £15 per driver. not sure yet whether my array is going to be sealed back, open back u-frame, cardoid with acoustic resistor on the back, or vented with the ports on the rear. going to start with the u-frame and experiment what works best. will post some pics and measurements in a few weeks. cheers Phil
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Replies:
Posted By: Elliot Thompson
Date Posted: 24 January 2020 at 10:02pm
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You need to be weary comparing very small speakers particularly when pitting home audio manufactures versus pro audio manufactures. Specifications tend to be more questionable with speakers aimed primarily to the home audio market as oppose the pro audio market.
When I was exploring 3 inch drivers around 6 years ago, I chose Faital Pro. I've conducted numerous tests using them in sealed, free air and, a straight horn. The speaker(s) showed it's (their) class ranging from 1.5 kHz and up.
I did purchase Fostex in addition to, Vifa later on and was not impressed with the results. Either a lack of high frequency level or SPL was the root of the problem when I compared a Pro Audio Manufacture to a Home Audio Manufacture.
You can hear my comparison of the Faital Pro 3FE25 vs Fostex FF 85WK below.
Drivers of that size are not going to offer enough bass regardless how many you use (coming from a pro audio user standpoint) and will still require a larger driver in order to make up the loss in the lower midrange to bass region. They perform as they are labelled... A Full-range Loudspeaker.
Best Regards, ------------- Elliot Thompson |
Posted By: bob4
Date Posted: 25 January 2020 at 10:29am
| Sica from Italy has a big range of full range drivers. They have a particularly cheap 5 inch unist, the 5d 1cs iirc. Its 12,60 here in Finland. |
Posted By: MarjanM
Date Posted: 25 January 2020 at 1:02pm
i dont think i would use a speaker with a whistler cone for a vertical array to be honest. ------------- Marjan Milosevic MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
bob4 wrote:Posted By: concept-10
Date Posted: 25 January 2020 at 4:54pm
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The 3fe-25 is a fabulous driver, we have used it on a few projects with excellent results. |
Posted By: snowflake
Date Posted: 26 January 2020 at 11:57am
| just ordered the beyma and faital 8 ohm version - will post some test results when they arrive. |
Posted By: studio45
Date Posted: 26 January 2020 at 1:52pm
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Very interested to hear how you get on with the Faital, I'm considering them for my next 12v tops. On paper they look like a good strong driver, designed with PA use in mind. ------------- Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA |
Posted By: snowflake
Date Posted: 16 February 2020 at 9:56pm
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just been doing some measurements of the faital and beyma drivers can't get the screenshot to upload at the moment for some reason. I tested with a 11.7V RMS signal - so nearly 20 watts beyma driver is about 4dB more sensitive across the midrange and goes slightly higher. the faital driver does have lower distortion but the beyma also had acceptable distortion levels. because the beyma is more sensitive and has higher max power, they have roughly the same distortion level for equal output levels. unless you want only moderate volume at ultra-high fidelity, I think the beyma is the superior driver. |
Posted By: Elliot Thompson
Date Posted: 17 February 2020 at 12:18am
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I use the Faital Pro to dampen the dips in the frequency response commonly found with the majority of compression horns so midrange Below (1.5 kHz) is not wanted/needed. Did you find the high frequencies (above 10 kHz) are more efficient in the Faital Pro or Beyma? Best Regards, ------------- Elliot Thompson |
Posted By: snowflake
Date Posted: 17 February 2020 at 11:24am
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because the weather is so bad these measurements were made on a baffle on top of my kitchen table with some pillows underneath - so only useful for relative level comparisson. these plots are the average of three measurements - on axis, 30 and 45 degrees off axis.  |
Posted By: Elliot Thompson
Date Posted: 17 February 2020 at 7:09pm
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Thank you. The measurements are more than enough to see what is taking place amongst both drivers above 10 kHz. The kitchen table allowed me to conduct a lot of audio measurements in the wee hours of the morning (3 a.m.) when everyone else is sleeping any ideas are running wild. Best Regards,
------------- Elliot Thompson |
Posted By: smoore
Date Posted: 17 February 2020 at 9:59pm
| Hi snowflake, Which colour is which driver? |
Posted By: Elliot Thompson
Date Posted: 18 February 2020 at 12:08am
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Beyma: Green Faital Pro: Torques Best Regards, ------------- Elliot Thompson |
Posted By: snowflake
Date Posted: 18 February 2020 at 5:23pm
| manufacturer spec sheets show very similar sensitivity - so bit surprised by the clear difference. |
Posted By: Elliot Thompson
Date Posted: 18 February 2020 at 8:17pm
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It is difficult to make
a comparison amongst Beyma and Faital Pro examining the
manufacturer's specification sheet. The differential in dB range vs
Frequency Range do not coincide on their specification sheets upon viewing the dB increments. The
Faital Pro hovers overall below 90 dB throughout of the majority
of the bandwidth (10 dB increments) whereas, the Beyma appears to be
undetermined from a dB range throughout the majority of its frequency
range due to following an unconventional increment dB scale. With
your chart, at least we can see the behavioural pattern at the given
frequencies amongst both drivers @ 5 dB increments. Best Regards, ------------- Elliot Thompson |
Posted By: JonB67
Date Posted: 18 February 2020 at 10:17pm
| Elliot, Does that verbose post really just say the beyma looks better? :) |
Posted By: Elliot Thompson
Date Posted: 19 February 2020 at 12:15am
This is what I am seeing... Based on the graph, we can see the Beyma 3 FR30 offers around +3 dB over the Faital Pro 3 FE25 within the 180 Hz - 2 kHz range. With the exception of 3 kHz (in favour of the Beyma 3 FR 30 by around +7 dB) the performance is very close from 4 kHz - 12 kHz (not very noticeable from an audible standpoint) between the Beyma 3 FR30 and Faital Pro 3 FE25 loudspeakers. Above 12 kHz, the Beyma offers +5dB within 14 kHz - 15 kHz range and both drivers begin to take a nose dive around 18 kHz.
So pretty much what Snowflake stated in terms of the Highs, Mids and, Bass on what he is hearing is displayed on the REW Plot.
We are at a stage that there are so many 3 inch full-range drivers at our disposal that, there is no need to settle for a full-range loudspeaker that will not meet our requirements.
Best Regards, ------------- Elliot Thompson |
Posted By: JonB67
Date Posted: 20 February 2020 at 8:07am
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Think i might get a few beymas to play with when my workshop is finished and i have the time and a place to mess about with a few cabinets. Really like the idea of a suitcase sized rig able to do a small venue. Was also looking at tony wilkes q25 reprise thread. Although the pictures are gone, the 5 inch coaxial and a second 5 inch driver must be a punchy combination in a bookshelf speaker sized package. The cost and simplicity of a line of three inch drivers has an appeal though!
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Posted By: snowflake
Date Posted: 21 February 2020 at 1:38pm
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putting the order in today for fifteen beyma drivers. managed to work out all the frequency shading with the use of just one 5W resistor. this prototype will be 1.2m long. beamwidth and pattern control can be altered by changing the curvurture of the line (it should be flexible engough to play around with this.). BTW would anyone consider using a CBT as a stage monitor? I have an idea for one that would be just 60cm tall, 10cm wide. with 70degree vertical beamwidth and pattern control to 80Hz.
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Posted By: snowflake
Date Posted: 28 February 2020 at 5:43pm
well I haven't got the drivers yet. three week wait for the Beymas so might just get the Faitals to do a prototype with. also, what's going on with the big dip in my Beyma measurement at 5kHz? it isn't present in the plot on manufacturers spec sheet. maybe a measurement error from reflections? but why isn't it also on the faital plot? If it ever stops raining and blowing will try to measure again outdoors.
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Posted By: Elliot Thompson
Date Posted: 28 February 2020 at 5:58pm
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You can measure them indoors with the microphone very close to the cone at a lower level. That will reduce any reflections taking place during the test measuring in the kitchen. I usually place the loudspeaker on a throw pillow to eliminate any reflections from a flat surface such as a table. Best Regards, ------------- Elliot Thompson |
Posted By: snowflake
Date Posted: 29 February 2020 at 2:21pm
just measured again with the mic 2" from the cone. 5kHz dip is still there
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Posted By: snowflake
Date Posted: 29 February 2020 at 2:29pm
| it really doesn't look to me like a measuring environment problem - the beyma and faital are giving respones that are almost the inverse of each other from 3kHz up - where one has peak the other has a dip. |
Posted By: snowflake
Date Posted: 29 February 2020 at 2:40pm
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low frequency response. this nearfiled measurement is very different to the previous measurement below 400Hz - room response was dominating before. the faital has a lower fs (110Hz vs 160Hz) and a higher Qts (0,7 vs 0.49). on an open baffle, I think this will make up for a some of its lower xmax and power handling - is that right? haven't really decided where to high pass these yet.
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Posted By: Elliot Thompson
Date Posted: 29 February 2020 at 2:47pm
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The next step is to measure the impedance curve to determine if there is a sudden rise in resistance. A rise in resistance at 5 kHz would have the Beyma offer a dip within the 5 kHz range. Based on my earliest measurements the Faital Pro looks about right using a typical swift sine wave sweep. https://postimg.cc/MvkbdmZh" rel="nofollow">  After being whacked with a good amount of power, the response curve is more like this... https://postimg.cc/8jBX2z5k" rel="nofollow">  Best Regards,
------------- Elliot Thompson |
Posted By: Elliot Thompson
Date Posted: 29 February 2020 at 2:57pm
That's right! The Qts, fs and VAS work together for the final result. Try matching both drivers at the same dB level at, I would say, 100 Hz and, make a measurement. The driver that remains the flattest from 100 Hz downwards will require less xmax within the flattest frequency range. The drivers will go out of phase at it's fs. So High Passing either driver above the fs should yield an in phase response up to 20 kHz. Best Regards,
------------- Elliot Thompson |
Posted By: snowflake
Date Posted: 03 April 2020 at 10:56pm
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made some progress  used 11.5mm ply as it's what I had lying about. it's not quite bendy enough so going to leave it bending for a couple of days then screw it to a base and some curved side piece to stiffen it up. the more you curve it the lower the pattern control is maintained.  got some more crimp spade connectors on their way to keep all the wiring neat
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Posted By: studio45
Date Posted: 04 April 2020 at 3:17pm
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Nice! The traditional way to get wood to bend is to use steam or hot water - maybe you could use some wet towels to apply the heat and steam, and then screw it to a former whilst still warm? Or, use a kerf cut between each driver - as long as your front laminate runs top to bottom grain wise? 9mm deep with a 2mm blade should give you more movement without compromising strength too much. You would still want plenty of reinforcement and glue in the kerfs. But this way should help to keep each driver's "land" flat. ------------- Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA |
Posted By: snowflake
Date Posted: 05 April 2020 at 3:42pm
think I can get it to 40deg arc of a 2m circle - should give pattern control down to 120Hz. I'd be afraid to steam this cheap ply in case it delaminated. Fine line between bendy and falling apart. might try some kerfs - might try doing them freehand with a narrow router bit. there's a reasonably thick gasket and there seems to be some flex in the mounting ears so think the drivers will fit okay. |
Posted By: Elliot Thompson
Date Posted: 06 April 2020 at 8:22am
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That is a perfect project to do during these chaotic times. Have you tried implementing the outcome with EASE Focus? https://focus.afmg.eu/" rel="nofollow - https://focus.afmg.eu/ Best Regards, ------------- Elliot Thompson |
Posted By: snowflake
Date Posted: 03 May 2020 at 2:25pm
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got it wired up a couple of weeks ago and have been testing it side by side with my regular hi-fi speakers. still open baffle and haven't even put sides on it at yet as still palying around with the curvature. needs a bit of eq but has useful response down to 100Hz. sound is great with no midrange mudiness. plenty loud enough for home use but runs out of excursion on bass-heavy material. might experiment with another driver with lower Fs and more xmax Beyma 4FR40-8 Faital 4FE35-16 Dayton ND91-8
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Posted By: ceharden
Date Posted: 03 May 2020 at 2:29pm
| You might expect the bass response to improve a bit and excursion to reduce when you turn it into a sealed box. Might get you low enough to cross over comfortably to a sub. |
Posted By: snowflake
Date Posted: 03 May 2020 at 5:20pm
I am tempted to try making it sealed back. but I'm quite liking the midrange sound of the open baffle. U-frame might give it a bit more authority down low.
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Posted By: imageoven
Date Posted: 10 April 2021 at 12:22am
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Did you ever complete this project?
I'm still sitting on 12 x 4" drivers, with an option on 4 more , and I'm interested in the options ------------- Keep pushing on, things are gonna get better. |