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Multi-Way Conventional loudspeakers with crossovers

Construction of a 3 way floor speaker
Construction of a 3 way floor speaker
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Old 8th November 2019, 01:35 PM   #1
triodehead is offline triodehead  Sweden
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Default Construction of a 3 way floor speaker

Hello

I am new to this forum. I just made an account and I have a question regarding a 3 way speaker design. I have no experience at all of this type of construction. I already own a pair of planar ribbon tweeters PT2C-8. I guess that they are quite good. Here is an datasheet of them.

https://www.parts-express.com/pedocs...ifications.pdf

The main things is "3 kHz recommended crossover frequency at 12 dB per octave" and 94 db sensitivity.

I have borrowed a pair of Canton LE109 that sounds nice and I want to build something similar to those in a physical size. Floor speakers that are high but can not overturn if my one year old kid are smashing in in them when she playes with her toys.

8" elements are a good and a nice size of the bass element, but the midrange speaker? I do not have a qlue. I do not know what I should buy and I have no idea of how I would construct the filter or nothing. I can build them in wood if I knew how to build them.

Any recommendations here?

My amplifier is a class AB tube amp with 2x15 watt output driven by EL84 and guitar outputtransformers so it is not so strong in the lowest frequencies, So if I can compensate for that in my design, it would be very good.

Where should I start?

Kind regards form a new forum member from Sweden.
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Old 8th November 2019, 02:43 PM   #2
ILikeFoodz is offline ILikeFoodz  United States
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Welcome to the forum!

For the midrange I would probably look at drivers around 100-135 mm to start with since they will generally be ok with crossing at 3kHz, and larger drivers generally will have higher sensitivity than smaller drivers, which will help get them closer to your tweeter's output level of 94 dB. The Dayton Audio RS100 and RS125 series would be worth a look, as well as SB Acoustics SB12, SB13, and SB15 models.

Edit: It would also be worthwhile to start reading up on crossover design and general speaker construction. There are lots of threads here you can find if you search, and various resources elsewhere. I don't have any specific ones to link to that I can remember right at the moment, but other forum members might have some links easily available.

Last edited by ILikeFoodz; 8th November 2019 at 02:45 PM.
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Old 8th November 2019, 03:40 PM   #3
Richard Ellis is offline Richard Ellis  Argentina
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I would opt for the 6CBMRA Eminence 6 1/2 inch sealed-back mid..trying to keep with the 95+ Db theme...crossed at 3-4K ..Get some LOG graph paper & overlay to two Db response curves & tell me what you think..



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Old 8th November 2019, 04:02 PM   #4
mountainman bob is online now mountainman bob  United States
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I’ve found it better to match tweeter sensitivity with pro mid/woofers than to attenuate the tweeter to match.......but then again I’m just a blind squirrel.

In other words I agree ^^

Last edited by mountainman bob; 8th November 2019 at 04:05 PM.
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Old 8th November 2019, 08:28 PM   #5
metzb1 is offline metzb1  United States
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You'll have a difficult time achieving 95dB/W @ 1m with an 8" woofer unless you're willing to give up a lot of extension.
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Old 8th November 2019, 10:57 PM   #6
triodehead is offline triodehead  Sweden
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Hello


Thanks for quick answers, I guess that I have to sacrifice some sensitivity with dampers in the filter to match a 87 db spl speaker. I found a thread here on the forum from 2010 that have a few tip in which speaker that could be matched with my high sensistivity tweeter and also a high sensitivity midrange. But I need a deep bass response.


I like the look of the Dayton Audio RS125-8 with 8 ohm impedance and 87 db spl. But the SB Acustics SB15 is also nice, it has 88 db spl sensitivity. The 6CBMRA had a strange response curve that scares me a little, a dip at 400 hz, I guess that is not something that I want?



The best bass woofer element I have found so far for a resoable price is Dayton Audio RS225P-8A 8" reference paper woofer 8 ohm. It has 89 db spl sensitivity.


I do not know, is this the right track for me? I am satisfied with a borrowed Canton LE109 that has 87 db sensitivity. But I have to give them back in a few month.
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Old 9th November 2019, 01:54 AM   #7
PeteMcK is online now PeteMcK
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SB20PFC are the best priced 8" woofers in Aus, try a 4" or 5" mid for best dispersion, SB12PFC or SB13PFC, or something equivalent in the Peerless range
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Old 9th November 2019, 03:40 AM   #8
LineSource is offline LineSource  United States
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If you have listened to the PT2C-8 planar ribbon tweeter in a good design and favor its limited vertical dispersion with a 2.5-3kHz crossover, add the 4" Faital 4FE32-8 midrange and 8" Dayton RS225SP-8 woofer. The mid and tweet will need to attenuated to ~87db to match a single 8" woofer.
========
You could build a 3-way proven design with a 1" dome tweeter + 5" midrange + 8" ported woofer for a successful reference sound, BUT construct the front baffle so you can SWAP baffle sections between your PT2C-8 planar ribbon tweeters for the dome. The baffle could be build from two 0.75" boards such that only the upper section of the front baffle board would need to get exchanged for the tweeter experiments. You would need two different tweeter crossover circuits, but the L-R-C passive parts are small and modest cost.

The tone from aluminum cone midrange like SB15NAC30-8 is often used with ribbon tweeters. The soft dome SB21SDC-4 tweeter has extended high frequency and a flat SPL, and a polar response which blends with a 5" midrange at 2,200-2,500Hz crossover. Add the aluminum cone woofer SB23NACS45-8 to blend.

Last edited by LineSource; 9th November 2019 at 03:43 AM.
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Old 9th November 2019, 09:23 AM   #9
triodehead is offline triodehead  Sweden
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SB Acoustics SB20PFC30-8 is a quite cheap and looks nice and quite good low end response. 90,5 db spl

Click the image to open in full size.


Vifa P21W0-20-08 has 91 db spl

Click the image to open in full size.


Vifa is more expensive but a little more sensitivity. Should I look att these graphs at all or how should I think?


When I try to match all these suggestions I got to match my ribbon planar tweeter I think all speakers should be 8 ohm to be able to build a crossover filter?
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Old 9th November 2019, 10:11 PM   #10
triodehead is offline triodehead  Sweden
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I have searched a lot after some nice speakers now and I have checked every tip that I got from all of you that have wrote in this thread. I have also read the sticky post about constructing a crossover filter but that is a later matter to deal with.


I think I can build a 93 dB system after all, or what do you pro diy-builders say?


A set up that could work or not? I also wrote some theoretical freqency ranges that I think can work.



PT2C-8 Planar Tweeter 94 dB @ 1W/1m lower cut @ 3000-up Hz
6CBMRA Eminence 6 1/2 inch 97.8 dB 1W/1m 400-3000 hz

8RS250 93 dB @ 1W/1m 20-400 Hz



The 8RS250 speaker has a frequency range 60-6300 hz in the datasheet or should I choose another speaker that has a range that is started at 20 hz? The graph in the datasheet shows measurments from 20 hz and up.
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