- Jun 5, 2020
After hours of reading on the web and especially on the ASR forum, I’m finally decided to start designing my first DIY speakers.
Initially I wanted to start with a tower speakers but I reconsidered my plan by first trying to take experiance first with a 2 Way Bookshelf speaker.
This project will be not very original as I want to make an inspired version of the Buschardt audio S400.
In that regard, I was planning to use :
-SB17NBAC for the woofer ;
-SB15SFCR for the passive radiator.en.toutlehautparleur.com
The woofer SB17NBAC as an Sd of 118cm² and a Xmax of 7.17mm (so 84.6cm^3 of displaced volume)
The passive radiator as a Sd of 178cm² and à Xmax of 11mm (so 195.8cm^3 of displaced volume)
So the passive radiator can displaced 2.3 time the air volume of the woofer which looks in the rules.
I was planning to use a 18L box and tried to simulate that in WinISD and it look like I could obtain a 50hz low at -3db.
So first, what do you think of this driver selection ?
Then come the hard part for me as I have no skills in crossover design and I know it have a huge rôle in the final result (I only know how to read a crossover schematic and good at welding components)
By looking at the frequency response of the drivers, I was thinking of using a crossover point somwhere beetween 1500 and 1800hz.
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This leads me to ask you few questions :
-How do you select the nominal speakers impedance as the woofer is available in 4 and 8 ohm ?
-Does a generic crossover always lead to a bad result ?
-Is there any active crossover module that can be used with numerical output for 2 FDA « budget » amplifier ? ;
-Othrewise, where to start from and which software do you recommand for passive crossover design ? (Go back to school is an acceptable answer ;-) ;
I also plan to order a UMIK-1 as I know it will be necessary to adjust parameters in every cases.
You can make quasi-anechoic measurements in-room using the method outlined in this thread. https://www.audiosciencereview.com/...ents-spinoramas-with-rew-and-vituixcad.21860/Few pictures of the prototype built. Cables are not the final ones but what I had on hand…
I started to make my crossover using the MiniDSP, but the current result is not really relevant as I did my measurement in room and it seems there is a lot of reflexion. Need to find time and space to do that with the adequate conditions. However, I'm already conquered by the sound of this speaker which seems to fill the whole room even though I only tested one.
What is the best SPL level I should focus on or I should work with for the crossover adjustment and why ?
On many response graphs I see an SPL level close to 85/90db as a target for the curve. It’s way too high level for an everyday listening so my thinking is, why do the crossover is adjusted so high whereas most of the people don’t listen that high. This question is also related to the non linear hearing humans a equipped. If the tunning is good at 85db, the result will be not in standard condition around 70db.
Is there any benefits to choose a an high crossover (2600/2800hz) versus a lower one (1800/2000hz).
I tried both and even if the response curve looks good, it’s way much detailed and accurate close to 2650 than with a lower value.
Any remarks or comments on my build are appreciated. It’s my first speakers so I may have done some mistakes.
Looks nice .Thanks for the answers and advices.
So i'm using the 8ohm version of the NBAC.
I worked a little on the active crossover and her is the current result with the goal to follow the marginal line around 78db.
-Yellow line is the tweeter
-Orange line is the mid/bass woofer
-Red line is both without any EQ on the DSP
-Green line is after DSP EQ. I also added a 40hz high pass filter otherwise bass are too punchy for me.
I did not played yet with the inner plate position to check if and how it affect the response.
I'm open to any comment to see where I could make changes.
Nice looking speaker. Why was the ring radiator chosen?Looks nice .
I would try a slightly lower dsp crossover , maybe everything from 1,7 KHz and go up to 3 KHz . The sound will be slightly different even if the frequency response looks the same. Theres always a tradeoff getting good directivity and low distortion . So in the end , you have to decide what sounds the best with music and ears.
You also have to tune the passive radiator with different weights . Try different and settle for the tuning that sounds best.
Use a 18 dB/oct dsp HP filter 5-10 Hz below the tuning frequency . This is very important for good sound .
In the Hybrid projekt , I also played with the tilt of the waveguide frequency response. 1 dB more energy at 10 KHz is audible . This is easily done with the dsp .
In this speaker the sound was the best with a crossover at 2,3 KHz , but the directivity measured best at 1,8 KHz .
The scanspeak ringradiator didnt like crossovers lower than 2 KHz .
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