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Discussion Starter · #1 ·
Hi all,
I am a beginner in DIY speakers and have been reading quite a lot lately but cannot find the reason to why my speakers perform this bad at the lower frequencies 150hz and down.

I am using Perless nomex 830875 crossed at approx 810hz with a 2nd order, no Zobel. Internal cabinet dimensions 212x310x260mm (17,3 liters with element and port volume included),19mm mdf (no bracing:( ), port diameter 6,9cm length 23,1. according to calculator, tuned at 52hz (recommended?) and damped on the sides and back with acoustic stuf. I really think they sound quite nice except little harsh and this I can fix BUT the weak bass something I really don't understand!!! I do not think the 6,5" driver should be this weak. Actually it is a bit louder at low frequencies (around 30-50hz) But this might be due to room modes. I have tried the speakers in different rooms so I do not think standing waves are the issue.

Appreciate if someone can help me understand if there is something I have missed.
Thanks!

Best regards
Mattias fr.o.m. Sweden
 

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Welcome to HTS! :bigsmile:

Can you describe your entire crossover for me, did you design it or did somebody else? Can you also describe where you place your speakers in your room? The problem you describe sounds exactly like the effect of not including baffle-step compensation (BSC) into the design. The issue is that as soon as you place a woofer in a box, bass and lower midrange frequencies suffer sensitivity loss that the higher frequencies do not. At what frequency this happens depends on your baffle dimensions, the impact can be as much as -6dB depending on the environment and speaker placement (usually DIYers compensate 2-4dB). The quick fix would be to add an RL shelving filter before the rest of the crossover.
 

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Welcome to Home Theater Shack, Mattias. Sounds like you have some good advice from our friend fusseli to try. Let us know how it all works out.
 

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Discussion Starter · #4 ·
Thank you VERY much! I will have to read some more about BSC:). I have not heard of LR shelving filter, what is the effect of this? Do I attenuate the other drivers to compensate? Is there any other way except for an enourmous baffle?

I made it quite easy for me as it is My first project and used an online crossover calculator for a 3-way 2nd order crossed at 812,5 & 6500. I realized quit quickly the speaker building is not that easy but I will not give up that easy;)
 

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Funny you mention an enormous baffle, the BSC effect is exactly why the same crossover can't be used for a normal speaker and an in-wall version of the same speaker. No there is no other way to compensate besides within the crossover design. Physics is physics! And yes, by incorporating BSC this effectively attenuates everything else down to the same level as the lower midrange and bass.

I would strongly recommend trying out and modelling your speaker in PCD. It's a little difficult to learn but it's an extremely powerful free tool for speaker design. Along with that, get Response Modeller with which you can exactly model the effect of your baffle and compensate appropriately. Ideally you would do this by using PCD from the beginning to design the crossover, such that you don't need the separate shelving filter.
 

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Discussion Starter · #6 ·
Again, really appreciate that you are helping me with this. I will try this and elaborate.
Have a nice day!
 
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