I've built a pair of 2-way bookshelf speakers that consist of a 1" tweeter, a 5" mid-woofer, and an 8" passive radiator per cabinet. They're indeed good sound. But, I have an unused pair of 8" car subwoofers with their 30-litre enclosures. These subs also have 300Hz 2nd-order passive low-pass filters. I'm thinking to convert my 2-way system to 2.5-way by stacking these subs to the existing 2-way bookshelf speakers. I have the following questions:
1. Since both 2-way speakers and the subs are 4 Ohms system, do I need to connect them "in series", in stead of parallel as conventional system; to prevent them from being 2-Ohm loads?
2. The subs with their enclosures are calculated to be tuned at about 35 Hz. However, the 2-way passive radiator speakers have resonance frequency at about 60 Hz. Hence, do I need to retune the passive radiators to have resonance at the same frequency as the subs i.e. 35 Hz?
1. Since both 2-way speakers and the subs are 4 Ohms system, do I need to connect them "in series", in stead of parallel as conventional system; to prevent them from being 2-Ohm loads?
2. The subs with their enclosures are calculated to be tuned at about 35 Hz. However, the 2-way passive radiator speakers have resonance frequency at about 60 Hz. Hence, do I need to retune the passive radiators to have resonance at the same frequency as the subs i.e. 35 Hz?
Do you mean that at the resonance frequency of either driver, the phase of sounds from the driver in a sealed enclosure and from the PR driver may differ from each other?
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Yes that's right, but it's not the only problem you'll need to deal with. If you put them in series the impedances won't share the signal fairly because the peaks won't line up.
I was suggested by my friend that the high impedance won't cause any problems, but the low impedance will.
He also suggested that we should pay attention only not to let the loads, here the speaker, have too low an impedance, mostly not less than 4 ohms if used with a home amplifier. Is this correct?
Could you please explain the results of the unfair signal sharing due to non-linear impedance peaks?
I've used flat simulated responses so you can see only the variations, and added two random woofer impedances. (Never mind that one is 4 ohms and one is 8 ohms, all I'm showing here is the ups and downs.)
Not only are the responses different, the phases vary and this adds to the already different phases.
Not only are the responses different, the phases vary and this adds to the already different phases.
Sorry, it was my typo. The main speaker boxes, PR system, were tuned at 28 Hz, whereas the sealed subs are tuned at 56 Hz.
Note: you will see that the subs' tuning is twice the main speakers. Beautiful number I think, but I'm not sure if it's good for sound.
Note: you will see that the subs' tuning is twice the main speakers. Beautiful number I think, but I'm not sure if it's good for sound.
Although it would cost money, I would invest in an amplifier that can drive 2 ohm loads.
You can then go with parallel connection for maximum output level and bass.
(you must get the +/- phase connection correct - this should be easy)
Although I have more than one amplifier, some time ago I 'bit the bullet' and bought a
high power, low distortion power amplifier that can easily drive 2 ohms ...
knowing that it would do me for the rest of my life.
You can then go with parallel connection for maximum output level and bass.
(you must get the +/- phase connection correct - this should be easy)
Although I have more than one amplifier, some time ago I 'bit the bullet' and bought a
high power, low distortion power amplifier that can easily drive 2 ohms ...
knowing that it would do me for the rest of my life.
I encountered this when I decided to try more then one subwoofer per channel. In the end its better to add more channels and designate them to one sub unless there parts are equal.
Have you tried connecting the subs "in series" to one channel? What was the result?
This is interesting because if the multiple subs per channel cause problems for the amplifier, that may be the result of the subs acting as too low loads due to the parallel connection. Hence, to change the situation, one could try reconnecting them "in series" instead.
What do all of you think about my assumption?
If your speakers sound nice now what is the problem? If you add these subs with a 300hz low pass the whole balance is going to change probably for the worse. Adding the subs will not make a 2.5 system.
Actually, I obtained the suggestion from the subwoofer's manual. It stated that the owners can use these drivers to enhance bass definition with the recommended "low-pass" at 300Hz.
I think if the "high-pass" at 300Hz is applied to the woofers, the system be considered as a 3 ways. Nevertheless, no "high-pass" are employed in this case.
Your may also use a plate amp plus build-in crossover to power one or more subwoofer cabinets. Easy integration.
Something sounded really off about it to me. It can be difficult, or tricky rather, to decipher such changes. Until giving your senses adequate time to re-adjust to changes. I didn't even keep the series configuration for long, or enough to reach any benefit of doubt. I put everything back to stereo, meaning with one sub per channel.