Crazy crossover possible?

ntell411

Member
2014-04-30 8:42 pm
Hi, I'm new to this crossover stuff but trying my best to understand how to do this: I want to use one 8 ohm 18 inch woofer with an inductor at 100hz as a low pass and then use another identical 18 inch 8 ohm woofer with an inductor at 200hz and combine it with one 8 ohm full ranger with no caps or inductors. Will this work and will the amplifier see an 8 ohm load?
 

Galu

Member
2018-04-17 6:50 pm
200Hz is very close to 100Hz, so I would just wire the two 18" units in parallel with a single inductor in series with the combination to provide a low pass filter at your desired frequency, say 200Hz or even a bit higher. This combination will give an amplifier load of 4 ohm over the frequency range where most of the signal power is being delivered by the amplifier.

A capacitor should be placed in series with your 8" full range speaker to provide a high pass filter at the same turnover frequency as the 18" drivers.

Whether this works effectively will depend on the relative sensitivities of your drivers, so you would have to supply information about them. If you follow the above suggestion then ensure your amplifier is happy to work into a low 4 ohm load.
 
I never bother with crossovers on sub woofers.
They cant reproduce higher frequencies much anyway.

I guess you are not familiar with the JBL 2203H, 2235H, and 2245H then

JBL used them in Subwoofers and as woofers in 4 way systems.

I myself run a 2245H as a subwoofer with a minidsp unit as crossover,
and with the hp filter bypassed it reproduces tunes well over 1khz before rolling off.
But this aint no 500grams mms slouch with tons of self inductance.
;)
 
For a person who knows nothing, you sure are certain where you want to go on this. :confused:

They say "Fools rush in where Angels fear to tread!" :eek:

2X 18" speakers will be seriously loud. I don't know where you find a mid that can keep up with this.

Anyway, this is PA territory, and a host of other problems.

You can use biggish basses with a few other drivers, but Mr. Troels Gravesen has been careful to series wire the 12" basses to keep loudness within limits:

DTQWT-mkII

Might be doable at some level with electronic filters. But, I dunno! :D
 
Let's remember where we all started shall we? I had similar dreams as this and guess what? Some of them came true.

I think ntell would be best off if he got two 18 4Ω drivers and ran them in series. The inductors he will need are going to be big and expensive so definitely consider just two of them and keeping a single XO point. I think you also want to raise the XO to ensure you don't see smoke coming from the 8" Maybe 300 Hz and use both a cap and coil on the small driver to get a steeper slope.

In fact, you might want to consider going active. The Behringer 2-way is priced well and will give you a more secure control over things. But, you will need a second amplifier.

Even cheaper is to do a PLLXO. Passive line level crossover. Still need a second amp and you don't have a lot of control over things but it's a great way to save coin.

What is your goal here and what do you to put into it?
 

ntell411

Member
2014-04-30 8:42 pm
I will post my reply again as I don't know if it went through. Thanks very much for all the timely responses. My goal is to run 2 Goldwood 18 inch drivers (8 ohm, 94.3 db 2.83v/m) with 1 Fane 12 inch FULL RANGE driver (8 ohms, 100 db, 1w/m) crossing over at 300 hz using an inductor only. I really like the tone and clarity of the Goldwood woofers and Fane Full range and think that using 2 woofers will give me more dynamics and bass as they only have 2 mm displacement and I will use them in an OPEN BAFFLE arrangement. Ok, my audio piranha friends, please help me out!
 
Fane full range will be way too loud for those low-cost two (parallel) 18" in a open baffle. Consider active bi-amplification: active (electronic) or passive (line-level) crossover and two power amplifiers (or one stereo amp) per speaker. One amp channel for the Fane, the second amp channel for the two 18-inchers. That is four amplifier channels in total, for a pair of open baffle speakers.
 

ntell411

Member
2014-04-30 8:42 pm
I have read all of the suggestions and not one of them gives me an answer as to why I cannot use 2 woofers and 1 fullrange driver (all 8 ohms) and treat this as a 3 way system where 1 woofer operates below 100hz (using an inductor only), the second operates below lets say 300 hz (using an inductor only) and the full range driver operates full range. I can use an L-pad to attenuate the full range driver to match the 2 woofers. Should this not work?
 
This is not an original thought from me, since I gleaned it from another thread! :eek:

But here's a project from Troels using an 18" woofer:

The-Loudspeaker

Just how it works, but wire two 18" in series and they come out same loudness.

So, yeah, maybe there's hope for this concept. 10" mid plus horn tweeter. Albeit Hypex amp on the basses for convenience. But a passive option too. Sadly Troels is being secretive about the exact filter values, cos he's gotta eat.