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Is it sensible to use a sub to relieve effort from a single driver BLH?
Is it sensible to use a sub to relieve effort from a single driver BLH?
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Old 14th March 2017, 01:57 AM   #1
hugz is offline hugz  Australia
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Default Is it sensible to use a sub to relieve effort from a single driver BLH?

I'm using a Dallas 2 as my main speaker (fe206e 8" full range). I'm quite happy with the bass, but I can't help but wonder if I should supplement it with a subwoofer and use a high-pass filter on the Dallas?

My theory is that when the Dallas is dealing with a 30hz signal, it must be difficult to keep enough driver control to also produce a clean 500hz concurrently. If I put a high pass filter on so the fostex doesn't have to stress itself with heavy bass, it should be cleaner in the "music" range.

That's my theory at least. Really, I know nothing about speaker design.

Opinions and advice please.
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Old 14th March 2017, 09:16 AM   #2
norman bates is offline norman bates  United States
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But filters aren't usually the best sounding, especially crossover phase to us full range driver people.

You can try a receiver and use its crossover to see if you find the benefits outweigh the drawbacks.

I have luck running a full range wide open and run a subwoofer with the driver.
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Old 14th March 2017, 09:22 AM   #3
scottjoplin is offline scottjoplin  Wales
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What you are describing is called FAST : Fullrange And Subwoofer Technology or Fullrange ASsisTed. It has benefits as you surmise
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Old 14th March 2017, 09:53 AM   #4
chris661 is online now chris661  United Kingdom
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Quote:
Originally Posted by norman bates View Post
But filters aren't usually the best sounding, especially crossover phase to us full range driver people.

You can try a receiver and use its crossover to see if you find the benefits outweigh the drawbacks.

I have luck running a full range wide open and run a subwoofer with the driver.
I'd argue that the phase curve produced by a crossover is by far a lesser evil than the distortion caused by the driver's voicecoil exiting the gap. That's not to mention the fact that the cabinet's LF rolloff already has it's own phase wiggles.


Just adding a sub will usually increase low-frequency level and/or extension. If you put a highpass filter on the midrange driver, you lower the distortion it's producing. Combine the two for the best effect.
The next step in that direction is to use a smaller full-range unit (generally better HF performance) in a small sealed compartment, and cross at 2-400Hz to a 6-8" midbass driver. Having the crossover higher up means even the small drivers can run comfortably at loud levels - 100Hz still requires a bit of cone movement.

Chris
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Old 14th March 2017, 11:24 AM   #5
jimbro is offline jimbro  United States
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I believe that in most blh designs, the horn is only active from about 300hz and below. What are you listening to and at what level? If I were to use a sub I'd cross it over fairly low like about 50hz so my dallas still handles most of the bass since you're "quite happy" with it. Then it becomes a question of how much money do you want to invest for that small benefit?
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Old 14th March 2017, 09:40 PM   #6
chrisb is offline chrisb
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It probably never hurts to BOTH relieve a smaller (less than 8"?) FR driver from the heavy lifting with HP filtering below, say, at least 80-100Hz, and reinforce with (sub)woofers - separately powered is my preference. Once you go high enough, stereo woofers should be considered essential. Call it what you like, it's a two-way system, just crossed over lower than the more commonly seen values anywhere between 1000-3200Hz.

Of several such combinations I've built over the past few years, my most satisfying results were with a 4" FR and pair of 6" mid bass per side. As neither of my listening spaces are friendly to BLH large enough to operate - aided or not- to the lowest couple of octaves, these enclosures were a floorstanding MTM. They're not narrow, but shallow enough to not encroach on floorspace, and being monopoles, placement with regards to side and rear walls and furniture is not as critical.
I always like a design that works for the room as it is, not shoehorn something that sounds great in a large, open space into a room constrained by size, shape and furniture . Not everyone has such restrictions, but until I have an ideal situation, WAF rules.
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Old 15th March 2017, 03:15 PM   #7
fb2017 is offline fb2017
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Well, what is important for you? Do you appreciate the deep pinpoint precise sound stage a pair of Dallas II is presenting or do you need even more bass than it already has? You can't have both unfortunately, because physics...
I found the bass on mine to be very fast, tight and impact full, but it won't be a stomach shaker, that's for sure. For me it is more than enough (live jazz, rock&roll, classic), at speaking voice volumes (OK, occasionally also louder).
If you love thumping 20Hz music (trance, house, electronica, etc), at high volumes, then you're probably better served with another design altogether.

>My theory is that when the Dallas is dealing with a 30hz signal, it must be difficult to keep enough driver control to also produce a clean 500hz concurrently.

That only at very high listening volumes, where the combined excursion caused by adding the two signals is more than the maximal one. The driver then behaves as a compressor. Driver control is a question of the amplifier, and if you have doubts, you can try them with a different 30 W amp, and see if it sounds better.

Last edited by fb2017; 15th March 2017 at 03:20 PM.
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Old 15th March 2017, 03:31 PM   #8
scottjoplin is offline scottjoplin  Wales
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Or, if you don't want to have multiple sets of speakers for your varied musical taste..........I'll let you work it out for yourself
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Old 16th March 2017, 12:39 AM   #9
hugz is offline hugz  Australia
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In response to the 2 specific questions about what I listen to- Various styles of music, including hiphop and rock. Often loud. I'll often see my drivers pumping to a drum beat and think "this can't be good for the drivers, or the sound".

As for what is important to me? Only nice "fidelity" really (as in- the accurate reproduction of sound). I'm not aiming for booming bass or anything. I'm just thinking of taking away extra stresses on the Dallas so that it can focus on fidelity without being overcome by trying to produce bass at the same time.

The reason I like the fullrange driver is really just because it seems "natural" to me. A trumpet lets out one note at a time- not three notes (thus, 3 drivers seems unrealistic). Likewise, to my best knowledge things are recorded using fullrange mics rather than 3-way mics.

Of course my impression of fullrange vs multi-way isn't exactly an accurate representation of speaker technology, but it's a feeling I get when I listen to fullrange. Obviously using a subwoofer goes against that a bit, but.....
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Old 16th March 2017, 04:36 AM   #10
GM is offline GM  United States
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Hmm, based on this, you'll need a seriously powerful ~40-150 Hz woofer/mid-bass system emphasis relative to the mains for hip-hop, with output to ~20 Hz to cover some other bass heavy music: http://thehub.musiciansfriend.com/te...-musical-style

GM
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