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Multi-Way Conventional loudspeakers with crossovers

BLH midrange... Crazy?
BLH midrange... Crazy?
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Old 14th April 2019, 02:19 AM   #1
mashaffer is online now mashaffer  United States
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Default BLH midrange... Crazy?

This may sound crazy but has anyone tried using a BLH for a high efficiency midrange. It seems like an approach that might work but would require a rather special driver.

It would need to rather efficient in its own right with a rising response and very low Q (kind of a scaled down Lowther type driver) because if I am not mistaken the BLH only boosts output at the lower end of the driver's range and really likes a strong motor.

The LaVoce line has some interesting candidates but not quite as low of Q as our Lowther buddies.
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Old 14th April 2019, 06:03 AM   #2
jtgofish is offline jtgofish
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Why would you want the reverse phase coming out of the back of the driver and interfering with what is coming out of the front?That is probably the worst approach you could use.
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Old 14th April 2019, 07:00 AM   #3
Phenoholic Anonymus is offline Phenoholic Anonymus
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I am fascinated by the same idea. BLH for midrange 130- 1.500 Hz, horn above the midrange. And i am also looking at the Lavoce range for a cheap driver to get the idea tested . These seem to work fine. White horn 16 cm driver x-over at 1.200, Red Horn 20 cm driver x-over at 800 Hz.

Click the image to open in full size.Click the image to open in full size.


Lavoce MAN062.00, 8 ohm seems to work ok in AJ-Horn. With the opening of the horn 30 cm behind the driver. (Front firing driver, backfiring mouth). B&C 4NDF34-8 has an EBP of 392.

The idea got three things working for it:
1. from 130 Hz up, you can use a relative big horn mouth. Say 1.200 cm2 this increases sensitivity. 100+ dB/1m/Watt according to sims with AJ-Horn.
2. The length of the horn is short, around 1.50 meter. so backwave delay is less of a problem.
3. You can turn the cabinet around, mount the driver where the compressions driver for freq. above x-over start. Thereby eliminating the big path length difference above horns have at the crossover frequency.

The delayed backwave is still there. But time alignment at x-over could be improved. If you look at the x-over points and diameters of the 16 and 20 cm driver in the horns above, they are both crossed beneath the freq where they become directional. I don't know if the idea could work but really like the idea of a cheap horn satellite with 100dB and improved alignment at x-over.

Info on red and white horn in German:
BK163KH - ART OF SOUND - Hornlautsprecher
BK 201 KH - ART OF SOUND - Hornlautsprecher

Last edited by Phenoholic Anonymus; 14th April 2019 at 07:09 AM.
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Old 14th April 2019, 07:49 AM   #4
ICG is offline ICG  Germany
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Quote:
Originally Posted by jtgofish View Post
Why would you want the reverse phase coming out of the back of the driver and interfering with what is coming out of the front?That is probably the worst approach you could use.
Indeed, that's a very bad idea. A BLH delays the decay of impulses, reflections within the folded horn. In the bass you can get away with that because the ear is not very sensitive to phase problems or a non-linear response but to use it in the midrange will sound awful.

What driver is it, in which frequency range do you want to use it? A front horn is a much better solution.
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Old 14th April 2019, 08:08 AM   #5
Phenoholic Anonymus is offline Phenoholic Anonymus
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The idea would be a bigger Hilding horn. The Hilding horn A cheap way to get high effieciency, experiment and have fun.
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Old 14th April 2019, 11:16 AM   #6
Phenoholic Anonymus is offline Phenoholic Anonymus
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The Voxativ has an unusual mix of backloaded mouth and driver sound. As far as i can see it has no backchamber. It's so darn near close to where a horn on top can overtake, i think it's worth the experiment.
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Old 14th April 2019, 06:48 PM   #7
freddi is offline freddi  United States
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BLH midrange... Crazy?
vented alone would make passive crossovers more difficult - active crossover better - but there's resonant spikes out the vent

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Last edited by freddi; 14th April 2019 at 06:59 PM.
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Old 15th April 2019, 12:12 AM   #8
GM is offline GM  United States
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Quote:
Originally Posted by mashaffer View Post
This may sound crazy but has anyone tried using a BLH for a high efficiency midrange. It seems like an approach that might work but would require a rather special driver.

It would need to rather efficient in its own right with a rising response and very low Q (kind of a scaled down Lowther type driver) because if I am not mistaken the BLH only boosts output at the lower end of the driver's range and really likes a strong motor.

The LaVoce line has some interesting candidates but not quite as low of Q as our Lowther buddies.
The mids are from ~250-2 kHz* and ideally we want a BLH to decay away with the baffle step and keep comb filtering through this acoustic XO with the driver's output well down where our hearing acuity isn't too good, which ideally is < ~300 Hz, requiring a relatively high Qt driver and a ~ 'one note' horn, so not a good plan viewed from any angle and why 'compact' BLHs tend to be at least mid bass/lower mids requiring a bit lower Qt drivers.

Horns are just folded up OBs, so don't care what the driver specs are, just at some point they become too big, short to be practical as anything but a WG and if you study the pioneer's BLHs you'll see that most started with medium Qt drivers coupled to a high output impedance = high effective Qt systems, making horns short, 'fat' once the corner was factored in with a narrow BW designed to offset baffle step loss, i.e. acoustic BSC.

Woofer horns of course were much wider BW, so Fs, Qts' needed to be lower [2*Fs/Qes' or Qts' depending on who you ask].

Qes' or Qts' = Qes or Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

* Musical Frequency Spectrum : classicalmusic

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Old 15th April 2019, 12:24 AM   #9
GM is offline GM  United States
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Originally Posted by Phenoholic Anonymus View Post
It's so darn near close to where a horn on top can overtake, i think it's worth the experiment.
With increasingly out of phase output comb filtering between the driver and horn up to ~ 1 kHz, well into our acute hearing BW, I have to wonder how 'clean', 'detailed', 'accurate' it can be to anyone use to listening to live music or at least well recorded: https://slideplayer.com/slide/506545...cteristics.jpg


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Old 15th April 2019, 08:14 AM   #10
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Thanks for the reality check, i know it's a stretch and could sound horrible. Sometimes i get to enthousiastic with the simulation program: 150 - 1.200 Hz + 100dB with smaller drivers .
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