For what it is worth, I use midbass horns from plm 80hz up, they are located on the floor, but I do not experience "no bass" up to 10' in my room. So it is not a given and may have more to do with the acoustic environment, but I never researched this phenomenon. So it may be true, just not in my situation.
Thanks @Horneydude
That is encouraging!
Can I ask how big is your room, how far from the midbass horn mouth do you listen, and what do you use below 80Hz?
That is encouraging!
Can I ask how big is your room, how far from the midbass horn mouth do you listen, and what do you use below 80Hz?
I don't seem to have that problem. I've enquired about an explanation a few times but I'm still uncertain.
My room has a bit of an odd shape, with open kitchen and a wall halfway but the speakers are about 3 meters (9'20") apart and 3 meters from where I am listening. The speakers are toe'ed in, across the side walls and the mouths are roughly 1/3th of the length of the room from the back wall. I use bandpass subwoofers in a quasi-single bass array below 80hz. Picture below is the midbass horn I designed long time ago and long time pal too.. I call it the MIGhorn.
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That W bin is a very capable horn. I've built very similar ones and loaded them with EVs. Good bandwidth up into the low 100s.
Won't it have been posible to arrive at the same horn length with just a single fold and the same outer dimensions ?
Regards
Charles
Thank you!
I will look into what a "bandpass subwoofers in a quasi-single bass array" means.
Thanks for including the midbass horn. I had not thought of W-shapes for midbass. How high do you play them? Could you share the external dimensions for my reference?
Good question, I don't know because I did not try ;-) but possible, probably.
The total exponential horn length is ~106cm -excluding pressure chamber and back chamber- and the mouth area is 1800cm2 and proximity of the floor helps. I had no choice but to make it more compact due to room constraints. It's outer dimensions are 670mm x 624mm x 324mm. 12mm chipboard (cheap). Driver is 20cm/8 inch (my secret ingredient 😉)
That is another good question. I use them "full range" basically and use natural roll-off, 6dB/octave starting from around 400hz. I do filter, but higher up to cut away the highest frequencies that would otherwise resonate or cause other problems. I other words, a horn is a bandpass device and does not require filtering when done (and integrated) properly, perhaps only some protective high pass or low pass filtering. I do not play very loud (up to 100dB maybe) so you can get away with it.
By the way I do not want to hijack this thread so if anyone think so, I'm sorry.
Horneydude - from an inexperienced designer/builder, I find all of the bits and pieces shared here extremely helpful ... but its not my thread.
Hoping this post is related to the initial topic too. Apologies if it is considered a hijack.
Question about integrating midbass horns. Trying to absorb all of the information here and that is leading to more questions.
Consider a scenario in the home environment with DSP.
When integrating a midbass horn at the upper crossover point (ie: to large format horn/compression driver), do you optimize the on-axis, off-axis & power response ? Is it possible to balance all three ? What do you prioritize if optimizing all three is not an option?
What about the directivity of the two horns at the crossover point? Is this compromised ? Is the target to have them matched ? Or does the crossover frequency determine when it matters and when it doesn't ?
Hoping this post is related to the initial topic too. Apologies if it is considered a hijack.
Question about integrating midbass horns. Trying to absorb all of the information here and that is leading to more questions.
Consider a scenario in the home environment with DSP.
When integrating a midbass horn at the upper crossover point (ie: to large format horn/compression driver), do you optimize the on-axis, off-axis & power response ? Is it possible to balance all three ? What do you prioritize if optimizing all three is not an option?
What about the directivity of the two horns at the crossover point? Is this compromised ? Is the target to have them matched ? Or does the crossover frequency determine when it matters and when it doesn't ?
My way of optimalisation is rather intuitive, I do take measurements on-axis and at the listening position to adress the worst problems, but the real tuning is by ear and hard work (moving the speakers around, fiddling with dsp settings to understand what happens when you change a parameter, and listening to well known music). You will need correct measurements, however, because your ear/brain is very adaptable and non-linear and has it's moods too. I do not use correction filters in DSP, only digital crossovers/filters and time delay. To get the phase correct between units in the transition band, where they overlap, is very important. Optimizing is also dependent of the room which contributes to maybe 50% to the sound.
My way of matching directivity at crossover point is to have both horns about the same width, and the mouths should be vertically aligned. My mid/high horn is about the same width as the midbass horn. I think it is a bad idea (I tried!) to do time/phase matching by physically move horn mouths back and forth. The mouths should be in the same vertical plane, such that in the transition band, the room reflections match. That is why I think horns are made for DSP or the other way around (time alignment makes your day).
But frankly, I don't really care about directivity. I have the speakers toed in and they beam anyway. I like the "giant headphones" presentation, without the "head in a vice" effect. I do use acoustic treatment like diffusers and bass traps to (partially) remove room influences, though.
Sorry for the woolen, unscientific brabble but audio is also an art, apart from science.
Easiest way I can visualize/'explain' it is to look at a compression horn's theoretical response on axis using HR's 'directivity' option and calculate how many meters away required to flatten it.
As for typical in room response, just like to the first approximation we ideally want a driver/vent offset at a TL's odd harmonic, so goes speakers/our ears (Lp) in room. Combine these two theories and you find that getting an optimal performance out of all but HF horns (> ~ 300 Hz I presume by the pioneer's designs/IME) in a typical HIFI/HT app can be tedious without modern day room EQ/DSP and no doubt in my mind another reason why after Altec bought Lansing in '41 it quickly switched to a truncated, reflex vented, compound (front/back loaded) horn circa '42, which of course was delayed to '45 by WWII, though apparently not available till '47 based on the earliest I've seen was an A800 VoTT invoiced sometime in '48.
IOW, when a large HE (horn) driver (or multiples) with the right specs WRT Fhm/HF WG is designed to merge with the room's acoustics has long since proven the 'hot ticket' to this day for most typical sized rooms all the way up to the few remaining Cinema Palaces and presume IMAX also, though on the small side, no WG is required per se as a large woofer or smaller driver array designed for sufficient polar response to meet the needs of the app is plenty good enough as Altec proved with its scaled down A8-16 series pg. 6 with speakers at the sound wall and LP at the rear wall being the max gain practical in general and speakers in corners, toe'd in as required to 'taste' for a bit more 'horn' (like) performance; and if truly serious, then an 'infinite' corner array to max out efficiency to near/at true full height corner (sub) bass horns.
Designed as a 'system', i.e. drivers too, yes; and now with DSP, then in theory (no 'hands on' experience yet, though 'Hope Springs Eternal') any system design can be done, so best two to 'zero in on' is the on axis (+ ideally off to as much as practical) axis required to cover the Lp with no floor/ceiling 'bounce', side wall reflections till behind ones ears where ideally it will be damped by a diffuse sound wall (i.e. LEDE room), which FWIW in my room is with a large bookcase filled with knickknacks, records and a large variety of book sizes as required to cover ~71% of available wall area.
Since for many this is some/all just a 'pipe dream'; so using furniture, indoor plants, decorative thick towels, small rugs/whatever on walls/hard flooring where there's reflections between the speakers/LP, etc., as listed on myriad sites/forums across the WWW; and for audios 'sake', if you have coffee and/or side/end tables, recommend to at least covering them with a thick comforter, furniture mover blankets or similar for any serious listening and for taller folks, a nice, dense pillow behind the head to 'taste' maybe worthwhile.
@ horneydude - Thanks for the woolen, unscientific brabble. My approach is more or less the same as yours. Also favor the giant headphone presentation, using radials for high and mid/hi horns, known for good wide coverage. Agree with our ears dialing in that last bit of critical detail ... especially to make the system suited to personal taste. I didn't notice much audible difference between physical time alignment and DSP time alignment, could be my room but it wasn't a game changer. Why did you think it was a bad idea? I don't quite follow. Did you hear or measure something that was obviously worse ?
@GM - Appreciate the breakdown. On-axis is my primary focus. The directivity characteristics of horn loaded midbass is what had me thinking it warranted a different integration approach compared to direct radiating midbass cabinet. I'm pretty comfortable with using REW and VTC DLMS4080 for 4way DSP. Thought integrating horn loaded midbass would be more difficult or maybe require other considerations.
My room treatment was necessary, made 4 superchunk floor to ceiling bass traps in all corners, 6 x 12" thick wall panels, some lighter ceiling treatment. Several shelves with vinyl records along back of room, random furniture and my daughters "stuff" all over the place. Before treatment, it didn't matter what I tried with my system, the room was an acoustic nightmare. The end tables and desk are annoying, never thought about covering them with thick blankets. It would be an interesting exercise to see how the room measures when covered.
@GM - Appreciate the breakdown. On-axis is my primary focus. The directivity characteristics of horn loaded midbass is what had me thinking it warranted a different integration approach compared to direct radiating midbass cabinet. I'm pretty comfortable with using REW and VTC DLMS4080 for 4way DSP. Thought integrating horn loaded midbass would be more difficult or maybe require other considerations.
My room treatment was necessary, made 4 superchunk floor to ceiling bass traps in all corners, 6 x 12" thick wall panels, some lighter ceiling treatment. Several shelves with vinyl records along back of room, random furniture and my daughters "stuff" all over the place. Before treatment, it didn't matter what I tried with my system, the room was an acoustic nightmare. The end tables and desk are annoying, never thought about covering them with thick blankets. It would be an interesting exercise to see how the room measures when covered.
I guess what you're saying is that if we take the horn outside, it is fine up close, it doesn't matter and the problem is the room?
In case I'm not hearing you, this is the next step you asked for.
In case I'm not hearing you, this is the next step you asked for.
Right, obviously the HF sounds louder over distance outdoors, ditto indoors relative to the LF before factoring in the room and in my case with a large 26' x 46', 8'/16' half cathedral ceiling room originally and now a ~ 'open' floor plan with ~46' longest path, corner short horn loading from 14 Hz - up was/is my only option for max 'full range' efficiency.
Before the DSP era but with a fully active analog crossover from Thel Electronics, I experimented with placing a mid/high horn straight in the corners for a wide sound stage. and the midbass horn physically aligned in front of it , but I never got the horns to play with one voice and make them disappear. I did not research it with measurements (maybe I will some day) but intuitively, this way of doing time alignment did not work out well for me. It did not look very well, either.
What I mean, is that around the crossover frequency, where both horns play the same frequencies, the mid/high horn mouth in the corner has a very short distance to the back wall, while the midbass horn mouth has a larger distance to the back wall. So the reflections from the back wall are messed up (that is my theory anyway). With back wall, I mean the wall behind the speakers. There is also a back wall behind your back, the same applies there.
When the miniDSP entered the arena, I could align the mouths in a vertical plane and delay the mid/high horn. This way I did finally manage a transparent crossover frequency transition. Now, output from both horns reflect in the same way from the back wall and you can not hear any anomaly in the crossover region, both horns play with the same voice so the transition is seamless which is what you want. Again, the room is part of the system, ultimately.
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