Say we have two choices in designing, say a center channel. We can use smaller drivers and port them to maybe 50hz to use a 100hz crossover point, or, use slightly larger drivers and use eq, specifically a hi shelf filter to achieve a flat response to 50hz for the same 100hz crossover point.
From my understanding we either want to have a flat response on either side of the crossover to achieve proper summing, or use the natural roll off on a drivers low end if it happens to be right where we want to have the next driver with a lowpass. I presently strive for an octave of response with no beaming through at least an octave also but that’s not pertaining to the thread’s purpose but I’d be happy to hear thoughts on this too.
If we use a helmholtz resonator to achieve flat response an octave below the crossover point there will be group delay differences between the mating drivers through the crossover. If we use slightly larger sealed drivers we should have a more consistent group delay throughout the crossover with the group delay being more in the high shelf filter.
Seems reputable loudspeaker companies will be perfectly fine using bass reflex in all the various components of a home theater system. Is it better, when possible, to use sealed drivers in all but the lowest playing drivers? Maybe even all sealed drivers if power and anything else is more of less equal? I personally will always have dsp in any design I take seriously.
From my understanding we either want to have a flat response on either side of the crossover to achieve proper summing, or use the natural roll off on a drivers low end if it happens to be right where we want to have the next driver with a lowpass. I presently strive for an octave of response with no beaming through at least an octave also but that’s not pertaining to the thread’s purpose but I’d be happy to hear thoughts on this too.
If we use a helmholtz resonator to achieve flat response an octave below the crossover point there will be group delay differences between the mating drivers through the crossover. If we use slightly larger sealed drivers we should have a more consistent group delay throughout the crossover with the group delay being more in the high shelf filter.
Seems reputable loudspeaker companies will be perfectly fine using bass reflex in all the various components of a home theater system. Is it better, when possible, to use sealed drivers in all but the lowest playing drivers? Maybe even all sealed drivers if power and anything else is more of less equal? I personally will always have dsp in any design I take seriously.
A lot of energy goes to the center channel in a surround setup, and I would be more concerned about directivity and SPL / Power handling / Headroom than group delay in the crossover region.
So I can´t find good reasons for Not using a vented design.
I myself use a 7 inch vented + 1" dome in a waveguide in the center
So I can´t find good reasons for Not using a vented design.
I myself use a 7 inch vented + 1" dome in a waveguide in the center
Directivity is amongst the higher priorities in any of my projects. It’s a major reason I talk about having an octave of flat, non beaming response on each side of the crossover. I’m preparing to build a center with two Anarchy 554’s, a peerless 1.5” and Dayton nd16 5/8” tweeter. Spl isn’t a main goal for me as I don’t enjoy loudness anymore.
This is more of a broad question with a center channel just as an example. With dsp all around the response can sum properly regardless of the driver’s enclosure alignment? I do prefer the smallest form factor in my builds as a challenge and spouse acceptance factor.
This is more of a broad question with a center channel just as an example. With dsp all around the response can sum properly regardless of the driver’s enclosure alignment? I do prefer the smallest form factor in my builds as a challenge and spouse acceptance factor.
Are there any additional specific methods to sum reflex alignments because of group delay? Also, group delay seems rather unimportant in the bass frequencies but what about once we’re talking into and above the lower midrange and midrange? A few milliseconds can equate to many cycles.
IME only from a construction POV as critically damping a vent yields ~the same or better GD than sealed, so your call.
Attachments
Your question suggests you are pushing your drivers to the bleeding edge, so a couple of dB is actually an issue. I'd rather have a lot of loudspeaker headroom so the issue of sealed or vented is not an issue forced by output. A vented box run in the midrange will always have vent resonances present in the operating range of the speaker. Not my choice.
I think I gave too much information to make the question more inviting and polite. It’s important to have a friendly little story as opposed to just typing a black and white purely utilitarian query for me. I’ll try to reframe the question to be more concise.
For whatever reasons one might choose to implement a helmholtz resonating system in their aim of audio reproduction that is as faithful to the recording as possible, concerning time domain behavior, specifically group delay, are there inherent difficulties in summing through the crossover region?
Is moderate group delay audible through the midbass region? More specifically, the reasonable amount of gd that’s inherent in a speaker system employing passive radiators, that was designed reasonably well.
I don’t particularly care for ports.
For whatever reasons one might choose to implement a helmholtz resonating system in their aim of audio reproduction that is as faithful to the recording as possible, concerning time domain behavior, specifically group delay, are there inherent difficulties in summing through the crossover region?
Is moderate group delay audible through the midbass region? More specifically, the reasonable amount of gd that’s inherent in a speaker system employing passive radiators, that was designed reasonably well.
I don’t particularly care for ports.
Last edited:
I absolutely appreciate everyone’s input here and I’ve learned many things over the years in forums from answers that included things not directly pertaining to the specific base question. The overall spl capability of a center channel is important no doubt. When designing a speaker system with one of the main goals being as small a form factor as possible, some of the biggest compromises are dynamic range and distortion products. I’ve seen evidence of distortion masking In our perception and in certain cases, like a very small speaker design, I can personally tolerate even more.
Cubic foot for cubic foot, I feel like it’s a better approach to use two sealed drivers covering the frequency band as opposed to a reflex alignment but that’s in absence of better time domain understanding. This is of course when the implementation of the two active drivers doesn’t lead to undesirable polar response.
Cubic foot for cubic foot, I feel like it’s a better approach to use two sealed drivers covering the frequency band as opposed to a reflex alignment but that’s in absence of better time domain understanding. This is of course when the implementation of the two active drivers doesn’t lead to undesirable polar response.
Group delay is hard to interpret -- AFAICT it's a bit like CSD plots and a 'peak' in the group delay corresponds to ringing. Commercial designs often seem to tune their vented systems higher to avoid this, which coincidentally gives them a more 'punchy' sound. It may look worse on a simulated frequency plot, but it sells for some reason.
"Power handling" is a bit vague wrt vented vs sealed. Vented designs usually have 2 narrower peaks, so more power is actually consumed for the given output.
For vocal clarity, I would go for a sealed system + electrical high pass, so strong bass signals don't modulate the higher frequencies (assuming there's a sub, so you're basically designing a multi-way system with a shared sub.)
To get consistent phase between the channels, they should all probably be designed with the same speakers, or at least carefully tuned to get the same cut-off.
"Power handling" is a bit vague wrt vented vs sealed. Vented designs usually have 2 narrower peaks, so more power is actually consumed for the given output.
For vocal clarity, I would go for a sealed system + electrical high pass, so strong bass signals don't modulate the higher frequencies (assuming there's a sub, so you're basically designing a multi-way system with a shared sub.)
To get consistent phase between the channels, they should all probably be designed with the same speakers, or at least carefully tuned to get the same cut-off.
I’m partial to the Anarchy woofers which I believe Erin H is responsible for their still being in production. I just feel like they’re diy community gems and even though better choices exist, they’re still cool units. I ordered two 554’s a week or two ago and after reading this and being reminded of it I should probably order two more for future use in a multi channel system’s front stage. It would seem foolish to pretend that they will be around forever considering the 7” models have been long out of stock. I was lazy about ordering the fountek fr59exe drivers and now I have to check ebay so I can hopefully have two as collection pieces.
I think I mentioned somewhere recently that I’m gutting an old polk cs10 center channel I’ve had for years in storage. The drivers will be two Anarchy 554’s sealed, a peerless 1.5” and a Dayton nd16 tweeter. This will be fully active with the Dayton kabd 4x30 board as just a simple “soundbar” that should hopefully sound wonderful while suiting the modest spl requirement of its purpose. Eventually, when I tackle a 3ch theater front I’ll be sorry that I didn’t just order two more 554’s. Heck, I ordered three peerless 1.5’s and three Dayton tweeters.
There's a lot to unpack in your premise including whether or not a centre speaker is a real thing to animals designed to receive stereo. Originally designed clarify voice in theatre systems the concept is flawed. Sidebar: A character on the left of screen should be loudest from the l/h speaker, a saxophonist on the right should be loudest from the r/h speak - a centre speaker just confused the issue and distorts truth - bygones.
Unless you're Don Lafontaine the centre speaker need not respond below 80hz.
Big box manufacturers port everything because it's 3db for free - smaller drivers cost less.
554s don't sound like the most sensitive of drivers, in a sealed cabinet they probably require a lot of power to keep up.
To further denigrate the centre speaker, whatever the frequency there's always another speaker providing cover.
Unless you're Don Lafontaine the centre speaker need not respond below 80hz.
Big box manufacturers port everything because it's 3db for free - smaller drivers cost less.
554s don't sound like the most sensitive of drivers, in a sealed cabinet they probably require a lot of power to keep up.
To further denigrate the centre speaker, whatever the frequency there's always another speaker providing cover.
You could also choose an enclosure volume that provides for an appropriate low frequency cut off without having to add in a high pass filter. Doing so will also increase headroom somewhat.
Might we say that two stereo mains would be ideal for a 1, 2, maybe even three person audience located with sufficient distance if they’re were three listeners. Much more likely it would be me and my girlfriend. I’m a purest when listening to well recorded music but home theater is not at all in my wheelhouse. I’ll say that two beefy bookshelves with sufficient power is plenty for me.
In reality I don’t think it’s one of my utmost priorities to have a stereo front set image like a crystal ball to watch a movie with my girlfriend. Now, when I get home from work earlier then her I can sit dead center and enjoy the imaging I’ve managed to coax from them.
I’m from a car stereo background focusing on one seat tunes so the processing and implementation of a center is completely off my radar until now. I’m a super puritan with my car and am happy to have it suggested to just forget the home theater encumbrance.
I’m from a car stereo background focusing on one seat tunes so the processing and implementation of a center is completely off my radar until now. I’m a super puritan with my car and am happy to have it suggested to just forget the home theater encumbrance.
True, though the pioneer's way minimizes it versus moving towards ~aperiodic, i.e. heavy damping the box and/or the time honored 'sticking a sock in it' (vent).
Don't see a way ATM for me make an overlay of a Hornresp (HR) sim of GD for 'critically damped' BR (CDBR) Vs PR, but looks like the PR is a little lower till near tuning where the BR rather ~abruptly 'flatlines' and the PR shoots up another 2-3 ms before inverting, so leaves me satisfied that to my hearing, etc., comparison (no measurements beyond SPL matched) of my dual 15", ~14 Hz (CDBR) Vs my long gone dual 15" ~14 Hz Servo-Drive PR subs were 'six of one, half dozen of the other' when it came to SQ BW limited to 120 Hz/2nd.