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Title: This or that
Post by: Jeremy McNichol on January 10, 2017, 11:32:03 PM
Hey guys. Looking for anyone with real experiences on running a sub setup with the X1 type design from Rog Mogale. Any significant advantages/disadvantages over a standard front loaded reflex system?
Assuming the same 18" driver used.
Sound quality is #1 priority.
Title: Re: This or that
Post by: Scott Holtzman on January 11, 2017, 01:30:26 AM

Sound quality is #1 priority.


What exactly does that mean?


Quality is such an ambiguous word. 
Title: Re: This or that
Post by: Tim McCulloch on January 11, 2017, 02:21:56 AM
Hey guys. Looking for anyone with real experiences on running a sub setup with the X1 type design from Rog Mogale. Any significant advantages/disadvantages over a standard front loaded reflex system?
Assuming the same 18" driver used.
Sound quality is #1 priority.

Buy Rog's subs.  I don't know if they're better or worse than anything else (and likely better than anything home-brew) but they're part of a loudspeaker SYSTEM.  Why divide a system into "known quantity" and "crap shoot"?
Title: Re: This or that
Post by: Chris Grimshaw on January 11, 2017, 07:16:29 AM
Its a pretty standard 6th order bandpass. Compared to a standard reflex of the same size, you gain a little output at the top end, and lose a little at the bottom. The distortion performance of the X1 ought to be better than a reflex because you've got an acoustic filter there.
That said, acoustically filtering at the top end is a double-edged blade. It'll sound cleaner at high levels, but you won't have much notice when your drivers are struggling, until they fail.

I haven't run the numbers, so I don't know if the air velocity in the ports will be a problem or not. If the port velocity is marginal, you'll get compression at the top and bottom of the passband. Standard reflex would only get compression at the bottom end.

One last thing - I'd experiment with mounting the drivers with the magnet in the small chamber if possible. That'll give you air flow directly across the magnet, and might buy you a bit more thermal power handling.

Chris
Title: Re: This or that
Post by: Ivan Beaver on January 11, 2017, 07:37:16 AM

What exactly does that mean?


Quality is such an ambiguous word.
EXACTLY.

Does quality mean "accurate reproduction"?

Or "louder"? Many associate quality with loudness.  But louder does not always mean the same sound.

Or "have a specific sound that I like, that may not be accurate"?

People often speak about sound quality, but they often don't actually mean that.

To me-sound quality means something that accurately reproduces what is coming into it.

It may not be the most "fun".

Title: Re: This or that
Post by: Steve M Smith on January 11, 2017, 08:16:20 AM
Quality has the full range from abysmal to excellent.  It means nothing on its own.


Steve.
Title: Re: This or that
Post by: David Morison on January 11, 2017, 08:49:31 AM
Buy Rog's subs.  I don't know if they're better or worse than anything else (and likely better than anything home-brew)

I doubt anyone considering homebrew like the X1 would have the budget for proper Void kit, to be fair.

Assuming the same 18" driver used.

6th Order Bandpass boxes often perform best with different drivers than Vented boxes, so why would you want to deliberately skew the comparison with that criteria?

You'll probably find more people with direct experience of the box on the speakerplans forums, if you haven't already checked that out.

Chris G's reply upthread pretty much sums up the main points to be aware of in considering a bandpass box.

One thing I'd add is that because you have the extra lowpass filter at the top end of the box's response, this may complicate crossing over into the rest of your system - so how good are your measurement chops?

FWIW,
David.
Title: Re: This or that
Post by: Stephen Kirby on January 11, 2017, 02:27:48 PM
Use comes into play here.  I have Cubo Subs which are a quasi band pass design as well (Looked at the X1 also).  Originally I thought that the 60Hz hump would give me a thump similar to 728s.  Depending on the music being played that can be okay, or it can get in the way.  On several outdoor things lately I've been taming that out and therefore losing out on some of the efficiency gain.  Starting to think about Keystones or something a bit more neutral.
Title: Re: This or that
Post by: Jeremy McNichol on January 12, 2017, 12:29:46 AM
Thanks for the response(s) guys.
ASSuming I were to use the driver mostly recommended on speakerplans, I would want to be aware of any shortcomings in the X1 design, eg port noise. I have always used reflex boxes and am curious if the X1 has that much of a different"sound" than a reflex, eg (scoops, horns etc). I have built 4th order boxes in the past and am aware of the masking effect that can lead to driver failure.
I don't belong to the audiophool camp so embellishments of how it sounds are not of much interest, thats why I asked here and not speakerplans.
Given the proper LMS settings they should both perform well if used within safe limits..? Correct?
I definitely would not run 2 different types of boxes in the same bandpass at a show.
No I cannot afford Void kit..right now.
I want accurate reproduction,  yes I'm aware that some people think that distortion adds to a bass systems loudness/quality.
Just wanted an objective view if it would be a step up, or sideways. I mean BP6 boxes are slightly more efficient than reflex's?
I really don't want something that sounds like it's farting out dead cats.
Title: Re: This or that
Post by: John Halliburton on January 12, 2017, 08:33:41 AM
Thanks for the response(s) guys.
ASSuming I were to use the driver mostly recommended on speakerplans, I would want to be aware of any shortcomings in the X1 design, eg port noise. I have always used reflex boxes and am curious if the X1 has that much of a different"sound" than a reflex, eg (scoops, horns etc). I have built 4th order boxes in the past and am aware of the masking effect that can lead to driver failure.
I don't belong to the audiophool camp so embellishments of how it sounds are not of much interest, thats why I asked here and not speakerplans.
Given the proper LMS settings they should both perform well if used within safe limits..? Correct?
I definitely would not run 2 different types of boxes in the same bandpass at a show.
No I cannot afford Void kit..right now.
I want accurate reproduction,  yes I'm aware that some people think that distortion adds to a bass systems loudness/quality.
Just wanted an objective view if it would be a step up, or sideways. I mean BP6 boxes are slightly more efficient than reflex's?
I really don't want something that sounds like it's farting out dead cats.

Here's an old rule of thumb.

All things being as equal as possible in the design, a sealed sub will sound better than a vented sub, which will sound better than a sixth order sub.

The best sounding sub is a well designed horn, with the one caveat being that delay thru the sub is greater and needs to be dealt with when tuning the whole system.

There are always tradeoffs.  Rog is a talented designer, I'd make sure to follow his plans and driver specs closely to see results that I would hope have been verified by him and others who have already built this model.

Best regards,

John
Title: Re: This or that
Post by: Rob Spence on January 12, 2017, 11:58:04 AM
Hey guys. Looking for anyone with real experiences on running a sub setup with the X1 type design from Rog Mogale. Any significant advantages/disadvantages over a standard front loaded reflex system?
Assuming the same 18" driver used.
Sound quality is #1 priority.

Not often can you use the same driver in two different designs.


Sent from my iPad using Tapatalk HD
Title: Re: This or that
Post by: Jim McKeveny on January 13, 2017, 08:09:11 AM
Bandpass designs demonstrate encouraging sensitivity advantage in a narrow passband, but if we dig further down the prediction & measurement chain we discover less-than-ideal Group Delay characteristics. This measurement is often credited as an identifier of the tradeoff between steady state v. transient response.

So (to quote Ivan) "It depends"..

BTW- Ivan should host his own forum here. His primary sponsor? Proctor & Gamble's DEPENDS....
Title: Re: This or that
Post by: Jim McKeveny on January 13, 2017, 08:26:40 AM
To me-sound quality means something that accurately reproduces what is coming into it.

And since absolute accuracy is not currently possible, endeavor to minimize distortions and effort to render those remainers de minimus and even-order harmonic in content.

Eeeeasy!. Right?
Title: Re: This or that
Post by: Roland Clarke on January 14, 2017, 04:35:40 PM
Here's an old rule of thumb.

All things being as equal as possible in the design, a sealed sub will sound better than a vented sub, which will sound better than a sixth order sub.

The best sounding sub is a well designed horn, with the one caveat being that delay thru the sub is greater and needs to be dealt with when tuning the whole system.

There are always tradeoffs.  Rog is a talented designer, I'd make sure to follow his plans and driver specs closely to see results that I would hope have been verified by him and others who have already built this model.

Best regards,

John

I'm usually with Ivan on the "it depends" bench, however, I can tell you that in all my years working audio, I've never heard a decent band pass box, from any maker or designer.  The jokes about one note bass aren't accident.  If by quality you mean reasonable reproduction fidelity look elsewhere.

The ultimate I've ever heard in bass fidelity is not a horn but a quarter wave transmission line.  Forget about the TLs of old, some amazing work was done about 17 years ago by George Auspurger and Martin King working independently, both came up with predictable mathematical models.  I have a pair of monitors based on these principles that are head and shoulders above anything else I've ever heard.  No good for PA systems, but Tom Danley's tapped horns use some of the same principles.
Title: Re: This or that
Post by: Chris Grimshaw on January 17, 2017, 09:21:27 AM
I'm usually with Ivan on the "it depends" bench, however, I can tell you that in all my years working audio, I've never heard a decent band pass box, from any maker or designer.  The jokes about one note bass aren't accident.  If by quality you mean reasonable reproduction fidelity look elsewhere.

The ultimate I've ever heard in bass fidelity is not a horn but a quarter wave transmission line.  Forget about the TLs of old, some amazing work was done about 17 years ago by George Auspurger and Martin King working independently, both came up with predictable mathematical models.  I have a pair of monitors based on these principles that are head and shoulders above anything else I've ever heard.  No good for PA systems, but Tom Danley's tapped horns use some of the same principles.

I quite liked my Tannoy T40 until I blew it, though I've moved on to nicer things since.

FWIW, a quarter-wave TL is perfectly usable in a PA situation. I recently built and tested one. 123dB continuous from 38Hz upwards from a single 15", in a cab you could carry (just) with one hand. Since you can keep the port area pretty big, there was minimal compression showing up until the amplifier clipped.

Chris
Title: Re: This or that
Post by: Roland Clarke on January 17, 2017, 09:38:03 PM
I quite liked my Tannoy T40 until I blew it, though I've moved on to nicer things since.

FWIW, a quarter-wave TL is perfectly usable in a PA situation. I recently built and tested one. 123dB continuous from 38Hz upwards from a single 15", in a cab you could carry (just) with one hand. Since you can keep the port area pretty big, there was minimal compression showing up until the amplifier clipped.

Chris

The trouble is preventing overexcursion of the cone.  Mine will move with a 7hz signal put through them.  I believe that even with the tapped horns they have to put a steep hpf in.  I would expect that in reality it would be very difficult to satisfactorily achieve the spl's we are used to with other sub systems, although contrary to popular myth tl's do not need to be as long or large as was once considered.
Title: Re: This or that
Post by: Chris Grimshaw on January 18, 2017, 06:29:26 AM
The trouble is preventing overexcursion of the cone.  Mine will move with a 7hz signal put through them.  I believe that even with the tapped horns they have to put a steep hpf in.  I would expect that in reality it would be very difficult to satisfactorily achieve the spl's we are used to with other sub systems, although contrary to popular myth tl's do not need to be as long or large as was once considered.

Unloading below tuning will happen with anything that doesn't have a sealed chamber. Ported boxes, 6th order bandpass, tapped horns, back loaded horns... You name it. They all suffer below their bottom tuning frequency. Front-loaded horns and sealed boxes are the only ones that don't.

Transmission lines are weird, with a lot of different cabinets having that name attributed to them. Mine are simply a slightly-tapering line that's tuned for a quarter-wave resonance in the high-30s. A traditional TL is optimally damped to totally flatten the low-frequency impedance peak. The ones that do manage that will effectively have an infinite baffle response, since the enclosure just absorbs the back wave. With modern drivers, that's not particularly useful - their motors are much stronger than drivers of old, so they don't need to see an infinite enclosure to get decent LF response. You can use a smallish sealed box and get basically the same thing, without having to move that huge enclosure. Most TLs in use today are quarter-wave resonators, which will provide reinforcement at the bottom end, like a ported box will.
The quarter-wave one I built (others are available) responds in a similar way to a ported box. Indeed, you can remove a couple of internal panels and get a ported box. I'll be trying that to see if there's much difference between the two, taking a hole saw to the panels.

Chris
Title: Re: This or that
Post by: Roland Clarke on January 19, 2017, 06:51:53 AM
Unloading below tuning will happen with anything that doesn't have a sealed chamber. Ported boxes, 6th order bandpass, tapped horns, back loaded horns... You name it. They all suffer below their bottom tuning frequency. Front-loaded horns and sealed boxes are the only ones that don't.

Transmission lines are weird, with a lot of different cabinets having that name attributed to them. Mine are simply a slightly-tapering line that's tuned for a quarter-wave resonance in the high-30s. A traditional TL is optimally damped to totally flatten the low-frequency impedance peak. The ones that do manage that will effectively have an infinite baffle response, since the enclosure just absorbs the back wave. With modern drivers, that's not particularly useful - their motors are much stronger than drivers of old, so they don't need to see an infinite enclosure to get decent LF response. You can use a smallish sealed box and get basically the same thing, without having to move that huge enclosure. Most TLs in use today are quarter-wave resonators, which will provide reinforcement at the bottom end, like a ported box will.
The quarter-wave one I built (others are available) responds in a similar way to a ported box. Indeed, you can remove a couple of internal panels and get a ported box. I'll be trying that to see if there's much difference between the two, taking a hole saw to the panels.

Chris

Whilst a lot of that is true,  generally, tl's are generally shorten than 1/4 wave these days.  The big mistake of old was the general consensus that the damping within the cabinet slowed the speed of the sound.  When this assumption was eventually disproved the maths started to work and a lot of the "rule of thumb" and "trial and error", design.  Martin Kings worksheets are a great starting place.
Title: Re: This or that
Post by: Chris Grimshaw on January 19, 2017, 09:37:42 AM
Whilst a lot of that is true,  generally, tl's are generally shorten than 1/4 wave these days.

Tapering them will push the tuning frequency down a bit, though there are limits of course. FWIW I use Hornresp, but keep meaning to learn Akabak.

Chris
Title: Re: This or that
Post by: Roland Clarke on January 19, 2017, 12:31:46 PM
Tapering them will push the tuning frequency down a bit, though there are limits of course. FWIW I use Hornresp, but keep meaning to learn Akabak.

Chris


http://leonardaudio.co.uk/transmission-line/help-file/

For TL's the Leonard audio program works and seems to correlate with Martins own calculations.
Title: Re: This or that
Post by: Jeremy McNichol on January 21, 2017, 11:49:16 PM
Ok, so transient response suffers with 6th order bandpass. Maybe I should just stick with reflex then.
Hmmm , what about a big vent reflex? Is the yorkville LS808 a back loaded horn or just a big vent reflex?
Title: Re: This or that
Post by: Ivan Beaver on January 22, 2017, 09:03:41 AM
Ok, so transient response suffers with 6th order bandpass. Maybe I should just stick with reflex then.
Hmmm , what about a big vent reflex? Is the yorkville LS808 a back loaded horn or just a big vent reflex?
The advantages of a large port/vent is the ability to pass the audio without chuffing or "shutting off".

If the port is to small, it will make various noises at higher levels (chuffing) and could possibly actually cut off or choke the cabinet-more or less turning it into a sealed box alignment.

The downside to a large port is that it MUST be longer/deeper.  So the cabinet size gets larger.

You you have to weigh the performance vs size issue.  In most cases the performance side is the one that "takes the hit".

It is all a matter of trade offs