Markaudio 7MS and CHP90 enclosure options

I've been looking at enclosure options for the Markaudio 7MS and CHP90.
Ideally I would like to build one enclosure suitable for both, but I recognise that this might be far fetched.

What I've found interesting is that opposed to a regular BR, some of these more complex enclosures have wide backwave output in the mid bass, mitigating baffle-step losses.
Just look at this one from @nandappe :

chp 2.jpeg


chp.jpg


And here is a comparable one for the 7MS:

7ms 2.jpeg
7ms.jpeg


I've also looked at the Okapi compact MLTL for the 7MS: https://www.markaudio.com/wp-content/uploads/2022/08/Okapi-7MS-compact-MLTL-metric.png
Would this achieve some of the same effect? (wide backwave output up to 700-800 Hz to mitigate baffle-step)
Is there an enclosure that would be suitable for both the 7MS and the CHP-90? (adjustable duct length etc)
 

Attachments

  • chp.jpg
    chp.jpg
    152.7 KB · Views: 120
Last edited:
I defer to people more competent than myself, but FWIW:
What I've found interesting is that opposed to a regular BR, some of these more complex enclosures have wide backwave output in the mid bass, mitigating baffle-step losses.
Just look at this one from @nandappe :
That's an extreme nearfield measurement of the vent output & will likely have a much narrower BW if measured at a greater distance (not practical except in freefield conditions). Realistically, for a bass load you don't want the cabinet to be producing anything significant > ~300Hz or group delay will become an issue.

I've also looked at the Okapi compact MLTL for the 7MS: https://www.markaudio.com/wp-content/uploads/2022/08/Okapi-7MS-compact-MLTL-metric.png
Would this achieve some of the same effect? (wide backwave output up to 700-800 Hz to mitigate baffle-step)
No, it's an MLTL rather than an ML-Voigt / ML-horn like Nandappe's so it has a slightly narrower operating BW. However, the driver has a naturally rising LF response < 500Hz which largely counters typical step-loss, so it doesn't need as much assistance from the enclosure (unless you need greater LF headroom, in which case a horn is needed).
Is there an enclosure that would be suitable for both the 7MS and the CHP-90? (adjustable duct length etc)
Not ideally. In can be done, & on paper they have similar Vb requirements due to the former's higher Q, but power handling will suffer given that it's about 40% down in size terms, so you need to be a mite careful.
 
frugal-phile™
Joined 2001
Paid Member
Ideally I would like to build one enclosure suitable for both, but I recognise that this might be far fetched.

Haven’t played much with the CHP90 yet but i believe it needs a much larger enclosure than the A7ms.

You might get lucky with an enclosure where the enclosure dominates, and there is some tunability.

A7ms fits Frugel-Horn Mk3, you might be able to squeeze the CHP90 in, but i suspect it would be happier in FHXL.

dave
 
According to the on-axis measurement of the CHP-90 in initial post #1 , the eighteen decibel "hole" from 120 hertz to 250 hertz...pity the musician whos' instruments fall into that frequency range, their performance "disappearing"...Not Hi-Fi ,..
rather, No-Fi ...

--------------------------------------------------------------------------------------------------------Rick...
 
According to the on-axis measurement of the CHP-90 in initial post #1 , the eighteen decibel "hole" from 120 hertz to 250 hertz...pity the musician whos' instruments fall into that frequency range, their performance "disappearing"...Not Hi-Fi ,..
rather, No-Fi ...

The large dip is due to the room, and the same dip will occur in Frugel Horn Mk3.

7HD+FH3.jpg
 
According to the on-axis measurement of the CHP-90 in initial post #1 , the eighteen decibel "hole" from 120 hertz to 250 hertz...pity the musician whos' instruments fall into that frequency range, their performance "disappearing"...Not Hi-Fi ,..
rather, No-Fi ...

Er -could I gently point out that isn't an 'on-axis measurement of the CHP-90'. It is in fact an on-axis in-room swept-sine measurement of a CHP-90 in a particular ML-horn in a particular room acoustic.
 
I installed Alpair7MS on DDVP-12.5-ML.
It has a lot of bass for me, but it seems to be good for bass lovers.

Wow, seems to work great! Seems I can just build this with a removable baffle for both the 7MS and CHP-90 :D
Do you have plots for more enclosures? What does the vent output look like for a MLTL for instance?

No, it's an MLTL rather than an ML-Voigt / ML-horn like Nandappe's so it has a slightly narrower operating BW. However, the driver has a naturally rising LF response < 500Hz which largely counters typical step-loss, so it doesn't need as much assistance from the enclosure (unless you need greater LF headroom, in which case a horn is needed).

Not ideally. In can be done, & on paper they have similar Vb requirements due to the former's higher Q, but power handling will suffer given that it's about 40% down in size terms, so you need to be a mite careful.

All the Markaudio drivers I've tried (P7HD, MS7, Maop 11) have had too little energy below baffle step cutoff (typically around 3 db).
Although less loss than your typical driver, I haven't found a way around having to provide BSC.

Hence my interest in the TQWT enclosure which seems to provide gain over a wider bandwidth than the old BR box I've always built.
What does the gain bandwidth of a MLTL look like in comparison?
 
According to the on-axis measurement of the CHP-90 in initial post #1 , the eighteen decibel "hole" from 120 hertz to 250 hertz...pity the musician whos' instruments fall into that frequency range, their performance "disappearing"...Not Hi-Fi ,..
rather, No-Fi ...
so DDVP-12.5-ML (TOWT) may not be the best box plan for the driver which doesn't appear to have the deep dip ~ 150 Hz - 202 Hz

chp-90.jpg
 
Er -could I gently point out that isn't an 'on-axis measurement of the CHP-90'. It is in fact an on-axis in-room swept-sine measurement of a CHP-90 in a particular ML-horn in a particular room acoustic.
So just how are we suppose to "A B" two differing drivers in two different enclosures in two different room acoustics?...too many variables. This is why we must have a baseline (same) enclosure, and a baseline room, we used to use anechoic chambers... Room acoustics can be virtually infinitely "adjustable"...an absorption panel here, there...even down to a particular paint on a "live" surface.
Even the Alpair 7MS according the graphing has a giant hole centered at 300 hertz down 25 decibels...the note on a piano is D4, at 293.665 hertz ...this note would essentially disappear with this loudspeaker.


-----------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
 
So just how are we suppose to "A B" two differing drivers in two different enclosures in two different room acoustics?...too many variables.
You can't. I was simply pointing out that you said:

According to the on-axis measurement of the CHP-90 in initial post #1 , the eighteen decibel "hole" from 120 hertz to 250 hertz...
...when that is not in fact a measurement of the CHP-90, but an in-room system response measurement, i.e. a 1m in-room combined response of drive unit, enclosure and room acoustic. You can't just take a system response plot like that and casually hang responsibility for an LF cancellation on the drive unit, whatever it is.
 
Last edited:
  • Like
Reactions: 1 user
Smoothing?...So can I wander onto a stage, pull out my power-screwdriver & cinch down someone's D4 key on their piano saying , the smoothing process in our brains will make this one particular key not noticeable.


----------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
 

Attachments

  • Stienway.jpg
    Stienway.jpg
    339 KB · Views: 37
I was just comparing the CHP-90 and A7-ms and got surprisingly similar results for a sealed box @ around 10L for both. I ended up getting the CHP-90 for its higher sensitivity and likely higher bass limits.

Plug both into Hornresp as separate project tabs, and switch back and forth between them to see if you can get a box that's roughly an equal compromise for both. In my case the customer wants sealed, so I can't make a TL, but that's what I would otherwise consider.

The smoothing process in our brain will make the peaks and dips in the graph less bothersome.
My brain seems to lack this software package. If there's a one-note peak somewhere, I must order a custom PCB with the appropriately tuned analogue notch filter, or else I won't sleep.
 
Last edited:
All the Markaudio drivers I've tried (P7HD, MS7, Maop 11) have had too little energy below baffle step cutoff (typically around 3 db).
Although less loss than your typical driver, I haven't found a way around having to provide BSC.
The amplifier's output impedance could provide some tunability. At least with closed and aperiodic boxes, raising the output impedance would give a bass boost that tends to follow the driver's impedance curve. It's probably a bit more complicated for TLs but my guess is that the drive 'softness' could be fine-tuned to damp the port/line resonances.

A few ohms (to a few 10s of ohms) in series with the speaker would provide a relative boost to the treble as well, which could be a good fit for the "Japanese tuned" drivers. Alternatively, if the treble is too hot, a small high gauge coil could be added, where its high DCR doesn't matter is a useful part of the tuning.
 
Last edited:
All I'm trying to say, let's not "sugar coat" a lousy response by "smoothing"...Let's use the highest resolution possible & then we can resolve these large peaks & valleys with the tools at our disposal...be it room tuning, a plain 31 band EQ, or a more permanent notch & band approach. With the kaleidoscope of enclosure types, choose one that "fixes" the most glaring of shortcomings & go forward from there.


--------------------------------------------------------------------------------------------------------------------------------------Rick...
 
I'm slightly lost about what you are suggesting? That the presence of room modes (which is what you are complaining about is) means a system is unlistenable and the owner shouldn't bother?
If indeed this graphing IS exactly the performance of this particular driver/enclosure/room response ...then no, this is absolutely unacceptable. Our perceptions likely will be, "sounds OK, but something's wrong & I can't put my finger on it"...this is why we have our machines, they can literally hear vastly better than we could ever do, so why not aspire to a level of perfection?
I had an opportunity awhile ago to visit an acquaitances studio & work the gear listening to music...the fellows control room with the monitors made for wonderful listening environment....then the guy had me step into the session room, the big acoustic door closing behind me...you gotta listen thru the big monitors!....so I went from dialed in board monitors to big PA type monitors.......day & night...my wincing facial reaction had him saying, yeah I know, sounds like crap.


----------------------------------------------------------------------------------------------------------------------------------------Rick...
 
If indeed this graphing IS exactly the performance of this particular driver/enclosure/room response ...then no, this is absolutely unacceptable.
So unless I've missed something:
  1. You were describing a complete in-room system response taken at a single point in space under the name of the drive unit only, and
  2. You are stating that unless a person's in-room system response adheres to whatever your unspecified personal criteria may be, they shouldn't even bother listening.
 
Last edited:
  • Like
Reactions: 1 user