Just figuring since the HiVis are pretty inexpensive may be worth getting them and do the A-B since the mid will so important to the overall speakers sound? Can always sell whatever you don't want on Ebay...
these are only £145 each in uk seems like excellent value for money I'll get some inthink wish I'd noticed the price earlier
@Michael Chua How old are your DMB-As? Qms is more than 4.0, Qts is over 1 5, Le is 0.12mH@10k and Fs is 660hz on most of mine. I played 300hz @ 4V for a few hrs to break them in and there was little change.
You mentioned an LCR trap at Fs, which I feel is mandatory to get decent lower mid performance on these things. By the time you factor in the parts cost of an Fs LCR, the price doesn't look that attractive anymore.
The main problem I'm seeing with the current batches of these mids is inconsistencies in TSPs depending on date of manufacture. It would require matching up each pair to specific xover implementations. This appears to be a common issue with cheap mid domes IMO.
The Morel MDM55 may be expensive in comparison, but its a much more refined and better performing driver which is alot easier to work with, plus its very consistent.
Based on overall performance and price, the Morel MDM55 (CAM558) and ScanSpeak D7608-9200 are the best choices for readily available dedicated mid domes. I'd consider a cone driver over the bargain basement domes in most cases unless you want to do alot of xover design to get the best from the cheap domes. Then you have the issue of finding replacements if something goes wrong, which IMO is the greatest risk of using budget drivers. You should always buy spares from the same batch/date just to be sure.
You mentioned an LCR trap at Fs, which I feel is mandatory to get decent lower mid performance on these things. By the time you factor in the parts cost of an Fs LCR, the price doesn't look that attractive anymore.
The main problem I'm seeing with the current batches of these mids is inconsistencies in TSPs depending on date of manufacture. It would require matching up each pair to specific xover implementations. This appears to be a common issue with cheap mid domes IMO.
The Morel MDM55 may be expensive in comparison, but its a much more refined and better performing driver which is alot easier to work with, plus its very consistent.
Based on overall performance and price, the Morel MDM55 (CAM558) and ScanSpeak D7608-9200 are the best choices for readily available dedicated mid domes. I'd consider a cone driver over the bargain basement domes in most cases unless you want to do alot of xover design to get the best from the cheap domes. Then you have the issue of finding replacements if something goes wrong, which IMO is the greatest risk of using budget drivers. You should always buy spares from the same batch/date just to be sure.
Made a new entry for the Morel TM4055 combined tweeter-mid; unique for its integrated tweeter thus compact c.t.c. spacing
I built a front three of the Zaph 3.5's back in the day....sounded great then....i still use the center channel in my main theater today.....the vocal clarity on speech and singing is eerie. These are 52A's though so take the above with a grain of salt......no breakup mode though
The RS52ANs sound considerably cleaner and more open when suppressing the top end breakup, even if its well outside the passband after the crossover.
HiVi had the TM1a dual driver combo like the TM4055. Not sure if it's totally NLA, but combines the DMNa and TN25. 2 versions exist with regards to flat metal faceplate or sculpted plastic, and the related capped small chamber or bullet shaped larger chambers.
I used the flat metal faced and capped chambers version in my NEHD speakers.
I used the flat metal faced and capped chambers version in my NEHD speakers.
Seems another one NLA for a couple years now. In case people weren't aware, the kind of expensive D3806 has been discontinued by Scan but is still available to buy atm; maybe it will be on sale at some point before they run out.
Does anyone know why some midrange domes do not have a closed/sealed rear? For example, consider the 3" Scan-Speak D7608/920010. Or, can we tune these midrange domes based on the midrange enclosure? If so, what parameters can we tune?
They have decent power handling, I cross them at 800Hz second order to a 7" woofer. The bigger issue IMO is rolling them off at say 3,500 - 4,000 Hz to avoid the break up that occurs around 10-11 kH.
I use the online calculators below depending on whether I have a sim program handy. Its essentially a series or parallel notch (sometimes a combination depending on severity of peak) which either increases or decreases impedance at that peak for less output. The series notch (used in parallel with the driver) needs some kind of resistance (ie low pass or high pass components of filter) in series to not end up with a difficult to drive impedance dip, but its arguably more effective at dampening the resonance independent of driver load impedance. The parallel notch is easier to implement but is impedance linearity sensitive ie any driver induced impedance fluctuations will interact with the notch circuit (usually unfavorably) causing unpredictable filter output variances.
In your case you want to remove the 10k ish dome resonance peak. There is a potential drawback doing this depending on if the peak frequency wanders moving off axis of the dome. The issue usually shows up with tall dome profiles causing a phase shift due to the speed of sound within the dome being faster than the airborne sound emitted from different locations around the dome surface. The best way to deal with this is using a small phase shield (ie piece of thin felt about 10 - 15mm in diameter glued to center of front grille). In many cases the phase shield alone will attenuate the peak sufficiently without the electrical filter. YMMV
www.mh-audio.nl/Calculators/ICTAPX.html
www.mh-audio.nl/Calculators/parallelnotchfilter.html
For those wondering whats under the felt of the SS D7608, here's a picture.
The felt (removed to test various chamber and dampening configurations) provides flow resistance to the dome. However, its synthetic based material which isnt sufficient in quantity or quality to lower the system Q to the point of reducing low end response overshoot to reasonable levels for better linearity, lower THD and impulse response. Not addressing this area properly leads to compromised performance which has tarnished this otherwise excellent mid's reputation. If this issue is overlooked, the dome won't achieve its full SQ potential.
The dampening mod is too long and detailed to fit in one post. I'll try to explain most of it soon, but for starters the goal is to drop system Q to under 0.8 (from over 1.5 in stock form). I've tried various notch filters at Fs to achieve this, but the mechanical dampening is far more effective and vastly improves performance when the dome is crossed under 800 hz. Without extra mechanical dampening, the dome will struggle to play loud and produce a very shouty sound. More to follow...
The felt (removed to test various chamber and dampening configurations) provides flow resistance to the dome. However, its synthetic based material which isnt sufficient in quantity or quality to lower the system Q to the point of reducing low end response overshoot to reasonable levels for better linearity, lower THD and impulse response. Not addressing this area properly leads to compromised performance which has tarnished this otherwise excellent mid's reputation. If this issue is overlooked, the dome won't achieve its full SQ potential.
The dampening mod is too long and detailed to fit in one post. I'll try to explain most of it soon, but for starters the goal is to drop system Q to under 0.8 (from over 1.5 in stock form). I've tried various notch filters at Fs to achieve this, but the mechanical dampening is far more effective and vastly improves performance when the dome is crossed under 800 hz. Without extra mechanical dampening, the dome will struggle to play loud and produce a very shouty sound. More to follow...
Attachments
Here is my crossover for RS52AN. This was for a 3way 6" + RS52AN + miniAMT, flat baffle, system sensitivity ~86dB.
