The dome midrange thread

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#1,321
profiguy said:
Sorrt.for rhe long post, but I feel this applies strongly to the preference of using mid domes
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Valued your experience a lot 👍

It is precisely this kind of information that is most instructive for ALL of us with varying degrees of knowledge.
Everyone benefit such "life experienced" practical "tweaks" info.

Those "geniuses" who discuss & explain things at an high engineering level "only reach" maby 5-10 % of the forum's members, but still are a highly valuable knowledge, but this reach everyone.

Again thanks!
 
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#1,322
profiguy said:
Regarding the D7608s, some of you are already finding out the complex dependency of rear chamber volume and lower mid performance. This is where the issues reside, as there is a strong correlation between chamber volume and lower mid HD/FR.

When comparing the wonky factory FR curve and corrected FR with any type of chamber between 350 - 750 ml, its apparent the D7608 was never intended to be used without some type of rear chamber. Adding to that is the felt on the motor structure, where things get even more weird. There is definitely some performance to be gained by optimizing this air flow restriction and the net chamber volume. The question is, how much snd what type of felt is needed for a given net chamber volume. The relationship I discovered is the felr should only be modified if the target lower mid HP is below 500 hz. Above this, the felt is pretty close to optimal for larger chamber volume. I'm honestly not sure what material they used for the rear felt, but it does appear to be some type of mix between synthetic and natural fibers.
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So I have a .56 L rear chamber with the pictured damping material . The material at the back of the chamber is denim damping , then in front of that two layers of Dacron batting. This pretty much fills the chamber without packing the dacron batting down. Should this get me in the ballpark using a 700Hz 12db highpass ? I left the felt on the back of the motor as is.
mid damping.JPG
 
#1,323
profiguy said:
My preferred HF HP is actually 3.2 - 3.5k and having the horizontal off axis response dip slightly at that frequency. This allows fine tuning the speaker by angling it in or out towards the sweet spot. It reduces the 3.5k range off axis (preferably by a few dB), which sounds far better to the ears, especially at higher volume levels (aka Fletcher Munson or BBC dip).
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Testing your recomedations a little on my latest diy (my 9 driver linesource)
Is it someting like this (RED curve) you mean ?
 

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#1,324
Found in the web, allegedly from an older version of the Harbeth website:

According to Harbeth's founder, who worked at the BBC during the time that this psychoacoustic effect was being explored, the primary benefit this little dip gave was in masking of defects in the early plastic cone drive units available in the 1960's. A spin-off benefit was that it appeared to move the sound stage backwards away from the studio manager who was sitting rather closer to the speakers in the cramped control room than he would ideally wish for. (See also Designer's Notebook Chapter 7). The depth of this depression was set by 'over-equalisation' in the crossover by about 3dB or so, which is an extreme amount for general home listening. We have never applied this selective dip but have taken care to carefully contour the response right across the frequency spectrum for a correctly balanced sound. Although as numbers, 1kHz and 4kHz sound almost adjacent in an audio spectrum of 20Hz to 20kHz, the way we perceive energy changes at 1kHz or 4kHz has a very different psychoacoustic effect: lifting the 1kHz region adds presence (this is used to good effect in the LS3/5a) to the sound, but the 4kHz region adds 'bite' - a cutting incisiveness which if over-done is very unpleasant and irritating. You can explore this effect for yourselves by routing your audio signal through a graphic equaliser and applying a mild cut in the approx. 1kHz to 4kHz region and a gradual return to flat either side of that.
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Reference for the soundstage effect: https://de-m-wikipedia-org.translat...l=auto&_x_tr_tl=de&_x_tr_hl=de&_x_tr_pto=wapp

The "BBC-Dip" comprises a FR range of 1-4kHz and might be used for design compromises or even goals that sound "good".
 
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#1,326
Troy Madden said:
So I have a .56 L rear chamber with the pictured damping material . The material at the back of the chamber is denim damping , then in front of that two layers of Dacron batting. This pretty much fills the chamber without packing the dacron batting down. Should this get me in the ballpark using a 700Hz 12db highpass ? I left the felt on the back of the motor as is. View attachment 1450537
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You'll want to only use the denim material. Dacron is actually lousy at dampening lower mid frequencies and reduces volume in larger volumes. Its advisable to orient the material with fibers running from front to back and fill loosely. That should get you close.
 
#1,330
@diceman Yoir observations of the ATC mid dome are on point. They do suffer from uneven directivity towards their upper limit. The WG has something to do with this including the wider surround. The depression of the VC to surround and dome junction causes weirdness with the WG. That's the major issue IMO but there's also the phase difference between the tip of the dome and lower sides which can be aggravated by the WG. Some domes use a phase shield which helps, buts its more of a bandaid IMO, maybe except for the Visaton DSM50. That one has a decent phase shield design.

Volt B250 is an excellent LF driver with good mid band behavior. The dustcap is designed nd sized properly on those. You'll be higher than 97dB in some areas in the curve above baffle step, more like closer to 99 dB if the woofers are in a tighter 2 x 2 orientation. If you stack them vertically, its a little less than 97 dB @ half WL point.

I'd choose the T34B if you're going to push the levels. The T25B is great, but not as sensitive and won't keep up crossed 3 - 3.5k. Id also be concerned with thermal power handling. A smaller 3 way would be fine with the T25B.

The D76AF are excellent mids. Fussy in the bottom area with analog filters but beautiful upper end. Not as good as the mids from the NS1000s.
 
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#1,331
@jawen Keep in mind the exact perfect center frequency for the mid dip i menrioned varies a little from person to person. Its actually a resonance caused by the shape and size of the Pina. You can hear this by pushing back on your ears and listening to music. The midrange balance changes considerably. Thats why those binaural dummy heads with mics in them have ears. The Jecklin disc doesn't consider this, being a simpler flat circle with angled mics on either side. The distance from the mics to the dividing surface creates a bump in response, but not in a predictable place.

Anyways, you'd want to experiment exactly where your own Pina center frequency peak lies. It can be anywhere from 2.5k - 4k. 90 percent of people are right in the middle at about 3.2k.
 
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#1,332
Any recommendations for sub $100 tweeter to pair with a single D7608 per speaker crossed at ~3KHz? Not interested in super high output, but I do rock out every now and then. I was thinking something a bit narrower to hopefully better match the mid. Am thinking of 22W/4534G00 for woofer, probably sealed. I'll be using subs as well
 
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#1,337
Troy Madden said:
Yes, FR, distortion, CSD are all excellent. A great tweeter at any price.
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My only reservation was the presumed directivity mismatch at 3k compared to the d7608. Looking at hificompass measurements it seems wider than manufacturer spec sheet, but still pretty narrow. I guess it won't be too objectionable. I had even thought about putting them in waveguides to match them up better. I haven't really heard firsthand the consequences of directivity mismatched drivers, so I don't know if it's worth fussing over too much, or the threshold at which it becomes objectionable under normal listening conditions
 
#1,338
Bryguy said:
Any recommendations for sub $100 tweeter to pair with a single D7608 per speaker crossed at ~3KHz? Not interested in super high output, but I do rock out every now and then. I was thinking something a bit narrower to hopefully better match the mid. Am thinking of 22W/4534G00 for woofer, probably sealed. I'll be using subs as well
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I'd be very interested in a design with D7608 and 22W/4534G00. It should have good sensitivity, like 90db, and should have a pretty smooth response. Troels liked that midbass in his Discovery 81. I like sealed, and it should go low enough not to have to use a sub, like 62hz F3.
 
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#1,339
andyjevans said:
I'd be very interested in a design with D7608 and 22W/4534G00. It should have good sensitivity, like 90db, and should have a pretty smooth response. Troels liked that midbass in his Discovery 81. I like sealed, and it should go low enough not to have to use a sub, like 62hz F3.
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I'll be happy to share my results. My design skills are wanting, but maybe it will turn out well enough to warrant replication. If there turns out to be any interest beyond yours, maybe some more seasoned DIYers around here can contribute to the design process to make it into something worth the effort. I'd certainly welcome that. It would motivate me to make quick progress, rather than dragging it out into a year long project as is my tendency lol

The Scans woofer has been used successfully sealed before: https://heissmann-acoustics.de/en/suzie/

Looks about 88dB sensitivity, with totally adequate bass extension. Doesn't really start to drop off until ~50Hz in his design. Subs likely wouldn't be necessary, but I have em. Might as well use em

Sorry if this has gone off topic
 
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#1,340
Is WO24p-4 a good bass woofer with D7608?
(Or with similar mid domes, EM 1308, M74P, M74S)


I know there has been recommendation for textreme version, but i feel i might want to try paper version instead.
Reasons for this is:

-Using single driver with about: 91db sensitivity, would like to make single driver design instead of two drivers..

-I feel paper version might have smoother tone.. I want to use 2:n order with bass, so it will bleed into the midrange and i prefer smooth tone..
Will textreme give this to me with it's harder cone?

-Using it either in closed or aperiodic box.. I know paper coned WO24 had been optimized for closed, but is the textreme similar?

I heard A26RE used with careful aperiodic tuning (Senior speaker builder who did tune it by ear), and it had quickest transients i have ever heard,
the drum kicks from opeth started from nothing and stopped to the wall, i was flabbergasted..
(I probably can also try this with vented, as i can gradually close the vent, but anyway..)
 
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