Hi tvrgeek,
I respect your view, but I don’t fully agree.
If I stuff the port on the ZA-SR71 to make it a closed box, wouldn’t it be John’s design? In my opinion it’s still John’s design even if the enclosure volume is increased and the port tuning is lowered as long as the chosen driver units, cross-over design, baffle dimension and driver unit layout is the same. Hey, I even used the same brand for the cross-over components as offered in the Madisound kit. 🙂
If I choose other internal wiring, stuffing and a different brand for the cross-over components than John's isn’t it still his design?
Shure it’s a variant, but I still think it’s the ZA-SR71, but with a personal tweak/tuning to fit personal bass preferences. I would say that at least 95% of the original design is still there and he do offer a lot of tuning options at his website that would change the original design a lot more.
Sorry for the long reply and if I misunderstood you! 😉
Regards
/Göran
I didn't think that there was. I was meaning if the calculated Mms happened to differ so much from SEAS then I'd think something had gone wrong during the measurement process. Afterall Mms is one of those parameters that should remain identical across all measurement platforms. Of course when you're making these measurements for yourself, you are going to see some variation due to the nature of how things are calculated.
Yes and no. IMHO, it is in essence his design, but it is not as he designed it, and it is not as he would have expected it to be used. Therefore, it is not his design, in spite of the fact that the changes made were arguably trivial.
This is purely academic in and of itself, not least because he might have included several different design options, in which case this modification would almost have certainly been encompassed such that it would still be his design". Sorry for the run-on sentence.
Thank you 454Casull,
I think you summed up what I meant here, but the language barrier came in between. 🙂
Just because I chose to increase the enclosure volume doesn’t justify me to claim it my design, but I could call it my design choice variant, I guess. 😉
Yes, I agree with you. This is purely academic, but in my world the essence of the design is the driver unit selection, the baffle lay-out and the cross-over design. The exact enclosure volume and port-tuning, closed box or not are tweaks/tuning free for all to explore without changing the heart and soul of the design, so to speak.
Sorry for misunderstanding!
Regards
/Göran
A big issue to watch. This is why the preferred method is not nickels, but a chunk of blue-tac that is carefully weighed. It is also a reason to compare at least two of the three methods.
I am all for giving the originator credit. Inspired by, modified, variant, whatever. Never would I claim it as my own. The reason I suggest variant is I have seen variations built on a good design that for some reason, baffle size, placement, cabinet issues, or other changes, so it does not perform as the designer intended, then the design was criticized. So, it is only the originators design if it is built true to his specification. This would include design options, as John is apt to suggest. Yep, every bright idea we may have may not actually be an improvement. Hard to believe eh? 😀
If you use this 2" port from PartsExpress with a length of about 15cm you get a port tuning of 38Hz.
Port Tube 2" ID Adjustable 260-387
For fine-tuning you need to measure.
Regards
/Göran
I'm somewhere in the middle...😀, my ER18s are in a 24 L box, currently tuned to 37Hz, but that's way too lean for me, I'll be tuning them to somewhere in the low 40s once I've measured them again. Last night I fed them from from a much better source than my dodgy old computer, & I think that I'm going to have to add the BSC inductor to pull these drivers into line (I've been using a .5 helper woofer instead), the forwardness of the sound is too much for me as they are.
Hmmm by its very nature a 2.5 way should compensate for baffle step fully, giving the full 6dBs. That is of course if you are using another ER18 for the helper. If the sound is still too forward even with the helper in place then perhaps you need to increase the size of the inductor feeding the 0.5 woofer.
I'm using a CA18RLY as the helper, it has a more solid low end response than the ER18, at the expense of a bigger box. It's actually the character of the sound I mean, rather than the overall balance. But I've just ordered some tweeters for the CA18s, so hope to end up with two good sets of 2-ways... after I get over the shock of finding out how much inductors cost nowdays...
Last edited:
Cool, thanks Gornir. I didn't get around to re-measuring my ER18s last weekend (damn kids...), but I'm off to the Lab at work to weigh some blobs of Blutack...
(I'm changing my mind about the ER18 sound, after more listening I think it's just more 'revealing' than I'm used to, & badly recorded stuff will sound that way...)
(I'm changing my mind about the ER18 sound, after more listening I think it's just more 'revealing' than I'm used to, & badly recorded stuff will sound that way...)
Last edited:
Tell me about it, even if you only use basic, but decent quality, passive xover parts, passive xovers always end up costing more then you'd like😱 Copper prices these days do indeed, not help!
ER18 re-measured
These are the new measurements done with Delta Comp. Sealed Box Vol is 14 L.
Goran, they appear to be similar to your sample #2. I'm getting a VAS of 26.43L.
5th, you're right, Mms = 13.96g.
Thanks for highlighting a possible fault in my initial measurements. I eventually traced the culprit to typo error. Added weight was actually 22g but I enter it as 12g.
Fortunately, even with wrong measurements, it worked out for me in a 14L vented box.
These are the new measurements done with Delta Comp. Sealed Box Vol is 14 L.
Goran, they appear to be similar to your sample #2. I'm getting a VAS of 26.43L.
5th, you're right, Mms = 13.96g.
Thanks for highlighting a possible fault in my initial measurements. I eventually traced the culprit to typo error. Added weight was actually 22g but I enter it as 12g.
Fortunately, even with wrong measurements, it worked out for me in a 14L vented box.
Attachments
Hi Michael, it's nice to see you've solved the issue. Aside from just the numerical error, the impedance plot of the second lot of measurements looks a lot smoother then the first too.
Yes, now it looks as it supposed to do with a smooth impedance curve and all. Seems like a reliable measurement.
Regards
/Göran
5th, Goran
Thanks, my initial measurements have always bugged me. It's comforting to know that my new TS are now closer to Seas.
In my ER18, I went for mid-bass instead of the lowest F3. Sequence of pictures are:
1) Simulation on Goran's 18L box (new TS)
2) Simulation on my 14L box (new TS)
3) Summed Response (PURPLE) of Port (GREEN) and Near Field Response of ER18 (RED). Accuracy up to 500Hz.
4) Gated 1 meter 2.83V Summed Response of Crossover (2,200Hz - RED)
5) Spliced Frequency Response of Bass and Crossover Graphs. Spliced at 500Hz.
6) System Z
7) Crossover Network (2nd order + 5dB BSC for ER18; 3rd Order for 27TDFC)
8) Finished Speakers
Thanks, my initial measurements have always bugged me. It's comforting to know that my new TS are now closer to Seas.
In my ER18, I went for mid-bass instead of the lowest F3. Sequence of pictures are:
1) Simulation on Goran's 18L box (new TS)
2) Simulation on my 14L box (new TS)
3) Summed Response (PURPLE) of Port (GREEN) and Near Field Response of ER18 (RED). Accuracy up to 500Hz.
4) Gated 1 meter 2.83V Summed Response of Crossover (2,200Hz - RED)
5) Spliced Frequency Response of Bass and Crossover Graphs. Spliced at 500Hz.
6) System Z
7) Crossover Network (2nd order + 5dB BSC for ER18; 3rd Order for 27TDFC)
8) Finished Speakers
Attachments
I'm thinking of building the SR71 to be powered off my P101 (high power version) but I'm undecided if I'd use the same box volume as recommended by Zaph. I'm planning on using this without a sub so what do you guys suggest for box volume and tuning? (I'll be keeping the baffle width but can adjust depth and height to maintain the response with the baffle step compensation as designed as I'm getting the Madisound parts kit)
- Status
- Not open for further replies.