Seeking input on ScanSpeak 3-way

karha096

Member
2013-02-05 10:26 pm
A few years back I bought a set of drivers and the time has come to make something out of them. I have started to model the crossovers and wanted to hear if you think I might be on the right track.

Elements:

Enclosure-wise, I am thinking that a 60 liter bass reflex box for the woofers and a closed enclosure for the midrange, something similar to Troels Gravesens Ekta Grande might be reasonable as a first trial box.

This is just an early sketch, so it is based on traced SPL and impedance curves from Scan Speak. Break-in and TS-measurements are under way. The crossover is modelled without a box and assuming all drivers are mounted with aligned acoustic centers.

I have attempted to integrate a baffle step around 500Hz and I have tried to keep the impedance above 3 Ohms.

What are your thoughts on this - on the right track here?

Another question, do you think it will be possible to drive mid+tweeter with a tube amp with this kind of impedance?
 

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mtidge

Member
2018-12-12 12:22 pm
A few years back I bought a set of drivers and the time has come to make something out of them. I have started to model the crossovers and wanted to hear if you think I might be on the right track.

Elements:

Enclosure-wise, I am thinking that a 60 liter bass reflex box for the woofers and a closed enclosure for the midrange, something similar to Troels Gravesens Ekta Grande might be reasonable as a first trial box.

This is just an early sketch, so it is based on traced SPL and impedance curves from Scan Speak. Break-in and TS-measurements are under way. The crossover is modelled without a box and assuming all drivers are mounted with aligned acoustic centers.

I have attempted to integrate a baffle step around 500Hz and I have tried to keep the impedance above 3 Ohms.

What are your thoughts on this - on the right track here?

Another question, do you think it will be possible to drive mid+tweeter with a tube amp with this kind of impedance?
What are you crossover points? From your simulation it looks the band-pass for the mid range is too small. If you put the low pass and high pass to close they will interfere with each other. Rule of thumb is the high pass should be 8 times to 10 times higher than the low pass. The classic 300hzHZ to 3Khz is a good starting point. If you are going active you might be able to ignore this, not sure. Not only does the filter work better, but it pushed the XO out of the telephone band.
 

karha096

Member
2013-02-05 10:26 pm
500/2500 would be my recommendation for xover points. Make sure you damp the 800/900 Hz resonance on the mid.
Good input, the current design filters at around 850. I will lower this to something at or below 500 Hz.
Regarding the resonance around 800-900, I was thinking maybe I would wait to see how they meausure before I implement a notch. I was kind of hoping to adress it along in the high-pass section.
 
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Interesting thread, I will be following as this is very similar to my upcoming build:
Scanspeak R3004/6020-10
Scanspeak 15M4531
2x Scanspeak 15W8531

Mine will be MTWW. Sealed, active, and compact. Only 60cm high with no stand (hence midrange above tweeter). I was thinking of crossover points of 250, and 2500, though Wolf's comments may change my mind. Anyway it will be minidsp active, so very flexible in terms of tuning.
 
Here's my reasoning...

When Pete built his Byzantiums (A squat, half-boat-shaped 3-way with the RSS315HF-8, the 15W4531 and venerable (NLA) RS28A), he found that even though the wider baffle would typically lend well to a lower xover due to the baffle-step, that it just sounded wrong. He found the best 'weight' to the mids was HP at 500Hz. Higher thinned them out, and lower had no benefit, especially with regards to xmax usage on the midrange. All that have heard the 15W variants know that they do mids very well, and getting the vocal range majority will benefit here. The 7" I don't feel does them as well. However, both are wider bandwidth drivers and can help each other. It is also easier to get good blending in xovers with the mid xoverd in this range, no matter the drivers used in such a design.

Just my opinion, but I think dual 15W8531 per side would leave me wanting more for woofers. (If you're doing a sub to augment it, then why go 3-way.)

The R tweeter will like 2.5kHz as well, as ring-tweeters tend to have rising HD as they play lower. You may have to comp the Fs with shallow slopes or it might buzz a bit. I would also advise to NOT use 8th order slopes with these drivers. They are still relatively SOTA, and have broad bandwidth. Blending with shallower slopes will likely sound very very good.
 
Hi Wolf
Thanks for the thorough explanation.
I remember the Byzantiums. Great build. Inspirational.
I am aiming for a very compact three-way. I have used the 15W4531 before in a two-way, so I have an idea what to expect. As you will surely know, there are many many documented two-way builds with the 5.5" Scanspeak Revelators. Most report an astonishingly full-range result (given their size). My thinking is that using two of the drivers for bass duty (sealed), and having the ability to boost them with minidsp EQ would give me a good improvement on the two way designs (Zaph's ZD5, Troel's Ellam, Carmody's Carrera, etc). If I went with a sub, I would have to cross below 150Hz or have the driver on the baffle, which I cannot accommodate for size restrictions.
I hope that I am not crashing this thread. The 15M4531 will be the make or break of the OP's build (and mine), I think. It is a surprising seldom used driver (in documented builds).
 
Musings:
Skip the mid, or put it at the back to maintain vibrational symmetry for the woofers, and arrange the woofers a la d'Appolito.

You could probably bring the impedance way up by running the woofers @ 16 ohm, and change the tweeter pad. Your tube amp will thank you for the lower current. And tune the bass alignment so the resonance provides useful EQ rather than unwanted bloat.
 
Hi Wolf
Thanks for the thorough explanation.
I remember the Byzantiums. Great build. Inspirational.
I am aiming for a very compact three-way. I have used the 15W4531 before in a two-way, so I have an idea what to expect. As you will surely know, there are many many documented two-way builds with the 5.5" Scanspeak Revelators. Most report an astonishingly full-range result (given their size). My thinking is that using two of the drivers for bass duty (sealed), and having the ability to boost them with minidsp EQ would give me a good improvement on the two way designs (Zaph's ZD5, Troel's Ellam, Carmody's Carrera, etc). If I went with a sub, I would have to cross below 150Hz or have the driver on the baffle, which I cannot accommodate for size restrictions.
I hope that I am not crashing this thread. The 15M4531 will be the make or break of the OP's build (and mine), I think. It is a surprising seldom used driver (in documented builds).
(Wolf's Scandivifias....) <------ Yeah, you forgot that one in your list.

The 15M is not that old of a driver, so it's understandable why it's not more prevalent.

I don't understand why you wouldn't use the 8530K00 and vent them for best extension without needing the boost at all. The group delay will be the same with a vented box as the boosted-sealed box if the drivers and transfer functions are the same. To top it off, the vented box will be likely more efficient, and protect the drivers better around resonance/Fb. If you already have them, then my query has no significance.