Pure Audio Project Quintet 15

Bob0398 · « **on:** 16 Dec 2021, 02:22 am »

Pure audio project quintet 15 speakers biamped using the PAP C1 crossover designed and built by Nelson Pass for PAP. Room spl below about 60hz say I need to boost the lower frequencies by a bunch. How do I choose what sub or subs to get? I'd appreciate any advice I can get to help me make a decision. Thank you.

richidoo · « **Reply #1 on:** 16 Dec 2021, 03:05 am »

You have enough woofer, you don't need more subs.
As you know, dipole has steeper rolloff than box speakers due to the cancellation, and this must be compensated to have similar bass extension as box speakers. Even with 8 15" woofers, in dipole they can't make low bass without EQ. Many AC members use dipole bass and have huge deep bass with only a pair of 12" drivers with servo amps. With quad 15" per side you will have that much more headroom and low freq extension due to the larger cone area, but you need to correct the system Q electronically (with EQ,) and luckily...

...the PAP C1 crossover blurb says it has "adjustable low bass boost" to compensate for the dipole bass rolloff, which is exactly what you need. Pass knows about big woofers in dipole so it will work as long as you have enough amp, and if the woofer motors can handle the power.
Sounds like it's all intended to work together in this setup. You won't need subs.

Bob0398 · « **Reply #2 on:** 16 Dec 2021, 02:44 pm »

Richidoo, thank you for your post. how do I get more bass? The system is biamped with Rowland Model 501s on the bottom so I presume there is enough juice. The crossover is set at the recommended 355hz approximately. I will take a picture later of the settings in the crossover and post it later.

richidoo · « **Reply #3 on:** 16 Dec 2021, 05:30 pm »

Quote from: Bob0398 on 16 Dec 2021, 02:44 pm

how do I get more bass?

Follow the directions in this picture. Or contact mfg. Or ask for help with a new thread in Enclosures Circle.

I recommend you use some kind of acoustic measurement (like OmniMic, $300) to make the C1 adjustment fast and easy. Play the test sweep signal through the speakers, run the program on your PC and adjust the C1 filters while you watch the frequency response change with your adjustments live on screen.

Adjust woofer and horn crossover frequencies separately so they are -6dB at your desired XO freq, then check for flat response when playing together. Dial in bass boost and treble EQ the same way. You can also do it with free tools if you understand the process.

Start a thread in Enclosures Circle if you need help adjusting the C1. There might also be a thread about C1 on diyaudio.com where Nelson Pass haunts. Good luck!

Bob0398 · « **Reply #4 on:** 16 Dec 2021, 05:46 pm »

I've set out spl measures with REW in my room. Also my settings in crossover box. Exterior pots set to about 5 o'clock. Suggestions?

richidoo · « **Reply #5 on:** 16 Dec 2021, 07:54 pm »

I'm happy to help you but I'm not sure exactly what you're looking for. Please be specific about what problems you're still having and what steps in the instructions you have already taken. Feel free to volunteer as much additional information as you're willing to type.

Bob0398 · « **Reply #6 on:** 16 Dec 2021, 08:52 pm »

When I see the REW graph of spl in my room , shown attached, I feel that I'm shortchanging myself on both the top and bottom ends of the frequency spectrum and I don't know how to change up the crossover, my only tool, to get a flatter graph. I'm looking for help to change the crossover settings to get more bass and more upper range sound. I feel it should be

possible given the quality of the speakers and electronics. This seems to be a view that's shared.

richidoo · « **Reply #7 on:** 16 Dec 2021, 10:07 pm »

If your low pass and high pass filters are both adjusted accurately to 355Hz then you need to increase the bass boost adjustment, and also increase the high pass level adjustment to flatten the overall response.

I would check the crossovers and levels are accurately adjusted first:
Move the microphone to be 2 feet away from the mouth (outer rim) of the horn, on axis. Measure woofers and horn of one speaker from this same mic location. This short distance will allow measuring the acoustic response of the drivers/crossovers without room response and echo messing it up.

Turn woofer amps on and tweeter amps off. Use REW to measure frequency response of the woofers only. Adjust the "low pass cross point adjustment" screw and the bass boost EQ (aka peak adjustment) until you have kinda flattish response curve, with the top end of the woofer response rolling off thru -6dB (below the flat part of the curve) at 355Hz, and the curve staying kinda flattish down to <50Hz. Take note of the SPL level of the flat part of the response curve on this REW woofer graph. You can fine tune the bass boost to your taste later. This is just to get you in the ball park. Move the mic to the other speaker and adjust those woofers same way.

After woofers are adjusted, shut off the woofer amps and turn on the tweeter horn amps. Mic is in same place, 2 feet away from horn, on axis. Use REW to measure FR of the tweeter/horn by itself with no woofer. Adjust the highpass filter cross point adjustment screw and the high pass filter level adjustment screw and high freq notch filter until the the tweeter response curve is flattish and rolls off to -6dB at 355Hz, and the flat part of the curve is about the same SPL level that you noted in the previous woofer adjustments. Repeat other side tweeter horn.

Turn woofer amps back on. Sweep the FRs of both whole speakers, mic still at 2 feet on horn axes. They should look mostly flattish the whole way with odd bumps OK. It won't be perfect, just get ballpark flattish. Make any fine adjustments to improve the measurement.

After you have it working flat you can start adjusting to taste. But let your brain adjust to flat before you make any changes. This might take a week or longer. Let your mind heal from any subconscious EQ you have been applying in your head, and lose any listening habits you have adopted to deal with the previous poor response.

After you have adjusted your mind to the flat EQ I would start fine tuning by reducing the high pass level screws by 1-3dB. Flat response on most older style horns is rarely an enjoyable musical experience. The horizontal aiming will have an efect on this adjustment too. Coordinate the speaker toe angle with the high pass level adjustment.
The horn cross point and notch filter adjustments can be adjusted slightly with the high pass level to create a gradually downward sloping FR from crossover freq to the top end according to your taste.

Play some dance or rock music with very hard hitting bass and adjust the bass boost EQ to suit your taste. Then play a classical symphony like Beethoven 5th 3rd movement by Vanska/Minnesota on a streamer. This has nice bass violin soli. Adjust the bass again, noting the changes from the dance music. Somewhere in between those settings is correct depending on what music you like, etc.

Advanced: Look at the phase angle response of the whole speaker with REW measurement (mic at 2 feet) and adjust the high pass cross point VERY slightly up or down to possibly flatten the phase response curve. This will make the woofer and tweeter sing in unison throughout the the XO band which will improve clarity in that range, upper bass / low mids.

Once everything is adjusted with mic at 2 feet, then you can scan the room to see what else you need to do with acoustic treatment and speaker positioning, etc. But you have to get the speakers working correctly on their own before you look at room.
Hope this helps, good luck

Cappy · « **Reply #8 on:** 16 Dec 2021, 11:38 pm »

Quote from: Bob0398 on 16 Dec 2021, 02:22 am

Room spl below about 60hz say I need to boost the lower frequencies by a bunch. How do I choose what sub or subs to get? I'd appreciate any advice I can get to help me make a decision. Thank you.

Greetings Bob. Welcome to Audiocircle.

Subwoofers with Quintet15 speakers can easily destroy the open baffle bass magic of the eight (!!!) 15" woofers.

I have Quintet15 Horn1 speakers with the Leonidas serial 1st order passive crossover. I use Audiolense software for room and speaker correction.

Until recently, I had been crossing a sealed Rythmik F12G subwoofer at 35 hz with a steep digital crossover. That sounded terrific. A higher crossover definitely wrecks the magic. But now I've found that even with the low 35hz crossover, the system sounds better without a sub, and with a higher DSP bass boost instead.

Rich is the man here -- he can help you get your Quintets with active crossover as flat as possible, with best phase response. After that I suggest considering use of Audiolense or Acourate software to improve things further for your digital chain.

Here is a recent Audiolense frequency response graph of my right channel, in 1db increments, at listening position:

Bob0398 · « **Reply #9 on:** 17 Dec 2021, 01:17 am »

Richidoo, your response was just what I was looking for. It'll be so helpful. Thank you so very much. I'll report back.

Bob0398 · « **Reply #10 on:** 17 Dec 2021, 01:19 am »

Cappy, yours is just the kind of response I'm hoping to get. Wish me luck

Bob0398 · « **Reply #11 on:** 17 Dec 2021, 05:39 pm »

Right speaker. Red is woofers only from 24inches to mic; blue is both woofers and full range Voxativ 1.6. from 24 inches to mic.

Cappy · « **Reply #12 on:** 17 Dec 2021, 05:45 pm »

Bob - got a screen shot program? That picture makes me whoozy...

OneNote has one if you have that.

Bob0398 · « **Reply #13 on:** 17 Dec 2021, 06:20 pm »

Easier to see?

Cappy · « **Reply #14 on:** 17 Dec 2021, 06:42 pm »

Yes, thanks.

This might be set correctly, but worth a check:

1) Is the volume jumper on the PAP C1 crossover set to control the Voxativ volume?

2) Can you increase the volume on the C1 crossover left and right pots to raise the level of the Voxativ driver?

That won't fix your bass issues but could make >400 hz flatter, particularly around 6khz, which has a pretty big dip. But it is a try and see thing. If you end up using DSP, I would say it would probably make sense to increase the Voxativ level a bit. Then if you use DSP to knock down the various peaks you could be looking pretty good, maybe even in the bass.

Also, how far are the Quintet15s from your front wall?

Also, it seems like with Rich's help on fine tuning the PAP C1, you could perhaps reduce the dip at 500hz.

Bob0398 · « **Reply #15 on:** 17 Dec 2021, 07:10 pm »

Speakers are about 7.5 feet from front wall. Crossover volume level? I don't know. Do you mean high level pass levels? They are linked to Voxativ.

Bob0398 · « **Reply #16 on:** 17 Dec 2021, 07:15 pm »

This is one speaker, Voxative only and this the curve with mic at two feet. What do I adjust to get this flatter?

Cappy · « **Reply #17 on:** 17 Dec 2021, 07:28 pm »

<< Speakers are about 7.5 feet from front wall. >>

Nice. That is going to give spectacular imaging when you get things dialed in.

Your big distance to back wall also lets you tune the bass by moving the speakers between, say 5' and 7.5'. You might be able to minimize issues caused by room nodes. And you might be able to improve low bass response. Have you played around with speaker positioning yet to optimize bass peaks and dips?

<<Do you mean high level pass levels? >>

Yup, the high pass signal that is going to the Voxativs.

<<This is one speaker, Voxative only and this the curve with mic at two feet. What do I adjust to get this flatter?>>

I am browsing the First Watt B5 crossover manual (which I believe is similar to the PAP C1) I see in addition to bass boost capability, there is a frequency eq filter for the high passed full range driver. This might help, not sure without looking into it more.

I have not seen a Voxativ 1.6 frequency curve before, but full range drivers are typically not very flat, with a choppy treble response. DSP can help.

Cappy · « **Reply #18 on:** 17 Dec 2021, 08:26 pm »

Looking at the B5 manual in more detail, it looks like the high pass frequency EQ attenuates higher frequencies of the full range driver.

So if this feature is available in the PAP C1, check to see if it is set incorrectly. Is it?

richidoo · « **Reply #19 on:** 17 Dec 2021, 08:39 pm »

The bass EQ is a boost, the treble EQ is a notch.

The bass boost need more and the notch needs less.

It looks from your measurements that high and low pass filters both crossover around 220Hz. Which is good if you want it that low. You said you wanted 355Hz XO before.

I thought the speaker had horn loaded compression driver. Speaker on their webpage has horn loaded compression driver. But you're talking about Voxative. They make full range dynamic drivers? Please post a picture of your speaker so I can see what we're working on here...

A high pass filter for full range driver like voxativ would tend to be lower freq like 200-350Hz while a horn tweeter which is typically crossed around 1kHz, not 350.

Overall it's looking much better. Great job! Still more to do.

EDIT: Now I read the website it has several different options. You have the voxative. OK I got it!