Dayton RSS 390 HF4 and NHT 1259 subwoofers. Relative Frequency Response in a Room. Searching for 20 hz deep bass.

[ligs]

Dayton RSS 390 HF4 and NHT 1259 subwoofers. Relative Frequency Response in a Room.

Recently I got a good deal on a pair of Dayton RSS 390 HF4 15” subwoofers. So I built a pair of 4.2 ft3 sealed cabinets made of ¾”  Baltic Birch plywood and stuffed with about 3 pounds of fiberfill in each cabinet. The NHT 1259 subwoofers are housed in 2.8 ft3 sealed cabinets with about 1.8 pounds of fiberfill each. The 12” NHT 1259 is no longer available. The Dayton 15” subwoofer is still current. It is highly regarded by the DIY community and is made with anodized aluminum cone meaning the cone has stiff exterior ceramic “aluminum oxide” surfaces and it also has a modern magnetic structure with triple shortening rings. Efficiency wise, the Dayton is rated at 91.2 db/2.83 vs 90 db/2.83v for NHT 1259.  Driven through a fixed 100 hz low pass (12 mH/200 uf) crossover, both subwoofers had strong response to at least to 31.5hz. Interestingly, the 15 inch Dayton is about 4 db more efficient from 20 hz to 31.5 hz. Both subs provide a smooth satisfying bass foundation to compliment small satellite speakers.

[Aadams]

3 hours ago, ligs said:

So I built a pair of 4.2 ft3 sealed cabinets made of ¾”  Baltic Birch plywood

Did you saw those cabinets?  That is hard core in this day.

[ligs]

There is a family owned Terry lumber yard near where I live. I purchased two 5x5 sheets of Baltic plywood and they cut into more than 38 pieces with great precision for a very reasonable $30. Fitting them together was very straightforward. This 13-ply Baltic is a great material to work with. The inside of the boxes is heavily braced(front to back, left to right and top to bottom). When done, each empty cabinet weighs 50 lbs about the same as an AR3a. 

For my generation(born in 1940's), if you wanted something you built it yourself. I still remember my fun with Eico kits, Knight Kits, Heathkits, and Dyna Kits.

[Aadams]

Your lumber yard is very cooperative.  Did they cut the radius on the hole too? 

Also, how do you cover the gap between your JBL roll off and this woofer if it is limited to around 100hz? 

[ligs]

Yes, we are lucky to have a real lumber yard nearby. At Lowes or Home Depot they would warn you the cuts will not be precise enough for cabinet work:) Yes, they cut the holes with a jig saw. But I spent hours enlarging the holes to fit the subwoofer openings. 

All my satellite speakers including the one using JBL 127H1 woofer will respond to below 100 Hz, so there will be some overlap between them as shown in the graph below. The red trace representing both drivers are in phase acoustically and  is louder than the blue line. It is interesting connecting the subwoofer electrical polarity  opposite to than of the JBL 127H1  resulted in in-phase acoustic response. 

[Aadams]

2 hours ago, ligs said:

It is interesting connecting the subwoofer electrical polarity  opposite to than of the JBL 127H1  resulted in in-phase acoustic response. 

Perhaps the amps are opposite polarity.  It happened to me once.

I was referring to the chart below.  Your JBL starts rolling off at 200Hz or has that changed?

[ligs]

That old chart has measurements taken from earlier version of crossover and the satellite showing rising response from 80 hz to 1000 hz. 

The latest version of the crossover has rendered the JBL 127H1/Dayton RST 28 A4 flat from 80 hz to 1000 hz.

The individual response curves of RSS 390 HF4 and the JBL satellite are shown below. All except a dip around 160 hz(probably due to the floor cancellation as discussed in many AR/ Allison literature), the new satellite speaker now matches the sub in SPL.

[Pete B]

Nice work, very nice!

[ligs]

Thanks, Pete.

Subwoofers are relatively straightforward to construct and can provide the biggest bang for the buck in terms of perceived improvement. 

A dedicated subwoofer amplifier can further enhance the performance of any subwoofer by combining crossover, equalizer and sufficient power all in one package and is available at a very affordable price.

 

[Aadams]

Ligs

If the NHT 3.3 is your model target why are you using a JBL 10" rather than a modern wide range 6"?

Adams

[ligs]

Excellent question!. One  normally would not choose a 10" woofer in a 2-way speaker. But as Carl showed in 2015  you could make a very robust 2-way with the new Advent woofer and a modern high power 28 mm tweeter(Dayton RS 28 H4) with efficiency around 92 db/2.83v. Since then, Dayton came up with two  higher sensitivity updated tweeters(RST 28 H4 and A4) and I came into possession of a pair of JBL 127H1 10-inch woofers which are similar in sensitivity as the new Advent woofer. DIYers seldom use JBL drivers in speaker projects. But JBL drivers are typically low in distortion with high in power handling. The particular 127H1 has extremely low distortion due to sophisticated magnetic and venting features(on par with Scanspeak).  When I compare my JBL 127H1/RST 28A4 with the more traditional 6.5-inch 2 way (either JBL S36 or Infinity R162) I am surprised that it sounds just as detailed as the smaller counterparts  and yet it can play much louder and stay clean. I am pleasantly impressed by how a good quality tweeter contributes to the definition and realism of music. 

One additional advantage is the midbass is more solid(or someone may describe as punchy) with a good 10"  woofer than a smaller one. So for some music it gives a better representation of the scale.

 

[Aadams]

On 2/22/2019 at 1:34 PM, ligs said:

When I compare my JBL 127H1/RST 28A4 with the more traditional 6.5-inch 2 way (either JBL S36 or Infinity R162) I am surprised that it sounds just as detailed as the smaller counterparts  and yet it can play much louder and stay clean.

I am not surprised. Based on my experiences with small "full range" two ways, they get overwhelmed in a hurry when used in singles.

Why the concern with efficiency?  92db isn't all that significant compared to 89 and a 10" crossed high can be beamy unless you are relaxing in the sweet spot or perhaps listening in the way- back, far field.

Adams

[ligs]

To determine the effect of beaming is to divide 13500/ the diameter of a cone in inch = frequency in hz.

The cone part of JBL 127H1 is 8 inch in diameter. The beaming becomes a problem when the operating frequency is greater than 13500/8= 1688 hz. In my satellite the crossover between the 10 inch(nominally) JBL and 1.1 inch(28 mm) RST 28A4 tweeter is around 1500 hz. This puts a strong demand on the tweeter, but this Dayton unit seems to handle it just fine. When I walk around this speaker the sound character does not change that much. The tweeter probably is the main reason that this particular design works.  JBL 8340A, a professional speaker using a similar 127 H3 woofer has a crossover of 2200 hz.

 http://www.jblproservice.com/pdf/Theatre Series/8340A.pdf

 

Now the question of why 92 db.

You said “Based on my experiences with small "full range" two ways, they get overwhelmed in a hurry when used in singles” If one wants minimize distortion and maximize SPL. One can run many small drivers or run with a larger one. Here, everything being equal, larger speaker is inherently more efficient and can take more power due to the larger voice coil, and dissipating heat better. Agreed,  92 db vs 90 db is not a deal breaker. But compared to hundreds of speakers with a sensitivity around 85-87 db/2.83 v, 92 db/ 2.83 v looks very nice.  A 6 db improvement in speaker sensitivity would make a 100 watts/channel amplifier sounds like an amplifier with 400 watts/channel.

[Aadams]

19 hours ago, ligs said:

The cone part of JBL 127H1 is 8 inch in diameter. The beaming becomes a problem when the operating frequency is greater than 13500/8= 1688 hz. In my satellite the crossover between the 10 inch(nominally) JBL and 1.1 inch(28 mm) RST 28A4 tweeter is around 1500 hz. This puts a strong demand on the tweeter, but this Dayton unit seems to handle it just fine. When I walk around this speaker the sound character does not change that much. The tweeter probably is the main reason that this particular design works.  JBL 8340A, a professional speaker using a similar 127 H3 woofer has a crossover of 2200 hz.

I have been thinking about this.  You have created a high efficiency AR14.   I made a quick check of other  2 way 10s. The LIGS14  and the AR14 seem to be the lowest crossover of any 2way 10" ever shown in public. 

 

[ligs]

It is very interesting that you compared it to AR 14.

According to Steve F

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/816-how-good-are-ar14-speakers/

 “The AR 14 crossed over to the 1" dome tweeter at 1300Hz, a remarkably low crossover, considering the tweeter’s 1050Hz resonance. Ordinarily, one could expect either high distortion at the bottom of the tweeter’s operating range or limited power handling, but I never recall the 14 suffering from these problems, so apparently the crossover was well designed. The 1300Hz crossover point allowed the speaker’s energy response to be reasonably uniform, since a woofer of that diameter won’t become severely directional until about 2000Hz.”

The modern Dayton RST A4 tweeter is slightly larger than the Peerless tweeter used in AR14 and has an even lower  Fs of 603 Hz with a usable range from 1200 hz and up. I used an even steeper 3-rd order high pass crossover around 1500 hz. The low pass crossover for JBL 127H1 is also  third order electrically as well, plus a LCR trap to make it smoother around 1000 hz. 

 

 One particular feature which I may claim to be different from AR 14 is the separate mounting of the tweeter (outside of the woofer box) allowing some adjustment of the frequency blending between the woofer and tweeter by varying the vertical distance between the tweeter and the woofer. Some people call it time (or phase) alignment but the change in the tonality with respect to the vertical alignment is quite noticeable. B&W has been a proponent of mounting the tweeter in a pod outside the woofer cabinet.

[Aadams]

On 2/24/2019 at 3:06 PM, ligs said:

If one wants minimize distortion and maximize SPL. One can run many small drivers or run with a larger one

Agree but I don't care about max spl except as the by-product of 12-15db of dynamic range, which in my limited experience 6 inch and smaller home 2 ways cannot handle without audible distortion. 

On 2/24/2019 at 3:06 PM, ligs said:

But compared to hundreds of speakers with a sensitivity around 85-87 db/2.83 v, 92 db/ 2.83 v looks very nice.  A 6 db improvement in speaker sensitivity would make a 100 watts/channel amplifier sounds like an amplifier with 400 watts/channel.

An alternative is to wire 8 ohm speakers in parallel and you can turn a 100 watt amp into 200 or even 400 watt amp, possibly for one brief glorious moment. 

On 2/25/2019 at 1:42 PM, ligs said:

adjustment of the frequency blending between the woofer and tweeter by varying the vertical distance between the tweeter and the woofer.

Are you referring to up and down or front to back.  Y axis or Z axis?

[ligs]

"An alternative is to wire 8 ohm speakers in parallel and you can turn a 100 watt amp into 200 or even 400 watt amp, possibly for one brief glorious moment."

Actually people tried that before. Stacking(or doubling) Advent or  AR speakers in each channel generally  produces better sound than using  one speaker for each channel. I wonder  if increased voltage sensitivity is somewhat responsible for this. However, one has to use caution regarding the life span of the tweeter(read the story below) and/or the ability of amplifier to handle the low impedance. 

"Are you referring to up and down or front to back.  Y axis or Z axis?"

Front to back(Y axis).  The voice coil of the woofer usually is further behind the mounting frame  than the tweeter. So at the same frequency the tweeter arrives to our ears sooner than the woofer.  The famous Dahlquist DQ10 places all upper drivers behind the woofer as seen in this picture.  B&W also has some high end models placing the tweeters outside and behind the woofers boxes. 

 

[Aadams]

Here you are Ligs,  from Floyd Toole at Harman 22 years ago.  It is still fact.

[ligs]

Thanks for the quote from Dr. Toole!

Many of us have struggled with placing the speakers in the room to get the optimal bass without making male voices too thick or heavy. Invariably, you get one thing right by sacrificing the other. So subwoofer can indeed easily solve this dilemma.

Another thing worth noting is there seems to have a lot more deep bass on youtube and HT media than typically experienced in FM and CD listening. This can put a lot of stress on the typical fullrange and even multi-way speakers and it also demands more amplifier power.  

[ligs]

To complete the comparison of bass performance of subwoofers, I thought it would be interesting to include the New Advent Loudspeaker(NAL) because it is known for the potent bass performance but, it never claimed to be a subwoofer. Surprise, surprise, it compares very well with NHT 1259. At a fairly loud 80 db at 3ft distance, it may not be easy to tell apart from NHT 1259. Since both NHT 1259 and RSS390 HF4 are much larger and have more linear displacement due to longer p-p, I  expect the difference would be more noticeable at higher spl. Of course, the larger subwoofers are rated for higher power too so you can play them

much louder than the Advents. But overall, at moderate spl, the bass of this classic 40-year old Advent still performs very well in my room. I wish I kept AR3a and AR1 for even more comparison.

Legend: NAL blue, RSS390 HF4 red, NHT 1259 green. The latter two were driven through a 100hz low pass crossover, NAL was driven directly to one channel of an amplifier. 

 

 

[Aadams]

Was the Advent in and Advent cabinet?

 

[ligs]

Yes. The original metal frame woofers were re-foamed using surrounds purchased from looneytune2001 on ebay. The interior is packed with foam blocks. During measurement, I turned the NAL tweeter switch to "extended" position. As I recall from the crossover schematics, at this position the woofer would by-pass the inductor and thus driven directly by the amplifier. 

 

[Aadams]

20 hours ago, ligs said:

still performs very well in my room

I had a pair of good working but rough looking OLAs I sold  before I started experimenting with subwoofers.  I have always thought old Advents would be good candidates for this application because 1. they can do it and 2. They are still cheap,  if you can avoid shipping charges.

But overall, at moderate spl, the bass of this classic 40-year old Advent still performs very well in my room. I wish I kept AR3a and AR1 for even more comparison. 

What is "moderate spl"   Vast majority of music program material rarely goes below 42hz where the Advent is strong.  Different issue if you like movie effects.

 

 

 

[ligs]

3 hours ago, Aadams said:

I had a pair of good working but rough looking OLAs I sold  before I started experimenting with subwoofers.  I have always thought old Advents would be good candidates for this application because 1. they can do it and 2. They are still cheap,  if you can avoid shipping charges.

But overall, at moderate spl, the bass of this classic 40-year old Advent still performs very well in my room. I wish I kept AR3a and AR1 for even more comparison. 

What is "moderate spl"   Vast majority of music program material rarely goes below 42hz where the Advent is strong.  Different issue if you like movie effects.

 

 

 

Just out curiosity, I measured the sound level (Realistic Sound Level Meter, C weighing) in my listening room. When each speaker was producing about 80db at 1 meter in front of the meter, at my listening position it was 75 db from both stereo speakers. It was definitely already louder than you could carry a conversation.  Since NAL is rated at 87 db/w at 1 meter, 80 db would not even need one watt in power:) 

 

I also did a quick calculation of the displacement capability of NAL vs other subwoofers. The maximum spl in the the bass is usually limited by the volume the woofer can displace (cone area x coil moving capability)

I am using the following data:

NAL. 7.5” cone diameter and 6.4mm voice coil overhang

AR3a 8.5” and 6.4mm

NHT 1259 9.5” and 13 mm

RSS390 11.5” and 14 mm

 

On the back of envelop calculation for cone displacement factor (imagine the cc displacement of a car engine) and assuming NAL is one then AR 3a is 1.3, NHT 1259 is 3.5 and RSS390 is 5.2. Thus the larger subwoofers can provide more potential for spl and perhaps less distortion.

 

I tend to agree with you that for music listening Advent and AR are perfectly satisfactory. What a subwoofer will help is the special HT effect and the louder SPL in the deep bass if you need it.  In most HT situation, people prefer to set the subwoofer at a higher spl (often up to 6 db) than the main speakers. Doing so with conventional full range speaker will tend to overload the woofer easily.

[Aadams]

17 minutes ago, ligs said:

When each speaker was producing about 80db at 1 meter in front of the meter, at my listening position it was 75 db from both stereo speakers.

Harman does their blind testing at 78db at listening position.